CN103952186B - There is the down-draft type gasifying furnace of tar degradation function - Google Patents

Abstract

The downdraft gasifier with tar degradation function disclosed by the present invention comprises a furnace, the lower part of the furnace has an annular constriction, there is a feed port at the top of the furnace, an ash outlet at the bottom, and a wall above the annular constriction of the furnace There are upper, middle and lower three-stage tangential primary air distribution ports along the axial direction, and a tubular grate is placed between the annular constriction at the lower part of the furnace and the ash outlet at the bottom. The tubular grate is composed of hollow steel pipes spaced apart from each other. The hollow steel pipe is drilled with a hole as a secondary air distribution port. There is a vertical flue outside the furnace. There is an air outlet on the upper part of the flue, and a calcium-based catalyst injection device is arranged on the top. The downdraft gasifier has a simple structure and has tar self-purification capability, which can ensure that the tar in the gasification gas has been fully decomposed before leaving the furnace, thereby obtaining higher-quality gasification gas.

Description

Downdraft gasifier with tar degradation function

technical field

The invention relates to a downdraft gasifier with the function of tar degradation, and belongs to the technical field of clean utilization of waste resources.

Background technique

At present, waste disposal is a major problem that needs to be solved urgently in today's society, and gasification technology is a clean and efficient method for waste disposal. Waste gasification is a method of pyrolysis and gasification of waste in a fixed gasifier and other devices in a high-temperature and low-oxygen environment to obtain combustible gases. Among many gasifiers, the fixed bed occupies an important position due to its simple structure, convenient operation, wide fuel adaptability and low investment. Traditional fixed bed gasifiers mainly include updraft fixed bed gasifiers and downdraft fixed bed gasifiers, but at present both gasifiers have serious problems, such as short residence time in the furnace , the tar content in the gasification gas is high, and it is easy to stick to the flue at the end of the furnace to form a blockage after the temperature drops, which is not conducive to the stable operation of the gasifier. Moreover, because the gasification gas contains tar, it increases the difficulty of the post-purification treatment of the gasification gas. Therefore, there is an urgent need to develop a gasifier with tar self-purification capability to ensure that the tar in the gasification gas has been fully decomposed before leaving the furnace, so as to obtain a higher quality gasification gas.

Contents of the invention

The object of the present invention is to propose a downdraft gasifier with tar degradation function in order to solve the excessively high tar content in the waste gasification process.

The downdraft gasifier with tar degradation function of the present invention comprises a furnace, the lower part of which has an annular constriction, a feed opening at the top of the furnace, an ash outlet at the bottom, and an edge on the wall above the annular constriction of the furnace. There are upper, middle and lower three-stage tangential primary air distribution ports in the axial direction, and a tubular grate is placed between the annular constriction at the lower part of the furnace and the ash outlet at the bottom. The tubular grate is composed of hollow steel pipes spaced apart from each other. The steel pipe is drilled with a hole as a secondary air distribution port. There is a vertical flue outside the furnace. One end of the horizontal flue that is flush with the tubular grate is connected to the furnace, and the other end is connected to the vertical flue. The upper part of the vertical flue has an air outlet, and the top is provided with a calcium-based catalyst injection device.

In the present invention, each of the three primary tangential air distribution ports of the upper, middle and lower stages has 3-5 tangential air distribution ports along the circumference of the furnace.

The present invention has the following characteristics: the material is fed into the furnace from the feed port on the top of the furnace, mixed with the primary gasification air during the descent process, and undergoes pyrolysis and gasification through the high temperature zone, and the upper, middle and lower stages arranged along the axial direction The air distribution enters the furnace in a tangential manner, forming a swirl area in the furnace, which helps to prolong the residence time of materials in the high temperature area; the arrangement of the secondary gasification air forms a local fluidization in the upper space of the grate The area not only helps ash fall, but also ensures the complete gasification of fixed carbon, keeps the bed at a high temperature above 750°C, and helps the degradation of tar components in the gasification gas. The arrangement of the vertical flue can prolong the residence time of the gasification gas, and the calcium-based catalyst injection can effectively realize the complete degradation of the tar components in the syngas.

The invention has a simple structure and has tar self-purification ability, which can ensure that the tar in the gasification gas is fully decomposed before leaving the furnace, thereby obtaining higher-quality gasification gas.

Description of drawings

Fig. 1 is a schematic structural diagram of a downdraft gasifier with tar degradation function according to the present invention.

Figure 2 is a top view of the tube grate.

