FIELD

The invention relates to medium & low temperature pyrolysis for coal, more especially, to a medium & low temperature pyrolysis system for coal, as well as a process for producing upgraded coal, pyrolysis gas with high calorific value, and tar or liquefied synthetic oil from raw coal by using the same.

BACKGROUND

The coal chemical composition is very complex; however it could be summarized by division of organic and inorganic substances, in which the major components are organic. The organic substances in coal mainly consist of five elements compounds including C, H, O, N, and S etc, wherein C, H, and O account for over 95 weight % of the above organic substances in coal. In addition, coal also contains a minor quantity of P and thimbleful other elements. Inorganic substances in coal includes moisture and different minerals, their existence lowers the quality and utilization value of coal. Most inorganic substances in coal are harmful components. Coal and steam could have water gas shift reaction under specific temperature and pressure, so as to form water gas product, i.e. syngas or pyrolysis gas and tar. Generally, coal pyrolysis gas has following composition: CO: about 45%; CO2: about 17-20 %; H2: about 34-39%; CH ₄ : about 0.1-4%. Tar is a liquid product derived from coal pyrolysis process, and can be classified into high temperature tar and medium & low temperature tar. The medium & low temperature tar is one of important sources for synthetic petroleum oil, and could be used to manufacture liquefied synthetic oil products including gasoline, diesel oil etc via hydrogenating processes etc. .

The fact that there is a great variance among ages and geological configurations of coal formation causes a great gap among qualities, compositions and properties with respect to coals from various geological locations. For many years, the process for converting low rank coal into higher grade coal in economical and /or efficient manner, or process for reasonable utilization of coal while retainment or recovery of coal useful components in coal has been developed or studied.

US 2008/0134666A1 disclosed a system and method for using unmixed fuel processor. This process used three reactors, wherein in the first reactor, coal was preliminarily gasified into pyrolysis gas including H2, CO, and CO2. After steam was inputted into the first reactor, steam, coal and CO in the pyrolysis gas reacted with each other forming H2 and CO2. C0 ₂ is then absorbed by the carbon sorbent material and removed from the product stream. C02rich carbon sorbent material is then introduced into the second reactor. As a result, the gas product discharged from the first reactor is mainly hydrogen rich gas. In the third reactor, the reduced oxygen transfer materials that are metal / metal oxides, for example FeO, and inputted hot air occurred oxidization reaction which is strong exothermic. Oxygenated oxygen transfer materials were then fed into the second reactor from the third reactor, and oxygen depleted hot air in the third reactor became nitrogen rich gas. This high temperature inert hot gas was discharged from the third reactor for further electricity generation. On the other hand, the used CO2 sorbent materials entering the second reactor from the first reactor is calcinated under effect of massive heat inputted from the oxygenated oxygen transfer materials entering the second reactor so as to release carbon dioxide. Meanwhile unreacted carbon, CO and H ₂ from the first reactor are oxidized by oxygen transfer materials which are metal oxides. As a result, oxygenated oxygen transfer material are reduced to non- oxygenated oxygen transfer material after releasing oxygen, and entered the third reactor again for next circulation of oxidization reaction. In this way, the gas product discharged from the second reactor is mainly CO2 rich gas. Via CO2 sorbent materials regeneration in the second reactor and entry of the first reactor; as well as oxygen transfer materials deoxidization in the second reactor and entry of the third reactor, the circulation and utilization by regeneration of CO2 sorbent materials and oxygen transfer materials has been achieved, on the other hand, hydrogen rich gas, carbon dioxide rich gas and nitrogen rich gas are discharged from the first, second and third reactors, respectively.

The above-mentioned system and method has following benefits: the effective separation between oxygen and other components else including nitrogen in air is realized in the third reactor so as to produce pure hydrogen rich gas, carbon dioxide rich gas and nitrogen rich gas. Because of high temperature of the above nitrogen rich gas, it could be used for heat utilization, for example electricity generation etc, or reacts with hydrogen discharged from the first reactor and /or carbon dioxide discharged from the second reactor so as to produce industrial products including ammonia or urea, in this way, not only is heat energy in coal effectively utilized, for instance, to generate electricity, but also the useful components in coal could be retained or recovered so as to produce industrial products including ammonia or urea or hydrogen with high calorific value.

On the other hand, the above - identified system and method has following defects: firstly, the system has three reactors communicated with each other, the cost of their manufacture, operation and maintenance is extremely high; secondly, the operation temperature of the above three reactors all approaches or is over lOOCfC, particularly, the operation temperature of the third reactor even reaches 1200~1550°C, under such high temperature, small particles of oxygen transfer material or char gradually become big particles through melting merging by the effect of surface tension, such big particles would plug the delivery line when being fed into another reactor from one reactor so as to increase risk for operation difficult or even accident; thirdly, in the above system, the coal gasification is divided by two stages, coal is preliminarily gasified in the first reactor, a certain quantity of produced char is entirely gasified in the second reactor. As a result, the complexity of the system is indeed increased, and the security of the system operation is consequently dropped down.

US6911057 and US6669917 also disclosed an apparatus and method that is very similar to that disclosed in the above US2008/0134666A1. Based on the almost same technical principle as in the US2008/0134666A1, the above apparatus and method disclosed in US6911057 and US6669917 also inevitably possess the above-mentioned defects that are very difficult to overcome.

US6667022 disclosed a method and apparatus for separating gas mixture containing synthetic gas (syngas) into separate streams of hydrogen rich gas and carbon dioxide rich gas respectively. Wherein in first reactor of fluidization bed type, carbon dioxide sorbent materials, for example CaO or dolomite, absorbed CO2 in syngas, meanwhile CO in the synthetic gas and steam further reacts with each other so as to form CO2 and H2, residue of CO was oxidized into CO2 by Fe203, at the same time, Fe203 was deoxidized into FeO. The used sorbent materials which became carbonate after sorption of CO2, and FeO touch high temperature steam carrying oxygen in the second reactor of fluidization bed type so as for the used sorbents to be pyrolyzed for releasing CO2 so that the used CO2 sorbent material re -became fresh and regenerated CO2 sorbent material again, and FeO was oxidized into Fe203 by oxygen, the regenerated CO2 sorbent materials and Fe203 were then circulated back to the above first reactor f of fluidization bed type for utilization by circulation.

Though the method and apparatus described in US6667022 also relates to the sorption of carbon dioxide and application of oxygen transfer materials, they are intended to be mainly applied on separation between various components in synthetic gas, does not relate to pyrolysis (including high temperature and medium & low temperature pyrolysis) or gasification of coal. Moreover, the second reactor of fluidization bed type in the above apparatus also has operation temperature of up to 1200 ^° C.

The above mentioned patent documents are incorporated hereby in entirety by reference.

SUMMARY OF INVENTION

The object of the present invention aims to overcome the above identified defects appearing in the process of coal conversion and utilization, and to provide with a system for utilizing coal in the effective and economic manner while retaining or recovering of the useful components in coal, more specifically, the present invention relates to a coal medium & low temperature pyrolysis system, as well as a process for producing upgraded coal, pyrolysis gas with high calorific value, and tar or liquefied synthetic oil from raw coal by using the same. The process according to the invention not only improves the heat energy efficiency of coal, but also retains or recovers the useful components in coal.

