JPS6023485A - Coal gasification apparatus - Google Patents

Abstract

PURPOSE:To prevent the troubles caused by the temperature lowering near the oxygen burner in a jet-layer gasification furnace, by attaching a flow control valve to the oxygen-supply line of the coal supply burner, and controlling the supply of oxygen to the burner according to the state of the slag deposited in the gasification furnace. CONSTITUTION:The wall of the gasification furnace 10 is furnished with a pair of vertically arranged burners 3A and 3B and flow-control valves 13 and 14. The valves 13 and 14 are provided with a timer 16 and a device 15 for setting and switching the ratio of oxygen/coal to enable the alternate change-over of the valves 13 and 14. The supply of the oxygen from the valves is controlled by this process so as to attain a specific oxygen/coal ratio for a definite time interval at the burners 3A and 3B. The oxygen content in the coal-transfer gas of the burner 3B is adjusted separately, or the oxygen supply is controlled by adjusting the timer so as to maintain the pulverized coal at a temperature above the temperature to cause the solidification and deposition of the coal in the burners 3A and 3B. The troubles caused by the solidification and deposition of slag flowing down along the wall of the furnace can be prevented by this process.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coal gasifier, and more particularly to a coal gasifier that prevents troubles caused by a temperature drop in the vicinity of an oxygen burner in a spouted bed gas furnace.

A prior art spouted bed gasifier is shown in FIG. In the figure, pulverized coal is blown together with oxygen (or air) through a burner 3 into a gas furnace 10 formed in a pressure vessel 4. In the furnace, a gas consisting mainly of CO and 1-12 is generated due to a partial oxidation reaction. Normally, 80 to 98% of the carbon in the input coal reacts in the gas furnace IO, and the remaining unburned carbon is entrained in the produced gas and sent from the gasifier to cyclone 6, heat recovery boiler 7, and cyclone 6.
The gas is then sent to the gas purification section 9. On the other hand, 30 to 70% of the ash in the coal adheres to the refractory jfAl on the furnace wall, flows down in a molten state, falls from the slag tap hole 8, is rapidly cooled in the quench tank 75 at the bottom of the furnace, and is discharged as solidified slag 5A. be done. After the remaining ash is discharged from the furnace along with the gas, it is collected by the cyclone 6 and recycled to the gasifier 10 by the air flow of N2 gas.

The reaction conditions include a gasification concentration of 1400 to 2300"C.
Almost all furnaces are operated in the range of 1 pressure normal pressure to 1100 at and a supply oxygen/supply coal weight flow ratio of about 0.7 to 1.0.

The two main efficiency factors of the gas furnace 10 are cold gas efficiency and coal reaction rate, which are defined as in the following equation.

Coal amount x Coal calorific value To improve these two efficiencies, it is necessary to reduce the amount of oxygen as much as possible, increase the coal reaction rate in the gasifier, and reduce the carbon percentage in the gas-entrained fine powder. . The relationship in which cold gas efficiency increases as the amount of oxygen decreases will be explained with reference to FIG. 2. FIG. 2 shows the material end-to-end of the gasifier, and as 02 is reduced, the amount of CO+H20 decreases and the ratio of CO+H2 increases. In other words, cold gas efficiency increases. However, 02
Since the coal reaction rate decreases when the amount of 02 is reduced, the cold gas efficiency begins to decrease when the amount of 02 becomes less than a certain amount. In addition, as the amount of 02 is reduced, the temperature inside the gasifier decreases, causing solidification of the ash slag flowing out from the slag tap.
In order to prevent this, it is necessary to supply more than a certain amount of 02. Considering this relationship, as a method to increase the reaction rate of coal, the coal supply burner is set in two stages, the 02 quantity coal ratio of the upper stage burner is 0.4, the 02 quantity coal ratio of the lower stage burner is 1.2, and the 02 quantity coal ratio of the lower stage burner is set to 1.2. A method has been considered in which the temperature near the slag tap is kept high and the residence time of particles is increased. However, the upper gasification temperature did not rise, and the slag did not flow down but stuck to the wall, making it impossible to continue operation.

An object of the present invention is to provide a coal gasification device that has both a high coal reaction rate and a high cold gas efficiency, and which does not cause ash fixation problems.

