JPH0678534B2 - Coal gasifier control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gasification furnace for gasifying coal by partial oxidation, which is produced when it is required to operate while changing the amount of produced gas. The present invention relates to a control device for operating conditions of a gasification furnace for keeping a gas calorific value above a certain value.

[Conventional technology]

When coal is gasified by the partial oxidation method, the factors that govern the calorific value of the produced gas are gasification temperature, gasification pressure, the flow rate of oxygen-containing gas such as oxygen or air which is a gasifying agent, and coal. Ratio, coal gasification rate, etc. Among these factors, the factors that can be operated as operating conditions are the gasification agent and the flow rate and gasification pressure of coal. The gasification temperature can be controlled to some extent by the preheating temperature of the gasifying agent or the temperature of the cooling medium of the gasification furnace material, but the heat source that keeps the gasification furnace at a high temperature is the reaction heat generated by the partial oxidation reaction of coal. Therefore, if the gasification temperature is determined by the flow rate ratio between the gasifying agent and coal, it is difficult to change the resulting gasification temperature significantly by the preheating temperature of the gasifying agent. Is. The gasification rate of coal is a factor that shows how efficiently the supplied coal reacts with the gasifying agent. If other conditions are constant, the calorific value of the produced gas is higher as the gasification rate is higher. . However, the gasification rate is not a factor that can be directly controlled depending on the operating conditions, because it is determined by the structure of the gasification furnace, the gasifying agent, the coal supply device, etc., the gasification reaction conditions, and the like.

Further, among the factors that can be operated, it is preferable to keep the gasifier pressure at a constant pressure in the case of a commercial-scale device in consideration of the influence on the peripheral equipment of the gasifier. Limited to gradual changes, rapid changes are difficult. Therefore, the factors that can be substantially manipulated as the operating conditions of the gasifier are the flow rate of coal and the gasifying agent that are primarily supplied, and the secondary factors are the gasifying agent preheating temperature, gasification pressure, etc. .

Japanese Unexamined Patent Publication (Kokai) No. 56-79186 discloses an apparatus for controlling the supply amount of coal and a gasifying agent when coal is blown into molten metal for gasification. This known example relates to a gasifier having a different type from the gasifier of the present invention, but control of the gasifying agent has many similarities. This known example is based on a control device that maintains the coal supply amount at a set value, and is equipped with a heating control device for keeping the heating temperature of coal and the gasifying agent constant, and further, coal, gasifying agent, and produced gas. Each temperature
It is intended to comprehensively determine the flow rate of the gasifying agent from the flow rate and the temperature in the gasification furnace.For example, the temperature of each part during start-up operation and steady operation, especially the temperature in the gasification furnace as much as possible The main purpose is to prevent solidification of the molten metal by controlling so as not to change. In the state where the coal supply amount is kept almost constant, it is possible to keep the generated gas calorific value substantially constant by keeping the gasifier temperature constant against fluctuations in the coal supply amount as disturbance. For gas production equipment that does not require a large change in the generated gas flow rate,
As a control device, the above-mentioned publicly known examples are considered to fulfill a sufficient function.

[Problems to be solved by the invention]

On the other hand, when the generated gas is guided to a power generation facility such as a gas turbine and used as fuel without storing the generated gas, it is necessary to adjust the generated gas generation amount according to the target calorific value, and It is required that the gas calorific value be constantly controlled within a range that is acceptable as fuel. In recent years, thermal power generation requires an increase / decrease rate of load of at least about 3% per minute in operation, and the gasification furnace combined with this needs to change the amount of generated gas almost in proportion to the increase / decrease of load. If the gasifier temperature is controlled to be constant as in this prior art, the heat loss from the furnace is basically unchanged even if the load changes, so it must occur in the gasifier at low load. The relative proportion of the required exothermic reaction amount to the calorific value of the supplied coal increases, and the calorific value of the produced gas decreases. Also, if the generated gas calorific value can be detected according to the furnace temperature, the generated gas calorific value can be kept constant by the same control as the conventional technology, but dust can be generated at high temperature and high pressure like a spouted bed gasification furnace. To detect the calorific value of the contained gas, a part of the gas is sampled and cooled.
After removing dust, it must be burned in a special combustor to directly measure the calorific value, or the composition must be analyzed by a gas chromatograph, etc. and calculated indirectly from the theoretical calorific value of each component. The time delay in the system is large and it is difficult to provide a detection end with a fast response. When the operating conditions of the gasification furnace change slowly, it is possible to control the calorific value of the generated gas by using a detection end with a large time delay, but in the case of an operation such as a power plant where the load fluctuation is significantly large and the rate of change is large, Proper control cannot be achieved at the heat generation amount detection end with a large time delay.