According to one aspect of the present invention, provided herein is a medium & low temperature pyrolysis (is abbreviated as LTCP) system for coal, comprising:

a medium & low temperature pyrolyzer for coal having a raw coal inlet, steam inlet, upgraded coal outlet, and pyrolysis gas output line, and at least one medium & low temperature pyrolysis zone within the pyrolyzer between the raw coal inlet and the upgraded coal outlet, wherein said raw coal inputted reacts with oxygenated oxygen transfer material in the medium & low temperature pyrolysis zone so as to be pyrolyzed at medium & low temperature, while a gaseous admixture of pyrolysis gas including methane, carbon oxide, carbon dioxide and hydrogen, and tar pyrolyzed at medium & low temperature or synthetic oil is produced; and at least one oxygen transfer material regenerator communicating with said medium & low temperature pyrolyzer via a line for a spent oxygen transfer material delivery and another line for regenerated oxygen transfer material delivery, wherein the spent oxygen transfer material produced in the pyrolyzer via the line for the spent oxygen transfer material delivery enters into the oxygen transfer material regenerator, and is regenerated therein through oxidization reaction with gas containing oxygen inputted into said regenerator, then regenerated oxygen transfer material recycles back into the medium & low temperature pyrolyzer via the another line for regenerated oxygen transfer material delivery, and oxygen depleted or lost gas by oxidization reaction is discharged out of said regenerator from its outlet; and a condenser communicating with said medium & low temperature pyrolyzer for coal via said pyrolysis gas output line, wherein said gaseous tar pyrolyzed at medium & low temperature or gaseous synthetic oil becomes tar or liquefied synthetic oil through condensation, and is separated from said pyrolysis gas.

In the above embodiment, preferably, the medium & low temperature pyrolysis zone comprises a fluidizing bed of particles of the coal and the oxygen transfer material, the fluidizing bed could comprise a perforated baffle at the bottom with at least one downcomer installed on it, with the upper end of the downcomer above the perforated baffle and the lower end of the downcomer below the perforated baffle, the upper end of the downcomer (107) could be a opening, and be covered by a mesh (108), with the following relationship among size of particles of the coal and oxygen transfer material, and hole of the mesh 108: smallest particle size of C wt of the coal > size of the hole of the mesh (108) > biggest particle size of A wt of the oxygen transfer material, wherein C wt and A wt are independently over 75 wt , preferably, C wt and A wt are independently over 85wt , more preferably, C wt and A wt are independently 100wt . wherein said opening could be an upward flare opening; said raw coal could be mixture of raw coal and catalyst for coal direct liquefaction.

In the above embodiment, more preferably, said oxygen transfer material could be carried into pores of porous ceramic particles tolerable to high temperature; and said upper end of the downcomer could be a opening, and be covered by a mesh, hole diameter of said mesh is equal to biggest diameter of said porous ceramic particles tolerable to high temperature so that said porous ceramic particles goes through said mesh (108) and enters inside of the downcomer, preferably, said opening is an upward flare opening.

In the above embodiment, also preferably, the medium & low temperature pyrolysis zone comprises a fluidizing bed of particles of the coal and the oxygen transfer material, the fluidizing bed comprises a perforated baffle at the bottom and at least two vertical baffles, one vertical baffle having upper end of at least one side cut above the perforated baffle and another vertical baffle having lower end of at least one side cut nearby the perforated baffle, wherein he upper end of the at least one side cut of the vertical baffle is covered by a mesh (108), with following relationship among size of particles of the coal and oxygen transfer material, and hole of the mesh 108:

Smallest particle size of C wt of the coal > size of the holes of the mesh (108) > biggest particle size of A wt of the oxygen transfer material, wherein C wt and A wt are independently over 75 wt , preferably, C wt and A wt are independently over 85 wt , more preferably, C wt and A wt are independently 100 wt .

In the above embodiment, more preferably, said oxygen transfer material could be carried into pores of porous ceramic particles tolerable to high temperature, wherein said upper end of the at least one side cut of the vertical baffle could be a opening, and be covered by a mesh, hole diameter of said mesh is equal to biggest diameter of said porous ceramic particles tolerable to high temperature so that said porous ceramic particles goes through said mesh and enters inside of gap or tunnel between the vertical baffle and internal wall of pyrolyzer.

In the above embodiment, particularly preferably, more than one said medium & low temperature pyrolysis zone could be present in the pyrolyzer, said oxygen transfer material could be iron oxide, wherein said iron oxide could be FeO or Fe ₂ 03.

In the above embodiment, most preferably, at least one heat exchanger could be installed in the medium & low temperature pyrolyzer and /or the oxygen transfer material regenerator to transfer heat generated in the system away out of the pyrolyzer and /or the oxygen transfer material regenerator; at least one cyclone, cyclone cascade, membrane and /or filter could be installed in the pyrolyzer and /or the oxygen transfer material regenerator to separate solid particles from gas; oxygen lost or depleted gas containing oxygen by oxidization reaction in said oxygen transfer material regenerator could be used to heat said medium & low temperature pyrolyzer (100) or the steam needed by said medium & low temperature pyrolyzer (100) via heat exchanger, and one layer or multi-layers of carbon dioxide sorbent could be arranged in said condenser so as to absorb or capture carbon dioxide therein for raising calorific value of said pyrolysis gas; the raw coal could be dehydrated, and loses medium & low temperature volatiles in said medium & low temperature pyrolysis zone so as to be converted into upgraded coal with improved calorific value; sulfur component in the raw coal reacts with oxygen transfer material in said medium & low temperature pyrolysis zone so as to form catalyst needed by liquefaction reaction where coal or tar is hydrogenated, wherein, said catalyst is preferably iron sulfide.

In the above embodiment, more particularly preferably, said upgraded coal outlet is located in area nearby said perforated baffle which biases to the upgraded coal outlet so as to facilitate to discharge the upgraded coal out of said medium & low temperature pyrolyzer; said perforated baffle could have another outlet of said upgraded coal so as to discharge said upgraded coal below said medium & low temperature pyrolysis zone; the raw coal fed into said medium & low temperature pyrolyzer could have particles diameter ranging from 500 microns to 100 mm; said oxygen transfer material regenerator could comprise a raiser which lifts spent oxygen transfer material to upper portion of said regenerator.

According to another aspect of the present invention, provided herein is a process for producing upgraded coal, pyrolysis gas with high calorific value, and tar or liquefied synthetic oil from raw coal by using the aforesaid medium & low temperature pyrolysis system for coal, comprising following steps in turn: raw coal, or admixture of raw coal and catalyst for direct liquefaction reaction for coal and oxygen transfer material are fed into said medium & low temperature pyrolyzer into which steam is inputted, meanwhile the medium & low temperature pyrolysis zone in said medium & low temperature pyrolyzer is kept into the range of temperature from 250°C-750°C for medium & low temperature pyrolysis; components pyrolyzed at the medium & low temperature in the raw coal react with the oxygen transfer material in the medium & low temperature pyrolysis zone so as to form pyrolysis gas containing carbon monoxide, carbon dioxide, hydrogen, and methane, as well as gaseous tar pyrolyzed at medium & low temperature or gaseous synthetic oil, and the raw coal is dehydrated and lose medium & low temperature volatiles so as to becomes upgraded coal with high calorific value via medium & low temperature pyrolysis, wherein sulfur component in the raw coal reacts with said oxygen transfer material so as to form catalyst needed by liquefaction reaction where the coal or tar is hydrogenated; the produced upgraded coal is discharged from its outlet , and a mixture of the pyrolysis gas and said gaseous tar pyrolyzed at medium & low temperature or gaseous synthetic oil is discharged from said pyrolysis gas output line; spent oxygen transfer material is fed into the oxygen transfer material regenerator from said medium & low temperature pyrolyzer via the line for the spent oxygen transfer material delivery; said spent oxygen transfer material reacts by oxidization with gas containing oxygen inputted into said regenerator so as to be regenerated in said regenerator; the regenerated oxygen transfer material is fed into said medium & low temperature pyrolyzer from said regenerator via line for regenerated oxygen transfer material delivery so as to be circulated by utilization; the outputted mixture of the pyrolysis gas and said gaseous tar pyrolyzed at medium & low temperature or gaseous synthetic oil passes through the condenser so as for said gaseous tar pyrolyzed at medium & low temperature or gaseous synthetic oil to become tar or liquefied synthetic oil via condensation and to be separated from the pyrolysis gas.

