FR3037259A1 - SYSTEM FOR THE PRODUCTION AND PURIFICATION OF A SYNTHESIS GAS OR A BIOGAS - Google Patents

Abstract

The present invention relates to a system for the production and purification of a synthesis gas or a biogas, comprising a reactor (T) designed to produce said gas, a washing tower of said gas, of the countercurrent type (Tic) comprising an envelope provided with an inlet of a washing liquid, an inlet and an outlet of said gas arranged so as to allow a circulation of said gas against the flow of the circulation of the washing liquid, the countercurrent washing tower (Tic) comprising means designed to form droplets with the flow of the washing liquid so that they can trap particles contained in said gas. According to the invention, the system for producing and purifying a synthesis gas or a biogas comprises a cooler (R) connected downstream of said washing tower, said cooler comprising means for lowering the temperature of said gas so to increase are PCI (lower calorific value) and condense, on the one hand, the residual cold tars and, on the other hand, the residual water present in said gas, still containing soot. The droplets trap, in particular, a portion of the hot tars, fine soot, sulfur compounds, nitrogen, phosphorus, contained in the synthesis gas or in the biogas. The combination of a washing tower with a cooler, produces a synthesis gas or a biogas of high purity, practically free of particles and especially soot, tars. It can be advantageously used to operate a heat engine, a gas turbine.

Description

The present invention relates to a system for the production and purification of synthesis gas, commonly called "syngas", and which is produced by a gasification reactor consuming carbonaceous material. A gasification reactor can be used in a cogeneration plant that is designed to produce two forms of energy, for example electrical and heat. In principle, it uses locally produced energy such as syngas or biogas from biomass. The syngas produced in particular contains particles of ash and tars, a portion of water, which impairs its direct use in a heat engine, such as an internal combustion engine, a gas turbine. Also, the applicant has sought a solution to rid the syngas produced, in particular, in a cogeneration plant, of the particles it contains, so that this purified syngas can be used in a heat engine, such as an engine. internal combustion without altering its service life.

For this purpose, is proposed a system for producing and purifying a synthesis gas or a biogas, comprising a reactor designed to produce said gas, a washing tower of said gas, of the countercurrent type comprising a envelope provided with an inlet of a washing liquid, an inlet and an outlet of said gas arranged so as to allow a circulation of said gas countercurrently to the circulation of the washing liquid, the washing tower to countercurrent apparatus comprising means for forming droplets with the flow of the washing liquid so that they can trap particles contained in said gas; according to the invention, the system for producing and purifying said gas further comprises a cooler connected downstream of said washing tower, said cooler comprising means for lowering the temperature of said gas in order to increase are PCI (lower calorific value) and condense, on the one hand, the residual cold tars and, on the other hand, the residual water present in said, still containing soot. The droplets trap, in particular, a portion of the hot tars, fine soot, sulfur compounds, nitrogen, phosphorus, contained in the synthesis gas or in the biogas. The combination of a washing tower with a cooler, produces a synthesis gas or a biogas of high purity, practically free of particles and especially soot, tars. It can be advantageously used to operate a heat engine, a gas turbine.

According to an additional characteristic of the invention, the means designed to form droplets comprises an endless screw disposed in its operating position, along a vertical or near vertical axis, without play or virtually without play inside. said envelope, the arrival of the washing liquid being positioned in the upper part of the envelope, so that the droplets can be formed by rolling down the wall of the worm. More than half of the residual particles contained in the synthesis gas or in the biogas are captured in this washing tower incorporating the worm. The relatively large exchange area of the worm, due to the helical structure, causes the synthesis gas or biogas to cool. In an alternative embodiment, the means designed to form droplets comprises perforated plates, arranged horizontally in their operating position, without play or substantially without play inside said casing, the arrival of the washing liquid being positioned in the chamber. upper portion of the casing so that it can flow through the perforations and form droplets to trap the particles contained in said as it rises through said perforations. This variant embodiment also provides a good capture efficiency of the particles contained in the synthesis gas or in the biogas.

According to an additional characteristic of the invention, the lower part of the casing is opened and immersed in a compartment of a tank for the recovery and decantation of the washing liquid, the said liquid being collected in another compartment for reuse by pumping into said wash tower. The decanted liquid circulates in a loop inside the scrubber.

