CN102517089A - Device and method for preparing high-calorific value combustible gas through biomass gasification and melting - Google Patents

Abstract

The invention discloses a device and method for producing clean combustible gas with high calorific value through gasification and melting of biomass, which can be used to prepare clean combustible gas with high calorific value. The device consists of a fluidized bed gasification reactor, a cyclone melting furnace, a superheater, Coal burner, heat pipe heat exchanger, bag filter, desulfurization tower, compression device and gas storage tank, etc. The invention is a high-efficiency biomass gasification technology that breaks through the prior art, can produce combustible gas with high calorific value, and can effectively reduce the contents of tar, carbon particles and ash in the gas. The heat utilization efficiency of the system is high, and it is safe and reliable.

Description

A device and method for producing high calorific value combustible gas by gasification and melting of biomass

technical field

The invention relates to a device and method for producing clean combustible gas with high calorific value through gasification and melting of biomass, and belongs to the field of solid waste resource disposal.

Background technique

The development of the economy and the progress of the society have led to an increasing demand for energy. The energy crisis caused by the reduction of fossil fuels such as coal and oil has intensified. Building a clean and safe energy future has become the common goal of all countries in the world. In 2007, the European Union issued a roadmap for renewable energy, proposing a goal of 20% of renewable energy in final energy consumption by 2020, and emphasizing the development and utilization of biomass energy. As the only renewable energy that can be converted into hydrocarbon fuels, biomass energy is not only rich in raw materials and widely distributed, but also a "carbon-neutral" energy source, which can effectively alleviate the problem of global warming. Biomass gasification and synthesis of liquid fuel technology through gasification can quickly convert a large number of different types of biomass into gas or liquid fuels that are convenient for storage and transportation, and have strong commercial feasibility. However, the overall efficiency of the current biomass gasification system is relatively low, and the gasification products are mostly low-quality combustible gases with low calorific value and high tar and ash content, which cannot directly replace fossil fuels such as coal, oil, and natural gas, resulting in gasification The economy of the technology is poor and the commercial competitiveness is low. Therefore, how to improve the efficiency of biomass gasification technology and improve the quality of combustible gas is an important problem to be solved in the field of biomass gasification.

Biomass gasification technology uses gasification agent to incompletely burn biomass to generate synthetic combustible gas containing H ₂ , CO, etc. under high temperature and oxygen-deficient atmosphere. According to different gasification agents, biomass gasification can be divided into: air gasification, oxygen gasification and water vapor gasification. The cost of air gasification is low, the equipment is simple, and the operation is feasible. However, due to the dilution of a large amount of nitrogen, the calorific value of the produced combustible gas is low, generally only 4-7MJ/Nm ³ . Oxygen gasification eliminates the influence of nitrogen, and the calorific value of gas produced is 10-18MJ/Nm ³ , which is equivalent to that of city gas. However, the high cost of pure oxygen preparation limits its popularization and application, and the use of oxygen-enriched oxidation can effectively reduce the cost. Steam gasification can produce hydrogen-rich combustible gas with a calorific value of 10-14MJ/Nm ³ . However, since steam gasification reforming is a strong endothermic reaction, it needs to be carried out at a temperature above 800 °C without a catalyst, so the gasification process needs to add external heating equipment, and the system complexity increases.

At present, besides combustible gases such as H ₂ and CO, biomass gasification products also contain impurities such as tar, carbon particles and ash. Tar is mixed with combustible gas in gaseous form at high temperature, but when it is lower than 200°C, it will condense into liquid, block equipment and pipelines, and affect the safe transportation of combustible gas. Physically, water washing is used to remove tar, not only the liquid recovery and circulation device is huge, but also the sewage after detarring is difficult to treat. Therefore, the current tendency is to remove tar by thermochemical methods, including pyrolysis and catalytic cracking. Pyrolysis can effectively reduce the tar content and increase the carbon conversion rate, but at the same time increases the energy consumption of the system, resulting in a decrease in the calorific value of the combustible gas and an increase in the possibility of reactor sintering. Catalytic cracking converts tar into light gas, increasing the calorific value of combustible gas. However, problems such as poor thermal stability, low mechanical strength, easy carbon deposition or poisoning deactivation of the catalyst restrict the development of tar catalytic cracking process. Ash content in combustible gas is also a key factor affecting gas application. The high concentration of heavy metals and soluble salts in ash will not only cause corrosion and wear of subsequent equipment, but also cause secondary pollution to soil and groundwater. In particular, the gas fly ash produced by fluidized bed gasification has a high content, which cannot be completely removed by traditional cyclone separation technology, resulting in low quality combustible gas and inconvenience to the subsequent gas purification treatment.

