CN203307297U - A three-stage biomass gasification device for producing combustible gas with low tar and high calorific value - Google Patents

Abstract

The utility model discloses a device for preparing low-tar and high-heating-value combustible gas by biomass three-stage gasification, which consists of a fluidized bed gasification reactor, a cyclone reforming reactor, a moving bed catalytic reactor and a material returning device, wherein the upper part of the fluidized bed gasification reactor is communicated with the upper part of the cyclone reforming reactor, the lower part of the fluidized bed gasification reactor is communicated with the lower part of the moving bed catalytic reactor through the material returning device, and the top of the cyclone reforming reactor is communicated with the top of the moving bed catalytic reactor; the lower part of the fluidized bed gasification reactor is also provided with a biomass particle feeding port and a first oxygen-enriched/steam inlet; the upper part of the cyclone reforming reactor is provided with a second oxygen-enriched/steam inlet; the bottom of the material returning device is provided with a third oxygen-enriched/steam inlet. The utility model discloses can effectively solve the problem that the product gas calorific value that exists is low, tar concentration is high among the present biomass gasification technology, prepare multiple high-quality combustible gas that can directly be applied to gas equipment. The system can be operated in a self-heating mode, the gasification cost is low, and the energy utilization rate is high.

Description

A three-stage biomass gasification device for producing combustible gas with low tar and high calorific value

technical field

The utility model relates to a device and method for producing combustible gas with low tar and high calorific value through three-stage gasification of biomass, which belongs to the field of solid waste resource disposal.

Background technique

With the improvement of my country's urbanization level, the demand for rural energy has increased and the energy structure has changed. The energy consumption of rural households has changed from traditional fuels such as straw and firewood to clean natural gas and liquefied petroleum gas fuels. Biomass resources have become regionalized. , seasonal and structural excesses. A large amount of biomass is directly incinerated, which not only wastes precious resources, but also seriously pollutes the environment. Therefore, how to solve the way out of biomass disposal and realize the efficient recycling of biomass energy has become a major problem to be solved urgently in the construction of new socialist countryside in our country.

Gasification is the thermochemical conversion of solid fuels into combustible gases. Biomass gasification technology only needs a small amount of agricultural and forestry waste to produce flammable gas, which can solve the problems of difficult biomass treatment and popularization of natural gas in rural areas, and can alleviate the energy shortage in the current rural economic development process and reduce environmental pollution and waste of resources are of great strategic importance.

Existing biomass gasification reactors include fixed bed, fluidized bed and entrained bed and other types. The fixed-bed gasifier has simple structure, low investment, and convenient operation, but its production scale is small and its continuous operation performance is poor; entrained-bed oxygen gasification can produce combustible gas with medium tar content and high carbon conversion rate, and the investment cost Higher, suitable for very large-scale gasification units. Compared with fixed bed or entrained bed gasification, fluidized bed gasification has the advantages of high heat and mass transfer rate, wide fuel applicability, high economy, easy scale-up and large-scale, etc., and has attracted more and more attention.

The existing fluidized bed gasification reactor has the problems of high tar concentration and low calorific value of the gas produced, and the gas produced by gasification needs to add expensive follow-up purification treatment equipment before it can be used. Raising the gasification temperature can promote tar cracking, but at the same time increases the risk of ash slagging and reduces gasification efficiency; the concentration of tar can be reduced by optimizing the gasification agent composition, but it still cannot meet the requirements of direct replacement of combustible gas; Due to the influence of fluid dynamics and the limitations of catalysts with low mechanical strength, poor thermal stability, and easy poisoning and deactivation in the bed, it is difficult to apply; staged gasification is currently mainly used in fixed-bed gasification systems, but fluidized-bed gasification Staged gasification is more conducive to improving gasification gas production and gas quality.

Contents of the invention

technical problem:

Aiming at the problems of low calorific value of gas production and high tar concentration in the current biomass gasification technology, the utility model proposes a three-stage gasification that separates biomass pyrolysis, tar reforming and coke gasification The device can produce combustible gas with low tar and high calorific value, and has high gasification efficiency.