According to an additional characteristic of the invention, the system for producing and purifying said gas comprises a vane pump coupled to a motor capable of rotating it, said pump being connected between the washing tower and the cooler for, on the one hand, sucking said gas produced by the reactor so as to allow it to be discharged into an accessory with a controlled flow rate, and secondly, to extract by centrifugation a portion of water of said gas capable of containing residual particles, said pump comprising a housing, inside which is rotatably mounted a rotor provided with vanes, a suction line for said gas, a delivery line for said gas, the rotation of the vanes causing suction and discharge of said gas respectively through 3037259 said conduits, an annular chamber being delimited in the housing, outside the blades, so that the rotation of said blades causes the p urification of said gas sucked by centrifugation in said annular chamber, a portion of the particles, and a liquid portion, that said gas contains. The vane pump is able to dehydrate, purify the synthesis gas, biogas, including soot containing silica, sulfur, cold tars, before returning to the cooler. As it is a synthesis gas requiring an oxygen supply, the operation of the vane pump makes it possible to regulate the operation of the tower 10 for producing said synthesis gas. The emergency stop of the operation of the synthesis gas production tower can be obtained relatively quickly by controlling the stopping of the vane pump. According to an additional characteristic of the invention, the system for producing and purifying said gas comprises at least one filter interposed between the reactor and the washing tower, said filter comprising an elongate envelope disposed along a vertical or quasi-vertical axis, the casing being connected in its lower part to an inlet connection of said gas and in its upper part to an outlet connection of said gas, so that it can circulate upwards in said casing, the heavy particles contained in said filter, including hot tars, cold tars, ash, soot, carbon, being partially retained by settling down under the effect of gravity, in the bottom of said envelope. Larger particles are retained by gravitational deposition inside this or these filters. A cogeneration plant is also part of the invention. The cogeneration plant includes a system for producing and purifying a synthesis gas described above. It further comprises a heat engine or a gas turbine.

The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being given in connection with the attached drawings, among which: 3037259 4 FIG. 1 is a diagram of a cogeneration plant including a synthesis gas purification system "syngas" produced in a reactor according to the invention, FIG. 2 is a cross-sectional view of a pump with centrifugal extraction and centrifugation blades of the syngas according to the invention and FIG. 3 shows a top view of the vane pump without its cap according to the invention. The CHP plant 100 shown in FIG. 1 is intended to produce two types of energy: electricity and heat. For this purpose, it uses syngaz Sg produced from the combustion of vegetable waste coming, for example, from a sawmill. Waste, such as wood chips, from woodworking or other plant materials such as maize cobs, is used to make syngas by using a gasification process derived from the Imbert process. Vegetable waste is introduced into the upper part of a gasification reactor and is here in the form of a tower T. Air A is introduced laterally into the tower T to supply the oxygen necessary for Syngas formation.

Syngaz Sg is produced according to a so-called "gasification" process: The gasification of wood involves two main stages, pyrolysis (at a temperature of between 600 and 700 ° C.) and gasification (up to 1300 ° C.). . At these temperatures, and with a limited amount of oxygen, the hydrocarbon substrates do not enter a conventional combustion, as can be seen in a chimney or wood stove: CxHy + (x + y / 2) 02 xCO2 + y / 2 H2O (complete combustion), but perform pyrolysis followed by gasification. During the pyrolysis, we obtain: 1. A stage of drying of the wood (for a temperature up to 120 ° C). 2. Slow decomposition of wood, mainly hemicellulose and cellulose, with production of gaseous compounds such as acetic acid or methanol; (for a temperature between 120 ° C and 250 ° C). 3. At a temperature above 250 ° C, the gases produced change composition to form: H2, CO and CH4. The production of aromatic condensable compounds from the decomposition of lignin is also observed. 4. At a temperature above 320 ° C, the heat is sufficient to ignite the gaseous mixture in air. In parallel, we observe the formation of charcoal, from lignin. Then, during the gasification, the remaining solid material consists mainly of coal, symbolized by the carbon element (C): C + 1/202 CO (partial oxidation) C ± H20 CO ± H2 (Water reduction by coal or Water Gas Reaction in English) C + CO2 <-> 2C0 (Boudouard equilibrium - reduction) 10 C + 2H2 CH4 (Methanation, especially at high pressure) The following reaction is favored at lower temperature (lower temperature) 300 ° C). It makes it possible to enrich the mixture with dihydrogen. CO + H20 <-> CO2 + H2 (Water-Gas Shift) We can note that the transformation of the water present in the wood is an important factor. The gas thus obtained at the reaction outlet is highly enriched in H2 hydrogen and whose share is greater than 10% and therefore has a high explosive power used to operate a heat engine or a gas turbine.