To sum up, the current difficulty in producing high-quality combustible gas from biomass gasification lies in how to simultaneously improve the calorific value and cleanliness of the combustible gas. The production of combustible gas with high calorific value requires high cost input (oxygen gasification) or adding an external heat source (steam gasification), while the removal of impurities such as tar and ash will consume part of the heat, resulting in a decrease in the overall energy conversion rate of the gasification system. Small, the quality of combustible gas will decrease.

Contents of the invention

Purpose of the invention: The purpose of the present invention is to address the deficiencies of the prior art and provide a device for producing clean combustible gas with high calorific value through gasification and melting of biomass that can increase the calorific value of combustible gas and reduce the amount of tar and fly ash.

Another object of the present invention is to provide a method for producing clean combustible gas with high calorific value by gasifying and melting biomass.

Technical solution: The device for producing clean combustible gas with high calorific value by gasification and melting of biomass according to the present invention includes a fluidized bed gasification reactor, a cyclone melting furnace, a superheater, an economizer, a heat pipe heat exchanger, and a bag dust collector devices, desulfurization towers, compression devices and gas storage tanks.

The fluidized bed gasification reactor is composed of a gasification reaction zone and an air chamber at the bottom. An air distribution plate is arranged between the air chamber and the gasification reaction area. The side walls and the bottom of the air chamber An air inlet and a slagging outlet are respectively arranged; a steam inlet and a feeder are arranged on the side wall of the gasification reaction zone of the fluidized bed gasification reactor; the gasification of the fluidized bed gasification reactor The upper part of the reaction zone is connected to the inlet of the cyclone melting furnace through a pipeline; the side wall and the bottom of the cyclone melting furnace are respectively provided with an air inlet and a slag discharge port; the top outlet of the cyclone melting furnace is connected with the superheater in turn , the economizer and the heat pipe heat exchanger are connected; the outlet of the heat pipe heat exchanger is connected with the dust remover, the desulfurization tower, the compression device and the gas storage tank in turn.

In the present invention, the fluidized bed gasification reactor is the main gasification equipment; the cyclone melting furnace is the carbon particle, tar cracking and fly ash melting equipment; the superheater, the economizer and the heat pipe heat exchanger are the main heat exchange equipment, The sensible heat of high-temperature combustible gas obtained by gasification and melting is recycled; the combustible gas after heat exchange is further purified by bag filter and desulfurization tower, and the high-quality combustible gas obtained is compressed and collected by the gas storage tank.

In order to prepare oxygen-enriched gas, the device of the present invention also includes an air separation unit, the outlet of the air separation unit is divided into two branches, and one branch is connected to the air inlet of the cyclone melting furnace after passing through the heat pipe heat exchanger. The other branch is connected to the air inlet of the fluidized bed gasification reactor after passing through the heat pipe heat exchanger.

In order to fully recover and utilize the sensible heat of high-temperature combustible gas produced by gasification and melting, a water inlet is provided on the economizer, and the water inlet pipe passes through the economizer and the superheater in sequence and then connects with the fluidized The steam inlet of the bed gasification reactor is connected. After the water is preheated by the economizer, it enters the superheater to be reheated and vaporized to produce water vapor, which is used for the reaction in the fluidized bed gasification reactor.

