DESCRIPTION

This invention relates to a facility and method for the treatment of organic compounds, in particular for the treatment of biomass deriving from human activities associated with agriculture, horticulture and forestry, and from urban organic wastes.

The invention has its preferred but not exclusive application in the sector of the treatment of organic compounds for the production of electrical and/or thermal energy.

In this sector facilities for the incineration of wastes by means of a high temperature combustion process from which the gaseous mixture produced is typically utilised for the generation of thermal imagery are widely in use. As is known, despite modern systems for the removal of pollutants provided in such facilities, the substances emitted from incinerators contribute to a progressive increase in environmental pollution.

Facilities, typically of small capacity, which carry out a process of thermochemical decomposition of organic matter in which the latter is divided into a solid fraction and a gaseous fraction which can be used to generate electrical and/or thermal energy are also known.

The process of thermochemical decomposition finds application in pyrolysis and gasification facilities which however are more complex facilities than incinerators.

Up to now the construction of such facilities has been at an experimental stage which is intended in particular to achieve greater energy efficiency in the corresponding processes for the generation of electrical energy. On the other hand pyrolysis and gasification facilities have many advantages in comparison with known incinerators, such as:

1. greater efficiency in the system and therefore a greater efficiency of the process;

2. simpler management of the processed products;

3. no atmospheric emissions of processed gas apart from exhaust gases produced by internal combustion engines for the generation of electrical energy;

4. completely inert discharged solid material.

One example of a recycling facility which uses a pyrolysis process is described in German patent application DE 10 2009 012668.

However in this facility the pyrolysis process does not take place with the control of pressure, with the result that it is difficult to control the process unless it is operated at particularly high pressures. In fact when the process is carried out at ambient pressure there is inevitably uncontrolled ingress of external agents.

The problem underlying this invention is that of providing a facility and method for the treatment of organic compounds which is functionally and structurally designed to overcome the disadvantages mentioned with reference to the cited known art.

This problem has been resolved by the invention through a facility and method for the treatment of organic compounds achieved in accordance with the attached claims.

Characteristics and advantages of the invention will be more apparent from the description of a preferred embodiment illustrated by way of indication and without limitation with reference to the appended drawings in which:

• Figure 1 is a diagrammatical perspective view of a facility for the

treatment of organic compounds according to the invention;

• Figure 2 is a diagrammatical view from above of a facility for the

treatment of organic compounds according to the invention;

• Figure 3 is a perspective view of a unit and corresponding drying

block of a facility for the treatment of organic compounds according to the invention;

• Figure 4 is a flow diagram representing the process for the treatment of organic compounds according to the invention;

• Figure 5 is a diagrammatical view in cross-section of a heat

exchanger of a facility for the treatment of organic compounds according to the invention.

In the enclosed figures a facility for the treatment of organic compounds constructed in accordance with this invention is indicated as a whole by reference number 100.

Preferably, organic compounds A, diagrammatically illustrated in Figure 4, comprise grass cuttings, pruning waste, woodworking waste and/or urban organic wastes. Organic compounds A are also known as biomass. More preferably organic compounds A are biomass of the ligneous type.

In any event, as will be evident from the remainder of the description, the technical characteristics of the facility make it advantageously possible to achieve optimum treatment of all substances of an organic type, thus rendering the facility according to the invention particularly flexible.

In accordance with a preferred embodiment facility 100 comprises a first unit 1 incorporating drying means 11, diagrammatically illustrated in Figures 2 and 3, suitable for treating the abovementioned organic compounds A in order to obtain a substantially anhydrous material B which is subsequently subjected to a pyrolysis process.

With reference again to Figure 1, organic compounds A preferably undergo a stage of grinding and preparation to reduce them into substantially uniform fragments which are then deposited in storage unit 1A before being delivered to the drying treatment. This arrangement makes it possible to reduce organic compounds A to a size which is suitable for the subsequent treatments provided by facility 100.