The tower T is connected to a line C through which the syngas produced Sg is collected. It is transported through at least one filter F to be filtered and cleaned of the heavier carbon or mineral particles. Three filters Fi, F2, F3 are implemented in this FIG. 1. They are connected via pipes C.

These filters are part of the syngas purification system. The syngas Sg is admitted in the lower part of each filter F and leaves at its upper part. Each filter F is composed of an elongated envelope formed of a cylinder or a polygon disposed along a vertical or quasi-vertical axis and in which the syngas flows upwards. The heavy particles, especially hot tars, cold tars, ashes, soot but especially carbon, are partly retained in these filters by settling. They fall back under the effect of gravity, in the bottom of the cylinders to sediment. A hatch disposed in the lower part or preferably in the bottom wall 3037259 6 of each cylinder can open said bottom to remove these residues, in periods of non-use of the filters. At the outlet of the last filter F3, syngaz Sg is admitted, via a line C, into a countercurrent washing tower Tlc constituting the syngas purification system. This consists of an envelope B, in the form of a cylindrical tube in this FIG. 1 disposed along a vertical or near vertical axis, and inside which is disposed a worm screw V. The worm V is mounted without play or virtually without play inside the cylindrical tube. The tube B is closed at its upper end while being connected to an inlet pipe Cr 10 of washing and cooling liquid, while its lower end is open and is immersed in a recovery tank and Bc decantation. The liquid flows by gravity, so down on the surface of the worm V and is recovered in the tray Bc. The intake of the syngas in the counter-current washing tower Tlc is made in its lower part, for example just above the upper level of the tray Bc, 15 while its output is carried out at its upper part. Thus, the syngas flows upstream on the worm V, against the current of the liquid admitted vertically into the tube and from top to bottom, and which by its spurt forms splashes, foam, droplets on the wall of said worm, and will partly trap light particles, including hot tars, fine soot, sulfur compounds, nitrogen, phosphorus, to drive them in the tank Bc where they will decant. The bin Bc comprises for this purpose several settling compartments that fill by overflow. The formation of the droplets can still, at least in part, be carried out by the updraft of the syngas, which by its speed will spray the liquid.

This countercurrent exchange will also allow the liquid to capture the calories contained in the syngas which thus emerges from the countercurrent washing tower Tlc, purified and cooled. The liquid is preferably water. In an alternative embodiment not shown, the worm is replaced by perforated plates, arranged horizontally in the casing and without play or virtually no clearance. The washing liquid flows through the perforations and forms droplets which trap the particles contained in the syngas that goes back through said perforations. In section, the envelope has any geometry, for example polygonal or circular and the geometry of the plates is adapted accordingly. The wash liquid is preferably sprayed over substantially the entire surface of the top plate. A large amount of droplets are formed in the perforations. The countercurrent washing tower Tlc captures about half or more than half of the residual particles contained in the syngas.

The liquid admitted into the countercurrent washing tower Tlc comes from a settling compartment and preferably from the last compartment of the tank Bc. It is pumped to be admitted into the countercurrent washing tower. The liquid contained in the different compartments contains a low concentration of NH4 at the end of the cycle. It is replaced periodically.

The syngas produced in tower T still contains, in spite of the presence of filters F, the countercurrent washing tower Tlc, soot containing particles such as silica and sulfur (hydrogen sulphide). , a liquid part containing cold tars, and which are still likely to foul, corrode and wear prematurely said engine.

