JPS63254192A - Operation of coal gasifying furnace of jet flow layer - Google Patents

Abstract

PURPOSE:To improve gasification efficiency while maintaining flow stability of slag, by forming a jet flow layer from coal and air adjusted to a specific amount and feeding air rich in oxygen to a lower layer of reaction to maintain temperature at >=given value. CONSTITUTION:In gasifying coal by forming a jet flow layer from coal and a gasifying agent comprising air, the amount of air is controlled based on total oxygen ratio fixed corresponding to load. On the other hand, air rich in oxygen is fed to the lower part of reaction layer and the amount of the air rich in oxygen is controlled to main temperature at the lower part of the reaction layer at >=a given value. The produced slag is made to flow to the bottom part of a furnace and discharged to operate a coal gasifying furnace of jet flow layer type.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of operating a spouted bed type coal gasifier, and particularly to a method suitable for improving gasification efficiency while maintaining slag flow stability. This invention relates to a method of operating a spouted bed coal gasifier.

[Conventional technology]

Figure 2 shows a cross-sectional view of a typical spouted bed type coal gasifier. As shown in the figure, the reaction layer located at the bottom of the coal gasifier is composed of a lower reaction layer 2 and an upper reaction layer 3, and coal 5 is supplied to each reaction layer via a burner 4.
Oxygen-enriched air 6 is supplied as a gasifying agent. The burner 4 is provided so as to be inclined in the connection direction with respect to the furnace.

Therefore, the coal 5 and oxygen-enriched air 6 injected into the furnace from the burner 4 swirl to form a spouted bed, and the coal 5 is gasified by a reaction such as a pyrolysis reaction. Crude gas 7 generated by gasification is extracted from the top of the furnace and supplied to gas consuming equipment etc. through a char collector 8.

A slag tap 9 is provided below the lower reaction layer M2, and the slag 10 melted in the reaction layer is continuously discharged.

The upper part of the gasifier 1 is used as a heat recovery section 11, and has a water-cooled wall structure.

Since the crude gas 7 contains unreacted char, it is collected by a char collector 8 and circulated to the lower reaction layer 2 of the gasifier 1 to improve efficiency.

In the spouted bed type coal gasifier 1 configured in this way, the pulverized coal that is the fuel reacts within a few seconds in the airflow, so the response is quick and load following operation is easy. It is necessary to maintain high gasification efficiency even during operation, and to ensure conditions for melting the generated coal ash and stably discharging it as molten slag.

Generally, the gasification efficiency in a coal gasifier requires Co,
There are two types: carbon gasification rate, which represents the proportion of carbon in coal that has been converted to gas such as CO2, and cold gas efficiency, which represents the ratio of the generated gas to the calorific value of coal. The difference can be considered as the proportion of sensible heat of the produced gas. In the coal gasifier 1, it is important to improve the efficiency of both at the same time and how to recover and effectively utilize the sensible heat of the generated gas in order to improve the thermal efficiency of the entire plant such as a power generation plant.

On the other hand, in the spouted bed type coal gasifier 1, coal is converted into H2, Co, etc. through a partial combustion reaction, and at the same time, the generated heat raises the temperature, and the ash content in the coal melts and becomes slag 10. This slag 10 flows down the furnace wall and is discharged from the slag tap 9. However, unless the temperature of at least the lower reaction layer 2 is maintained above the melting point of the slag 10, the slag 10 flows down the furnace wall and is discharged from the slag tap 9. 9, which makes it impossible to operate the furnace. The melting point of the slag 10 mainly depends on the properties of the coal 5, but even if the ash has a high melting point, it is necessary to maintain the molten state of the slag and allow it to flow down stably to perform a stable gasification process. .

The above-mentioned gasification efficiency and slag flow stability are controlled by the amount of oxygen supplied to the gasifying agent. FIG. 3 shows the relationship between the theoretical gasification temperature, gasification efficiency, and gas calorific value with respect to the oxygen ratio (oxygen supply amount/coal supply amount). As can be seen from the figure, increasing the oxygen ratio increases the gasification temperature and the carbon gasification rate ηC, but the cold gas efficiency ηG is
It decreases from around 0.81. This is because the CO2 concentration in the generated gas increases and the gas calorific value decreases from a certain oxygen ratio. On the other hand, the higher the temperature inside the gasifier, the easier it is to melt the coal ash and the easier it is for the slag to flow down.

