Process and Plant for Refining Raw Materials Containing Organic Constituents

This invention relates to a process and a plant for refining raw materials containing organic constituents, such as solids containing oil, bitumen and/or kerogen, in particular oil or tar sand or oil shale.

In view of an increasing shortage of petroleum deposits, the economic exploita- tion of raw materials containing organic constituents, such as oil or tar sands or oil shale, has become of greater interest. Oil or tar sands are mixtures of clay, sand, water and hydrocarbons. The latter can have different compositions and range from bitumen to normal crude oil. The hydrocarbon content in the sands is between about 1 and 18%. The economic efficiency of an exploitation increases with the hydrocarbon content. Oil or tar sands can be recovered by surface mining. When extracting them from deeper soil layers, an initial processing of the oil or tar sand already is effected in situ. Steam is introduced into the deposit, in order to liquefy the hydrocarbons. Therefore, this kind of oil recovery requires very much water, which in addition cannot be discharged quite free from oil.

Oil shales are rocks which contain bitumen or low-volatility oils. The content of organic matter (kerogen) lies between about 10 and 30%. Oil shales are no shales in a petrographic sense, but layered, not schistous, sedimentary rocks. The recovery of hydrocarbons, such as oil from oil shale, traditionally is effected by mining and subsequent pyrolysis (carbonization at 500 ⁰ C). Alternatively, there is also used the subsurface recovery (in situ) by pressing a steam-air mixture into the rock previously loosened by blasting and ignition of a flame front, which expels the hydrocarbons such as oil.

The previous recovery of hydrocarbons, such as crude oil from oil or tar sands or oil shale thus is relatively cost-intensive. With rising oil prices, the recovery of hydrocarbons, such as crude oil, from oil or tar sands and oil shale becomes increasingly interesting in economic terms. An essential problem in the present recovery of hydrocarbons, such as crude oil, from oil or tar sands and oil shales is the necessary high consumption of water and the emission of waste waters containing residual oil.

From U.S. patent 4,507,195 a process for coking contaminated oil shale or tar sand oil on solids distilled in retorts is known. Here, the hydrocarbonaceous solids are mixed with a hot heat transfer material, in order to raise the temperature of the solids to a temperature suitable for the pyrolysis of the hydrocarbons. The mixture is maintained in a pyrolysis zone, until a sufficient amount of hydrocarbon vapours is released. In the pyrolysis zone, a stripping gas is passed through the mixture, in order to lower the dew point of the resulting hydrocarbon vapours and entrain the fine particles. Accordingly, a mixture of contaminated hydrocarbon vapours, stripping gas and entrained fine particles is obtained from the pyrolysis zone. From the contaminated hydrocarbon vapours, a heavy fraction is separated and thermally cracked in a fluidized bed consisting of the fine parti- cles, whereby the impurities together with coke are deposited on the fine particles in the fluidized bed. The product oil vapours are withdrawn from the coking container. As heat transfer material, recirculated solids residues from pyrolyzed oil shale or tar sand is used, which was guided through a combustion zone, in order to burn remaining carbon and provide the heat for the pyrolysis of the raw material. Since there is no pressure seal between the combustion zone and the pyrolysis furnace, the oxidizing atmosphere of the combustion zone can enter the pyrolysis furnace and impair the quality of the oil vapour. Thermal cracking in the coking container also consumes much energy and therefore is expensive.

From EP 1 015 527 B1 , a process for the thermal treatment of feedstock containing volatile, combustible constituents is known, wherein the feedstock is mixed with hot granular solids from a collecting bin in a pyrolysis reactor, in which relatively high temperatures exist. This should lead to cracking reactions in the gases and vapours in the reactor.

Beside the thermal cracking used in the above-mentioned processes, catalytic cracking processes are also known. In Fluid Catalytic Cracking (FCC), the heavy distillate of a refinery is decomposed to gases, liquefied gases and gasolines, preferably to long-chain n-alkanes and i-alkanes. Cracking generally is effected at temperatures between 450 and 550 ⁰ C and a reactor pressure of 1.4 bar by means of an alumosilicate-based zeolite catalyst. FCC crackers are described for instance in US 7,135,151 B1 , US 2005/0118076 A1 or US 2006/0231459 A1. An exemplary catalyst is disclosed in WO 2006/131506 A1.

As further possibilities for the further treatment of hydrocarbon fractions, hy- drotreatment and hydrocracking are mentioned by way of example.

It is the object of the present invention to provide a more efficient process for utilizing the organic constituents of raw materials, such as materials containing oil and/or bitumen, in particular oil or tar sand or oil shale.