Technical solutions:

The device for producing low tar and high calorific value combustible gas by biomass three-stage gasification of the utility model is composed of a fluidized bed gasification reactor, a cyclone reforming reactor, a moving bed catalytic reactor and a feeder. The upper part of the bed gasification reactor is connected with the upper part of the cyclone reforming reactor, the lower part of the fluidized bed gasification reactor is connected with the lower part of the moving bed catalytic reactor through the feeder, and the top of the cyclone reforming reactor is connected with the moving bed catalytic reactor The top of the fluidized bed gasification reactor is connected; the lower part of the fluidized bed gasification reactor is also equipped with a biomass particle feed port and the first oxygen-enriched/steam inlet, and the bottom of the fluidized bed gasification reactor is provided with a slag discharge port; the cyclone reforming reaction The upper part of the reactor is the second oxygen-enriched/steam inlet, and the bottom of the cyclone reforming reactor is a liquid slag outlet; the lower part of the moving bed catalytic reactor is equipped with a coke inlet and a combustible gas outlet, and the bottom of the moving bed catalytic reactor is equipped Ash port; the bottom of the feeder is the third oxygen-enriched/water vapor inlet.

The utility model produces the method for low-tar high calorific value combustible gas, comprises the following steps:

(1) Feed biomass raw materials, oxygen-enriched/water vapor into the fluidized bed gasification reactor, and generate crude combustible gas and pyrolysis coke under the condition of 600~800°C, and the crude combustible gas is gasified by the fluidized bed The upper part of the reactor is transported to the cyclone reforming reactor, and the pyrolysis coke is transported from the lower part of the fluidized bed gasification reactor to the moving bed catalytic reactor through the feeder. Continuous transportation, the bottom slag generated by gasification is discharged from the slag outlet of the fluidized bed gasification reactor;

(2) After the crude combustible gas enters the cyclone reforming reactor, oxygen-enriched/water vapor is introduced into the second oxygen-enriched/steam inlet at the same time. Under the condition of 1200~1400℃, the crude combustible gas is removed The high-temperature combustible gas in which the tar and ash have been purified is transported from the upper part of the cyclone reforming reactor to the moving bed catalytic reactor, and the molten slag generated by the reaction is discharged from the liquid slag outlet of the cyclone reforming reactor;

(3) Pyrolysis coke is accumulated in the moving bed catalytic reactor to form a coke bed layer. After the reformed high-temperature combustible gas enters the moving bed catalytic reactor, the tar is further cracked and removed under the coke catalytic atmosphere at 700~900°C. Pyrolysis coke is reduced by _CO2 and water vapor in the high-temperature combustible gas to generate CO, and the low-tar high-calorific value combustible gas obtained after catalytic reduction is discharged from the combustible gas outlet at the lower part of the moving bed catalytic reactor, and the ash generated by gasification is discharged from the bottom Mouth discharge.

The reaction temperature of the fluidized bed gasification reactor is 750°C, the reaction temperature of the cyclone reforming reactor is 1200°C, and the reaction temperature of the moving bed catalytic reactor is 880°C.

The oxygen-enriched/water vapor fed is a mixed gas of oxygen-enriched gas and water vapor, the ratio of the mixed gas is 1:1~5:1, the concentration of oxygen-enriched gas is 40%; the water vapor temperature is 400~500°C.