First unit 1 provides for heating organic compounds A by drying means 11, which are in themselves known, to evaporate the water Al present therein, thus obtaining a substantially anhydrous material B.

Advantageously evaporated water Al is delivered from first unit 1 to a condenser IB and subsequently to a purifier 1C for condensation and purification respectively in order to bring the concentration of polluting substances present to a value below the limit imposed by current regulations.

Preferably purification takes place through an electrolysis process.

Substantially anhydrous material B is transported, preferably by means of a screw conveyor 12 illustrated in Figure 2, to a second unit 2 in facility 100 so that a pyrolysis process can be performed.

Substantially anhydrous material B is therefore subjected to a pyrolysis process from which a gaseous fraction Bl and a solid fraction B2 resulting from thermochemical decomposition of the material treated are obtained. In detail, with reference to Figure 2, second unit 2 includes a first reactor 21 in which substantially anhydrous material B is heated to a temperature of preferably 850-900°C. Second unit 2 also comprises control means 22 to carry out the pyrolysis process at a pressure slightly above the atmospheric pressure in such a way as to prevent the ingress of air into first reactor 21, that is to prevent the ingress of air coming from the external environment into first reactor 21, so that the process takes place substantially in the absence of ingress of air, that is it is performed substantially in the absence of oxidising agents such as oxygen coming from the external environment. This feature makes it possible to avoid an excess pressure in first reactor 21, fact that would require careful management in the course of the pyrolysis process. Also it should be borne in mind that the absence of ingress of air during the process prevents an uncontrolled ingress of oxidising agents whose present would make control particularly complex. The applicant has in fact found that by using a reactor in which the pressure is maintained only slightly above the atmospheric pressure it is possible to avoid the uncontrolled ingress of external agents without however requiring the high pressures provided by facilities operating at overpressure.

It will be noted that in the context of this invention the expression "pressure slightly above the atmospheric pressure" indicates a pressure greater than the latter, without however requiring any particular arrangements in the facility in comparison with operation at atmospheric pressure. For example a pressure in first reactor 21 which is greater than atmospheric pressure by a value of between 2 and 10 mm of water column (that is a pressure which is greater than atmospheric pressure by a value of between 19.613 Pa and 98.064 Pa) can be regarded as a pressure slightly above the atmospheric pressure according to the meaning of this invention.

Conduct of the pyrolysis process in the absence of an oxidising agent makes it possible to obtain a gaseous fraction Bl from substantially anhydrous material B comprising mainly hydrocarbons having a simple molecular chain (mainly methane CH _4; carbon monoxide CO, hydrogen H ₂ and carbon dioxide C0 ₂ ).

In greater detail, a range of between 70 and 80% of the total of the abovementioned gaseous fraction Bl may comprise:

· Methane CH ₄ ;

• Carbon monoxide CO;

• Hydrogen H ₂ ;

And the remaining 20-30% of the total may comprise:

. H ₂ 0;

· Carbon dioxide C0 ₂ ;

• Nitrogen N ₂ , in a small quantity.

Otherwise the abovementioned characteristics to carry out of the pyrolysis process make it possible to obtain the solid fraction B2 from substantially anhydrous material B, that is the residual solid material from the pyrolysis process, which is essentially carbon based and is transported preferably by means of a screw conveyor to a third unit 3 of facility 100 for a gasification process to be performed.

Control means 22 preferably comprise subdivider valves located at an entrance of second unit 2 for inserting of substantially anhydrous material B and counterpressure means located at an exit of second unit 2 for the exit of solid fraction B2 of substantially anhydrous material B to third unit 3. Advantageously, the fact that the material obtained from the drying stage is substantially anhydrous B, together with the abovementioned characteristics for performance of the pyrolysis process which that material subsequently undergoes, greatly restricts the formation of substances of carbonaceous material of intermediate molecular weight. Such substances are of a tarry consistency when subjected to a temperature below the operating temperature of the pyrolysis process and can therefore become deposited on the surfaces of facility 100 forming incrustations.

