JPH066709B2 - Coal gasifier - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coal gasifier, and is particularly suitable for enhancing gasification efficiency in a spouted bed coal gasification furnace and at the same time suppressing burnout of a furnace wall. It relates to a coal gasifier.

[Conventional technology]

Conventionally, various systems such as fixed bed, fluidized bed, and spouted bed have been proposed for coal gasification furnaces. In these systems, the spouted bed keeps the temperature inside the furnace above the melting point of coal ash (approximately 1300 to 16
Compared to other methods, it has high gasification efficiency and a wide range of applicable coal types. ing.

As a spouted bed type coal gasification furnace, there is a gasification furnace in which a gasification chamber 31 is provided with a two-stage burner including an upper burner 20 and a lower burner 21, as shown in FIG. In this gasification furnace, the oxidizing agent is distributed more to the lower burner 21 than to the upper burner 20, and in the lower part of the gasification chamber 31, the ash content in the coal is melted to form a high temperature region where slag can be formed. High gasification performance is obtained by increasing the gasification reaction rate of the char activated by the pulverized coal 1 and the oxidant 3 supplied from the upper burner 20 in the high temperature range.

Generally, the gasification furnace is a pressurizing device in order to make the device compact, and the pulverized coal 1 is the atmospheric pressure hoppers 10 and 2.
Feeders 13, 14 through the base pressure hoppers 11, 12
Is supplied to the upper burner 20 and the lower burner 21 by a carrier gas 2 such as nitrogen gas. Oxidants 3 such as oxygen and air are sent to the upper burner 20 and the lower burner 21, respectively, and are gasified in the gasification chamber 31, and the produced gas is discharged from the produced gas line 6.
By making the supply amount of the oxidant 3 to the lower burner 21 larger than that of the upper burner 20, the temperature of the lower part of the gasification chamber 31 is raised to the temperature at which the slag is melted. Further, the slag tap 32 is heated by the tap burner 22 as needed, but the slag falls into the cooling water 36 and is water granulated,
It is discharged to the outside of the system through the slag discharge line 7.

[Problems to be solved by the invention]

FIG. 5 shows an example of an experimental result when oxygen is used as an oxidant in the coal gasifier shown in FIG. In this experiment, two types of coal, A coal and B coal, having different ash melting points and coal compositions were used as pulverized coal, the oxygen ratio of the lower burner 21 was 1.2 kg / kg, and the upper burner was constant. The gasification efficiency η represented by the following formula was measured by changing the oxygen / coal weight ratio of 20.

From FIG. 5, coal A and coal B have different oxygen supply amounts in the upper burner 20 when the gasification efficiency is maximum. Therefore, for example, during mixed coal operation such as switching from A coal to B coal, unless the amount of oxygen supplied to the upper burner 20 is appropriate, the gasification efficiency is lowered and the gas produced from the gasification furnace is used. Affect the equipment of.

In addition, for example, even when operating with one type of coal A, the composition of coal A may change depending on the coal seam and the mining location in the coal seam. Therefore, always operate with the oxygen supply amount corresponding to that composition. If not, the gasification efficiency may be reduced. Furthermore, when the coal supply rate changes greatly like load change, even if the oxygen supply rate is set in advance according to the analysis result of the coal, a difference occurs between the set value and the optimum value for obtaining the highest gasification efficiency, In particular, there is a problem that when the load is changed at the time of fuel switching, the difference is large and optimum operation cannot be maintained.

Further, in the gasification of coal having a high ash melting temperature such that the slag does not flow down at the supply amount of the oxidizer that maximizes the gasification efficiency, if the oxidizer is supplied more than necessary, the efficiency will decrease. By supplying more oxidant than necessary, not only the slag tap 32 but also the furnace wall is burned,
There is a problem that repair work of the gasification furnace is increased and the life of the gasification furnace is shortened.

The object of the present invention is to solve the above-mentioned problems of the prior art,
An object of the present invention is to provide a coal gasification device that can always obtain the highest gasification efficiency even when the composition of coal and the amount of coal supplied change, and prevent burnout of the furnace wall.

