CN114574250B - Method and device for preparing clean synthetic gas by biomass chemical chain gasification - Google Patents

Abstract

The present invention proposes a method and device for producing clean syngas by chemical chain gasification of biomass. The method includes heating and oxidizing biomass by using a circulating solid heat carrier as an oxygen carrier in a moving bed fuel reactor to perform gasification reaction , to generate gaseous products, semi-coke and reduced oxygen carrier; wherein the gaseous products are used in the moving bed reforming reactor to carry out the tar carbon dioxide reforming reaction by using the circulating solid heat carrier as the tar carbon dioxide reforming catalyst to obtain clean synthesis gas. The present invention utilizes a double-cycle oxygen carrier and tar carbon dioxide reforming catalyst to realize in-situ efficient removal of tar, carbon dioxide and dust in biomass gasification and its gaseous products, and simultaneously convert tar and carbon dioxide into hydrogen and carbon monoxide, The yield and quality of synthesis gas are improved, and the utilization rate of atoms and energy is significantly improved. The independent double-cycle operation avoids the contact and mutual pollution between the oxygen carrier and the carbon dioxide reforming catalyst of tar.

Description

A method and device for producing clean syngas by chemical chain gasification of biomass

Technical Field

The invention belongs to the technical field of energy chemical industry, and relates to a method and device for producing clean synthesis gas by chemical chain gasification of biomass.

Background Art

Biomass is abundant, carbon neutral and environmentally friendly, and is currently the only renewable carbon-containing organic energy. The efficient and clean conversion of biomass is an indispensable and important way to solve the current increasingly severe fossil energy crisis and improve the ecological environment. Among them, biomass gasification technology is considered to be the most promising conversion method to replace fossil energy to produce high-quality syngas. The main components of syngas are hydrogen and carbon monoxide, which can be directly used as fuel gas for heating or power generation, and can also be converted into liquid fuels or high-value-added chemicals through Fischer-Tropsch synthesis and separated and purified to produce pure hydrogen. Compared with traditional fixed bed, fluidized bed and entrained bed gasification technologies, chemical chain gasification decomposes the gasification process into oxidation and reduction reactions, which are carried out in two independent reactors or reaction spaces respectively. The lattice oxygen of the oxygen carrier replaces oxygen to circulate between the reactors and transfer heat. Since the gasification and combustion reactions are isolated from each other in space, the dilution of the syngas by the flue gas produced by combustion and nitrogen in the air is effectively avoided. However, the biomass gasification process will be accompanied by the production of a large amount of tar by-products, which not only corrodes and blocks the pipelines, affects the continuous operation of the gasification device, but also reduces the efficiency of the gasification process. In addition, the gas-solid oxidation reaction between the oxygen carrier and the gaseous product during the chemical chain gasification process is more likely to occur than the solid-solid oxidation reaction between the oxygen carrier and the biomass. Therefore, the oxygen carrier will preferentially oxidize the hydrogen and carbon monoxide in the gaseous product, resulting in a decrease in the synthesis gas yield and an increase in the carbon dioxide content in the synthesis gas composition, poor quality, and unsuitable for downstream applications.

In view of the problem of high tar and carbon dioxide content in the biomass gasification process, patent CN107057797A discloses a composite oxygen carrier, a preparation method and its application in solid fuel gasification. The application method comprises: in a fuel reactor, solid fuel undergoes a gasification reaction under the combined action of an oxidized composite oxygen carrier and water vapor; a crude synthesis gas generated by the gasification reaction enters an absorption reactor, where carbon dioxide in the crude synthesis gas is absorbed by calcium oxide to obtain high-quality synthesis gas; the reduced composite oxygen carrier and the incompletely gasified semi-coke in the fuel reactor enter an air reactor, wherein the semi-coke undergoes a combustion reaction with the introduced hot air, and the reduced oxygen carrier is oxidized and regenerated by the hot air and heated by the high-temperature hot flue gas generated by the combustion; after separation by a gas-solid separator, the oxidized oxygen carrier returns to the fuel reactor; the calcium oxide that absorbs carbon dioxide enters a calcination reactor, is heated and lifted by the hot flue gas from the air reactor, and is calcined and regenerated during the lifting process; the regenerated calcium oxide is separated by a gas-solid separator and then returns to the absorption reactor. The shortcomings of this method are: although the carbon dioxide concentration is reduced and the quality of synthesis gas is improved by using calcium oxide to absorb carbon dioxide in the gaseous product, a certain amount of carbon loss is caused, resulting in a decrease in the synthesis gas yield and the carbon monoxide content, and the tar is not fully converted; in addition, both the air reactor and the calcination reactor adopt fast fluidized bed operation, and the residence time of the gas and solid is short, resulting in insufficient regeneration of the reduced oxygen carrier and the calcium oxide that absorbs carbon dioxide, and it is also difficult to heat to the required temperature.