In the above embodiment, preferably, said gas containing oxygen is air; and said outputted pyrolysis gas is separated from carbon dioxide by sorption of CO2 sorbent so as to enhance calorific value of said pyrolysis gas, and to realize capture of CO2.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic illustration showing the principle of operation of the medium & low temperature pyrolysis system according to the present invention, wherein some components are optional.

Fig. 2A shows a preferable mechanism structure of separation between coal and oxygen transfer material in said medium & low temperature pyrolyzer.

Fig. 2B shows another preferable mechanism structure of separation between coal and oxygen transfer material in said medium & low temperature pyrolyzer.

Fig. 3 is an amplified view showing porous ceramic particles tolerable to high temperature, on which the oxygen transfer material is carried.

Fig. 4 is another schematic illustration showing the principle of operation of the medium & low temperature pyrolysis system according to the present invention, wherein the vitiated air discharged from said regenerator is separated gas from solid particle.

SPECIFIC MODE FOR IMPLEMENTING THE INVENTION

Reference is made to drawings below for further explanation and description of the present invention, so as for skilled worker in the art to clearly understand the sprit and principle of the present invention. However, such below description is just exemplary, is not meant to limit the scope of the present invention in any manner.

As a general and exemplary embodiment of the medium & low temperature pyrolysis system according to the present invention, shown in Fig. 1, such system includes a medium & low temperature pyrolyzer or pyrolyzer (100) for coal and an oxygen transfer oxygen material regenerator (200) communicating with said medium & low temperature pyrolyzer (100) via a line (103) for a spent oxygen transfer material delivery and another line (104) for regenerated oxygen transfer material delivery, said pyrolyzer or pyrolyzer (100) for coal has steam inlet (102) at lower portion, preferably at bottom, pyrolysis gas output line (111) at upper portion, preferably at top, raw coal inlet (101) at middle portion or upper portion, and upgraded coal outlet (109) at lower portion or at bottom. The oxygen transfer oxygen material regenerator (200) has hot air inlet (201) at bottom.

Raw coal with specific particle diameter, which is fed into the above medium & low temperature pyrolyzer (100) at middle portion or upper portion, takes place physical or chemical reaction in the presence of steam, so as to be pyrolyzed at medium & low temperature so that char or upgraded coal and coal pyrolysis gas are produced, the said coal pyrolysis gas mainly contains CO, CO2, H2, vapor, and minor quantity of sulfide gas; the main component of char or upgraded coal is C.

The refreshed or regenerated oxygen transfer material which is fed into the above medium & low temperature pyrolyzer (100) from the above oxygen transfer material regenerator (200) via line (104) for regenerated oxygen transfer material delivery occurs following reactions:

OTM-oxidized + C <= > CO + OTM-reduced (1)

CO + OTM- oxidized <= > CO2 + OTM-reduced (2)

H2 + OTM-oxidized <= > H2O + OTM-reduced (3)

At the same time, in said medium & low temperature pyrolyzer (100), the raw coal takes place the following water-gas shift reaction:

CHO.8 (coal) + H2O <= > CO + 1.4H2 (4)

CO + H2O <= > CO2 + H2 (5)

CO + 3H2 <= > CH4 + H2O (6)

2CO + 2H2 <= > CH4 + CO2 (7)

Sulfide contained in the raw coal becomes sulfide gas which mainly is H2S by coal pyrolysis at medium & low temperature, then occurs following reaction:

H2S + OTM-oxidized <= > H2O + SO2 + OTM-reduced or (8)

H2S + OTM-oxidized <= > H2O + OTM-reduced S (9)

In this way, the raw coal fed into the medium & low temperature pyrolyzer (100) is converted into char or upgraded coal and coal pyrolysis gas is generated, meanwhile the fresh oxygenated oxygen transfer material is deoxidized into oxygen lost or depleted spent oxygen transfer material which is then fed into the above oxygen transfer material regenerator (200) via line (103) for spent oxygen transfer material delivery and is regenerated by occurrence of following chemical reaction:

OTM-reduced + O2 <= > OTM-oxidized (10)

The regenerated and oxygenated oxygen transfer material is circulated into said medium & low temperature pyrolyzer (100) via line (104) for regenerated oxygen transfer material delivery, and will be deoxidized again therein for realization of next circulation.

The char or upgraded coal generated in said pyrolyzer (100) is discharged out of the above said pyrolyzer (100) from the upgraded coal outlet (109) at lower portion or bottom of the above said pyrolyzer (100). The coal pyrolysis gas produced in said pyrolyzer (100) is discharged out of above said pyrolyzer (100) from pyrolysis gas output line (111) at upper portion, preferably at top of the above said pyrolyzer (100), and such pyrolysis gas contains gaseous tar or synthetic oil which has not been separated from pyrolysis gas by condensation.

The operation temperature in said pyrolyzer (100) could generally be ranged from 250°C to 750°C, preferably from 300°C to 700°C, more preferably from 350°C to 650°C, particularly preferably from 400°C to 600°C, most preferably from 450°C to 550°C; the operation pressure in said pyrolyzer (100) could be generally ranged from atmosphere to 60 bar, preferably from 20-60 bar, more preferably from 25-55bar, particularly preferably from 30-50bar, most preferably from 35-45bar, for example 40bar.

Steam, preferably pressurized steam, is generally inputted into the above pyrolyzer (100) at bottom of pyrolyzer (100) by pressurized nozzles so as to promote or accelerate the water-gas shift reaction therein. The temperature and usage quantity of the above steam are not herein specially limited, provided that they could ensure the temperature within pyrolyzer (100) to reach the desired operation temperature, and the water-gas shift reaction therein could be on the rails, for instance, the steam temperature could be 200-750°C, or is equal to or similar to the operation temperature within said pyrolyzer (100).

The operation temperature in said oxygen transfer material regenerator (200) could generally be ranged from 550°C to 1000°C, preferably from 550°C to 900°C, more preferably from 450°C to 850°C, particularly preferably from 500°C to 800°C, most preferably from 550°C to 750°C, for example 600°C or 700°C; the operation pressure in said oxygen transfer material regenerator (200) could be generally ranged from atmosphere to 60 bar, preferably from 20-60 bar, more preferably from 25-55bar, particularly preferably from 30-50bar, most preferably from 35-45bar, for example 40bar.

The oxygen released or depleted spent oxygen transfer material entering the bottom of the above regenerator (200) is raised to upper portion of said regenerator (200) through a raiser (202) via transportation by hot air blown into the above regenerator (200) at bottom. During the process of upward movement, the above spent oxygen transfer material massively exothermically reacts by oxidization with oxygen contained in hot air so as to be oxidized into oxygenated refreshed or regenerated oxygen transfer material, which is then circulated into said pyrolyzer (100) via line (104) for regenerated oxygen transfer material delivery, on the other hand, the oxygen lost or depleted vitiated air is discharged out of said regenerator (200) from its outlet at upper portion, or at top of said regenerator (200).

The temperature and usage quantity of the above hot air is not herein specially limited, provided that they could ensure temperature into said regenerator (200) to reach the desired operation temperature, and oxidization reaction therein could smoothly take place and continue to proceed. The above hot air is poured into the bottom of said regenerator (200) preferably by pressurized nozzles.

The above mentioned oxygen transfer material generally is metal oxides, preferably iron oxides, particularly preferably FeO, Fe ₂ 03 and /or Fe ₃ 04, and most preferably FeO.