Third unit 3 includes a second reactor 31 to carry out the gasification process in which the abovementioned solid fraction B2 is heated to a temperature of preferably 900-1100°C to substantially reduce the carbon present by blowing steam provided in a controlled way through the facility, or a mixture of carbon monoxide and hydrogen. Preferably this gasification process completely reduces the carbon present in abovementioned solid fraction B2.

Specifically this process makes it possible to obtain a gaseous fraction CI and a solid fraction C2 from solid material B2 which is left over from the pyrolysis process.

Preferably first and second reactors 21, 31 take the form of a single reactor subdivided into two parts to carry out of the pyrolysis process and the subsequent gasification process.

In a preferred embodiment of the invention the drying process, together with the pyrolysis and gasification processes, advantageously make it possible to reduce organic compounds A entering first unit 1 by approximately 95%, that is solid fraction C2 obtained from the exiting gasification process represents approximately 5% of organic compounds A entering the drying process.

With reference to Figure 4, facility 100 for the treatment of organic compounds A comprises a fourth unit 4 including vitrification means 41 to carry out a process of vitrification of solid fraction C2 obtained from the gasification process. This solid fraction C2 is substantially devoid of carbon because this has been converted into a gaseous form included in the abovementioned gaseous fraction CI.

Therefore solid fraction C2, that is the solid residue obtained from the gasification process, essentially comprises inert ashes such as metals and glass originally present in organic compounds A, and possibly traces of toxic/harmful substances which are inerted by the vitrification process, which is in itself known, thus making it possible to dispose of that solid residue to a dump.

It will be noted that the vitrification process is facilitated by the high temperature, approximately 1200°C, to which solid fraction C2 obtained from second reactor 31 is subjected.

As described in the case of second unit 2, third unit 3 comprises control means 32 to carry out the gasification process at a pressure slightly above the atmospheric pressure in order to avoid the ingress of air into second reactor 31, that is in such a way as to prevent the ingress of air coming from the external environment into second reactor 31, so that this process takes place substantially in the absence of ingress of air, that is it takes place substantially in the absence of oxidising agents coming from the external environment.

Preferably a pressure in second reactor 31 which is greater than atmospheric pressure by a value of between 2 and 10 mm of water column (that is a pressure greater than atmospheric pressure by a value between 19.613 Pa and 98.064 Pa) can be regarded as a pressure slightly above the atmospheric pressure according to the meaning of this invention.

Control means 32 preferably comprise subdivider valves located at an entrance of the third unit 3 for inserting of solid fraction B2 of substantially anhydrous material B and counterpressure means located at an exit of the third unit 3 for exit of solid fraction C2 obtained from the gasification process.

Advantageously, the abovementioned features of the embodiment of the gasification process together with the stages of drying and pyrolysis according to the invention also strongly limit the formation of substances of a carbonaceous nature having an intermediate molecular weight which can form encrustations in facility 100.

The process of pyrolysis and gasification, which are placed in cascade, make it possible to obtain a gaseous mixture D comprising gaseous fraction Bl of substantially anhydrous material B and gaseous fraction CI obtained from the abovementioned gasification process for the generation of electrical energy E _EL and/or thermal energy, as will be more particularly described below.

In a preferred form of the invention a principal part Dl of gaseous mixture D, preferably approximately 90% of the total, is intended for the production of electrical energy E _EL while the residual part of gaseous mixture D, called secondary part D2, preferably approximately 10% of the total, is intended to feed combustion means, such as burners, to feed the abovementioned pyrolysis and gasification processes when the latter reach steady-state conditions.

Specifically steady-state conditions are reached when the pyrolysis and gasification processes are in a substantially stationary state in which they take place according to predetermined conditions (for example of temperature and pressure).

In other words, after a first transition stage in which first and second reactors 21, 31 of facility 100 are brought up to a predetermined operation state corresponding to which the pyrolysis and gasification processes take place under steady-state conditions, secondary part D2 of gaseous mixture D is intended to feed the burners to feed the abovementioned processes. It is obvious that this makes it possible to reduce the proportion of energy originating from external sources for feeding the pyrolysis and gasification processes, thus achieving a better energy efficiency of facility 100, that is a greater energy efficiency for facility 100, and thus achieving obvious advantages of an economic nature.