Patent CN110982558B discloses a method for directly producing hydrogen and carbon monoxide by biomass gasification based on chemical chain technology, including: in a fluidized bed fuel reactor, biomass undergoes gasification reaction under the action of calcium oxide oxygen carrier loaded with iron or nickel and water vapor, and calcium oxide is used to absorb carbon dioxide in the gaseous product to produce high-purity hydrogen; the oxygen carrier after the reaction and the semi-coke that is not completely gasified are separated by a gas-solid separator and enter an oxygen reactor, where the semi-coke undergoes partial oxidation reaction with the introduced oxygen to generate carbon monoxide, while releasing reaction heat to decompose calcium carbonate into calcium oxide and carbon dioxide, and then the generated carbon dioxide reacts with the semi-coke to generate carbon monoxide. This method reacts carbon dioxide with semi-coke, which can reduce the concentration of carbon dioxide in the synthesis gas, improve the quality of the synthesis gas, and increase the carbon monoxide content in the synthesis gas. However, there are also the following shortcomings: both the fuel reactor and the oxygen reactor adopt fluidized bed operation, and the defect of short gas residence time will cause insufficient conversion of the tar produced in the fuel reactor, and the unconverted tar is also easy to condense in the gas-solid separation device, affecting the stable operation of the system; in addition, the gas-solid contact time of carbon dioxide and semi-coke in the oxidation reactor is short, so it is difficult to fully convert carbon dioxide.

Summary of the invention

The present invention aims to solve the problems of insufficient conversion of tar and carbon dioxide in the above-mentioned biomass chemical chain gasification process, difficulty in balancing the yield and quality of synthesis gas, and insufficient regeneration of oxygen carriers, and provides a method and device for producing clean synthesis gas by biomass chemical chain gasification.

The technical solution of the present invention is as follows:

A method for producing clean synthesis gas by chemical chain gasification of biomass, the method comprising the following steps: in a moving bed fuel reactor (1), biomass undergoes pyrolysis reaction and gasification reaction under the heating and oxidation action of an oxidized oxygen carrier from an oxygen carrier silo (5), generating gaseous products, semi-coke and reduced oxygen carriers, the temperature of the moving bed fuel reactor (1) being 800-900° C.; the generated gaseous products enter a moving bed reforming reactor (2) through a louver (1a), tar and carbon dioxide in the gaseous products undergo a tar carbon dioxide reforming reaction under the heating and catalytic action of a catalyst from a regenerator (8), and dust in the gaseous products is captured by a moving particle bed formed by the catalyst, the obtained clean synthesis gas is led out from a gas channel (2b) through the louver (2a), the temperature of the moving bed reforming reactor (2) being 750-850° C. ℃; the semi-coke and reduced oxygen carrier in the moving bed fuel reactor (1) enter the combustion section (3a) at the lower part of the riser air reactor (3), where the reduced oxygen carrier is oxidized into oxidized oxygen carrier by the hot air introduced, and the semi-coke is burned out by the hot air to generate ash and hot flue gas. The heat released by the combustion heats the oxidized oxygen carrier, and then the oxidized oxygen carrier and ash enter the lifting section (3b) at the upper part of the riser air reactor (3) and are lifted by the hot flue gas and the hot air introduced to the gas-solid separator (4). The inlet temperature of the hot air is higher than 300 ℃; dusty flue gas and oxidized oxygen carrier are separated in the gas-solid separator (4), wherein the dusty flue gas is discharged after dust removal and heat recovery, and the oxidized oxygen carrier enters the oxygen carrier silo (5), and then returns to the moving bed fuel reactor (1), forming a circulation loop; the carbon deposited catalyst with dust captured in the moving bed reforming reactor (2) enters the lifter (6) and is lifted by air to the gas-solid separator (7); the dusty tail gas and the carbon deposited catalyst are separated in the gas-solid separator (7), wherein the dusty tail gas is discharged after dust removal, and the carbon deposited catalyst enters the regenerator (8), is regenerated by combustion with the introduced hot air and auxiliary fuel, and the heat released by the combustion heats the regenerated catalyst, and then returns to the reaction chamber of the moving bed reforming reactor (2), forming a circulation loop.

The moving bed fuel reactor (1) and the moving bed reforming reactor (2) are connected via a baffle plate with a shutter (1a) at the top, and the shutter (1a) is higher than the particle bed in the moving bed fuel reactor (1); a baffle plate with a shutter (2a) at the bottom is arranged on the right side of the moving bed reforming reactor (2), thereby forming parallel flow and cross flow contact between the gaseous product and the moving particle bed and allowing the clean synthesis gas to be drawn out. The moving bed operation mode of the fuel reactor is conducive to the solid-solid contact and reaction between the biomass and the oxygen carrier. The moving bed operation mode of the reforming reactor is conducive to the full contact between the tar and the catalyst, and prolongs the contact time between the tar and the catalyst, so that the tar conversion is more complete, and the formed moving particle bed can also be used to capture dust in the gaseous product.