The method for producing clean combustible gas with high calorific value by gasification and melting of biomass according to the present invention comprises the following steps:

(1) Feed biomass raw materials, oxygen-enriched gas and water vapor into the fluidized bed gasification reactor, generate crude combustible gas under the condition of 450-750°C, and then use the fluidized bed gasification reactor The upper part of the furnace is transported to the cyclone melting furnace; the bottom slag generated by the reaction is discharged from the slag outlet of the fluidized bed gasification reactor;

(2) After the crude combustible gas enters the cyclone melting furnace, the oxygen-enriched gas is introduced into the cyclone melting furnace at the same time, and the tar and carbon particles are removed from the crude combustible gas under the condition of 1100-1450°C The high-temperature combustible gas that has been purified with ash is discharged from the upper part of the cyclone melting furnace, and flows through the heater, economizer and heat pipe heat exchanger in sequence; the slag generated by the reaction is discharged from the slag outlet of the cyclone melting furnace discharge;

(3) The low-temperature combustible gas from the heat pipe heat exchanger flows through the bag filter and the desulfurization tower for further purification. After purification, the purified combustible gas is compressed by the compression device and collected in the gas storage tank.

The invention adopts oxygen-enriched gas and water vapor as the common gasification agent, combines the advantages of the two technologies of oxygen-enriched gasification and cyclone melting, and obtains relatively pure combustible gas with high calorific value through the combination of low-temperature gasification and high-temperature melting. The specific feature of the gasification part in step (1) is that oxygen-enriched gas and water vapor are used as common gasification agents, and oxygen-enriched combustion can provide heat for steam gasification and reforming reactions, thereby forming a self-heating gasification system. The intense heat release in the oxygen-enriched oxidation process provides heat for the steam gasification reforming reaction, which makes the incompletely reacted carbon particles and tar and other macromolecular substances further gasify under the action of water vapor to generate CO and H ₂ , etc. This not only reduces the content of tar and carbon particles in the gasification products, but also improves the carbon conversion rate of the gasification reaction and increases the calorific value of combustible gas. The reaction rate, reaction temperature, carbon conversion rate and gas production calorific value of the whole system are all high.

What should be explained here is that although the evaporation of water from biomass raw materials can also produce water vapor, which may further participate in the gasification and reforming reaction, but because the initial temperature of this part of water vapor is relatively low, the gasification and reforming reaction requires It consumes a lot of heat, so the effect of gasification and reforming reaction only by evaporating water vapor inside the biomass is poor, and the gasification effect obtained by directly passing high-temperature water vapor is better.

The coarse combustible gas purification part of the present invention is an important component of the gas production system, and its specific feature is that a high-temperature cyclone melting furnace is used to remove tar and carbon particles and melt ash. The cyclone melting furnace forms a high-temperature reducing melting atmosphere through the combustion of crude combustible gas and oxygen-enriched gas. It does not require complicated external heat sources, which not only saves heating costs, but also reduces the complexity of the system. The crude combustible gas carrying tar, carbon particles and a large amount of ash is directly passed into the cyclone melting furnace from the upper part of the fluidized bed gasification reactor, and is gasified and melted under the action of combustion-supporting oxygen enrichment, and the temperature in the melting furnace is maintained at 1100-1450 °C high temperature reducing atmosphere. The tar in the combustible gas is cracked at high temperature in the melting furnace to produce small molecule gas, and the macromolecular carbon particles and oxygen-rich gas undergo secondary cracking and gasification. The pyrolysis products of tar and carbon particles are discharged from the upper part of the melting furnace along with the combustible gas. The ash in the combustible gas is melted at high temperature and captured by the inner wall of the furnace under strong swirl and centrifugal action, and then flows into the slag outlet along the inner wall. The heavy metals in the ash exist stably in the slag in the form of compounds, and the slag can be landfilled as ordinary solid waste, and can also be used as building and roadbed materials.

The high-temperature combustible gas that has undergone cyclone melting, purification and ash removal is recycled through heat exchange devices such as superheaters, economizers and heat pipe heat exchangers to improve the energy utilization efficiency of the gasification system. The specific feature is that the heat exchange between combustible gas, water and oxygen-enriched gas is carried out through the superheater, economizer and heat pipe heat exchanger, and the water vapor and oxygen-enriched gas required for gasification are heated while cooling the combustible gas. The specific implementation method is: after the combustible gas is purified and deashed, it flows through the heater, economizer and heat pipe heat exchanger in sequence; after the feed water is preheated by the economizer, it enters the superheater and is reheated to generate high-temperature water vapor required for gasification; The oxygen-enriched gas with an oxygen concentration of 25-95% obtained from air purified by an air separation unit is heated to 200°C by a heat pipe heat exchanger and then sent to a fluidized bed gasification reactor and a cyclone melting furnace.

