METHOD FOR GASIFICATION OF CARBONACEOUS FEEDSTOCK AND DEVICE FOR IMPLEMENTING SAME

Abstract

The invention relates to the field of gasification of a carbonaceous feedstock and can be used in the chemical, petrochemical, coke-gas and energy industries. A method for gasification of a carbonaceous feedstock comprises partial oxidation of the carbonaceous feedstock in an oxidation chamber in a mixture of oxygen-containing gas and water vapour in a partial oxidation channel, which is mounted coaxially in the vertical oxidation chamber. The water vapour for the partial oxidation of the carbonaceous feedstock is supplied at the input and output of the vertical oxidation chamber of a combustion chamber. A gas producer comprises a housing, a burner device, a vertical oxidation chamber, manifolds for supplying carbonaceous feedstock, water vapour and oxygen-containing gas, a pipe for discharging gasification products, a slag removal chamber, and also a partial oxidation channel, which is arranged coaxially in the vertical oxidation chamber and is attached to an upper internal part of the housing, in which the burner device is installed. What is achieved is the production of producer gas with an elevated concentration of hydrogen.

Claims

1. A method of gasification of carbonaceous feedstock, including partial oxidation of carbonaceous feedstock in an oxidation chamber in a mixture of oxygen-containing gas and water vapour characterized in that partial oxidation is carried out in a partial oxidation channel which is mounted coaxially in a vertical oxidation chamber, and water vapour supply for partial oxidation of carbonaceous feedstock is carried out at the input and output of the partial oxidation channel of the oxidation chamber.

2. The method, as claimed in claim 1, characterized in that partial oxidation is carried out in the flow of the oxygen-containing gas and water vapour mixture in the partial oxidation channel of the oxidation chamber at a temperature of 900-1100° C. which is maintained by changing the volume of vapour at the output of the partial oxidation channel.

3. The method as claimed in claim 1 characterized in that at the output of the partial oxidation channel of the oxidation chamber the temperature is maintained within 800-1000° C. which is provided by changing the volume of vapour at the output of the partial oxidation channel.

4. The method as claimed in claim 1 characterized in that the ignition of the carbonaceous feedstock and vapour-oxygen mixture and maintenance of their stable combustion is carried out by feeding the combustion products to the input of the partial oxidation channel from the burner device mounted coaxially in the partial oxidation channel.

5. The method as claimed in claim 1 characterized in that the residence time of combustion products in the oxidation channel is longer than the biggest feedstock particle's combustion time.

6. The method as claimed in claim 1 characterized in that the size dimensions of the partial oxidation channel are chosen based on the ratio:
L≥(4*G*T.sub.b)/(π*ρ(t.sub.0)*D.sup.2), where L—the length of the partial oxidation channel; D—the diameter of the partial oxidation channel; G—the mass arrival of oxidation products into the partial oxidation channel; T.sub.b—the combustion temperature of the biggest particle of carbonaceous feedstock; t.sub.0—the calculated temperature of oxidation products in the partial oxidation channel; ρ(t.sub.0)—the calculated density of oxidation products in the partial oxidation channel.

7. The method as claimed in claim 1 characterized in that solid fuels in the form of coal, brown coal, peat, wood, coke, soot or gaseous and liquid fuels, or mixtures thereof, are used as carbonaceous feedstock.

8. A gas producer comprising a housing, a burner device, a vertical oxidation chamber, manifolds for supplying carbonaceous feedstock, water vapour and oxygen-containing gas, a pipe for discharging gasification products, a slag removal chamber, is peculiar for the fact that the partial oxidation channel is additionally introduced into it. The channel is arranged coaxially in the vertical oxidation chamber and is attached to the upper internal part of the housing in which the burner device is installed.

9. The gas producer as claimed in claim 1 characterized in that the upper part of the housing is made in the form of a removable lid, into which the burner device is installed.