The top of the combustion section (3a) of the riser air reactor (3) is connected to the bottom of the lifting section (3b); the combustion section (3a) is a dense phase fluidized bed to provide sufficient gas and solid residence time for full combustion of the semi-coke and full heating of the oxidized oxygen carrier by utilizing the heat released by the combustion; the lifting section (3b) is a dilute phase conveying bed for lifting the oxidized oxygen carrier and continuing to heat the oxidized oxygen carrier by utilizing the hot flue gas during the lifting process; the flow cross-sectional area of the combustion section (3a) is larger than the flow cross-sectional area of the lifting section (3b).

The biomass is one of agricultural waste, forestry waste, energy crops, wood chips or a mixture of several thereof; the particle size of the biomass is 0.1-3 mm.

The oxygen carrier is one of copper-based oxygen carriers, iron-based oxygen carriers, and nickel-based oxygen carriers, or a composite oxygen carrier of two of them, and the particle size of the oxygen carrier is 0.1-0.8 mm; the catalyst is a tar carbon dioxide reforming catalyst, which is a nickel-calcium-based composite oxide catalyst, a nickel-magnesium-based composite oxide catalyst, or a nickel-cerium-based composite oxide catalyst, and the particle size of the tar carbon dioxide reforming catalyst is 0.4-0.8 mm.

The temperature of the moving bed fuel reactor (1) is controlled by controlling the temperature of the oxidized oxygen carrier entering the moving bed fuel reactor (1) and the ratio of the oxidized oxygen carrier circulation rate to the biomass feed rate, wherein the temperature of the oxidized oxygen carrier entering the moving bed fuel reactor (1) is 900-950°C, and the ratio of the oxidized oxygen carrier circulation rate to the biomass feed rate is 15-50:1.

When the combustion in the riser air reactor (3) is insufficient to heat the oxidized oxygen carrier to the temperature for entering the moving bed fuel reactor (1), heat is supplemented by adding auxiliary fuel in the combustion section (3a) at the bottom of the riser air reactor (3) and utilizing the combustion of the auxiliary fuel.

The temperature of the moving bed reforming reactor (2) is controlled by controlling the temperature of the catalyst entering the moving bed reforming reactor (2) and the ratio of the catalyst circulation rate to the biomass feed rate, wherein the temperature of the catalyst entering the moving bed reforming reactor (2) is 850-900° C., and the ratio of the catalyst circulation rate to the biomass feed rate entering the moving bed reforming reactor (2) is 10-50:1.

Fresh oxygen carrier and catalyst inlets are respectively arranged at the lower part of the riser air reactor and the lower part of the riser to replenish the wear and loss of the oxygen carrier and the catalyst.

The present invention also provides a biomass chemical chain gasification device for producing clean syngas, comprising:

A moving bed fuel reactor (1), wherein the moving bed fuel reactor (1) is used to carry out pyrolysis and gasification reactions on biomass to generate gaseous products, semi-coke and reduced oxygen carriers;

A moving bed reforming reactor (2), the moving bed reforming reactor (2) being connected to the moving bed fuel reactor (1) via a first louver (1a), the gaseous product entering the moving bed reforming reactor via the first louver (1a) to undergo a tar carbon dioxide reforming reaction and adsorption and dust removal to obtain a clean synthesis gas;

a first circulation loop, the first circulation loop comprising a riser air reactor (3), the moving bed fuel reactor (1) being connected to the riser air reactor (3) via a combustion section (3a) at a lower portion of the riser air reactor (3), the lifting section (3b) at an upper portion of the riser air reactor (3) being connected to a first gas-solid separator (4); the first gas-solid separator (4) being connected to the moving bed fuel reactor (1) via an oxygen carrier silo (5);

A second circulation loop, wherein the second circulation loop comprises a lifter (6), the lifter (6) being connected to the moving bed reforming reactor (2), and the carbon deposited catalyst with dust captured enters the lifter (6) and is lifted by air to a second gas-solid separator (7); the second gas-solid separator (7) is connected to the moving bed reforming reactor (2) via a regenerator (8).

Optionally, it further comprises a second louver (2a), wherein the second louver (2a) is arranged in the moving bed reforming reactor (2), and the clean synthesis gas is led out through the second louver (2a).

Optionally, it also includes oxygen carrier and catalyst inlets respectively arranged at the lower part of the riser air reactor (3) and the lower part of the riser (6) to compensate for the wear and loss of the oxygen carrier and the catalyst.

Optionally, the first gas-solid separator (4) discharges dust-containing flue gas, and the second gas-solid separator (7) discharges dust-containing tail gas.

