CN1865408A - Method for preparing fuel gas by fluidized bed co-gasification of biomass and coal - Google Patents

Abstract

A method for co-gasifying biomass and coal fluidized bed to prepare fuel gas is to crush the biomass to a particle size of less than 5mm, and mix the coal to a particle size of less than 2mm; heat the gasifier to 700-800°C, and The mixture of biomass and coal is fed into the gasifier, and air and water vapor are introduced to keep the temperature in the gasifier at 900-1100°C to generate tar-free fuel gas. The invention has the advantages of no tar generation, simple process, easy realization of large-scale production, large gas production and high production efficiency.

Description

A method for preparing fuel gas by co-gasification of biomass and coal fluidized bed

technical field

The invention belongs to a method for preparing clean fuel gas, in particular to a method for co-gasifying a mixture of biomass and coal to prepare fuel gas.

Background technique

With the decrease of fossil energy, biomass, as an important renewable energy, has attracted the attention of all countries in the world. Biomass fluidized bed gasification technology is an important way to effectively utilize biomass energy. Biomass has high content of volatile components, high carbon reactivity, low content of sulfur, nitrogen and ash, and is more suitable as gasification raw material; There are some disadvantages in separate gasification of materials. First, biomass production is seasonal and cannot be supplied stably. Second, due to the irregularity of biomass particles, it cannot be fluidized independently in a fluidized bed, and bed materials need to be added, such as Sand, which increases power consumption; third, the low energy density of biomass leads to low gasification temperature, generally between 600 and 800°C, so a large amount of tar will be produced, which will be deposited in or even block the pipeline or post-system equipment. Improper treatment of discharged tar can easily cause secondary pollution. Co-gasification of biomass and coal can well make up for the defects of biomass gasification alone: ① Coal can be supplied stably to make up for the seasonal defects of biomass production; ② Coal is used as bed material to solve the flow problem of biomass; ③ Co-gasification of coal and biomass can increase the gasification temperature to above 900°C, thereby avoiding the generation of tar. At present, someone in China has proposed a process flow for intermittent operation of coal and biomass fluidized bed air supply combustion and steam gasification (public number CN 1557919A). In the air supply combustion stage, coal and air are introduced to make the coal in Combustion in a fluidized state generates heat; in the steam gasification stage, water vapor and biomass are fed into the gasifier, and fuel gas with high calorific value can be obtained during the process without tar generation. The process adopts the intermittent operation of air supply combustion and steam supply gasification, and uses the high-temperature material bed generated by coal combustion to gasify coal and biomass, which improves the calorific value of fuel gas, avoids the generation of tar, but reduces production Efficiency increases the complexity of the operation. Moreover, the intermittent operation method makes the valves that control the air supply combustion and steam supply operation switch frequently, which requires high material requirements for the valves and increases the difficulty of industrial application.

Contents of the invention

The object of the present invention is to provide a method for producing fuel gas through continuous co-gasification of biomass and coal without tar generation and simple process.

The purpose of the present invention is achieved like this: the biomass does not need to be sorted and purified, it is crushed to a particle size less than 5mm, and then mixed with coal with a particle size of less than 2mm, and the mass percentage of the biomass in the mixture is 5-50%. The mixture is put into the gasification furnace, and air and steam are passed through, and the temperature of the gasification furnace is controlled at 900-1100°C to obtain tar-free fuel gas.

The method for preparing fuel gas by biomass and coal co-gasification of the present invention comprises the following steps:

1. Crushing the biomass until the particle size is less than 5mm, and crushing the coal until the particle size is less than 2mm, and then mixing the two, the mass percentage of biomass in the mixture is 5-50%;

2. Heat the gasifier to 700-800°C, put the mixture of biomass and coal into the gasifier, feed air and steam, and mix the total amount of air into the furnace with the raw material of the mixture of biomass and coal The ratio is 2.1-3.6Nm ³ air/kg mixture, the ratio of water vapor to biomass and coal mixture raw material is 0.1-0.6kg water vapor/kg mixture, and the temperature in the gasifier is kept at 900-1100°C to generate no Fuel gas containing tar.

