CN100410352C - A gasification process and device for co-gasification of biomass and coal - Google Patents

Abstract

The invention relates to energy equipment, in particular to a gasification process and its device for generating low calorific value gas by mixed gasification of biomass and coal in a fluidized bed. This method is based on air and adding a small amount of water vapor as gasification agent. The proportion of air to the total amount of coal and biomass added is 1.2-2.0m ³ /Kg, and the proportion of water vapor to the total amount of coal and biomass added is 0.2-0.3Kg/Kg. Gasification raw materials are 0-10mm powdered biomass and 0-6mm pulverized coal. The ratio of biomass/coal is selected between 40/60-80/20. The two raw materials are respectively fed into the biomass fluidized bed gasification furnace through two special feeding devices, the working temperature is 850-950°C, and the fluidization velocity is 0.8-1.2m/s. The generated crude gas is firstly dedusted by the high-temperature cyclone separator, and the separated carbon-containing dust is sent into the ash storage box through the feeding pipe. After the initial dedusting gas is heat-exchanged by the steam generator, the temperature drops below 300°C, enters the purification system for further washing and dedusting, and is sent to the gas cabinet for use. It basically produces no tar, and the process is simple.

Description

A gasification process and device for co-gasification of biomass and coal

technical field

The invention relates to energy equipment, in particular to a gasification process and its device for generating low calorific value gas by mixed gasification of biomass and coal in a fluidized bed.

Background technique

The existing biomass fluidized bed gasifier with air as the gasification agent has the advantages of simple process, low investment, low operating cost, and convenient operation, and is widely used in industry for power generation and heat supply. Due to the small bulk density of biomass, low ash content, high volatile content, low fixed carbon content, and high gasification reactivity, biomass is easy to gasify, but it is difficult to form a stable fluidized material layer. The solution at home and abroad is to fluidize A certain amount of inert particles such as river sand, quartz sand, etc. are added to the bed to establish a stable material layer. Moreover, due to the high volatile content of biomass and low reaction temperature, generally 700-750°C, high-molecular hydrocarbons cannot be cracked into gaseous small molecules, and the product gas contains a large amount of tar, which seriously affects the use of gas. At present, the method of catalytic cracking is used to remove the tar in the gas at home and abroad, but for small and medium-scale biomass gasification plants, there are many problems in terms of economy and operation. In addition, due to the periodicity of biomass growth, it also brings periodicity in the supply of biomass raw materials. This periodicity affects the continuous stability of biomass gasification production. Existing Chinese patents 200420024372.X "biomass gasifier", 200410013943.4 "a biomass and coal mixed fluidized bed gasification method and its device". It adopts two stages of air supply combustion and steam supply gasification, and needs to add two sets of control valves. The control system is relatively complicated, and its gasification products are high and medium calorific value gases, which have different characteristics from the low calorific value gases described in the present invention. application field.

Contents of the invention

The purpose of the present invention is to address the defects of the prior art, and provide a gasification process and device for co-gasification of biomass and coal with low heat value gas, basically without tar generation, simple process, and gasification product.

The technical solution to achieve the above objectives is: using a fluidized bed gasifier as the main equipment, using air and water vapor as the gasification agent, and using powdered biomass and pulverized coal as raw materials, the biomass and gasification process is carried out through the fluidized bed gasifier. Coal pyrolysis gasification reaction, continuous production of low calorific value gas, used for power generation, heating, etc.

This method is based on air and adding a small amount of water vapor as gasification agent. The ratio of air to the total amount of coal and biomass feed is selected within 1.2-2.0m ³ /Kg, and the ratio of water vapor to the total amount of coal and biomass feed is selected within 0.2-0.3Kg/Kg. Gasification raw materials are 0-10mm powdered biomass and 0-6mm pulverized coal. The ratio of biomass/coal can be selected between 40/60-80/20 according to the raw material situation. The two raw materials are fed into the furnace separately through two special feeding devices. The gasification equipment is a fluidized bed gasifier. The operating temperature of the biomass fluidized bed gasifier is 850-950°C, and the fluidization velocity is 0.8-1.2m/s. The generated crude gas is firstly dedusted by the high-temperature cyclone separator, and the separated carbon-containing dust is put into the ash storage box through the feeding pipe for other purposes. After the initial dedusting gas is heat-exchanged by the steam generator, the temperature drops below 300°C, enters the purification system for further washing and dedusting, and is sent to the gas cabinet for use. The air is supplied into the furnace by the Roots blower, a small part of the steam generated by the steam generator is used for gasification, and the rest is supplied externally.