Therefore, the stable flow of slag and the carbon gasification rate ηC
In terms of improving the oxygen ratio, the higher the oxygen ratio, the better, but on the other hand, there is a problem that the gasification efficiency decreases.

As described above, in the spouted bed type coal gasifier, it is necessary to reduce the oxygen ratio as much as possible to increase the cold gas efficiency ηG and to allow the slag to flow stably.

[Problem that the invention seeks to solve]

By the way, the heat loss of the coal gasifier 1 is determined by the peak temperature of the burner, and is substantially constant regardless of the magnitude of the load. Therefore, if the oxygen ratio is kept constant while the load is reduced, the temperature of the lower reaction layer 2 will drop below the melting point of the ash, making it difficult to discharge the slag 10 and causing the coal gasifier 1 to malfunction. It becomes possible.

For these reasons, conventional coal gasifiers either operate at a slightly higher oxygen ratio in advance or adjust the oxygen ratio depending on the load.

According to the former method of supplying a high oxygen ratio, there is a problem that gasification efficiency deteriorates under high loads.

On the other hand, according to the latter method of adjusting the oxygen ratio by load, the gasifying agent with the same oxygen ratio as the lower reaction layer 2 is supplied to the upper reaction layer 3, so the melting temperature of the slag can be maintained, but the gasification There is a problem that efficiency decreases.

In addition, in the case of using oxygen-enriched air as the gasifying agent and supplying it separately to the upper and lower reaction layers, as in the above-mentioned conventional example or Japanese Patent Application Laid-open No. 58-80381, the oxygen As the ratio becomes larger, the oxygen production equipment becomes larger, which causes a problem in that the total energy efficiency decreases and economic efficiency deteriorates.

The object of the present invention is to provide a spouted bed coal gasifier that can maintain high gasification efficiency in response to changes in furnace conditions such as load fluctuations, maintain stability of slag flow, and reduce pure oxygen consumption. The goal is to provide a driving method.

[Means for solving problems]

In order to achieve the above object, the present invention has a spouted bed formed to gasify the coal by forming a spouted bed with coal and a gasifying agent, and to cause the generated slag to flow down to the bottom of the furnace and be discharged. In a method for operating a type coal gasifier, air is used as the gasifying agent, and the amount of air is adjusted based on a total oxygen ratio determined in accordance with the load, while oxygen-enriched air is supplied to the lower part of the reaction bed. The temperature of the lower part of the reaction layer is maintained at a predetermined value by adjusting the amount of oxygen-enriched air supplied.

[Effect]

That is, the present invention basically lowers the gasification temperature by using air as the gasification agent, thereby increasing the gasification efficiency and
In particular, the cold gas efficiency is maintained high, and one lower reaction layer is maintained above the slag melting point by the supplied oxygen-enriched air. As a result of adjusting the gasification efficiency and adjusting the temperature of the lower reaction layer separately, it is possible to maintain a high gasification rate by adjusting the air even if the load on the gasifier fluctuates. On the other hand, by regulating the oxygen-enriched air, the stability of the slag can be easily maintained. Moreover, since the amount of oxygen-enriched air consumed can be reduced to just the amount needed to maintain the temperature of the lower reaction layer, the oxygen generator can be small.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

FIG. 1 shows the overall configuration of an embodiment of an apparatus to which the present invention is applied. In this figure, since the coal gasifier 1 has the same configuration as the conventional example shown in FIG. 2, it is schematically shown in a simplified manner.

Oily air 31 as a gasifying agent is supplied from a compressor 22 of a gas turbine device 20 to a lower reaction layer 2 and an upper reaction layer 3 of the coal gasifier 1 . The respective air supply amounts can be adjusted by air amount adjustment valves 12,13.

Further, oxygen-enriched air 32 is produced in the oxygen production device 30 using the oily air 31 as a raw material, and the oxygen-enriched air amount control valve 14
It is supplied to the lower reaction layer 2 via.

Coal 5 is adjusted to an amount according to the load (or air supply amount) via coal amount regulators 15 and 16, and is supplied to lower reaction layer 2 and upper reaction layer 3, respectively. The crude gas 7 generated in the coal gasification furnace 1 is sent to the heat recovery device 17 after the char is separated and removed by the char collector 8, and is converted into crude gas by exchanging heat with a heat exchange medium and generating steam. Sensible heat of gas 7 is recovered. Thereafter, the crude gas 7 is guided to the gas purification device 4, where dust and reactive compounds such as sulfur contained in the gas are removed and purified, resulting in a coal production gas 71.