The low-temperature combustible gas from the heat pipe heat exchanger is further purified and dust-removed through the bag filter and desulfurization tower. The gas first enters the bag filter to remove the remaining fine dust, and then flows into the desulfurization tower to remove the sulfur compounds in it, and finally obtains high-quality clean combustible gas. The purified combustible gas is compressed by the compression device and collected in the gas storage tank for standby, or directly transported to the gas consumption place.

Beneficial effect:

Conventional fluidized bed gasification technology uses air, oxygen, water vapor or a mixture of air (oxygen) and water vapor as the gasification agent, which cannot achieve the balance between investment cost and calorific value of gas production, resulting in low calorific value of combustible gas or system investment higher cost. The high content of fly ash in combustible gas not only brings inconvenience to gas purification, but also causes corrosion and wear of subsequent equipment and secondary pollution of the environment. In addition, tar in combustible gas exists in gaseous form at high temperature, but it will condense into liquid when it is lower than 200°C, which will block equipment and pipelines and affect the safe transportation of combustible gas. The present invention effectively solves this problem by combining oxygen-enriched-steam gasification technology and cyclone melting technology, and realizes the balance between investment cost and gas production calorific value. In terms of investment cost, compared with pure oxygen oxidation, oxygen-enriched oxidation requires lower oxygen concentration and lower oxygen production cost. At the same time, the steam gasification reforming reaction can provide heat through oxygen-enriched combustion, which reduces the pressure of external heat sources and reduces operating costs. In terms of combustible gas quality, due to the low nitrogen content of oxygen-enriched gas, the reaction rate is fast and the thermal efficiency is high. Compared with air gasification, the calorific value of gas production can be nearly doubled. And because the steam gasification reforming reaction increases the concentration of H ₂ and CO in the combustible gas, the calorific value of the crude combustible gas in this technology can be as high as 14-18MJ/Nm ³ .

In the process of gas purification, the cyclone melting furnace is used as a breakthrough for ash melting in combustible gas and secondary cracking and gasification of tar and carbon particles, which effectively solves the problem of high content of fly ash in fluidized bed gas, low carbon conversion rate, and tar clogged pipelines And other problems, improve the carbon conversion rate and gas production calorific value of biomass gasification. Combustion of crude combustible gas and oxygen-enriched gas is used to heat the melting furnace, without adding complicated heating equipment, which saves investment costs and improves energy utilization. The ash is completely melted at high temperature to form slag, and the heavy metal elements in the slag exist in the form of compounds, which will not pollute the environment and can be recycled as building and roadbed materials. Tar and carbon particles continue to be cracked and gasified in a high-temperature reducing atmosphere, which reduces the risk of equipment blockage and coking, and also solves the problems of serious loss of carbon particles and low gas production capacity in previous gasification technologies.

The system is equipped with a heat exchange unit to recover and utilize the sensible heat of high-temperature combustible gas, and adopts superheaters, economizers and heat pipe heat exchangers for heat cascade utilization, which not only realizes the cooling and cooling of combustible gas, but also preheats the water required for gasification Steam and oxygen-enriched gas, the energy utilization efficiency of the system is improved. During the heat exchange process between the oxygen-enriched gas and the combustible gas, since the combustible gas and the oxygen-enriched gas are prone to reaction and explosion, the present invention adopts a heat pipe heat exchanger that does not contact each other to ensure the safety of the system. Finally, bag filter and desulfurization tower are used to further purify and remove combustible gas to ensure the cleanliness of combustible gas.

Description of drawings

Fig. 1 is a schematic diagram of the process flow of biomass gasification and melting to produce high calorific value combustible gas according to the present invention.

In the figure: fluidized bed gasification reactor 1, feeder 1-1, air inlet 1-2, steam inlet 1-3, air chamber 1-4, air distribution plate 1-5, slag outlet 1- 6. Cyclone melting furnace 2, air inlet 2-1, slag outlet 2-2, superheater 3, economizer 4, heat pipe heat exchanger 5, bag filter 6, desulfurization tower 7, compression device 8, gas storage Tank 9, air separation unit 10.