The device for implementing the gasification process includes: biomass fluidized bed gasifier (1), cyclone separator (2), ash storage box (7) and carbon storage box (8), steam generator (3), washing Tower (4). The biomass fluidized bed gasifier (1) is composed of three parts, the upper part is a large cylindrical vertical section, the middle part is an inverted conical extension section, and the lower part is a small cylindrical vertical section. The furnace body is a circular steel plate structure with refractory lining, and the lower part of the furnace body is provided with an air chamber (11), a slag discharge pipe (15) and an air distribution plate (12) in sequence. The biomass fluidized bed gasifier is provided with two feed bins, a coal bunker (9) with a screw feeder and a biomass feed bin (10) with a screw feeder. In the middle part of the lower vertical section of the biomass fluidized bed gasifier, the coal bunker (9) is connected with the biomass fluidized bed gasifier (1) through a screw feeder. A biomass material bin (10) is arranged at the middle and lower part of the extension section to be connected with the biomass fluidized bed gasifier (1) through a screw feeder. Four nozzles (13) are provided on the upper part of the biomass material inlet to supply steam, and a discharge port (14) for biochar is provided on the upper part of the nozzle, and the biochar is discharged into the carbon storage box (8 )Inside. The upper outlet of the furnace body is connected with a high-temperature cyclone separator (2), and the lower end of the cyclone separator (2) is connected with the ash storage box (7) through a feeding pipe; the top outlet of the cyclone separator (2) is connected with the steam generator inlet (3 ) is connected, and its outlet is connected with the washing tower (4). The gas after washing and purifying enters the gas cabinet (5) for use.

Compared with the method of the existing biomass fluidized bed gasifier, the present invention has the following advantages.

(1) The present invention uses pulverized coal (0-6mm) to replace the inert particles of conventional biomass fluidized bed gasifiers, and continuously co-gasifies with biomass in the fluidized bed, cancels the two stages of combustion and gasification, and does not Additional two-stage reversing valves and control systems are required for easy control.

(2) The greenhouse gas emission of biomass is zero, and the content of S and N in biomass is very small. Co-gasification with coal can make full use of coal resources; reduce pollutant emissions and improve the ecological environment.

(3) Biomass is a renewable resource, and due to the periodicity of biomass growth, it brings periodic supply. Co-gasification with coal can use coal to adjust the periodicity of biomass supply to ensure continuous and stable energy supply and reduce coal consumption.

Description of drawings

Figure 1 is a schematic diagram of a biomass fluidized bed gasifier

Fig. 2 is a schematic diagram of the process flow of the present invention

1. Biomass fluidized bed gasifier 2. High temperature cyclone separator 3. Steam generator 4. Washing tower 5. Gas storage cabinet 6. Roots blower 7. Ash storage box 8. Carbon storage box 9. Coal bunker and Spiral coal stoker 10, biomass bin and feeder 11, air chamber 12, air distribution plate 13, steam nozzle 14, carbon discharge port 15, slag discharge pipe

Detailed ways

As shown in Figure 1, this process uses air and water vapor as gasification agents, and the raw coal of 0-6mm is sent through the screw feeder (9) and the biomass of 0-10mm through the screw feeder (10) according to a certain ratio. into the biomass fluidized bed gasifier (1), the air enters the biomass fluidized bed gasifier (1) from the Roots blower (6) through the air chamber (11) through the air distribution plate (12), so that the furnace The biomass and coal in the fluidized bed undergo partial oxidation, pyrolysis and gasification.