Beneficial effects of the present invention:

(1) By using a dual-circulation oxygen carrier and tar-CO2 reforming catalyst, the in-situ and efficient removal of tar, CO2 and dust from biomass gasification and its gaseous products was achieved. At the same time, tar and CO2 were converted into hydrogen and carbon monoxide, which increased the yield and quality of synthesis gas and significantly improved the atomic and energy utilization.

(2) By using independent dual-cycle operations, the biomass gasification, tar CO2 reforming, and oxygen carrier and catalyst regeneration processes can be independently optimized and regulated, and contact and mutual contamination between the oxygen carrier and the tar CO2 reforming catalyst can be avoided.

(3) In-situ removal of tar and carbon dioxide eliminates the need for subsequent condensation purification units and can utilize the sensible heat in the gaseous products to directly connect with downstream units, which not only shortens the process flow of biomass chemical chain gasification to produce synthesis gas, reduces equipment costs, but also improves the comprehensive energy utilization efficiency.

(4) The gas-solid co-flow and cross-flow contact modes in the moving bed reforming reaction are conducive to the full contact between tar and carbon dioxide and the tar-carbon dioxide reforming catalyst, thereby achieving efficient conversion of tar and carbon dioxide.

(5) A dense phase fluidized bed combustion section is set at the bottom of the riser air reactor to provide sufficient residence time for the gas and solids to fully burn the semi-coke and heat the oxidized oxygen carrier to the required temperature, thus overcoming the short residence time of the gas and solids in the traditional riser reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a process flow chart of producing clean syngas by chemical chaining gasification of biomass according to one embodiment of the present invention.

In the figure: 1 moving bed fuel reactor; 1a shutter; 2 moving bed reforming reactor; 2a shutter; 2b gap; 3 riser air reactor; 3a combustion section; 3b lifting section; 4 first gas-solid separator; 5 oxygen carrier silo; 6 lifter; 7 second gas-solid separator; 8 regenerator.

DETAILED DESCRIPTION

In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

Example 1

As shown in FIG1 , this embodiment provides a method for producing clean syngas by biomass chemical chain gasification, which comprises the following steps:

In the moving bed fuel reactor (1), the biomass undergoes pyrolysis and gasification reactions under the heating and oxidation of the oxidized oxygen carrier from the oxygen carrier silo (5), thereby generating gaseous products, semi-coke and reduced oxygen carrier;

The gaseous product enters the moving bed reforming reactor (2), and the tar and carbon dioxide in the gaseous product undergo a tar-carbon dioxide reforming reaction under the heating and catalytic action of the catalyst from the regenerator (8), while the moving particle bed formed by the catalyst is used to capture dust in the gaseous product, and the obtained clean synthesis gas is led out from the gas channel (2b);

in,

The semi-coke and reduced oxygen carrier in the moving bed fuel reactor (1) enter the combustion section (3a) at the bottom of the riser air reactor (3), the reduced oxygen carrier is oxidized into oxidized oxygen carrier by the introduced hot air, the semi-coke is burned out by the hot air to generate ash and hot flue gas, the heat released by the combustion heats the oxidized oxygen carrier, and then the oxidized oxygen carrier and the ash enter the lifting section (3b) at the top of the riser air reactor (3) and are lifted to the gas-solid separator (4) by the hot flue gas and the introduced hot air; the dusty flue gas and the oxidized oxygen carrier are separated in the first gas-solid separator (4), wherein the dusty flue gas is discharged after dust removal and heat recovery, and the oxidized oxygen carrier enters the oxygen carrier silo (5), and then returns to the moving bed fuel reactor (1), forming a first circulation loop;

The carbon deposited catalyst with dust trapped in the moving bed reforming reactor (2) enters the lifter (6) and is lifted by air to the second gas-solid separator (7); the dust-containing tail gas and the carbon deposited catalyst are separated in the second gas-solid separator (7), wherein the dust-containing tail gas is discharged after dust removal, and the carbon deposited catalyst enters the regenerator (8) and is regenerated by combustion with the introduced hot air and auxiliary fuel, and the heat released by the combustion heats the regenerated catalyst, and then returns to the reaction chamber of the moving bed reforming reactor (2), forming a second circulation loop.

Wherein, the biomass is one of agricultural waste, forestry waste, energy crops, wood chips or a mixture of several thereof; and/or the particle size of the biomass is 0.1-3 mm.

Optionally, the oxygen carrier is one of a copper-based oxygen carrier, an iron-based oxygen carrier, and a nickel-based oxygen carrier, or a composite oxygen carrier of two of them; and/or the particle size of the oxygen carrier is 0.1-0.8 mm; and/or the catalyst is a tar carbon dioxide reforming catalyst;

Preferably, the catalyst is a nickel-calcium-based composite oxide catalyst, a nickel-magnesium-based composite oxide catalyst, or a nickel-cerium-based composite oxide catalyst;

Preferably, the particle size of the tar carbon dioxide reforming catalyst is 0.4-0.8 mm.