The three-stage gasification method of the utility model for producing combustible gas with low tar and high calorific value, the biomass particles are added into the fluidized bed, and the biomass particles are vigorously mixed with water vapor and oxygen-enriched gas, resulting in intense heat and mass exchange , so that the biomass particles in the bed quickly rise to the temperature in the bed, the cellulose in the biomass thermally decomposes volatile substances and tar, and the lignin decomposes to produce coke particles. The crude combustible gas carrying a large amount of tar and ash is sent from the upper part of the fluidized bed to the cyclone reforming reactor, and the coke is sent from the lower part of the fluidized bed through the feeder to the moving bed catalytic reactor to be used as a catalyst. Oxygen-enriched gas and water vapor are fed into the bottom of the feeder to adjust the delivery rate, ensuring continuous delivery of coke particles and avoiding gas backflow. In the cyclone reforming reactor, part of the crude combustible gas undergoes combustion reaction with oxygen-enriched gas to maintain a reforming high-temperature atmosphere. The primary tar is completely cracked and removed through high-temperature cracking and steam reforming reactions, and the ash is melted at high temperature to form liquid ash. The slag outlet is discharged. The heavy metals in the ash can be stably dissolved in the slag, and the slag can be directly landfilled or used as building and roadbed materials. Pyrolysis coke is sent to the moving bed catalytic reactor to accumulate into a coke bed layer, and the reformed high-temperature combustible gas is sent from the top of the moving bed and transfers heat to the moving bed. The tar is in full contact with the coke and is catalytically cracked into a small molecular gas. At the same time, the coke is reformed by the water vapor and _CO2 in the combustible gas to generate CO, and the cleanliness and calorific value of the gas are improved. In the inventive device, through the adjustment of gasification agent components and operating parameters in each stage of the three-stage gasification, combustible gases with different properties can be obtained to meet the requirements of various gas applications such as engines, gas turbines, and chemical synthesis. The combustion of oxygen-enriched gas and combustible gas can provide heat for the system and realize the self-heating operation of the system.

Beneficial effect:

Conventional fluidized bed gasification technology has a low carbon conversion rate and high gas tar concentration, making subsequent gas purification difficult. The utility model combines the technical advantages of existing high-temperature gasification, oxygen-enriched/steam reforming, segmented gasification and catalytic cracking, and proposes a new three-stage biomass gasification device for producing low-tar, high-calorific-value combustible gas and The method separates the processes of biomass pyrolysis, tar reforming and coke gasification, which can effectively improve the conversion rate of tar and coke. The three-stage gasification simulation results show that when the fluidized bed temperature is 750°C, the cyclone reforming reactor temperature is 1200°C, and the moving bed temperature is 880°C, the three-stage gasification efficiency can reach 81%, and the coke conversion rate It is 98%, and the tar content in the gas is as low as 10mg/Nm ³ . Therefore, the utility model can reduce the secondary purification cost of combustible gas, and realize the direct application of gas production on gas equipment.

1. Fluidized bed gasification is suitable for a variety of fuels of different qualities and is easy to scale up. Through medium and low temperature pyrolysis gasification, the unstable operation of the fluidized bed caused by ash slagging in biomass can be avoided. The use of oxygen-enriched/steam gas It is converted into crude combustible gas and pyrolysis coke containing more tar. Oxygen-enriched gasification can improve the gasification reaction rate and gasification efficiency, and provide heat for the steam reforming reaction, reducing the use of external heat sources. Steam reforming can help reduce tar production. Pyrolysis coke has a high carbon content and can be used as a good tar cracking catalyst.

2. The cyclone reforming reactor reforms the tar in the crude combustible gas under the high temperature + water vapor atmosphere, and the introduction of water vapor can prevent the coking of the reforming reactor and the secondary polymerization of the tar. The ash is melted at high temperature into liquid ash, effectively solidifying pollutants such as heavy metals, and the slag can be directly landfilled or recycled as construction and roadbed materials. The high-temperature atmosphere of the reactor is maintained by burning oxygen-rich gas and part of the crude combustible gas to release heat, which reduces the use of fossil fuels and reduces operating costs.

3. Pyrolysis coke is directly used for catalytic cracking of tar in the moving bed, which can further reduce the concentration of tar, save the cost of catalyst use, and also solve the problems of short contact time between tar and coke and poor catalytic effect in fluidized bed gasification. At the same time, coke can be further gasified by water vapor and CO ₂ to generate CO, and the conversion rates of tar and coke are both improved.

