CN1098910C - Thermal-cracking decoking biomass gasification furnace - Google Patents

Abstract

The invention relates to the processing and utilization of agricultural waste and the manufacture of equipment for producing gas from solid carbonaceous materials. It includes a furnace body, a fire grate, a feed port, an air distribution port, a slag discharge port, a gas outlet, etc. of an existing fixed-bed downdraft gasifier. It is also possible to add a cracking catalytic bed on the bottom of the furnace. The invention forces the gas flow to slow down in the flow channel, prolongs the residence time of the gas in the high-temperature environment, and cracks part of the tar in the gas. In the case of setting the catalytic bed, the cracking reaction is more sufficient, further improving the tar cracking rate, gasification efficiency and gas calorific value.

Description

Thermal cracking decoking biomass gasifier

The invention relates to the treatment and utilization technology of the waste of crops, and also relates to the manufacture of equipment for producing gas from solid carbonaceous materials.

Biomass gasification is to use a gasification device to burn biomass in an oxygen-deficient state, so that most of the combustible substances are converted into combustible gases, which are cooled and purified for power generation or cooking. According to different combustion methods, there are many types of gasification devices. The most common one in the prior art is the fixed bed downdraft gasifier, which has the characteristics of simple structure, low cost, and easy operation. It is very suitable for my country's national conditions, especially for In rural areas of our country, it is used to deal with crop waste, such as straw, rice husk, branches, weeds, etc. However, due to the structural constraints of the gasifier itself, its gasification efficiency and gas calorific value are both low, and the tar content in the gas is high. This gas is not conducive to storage and transportation, thereby affecting the further utilization of this technology.

The purpose of the present invention is to improve the structure of the existing fixed-bed downdraft gasifier, to provide a biomass gas that can improve the gasification efficiency and the calorific value of the gas, and can crack the tar in the output gas Furnace.

The purpose of the present invention is achieved in the following ways.

The thermal cracking and decoking biomass gasification furnace of the present invention includes the furnace body and fire grate of the fixed bed downdraft gasification furnace in the prior art, and the feeding port, air distribution port and slag discharge port arranged on the furnace wall . The gas outlet is characterized in that a detour of gas flow is provided under the fire grate. The roundabout flow channel can be constructed as follows: an inverted cone tubular baffle is connected under the grate, its bottom is connected to the furnace wall, a section of straight pipe is connected to its lower port, and a large round pipe is arranged on the furnace floor. The mouth is lower than the upper port of the straight pipe, and the cross-sectional areas of the inside of the straight pipe, between the outer wall of the straight pipe and the large circular pipe, and between the outer wall of the large circular pipe and the furnace wall are equal or similar. A slag discharge pipe is installed on the wall of the large circular pipe and extends To the outside of the furnace wall, the gas outlet is arranged at the lower part of the furnace body. It is also possible to set a cracking catalytic reaction bed on the bottom of the furnace, which is composed of a block or granular catalyst and a cover plate thereof. There are through holes used as gas flow passages on the top, and the gas outlet is set on the furnace wall of the catalytic reaction bed section. The catalyst is a commonly used thermal cracking catalyst, such as granular dolomite, iron oxide, activated carbon, etc.

The thermal cracking and decoking biomass gasification furnace of the present invention, on the one hand, retains the characteristics of the fixed bed downdraft gasification furnace in the prior art, such as simple structure and low cost; The gas flow slows down in the flow channel, delaying the residence time of the gas flow in the furnace, causing the generated gas to undergo thermal cracking reaction in a high-temperature environment, and part of the tar in the gas is cracked. In the case of setting a catalytic reaction bed, due to the action of the catalyst, the cracking reaction is more sufficient, further improving the tar cracking rate, gasification efficiency and gas calorific value.

Further description will be made below in conjunction with the embodiments and accompanying drawings.

Fig. 1 is a schematic diagram of the overall structure of a fixed-bed downdraft gasifier in the prior art.

Fig. 2 is a schematic diagram of the overall structure of an embodiment of the thermal cracking and decoking biomass gasifier according to the present invention.

Fig. 3 is a schematic diagram of the overall structure of another embodiment of the thermal cracking and decoking biomass gasifier according to the present invention.

See Figure 1, (1) is the furnace body, (2) is the fire grate, which divides the furnace into upper and lower parts, (3) is the air distribution port, (4) is the feed port, and (5) is one-time slag discharge Port, (6) is the secondary slag discharge port. (7) is gas outlet. It can be seen from the figure that the gas generated by the incomplete combustion of crop waste in the upper furnace is directly sucked out by the exhaust fan installed at the gas outlet. The flow path stroke is short, and the gas stays in the furnace for a short time, so there is no time for cracking The reaction, therefore, has a higher tar content.