This object substantially is solved with the invention by a process with the following steps:

supplying the raw materials to a reactor and expelling a fuel gas at a temperature of about 300 to 1000 ⁰ C, preferably about 500 to 800 ⁰ C, introducing the solids left in the reactor including the non-evaporated fractions of heavy hydrocarbons into a furnace,

burning the heavy hydrocarbons left in the solids in the furnace at a temperature of 600 to 1500 ⁰ C, preferably 700 to 900 ⁰ C, recirculating hot solids from the furnace into the reactor, wherein the oxidizing atmosphere of the furnace is separated from the atmosphere of the reactor by means of a fluidized solid seal.

In the reactor, the hydrocarbons contained in the raw materials can volatilize as fuel gas preferably for 60% to 80%, particularly preferably for 65% to 70% - at a temperature of preferably 400to 790 ⁰ C - and, upon gas cleaning, advanta- geously be used for instance in metallurgical processes (e.g. reduction of iron- containing ores), calcination processes (e.g. gold ore and the like), calciners (AI ₂ O ₃ , alum earth, gypsum, loam and the like) or pelletizing plants. The remaining amount of hydrocarbons left in the solids is burnt in a furnace configured as heat generator, in order to provide the heat required in the reactor, which is transferred into the reactor via the solids withdrawn from the furnace. Between the furnace and the reactor a seal is provided, in order to separate the oxidizing atmosphere of the furnace from the distillation section of the reactor and avoid an oxidation, combustion or even explosion of the fuel gases generated in the reactor. In accordance with a preferred aspect of the invention, the raw materi- als are dried and/or preheated in a one- or multistage process before being introduced into the reactor. Drying can be effected at a temperature of about 80 to 120 ⁰ C, and preheating at a temperature of about 110 to 300 ⁰ C. With a rather low loss of organic constituents, the water content should largely be removed from the raw materials, wherein the ultralight hydrocarbons contained in the raw material are separated for instance by distillation and are supplied as product to the fuel gas originating from the reactor. The water can be supplied to a sewage treatment plant. Preheating serves the purpose of minimizing the mass flow which is recirculated from the furnace into the reactor as heat transfer medium. As a result, the thermal energy possibly to be supplied to the reactor in addition is reduced or a suspension preheater correspondingly. As preheater, a fluidized

bed with a heat transfer medium can be used, or the heat can also be transferred indirectly.

The reactor serves the in particular distillative expulsion of the organic constitu- ent contained in the dried and/or preheated raw material as fuel gas. For optimizing the heat transfer of the solids fed into the reactor a circulating fluidized bed, a stationary fluidized bed, an annular fluidized bed or a transport or flash reactor can for instance be used.

In a succeeding step, the fuel gas obtained can be processed to a uniform or different quality and/or condition, e.g. by desulfurization or cracking.

In accordance with the invention, fluidizing the reactor is effected with gas streams which are obtained from the drier/preheater and/or the reactor itself and contain light hydrocarbons, in particular an amount of the fuel gas originating from the reactor. It is, however, also possible to supply nitrogen, hydrogen, carbon dioxide gas mixtures containing air or oxygen, or an amount of the waste gas from the furnace to the reactor as fluidizing gas. A portion of air or oxygen in the gas mixture can be used for adjusting or initiating a partial combustion for adapting the temperature and/or the yield. It is also possible to perform the flu- idization by means of an inert gas such as nitrogen. The fluidizing gases can be supplied to the reactor cold or preheated.

In accordance with a development of the invention, it is possible to divide the reactor for expelling the hydrocarbons into several individual reactors, in order to adjust more accurately defined temperatures and gas compositions.

To raise the efficiency, the reactor can be operated under a reduced pressure in the range from 0.001 to 1 bar (abs.). Lowering the pressure promotes the expul-

sion of the fuel gas from the solids and reduces the risk of dropping below the dew point.

To improve or control the yield in the reactor, e.g. electromagnetic waves (e.g. microwaves), ultrasound or the like can be used. It is likewise possible to use catalytically active substances in the reactor, which can improve and control or regulate the evaporation of the organic constituents in the reactor or control and change their composition.

The furnace serves to generate heat for the reactor, wherein the temperature of for instance 300 to 800°C, which is required in the reactor, is introduced into the reactor via the solids heated in the furnace. In accordance with the invention, the combustion in the furnace is performed in an atmosphere with an excess of oxygen, which can be produced by supplying air, air enriched with oxygen or pure oxygen, in order to ensure a nearly complete combustion of the organic constituents left in the solids, in particular of the heavy oil components or oil products. The oxygen containing gases can be supplied cold or preheated, so that the furnace temperature preferably lies between 700 and 900 ⁰ C.

In accordance with the invention, a circulating fluidized bed, an annular fluidized bed, a stationary fluidized bed, a transport or flash reactor, a rotary kiln or a grate combustion can be used as furnace. To increase the utilization of energy, a staged combustion is preferred. Additional fuel can be supplied to the furnace e.g. in the form of untreated raw material, coal, coke, waste materials, biomass or the like, or an amount of the fuel gas obtained in the reactor.