The present invention provides a coal gasifier in which a plurality of coal supply burners are arranged in a gasification furnace in multiple stages so as to generate a swirling flow in the furnace. The gas furnace is characterized in that the amount of oxygen supplied to the upper burner is increased or decreased depending on the state of slag adhesion within the gas furnace.

In the present invention, in order to increase or decrease the amount of oxygen supplied to the upper burner according to the slag deposition status in the gasifier, the temperature of the refractory wall of the coal gasifier is measured, and the temperature is higher than the solidification temperature of the slag. It is preferable to control the amount of oxygen supplied to the upper burner so that Further, it is preferable to provide a buffer tank to absorb fluctuations in gas amount and coal gas due to increase/decrease in oxygen supply.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 3 is an explanatory diagram of a coal gasification apparatus showing one embodiment of the present invention. In the figure, the differences from the device in Figure 1 are as follows:
Two stages of upper and lower burners 3A and 3B are installed on the fireproof wall of the furnace, and flow control valves 13.1 are installed in the oxygen supply lines provided with the coal IM feed lines of the burners 3A and 3B, respectively.
4 is provided, and the flow rate control valve is provided with an oxygen/coal ratio setting switching device 15 and a timer 16, so that the amount of oxygen supplied from the valves 13 and 14 is adjusted to the upper and lower burners 3A,
3B can be alternately switched to a predetermined oxygen/coal ratio for a predetermined period of time. Note that the cyclone 6 on the downstream side is connected to a buffer tank 11, and this buffer tank 11 is connected to the control valve 13 or 1.
In order to absorb changes in the amount of gas in the gas furnace at the time of switching, the cyclone-collected ash is connected to a recycling line for returning the cyclone-collected ash to the coal-gas furnace lO.

In the above configuration, pulverized coal is supplied to the upper and lower burners 3A and 3B of the two-stage swirling flow furnace at a ratio of 1:E. At this time, oxygen is supplied at a weight ratio of 0.8 to the total amount of coal supplied. ” If 0.4 is supplied to the second stage burner 3B and 1.2 is supplied to the lower stage burner 3A, the amount of oxygen supplied to the total amount of coal supplied becomes 0.8.

If Pacific coal is used, under these reaction conditions, for example, a carbon reaction rate of 93% and a cold gas efficiency of 70% can be obtained, but under these conditions, the amount of oxygen in the upper stage is as low as 0.4, so the gasification temperature increases. For example, when the gas temperature near the lower burner is 2200 to 2300°C, the gas temperature near the upper burner is 1500°C or less, and under such conditions Below,
For example, in the case of Pacific coal, the gas temperature is below the pour point of ash in a reducing atmosphere, approximately 1400°C, which makes it difficult for the ash to flow on the furnace wall, and the flow of adhesion onto the furnace wall becomes extremely large. This causes problems such as burner blockage and slag tap hole blockage due to solidified slag falling off. In particular, as the distance between the upper and lower burners increases with scale-up, the temperature distribution inside the furnace becomes uneven, and the upper burner becomes less susceptible to the effects of the lower burner, causing the temperature near the upper burner to drop further. Admitted.

In order to deal with this, the present invention periodically switches the oxygen/coal ratio of the upper stage burner with that of the lower stage burner, which supplies a large amount of oxygen.
By periodically increasing the amount of coal burned in the upper burner, the furnace wall temperature near the upper burner is periodically increased.
This is to prevent slag accumulation on the furnace wall. FIG. 4 shows an example of such an operating method. The area near the upper burner is gasified at approximately 1400°C during the period corresponding to period T2, and a highly efficient gasification reaction is performed. At the time corresponding to the period T+, the slag is gasified at 2,200 to 2,300° C., and the slag deposited in the period T1 is melted and flowed down. In this way, the adhesion and growth of solidified slag in the vicinity of the upper burner is suppressed.

In addition, it is desirable to provide a buffer pump 11 (FIG. 3) of sufficient capacity in the gas recycle system of the furnace so as to absorb fluctuations in gas composition due to changes in operating conditions.

Due to the operation of the present invention, the amount of molten slag discharged also changes periodically, which rather has a positive effect on the slag discharge. This is because when the slag flows down from the slag tap ball, if the flow rate is above a certain level, the rate of heat loss will be smaller and the risk of re-solidification near the slag tap will be reduced. It is from.