Biomass raw material A, oxygen-enriched gas B, water vapor C, coarse combustible gas D, bottom slag E, high-temperature combustible gas F, slag G, water supply H, dust I, air J, low-temperature combustible gas K, purified combustible gas L.

Detailed ways

The technical solutions of the present invention will be described in detail below, but the protection scope of the present invention is not limited to the embodiments.

Embodiment: The device of the present invention is mainly composed of a fluidized bed gasification reactor 1, a cyclone melting furnace 2, a superheater 3, an economizer 4, a heat pipe heat exchanger 5, a bag filter 6, a desulfurization tower 7, a compression device 8, The air storage tank 9 and the air separation unit 10 are composed.

The fluidized bed gasification reactor 1 is composed of a gasification reaction zone and an air chamber 1-4 at the bottom, and an air distribution plate 1-5 is arranged between the air chamber 1-4 and the gasification reaction zone. The side wall and bottom of the air chamber 1-4 are respectively provided with an air inlet 1-2 and a slag discharge port 1-6; the side wall of the gasification reaction zone of the fluidized bed gasification reactor 1 is provided with Steam inlet 1-3 and feeder 1-1; the upper part of the gasification reaction zone of the fluidized bed gasification reactor 1 is connected with the inlet of the cyclone melting furnace 2 through a pipeline; the cyclone melting furnace 2 The side wall and bottom of the furnace are respectively provided with an air inlet 2-1 and a slagging outlet 2-2; the top outlet of the cyclone melting furnace 2 is connected with the superheater 3, the economizer 4 and the heat pipe heat exchanger 5 in sequence; The outlet of the heat pipe heat exchanger 5 is sequentially connected with the bag filter 6, the desulfurization tower 7, the compression device 8 and the gas storage tank 9; the outlet of the air separation unit 10 is divided into two branches, one branch After passing through the heat pipe heat exchanger 5, it is connected with the air inlet 2-1 of the cyclone melting furnace 2, and another branch is connected with the inlet of the fluidized bed gasification reactor 1 after passing through the heat pipe heat exchanger 5. The tuyere 1-2 is connected; the economizer 4 is provided with a water inlet, which passes through the economizer 4 and the superheater 3 successively through the water inlet pipe and connects with the fluidized bed gasification reactor 1 The steam inlet 1-3 is connected.

As shown in Figure 1, the biomass raw material A is sent into the fluidized bed gasification reactor 1 by the feeder 1-1, and the oxygen-enriched gas B separated by the air separation unit 10 is preheated and then passed through the air inlet 1-2 , enter the gasification reaction zone through the air chamber 1-4 and the air distribution plate 1-5, and steam C is introduced into the steam inlet 1-3. The temperature of the fluidized bed gasification reactor 1 is 450-750°C. The crude combustible gas D obtained by gasification and reforming is transported from the upper part of the fluidized bed to the cyclone melting furnace 2, and the bottom slag E is discharged through the slag outlet 1-6. The oxygen-enriched gas B is fed through the air inlet 2-1, and the temperature of the cyclone melting furnace 2 is 1100-1450°C, and the tar, carbon particles and ash are removed from the crude combustible gas in a high-temperature environment. The slag G produced by high-temperature melting is discharged from the slag outlet 2-2, and the purified high-temperature combustible gas F is discharged from the upper part of the cyclone melting furnace 2, and flows through the heater 3, the economizer 4 and the heat pipe heat exchanger 5 in sequence. The feed water H enters the superheater 3 after being preheated by the economizer 4, and the steam C generated by heating is passed into the fluidized bed gasification reactor 1. The oxygen-enriched gas B is passed into the fluidized bed gasification reactor 1 and the cyclone melting furnace 2 after being exchanged by heat pipes. After heat exchange, the low-temperature combustible gas K flows through the bag filter 6 and the desulfurization tower 7 for further purification, and the purified combustible gas L is compressed by the compression device 8 and collected in the gas storage tank 9 .