Optionally, the method further comprises controlling the temperature of the moving bed fuel reactor (1) by controlling the temperature of the oxidized oxygen carrier entering the moving bed fuel reactor (1) and the ratio of the oxidized oxygen carrier circulation rate to the biomass feed rate;

Optionally, the temperature of the oxidized oxygen carrier entering the moving bed fuel reactor (1) is 900-950°C, and the ratio of the circulation rate of the oxidized oxygen carrier entering the moving bed fuel reactor (1) to the biomass feed rate is (15-50):1.

Optionally, it also includes:

When the combustion in the riser air reactor (3) is insufficient to heat the oxidized oxygen carrier to the temperature for entering the moving bed fuel reactor (1), heat is supplemented by adding auxiliary fuel in the combustion section (3a) at the bottom of the riser air reactor (3) and utilizing the combustion of the auxiliary fuel.

Optionally, the method further comprises controlling the temperature of the moving bed reforming reactor (2) by controlling the temperature of the catalyst entering the moving bed reforming reactor (2) and the ratio of the catalyst circulation rate to the biomass feed rate;

Preferably, the temperature of the catalyst entering the moving bed reforming reactor (2) is 850-900° C., and the ratio of the catalyst circulation rate entering the moving bed reforming reactor (2) to the biomass feed rate is (10-50):1.

Specifically, the present disclosure proposes a method for producing clean syngas by chemical chain gasification of biomass. In the experiment, pine sawdust was selected as the biomass raw material. Before the experiment, the raw material was crushed and sieved to an average particle size of 0.38-0.83 mm, and dried in an oven at 105-110°C for 3 hours. The industrial analysis and elemental analysis of the pine sawdust are shown in Table 1.

Table 1 Industrial analysis and elemental analysis of pine sawdust

(*Subtraction)

The oxygen carrier is CuO/olivine, in which the theoretical loading of CuO is 10%. Preparation method: First, crush the olivine and screen out particles with an average particle size range of 0.15~0.25mm, and then place it in a muffle furnace for calcination at 900 ^o C for 4h. The calcined olivine is placed in a certain concentration of Cu(NO ₃ ) ₂ ·3H ₂ O solution with equal volume and immersed for 24h, and finally calcined in a muffle furnace at 900 ^o C for 4h.

The tar reforming catalyst is a NiO-CaO/olivine composite oxide catalyst, in which the total loading of NiO and CaO in the catalyst is 5%, and the molar ratio of NiO to CaO is 3:1. Preparation method: First, a certain concentration of Ni(NO ₃ ) ₂ ·6H ₂ O and Ca(NO ₃ ) ₂ ·4H ₂ O mixed aqueous solution is prepared. A certain amount of olivine particles with a particle size range of 0.38~0.83mm calcined at 900 ^o C are weighed and immersed in the above solution at room temperature for 12 hours. Then, the remaining water is removed by reduced pressure distillation at 90 ^o C in a rotary evaporator, and then dried in an oven at 105~110 ^o C for 12 hours, and finally calcined in a muffle furnace at 900 ^o C in an air atmosphere for 4 hours.

As shown in FIG1 , about 3.0 kg of CuO/olivine oxygen carrier is first added to the oxygen carrier silo (5), and about 5 kg of NiO-CaO/olivine tar carbon dioxide reforming catalyst is added to the regenerator (8); the catalyst is, for example, a nickel-calcium-based composite oxide catalyst, a nickel-magnesium-based composite oxide catalyst, or a nickel-cerium-based composite oxide catalyst. The air flow rate of the combustion section (3a) at the lower part of the riser air reactor (3) is adjusted to about 2.2-2.5 m ³ /h, and the air flow rate of the riser section (3b) is adjusted to about 4.0-4.2 m ³ /h. The ratio of the circulation rate of the oxygen carrier entering the moving bed fuel reactor (1) to the feed rate is 12, and the temperature of the moving bed fuel reactor (1) is 800 ^° C. The ratio of the circulation rate of the tar carbon dioxide reforming catalyst entering the moving bed reforming reactor (2) to the feed rate is 10, and the temperature of the moving bed reforming reactor (2) is 800 ^° C. The biomass is fed into the moving bed fuel reactor (1) by a two-stage screw feeder at a feed rate of 0.22 kg/h, and is heated and oxidized by the high-temperature oxidized oxygen carrier from the oxygen carrier silo (5), and undergoes pyrolysis and gasification reactions. The generated gaseous product enters the moving bed reforming reactor (2) through the first louvered gas channel on the upper part of the baffle, and is in parallel and cross-current contact with the moving particle bed formed by the catalyst descending from the regenerator (8). The tar and carbon dioxide in the gaseous product are converted into hydrogen and carbon monoxide under the catalytic action of the tar carbon dioxide reforming catalyst, and the dust carried in the gaseous product is captured by the moving particle bed. The obtained clean synthesis gas is drawn out from the second louvered gas channel on the lower part of the right baffle of the moving bed reforming reactor (2), wherein the condensable components in the gas are captured by the condensation system and collected in the tar storage tank, and the non-condensable components are collected in the gas cabinet after passing through the condensation cooler. The reduced oxygen carrier and semi-coke leaving the moving bed fuel reactor (1) enter the combustion section (3a) at the bottom of the riser air reactor (3), where the semi-coke is burned out by the hot air and releases heat, and the reduced oxygen carrier is oxidized by the hot air and heated to 900 ^° C, and then enters the lifting section (3b), where it is lifted by the hot air and hot flue gas to the first gas-solid separator (4). The carbon deposited catalyst with dust trapped leaving the moving bed reforming reactor enters the lifter (6), where it is lifted by air to the second gas-solid separator (7). The separated carbon deposited catalyst enters the regenerator, where it is regenerated by burning with the hot air and heated to 850 ^° C. The inlet temperature of the hot air is 400 ^° C. The first gas-solid separator (4) and the second gas-solid separator (7) are both cyclone separators.