10. The gas producer as claimed in claim 1 characterized in that the pipe for discharge of gasification products is installed in the side piece of the gas producer housing closer to the upper part of the gas producer.

11. The gas producer as claimed in claim 1 characterized in that it contains upper and lower vapour manifolds made in the form of hollow rings connected by downpipes, the axes of which are parallel to the axis of the outer housing, though the upper manifold is installed on the outer part of the gas producer lid, the downpipes are installed on the outer side of the partial oxidation channel, and the lower vapour manifold is located at the output of the oxidation channel and is provided with vents to send vapour into the flow of partial oxidation products.

12. The gas producer as claimed in claim 1 characterized in that the burner device is made in the form of a diffusion burner equipped with annular channels arranged coaxially around the diffusion burner and made with the possibility of supplying oxygen-containing gas, carbonaceous feedstock and water vapour to the annular channels.

13. The gas producer as claimed in claim 1 characterized in that the inner walls of the oxidation chamber are made in the form of a coil, the upper output of which is connected to the upper vapour manifold through the hot vapour distribution unit, and the lower output is connected to an external water vapour generator.

14. The gas producer as claimed in claim 1 characterized in that the inner walls of the oxidation chamber are made in the form of coaxially arranged toroid-shaped containers made with the possibility of supplying water vapour from below the oxidation chamber to the lid of the gas producer.

15. The gas producer as claimed in claim 1 characterized in that the partial oxidation channel is made with external thermal insulation.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0068] The present method and device for gasification of carbonaceous feedstock are illustrated by drawings, where:

[0069] FIG. 1 shows the overall scheme of the gas producer for gasification of carbonaceous feedstock;

[0070] FIG. 2 shows the section scheme of the gas producer;

[0071] FIG. 3 shows the scheme of the burner device of the gas producer;

[0072] FIG. 4 shows the schematic diagram of the gas producer with a coil for heating vapour and cooling the housing wall; and

[0073] FIG. 5 shows the schematic diagram of the gas producer with a set of toroid-shaped containers for heating vapour and cooling the wall of the gas producer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0074] The proposed gas producer for gasification of carbonaceous feedstock contains a housing 1, an oxidation chamber 2, a housing lid 3 (FIG. 1), a burner device 4 (FIG. 4) with a diffusion burner 7, oxygen supply pipes 5 and a mixture of water vapour and carbonaceous feedstock 6, a pipe 8 for discharging generator gases, a partial oxidation channel 9 with thermal insulation 10, with a vapour supply manifold 12 into the space at the output of the oxidation channel 9, as well as downpipes 13, (FIG. 2) supplying vapour from the upper vapour manifold 14 to the vapour supply manifold 12. A slag removal chamber 11 is installed in the lower part of the housing.

[0075] FIG. 2 presents the A-A section (FIG. 1) of the gas producer, which shows a variant of arrangement of the vapour supply vants 15 in the vapour supply manifold 12. FIG. 3 shows a diagram of the burner device 4 with a built-in diffusion burner 7 with an air supply channel 16, with a fuel supply channel 17 (for example, fuel oil or gas fuel), with ignition electrodes 18, a mixing diffuser 19, with an oxygen supply channel 20 and a vapour supply channel 21. FIG. 4 shows a diagram of the gas producer according to FIG. 1, supplemented by a coil 22 for heating vapour and cooling the thermal insulation of the wall of the gas producer housing 1, a vapour input pipe 23 into the coil 22, a vapour distribution unit 24 into the vapour mixing unit with carbonaceous feedstock 25 and into the manifold 14, a coal supply pipe 26 into the mixing unit 25. FIG. 5 shows a diagram of the gas producer according to FIG. 1, supplemented by toroid-shape tanks 27 for heating vapour and cooling the thermal insulation of the wall of the gas producer housing 1, a vapour input pipe 23 into the coil 22, a vapour distribution unit 24 into the vapour mixing unit with carbonaceous feedstock 25 and into the manifold 14, a coal supply pipe 26, U-tubes 28 connecting toroid-shaped containers 27 among themselves.