[Means for solving problems]

The above-mentioned object is to detect the calorific value of the generated gas from the gasification furnace per unit time, control at least the oxidant supply amount on the burner side of the uppermost stage so that the calorific value is maximized, and at the same time, the slagging section. Detects the fluid state of the slag at
Based on the information, it is achieved by controlling at least the oxidant supply amount on the burner side of the lowermost stage to the minimum amount required to maintain the slag flow down.

[Action]

The calorific value of the generated gas from the gasification furnace per unit time is
It can be calculated by measuring the composition of the product gas on the product gas line and taking the material balance of an inert gas such as nitrogen gas entering the furnace, or by measuring the composition of the product gas and its flow rate.

In this way, the calorific value of the produced gas per unit time is calculated, and by controlling the oxidant supply rate that contributes to at least partial oxidation in the burner on the uppermost stage side so that the calorific value becomes maximum, The maximum gasification efficiency can be maintained even when the composition and the supply amount are changed.

Further, at least on the lowermost burner side, if the oxidizer is controlled so as to have the minimum amount of oxidant required to maintain the slag flowing state in the slag forming section, the upper burner while maintaining the slag flowing down. It is possible to prevent excessive temperature rise in the vicinity of the lower burner, which is in a higher temperature range than in the vicinity, and prevent burning of the furnace wall. Even if the amount of oxidant for the lower burner fluctuates, the final gasification efficiency is adjusted by controlling the amount of oxidant for the upper burner.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a coal gasifier of the present invention. This coal gasifier includes a generated gas analyzer 70 that analyzes the composition of the generated gas in the middle of the generated gas line 6 from the gasification furnace main body 30, and this generated gas analyzer 7.
0 and a signal line 73 are connected to each other, and a calculator / controller 71 for calculating the calorific value of generated gas per unit time is installed.

The calculator / controller 71 is connected via a signal line 74 to a control valve 72A arranged in the oxidant line 64 for supplying the oxidant 3 to the upper burner 20. A camera 75 such as a television camera or an infrared camera is installed on the lower side surface of the gasification furnace main body 30. The camera 75 is connected to an image processor 76 via a signal line 77, and the image processor 76 is connected to the signal line. It is connected to the calculator / controller 71 by 78. The calculator / controller 71 uses the oxidizer 3 for the lower burner 2
Control valve 72 disposed in the oxidant line 65 for supplying the liquid
Connected to B.

1 is substantially the same as the conventional coal gasifier shown in FIG. 4 except for the above-mentioned components, and is therefore denoted by the same reference numerals, and the structural description will be omitted.

Next, the operation and effect of the coal gasifier having the above-described structure will be described.

The pulverized coal 1 is stored in the pulverized coal hopper 10 at normal pressure, the pressurized pulverized coal hopper 11 through the valve 40, and the pressurized pulverized coal hopper 12 through the valve 41. The pulverized coal stored in the pulverized coal hopper 12 is divided into predetermined amounts by the feeders 13 and 14 and reaches the ejectors 16 and 17. The ejector 16 is supplied with the N ₂ gas 2 as a carrier gas which is supplied through the valve 43 through the valve 43, and the pulverized coal 1 is pressure-equalized by the pressure equalizing pipe 17 so that the line 6 is discharged.
It is pneumatically transported through the inside of 3 and reaches the lower burner 21. Further, the ejector 16 is supplied through the valve 42 in the line 60, and the pulverized coal 1 is pressure-equalized by the pressure equalizing pipe 18 and the N ₂ gas 2 as a carrier gas is air-flow-transported in the line 62. It is supplied to the upper burner 20. Further, the oxidizer 3 is supplied to the upper burner 20 from the line 64, and the oxidizer 3 is supplied to the lower burner 21 from the line 64.

In the gasification chamber 31, a high temperature region is formed near the lower burner 21, which distributes a larger amount of oxidant than the upper burner 20, to slag the ash in the coal and to gasify the char formed on the upper burner 20 side. Let The generated gas generated in the gasification chamber 31 reaches the generated gas line 6 from the top of the gasification furnace main body 30 via the gasification chamber outlet 33.