The comparison of sawdust gasification performance under different bed materials is shown in Table 2. The experimental results show that when CuO/olivine oxygen carrier is used as circulating solid heat carrier, the content of tar, methane and carbon dioxide in the gas composition is high, and the quality of syngas is poor. When CuO/olivine oxygen carrier and NiO-CaO/olivine tar carbon dioxide reforming catalyst are used, the gas yield and cold gas efficiency increase, the content of tar, methane and carbon dioxide in the gas composition decreases significantly, and the content of hydrogen and carbon monoxide increases. No significant amount of dust was detected in the collected liquid product.

Table 2 Comparison of pine sawdust gasification performance under different bed materials

Example 2

As shown in FIG1 , the present disclosure further proposes a biomass chemical chain gasification device for producing clean synthesis gas, which corresponds to the method disclosed in Example 1, and the same parts will not be repeated here.

The device includes:

A moving bed fuel reactor (1) is used for carrying out pyrolysis and gasification reactions on biomass to generate gaseous products, semi-coke and reduced oxygen carriers; the biomass is, for example, agricultural waste, forestry waste, energy crops, wood chips or a mixture of several thereof; the particle size of the biomass is 0.1-3 mm.

A moving bed reforming reactor (2), wherein the moving bed reforming reactor (2) is separated from the moving bed fuel reactor (1) by a baffle plate having a first louver (1a) on the upper portion, and the first louver (1a) is higher than a particle bed in the moving bed fuel reactor (1); the moving bed reforming reactor (2) is connected to the moving bed fuel reactor (1) via the first louver (1a); a baffle plate having a second louver (2a) on the lower portion is arranged on the right side of the moving bed reforming reactor (2); the gaseous product enters the moving bed reforming reactor (2) via the first louver (1a) and contacts with the moving particle bed in parallel flow and cross flow to carry out a tar carbon dioxide reforming reaction, and after adsorption and dust removal, the clean synthesis gas is led out via the second louver (2a).

a first circulation loop, the first circulation loop comprising a riser air reactor (3), the outlet of the moving bed fuel reactor (1) being connected to the riser air reactor (3) via a combustion section (3a) at a lower portion of the riser air reactor (3), the outlet of a lifting section (3b) at an upper portion of the riser air reactor (3) being connected to a first gas-solid separator (4); the outlet of the first gas-solid separator (4) being connected to the moving bed fuel reactor (1) via an oxygen carrier silo (5);

A second circulation loop, wherein the second circulation loop comprises a lifter (6), the outlet of the moving bed reforming reactor (2) is connected to the lifter (6), and the carbon deposited catalyst with dust captured enters the lifter (6) and is lifted by air to the second gas-solid separator (7); the outlet of the second gas-solid separator (7) is connected to the moving bed reforming reactor (2) via a regenerator (8).

Optionally, it further comprises a second louver (2a), wherein the second louver (2a) is arranged at the lower end of the right side of the moving bed reforming reactor (2), and the clean synthesis gas is led out through the second louver (2a).

Optionally, it also includes oxygen carrier and catalyst inlets respectively arranged at the lower part of the riser air reactor (3) and the lower part of the riser (6) to compensate for the wear and loss of the oxygen carrier and the catalyst.

Optionally, the first gas-solid separator (4) discharges dust-containing flue gas, and the second gas-solid separator (7) discharges dust-containing tail gas.