[0076] The proposed method and gas producer work as follows.

[0077] Wet vapour enters the coil 22 through the nozzle 23 (FIG. 4) where it is heated by the outgoing producer gases through the pipe 8 discharging producer gases. Through the coil 22, vapour enters the vapour distribution node 24, where it is divided into 2 flows. Part of the vapour enters the mixing unit 25, where the vapour picks up fine carbonaceous feedstock for example, coal dust coming through the nozzle 26, and the resulting coal-vapour mixture enters through the nozzle 6 (an ejection device or a sluice (not shown in the drawing)) into the burner device. The burner device is a combined burner 4 (FIG. 3) in the center of which there is a diffusion burner 7 for burning liquid or gaseous fuel in the air. The combustion products of the diffusion burner with a temperature of 1500-2000° C. create the centre of the gas stream whirled by the mixing diffuser 19 of the burner 7 mixing the oxygen flows entering through the nozzle 5 into the channel 20 and the vapour-coal mixture entering through the nozzle 6 into the channel 21.

[0078] In order to obtain the maximum possible amount of hydrogen during gasification of hydrocarbon particles in a parallel flow it is essential to solve several complex tasks, production of producer gas by an endothermic chemical reaction in particular

C+H2O=CO+H2−31700 kcal  (2)

with a significant loss of thermal energy simultaneously with burning up part of carbonaceous particles in oxygen (in the total flow of vapour and oxygen-containing gas) and maintaining the process temperature in the range of 900-1100° C.

[0079] In order to obtain the required result it is necessary to perform the process at low pressure (for instance, the pressure close to the atmospheric one), then, according to the Le Chatelier principle, the process according to (2) will be shifted to the right. The principle of Le Chatelier establishes that in case of an outside impact on a system in a state of equilibrium by means of a change in one of the factors determining the equilibrium, the direction of the process which weakens such impact in the system increases. Since the reaction (2) produces 2 moles of gas (CO and H2 instead of one mole of H2O) with an increase in pressure as a result of an increase in the volume of gases, then by decreasing the pressure in the reactor, it is possible to force the system to return to equilibrium, accelerating the reaction (2) with production of CO and H2 gases. Conversely, when the pressure in the reactor increases the pressure in the system decreases due to slowing down reaction (2). Technically, this means that it is necessary to prevent an increase in pressure during oxidation process, i.e. it is necessary to prevent an increase in gas dynamic resistances to the movement of the gas flow. Consequently, the design of the channels through which the oxidation products move should not have sharp constrictions and the combustion of carbonaceous particles should preferably be carried out during movement in the flow and not in a closed chamber.

[0080] To maintain the necessary temperature, it is rational to burn a part of carbon in oxygen according to the reaction

C+O2=CO2+94300 kcal  (3)

which happens almost instantly at 1000° C., but when the temperature decreases its speed decreases too [1, p. 24]. However, to maintain the reaction (2) a significant amount of water vapour is used and it takes away thermal power and the heat input from the reaction (3) occurs gradually while the particles burn up. Therefore, it is rational to divide the water vapour into 2 parts where the first part of the vapour enters through the burner device, and the second part used for partial oxidation of feedstock enters the flow of partial oxidation products at the output of the oxidation channel after burning up of carbonaceous feedstock into the space between the vertical wall of the gas producer housing and the wall of the oxidation channel. In addition, the division of water vapour supply makes it possible to conduct a controlled reaction at the output of the oxidation channel

CO+H2O=CO2+H2+10300 kcal  according to formula (1)

with an increase in hydrogen in producer gas. As the reaction (1) is exothermic, the temperature increase will lead to the shift of equilibrium to the left (i.e. towards the feedstock) according to the Le Chatelier principle. However, for this reaction the limit is the temperature of 1000° C. (it is proved by the equilibrium constant dynamics [3, p. 102] and experimental data [2, p. 30]). It means that the supply of water vapour at the output of the oxidation channel will allow the reaction (1) to develop and reduce the gases temperature to 700-800° C. preventing it from rising above 900-1000° C. Therefore, it is optimal to maintain the temperature at the output of the oxidation channel in the range of 800-1000° C.