The composition of the produced gas is detected by the produced gas analyzer 70. Based on the information on the composition of the generated gas by the generated gas analyzer 70, the calculation / control unit 71 calculates the calorific value of the generated gas per unit time from the calorific value per generated gas volume and the generated gas flow rate. Here, as a method of calculating the generated gas flow rate from the coal composition, nitrogen (N ₂ ) or air, which is an inert gas, is generally used as the pulverized coal carrier gas in the method of dry-feeding pulverized coal as in this embodiment. A method of calculating the material balance with the amount of nitrogen used for coal transportation is adopted. The flow rate of the generated gas may be directly measured with an orifice or the like.

When the calorific value per generated gas volume is calculated by the calculation / control device 71, the amount of the oxidant (O ₂ ) to the upper burner 20 is slightly changed as shown in FIG. When the amount becomes higher, the opening degree of the control valve 72A is controlled so that the minute change in the amount of the oxidant is continued until the amount of heat generation of the generated gas per unit time decreases.

Next, the reverse operation to the above is continued until the calorific value per unit time of the generated gas becomes high, and the generated gas with a high calorific value per unit time is always maintained even when the coal composition and the coal supply amount are changed. That is, it can be operated with the highest gasification efficiency.

Next, the slag 35 generated near the lower burner 21 of the gasification chamber 31 is granulated in the cooling water 36 through the slag tap 32, and is retained in the slag hopper 34 through the valve 48.
It is discharged from the slag discharge line 7 to the outside of the system via the valve 49. At this time, combustion gas is generated in the tap burner 22 by the fuel 4 supplied via the valve 46 and the oxidant 5 supplied via the valve 47, and this combustion gas is ejected near the slag tap 32.

The flow-down state of the slag 35 from the slag tap 32 is captured by the camera 75 as an image. In the image processor 76, the image from the camera 75 is subtracted from the image when the slag is not flowing down, for example, by a method of calculating the difference in contrast or the temperature difference between the drop of the slag and the surrounding temperature. It is determined whether or not it is flowing properly. As a means to detect the flowing state of slag,
There is a visible normal camera or an infrared camera, but the present invention is not limited to this, and any camera that can detect the flowing state of the slag can be used.

FIG. 3 is a flowchart showing an example of control on the lower burner 21 side.

When the image processor 76 determines that the slag 35 is appropriately flowing down, the calculation / control device 71 outputs a command to slightly reduce the opening degree of the control valve 72B, and this is introduced into the lower burner 21. The amount of the oxidizer 3 is slightly reduced.
On the other hand, when the image processor 76 determines that the slag 35 does not properly flow down, the calculation / control unit 71 outputs a command to slightly increase the opening degree of the control valve 72B, and thereby the lower burner 21 is introduced. The amount of the oxidizing agent 3 to be used is slightly increased. In this way, the amount of the oxidizer 3 supplied to the lower burner 21 is controlled to the minimum amount required to maintain the slag 35 flowing down, and an excessive temperature rise on the lower burner 21 side is suppressed.

In this case, when supplying the minimum amount of the oxidizer 3 required for the slag 35 to flow down, it is desirable that the temperature near the slag tap 32 is within 100 ° C. at least higher than the pour point of the coal ash.

Further, the supply amount of the oxidizer 3 in the upper burner 20 is controlled in accordance with the control of the supply amount of the oxidizer 3 on the side of the lower burner 21 described above, and the highest gasification efficiency can be finally maintained.

If the rough relationship between the coal supply amount and the oxygen supply amount is incorporated in advance, the time required to reach the optimum control state can be shortened.

As described above, the gasification efficiency can always be maximized even if the composition of coal and the amount of coal supplied change. Therefore,
Normally, even when using the same brand of coal, the composition is not constant due to the difference in the coal seam, the mining site in the coal seam, etc. Also, when different brands of coal are mixed and used, they cannot be mixed in advance and used. Therefore, the composition of coal changes every moment as compared with the case of using one kind of coal. In the present embodiment, the calorific value of the produced gas per unit time can be kept at the highest level even with such changes in the coal composition over time.