In a staged combustion, it is preferred to perform at least one stage as a sub- stoichiometric combustion (i.e. with a lack of oxygen) and at least one stage as a superstoichiometric combustion (i.e. with an excess of oxygen).

In a staged combustion, it is also possible to combine part of or the entire waste gas from a substoichiometric combustion stage with the fuel gas from the reactor or to use it separately in another plant (e.g. metallurgical plant) or in another part of the plant (e.g. reactor or preheating). Thereby, the yield of gas and/or the gas quality from the generation of fuel gas can be changed and regulated or controlled.

The temperature in the furnace should be adjusted such that the optimum temperature required for expelling fuel gas thereby is achieved in the reactor. At higher temperatures, less solids containing organic constituents are delivered from the reactor into the furnace, so that additional fuel might be required. The optimum is determined by means of the properties of the raw material used.

It is also possible to introduce waste gas from the furnace or from the down- stream plant, in which the fuel gas is required (e.g. metallurgical plant), into the furnace, in order to operate the furnace or regulate or control the temperature.

To improve the energy balance, the heat generated in the furnace can be recovered from the waste gas and/or the calcination residue in accordance with the development of the invention. In a manner known per se, this can be effected by means of a heat recovery system, for instance in the form of a fluidized-bed cooler/heater, a heat recovery cyclone, a waste heat boiler or a suspension pre- heater (Venturi/cyclone) combination. It is also possible to use the heat generated in the furnace for preheating the fluidizing streams of the drier/preheater and/or reactor or for indirectly heating the drier/preheater. The heat can also be utilized for steam generation, e.g. for the further power generation.

This invention also extends to a plant for refining raw materials containing organic constituents, such as solids containing oil and/or bitumen, in particular oil or tar sand or oil shale, but also oil-containing fluidizable materials or wastes,

comprising a reactor to which the raw materials are supplied, a furnace to which solids and fuel coming from the reactor are supplied, a return conduit via which hot solids generated in the furnace are recirculated to the reactor, and a blocking means for separating the gas atmospheres of the furnace and of the reactor, which can be a fluidized-bed reactor.

In accordance with a development of the invention, the plant also can include a drier/preheater for drying/preheating the raw materials introduced.

The furnace can be a fluidized-bed furnace, a rotary kiln or a flash reactor.

Downstream of the furnace a circulating fluidized bed, a heat recovery system for the waste gas and/or the calcination residue preferably is provided.

Furthermore, gas cleaning units or gas processing stages can be provided for the gases generated (waste gas and fuel gas).

In a preferred aspect of the invention, the blocking device between the furnace and the reactor includes a downpipe via which a stream of solids is withdrawn from the furnace, a riser pipe which close to the bottom of the downpipe is branched off from the same to the top, and a conveying gas supply below the riser pipe, wherein the stream of solids withdrawn from the furnace is fluidized by the conveying gas and transported to the reactor via the riser pipe. This does not only provide for a regulation of the mass flow of heat transfer medium sup- plied to the reactor, which can be controlled via the supply of the conveying gas, but also for a reliable pressure seal between the oxidizing atmosphere of the furnace and the reactor. An oxidation, combustion or even explosion of the fuel gases expelled in the reactor thus can reliably be avoided. Apart from the so- called seal pot construction described above, a lock hopper, a check valve or combinations of these elements can also be used.

Further objectives, features, advantages and possible applications of the invention can be taken from the following description of embodiments and the drawings. All features described and/or illustrated form the subject-matter of the in- vention per se or in any combination, also independent of their inclusion in the claims or their back-reference.

In the drawings:

Fig. 1 schematically shows an exemplary plant for performing a process in accordance with the invention, and

Fig. 2 schematically shows a possible blocking device arranged between the furnace and the reactor.

A plant for refining raw materials containing organic constituents, which is schematically shown in Fig. 1 , includes a one- or multistage drier/preheater 2, to which raw materials, such as oil or tar sand or oil shale, are supplied via a supply conduit 1. With a temperature of for instance 200 ⁰ C, the dried/preheated solids are supplied to a reactor 6 suitable for distillation, in which the same are heated to 500 to 750 ⁰ C, and thereby the organic constituents are expelled as fuel gas. Upon passing through a cleaning and/or processing 8, the fuel gases obtained are discharged for further use.

The solids left in the reactor 6 after expelling the fuel gases, which contain amounts of heavy hydrocarbons, are supplied via a conduit 11 to a furnace 12 configured e.g. as circulating fluidized-bed furnace, to which e.g. air and an amount of the fuel gas originating from the reactor 6 can be supplied via conduits 13, 14 for starting the furnace 12 or for controlling the same.