Furthermore, downstream from third unit 3, facility 100 for the treatment of organic compounds A may comprise a fifth unit 5 comprising a heat exchanger 51 to cool gaseous mixture D before it is subdivided into principal part Dl for the generation of electrical energy E _E _ and secondary part D2 intended to feed the abovementioned processes.

In a preferred embodiment of the invention heat exchanger 51 is of the surface type comprising a cooling circuit 52 through which a cooling fluid 53 flows. Gaseous mixture D is therefore cooled by countercurrent heat exchange with cooling fluid 53.

With reference to Figure 5, heat exchanger 51 comprises a shell and a first tubular element through which gaseous mixture D flows. The first tubular element has the shell on, so that the shell is coaxial with the first tubular element. This shell comprises cooling circuit 52 for conduct of the countercurrent heat exchange process between the fluid within the first tubular element and the fluid within the shell. Preferably cooling fluid 53 is substantially air which is inserted into heat exchanger 51 at ambient temperature, or at around 20°C.

Heat exchanger 51 makes it possible to cool gaseous mixture D from a temperature of approximately 1200°C on exit from third unit 3 to a temperature of approximately 200°C.

Advantageously cooling of gaseous mixture D takes place over a short time so that the formation of undesired substances, such as tarry substances and dioxins, is prevented.

In addition, the invention may provide that at least part of the flue gases produced by the burners are fed to a cooling circuit 52 for heating cooling fluid 53 by contact. In one embodiment of the invention, part of the flue gases produced by the burners is introduced into cooling circuit 52 approximately half way along the circuit so that cooling fluid 53 has a temperature of approximately 700°C at the point where gaseous mixture D is introduced into heat exchanger 51.

According to a preferred embodiment of the invention, at the point where gaseous mixture D is introduced into heat exchanger 51 provision is made for tapping off at least part of cooling fluid 53, preferably all of fluid 53, at a temperature of 700°C in order to feed the abovementioned pyrolysis and gasification processes together with secondary part D2 of gaseous mixture D.

In detail, the pyrolysis and gasification processes are fed exclusively by secondary part D2 of gaseous mixture D and by cooling fluid 52 exiting from heat exchanger 51 when these processes reach steady-state conditions. This characteristic makes it possible to carry out the pyrolysis, gasification and vitrification processes in such a way that they are self-feeding, that is, in other words, when the abovementioned steady-state conditions are established, the facility 100 does not need for an external source for providing a feed to the pyrolysis and gasification processes. There is therefore an increase in the energy efficiency of facility 100 according to the invention.

Facility 100 for the treatment of organic compounds A may also comprise a sixth unit 6 including a purification system 61 for purification of gaseous mixture D exiting from fifth unit 5, that is exiting from heat exchanger 51, to remove possible dust and other pollutants such as pollutants in the liquid state or of a tarry consistency present in suspension.

In this case, after purification of gaseous mixture D, the latter is subdivided into the principal part Dl and secondary part D2 mentioned above.

Purification system 61 comprises a plurality of washing columns, in themselves known, which are capable of purifying abovementioned gaseous mixture D by means of a wash fluid 62, for example a basic aqueous solution. This wash fluid 62 is subsequently delivered to a purifier 1C for purification in a manner similar to that provided for the evaporated water obtained from first unit 1. In addition to this, part of the purified water may be filtered and sent to a process water circuit to satisfy the water needs of the utilities provided for facility 100.

One embodiment of the invention may provide for one or more sensors for continuous monitoring of gaseous mixture D downstream from the gasification process but upstream from purification system 61 to control conduct of the pyrolysis and gasification processes.