Also, when switching from one brand of coal to another brand of coal, there is a process such as crushing and hopper filling from the mixing of coal to the gasification furnace. It is difficult to grasp the time. Also in this case, in the present embodiment, the calorific value of the generated gas per unit time can be always maintained at the maximum state in response to the change of the calorific value of the generated gas due to the coal composition supplied to the gasification furnace. .

Further, even when coals having different melting points are mixed and used, high gasification efficiency can be always maintained while keeping the slag flowing down.

In the above-described embodiment, an example in which two sets of burners, the upper burner 20 and the lower burner 21, are provided in the gasification chamber 31 and the amount of the oxidant 3 introduced into each burner is controlled, is shown. Is not limited to the case of controlling the amount of the oxidant introduced into the burner itself, and a system for controlling the amount of the oxidant contributing to the partial oxidation of the pulverized coal supplied from each burner can be adopted. As an example of this system, for example, oxidant supply nozzles are provided near the outlet openings of the upper burner 20 and the lower burner 21, respectively, and the amount of oxidant supplied from each oxidant supply nozzle into the gasification chamber 31. There is a method of controlling the above by the method described above.

Further, in the present invention, the burner is not limited to the case of two stages
An example in which a burner having more than one stage is installed is also included. in this case,
It is sufficient to control the amount of the oxidizer so that the calorific value of the produced gas per unit time is maximized in at least the uppermost burner, and at least in the lowermost burner, the maximum amount required to maintain the slag flow is maintained. The amount of the oxidizing agent may be controlled to be small.

〔The invention's effect〕

As described above, according to the present invention, the supply amount of the oxidizer to the upper burner side is controlled so that the calorific value of the produced gas per unit time is maximized even with respect to changes in the coal composition and the coal supply amount. Therefore, the gasification efficiency can be always maintained at the maximum. Furthermore, the flow rate of slag can be detected and the amount of oxidant supplied to the lower burner side can be maintained at the minimum amount necessary to maintain the flow state of slag. Burnout can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a coal gasifier of the present invention, and FIG. 2 is a flow chart showing an example of controlling an oxidant supply amount to an upper burner in the coal gasifier shown in FIG. FIG. 3 is a flow chart showing an example of controlling the amount of oxidant supply to the lower burner in the coal gasifier shown in FIG. 1, FIG. 4 is a schematic configuration diagram showing a conventional coal gasifier, and FIG. 5 is coal. 6 is a graph showing the relationship between the upper burner oxygen / coal weight ratio and the gasification efficiency when A and B coals having different compositions are used. 1 ... Pulverized coal, 2 ... Pulverized coal carrier gas, 3 ... Oxidizing agent,
4 ... Fuel, 5 ... Oxidizer, 6 ... Product gas line, 7
...... Slag discharge line, 20 ...... Upper burner, 21 ......
Lower burner, 22 ... Tap burner, 30 ... Gasification furnace main body, 31 ... Gasification chamber, 32 ... Slag tap, 70
...... Generated gas analyzer, 71 …… Calculator / controller, 72A,
72B ... control valve, 75 ... camera, 76 ... image processor.

Claims (1)

[Claims] 1. A coal gasifier comprising a spouted bed coal gasification furnace which gasifies at a temperature above the melting point of coal ash, wherein fine powder is divided into a plurality of stages in the height direction of the spouted bed coal gasification furnace. Means for supplying charcoal, means for supplying an oxidant for partially oxidizing the differential coal, means for detecting the calorific value per unit time of the produced gas discharged from the spouted bed coal gasification furnace, A means for controlling the flow rate of the oxidizer that contributes to partial oxidation in at least the uppermost burner so that the calorific value per unit time of the produced gas becomes maximum, and the slag flowing out from the lower part of the spouted bed coal gasification furnace. Means for detecting the flow-down state, and means for controlling the amount of the oxidant contributing to partial oxidation in at least the lowermost burner on the basis of the information from the detection means to the minimum amount required to maintain the flow of the slag. Establishment Coal gasifier, characterized in that.