4. The feeder is used to realize the continuous transfer of pyrolysis coke from the fluidized bed gasification reactor to the moving bed catalytic reactor, effectively avoiding the back channeling of gas. Oxygen-enriched gas and water vapor are fed into the bottom of the feeder to adjust the delivery volume to ensure the continuous delivery of coke particles. According to the difference of fuel activity and ash content, the feeder can be used as a small burner (passing oxygen-enriched gas) or a reforming reactor (passing water steam) to meet the requirements of changing operating conditions of the system.

5. Adopting a three-stage gasification system combining fluidized bed, high-temperature reforming and moving bed, the operation is flexible and convenient, and various types of combustible gas can be obtained by adjusting the gasification agent components and operating conditions of each stage , to meet the requirements of different gas applications such as gas turbines, engines and chemical preparation. Compared with fixed-bed staged gasification, it has a larger production capacity, is more suitable for medium-scale or large-scale industrial production, and has a good prospect for commercial application.

6. The oxygen concentration of oxygen-enriched gas used in gasification and reforming is about 40%, which can be obtained by oxygen-enriched membrane oxygen production method, and the cost of oxygen production is low. The introduction of oxygen-enriched gas provides the required heat for the fluidized bed and reforming reactor, and the heat of the reformed high-temperature combustible gas is transferred to the moving bed to maintain the temperature required for catalysis, and the entire gasification system can realize self-heating operation.

Description of drawings

Fig. 1 is a schematic flow chart of the three-stage biomass gasification process of the present invention.

Figure 2 is a graph of gasification characteristics as a function of temperature.

Among them are fluidized bed gasification reactor 1, screw feeder 1-1, air chamber 1-2, air distribution plate 1-3, cyclone reforming reactor 2, moving bed catalytic reactor 3, feeder 4, The first oxygen-enriched/steam inlet A, the biomass pellet feeding port B, the slag outlet C, the second oxygen-enriched/steam inlet D, the liquid slag outlet E, the coke inlet F, and the combustible gas outlet G , Ash outlet H, third oxygen-enriched/steam inlet I.

Detailed ways

The biomass three-stage gasification device provided by the utility model to produce low-tar high-calorific-value combustible gas is mainly composed of a fluidized bed gasification reactor 1, a cyclone reforming reactor 2, a moving bed catalytic reactor 3, and a return material Device 4 is composed. The upper part of the fluidized bed gasification reactor 1 communicates with the upper part of the cyclone reforming reactor 2, the lower part communicates with the lower part of the moving bed catalytic reactor 3 through the feeder 4, and the top of the cyclone reforming reactor 2 communicates with the moving bed catalytic reactor 3 connected at the top. The lower part of the fluidized bed gasification reactor 1 is also equipped with a biomass particle feeding port B and a first oxygen-enriched/steam inlet A, and a slag discharge port C is provided at the bottom; the upper part of the cyclone reforming reactor 2 is a second Oxygen-enriched/steam inlet D, the bottom is a liquid slag outlet E; the lower part of the moving bed catalytic reactor 3 is provided with a coke inlet F and a combustible gas outlet G, and the bottom is provided with an ash outlet H; the bottom of the feeder 4 is Third oxygen-enriched/steam inlet I.