The object of the present invention is a detection end which is inferior in the measurement accuracy of the generated gas calorific value but which detects the gasifier operating state with good response, and a detection end which is excellent in the calorific value measurement accuracy of the gasifier generated gas but has a slow response. Is used at the same time, and the information obtained from both detected amounts is reasonably feedback-controlled, so that the calorific value of the generated gas is controlled to be substantially constant even during load changes.

[Means for solving problems]

The purpose of the above is to determine the coal supply amount according to the load change and control the gasification agent supply amount so that the state amount detected by the first detection end with good responsiveness becomes the set value, while the response is slow. Wait until the generated gas calorific value is accurately detected at the second detection end, and at the time when the generated gas calorific value is detected at the second detection end, compare this with the calorific value set value, and according to the error, This is achieved by configuring a control loop that changes the set value of the state quantity detected at one detection end.

〔Example〕

Hereinafter, the configuration of the present invention will be described in more detail with reference to FIG.
FIG. 1 shows a connection structure of a control block suitable for embodying the present invention. The coal supply amount set value 1 given according to the load on the power generation side is compared with the output of the coal supply amount detection circuit 13, and the error of both causes the coal supply amount control device 12 to pass through the compensation circuit 11 configured by a PID controller. The amount of coal supply 2 to the gasifier 40 is controlled and adjusted. On the other hand, the generated gas calorific value set value 3 is compared with the output of the generated gas calorific value detection circuit 32, and due to an error between them, the gasification furnace temperature correction circuit
Add the offset to the gasifier temperature set point 4 through 21,
Further, it is compared with the output of the gasification furnace temperature detection circuit 31. This error is converted into a gasifying agent supply amount set value by the gasifying agent supply amount calculation circuit 22, compared with the output of the gasifying agent supply amount detection circuit 25, and the error is compensated by a compensation circuit 23 composed of a PID controller. The gasifying agent supply amount control valve 24 is controlled to control the gasifying agent supply amount 5 to the gasification furnace 40. The gasification furnace temperature detection signal 6 and the generated gas calorific value detection signal 7 are extracted from the gasification furnace 40, and are respectively supplied to the gasification furnace temperature detection circuit 31.
And the generated gas calorific value detection circuit 32. Among these, the generated gas calorific value detection circuit 32 has a function of holding the calorific value measured immediately before until the generated gas calorific value is newly detected and measured.

Now, the gasifier controlled in Fig. 1 is in a steady state,
When the coal feed rate set value 1 is gradually decreased from a certain point in time, the coal feed rate 2 starts to drop due to the open loop constituted by the blocks 11 to 13. Immediately after this, block 23 ~
Since the gasification agent supply amount 5 is kept constant by the open loop composed of 25, the gasification agent per unit coal supply amount increases, and the operating state of the gasification furnace 40 approaches complete combustion. . This change in state leads to an increase in the temperature of the gasifier and a decrease in the calorific value of the generated gas.First, the temperature rise is fed back through the temperature detection circuit 31, and the gasifying agent supply amount output from the gasifying agent supply amount calculation circuit is output. The set value is lowered, and the closed loop constituted by the blocks 23 to 25 lowers the gasifying agent supply amount toward the new set value. The gasifying agent supply amount continues to decrease until the temperature detection signal 6 of the gasification furnace 40 reaches the previous steady value. During this period, a new measured value of the calorific value of the generated gas is obtained from the generated gas detection circuit 32, and when the calorific value of the generated gas is lower than the set value 3, the temperature correction circuit 21 increases the offset value, apparently. , A low gasification furnace temperature set value, further reducing the gasifying agent supply amount 5 to reduce the gasifying agent supply amount per unit coal supply amount, and recovering the generated gas calorific value.

It should be noted that the present invention is not limited to the type of the detection end installed in the gasification furnace, and the temperature in FIG. 1 and the block related thereto are not limited to other state quantities, for example, the concentration of a specific component in the produced gas. Alternatively, the concentration ratio of the same specific two components and the block relating thereto may be replaced. However, at this time, it is preferable to select a detection end whose response is equal to or less than the gas residence time of the gasification furnace.
In addition, the part related to the calorific value detection in FIG. 1 is such that even at the detection end for quantifying most of the components in the generated gas and calculating the calorific value by a gas chromatograph or the like, a part or part of the generated gas is burned, It may be a detection end for obtaining the calorific value of the gas from the combustion temperature or the like.