[0081] To complete the oxidation-reduction reactions (2) in the partial oxidation channel, its size dimensions (diameter and length) must ensure that the burning particle stays in the channel at least for as long as its burnup time (significantly increasing thermal efficiency of the process) which critically depends on the size of the burned particle. For example, an anthracite particle with a diameter of 100 microns burns up in oxygen for 7.1 seconds, but a particle with a diameter of 50 microns burns up for 0.413 seconds [3, p. 210]. Knowing the particle size of the gasified feedstock and its hourly consumption, it is easy to calculate the size dimensions of the oxidation channel.

[0082] The most important condition for the stable operation of a gas producer with particle in flow gasification is stable ignition and combustion in the resulting two-phase flow, where combustion occurs both on the surface of the particle and in the gas phase. For the stability of the process it is important for the flame propagation velocity to be higher than the two-phase flow velocity, otherwise the flame will fail and the oxidation process will stop. In well-known gas producers of flow-line gasification including the closest analogue of the “PRENFLO” PDQ this problem is solved in the following way. They increase the combustion rate of coal particles increasing the pressure and temperature of the process by means of increasing the oxygen supply and burning more coal according to reaction (3). In addition, they increase the residence time of particles in the reactor by arranging the burners perpendicular to the flow. What is essential in the design of the prototype is that the increase in pressure in the oxidation chamber is achieved by narrowing at the output of the oxidation chamber in the form of a rocket nozzle which innately requires liquid slag removal and high temperatures because otherwise the narrowing channel will be quickly slagged.

[0083] In the proposed device, this problem is solved differently. In order to obtain a permanent ignition source and stabilize the partial oxidation process the burner device, preferably embedded in the lid of the gas producer, is a combined diffusion burner in the center of which along the axis the actual diffusion burner for burning gaseous or liquid fuel is embedded. It is equipped with annular channels arranged coaxially around the built-in diffusion burner designed with the possibility of supplying oxygen-containing gas, carbonaceous feedstock and water vapour to these annular channels. It means the source of additional heat for igniting the mixture and maintaining a stable oxidation process in the proposed method is the heat of the combustion products of liquid or gaseous fuel fed along the flow of the reacting oxygen vapour mixture and carbonaceous feedstock. Such a scheme of combustion process allows obtaining a stable ignition of the two-phase flow and maintaining its combustion until there is stable heat generation according to reaction (3) and compensating for heat losses in the reaction of carbon and carbon monoxide with water vapour. Thermodynamic calculations of variants of such process show that the power of such a built-in burner comprises 10-25% of the power of the carbon burned by the reaction (3) and it is sufficient for organizing a stable process with an inflow temperature not exceeding 1100° C.

[0084] Thus, the proposed method allows for stable ignition and combustion in the resulting two-phase flow both on the surface of the particle and in the gas phase due to the stable supply of additional thermal energy from combustion products coming from an integrated burner device in which liquid or gaseous fuel is burned. The combustion products from the burner device enter the partial oxidation channel along the axis of the channel, mixing with carbonaceous feedstock and oxygen vapour mixture.

[0085] Adjustment of flow rates of vapour, coal and oxygen in the oxidation channel 9 (FIG. 4) helps to set the temperature of 900-1100° C. monitored by thermal sensors (not shown in the drawings). The second part of the vapour from the distribution unit 25 through the pipes 13 enters the vapour supply manifold 12 and through the vents 15 is fed into the space at the output of the oxidation channel 9, where carbon monoxide is oxidized to carbon dioxide to produce hydrogen. The calculated amount of vapour should in total provide cooling to a temperature not higher than 900-1000° C. to prevent reverse reactions according to formula (1). The resulting producer gases are fed through the producer gas output pipe 8 for cooling and purification and further processing (for example, for organic synthesis or to a membrane separator with further supply of the resulting hydrogen for coal hydrogenation). The bulk of the slag and ash formed as a result of coal combustion enters the slag removal chamber 11. They are disposed of by the system afterwards.