The specific process of the preparation method is as follows: the biomass particles are fed through the screw feeder 1-1 from the biomass particle feeding port B, the oxygen-enriched/steam gasification agent is introduced from the first oxygen-enriched/steam inlet A, Biomass particles and oxygen-enriched/steam undergo pyrolysis gasification reaction in the fluidized bed gasification reactor 1 . The cellulose in the biomass is thermally decomposed to release volatile matter and tar, and the lignin is decomposed to form coke particles, and the ash is discharged through the slag discharge port C. The crude combustible gas produced by gasification leaves from the upper part of the fluidized bed gasification reactor 1 with tar and ash, and enters the cyclone reforming reactor 2 . The coke particles generated by gasification flow into the feeder 4, and under the action of the oxygen-enriched/steam introduced from the third oxygen-enriched/steam inlet I, the coke particles are sent into the moving bed catalytic reactor through the coke inlet F 3 as a catalyst. The oxygen-enriched/steam introduced from the second oxygen-enriched/steam inlet D of the cyclone reforming reactor 2 is fully mixed with the crude combustible gas for reforming, and the tar can be cracked at high temperature or further generated with water vapor The liquid ash generated by the high-temperature melting of the fly ash in the combustible gas is discharged through the liquid slag outlet E. The high-temperature combustible gas coming out of the cyclone reforming reactor 2 enters the moving bed catalytic reactor 3, flows through the bed layer of coke accumulation and is further purified. The tar is in full contact with the coke and is catalytically cracked. The coke is reduced to CO under the action of water vapor and _CO2 . The clean combustible gas is discharged from the combustible gas outlet G at the lower part of the moving bed, and the residual ash is discharged from the bottom ash discharge port H.

In the whole three-stage biomass gasification process, the fluidized bed gasification reactor is in the medium temperature state of 600~800°C, the cyclone reforming reactor is in the high temperature state of 1200~1400°C, and the moving bed catalytic reactor is passed through the high temperature combustible gas The heat transfer maintains a medium temperature of 700~900°C. The pyrolysis gas is reformed with high-temperature steam to remove tar, and the pyrolyzed coke is sent to the moving bed catalytic reactor as a catalyst to separate the biomass pyrolysis, tar reforming and coke gasification processes, and provide heat for the system through oxygen-enriched oxidation , to realize the self-heating operation of the system.

Figure 2 shows the gasification efficiency, coke conversion rate, and tar content in the gas produced by simulation as a function of gasification temperature. The simulation results show that the gasification efficiency and coke conversion rate increase gradually with the increase of temperature, and the gasification efficiency reaches more than 80% and the coke conversion rate can reach more than 90% when the temperature is above 1000 °C; the tar production decreases significantly with the increase of temperature, It decreases to 10mg/Nm ³ at around 1200°C. Due to the restriction that the fluidized bed temperature is too high, it is easy to coke and block, the gasification temperature in the previous gasification process is generally controlled below 820°C, resulting in low gasification efficiency and coke conversion rate, and high tar yield, which affects the gasification gasification process. of direct use. Through the three-stage gasification method, the biomass gasification temperature can be increased to 1200-1400 °C while avoiding coking, the gasification efficiency and coke conversion rate can reach a high level, and the tar production will also be greatly reduced.

Claims (1)

1. A three-stage biomass gasification device for producing combustible gas with low tar and high calorific value, which consists of a fluidized bed gasification reactor (1), a cyclone reforming reactor (2), a moving bed catalytic reactor (3 ) and a feeder (4), characterized in that: the upper part of the fluidized bed gasification reactor (1) communicates with the upper part of the cyclone reforming reactor (2), and the lower part of the fluidized bed gasification reactor (1) passes through The feeder (4) communicates with the lower part of the moving bed catalytic reactor (3), and the top of the cyclone reforming reactor (2) communicates with the top of the moving bed catalytic reactor (3); the fluidized bed gasification reactor (1 ) is also equipped with a biomass particle feed port (B) and the first oxygen-enriched/steam inlet (A), and a slag discharge port (C) is provided at the bottom of the fluidized bed gasification reactor (1); The upper part of the whole reactor (2) is the second oxygen-enriched/steam inlet (D), the bottom of the cyclone reforming reactor (2) is the liquid slagging outlet (E); the lower part of the moving bed catalytic reactor (3) is There is a coke inlet (F) and a combustible gas outlet (G), and the bottom of the moving bed catalytic reactor (3) is equipped with an ash outlet (H); the bottom of the feeder (4) is the third oxygen-enriched/steam inlet (I).

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