In addition, in the operating method shown in Fig. 4, if an abnormal drop in the temperature of the refractory material on the furnace wall (thermometer 12 in Fig. 3) is detected,
It is possible to operate so that the amount of oxygen supplied to the upper burner increases, that is, the cycle T2 becomes longer (the cycle T1 becomes shorter). In this way, the oxygen/coal ratio of the upper and lower burners is periodically switched so that the temperature of the refractory material near the upper burner is higher than the allowable temperature for gas slag deposition.
Alternatively, by changing the period, troubles caused by solidification and accumulation of slag can be prevented.

FIG. 5 shows a control system in which the coal/oxygen ratio of the upper stage burner is changed independently according to the temperature of the fireproof wall. This equipment system is installed on the furnace wall near the upper bar 3B (
a temperature detector 12 provided on a fireproof wall), a temperature instruction control unit 23 connected to the temperature detector 12, a flow rate setting device 24 that determines the oxygen supply amount according to instructions from the control unit, and the flow rate setting device 2.
The flow rate control valve 25 supplies a predetermined amount of oxygen to the upper stage burner in response to a signal from the flow rate control valve 25, and a flow rate indicator/controller 26 performs feedback control so that the flow rate of the flow rate control valve 25 becomes the predetermined value. In addition, 20 is a solidified slag, 21 is a flowing slag, 22 is an outer shell of the furnace, and 25A and 26A are each a lower stage burner 3A.
These are a flow rate control valve and a flow rate indicator adjustment needle provided at 5.

FIG. 6 also shows that the furnace wall temperature near the upper burner 3B is detected by the detection end 12 and the temperature indicator 27, and is connected to the flow rate setting device 24 and the timer setting device 10 so that the temperature becomes a predetermined value or higher. The flow rate control valve 25 controls the amount of oxygen supplied to the upper burner 3B.

As shown in FIGS. 5 and 6, the temperature of the furnace wall near the upper burner 3B is detected, and the upper burner 3B
By independently changing the amount of oxygen in the coal carrier gas of B,
Alternatively, by changing the oxygen supply amount periodically or periodically by setting a timer, it is possible to prevent troubles caused by solidification and accumulation of slag flowing down on the furnace wall.

As described above, according to the present invention, it is possible to provide a coal gasification apparatus that is free from troubles such as adhesion and accumulation of molten ash or slag while maintaining a high coal reaction rate and cold gas efficiency.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a conventional spouted bed coal gasifier;
The figure is a conceptual diagram for explaining the balance of gasified materials in a coal gasifier, and FIGS. 3 and 4 are explanatory diagrams showing a coal gasifier and its operating method according to an embodiment of the present invention. FIG. 5 and FIG. 6 respectively show the upper stage burner according to the present invention. FIG. 2 is an explanatory diagram showing a control device system for changing the coal/oxygen ratio. 3A...lower burner, 3B...upper burner, 6...
・Cyclone, 7... Heat recovery boiler, 1o... Gasifier, 11... Buffer tank, 13.14...
Oxygen flow rate control l-roll valve, 15...Oxygen/coal ratio setting switch, 16...Timer. Agent Patent Attorney Takenaga Kawakita Figure 1b Figure 2 -! Figure 3: Preservation! Figure 4 Figure 5 Figure B Figure 6 595-

Claims (1)

[Scope of Claims] (1) In a coal gasifier in which a plurality of coal supply burners are arranged in a gasification furnace in multiple stages so as to generate a swirling flow in the furnace, the oxygen in the upper stage coal supply nozzle is A coal gasifier characterized in that a flow rate control valve is provided in the supply line to increase or decrease the amount of oxygen supplied to the upper part/Nl-gas according to the state of slag adhesion within the gas furnace. (2. A coal gasification apparatus according to claim 1, characterized in that the temperature of the fireproof wall of the coal gas furnace is measured, and the amount of oxygen supplied to the upper burner is increased or decreased depending on the temperature. ( 3) The coal gas according to claim 1 or 2, characterized in that a fuel tank is provided to absorb fluctuations in the gas amount and coal gas composition due to increases and decreases in the amount of oxygen supplied. conversion device.