[0086] Description of a Real Case [0087] 1. To produce hydrogen for the coal hydrogenation plant, a prototype gas producer was built according to the scheme of FIG. 5 for partial oxidation of coal. The characteristics of raw coal type were determined: average ash content—12%; moister content—8%; carbon content in the organic matter of coal (COM)—77%; hydrogen content in COM—5%. The raw coal was crushed, dried in a drum dryer and finely ground on a crusher with a particle size of less than 100 microns (80% of particles with a size of less than 50 microns). The consumption of dry coal was 1 ton per hour. [0088] 2. An oxygen extraction unit with a capacity of 300 m.sup.3 per hour or 390 kg per hour was chosen as an oxygen source. [0089] 3. The volume of the amount of water for the oxidation of coal and the proportions of the distribution of vapour volumes through the burner and manifold at the output of the oxidation channel were selected from thermodynamic calculations of thermal balances of chemical oxidation and reduction reactions. As a diffusion burner built into the burner device a fuel oil burner with a thermal capacity of 200 kW was used. The burner can burn 20 kg of fuel oil in 20×10.8=216 m.sup.3/hour of air or 276.5 kg/hour of air during a 60-minute period. [0090] 4. Up to 150 kg of vapour per hour were supplied to the input of the partial oxidation channel through the burner device. The calculated temperature of the combustion products at the output of the partial oxidation channel was 952° C. which fits into the optimal temperature limit of 900-1100° C. [0091] 5. Vapour supply from the manifold (pos. 12, FIG. 5) was carried out through 3 rows of vents with a spray angle between the rows of vents equal to 120°. The volume of vapour coming through the manifold (pos. 12 FIG. 5) was 250-300 kg per hour.

[0092] The regulation of vapour volumes entering through the burner device and through the manifold was carried out according to the data of the three temperature sensors built in at the output of the oxidation channel and data from temperature sensors built into the annular gap between the oxidation channel and the gas producer housing 20 cm above the output of the oxidation channel (3 pcs).

[0093] The selection of size dimensions of the partial oxidation channel (pos. 9, FIG. 6) was determined by the residence time of combustion products in the oxidation channel. This value should preferably be longer than the combustion time of the biggest particle of the feedstock. Coal dust with particle size of up to 50 microns (80%) and up to 80-90 microns (20%) was fed to the gas producer. The combustion time of a particle with the size of 50 microns was 0.41 seconds, and with the size of 100 microns—7 seconds. Under the condition of the complete reaction of coal in the oxygen vapour flow about 826 liters of gases were obtained at a temperature of 1000° C. per second. When selecting the diameter for the partial oxidation channel of 0.85 meters and the length of the oxidation chamber of 6 meters, the residence time of the particles in the oxidation chamber was 7.9 seconds, which exceeded the theoretical combustion time of a coal particle of the biggest size.

[0094] The composition of gases (dry) under the mode with maximum hydrogen yield averaged in volume %:

[0095] H2—52.3%,

[0096] N2—10.0%,

[0097] CO—12.4%,

[0098] CO2—25.3%.

[0099] Oxygen consumption per 1 ton of dry coal was 300 m.sup.3 per hour, vapour consumption per 1 ton of dry coal was 370-430 kg.