The generated gas 71 is supplied to the combustor 21 of the gas turbine device 20, and reacts with high pressure air 23 as an oxidizing agent pressurized by the compressor 22 to generate combustion gas 24. This combustion gas 14 is guided to a gas turbine 25 and drives the gas turbine 25. A part of the power generated by the gas turbine 25 is used to drive the electric motor 26 to generate electric power.

The majority of the gas turbine power is used to drive the compressor 22. A part of the high pressure air 23 discharged from the compressor 22 is used as air 31 as a gasifying agent in the coal gasifier 1.
The gas is extracted as gas, and the pressure is increased to a predetermined pressure by the boost compressor 33, and the air is sent to the coal gasifier 1.

On the other hand, the exhaust gas 28 of the gas turbine 25 is sent to the exhaust heat recovery boiler 29 to generate high-temperature, high-pressure steam, which drives a steam turbine (not shown), rotates a generator connected to it, and generates electricity. is configured to occur.

The operating method of the embodiment configured as described above, especially the air 31
Next, the adjustment of the oxygen-enriched air 32 will be explained.

As shown in Figure 3, using oxygen-enriched air 32 makes it possible to increase the calorific value of the generated gas, but on the other hand, the cost of producing oxygen-enriched air 32 is incurred, so the entire power generation plant Therefore, in a load zone where the plant is frequently operated, it is a good idea to perform air blowing operation using only the bleed air 21 without using the oxygen-enriched air 32 as much as possible. be.

Therefore, the oxygen ratio of the coal gasifier 1 is adjusted by the oxygen ratio on an air injection basis, and the adjustment of the oxygen-enriched air 32 is excluded from the oxygen ratio control. In other words, the coal gasifier 1 is basically operated with air blowing. In this case, in order to improve the efficiency of the coal gasifier 1, the oxygen ratio is selected to be as small as possible considering the load operation range. The oxygen-enriched air 32 is used by supplying the oxygen-enriched air 32 to the lower reaction layer 2 only when the temperature of the lower reaction layer 2 of the coal gasifier 1 falls below a predetermined value. The reaction temperature is increased by increasing the oxygen ratio of 2 to 2 to maintain the molten flow of the slag.

Here, a method for setting the oxygen ratio will be explained using FIG. 4. The figure shows the relationship between the theoretical gasification temperature by air oxidation in the coal gasifier 1 and the oxygen ratio. Line a is for 100% load, line a is for 50% load, and The minimum operating temperature for melting and discharging slag in the coal gasifier 1 is set to 1700°C. For example, if the oxygen ratio is set at point A, the slag cannot be melted and discharged below the rated load, so the oxygen ratio is set at a slightly higher point B. Even if it is set at point B, when the load of the coal gasifier 1 decreases to 50%, the point becomes 0, which is the lower limit temperature for slag melting and discharge operation. Therefore, when this point C is reached, the supply of oxygen-enriched air 32 to the lower reaction layer 2 is started.

As described above, according to this embodiment, the gasification efficiency can be maintained high even when the load fluctuates, and the stability of slag flow can be maintained.

Furthermore, since air is basically used as the gasifying agent, the amount of oxygen-enriched air consumed can be reduced, thereby making it possible to downsize the oxygen generator and improve economic efficiency.

In addition, the structure of one example of the concrete automatic control device which implements the supply amount adjustment method of the air 31 and the oxygen-enriched air 32 of the said Example is shown.

The oxygen ratio determined by the method described above is set in advance in the oxygen ratio setting device 51, and the oil/air air 31 detected by the flow rate detector is
Coal amount regulators 15 and 16 control the amount of coal supplied to the coal gasifier 1 based on the flow rate signal.

On the other hand, the load signal 60 of the plant is given to the air quantity control device 61, and the oil/air quantity 3
Control 1.

On the other hand, the reaction temperature of the lower reaction layer 2 is detected by the temperature detector 65, and the oxygen-enriched air amount control valve 14 is controlled so that the reaction temperature becomes equal to or higher than the melting temperature of the slag, so that the oxygen-enriched air 22 is supplied to the lower reaction layer 22. It is supplied to the reaction layer 2, increasing the oxygen ratio only in the lower reaction layer 2, and maintaining the reaction temperature high.