In the cast that the above mentioned oxygen transfer material is FeO, in the above pyrolyzer (100), FeO and H ₂ S contained in said pyrolysis gas will occur following reaction: FeO + H2S <= > H2O + FeS ( 9' )

As above described, tar derived from medium & low temperature pyrolysis is one of important sources of synthetic petroleum oil, and could be used to manufacture liquefied synthetic oil products including gasoline, diesel oil etc via hydrogenating reaction under high pressure.

The above FeS indeed is the excellent catalyst for coal direct liquefaction reaction and tar hydrogenated reaction, under the catalysis of FeS, tar derived from medium & low temperature pyrolysis and hydrogen contained in pyrolysis gas will occur following reaction, under high pressure of 20-60 bar within said pyrolyzer (100):

CxHy (tar or coal) + H2 <= > CH2 (synthetic oil) ( 11 )

Wherein above y/x is about 0.8.

Through the above hydrogenating reaction, gaseous tar contained in pyrolysis gas is converted into synthetic petroleum oil. If amount of FeS produced from the above reaction (9') is not sufficient to support the continuation of proceeding or completion of the above hydrogenating liquefaction reaction, some catalyst for the above hydrogenating liquefaction reaction, for example FeS, could be mixed into the above raw coal fed into the above pyrolyzer (100) in the specific proportion so as to drive the above hydrogenating liquefaction reaction to approach completion.

The coal pyrolysis gas discharged from the above medium & low temperature pyrolyzer (100) is separated out of tar or liquefied synthetic oil by tar recovery apparatus generally including condenser, so as to be converted into pure coal pyrolysis gas which contains H2, CH4, CO and CO2. The above coal pyrolysis gas passes through filter containing CO2 sorbent so as to be converted into more pure coal pyrolysis gas mainly including H2, CH4, and CO, which is thereby an excellent gaseous fuel with very high calorific value due to absence of impurities by filtrating out CO2.

The raw coal is dehydrated and loses medium & low temperature volatiles in said pyrolyzer (100) via pyrolysis at medium & low temperature so as to be converted into char or upgraded coal with greatly improved calorific value.

The above tar or liquefied synthetic oil separated from the coal pyrolysis gas by condensation is very good chemical raw material or liquid fuel.

In this way, general raw coal, especially poor quality raw coal, is converted into upgraded coal, coal pyrolysis gas with high calorific value and tar or liquefied synthetic oil by using the medium & low temperature pyrolysis system according to the present invention, which of utilization value and calorific efficiency is remarkably enhanced.

In the case that the above oxygen transfer material is iron oxide, maybe there are various forms of the above oxygen transfer material, the reason is that, in the medium & low temperature pyrolyzer (100) and the regenerator (200), the above iron oxide generally as the oxygen transfer material could occur following reaction.

Under deoxidization atmosphere within said pyrolyzer (100), iron oxide would take place following deoxidization reaction:

CxHy (coal)+ FeO => CO2 + H2O+ Fe ( 12) or

CxHy (coal)+ FeiOs => CO2 + H2O+ FeO ( 13 )

On the other hand, under oxidization atmosphere within said regenerator (200), Fe would take place following oxidization reaction:

Fe + 02 => FeO ( 14)

The all above oxidization reactions are massively exothermic, which would generate a lot of heat which could keep the operation temperature of the above regenerator (200) into the range of

400 ^° C-1000 ^° C. The above oxidization reactions have different reaction temperatures, however within the above range of 400 ^° C-1000 ^° C , Fe is mainly oxidized into Fe2C"3.

Generally, the gas discharged from the above medium & low temperature pyrolyzer (100) may contain tiny solid particles or dust, preferably, such vitiated gas goes through separator for gas-solid or gas -liquid, for example cyclone shown in Fig. 1, cyclone cascade, membranes, and /or filter, so as to realize separation between gas and solid, separated tiny solid particles or dust could be subjected to general water quenching treatment.

The temperature of medium & low temperature pyrolyzed gas after gas-solid separation generally ranges from 250 ^° C to 750 ^° C . Preferably, one or more heat exchangers could be applied to it, for instance coils and multi-tubular heat exchanger with water or air passing there through, so as for the above gas temperature to lower into the temperature range which is suitable for separation of tar or hydrogenated liquefied synthetic oil by condensation, identification of the above temperature is obvious for the skilled worker in the art, or could be available from regarding references or documents in the prior art, or is found out from operation handbook or product specification of special equipments.

Preferably, cooled medium & low temperature pyrolyzed gas after gas-solid separation passes through tar or synthetic oil recovery apparatus typically containing condenser (300) shown in Fig. 1 so as to be separated into pure coal pyrolysis gas and tar or hydrogenated liquefied synthetic oil.

More preferably, in the above heat exchanger (115), as shown in Fig. 1, air pressurized by compressor (301) is applied as heat exchanging medium for the above heat exchanger (115), the pressured air heated by the above heat exchanger could be used as a source of hot air needed by the above oxygen transfer material regenerator (200), and is directly sprayed into the bottom of the above regenerator (200) by pressurized nozzles.

The temperature of oxygen lost or depleted vitiated air discharged from its outlet (203) at top of the above regenerator (200) could reach 550 ^° C-1000 ^° C . Also preferably, as shown in Fig. 1, such highly pressured and high temperature air could be fed into an expander (302) so as to drive steam boiler (305) or steam turbine for generating electricity, the generated steam could be used as a source of steam needed by the medium & low temperature pyrolyzer (100), and is directly sprayed into the bottom of the above pyrolyzer (100) by pressurized nozzles.

In fact, at least one medium & low temperature pyrolysis zone (105) is present in the above medium & low temperature pyrolyzer (100), which could have structure of fixed bed or fluidizing bed, however, preferably structure of fluidizing bed, in this medium & low temperature pyrolysis zone (105) where not only is the raw coal pyrolyzed at medium & low temperature, but also the water-gas shift reaction takes place, the raw coal is fully mixed with oxygen transfer material while steam under high pressure and high temperature is prayed into the medium & low temperature pyrolysis zone (105) at bottom so as to form admixture of raw coal, oxygen transfer material and steam.

The admixture of the upgraded coal or char and spent oxygen transfer material could be separated by using some specific separation mechanisms, the separated upgraded coal or char is discharged out of said pyrolyzer (100), so as to be converted into solid product after cooling; meanwhile the separated spent oxygen transfer material enters its regenerator (200) via line (103) for spent oxygen transfer material delivery for regeneration.

The above mentioned separation mechanisms are herein not specially limited, however, above preferable separation mechanisms are those shown in Fig. 2A and 2B.

Fig. 2A shows a preferred embodiment of the separation mechanisms for upgraded coal or char and spent oxygen transfer material in the medium & low temperature pyrolysis zone (105) shown in Fig. 1 in which the medium & low temperature pyrolysis zone (105) includes a fluidization bed, such as spout bed, enclosed by perforated baffles (106) at bottom or similar mechanism such as bubble-cap tray or float valve tray with one or more vertical upwards -flare- opening downcomer(s) (107). The upwards -flare- opening of downcomer (107) is covered by a mesh (108).

In the above case, the particles size of coal or char and spent oxygen transfer material and the size of hole of the mesh 108 have relationship as following:

The smallest particle size of C wt of the coal or char > Size of the holes of the mesh (108) > the biggest particle size of A wt of the spent oxygen transfer material

Wherein, C wt and A wt can be independently more than 60 wt , preferably over 75 wt , more preferably over 85 wt , particularly preferably over 95 wt , most preferably 100 wt . The above-identified size of particles of the coal or char and spent oxygen transfer material as well as the hole of the mesh (108) is referred to their diameters.