From the furnace 12, a return conduit 15 leads to a sealing device 16 shown in detail in Fig. 2, which is used for separating the furnace and reactor atmospheres and is connected with the reactor 6 via a conduit 17.

The waste gas from the furnace 12 is supplied via a conduit 18 to a heat recovery 19 and then via a conduit 20 to a gas cleaning 21. Via a conduit 22, the calcination residue of the furnace 12 also can be supplied to a heat recovery 23. Via a conduit 24, the heated gas obtained in the heat recoveries 19, 23 (e.g. air or other mixtures with oxygen) can be introduced into the furnace 6 as oxidizing agent.

It is possible, to energetically couple the cleaning and processing stage 8 with the heat recovery 19, in order to achieve a maximum energy integration or energy utilization.

In Fig. 2, a so-called seal pot is shown as an example for a suitable sealing device 16. From the furnace 12, the descending return conduit 15 is branched off, which is also referred to as downpipe 50 or downer and via which hot solids are discharged as heat transfer media for the reactor 6. The inlet region of the downpipe 50 also is referred to as head 51 of the downpipe. Just before the bottom 52 of the downpipe 50, an upwardly directed conduit, which also is referred to as rising pipe 52 or riser, is branched off from the downpipe 50 and substantially extends against gravity. The diameter of the downpipe 50 is greater than that of the rising pipe 53, preferably about twice as great as that of the rising pipe 53. The inlet region or foot 54 of the rising pipe 53 can slightly protrude into the downpipe 50 or terminate flush with the wall of the downpipe. At the upper end or head 55 of the rising pipe 53, the rising pipe opens into a discharge pot 56, from which the solids can flow off into the reactor 6 via the conduit 17. At the bottom 52 of the downpipe 50, below the foot 54 of the rising pipe, conveying gas is supplied via a nozzle 57 connected to the supply conduit 58, in order to

fluidize the stream of solids in the rising pipe 53. As fluidizing gas, every suitable conveying gas can be used in principle. Preferably, a third, in particular inert gas such as nitrogen is used, in order to ensure the separation of the gas atmospheres between the fluidized bed in the furnace 12 and the head of the rising pipe 53.

The plant for refining raw materials containing organic constituents (hydrocarbons) in accordance with the present invention, substantially can be constructed as described above. In the following, its mode of operation, function and action will be explained in greater detail.

The ground or unground, e.g. oil-containing raw materials supplied via the supply conduit 1 are heated to a temperature of 105 to 160 ⁰ C and dried in the drier/preheater 2. for instance by means of fluidizing gas supplied via a fluidizing conduit 25a, and preheated to about 450°C. Via a discharge conduit 26, a gas stream containing superlight oil components is supplied to a gas cleaning and processing 8. In the reactor 6, the preheated solids are heated to a temperature of for instance 650 to 700 ⁰ C by means of the hot solids recirculated from the furnace 12, whereby 61 to 75 wt-% of the hydrocarbons contained in the solids are expelled as fuel gas. Via conduit 7, the fuel gases obtained are supplied to the gas processing 8 and, upon cleaning, discharged as fuel gas for further use with a temperature of for instance about 200 to 300 ⁰ C. An amount of the fuel gas and of the light hydrocarbon components originating from the drier/preheater 2 can be recirculated to the reactor 6 via a fluidizing conduit 25b.

Via conduit 11 , the solids left in the reactor including the non-evaporated heavy hydrocarbon components are introduced into the furnace 12 and burnt there at a temperature of for instance about 850 ⁰ C. There are merely burnt the hydrocarbons still contained in the solids, and the solids thereby are brought to a high temperature, so that they can serve as heat transfer media for the reactor 6.

The calcination residue, which via conduit 22 is delivered to the heat recovery 23, is discharged to the outside via a discharge conduit 27.

List of Reference Numerals:

1 supply conduit for solids

2 drier/preheater

3 conduit for dried/preheated solids

6 reactor for solids

7 conduit for fuel gas

8 cleaning/processing for fuel gas

11 conduit for solids

12 furnace (heat generator)

13 conduit for combustion gas

14 conduit for fuel gas

15 return conduit for solids

16 blocking device (seal pot)

17 conduit for solids

18 conduit for waste gas

19 heat recovery for waste gas

20 conduit for waste gas

21 gas cleaning for waste gas

22 conduit for calcination residue

23 heat recovery for calcination residue

24 conduit for combustion gas

25a fluidizing conduit (e.g. air, waste gas)

25b fluidizing conduit (fuel gas)

26 discharge conduit for fuel gas

27 discharge conduit for calcination residue

50 downpipe

51 head of the downpipe

52 bottom of the downpipe

riser pipe foot of the riser pipe head of the riser pipe discharge pot nozzle supply conduit