In the invention, a blade pump Pa interposed in the circulation circuit of the syngas is used before feeding a heat engine Mt via a cooler R. The blade pump Pa is preferably disposed at the outlet the countercurrent washing tower Tlc and upstream of the cooler R to not obstruct it. It is an additional means constituting the syngas purification system. The paddle pump Pa is rotated by means of a motor M, such as an electric motor, on the one hand, to suck the syngas and to remove it by centrifuging the particles and the liquid part in the form droplets it contains and, secondly, the repress in the heat engine Mt with a regulated flow 25 and slight overpressure of the order of 4000 to 5000 Pa. Indeed, it is the depression caused by the operation of the paddle pump Pa which causes the suction of the air A and the oxygen it contains in the tower T to maintain the gasification reactions implemented in said tower. The operation of the paddle pump Pa thus serves to modulate the production of syngas in quantity and composition. The slight overpressure generated by the operation of the paddle pump Pa increases the efficiency of the engine. The syngas then circulates in the cooler R where its temperature is further lowered and controlled. The syngas is used to operate the thermal engine Mt, such as a relatively high displacement internal combustion engine, coupled to a generator G of electric current I, such as an alternator. In an alternative embodiment, not shown, the heat engine consists of a gas turbine also coupled to an electric power generator.

5 The cogeneration plant 100 still produces Co calories, in particular peddled by water heated by circulating at the base of the tower T, around the cylinders of the heat engine Mt, hot air from the room in which is installed the engine. This energy can be used to heat offices, industrial premises, to dry various products, such as agricultural products. Hot gas Gc is also produced by the heat released by the exhaust manifold of the heat engine Mt, to be used, for example in a drying unit of materials such as wood in the form of platelets. In FIG. 2, the blade pump Pa is shown in its operating position. It consists of a casing Ct of cylindrical shape and in which is housed a rotor Rt rotatably mounted inside thereof, a connection cap Cr. The casing Ct has a cylindrical opening Oc crossing the upper one, Fel, with its two end faces Fel, Fe2, and through which the rotor Rt can be mounted in said casing. The cap Cr is formed of a ring bearing on the end face 20 Fel and around the cylindrical opening Oc, a cylindrical chamber Cc opening an edge through said crown and the other edge is closed by a circular wall Pc. A suction pipe Cp of the syngas crosses at its center the circular wall Pc and a discharge pipe Cf passes through said circular wall, offset from the suction pipe Cp. The suction pipe Cp is connected to the outlet of the countercurrent washing tower Tlc, while the discharge pipe Cf is connected, via the cooler R, to the supply manifold of the heat engine Mt. In operation, the heat engine drives the generator which produces electric current which can advantageously be used in a plant or injected into an electrical network. The flow direction of the syngas in the paddle pump Pa during its operation is indicated by the arrows 51 and S2 and correspond respectively to the suction and discharge thereof.

The rotor Rt consists of a rotary drive shaft Ar integral with a disk Ds on which vanes Ab are formed. The drive shaft Ar is held in a bearing Pl integral with the lower face of the rotor. closed end Fe2 of the casing Ct, except at its center for the passage of the shaft Ar.

The length of the blades Ab is such that an annular chamber Ca is formed at the periphery of the casing Ct between the outer edge of the vanes and the peripheral edge of the casing. This annular chamber Ca extends lower than the lower end face and closed Fe2 of the casing Ct, in the normal operating position of the paddle pump Pa, in an annular gutter Ga.

Each blade Ab consists of a flat plate which extends perpendicularly from the disk Ds. In Figs. 2 and 3, each blade Ab is preferably arranged radially, that is to say that its median plane is secant to the axis of the disk drive shaft Ar Ds. This gives a relatively low discharge pressure in the engine. In FIG. 2, the suction pipe Cp extends inside the cylindrical chamber Cc to the vicinity of the blades Ab, to convey the syngas to the center of the rotor Rt and to define a discharge chamber C1 in the chamber cylindrical Cc, around the suction pipe Cp and into which the discharge pipe Cf the inner diameter of the discharge chamber C1 is smaller than the diameter of evolution of the blades Ab, so that the particles and the centrifuged droplets in the annular chamber Ca can no longer return to the delivery chamber C1. In FIG. 1, the rotor drive is effected by motor M. Said motor drives the rotor drive shaft via pulley and belt transmission (s) to provide flexibility and quiet operation. The cooler R which is connected downstream of the paddle pump Pa is intended to lower the temperature of the syngas dehumidified and purified to increase its efficiency PCI (lower calorific value). It is formed of an envelope 30 containing a heat exchanger. This heat exchanger comprises hollow plates and inside which can circulate a coolant, such as water flowing in a loop in a refrigerating unit Gf. The syngas circulating around these plates can then be cooled.