As shown Fig. 2A, the fresh and /or regenerated oxygen transfer material goes down through a downcomer (107) or a hollow conduit and enters area nearby the perforated baffles (106), so as to drop in the lower portion of the fluidizing bed, then is upwardly fluidized by the fluidizing bed, and rapidly reacts with the raw coal and steam therein. During upward floating movement by fluidization, refreshed and /or regenerated oxygen transfer material is oxidized so as to complete reaction and becomes spent oxygen transfer material due to completion of reaction. As the spent oxygen transfer material accesses or approaches to upwards -flare- opening of downcomer (107), it has to pass through the mesh (108) covering the upwards-flare-opening by effect of fluidization, the mesh (108) allows small particles of spent oxygen transfer material pass through, but retains larger particles of coal or char in the medium & low temperature pyrolysis zone (105). The spent oxygen transfer material particles passing through the mesh (108) go down through downcomer (107) and enters into volume beneath of the medium & low temperature pyrolysis zone (105). Finally, the spent oxygen transfer material exits the medium & low temperature pyrolyzer (100) via line (103) for spent oxygen transfer material delivery, and is fed in the oxygen transfer material regenerator (200) for regeneration.

It must be noted that the mesh (108) shown in Fig. 2A is optional. It could be deleted from the system according to the present invention. In that case, a minute quantity of coal or char particles or coal dust would be brought into spent oxygen transfer material particles, and then enters into the oxygen transfer material regenerator (200) together with spent oxygen transfer material particles, and combusts with the inputted hot air so as to be converted into CO2 gas etc, thereby to be separated from the fresh or regenerated oxygen transfer material.

In said medium & low temperature pyrolysis zone (105), the coal may collide with oxygen transfer material as being pyrolyzed, therefore the distribution of particles size of raw coal or char in the above medium & low temperature pyrolysis zone (105) may be quite different from that of raw coal just entering said medium & low temperature pyrolyzer (100), that means the distribution of particles size of raw coal or char in the above medium & low temperature pyrolysis zone (105) may be much wider than that of raw coal just entering said medium & low temperature pyrolyzer (100). Therefore, even if the mesh (108) covering the upwards-flare-opening of the downcomer (107) is present, a small portion of coal or char small or tiny particles or coal dust is brought into the above spent oxygen transfer material particles. Such portion of coal or char small or tiny particles or coal dust would be combusted out after entering the oxygen transfer material regenerator (200) together with spent oxygen transfer material. If spent oxygen transfer material mainly is Fe, the spent oxygen transfer material could be separated from the above coal or char small or tiny particles or coal dust by using magnetic separation prior to entering the oxygen transfer material regenerator (200).

The mesh (108) should be tolerable to high temperature of about 900°C, for example about 750°C, and should possess enough strength and deformation resistance at above high temperature. A lot of material could be used to manufacture the above mesh (108), for instance, high temperature resistant alloy, based on Fe, Co and/or Ni, or porous high temperature resistant ceramic film, based on SiC and/or S13N4 could be used to manufacture the above mesh (108).

Under the effect of fluidizing bed, the coal or char and oxygen transfer material particles are fluidized and floating above the perforated baffles (106). However, because of the fact that the size of spent oxygen transfer material particles is much smaller than that of coal or char particles, the weight of the spent oxygen transfer material particles is also much less than that of coal or char particle, thereby the fluidizing or floating height of the spent oxygen transfer material particles, relative to the perforated baffles (106), is much higher than that of the coal or char particles, and thus makes the spent oxygen transfer material particles easily access or approach the above upwards-flare-opening of the downcomer (107), and such spent oxygen transfer material particles are also easily captured by the upwards-flare-opening of the downcomer (107). As a result, the separation between the coal or char particles and spent oxygen transfer material particles is realized in this way.

In the medium & low temperature pyrolysis zone (105), position of the top opening of overflow conduits (upwards -flare- opening of downcomer (107)) relative to the perforated baffle (106), which determines the height of the fluidized bed, is designed to control the rate of overflow of the spent oxygen transfer material to a desired value so as to control the reaction saturation of the oxygen transfer material in the medium & low temperature pyrolysis zone (105), and thus to control the relative amount of the oxygen transfer material inside the medium & low temperature pyrolysis zone (105) in said medium & low temperature pyrolyzer (100).

The raw coal is pyrolyzed and /or pyrolyzed at medium & low temperature in the medium & low temperature pyrolysis zone (105) so as to be converted into char or semi-char which is charged into a specific volume beneath of the perforated baffles (106) after separation from spent oxygen transfer material via common mechanisms well known by skilled worker in the art, for example an char or upgraded coal outlet (not shown) preset within the perforated baffles (106), and is then discharged out of the above pyrolyzer (100) from the above specific volume via another char or upgrade coal outlet (109) at lower portion or bottom of said pyrolyzer (100).

Before the process of medium & low temperature pyrolysis for coal according to the present invention is carried out by using the system as shown in Fig. 1 with the medium & low temperature pyrolysis zone (105) as shown in Fig. 2A, the raw coal is loaded in the medium & low temperature pyrolysis zone (105) from the raw coal inlet (101). Upon starting of the operation, steam under high pressure and high temperature goes through the perforations in the perforated baffle (106) and enters into the fluidizing bed, and rapidly causes the said pyrolyzer (100) fall into its operation pressure and operation temperature. At the same time, the oxygen transfer material particles enter fluidizing bed and are fluidized together with the coal particles. During upward floating movement of the coal and oxygen transfer material particles by fluidization, the coal is pyrolyzed so as to be dehydrated and lose medium & low temperature pyrolyzed volatiles to be converted into char or semi-char while oxygen transfer material is deoxidized by C, CO, and /or H2 therein to release O so as to be converted into spent oxygen transfer material. If the relationship among the size of char or coal and spent oxygen transfer material particles as well as the hole of the mesh (108) is as defined above, theoretically, the mesh (108) allows only the spent oxygen transfer material particles to pass through while the coal or char particles are retained. Fluidized spent oxygen transfer material particles overflow into the downcomer (107) through the mesh (108) and drop down to the zone beneath the medium & low temperature pyrolysis zone (105), then leaves the above pyrolyzer (100) eventually via line (103) for spent oxygen transfer material delivery.

In a preferred embodiment according to the present invention, the oxygen transfer material particles have a size ranging from 1 to 1000 microns, and the raw coal particles have a size ranging from 500 microns to 100 mm. The temperature and pressure within the above pyrolyzer (100) lie in any range suitable for medium & low temperature pyrolysis for coal, such as 200°C ~900°C, particularly 250°C -750°C; 1 atm to 100 bar, particularly 20-60 bar.

Fig. 2B shows another preferred embodiment of the separation mechanisms for upgraded coal or char and spent oxygen transfer material in the medium & low temperature pyrolysis zone (105) shown in Fig. 1. This embodiment is the same as that shown in Fig. 2A, with the exception that two vertical baffles (107') each with end of one or more side cut(s) are used instead of vertical upwards-flare-opening downcomer(s) (107) (overflow conduits). It is apparent to those skilled in the art that the principle for the operation of this medium & low temperature pyrolysis zone (105) is the same as that shown in Fig. 2A.