In reality, the temperature of the lower reaction layer 2 is close to 2000°C, and it is extremely difficult to directly measure the temperature. Therefore, other state values correlated to the reaction temperature of the lower reaction layer 2,
For example, it is also possible to substitute the temperature of the crude gas 7 at the outlet of the coal gasifier 1.

In addition, if the relationship between the load, oxygen ratio, and reaction temperature has been obtained in advance through experiments, it is possible to control the oxygen-enriched air amount 32 based on the load, or to control the oxygen-enriched air amount 32 based on the You may also combine the status values.

In the embodiments shown in FIGS. 1 and 5, the oxygen-enriched air 32 is directly supplied to the lower reaction layer 2; You may also do so. In this case, it is injected into the downstream piping of the control valve 12.

Further, according to the embodiments shown in FIGS. 1 and 5, oxygen-enriched air 32 is supplied to the lower reaction layer 2 independently of the air 31 as the main gasifying agent to control the temperature of the lower reaction layer 2. Since the temperature is maintained above the slag melting point, it is possible to effectively cope with other causes of reaction temperature reduction (disturbances) other than the oxygen ratio, and to achieve protection of the coal gasifier. In addition,
Such disturbances include sudden load changes, delays in the air for gas and other agents following load changes, changes in the properties of coal, and changes in the amount of char recycled.

In particular, since the char reflux amount can be 20 to 30% of the coal supply amount, fluctuations in the char distal flow amount have a large effect on the lower reaction layer 2, but conventionally no consideration has been given to this fluctuation. However, according to the present invention, since the temperature of the lower reaction layer 2 is directly controlled, it is effective against such disturbances.

〔Effect of the invention〕

According to the present invention, since the method is used to back up oxygen-enriched air regardless of the overall oxygen ratio in accordance with the reaction temperature of the lower reaction layer, the function of the spouted bed coal gasifier is
This has the effect of making it easier to maintain the most important melting temperature of the slag, and maintaining the stability of the slag flow in response to load fluctuations and disturbances.

As a result, it is possible to use air as the gasifying agent in the coal gasifier and operate it with a lower oxygen ratio.
The gasification efficiency of a coal gasifier can be increased. Furthermore, since oxygen consumption can be reduced, economical efficiency is improved.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of an embodiment of an apparatus to which the present invention is applied, and FIG. 2 is a sectional view of a general spouted bed coal gasifier.
Fig. 3 is a diagram showing the relationship between oxygen ratio, gasification efficiency, gas calorific value, and theoretical gasification temperature, Fig. 4 is a diagram explaining the method of setting the oxygen ratio in the first embodiment, and Fig. 5 is a diagram showing the relationship between the oxygen ratio and gasification efficiency, gas calorific value, and theoretical gasification temperature. 1 is a system configuration diagram of an embodiment of an automatic control device that is a main part of the invention. 1... Coal gasifier, 2... Lower reaction layer, 3...
Upper reaction layer, 12, 13.14... control valve, 15.16
...Supply amount control valve, 31...Air, 32...Oxygen enriched air, 51...Oxygenation set value, 65...Temperature detector.

Claims (1)

[Claims] 1. A spouted bed type coal gas formed to gasify coal by forming a spouted bed with coal and a gasifying agent, and to cause generated slag to flow down to the bottom of the furnace and be discharged. In the method for operating a chemical reactor, air is used as the gasifying agent, and the amount of air is adjusted based on a total oxygen ratio determined in accordance with the load, while supplying oxygen-enriched air to the lower part of the reaction layer,
A method of operating a spouted bed coal gasifier, which comprises adjusting the amount of oxygen-enriched air to maintain the temperature of the lower part of the reaction bed at a predetermined value or higher. 2. The method of operating a spouted bed coal gasifier according to claim 1, wherein the total oxygen ratio is set to a constant value over a constant load fluctuation range. 3. The spouted bed type according to claim 1, wherein the amount of oxygen-enriched air supplied to the lower part of the reaction layer is adjusted to a predetermined value depending on the state value of the gasifier load. How to operate a coal gasifier. 4. The amount of oxygen-enriched air supplied to the lower part of the reaction layer is adjusted based on the detected temperature at the lower part of the reaction layer or the state value of the gasifier that is correlated to this detected temperature. A method for operating a spouted bed coal gasifier according to scope 1.