Referring to Fig. 2, in this embodiment, a roundabout flow channel for gas flow is provided under the fire grate, and an inverted conical tube (8) is arranged under the fire grate, and the bottom angle of the cone is about 45°, and the upper bottom of the tube is connected to the furnace wall , the lower port is connected with a section of straight pipe (9), and (10) is a large round pipe located on the bottom of the furnace, and the upper end of the tube is lower than the upper end of the straight pipe. The heights of the inverted tapered pipe (8) and the straight pipe (9) respectively account for 1/3 of the height of the lower furnace, and the cross-sectional areas of the inside of the straight pipe, the distance from the inner wall of the large circular pipe to the outer wall of the straight pipe, and the distance between the outer wall of the large circular pipe and the inner wall of the furnace are approximately equal to ensure smooth flow of gas. The gas outlet is set under the furnace wall, which can increase the gas stroke. The arrows in the figure indicate the flow direction of gas in the furnace. It can be seen from this that the gas is forced to slowly travel along the circuitous flow in the lower furnace until it is drawn out by the exhaust fan from the outlet (7) and sent to the cooling and purification device. Compared with the prior art, the device of this embodiment prolongs the residence time of the gas in the high-temperature environment, ensures the cracking reaction, reduces the content of heavy molecular tar, and improves the gasification efficiency.

Experiments show that the tar in the produced gas can be cracked by 60% by using the gasifier with this structure to treat crop waste. Compared with the fixed-bed downdraft gasifier in the prior art, the gasification efficiency is increased by 12%, and the calorific value of the gas is increased by 15%.

Referring to Fig. 3, present embodiment is to set up the catalytic reaction bed that is full of catalyst on the hearth, (11) is granular catalyst, and particle diameter is about 1-3cm, as granular dolomite. (12) is a cover plate, and the large circular tube is fixed on the cover plate, so that the catalytic reaction bed is separated from the large circular tube inner cavity. Through holes are evenly distributed on the cover plate between the large round tube and the furnace wall, which are used as gas flow channels. The height between the bottom of the furnace and the cover plate accounts for about 2/5 of the height of the lower furnace. The height of the inverted tapered pipe (8) and the straight pipe (9) accounts for 1/3 of the remaining height of the lower furnace respectively, and the radial dimensions of the straight pipe and the large circular pipe are the same as those of the previous embodiment to ensure the smooth flow of gas. A gas outlet pipe (13) is connected from the gas outlet, and it stretches into the middle part of the particle catalyst, and the gas that has fully reacted with the catalyst is sucked out of the furnace body.

In this embodiment, not only a reasonable air flow channel is added, but also the gas that has been flowing in a circuitous manner in the lower furnace is sucked into the catalytic reaction bed from the space on the outer wall of the large circular tube. Under the action of the catalyst, the tar in the gas is fully produced. After the cracking reaction, it is pumped out, so the tar content in the output gas is low and the calorific value is high. Experiments show that when the gasification furnace with this structure is used to treat crop wastes, 60% of the tar in the produced gas can be cracked. Compared with the fixed-bed downdraft gasifier in the prior art, the gasification efficiency can be increased by 15%, and the calorific value of the gas can be increased by 20%.

Claims (2)

1. thermal-cracking decoking biomass gasification furnace, the body of heater that comprises fixed bed downdraft vapourizing furnace of the prior art, fire grate, and be arranged on feeding port on the furnace wall, air distribution outlet, slag-drip opening, gas outlet, it is characterized in that, below fire grate, be provided with the circuitous runner of a fuel gas flow, the circuitous runner of this fuel gas flow constitutes like this: be connected with a tubular baffle plate of back taper below fire grate, its end, be connected with the furnace wall, its lower port is connected with straight-run of pipe, on drop-bottom, also be provided with a big pipe, this mouth of pipe is lower than the straight tube upper end, in the straight tube, between straight tube outer wall and big pipe, big circular tube external wall equates with twere three's sectional area or is close, tipping has scum pipe and extends to outside the furnace wall on the great circle tube wall, and gas outlet is arranged on the body of heater bottom.

2. thermal-cracking decoking biomass gasification furnace as claimed in claim 1, it is characterized in that, the cracking and catalyzing reaction bed also is set on furnace bottom, it is made of pellet type catalyst and cover plate thereof, described cover plate upper surface is connected with the great circle infratubal port, be provided with the through hole as the combustion gas runner on the cover plate of big pipe and twere, gas outlet is arranged on the furnace wall of catalytic bed section, and described catalyzer is the thermal cracking catalyst of using always.

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