As shown in Fig. 2B, there is a gap or tunnel between the internal vertical wall of the above pyrolyzer (100) and two vertical baffles (107'). The fresh or regenerated oxygen transfer material goes down through the gap or tunnel between the internal vertical wall of the above pyrolyzer (100) and one vertical baffles (107') with lower end of at least one side cut, and enters into area near by perforated baffle (106) via the lower side cut, thereby drops into the lower portion of said fluidizing bed. Then it is upwardly fluidized by said fluidizing bed, and rapidly is deoxidized by C, CO, and /or H2 therein to release O so as to be converted into the spent oxygen transfer material. During upwardly floating movement by fluidization, the fresh or regenerated oxygen transfer material completes deoxidization reaction and becomes spent oxygen transfer material. As spent oxygen transfer material approaches o accesses to upper end having at least one side cut of another vertical baffle (10V), it has to pass through a mesh (108) covering the said upper end with side cut by effect of fluidization, the mesh (108) allows small particles of spent oxygen transfer material pass through, but retains larger particles of coal or char in said medium & low temperature pyrolysis zone (105). The spent oxygen transfer material particles passing through mesh (108) go down through the gap or tunnel between the internal vertical wall of said pyrolyzer (100) and one vertical baffles (10V) with upper end of at least one side cut, and enters into volume beneath of the perforated baffle (106). Finally, the spent oxygen transfer material exits said pyrolyzer (100) via line (103) for spent oxygen transfer material delivery, and is fed in the oxygen transfer material regenerator (200) for regeneration.

In the above case, there is following relationship among the particles size of coal or char and spent oxygen transfer material and the hole size of mesh (108):

The smallest particle size of C wt of the coal or char > Size of the holes of the mesh (108) > the biggest particle size of A wt of the spent oxygen transfer material

Wherein, C wt and A wt can be independently more than 60 wt , preferably over 75 wt , more preferably over 85 wt , particularly preferably over 95 wt , most preferably 100 wt . The above-identified size of particles of the coal or char and spent oxygen transfer material as well as the hole of the mesh (108) is referred to their diameters.

It must be noted that the mesh (108) shown in Fig. 2A is optional. It could be deleted from the system according to the present invention. In that case, a minute quantity of coal or char particles or coal dust would be brought into spent oxygen transfer material particles, and then enters into the oxygen transfer material regenerator (200) together with spent oxygen transfer material particles, and combusts with the inputted hot air so as to be converted into CO2 gas etc, thereby to be separated from the fresh or regenerated oxygen transfer material.

In said medium & low temperature pyrolysis zone (105), the coal may collide with oxygen transfer material as being pyrolyzed, therefore the distribution of particles size of raw coal or char in the above medium & low temperature pyrolysis zone (105) may be quite different from that of raw coal just entering said medium & low temperature pyrolyzer (100), that means the distribution of particles size of raw coal or char in the above medium & low temperature pyrolysis zone (105) may be much wider than that of raw coal just entering said medium & low temperature pyrolyzer (100). Therefore, even if the mesh (108) covering the said top end having at least one side cut of the vertical baffle (107') is present, a small portion of coal or char small or tiny particles or coal dust is brought into the above spent oxygen transfer material particles. Such portion of coal or char small or tiny particles or coal dust would be combusted out after entering the oxygen transfer material regenerator (200) together with spent oxygen transfer material. If the spent oxygen transfer material mainly is Fe, the spent oxygen transfer material could be separated from the above coal or char small or tiny particles or coal dust by using magnetic separation prior to entering the oxygen transfer material regenerator (200).

The mesh (108) should be tolerable to high temperature of about 900, °C for example about 750°C, and should possess enough strength and deformation resistance at above high temperature. A lot of material could be used to manufacture the above mesh (108), for instance, high temperature resistant alloy, based on Fe, Co and/or Ni, or porous high temperature resistant ceramic film, based on SiC and/or S13N4 could be used to manufacture the above mesh 108.

Under the effect of fluidizing bed, the coal or char and oxygen transfer material particles are fluidized and floating above the perforated baffles (106). However, because of the fact that the size of spent oxygen transfer material particles is much smaller than that of coal or char particles, the weight of the spent oxygen transfer material particles is also much less than that of coal or char particle, thereby the fluidizing or floating height of the spent oxygen transfer material particles, relative to the perforated baffles (106), is much higher than that of the coal or char particles, and thus makes the spent oxygen transfer material particles access or approach the above top end having at least one side cut of the vertical baffle (10V), and such spent oxygen transfer material particles are easily captured by the above top end having at least one side cut of the vertical baffle (10V). As a result, the separation between the coal or char particles and spent oxygen transfer material particles is realized in this way.

In the medium & low temperature pyrolysis zone (105), position of the top end having at least one side cut of the vertical baffle (107') relative to the perforated baffle (106), which determines the height of the fluidized bed, is designed to control the rate of overflow of the spent oxygen transfer material to a desired value so as to control the reaction saturation of the oxygen transfer material in the medium & low temperature pyrolysis zone (105), and thus to control the relative amount of the oxygen transfer material inside the medium & low temperature pyrolysis zone (105) in said medium & low temperature pyrolyzer (100).

The raw coal is pyrolyzed and /or pyrolyzed at medium & low temperature in the medium & low temperature pyrolysis zone (105) so as to be converted into char or semi-char which is charged into a specific volume beneath of the perforated baffles (106) after separation from spent oxygen transfer material via common mechanisms well known by skilled worker in the art, for example an char or upgraded coal outlet (not shown) preset within the perforated baffles (106), and is then discharged out of the above pyrolyzer (100) from the above specific volume via another char or upgrade coal outlet (109) at lower portion or bottom of said pyrolyzer (100).

Before the process of medium & low temperature pyrolysis for coal according to the present invention is carried out by using the system as shown in Fig. 1 with the medium & low temperature pyrolysis zone (105) as shown in Fig. 2B, the raw coal is loaded in the medium & low temperature pyrolysis zone (105) from the raw coal inlet (101). Upon starting of the operation, steam under high pressure and high temperature goes through the perforations in the perforated baffle (106) and enters into the fluidizing bed, and rapidly causes the said pyrolyzer (100) fall into its operation pressure and operation temperature. At the same time, the oxygen transfer material particles enter fluidizing bed and are fluidized together with the coal particles. During upward floating movement of the coal and oxygen transfer material particles by fluidization, the coal is pyrolyzed so as to be dehydrated and lose medium & low temperature pyrolyzed volatiles to be converted into char or semi-char, while oxygen transfer material is deoxidized by C, CO, and /or H2 therein to release O so as to be converted into spent oxygen transfer material. If the relationship among the size of char or coal and spent oxygen transfer material particles as well as the hole of the mesh (108) is as defined above, theoretically, the mesh (108) allows only the spent oxygen transfer material particles to pass through while the coal or char particles are retained. Fluidized spent oxygen transfer material particles overflow into the gap or tunnel between the internal vertical wall of the above pyrolyzer (100) and the above vertical baffles (107') through the mesh (108) and drop down to the zone beneath the medium & low temperature pyrolysis zone (105), then leaves the above pyrolyzer (100) eventually via line (103) for spent oxygen transfer material delivery. In a preferred embodiment according to the present invention, the oxygen transfer material particles have a size ranging from 1 to 1000 microns, and the raw coal particles have a size ranging from 500 microns to 100 mm. The temperature and pressure within the above pyrolyzer (100) lie in any range suitable for medium & low temperature pyrolysis for coal, such as 200°C ~900°C, particularly 250°C -750°C; 1 atm to 100 bar, particularly 20-60 bar.