Beneficial effects of the present invention:

(1) By using a double-circulation oxygen carrier and tar-CO2 reforming catalyst, the in-situ and efficient removal of tar, CO2 and dust from biomass gasification and its gaseous products was achieved. At the same time, tar and CO2 were converted into hydrogen and carbon monoxide, which increased the yield and quality of synthesis gas and significantly improved the atomic and energy utilization.

(2) By using independent dual-cycle operations, the biomass gasification, tar CO2 reforming, and oxygen carrier and catalyst regeneration processes can be independently optimized and regulated, and contact and mutual contamination between the oxygen carrier and the tar CO2 reforming catalyst can be avoided.

(3) In-situ removal of tar and carbon dioxide eliminates the need for subsequent condensation purification units and can utilize the sensible heat in the gaseous products to directly connect with downstream units, which not only shortens the process flow of biomass chemical chain gasification to produce synthesis gas, reduces equipment costs, but also improves the comprehensive energy utilization efficiency.

(4) The gas-solid co-flow and cross-flow contact modes in the moving bed reforming reaction are conducive to the full contact between tar and carbon dioxide and the tar-carbon dioxide reforming catalyst, thereby achieving efficient conversion of tar and carbon dioxide.

(5) A dense phase fluidized bed combustion section is set at the bottom of the riser air reactor to provide sufficient residence time for the gas and solids to fully burn the semi-coke and heat the oxidized oxygen carrier to the required temperature, thus overcoming the shortcoming of short residence time of gas and solids in the traditional riser reactor.

It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims (14)

1. A method for preparing clean synthetic gas by biomass chemical chain gasification, which is characterized by comprising the following steps:

in the moving bed fuel reactor (1), biomass is subjected to pyrolysis reaction and gasification reaction under the heating and oxidization action of an oxidation state oxygen carrier from an oxygen carrier bin (5) to generate gaseous products, semicoke and a reduction state oxygen carrier;

the method comprises the steps that gaseous products enter a moving bed reforming reactor (2) through a first louver (1 a), tar and carbon dioxide in the gaseous products are subjected to tar carbon dioxide reforming reaction under the heating and catalytic action of a catalyst from a regenerator (8), dust in the gaseous products is captured by a moving particle bed formed by the catalyst, and clean synthesis gas is led out through a second louver (2 a) and a gas channel (2 b) arranged in the moving bed reforming reactor (2);

wherein,,

the semicoke and the reduced oxygen carrier in the moving bed fuel reactor (1) enter a combustion section (3 a) at the lower part of the riser air reactor (3), the combustion section (3 a) is a dense phase fluidized bed combustion section so as to provide enough residence time for gas and solid to fully burn the semicoke and heat the oxidized oxygen carrier to a required temperature, the reduced oxygen carrier is oxidized into the oxidized oxygen carrier by the introduced hot air, the semicoke is burnt out by the hot air to generate ash and hot flue gas, the oxidized oxygen carrier is heated by the heat released by the combustion, and then the oxidized oxygen carrier and the ash enter a lifting section (3 b) at the upper part of the riser air reactor (3) and are lifted to a first gas-solid separator (4) by the hot flue gas and the introduced hot air; the dust-containing flue gas and the oxidation state oxygen carrier are separated in a first gas-solid separator (4), wherein the dust-containing flue gas is discharged after dust removal and heat recovery, the oxidation state oxygen carrier enters an oxygen carrier bin (5) and then returns to the moving bed fuel reactor (1) to form a first circulation loop;

the carbon deposition catalyst in the moving bed reforming reactor (2) with captured dust enters a lifter (6) and is lifted to a second gas-solid separator (7) by air; the dust-containing tail gas and the carbon deposition catalyst are separated in a second gas-solid separator (7), wherein the dust-containing tail gas is discharged after dust removal, the carbon deposition catalyst enters a regenerator (8) to be burnt and regenerated with the introduced hot air and auxiliary fuel, and the heat released by the burning heats the regenerated catalyst and then returns to a reaction chamber of a moving bed reforming reactor (2) to form a second circulation loop;

the method further comprises controlling the temperature of the moving bed fuel reactor (1) by controlling the temperature of the oxidized oxygen carrier entering the moving bed fuel reactor (1) and the ratio of the oxidized oxygen carrier circulation rate to the biomass feed rate.

2. The method for producing clean syngas by chemical chain gasification of biomass according to claim 1, wherein the biomass is an energy crop.

3. The method for producing clean syngas by chemical chain gasification of biomass according to claim 2, wherein the biomass is agricultural waste or forestry waste.

4. The method for producing clean syngas by chemical chain gasification of biomass according to claim 1, wherein the particle size of the biomass is 0.1-3mm.