As stated above, while the invention has been shown and described with reference to certain preferred embodiments, this should not be construed as limiting the invention itself. Various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (7)

1. A device for producing high calorific value clean combustible gas by gasification and melting of biomass, characterized in that it includes a fluidized bed gasification reactor (1), a cyclone melting furnace (2), a superheater (3), a coal-saving device (4), heat pipe heat exchanger (5), bag filter (6), desulfurization tower (7), compression device (8) and gas storage tank (9); The fluidized bed gasification reactor (1) is composed of a gasification reaction zone and an air chamber (1-4) at the bottom, and a cloth is arranged between the air chamber (1-4) and the gasification reaction area. The wind plate (1-5), the side wall and the bottom of the air chamber (1-4) are respectively provided with an air inlet (1-2) and a slag discharge port (1-6); the fluidized bed is gasified The sidewall of the gasification reaction zone of the reactor (1) is provided with a steam inlet (1-3) and a feeder (1-1); the gasification reaction of the fluidized bed gasification reactor (1) The top of the zone is connected with the inlet of the cyclone melting furnace (2) by a pipeline; The side wall and the bottom of the cyclone melting furnace (2) are respectively provided with an air inlet (2-1) and a slagging outlet (2-2); the top outlet of the cyclone melting furnace (2) is sequentially connected with the superheater (3), economizer (4) is connected with heat pipe heat exchanger (5); The outlet of the heat pipe heat exchanger (5) is sequentially connected with the dust remover (6), desulfurization tower (7), compression device (8) and gas storage tank (9). 2. The device for producing high calorific value clean combustible gas by gasification and melting of biomass according to claim 1, characterized in that: it also includes an air separation device (10), the outlet of the air separation device (10) is divided into two One branch is connected with the air inlet (2-1) of the cyclone melting furnace (2) after passing through the heat pipe heat exchanger (5), and the other branch passes through the heat pipe heat exchanger (5) ) is connected with the air inlet (1-2) of the fluidized bed gasification reactor (1). 3. The device for producing clean combustible gas with high calorific value by gasification and melting of biomass according to claim 1, characterized in that: the economizer (4) is provided with a water inlet, and the water inlet pipeline passes through the The economizer (4) and the superheater (3) are connected to the steam inlet (1-3) of the fluidized bed gasification reactor (1). 4. A method for producing high calorific value clean combustible gas by gasification and melting of biomass, characterized in that it comprises the following steps: (1) Feed biomass raw materials, oxygen-enriched gas and water vapor into the fluidized bed gasification reactor, generate crude combustible gas under the condition of 450-750°C, and then use the fluidized bed gasification reactor The upper part of the furnace is transported to the cyclone melting furnace; the bottom slag generated by the reaction is discharged from the slag outlet of the fluidized bed gasification reactor; (2) After the crude combustible gas enters the cyclone melting furnace, the oxygen-enriched gas is introduced into the cyclone melting furnace at the same time, and the tar and carbon particles are removed from the crude combustible gas under the condition of 1100-1450°C The high-temperature combustible gas that has been purified with ash is discharged from the upper part of the cyclone melting furnace, and flows through the heater, economizer and heat pipe heat exchanger in sequence; the slag generated by the reaction is discharged from the slag outlet of the cyclone melting furnace discharge; (3) The low-temperature combustible gas from the heat pipe heat exchanger flows through the bag filter and the desulfurization tower for further purification. After purification, the purified combustible gas is compressed by the compression device and collected in the gas storage tank. 5. The method for producing high calorific value clean combustible gas by gasification and melting of biomass according to claim 4, characterized in that: in step (1) and step (2), the oxygen concentration of the oxygen-enriched gas is 25- 95% and preheated to above 200°C. 6. The method for producing high calorific value clean combustible gas by gasification and melting of biomass according to claim 4 or 5, characterized in that: in step (1) and step (2), the oxygen-enriched gas is passed through by air It is obtained after purification by an air separation unit and heated to above 200°C by a heat pipe heat exchanger. 7. The method for producing clean combustible gas with high calorific value by gasification and melting of biomass according to claim 4, characterized in that: in step (1), the steam is preheated by water through an economizer, and enters It is obtained by reheating and vaporizing the superheater.