These sensors are preferably intended to detect valuable combustible gases such as hydrogen H ₂ , methane CH ₄ , carbon monoxide CO, acetylene C ₂ H _2; inert gases such as nitrogen N ₂ and carbon dioxide C0 ₂ , or undesired compounds which are harmful to the functioning of facility 100, such as acids in general and aromatic hydrocarbons.

A seventh unit 7 including one or more internal combustion engines 71, for example Otto cycle engines, which can be associated with alternators 72 for the generation of electrical energy E _E L, may be provided for facility 100 according to the invention.

In particular internal combustion engines 71 may be fed by the principal part Dl of gaseous mixture D purified by purification system 61.

Preferably facility 100 may provide for a pressurestat accumulator 8 for the abovementioned purified gaseous mixture upstream from internal combustion engines 71, to control the continuous functioning of the electrical energy generation E _E L-

It is obvious that different thermal machines for the conversion of the energy which can be derived from the principal part Dl of gaseous mixture D into electrical energy are provided by the invention, such as, for example, turbines or hydrogen cells.

In a preferred embodiment of the invention, facility 100 is capable of generating a power of 2MW by means of alternators 72 associated with internal combustion engines 71.

Advantageously, facility 100 is intended to make use of the thermal energy E _T produced by the operation of internal combustion engines 71, for example to generate further electrical energy.

In particular facility 100 may incorporate heating means 9 for heating a liquid F using abovementioned thermal energy E _T , for example to heat water to a temperature of 100°C. This heated liquid F can then be used by one or more systems such as first unit 1 for the drying treatment of organic compound A and a system for remote heating through a suitable system of piping, and/or for the generation of additional electrical energy through corresponding thermal machines.

In one embodiment of the invention, one or more of abovementioned units 1,...,7 comprised in the facility 100, preferably each of the abovementioned units 1,...,7 comprised in the facility 100 for the treatment of organic compounds A, is preassembled into corresponding independent blocks BL1,...,BL7.

Specifically, blocks BL1,...,BL7 are independent of each other because the construction of a block including the corresponding unit of facility 100 is not associated with the construction of another block, making it possible to preassemble units 1,...,7 in the factory, therefore offering high modularity for the facility.

Preferably each block BL1,...,BL7 is a metal structure of substantially solid rectangular shape such as a container, in which a corresponding unit 1,...7 (possibly without its marginal parts) is included.

Such characteristics therefore make it possible to transport each block BL1,...,BL7 to the intended locality for the construction of facility 100 and subsequently to connect them appropriately in order to start up the latter. It will be noted that factory preassembly of the abovementioned units 1,...7 into corresponding blocks BL1,...,BL7 will advantageously make it possible to finish the construction of facility 100 in the location intended for its use, thus avoiding the construction and/or assembly of each of units 1,...,7 comprised in the facility 100 on site, fact that would obviously have an adverse impact on the costs and times required for constructing facility 100. Simplified management of the construction of facility 100 in the locality intended for its use is therefore achieved. Obviously a person skilled in the art could apply further modifications and variants to the invention described above in such a way as to satisfy specific and contingent application requirements, variants and modifications which would in any event fall within the scope of protection as defined by the following claims.

The invention thus resolves the problem stated, offering many advantages, including that of carrying out a facility and a method for the treatment of organic compounds comprising a pyrolysis and gasification process which is particularly simple and reliable and has greater energy efficiency than known facilities.

In particular the invention advantageously makes it possible to carry out the pyrolysis and gasification processes while avoiding overpressure in the corresponding reactors, fact that would require careful management, and to use part of gaseous mixture D obtained from such processes to feed the same, thus increasing the energy efficiency of the facility.

The stages of drying, pyrolysis and gasification also make it possible to avoid the presence of tarry substances in the gaseous mixture obtained from the facility, as well as in the waste products from the facility according to the invention.

In addition to this, the processes involved in this facility are suitable for the treatment of a wide range of substances, thus rendering the facility particularly versatile.

Furthermore, the characteristic of preassembling the plurality of units of the facility in corresponding independent blocks advantageously offers the facility a high level of modularity.