5. The method for producing clean syngas by biomass chemical chain gasification according to claim 1, wherein the oxygen carrier is one or two of copper-based oxygen carriers, iron-based oxygen carriers, and nickel-based oxygen carriers; and/or the catalyst is a tar carbon dioxide reforming catalyst.

6. The method for producing clean syngas by chemical chain gasification of biomass according to claim 5, wherein the catalyst is a nickel-calcium-based composite oxide catalyst or a nickel-magnesium-based composite oxide catalyst or a nickel-cerium-based composite oxide catalyst.

7. The method for producing clean syngas by chemical looping gasification of biomass according to claim 5, wherein the particle size of the oxygen carrier is 0.1-0.8mm; the particle size of the tar carbon dioxide reforming catalyst is 0.4-0.8mm.

8. The method for preparing clean synthetic gas by chemical looping gasification of biomass according to claim 1, wherein,

wherein the temperature of the oxidation state oxygen carrier entering the moving bed fuel reactor (1) is 900-950 ℃, and the ratio of the circulation rate of the oxidation state oxygen carrier entering the moving bed fuel reactor (1) to the biomass feed rate is (15-50): 1.

9. the method for producing clean syngas by chemical looping gasification of biomass according to claim 1, further comprising:

when the combustion in the riser air reactor (3) is insufficient to heat the oxygen carrier in oxidation state to a temperature at which it enters the moving bed fuel reactor (1), the heat is supplemented by the combustion of the auxiliary fuel by adding the auxiliary fuel in the combustion section (3 a) at the bottom of the riser air reactor (3).

10. The method of producing clean syngas by chemical chain gasification of biomass according to claim 1, further comprising controlling the temperature of the moving bed reforming reactor (2) by controlling the temperature of the catalyst entering the moving bed reforming reactor (2) and the ratio of catalyst circulation rate to biomass feed rate.

11. The method for producing clean syngas by chemical chain gasification of biomass according to claim 10, wherein the temperature of the catalyst entering the moving bed reforming reactor (2) is 850-900 ℃, and the ratio of the circulation rate of the catalyst entering the moving bed reforming reactor (2) to the feed rate of biomass is (10-50): 1.

12. a device for preparing clean synthetic gas by biomass chemical chain gasification, which is characterized by comprising:

the moving bed fuel reactor (1) is used for carrying out pyrolysis reaction and gasification reaction on biomass to generate gaseous products, semicoke and a reduced oxygen carrier;

the moving bed reforming reactor (2), the moving bed reforming reactor (2) is communicated with the moving bed fuel reactor (1) through a first louver (1 a), and the gaseous product enters the moving bed reforming reactor through the first louver (1 a) to carry out tar carbon dioxide reforming reaction and adsorption dust removal to obtain clean synthetic gas;

a first circulation loop comprising a riser air reactor (3), the combustion section (3 a) and the lifting section (3 b) of the riser air reactor each having a hot air inlet, the moving bed fuel reactor (1) being in communication with the riser air reactor (3) via the combustion section (3 a) in the lower part of the riser air reactor (3), the combustion section (3 a) being a dense-phase fluidized-bed combustion section to provide sufficient residence time for gases and solids to fully combust semicoke and heat the oxidized oxygen carrier to the desired temperature, the lifting section (3 b) in the upper part of the riser air reactor (3) being connected to a first solids separator (4) by controlling the temperature of the moving bed fuel reactor (1) by controlling the temperature of the oxidized oxygen carrier entering the moving bed fuel reactor (1) and the ratio of the oxidized oxygen carrier circulation rate to the biomass feed rate, such that the oxidized oxygen carrier and ash enter the first solids separator (4) in the upper part of the riser air reactor (3 b) are separated by the hot air entering the first solids separator (4); the first gas-solid separator (4) is connected with the moving bed fuel reactor (1) through an oxygen carrier bin (5);

a second circulation loop, wherein the second circulation loop comprises a lifter (6), the lifter (6) is connected with the moving bed reforming reactor (2), and the carbon deposition catalyst with captured dust enters the lifter (6) and is lifted to a second gas-solid separator (7) by air; the second gas-solid separator (7) is connected with the moving bed reforming reactor (2) through a regenerator (8);

the system also comprises a second louver (2 a), wherein the second louver (2 a) is arranged in the moving bed reforming reactor (2), and clean synthesis gas is led out through the second louver (2 a).

13. The apparatus for producing clean syngas by chemical chain gasification of biomass according to claim 12, further comprising oxygen carrier and catalyst inlet provided at the lower part of the riser air reactor (3) and the lower part of the riser (6), respectively, to supplement the wear and loss of oxygen carrier and catalyst.

14. The clean synthesis gas plant for chemical looping gasification of biomass according to claim 12, characterized in that said first gas-solid separator (4) discharges a dust-laden flue gas and said second gas-solid separator (7) discharges a dust-laden tail gas.

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