The cooler R, because of its relatively low internal temperature in operation, of the order of a few degrees Celsius, for example 4 ° C as an indication, will force the residual cold tars contained in the syngas to condense on the cold plates of the heat exchanger. The residual traces of water are also condensed, causing the remaining soot not removed in the various purification means connected upstream. He thus participates in purifying the syngas. The syngas leaving the exchanger, cooled out spring but also purified again. The cooler R is connected, via a pipe C, to a compartment of the tank Bc for recovery and decantation and preferably the first, for discharging therein, the condensates produced in the cooler R and containing cold tars. The operation of the system for producing and purifying a synthesis gas present in the cogeneration plant will now be described.

The ignition of the gasification tower is initiated, then it is fed continuously with vegetable waste. Syngaz Sg is produced. The motor M is turned on and the paddle pump Pa sucks the syngas produced. It is sucked upstream of the blade pump Pa through the pipes C and the filter (s) F and through the countercurrent washing tower Tlc. Since the pressure of the syngas is negative with respect to atmospheric pressure, a leak, for example at a connection, has the effect of introducing air into the pipes, which eliminates the risk of accidental ignition of the air. the installation or the pollution of the outside air in the environment of the installation. Arriving in the paddle pump Pa, the syngas Sg aspirated is centrifuged by the blades Ab, the liquid droplets, the particles it contains, of greater density than that of the gas, are projected into the annular chamber Ca, then fall by gravity into the underlying annular gutter Ga, following the directions of the arrows S3 and S4. This relatively liquid material is evacuated by gravity through a drain pipe Cn which is connected from below to the annular groove Ga. The pipe Cn opens into a compartment of the settling tank Bc A restrictor Rs, that is that is to say a passage of reduced section is disposed in the pipe Cn, to limit the loss of syngaz may be released to the atmosphere through said pipe. An intermittent valve may replace or supplement the restrictor to cyclically purge the line Cn. Note that in operation, the pressure P + measured in the discharge chamber C1 is higher than that P- measured in the line. Suction 5 Cp, so that the particles of the gas admitted in the pump Pa can not in principle be introduced into said discharge chamber C1. In FIG. 1, the purified gaseous portion of the syngas, denoted Sgp, is discharged through the discharge pipe Cf. The temperature of the purified syngas is then lowered and regulated through the cooler R. The syngas is then admitted to the heat engine Mt with a weak suppression, of the order of a few tens of millibars. The supply of the thermal engine Mt which operates at constant speed is thus regulated by the speed of rotation of the paddle pump Pa. The exhaust gases produced by the engine do not contain nitrogen oxide or sulfur, and very little methane (<0.2%).

Stopping the operation of the heat engine is simply implemented by stopping the operation of the drive motor of the vane pump, which makes it possible to secure the operation of the cogeneration plant. The air is no longer allowed in the tower, the gasification reactions can be stopped in a relatively short time, of the order of fifteen minutes. The safety devices of which the syngas production and purification system is provided make it possible to act on stopping the operation of the vane pump. The blade pump can still be used, as such, to purify a gas other than syngas. The system for the production and purification of syngas produced by a gasification reactor provides a great operational durability of the heat engine, of the turbine, which it supplies with syngas, by reducing its wear, by eliminating the syngas from the main impurities. that it contains, and in particular the soot and tars, by withdrawing its part in water and cooling it. The operation of the heat engine is regulated by the flow rate of the 30-blade pump. The cogeneration plant, object of features of the invention has a high efficiency, of the order of 90%. It guarantees in principle an energy autonomy when it is associated with a syngas production reactor using organic plant material.