The physical separation between the raw coal or char and oxygen transfer material could also be realized by selection of another manner. That means that the oxygen transfer material could be carried into the internal pores of porous ceramic material particles tolerable to high temperature, and such internal pores are communicated outside. The separation between the raw coal or char and oxygen transfer material could be realized by the separation between the porous ceramic material particles tolerable to high temperature and raw coal or char. As well known by those skilled in the art, the specific gravity of raw coal and char generally ranges from 1.0-1.8, on the other hand, the specific gravity of metal oxide as the oxygen transfer material is much higher than the above value, for instance, various iron oxide and Fe have the specific gravity ranging from 3.5-5.0. Furthermore, majority of ceramic materials tolerable to high temperature, for example SiC and S13N4, also has the specific gravity of over 3.0. Therefore the bulk specific gravity of porous ceramic material particles tolerable to high temperature, which of internal pores are filled by the above oxygen transfer material, is much higher that of the raw coal or char. In the case that the above inert porous ceramic material particles tolerable to high temperature carrying the oxygen transfer material, is fluidized or mixed with the raw coal or char particles in the above medium & low temperature pyrolysis zone (105), under the operation circumstance of said pyrolyzer (100), the oxygen transfer material present in the internal pores of the above mentioned ceramic particles is also deoxidized by C, CO, and /or H2 nearby to release O so as to be converted into the spent oxygen transfer material, the porous ceramic material particles tolerable to high temperature carrying the spent deoxidized oxygen transfer material enter the oxygen transfer material regenerator (200) via line 103 for the spent oxygen transfer material delivery, where the spent oxygen transfer material present in the above internal pores is also oxidized by oxygen contained in the hot air fed into the said regenerator (200) so as to be converted into refreshed or regenerated oxygen transfer material. From this it is clear that deoxidization reaction in said pyrolyzer (100) or oxidization reaction for in the oxygen transfer material regenerator (200) for the oxygen transfer material carries out in the internal pores of the porous ceramic material particles tolerable to high temperature.

The above porous ceramic material tolerable to high temperature and being able to carry the oxygen transfer material could be various deoxidizing and oxidizing atmosphere resistant inert ceramic material tolerable to high temperature, however preferably is SiC and S13N4 ceramics etc, Fig. 3 is the amplified view showing the porous ceramic material particles tolerable to high temperature, on which the oxygen transfer material is carried, Pores communicating with each other are present on surface and inside of the above ceramic particles so as to facilitate carrying the oxygen transfer material. The ceramic particles shown in Fig. 3 has round shape which is a preferable form, however other shapes, for example oval, cubic or irregular particles shape etc, could also be adopted for such ceramic particles.

The above porous ceramic material particles tolerable to high temperature, on which the oxygen transfer material is carried, could be made by any common general methods well known by those skilled in the art, wherein the most typical method is following: the porous ceramic material particles tolerable to high temperature is immersed into a precursor solution of the oxygen transfer material, after saturation of immersion, the precursor of the oxygen transfer material present in internal pores of the above porous ceramic material particles tolerable to high temperature is subjected to drying and calcinations so as to be converted into the oxygen transfer material. When the oxygen transfer material is oxide of iron, its precursor could be any salt solution of various chloride of iron. The above immersion, drying and calcinations could be repeated several times, however the final porous ceramic material particles tolerable to high temperature, on which the oxygen transfer material is carried, should keep a specific ratio of the volume of pores, for example 15-30 volume pore rate, so as for the oxygen transfer material present in the above pores to be deoxidized or oxidized thereafter.

As above described, because the bulk density of porous ceramic material particles tolerable to high temperature, on which the oxygen transfer material is carried, is much higher than that of the raw coal and char, thereby the weight of the above-identified porous ceramic material particles is also much higher than that of coal or char particles of which bulk or volume is the same as the above- identified porous ceramic material particles. Therefore, by the effect of same fluidizing force derived from the fluidizing bed, the fluidizing or floating height of the above raw coal and char particles is much higher than that of the above porous ceramic material particles tolerable to high temperature, on which the oxygen transfer material is carried, in other words, on the fluidizing or floating height of the above specific porous ceramic material particles tolerable to high temperature, on which the oxygen transfer material is carried, there must just be fluidized or floating particles of the raw coal or char of which size is much larger than that of the above specific porous ceramic material particles, the other particles of the raw coal or char else of which size is smaller than or equal to that of the above specific porous ceramic material particles are fluidized or floating on the larger height, if the heights of the upward flare opening of downcomer (107) shown in Fig. 2A and the top end having at least one side cut of the vertical baffle (10V) shown in Fig. 2B are adjusted to the fluidizing or floating height of the above specific porous ceramic material particles on which the oxygen transfer material is carried, and the hole diameter of mesh (108) on them is adjusted to be equal to the diameter of the above-mentioned specific porous ceramic material particles, by the effect of fluidizing bed, this mesh (108) just allows the above specific porous ceramic material particles tolerable to high temperature, on which the spent oxygen transfer material is carried, pass through it and retains the particles of raw coal or char of which size is much larger than that of the above identified porous ceramic material particles on the same fluidizing or floating height in the medium & low temperature pyrolysis zone (105). In this way, the separation between the above porous ceramic material particles tolerable to high temperature, on which the spent oxygen transfer material is carried, and the particles of the raw coal and char is realized, so as to achieve the separation between the spent oxygen transfer material and the particles of the raw coal and char.

It must be indicated that, in the above medium & low temperature pyrolyzer (100) shown in Fig. 1, there could be one or more the above medium & low temperature pyrolysis zones (105) each which of structure may be the same as or different from that of other else, for example, the medium & low temperature pyrolysis zones (105) which of structures are shown in Fig. 2A and 2B could be arranged alternately in the above medium & low temperature pyrolyzer (100).

In the case that the above medium & low temperature pyrolyzer (100) communicates with the oxygen transfer material regenerator (200) via line (103) for spent oxygen transfer material delivery and line (104) for regenerated oxygen transfer material delivery, the above-mentioned both reactors necessarily are separated by atmosphere from each other due to the deoxidization atmosphere in the above medium & low temperature pyrolyzer (100) and oxidization atmosphere in the above the oxygen transfer material regenerator (200). As shown in Fig. 1, the steam could be used as medium for atmosphere separation between the above medium & low temperature pyrolyzer (100) and the oxygen transfer material regenerator (200).

The time when the raw coal resides in the above medium & low temperature pyrolyzer (100) generally depends on the types and operation condition of applied coal pyrolyzer or coal medium & low temperature pyrolyzer (100). Such process parameters could be available from operation handbook or product specification of regarding commercial equipments, or be find out from the documents or references, in the prior art, well known by those skilled in the art. With respect to coal pyrolyzer or coal medium & low temperature pyrolyzer (100) of fluidizing bed types, the time that the raw coal resides therein generally is about 20 minutes - 1 hour, and preferably about 30 minutes - 45 minutes.

Oxygen lost or depleted vitiated air discharged from the upper portion or top of the oxygen transfer material regenerator (200) may contain a certain quantity of solid tiny particles or dust, which could include tiny or small particles or dust of oxygen transfer material and minor quantity of the raw coal or char entrapped into the above regenerator (200) and their combustion products. Preferably, prior to emission or heat utilization, the above oxygen lost or depleted vitiated air entraining such solid tiny or small particles or dust is subjected to solid-gas separation on one stage or multi-stage via the general common solid-gas or liquid-gas separation equipments, for instance cyclone (207) and /or filter or membrane (209) as shown in Fig. 4.

The invention is further described with reference to following exemplary examples in detail; however such exemplary examples are not intended to limit the scope of the invention in any manner.

EXAMPLE

Example 1

The medium & low temperature pyrolysis system for coal, as shown in Figs. 1 and 2 was used to perform the process for producing upgraded coal, pyrolysis gas with high calorific value, and tar or liquefied synthetic oil according to the present invention.

Firstly, the soft coal with following chemical composition was crushed into particles with following particles diameter distribution via common general crusher.