Since the reaction has an exothermic reaction and an endothermic reaction, when the two reactions are in thermal equilibrium, the bed temperature is in a stable state. The temperature is adjusted according to the ratio parameters of air volume, water vapor volume and biomass/coal volume to reach a predetermined temperature. Generally, the adjustment range of these parameters is 1.2-2.0m ³ /Kg of air/feeding ratio, 0.2-0.3Kg/Kg of water vapor and 0.3Kg/Kg of feed, and 40/60-80/20 of biomass/coal. Between; keep the bed temperature at 850-950°C to get better gasification effect. The high-temperature gas is discharged from the outlet of the biomass fluidized bed gasifier (1) through the high-temperature cyclone separator (2), and the carbon-containing dust separated by the high-temperature cyclone separator (2) is discharged into the ash storage box (7) through the feeding pipe, and the gas after dust removal enters the steam The generator (3) cools down to below 300°C through heat exchange, enters the scrubber (4) and is sent to the gas cabinet (5) for further use after further washing, dedusting and cooling. Part of the water vapor generated by the steam generator (3) is mixed with the air from the Roots blower and enters the biomass fluidized bed gasifier (1) through the air chamber (1), and part of the water vapor is directly sprayed by the steam nozzle (13) into the biomass fluidized bed gasifier (1). A powdery biomass charcoal outlet (14) is arranged in the middle of the biomass fluidized bed gasifier (1), and the biomass charcoal in the furnace is discharged into the charcoal storage box (8) as required.

According to the technical solution of the present invention, the typical operating parameters and characteristics of the Φ300 biomass and coal co-gasification fluidized bed gasifier demonstration plant are as follows:

Biomass: corn cob, 0-10mm; corn cob calorific value Q _{net, ar} : 17245KJ/Kg

Coal: 0-6mm; coal calorific value Q _{net, ar} : 23120KJ/Kg, the operating data of two embodiments are as follows:

The above experimental methods are only used to illustrate the technical solution, not to limit.

Claims (2)

1. the gasifying process that gasifies altogether of biomass and coal is characterized in that based on air and to add a small amount of water vapor be vaporized chemical, and it is 1.2～2.0m that air capacity accounts for the feed in raw material ratio of total amount of coal and biomass ³The ratio that/Kg, steam vapour amount account for coal and the reinforced total amount of biomass is 0.2～0.3Kg/Kg, and gasified raw material is the fine coal of 0-10mm powder biomass and 0-6mm, and both ratios of biomass/coal are 40/60-80/20; Two kinds of raw materials add biomass fluidized bed gasification furnace respectively by the feeding device of two special uses, the working temperature of biomass fluidized bed gasification furnace is 850～950 ℃, fluidizing velocity is 0.8～1.2m/s, the thick combustion gas that generates is through high temperature cyclone separator dedusting just, and the carbon containing dust under separating is gone into ash storage box through tremie pipe; First dust separating combustion gas is after the steam generator heat exchange, and temperature is reduced to below 300 ℃, enter the further scrubbing dust collection of purification system after, it is stand-by to be sent to gas holder; Air is infeeded in the stove by roots blower, the steam sub-fraction air feed usefulness that vapour generator produces, and it besides supplies.

2. implement the device of the fluidized-bed gasification furnace technology that biomass according to claim 1 and coal gasify altogether, it comprises: biomass fluidized bed gasification furnace (1), cyclonic separator (2), ash storage box (7) and storage charcoal case (8), vapour generator (3), washing tower (4); Wherein biomass fluidized bed gasification furnace (1) is made up of three parts, and top is great circle tubular vertical section, and the middle part is obconic expanding section, and the bottom is a roundlet tubular vertical section; Body of heater is the circular steel plate structure of refractory liner, and the body of heater bottom is sequentially with air compartment (11), scum pipe (15) and air distribution plate (12); Biomass fluidized bed gasification furnace is provided with two feed bins, the biomass silo (10) of the coal bunker (9) of band self-conveyor feed and band self-conveyor feed; At biomass fluidized bed gasification furnace lower vertical section middle part, coal bunker (9) links to each other with biomass fluidized bed gasification furnace (1) through self-conveyor feed; Be provided with biomass silo (10) links to each other with biomass fluidized bed gasification furnace (1) through self-conveyor feed in the expanding section middle and lower part; Be provided with four nozzles (13) on the top of biological material import and infeed water vapour, it is characterized in that the top of nozzle is provided with the drain hole of a biomass charcoal (14), biomass charcoal is entered in the storage charcoal case (8) by tremie pipe; The upper of furnace body outlet is connected with high temperature cyclone separator (2), and cyclonic separator (2) lower end links to each other with ash storage box (7) through tremie pipe; The top outlet of cyclonic separator (2) links to each other with vapour generator import (3), and its outlet links to each other with washing tower (4); It is stand-by that combustion gas behind the washing, purifying enters gas holder (5).

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