Figure 3 is a schematic diagram of a tangential primary air distribution port at any stage.

Detailed ways

With reference to Fig. 1, the downdraft gasifier with tar degradation function of the present invention comprises a hearth 1, the bottom of the hearth has an annular constriction, a feed port 12 is arranged on the top of the hearth, an ash outlet 7 is arranged at the bottom, and an ash outlet 7 is arranged at the bottom of the hearth. The upper, middle and lower three-stage tangential primary air distribution ports 2, 3, and 4 are arranged axially on the furnace wall above the constriction, and each stage has four tangential air distribution ports along the furnace circumference (as shown in Figure 2 for an example) , the primary gasification air can be tangentially injected into the furnace from the upper, middle and lower parts of the furnace wall, forming a swirling flow area in the furnace, which is beneficial to the good mixing of gasification medium and materials, and prolongs the time for materials to stay in the high temperature zone. the residence time. A tubular grate 6 is placed between the annular constriction at the lower part of the furnace and the bottom ash outlet 7. The tubular grate 6 is composed of hollow steel pipes spaced apart from each other. The gap between the steel pipes is conducive to ash discharge. The hole 5 (as shown in Figure 3) is drilled on the upper side as the secondary air distribution port. Air is introduced into the steel pipe, and the gasification medium in the steel pipe is sprayed into the furnace at a relatively high flow rate through the hole to form a secondary gas. The higher wind speed can fluidize the materials in the local space above the tubular grate 6 to form a local fluidized zone. This design not only enables the ash to fall into the ash outlet 7 smoothly, but also facilitates the complete gasification of the fixed carbon at the bottom of the bed, which has great advantages in increasing the gasification temperature in this area and reducing the output of tar. There is a vertical flue 9 outside the furnace, and one end of the horizontal flue 8 flush with the tubular grate communicates with the furnace, and the other end communicates with the vertical flue 9. There is an air outlet 10 on the upper part of the vertical flue. A calcium-based catalyst injection device 11 is provided.

During normal operation, the material enters the furnace from the feeding port. During the descent, it mixes with the primary gasification air tangentially entering the furnace and forms a swirling disturbance in the furnace to ensure that the material is fully dried and heated in the high temperature area. Then the material falls on the tubular grate to form a stacked bed, and the secondary gasification wind can make the lower bed form a local fluidized area, which is convenient for the smooth discharge of ash and slag. In addition, the secondary gasification air can also promote the complete oxidation of fixed carbon at the bottom of the bed, thereby ensuring that the bed temperature is maintained above 750°C. When the gasification gas passes through the bed, the tar component in it can be further decomposed at high temperature, which reduces the tar amount of the gasification gas to a certain extent. The ash at the bottom of the bed falls into the ash outlet through the gap between the tubular grates, and then enters the ash hopper for collection. After the gasification gas passes through the bed, it enters the vertical flue through the horizontal flue. Due to the effect of gravity, the fly ash particles carried by the gas fall to the bottom of the vertical flue, which is beneficial to the purification of the gasification gas, while the gasification The gas leaves the furnace through the gas outlet on the upper part of the vertical flue. The injection of calcium-based catalyst can further promote the secondary cracking of tar to ensure that the tar is fully decomposed before leaving the furnace, thereby improving the quality of the outlet gasification gas.

Claims (2)

1. A downdraft gasifier with tar degradation function, which is characterized in that it includes a furnace (1), the lower part of the furnace has a ring-shaped constriction, there is a feeding port (12) at the top of the furnace, and an ash outlet (7) at the bottom , On the wall above the annular constriction of the furnace, there are upper, middle and lower three-stage tangential primary air distribution ports (2, 3, 4) in the axial direction, and the annular constriction at the lower part of the furnace and the bottom ash outlet (7) There is a tubular fire grate (6) between them. The tubular fire grate (6) is composed of hollow steel pipes spaced apart from each other. Hollow steel pipes are drilled with holes (5) as secondary air distribution ports on the upper side. Straight flue (9), one end of the horizontal flue (8) flush with the tubular grate communicates with the furnace, and the other end communicates with the vertical flue (9), and there is an air outlet on the upper part of the vertical flue ( 10), the top is provided with a calcium-based catalyst injection device (11). 2. The downdraft gasifier with tar degradation function according to claim 1, characterized in that each of the upper, middle and lower three-stage tangential primary air distribution ports (2, 3, 4) is along the There are 3-5 tangential air distribution ports in the furnace circumference.