Compared with the prior art, the present invention has the following advantages:

(1) Biomass and coal co-gasification are complementary in terms of physical properties and gasification performance. The supply of coal is relatively stable, which can make up for the seasonal shortage of biomass production; the density of biomass particles is small, and it is easy to be carried out of the bed, resulting in incomplete reaction. The problem of stable fluidization, and can inhibit the biomass particles from being taken out, prolonging the residence time in the bed; the volatile content of biomass is relatively high, the carbon reactivity is high, and the coal particles form a high-temperature material layer, which is conducive to the biomass. Gasification reaction, complementary and synergistic effects can occur between the two;

(2) The method for preparing fuel gas of the present invention does not produce tar, and the process is simple, and it is easy to realize large-scale production;

(3) The preparation of raw materials is simple and the source is abundant. Coal is widely distributed in my country and has large reserves, while biomass does not need to be sorted and is easy to process. Co-gasification can improve the economics of the process;

(4) The process can be produced continuously for a long time, with large gas production and high production efficiency;

(5) The calorific value of the fuel gas produced is 3.0-4.8MJ/Nm ³ .

The content of the present invention will be further elaborated below in conjunction with the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is a flow chart of the present invention.

As shown in the figure, 1 material bin with stirring device 2 distilled water storage tank 3 speed regulating motor 4 screw feeder 5 metering pump 6 steam generator 7 air compressor 8 casing heat exchanger 9 cyclone separator 10 gasifier 11 Distribution plate 12 Center pipe 13 Ash hopper 14 Valve 15 Washing tower 16 Gas-liquid separator 17 Gas cabinet.

Detailed ways

Example 1

The mixture of rice straw and coal is used as raw material for gasification. The rice straw does not need to be sorted and purified. It is crushed to a particle size of less than 5mm and mixed with coal particles with a particle size of less than 2mm. The mass percentage of straw in the mixture is 5%. The material is added to the silo 1 with a stirring device for use. Insert the flame spray gun into the furnace from the bottom of the gasification furnace 10, feed in the liquefied gas and the air required for complete combustion, heat the gasification furnace 10 to 700-800°C, stop heating, turn on the speed regulating motor 3, and feed through the screw The device 4 puts the mixed material into the gasifier 10, and the compressed air generated by the air compressor 7 enters the gasifier 10 through the distribution plate 11 and the central pipe 12 respectively, and the total amount of air entering the furnace is equal to the mixture raw material of biomass and coal. The proportion is 2.2Nm ³ air/kg mixture. After the material is burned until the furnace temperature is stable, the metering pump 5 and the steam generator 6 are turned on, and the distilled water in the distilled water storage tank 2 is injected into the gasification through the distribution plate 11 in the form of steam. Furnace 10, the steam temperature is 300°C, the ratio of water vapor to biomass and coal mixture raw material is 0.6kg water vapor/kg mixture. The crude fuel gas produced comes out from the top of the gasifier 10, is cooled by the casing heat exchanger 8, enters the cyclone separator 9, and then is purified by the water washing tower 15 and the gas-liquid separator 16 in turn, and then enters the gas cabinet 17 for use by users . The cyclone ash and slag enter the ash hopper 13-1 and the ash hopper 13-2 respectively, and then are discharged through the valve 14-1 and the valve 14-2 respectively. The indicators of the fuel gas produced are as follows:

Gasifier temperature: 960-1050°C

Typical fuel gas composition: N ₂ 53.64-61.46 CO ₂ 11.38-13.71 H ₂ 11.59-9.13 CO 21.91-14.38 CH ₄ 1.48-1.32