[0100] From the information source [4, p. 31] describing the prototype installation according to the Shell-Coppers technology, the following average indicators are revealed:

[0101] H2—25.6%

[0102] CO—65.6%

[0103] CO2—0.8%

[0104] CH4—8.0%

[0105] The oxygen consumption was 644 m.sup.3 per ton of dry coal, and the vapour consumption was only about 100 kg per ton of dry coal. It is obvious that the hydrogen yield according to the proposed method and device is 2 times higher than that of the prototype, oxygen consumption is 2 times lower. The process temperature is lower (1100° C.) too, compared to the prototype in which the process takes place at a temperature of 1400-1600° C. In the proposed device the water vapour consumption is almost 4 times higher, but the elevated hydrogen yield is precisely determined by decomposition of water.

[0106] The given example of a specific implementation of the claimed method and device for its implementation shows that in the installation of the proposed gas producer, the results obtained on the hydrogen yield significantly exceed the hydrogen yield indicators compared to the prototype. At the same time, the total consumption of water vapour for partial oxidation of coal was 370-430 kg per 1 ton of coal. Oxygen consumption was 300 m.sup.3 per ton of coal. The total yield of hydrogen was about 65 kg per hour, while in the prototype it is about 32 kg per hour.

[0107] The proposed invention can find wide application in gasification of carbonaceous feedstock, due to ensuring efficient gasification in a parallel flow of carbonaceous feedstock, such as coal, brown coal, peat, wood, coke, soot or other types of gaseous, liquid or solid fuels, or mixtures thereof in order to obtain producer gas with the highest possible hydrogen concentration. At the same time, the required parameters of the produced gas are easily regulated by changing the flow rates of oxygen, vapour, gasified feedstock and the power of the built-in burner.

[0108] The gas producer can be used in the chemical, carbon and petrochemical industries (ammonia, methanol, synthetic fuels, etc.), coke and gas, energy and other related industries for processing carbonaceous feedstock to produce energy and gases. Elevated concentration of hydrogen in the technical gases produced in the proposed device will allow efficiently disposing of heavy oil residues at oil refineries together with producing high-quality motor fuels. For the coal chemical industry the proposed device can become the main basic device for chemical processing of coal. Such device is equally essential both for processing coal by hydrogenation and for obtaining synthesis gas from coal.

REFERENCE LIST

[0109] Alyoshina A. S., Sergeev V. V. Gasification of solid fuel: textbook. St. Petersburg: Publishing House of the Polytechnic University, 2010.—202 p. [0110] Rambush N. E. (translated from English) Gas producers—M.-L.: GONTI, 1939.—413 p. [0111] Pomerantsev V. V., Arefyev K. V. and others. Fundamentals of the practical theory of combustion: textbook for universities—L.: Energoatomizdat, 1986.—312 p. [0112] Schilling G.-D., Bonn B., Kraus U. Coal gasification—Moscow: Nedra, 1986.—175 p.

LIST OF TERMS

[0113] 1. Housing [0114] 2. Oxidation chamber [0115] 3. Gas producer lid [0116] 4. Burner device [0117] 5. Oxygen supply pipe [0118] 6. Pipe for supplying a mixture of water vapour and carbonaceous feedstock [0119] 7. Built-in diffusion burner [0120] 8. Pipe for the discharge of producer gases [0121] 9. Partial oxidation channel [0122] 10. Thermal insulation of the oxidation channel [0123] 11. Slag removal chamber [0124] 12. Lower vapour manifold [0125] 13. Downpipes [0126] 14. Upper vapour manifold [0127] 15. Vapour supply vents in the manifold [0128] 16 Air supply channel [0129] 17. Fuel supply channel [0130] 18. Ignition electrodes [0131] 19. Mixing diffuser [0132] 20. Oxygen supply channel [0133] 21. Vapour supply channel [0134] 22. Vapour heating coil [0135] 23. Vapour input pipe into the coil [0136] 24. Vapour supply distribution unit [0137] 25. Vapour mixing unit with carbonaceous feedstock [0138] 26. Coal supply pipe to the mixing unit [0139] 27. Toroid-shaped containers for vapour heating [0140] 28. U-tubes for connecting toroid-shaped containers