3037259 12 It allows the recycling of products from the wood industry. It offers additional revenue through the sale of electricity. It does not use waste that is difficult to manage and does not pollute the water. Its manufacturing cost is relatively low.

The invention described above refers to the use of syngas, which is a gas produced by a physicochemical action unrelated to a living being. In an embodiment variant not shown, the production and purification system processes biogas resulting from a biological metabolization of the carbon compounds, for example from a reactor constituting an anaerobic digestion plant. The anaerobic digestion being carried out in the absence of oxygen supply, stopping the operation of the vane pump is no longer able to interrupt the production of biogas in the methanation reactor.

Claims (7)

CLAIMS1) System for producing and purifying a synthesis gas or a biogas, comprising a reactor (T) designed to produce said gas, a washing tower of said gas, of the countercurrent type (Tic) comprising a envelope provided with an inlet of a washing liquid, an inlet and an outlet of said gas arranged so as to allow a circulation of said gas against the flow of the washing liquid circulation, the washing tower to countercurrent device (Tic) comprising means designed to form droplets with the flow of the washing liquid so that they can trap particles contained in said gas, characterized in that it comprises a cooler (R) connected downstream of said scrubber, said cooler comprising means for lowering the temperature of said gas to increase is PCI (lower calorific value) and condense, on the one hand, residual cold tars and, on the other hand, water residual meadows in said gas, still containing soot. 2) System for producing and purifying a synthesis gas or a biogas according to claim 1, characterized in that the means designed to form droplets comprises a worm (V) disposed in its operating position along a vertical or near-vertical axis, with no clearance or practically no clearance within said casing, the arrival of the washing liquid being positioned in the upper part of the casing (B), so that the droplets can to form while running down the wall of the worm (V). 3) System for producing and purifying a synthesis gas or a biogas according to claim 1, characterized in that the means designed to form droplets comprises perforated plates, arranged horizontally in their operating position, without play. or practically without clearance within said casing, the arrival of the washing liquid being positioned in the upper part of the casing (B) so that it can flow through the perforations and form droplets so trapping particles contained in said gas as it rises through said perforations. 4) System for producing and purifying syngas or a biogas according to claim 2 or 3, characterized in that the lower part of the casing (B) is open and immersed in a compartment of a tank of recovery and decantation (Bc) of the washing liquid, said liquid being captured in another compartment for reuse by pumping in said wash tower. 5) System for producing and purifying a synthesis gas or biogas according to any one of the preceding claims, characterized in that it comprises a vane pump (Pa) coupled to a motor (M) capable of rotating it, said pump being connected between the washing tower (Tic) and the cooler (R) in order firstly to suck up said gas produced by the reactor (T) in order to allow it to be forced back into the an accessory with a controlled flow rate, and secondly, for extracting by centrifugation a portion of water of said gas capable of containing residual particles, said pump comprising a housing (Ct), inside which is rotatably mounted a rotor (Rt) provided with blades (Ab), a suction pipe (Cp) of said gas, a discharge pipe (Cf) of said gas, the rotation of the blades (Ab) causing the suction and the discharge of said gas respectively through said lines (Cp, Cf), an annular chamber (Ca) is nt delimited in the casing (Ct), outside the blades (Ab), so that the rotation of said blades causes the purification of said gas sucked by centrifugation in said annular chamber, a part of the particles, and a liquid part, that said gas contains. 6) System for producing and purifying a synthesis gas or a biogas according to any one of the preceding claims, characterized in that it comprises at least one filter (F) interposed between the reactor (T) and the washing tower (Tic), said filter comprising an elongate envelope disposed along a vertical or quasi-vertical axis, the envelope being connected in its lower part to an intake connection of said gas and in its upper part to a connection of output of said gas, so that it can flow upwardly in said envelope, the heavy particles contained in said filter, including hot tars, cold tars, ash, soot, carbon, being partly retained by decantation by falling under the effect of gravity, in the bottom of said envelope. 7) Installation (100) of cogeneration, characterized in that it includes a system for producing and purifying a synthesis gas or a biogas according to any one of the preceding claims and in that it comprises a heat engine (Mt) or a gas turbine.