High calorific value of fuel gas: 3.5MJ/Nm ³ -4.8MJ/Nm ³

System carbon conversion rate: 70%-90%

Example 2

The mixture of rice straw and coal is used as raw material for gasification. The rice straw does not need to be sorted and purified. It is crushed to a particle size of less than 5mm and mixed with coal particles with a particle size of less than 2mm. The mass percentage of rice straw in the mixture is 33%. The material is added to the silo 1 with a stirring device for use. Insert the flame spray gun into the furnace from the bottom of the gasification furnace 10, feed in the liquefied gas and the air required for complete combustion, heat the gasification furnace 10 to 700-800°C, stop heating, turn on the speed regulating motor 3, and feed through the screw The device 4 puts the mixed materials into the gasifier 10, and the compressed air generated by the air compressor 7 enters the gasifier 10 through the distribution plate 11 and the central pipe 12 respectively, and the total amount of air entering the furnace is equal to the mixture raw material of biomass and coal. The proportion is 2.8Nm ³ air/kg mixture. After the material is burned until the furnace temperature is stable, the metering pump 5 and the steam generator 6 are turned on, and the distilled water in the distilled water storage tank 2 is injected into the gasification through the distribution plate 11 in the form of steam. Furnace 10, the steam temperature is 300°C, the ratio of water vapor to biomass and coal mixture raw material is 0.3kg water vapor/kg mixture. The crude fuel gas produced comes out from the top of the gasifier 10, is cooled by the casing heat exchanger 8, enters the cyclone separator 9, and then is purified by the water washing tower 15 and the gas-liquid separator 16 in turn, and then enters the gas cabinet 17 for use by users . The cyclone ash and slag enter the ash hopper 13-1 and the ash hopper 13-2 respectively, and then are discharged through the valve 14-1 and the valve 14-2 respectively. The indicators of the fuel gas produced are as follows:

Gasifier temperature: 900-950°C

Typical fuel gas composition: N ₂ 55.23-62.33 CO ₂ 12.46-13.91 H ₂ 10.62-9.09 CO 20.17-13.26 CH ₄ 1.52-1.41

High calorific value of fuel gas: 3.4MJ/Nm ³ -4.5MJ/Nm ³

System carbon conversion rate: 70%-90%

Example 3

The mixture of rice straw and coal is used as the raw material for gasification. The rice straw does not need to be sorted and purified. It is crushed to a particle size of less than 5mm and mixed with coal particles with a particle size of less than 2mm. The mass percentage of rice straw in the mixture is 50%. The material is added to the silo 1 with a stirring device for use. Insert the flame spray gun into the furnace from the bottom of the gasification furnace 10, feed in the liquefied gas and the air required for complete combustion, heat the gasification furnace 10 to 700-800°C, stop heating, turn on the speed regulating motor 3, and feed through the screw The device 4 puts the mixed materials into the gasifier 10, and the compressed air generated by the air compressor 7 enters the gasifier 10 through the distribution plate 11 and the central pipe 12 respectively, and the total amount of air entering the furnace is equal to the mixture raw material of biomass and coal. The proportion is 3.5Nm ³ air/kg mixture. After the material is burned until the furnace temperature is stable, the metering pump 5 and the steam generator 6 are turned on, and the distilled water in the distilled water storage tank 2 is injected into the gasification through the distribution plate 11 in the form of steam. Furnace 10, the steam temperature is 300°C, the ratio of water vapor to biomass and coal mixture raw material is 0.1kg water vapor/kg mixture. The crude fuel gas produced comes out from the top of the gasifier 10, is cooled by the casing heat exchanger 8, enters the cyclone separator 9, and then is purified by the water washing tower 15 and the gas-liquid separator 16 in turn, and then enters the gas cabinet 17 for use by users . The cyclone ash and slag enter the ash hopper 13-1 and the ash hopper 13-2 respectively, and then are discharged through the valve 14-1 and the valve 14-2 respectively. The indicators of the fuel gas produced are as follows:

Gasifier temperature: 920-980°C

Typical fuel gas composition: N ₂ 58.43-64.17 CO ₂ 14.32-15.32 H ₂ 9.81-8.26 CO 15.84-10.76 CH ₄ 1.60-1.49

High calorific value of fuel gas: 3.0MJ/Nm ³ -3.9MJ/Nm ³

System carbon conversion rate: 80%-95%

Claims (1)

1, a kind of biomass and the fluidized bed method of preparing fuel gas by gasifying altogether is characterized in that comprising the steps:

(1), biomass are crushed to granularity less than 5mm, coal is crushed to granularity less than 2mm, and mixed both then, the mass percent of biomass in miscellany is 5-50%;

(2), vapourizing furnace is warmed 700-800 ℃, the mixture of biomass and coal is joined in the vapourizing furnace, bubbling air and water vapour, the proportioning of going into the mixture material of stove air total amount and biomass and coal is 2.1-3.6Nm3 air/kg mixture, steam vapour amount and biomass and coal mixtures proportion of raw materials are 0.1-0.6kg water vapour/kg mixture, keeping the interior temperature of vapourizing furnace is 900-1100 ℃, generates the fuel gas that does not contain tar.

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