5 mm >Diameter of 95 weight% soft coal particles > 1 mm;

10mm >Diameter of 100 weight% soft coal particles > 500 microns

The applied raw soft coal had the chemical composition as following:

Table 1

The above value was based on weight

In general, the moisture in the raw coal was not limited, however the moisture in the raw soft coal applied to this example 1 was about 14 weight %. Its calorific value was about 19900 joule/gram. Optionally, the raw coal could be subjected to pre-heating or pre-drying so as for the moisture contained therein to reach below 12 weight % and for its temperature to keep about 120°C. The above finely divided and optionally dried soft coal particles was firstly fed into coal pyrolyzer or coal medium & low temperature pyrolyzer (100) of fluidization bed type on flow rate of 1000 kilogram/hour via the well know lock hopper system (not shown). The above pyrolyzer or medium & low temperature pyrolyzer (100) had operation temperature of about 550 °C , and operation pressure of about 35 bar. Steam under about 700 °C was sprayed into the above medium & low temperature pyrolyzer (100) at bottom on flow rate of 1000 cubic meter/hour via the well know pressurized nozzles, and inputted steam then passed through perforations of perforated baffle (106) to enter the medium & low temperature pyrolysis zone (105), meantime the above pyrolyzer or medium & low temperature pyrolyzer (100) was rapidly fell into its operation temperature and operation pressure. The height of the medium & low temperature pyrolysis zone (105) was 1.2 meter, which depended on velocity of fluidizing medium. FeO was fed into the medium & low temperature pyrolysis zone (105) on flow rate of 160 kilogram/hour via line (104) for regenerated oxygen transfer material delivery and downcomer (107) or hollow conduct shown in Fig.2, by the effect of the fluidization bed, the above raw soft coal particles, FeO particles, and steam were fully mixed, and then occurred aforesaid reactions so as to generate pyrolysis gas or pyrolysis gas pyrolyzed at medium & low temperature. The raw soft coal therein was dehydrated and lost medium & low temperature volatiles so as to be converted into semi-char or char while FeO was deoxidized to release O so as to be converted into Fe. The particle diameter of FeO fed into the medium & low temperature pyrolysis zone (105) ranged from lmicron to 1 mm, wherein particles diameter of 95 weight % FeO was smaller than 100 micron. The time when coal resided in the above pyrolyzer or medium & low temperature pyrolyzer (100) generally was about 45 minutes.

The diameter of the above mentioned particles was determined by well known sieve analysis method or specific surface method. The holes diameter of the mesh (108), which was made from high temperature resistant alloy based on Ni, and possessed excellent strength and ability resistant to deformation under or below about 900 °C, was 1 mm.

Fe was physically separated from the resultant char via the separation mechanism shown in Fig.2, separated Fe entered into the oxygen transfer material regenerator (200) via line (103) for spent oxygen transfer material delivery for regeneration, on the other hand, the produced char was discharged out of the above pyrolyzer or medium & low temperature pyrolyzer (100) (via a char outlet at perforated baffle (106) or/and another char outlet at side wall or bottom wall of the pyrolyzer or medium & low temperature pyrolyzer (100).

The temperature of char discharged out of the above pyrolyzer (100) was about 550°C,such char was treated by cooling deactivation by deactivating or inactivating coolers (not shown) well known by those skilled in the art so as to be converted into the upgraded coal.

The above upgraded coal had the chemical composition as following:

Table 2

The above value was based on weight

The calorific value of the above upgraded coal was measured as 29500 joule/gram. From this it was clear that the calorific value of coal was greatly enhanced by the aforesaid processing on it.

The pyrolysis gas discharged from the above pyrolyzer or medium & low temperature pyrolyzer (100) was filtrated out solid tiny or small particles or dust entrained therein via the cyclone (114) as shown in Fig. 1, and then carried out heat exchange in the heat exchanger (115) shown in Fig. 1, thereby its temperature was lowered to 70°C-150 ^° C , later such separated pyrolysis gas passed through condenser (300) shown in Fig. 1 which further lowered the temperature of the above gas to 22 ^° C-35 ^° C , so as to separate tar or liquefied synthetic oil form the above gas.

Pyrolysis gas had chemical composition as following:

Table 3

The above value was based on mole

The calorific value of the above pyrolysis gas after dehydration was about 18000 kilojoules/cubic meter; from this it was very clear that it was a gaseous fuel with high calorific value

Tar pyrolyzed at medium & low temperature had chemical composition as following: Table 4

The above value was based on weight Tar pyrolyzed at medium & low temperature had elements composition as following: Table 5

The above value was based on weight

Fe generated in the medium & low temperature pyrolyzer (100) entered the bottom of the oxygen transfer material regenerator (200) via line (103) for spent oxygen transfer material delivery, then by the entraining effect of hot air sprayed into the above regenerator (200) at bottom, Fe was upwardly entrained and lifted to the upper portion of the above regenerator (200), during the upward movement, Fe reacted with oxygen contained in air by oxidization so as to be converted into FeO, which of period a lot of heat was emitted. The hot air at 300°C was sprayed into the bottom of the regenerator (200) on flow rate of about 100 cubic meter/hour via the pressurized nozzles, the operation temperature and pressure of the above oxygen transfer material regenerator

(200) were about 900°Cand 35 bar respectively, and the steam was used for atmosphere separation between the above regenerator (200) and the above medium & low temperature pyrolyzer (100). In the initial stage of operation of the above regenerator (200), the temperature of the above hot air could be increased to about 1000°C so as for the above regenerator (200) to fall into its operation temperature, however after its operation temperature was reached, and the above exothermic reaction has been continuing proceeding, the temperature of the above hot air could be lowered to about 300 ^° C.

The source of the hot air could come from the above heat exchanger where heat exchanging medium exchanged heat with pyrolysis gas or gas pyrolyzed at medium & low temperature. As shown in Fig. 1, air pressurized by the compressor (301) was fed into the above heat exchanger

(115) as the heat exchanging medium, and then the hot air heated to about 300°C exited the above heat exchanger (115), and was fed into the above oxygen transfer material regenerator (200).

The oxygen lost or depleted vitiated air discharged from the upper portion or top of the above oxygen transfer material regenerator (200) could be subjected to solid-gas separation via cyclone, filter and /or membrane (not shown), then was fed into expander (302) so as to drive steam boiler (305) or steam turbine for generation of electricity.

Example 2

The finely divided soft coal particles applied in the example 1 was mixed with pyrrhotine (Fe(i-x)S) (wherein (1-X) generally was about 0.8, its particles size was equal to or similar to that of the crushed soft coal particles) in mixture proportion of 99 :1, then the resultant admixture was fed into the above medium & low temperature pyrolyzer (100) in the same manner as that in the example 1. By the catalysis effect of the above pyrrhotine and FeS generated during coal pyrolysis processing, coal or tar derived from coal pyrolysis took place fragmentation reaction, and then reacted with hydrogen contained in coal pyrolysis gas by hydrogenation so as to produce liquefied synthetic oil with low molecule weight.

Finally, pryolysis gas had the chemical composition as following:

Table 6

The above value was based on mole

The calorific value of the above pyrolysis gas after dehydration was about 16000 kilojoules/cubic meter, from this it was very clear that it was still a gaseous fuel with high calorific value

The above liquefied synthetic oil had the chemical composition as following: Table 7

The above value was based on weight

The above liquefied synthetic oil had the elements composition as following:

Table 8

The above value was based on weight

The process parameters applied in the example 2 were the same as that applied in the example 1, wherein those raw material composition, process parameters, and products compositions etc that were not mentioned in the example 2 were same as that identified by the example 1 unless otherwise stated.

The chemical or elements compositions for the above soft coal, upgraded coal, pyrolysis gas, tar, or liquefied synthetic oil were measured by any methods well known by those skilled in the art, for example, they were measured by Spectroscopic Methods.

Although a few embodiments according to the present invention have been shown and described, the present invention is not limited to the described embodiments. Instead, it would be appreciated by those skilled in the art that any changes and modification may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by appended claims and their equivalents.