By changing the contents of the temperature correction circuit 21, the present invention functions both as a constant control of the generated gas calorific value and as a lower limit control. If necessary, both control methods can be switched according to the conditions. For example, when the generated gas is used as gas turbine fuel, the calorific value of the generated gas in the gasification furnace is the rated value in order to prevent the combustor temperature from rising abnormally during operation at the rated or equivalent load. It is preferable to keep it constant near the combustor temperature during low load operation, so to prevent misfire in the combustor, if the calorific value of the gasifier produced gas can be controlled so as not to fall below the limit value. Good.

As the gasification furnace 40, a spouted bed gasification furnace having a gasification section with an inner diameter of 300 mm and a height of 1,200 mm is used, and when gasifying Pacific coal at a pressure of 4 kg / cm ² G with air preheated to about 150 ° C., Using the control block shown in Fig. 1, the thermocouple installed at the outlet of the gasification furnace as the temperature detection end and the calculated value from the analysis value of the process gas chromatograph for 10 minutes as the heat generation amount detection end were used. , Coal supply from 32kg / h to 14kg / h
Even if it decreases at a rate of 3% per minute, the generated gas calorific value is 75
It could be controlled within the range of 0 to 820 Kcal / kg (lower heating value).

FIG. 2 shows the connection structure of the control block of another embodiment of the present invention, in which the temperature control of the gasifying agent is added to the embodiment of FIG. That is, the output of the temperature correction circuit 21 is branched and led to the gasifying agent preheating temperature compensating circuit 51, and the heating amount of the gasifying agent preheater 52 is controlled so that the output of the temperature correcting circuit 21 becomes zero. The gasifying agent temperature control of the present embodiment is essentially different from the control for keeping the supply temperature of the gasifying agent constant, and the gasifying agent preheating temperature at low load is increased as compared with that at the time of rated operation to lower the gasification furnace temperature. The load reduction limit can be further lowered and the operable range can be expanded. Also, as is clear from the configuration of the control block, the final purpose of temperature control of the gasifying agent is to maintain the calorific value of the generated gas.
It is not to keep the gasifier temperature constant. Therefore, the gasifier steady-state temperature when the partial load is continued does not always match the gasifier steady-state temperature in the rated state, and the degree of difference depends on the characteristics of the para system.

Furthermore, when using the generated gas as gas turbine fuel,
It is also possible to regard the combustion of the generated gas in the gas turbine fuel unit as the gas calorific value detection end and feed back the information. In this case, the gas produced from the gasifier is cooled,
There is a delay of several minutes before reaching the gas turbine combustor, which is the end of the calorific value detection, due to the addition of dust removal, desulfurization, etc., but the control method according to the present invention does not cause any particular problem.

〔The invention's effect〕

According to the present invention, even if the spouted bed coal gasification furnace is operated while varying the coal supply amount, it is possible to suppress the decrease in the calorific value of the generated gas generated from the gasification furnace, and to reduce the heat generation from coal such as a gas turbine. It becomes possible to produce a gas suitable as a fuel.

[Brief description of drawings]

FIG. 1 is a block diagram of a control block according to an embodiment of the present invention, and FIG.
The figure is a block diagram of the control block of another embodiment. 1 ... Coal supply amount setting value, 2 ... Coal supply amount setting, 3 ... Generated gas calorific value setting value, 4 ... Gasification furnace temperature setting value, 5 ...
Gas supply agent supply amount, 6 ... Temperature detection signal, 7 ... Generated gas heat value detection signal, 8 ... Gasification agent temperature, 40 ... Gasification furnace

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Shuntaro Koyama 4026 Kuji-machi, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory Ltd. (72) Inventor Yoshiki Noguchi 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd. Inside the Works (72) Inventor Eiji Kida 6-9 Takaracho, Kure City, Hiroshima Prefecture Papkotsu Hitachi Hitachi Kure Factory

Claims (5)

[Claims] 1. When gasifying coal with a spouted bed gasification furnace using oxygen or an oxygen-containing gas as a gasifying agent, a first detection end for detecting changes in the state of the furnace and a calorific value of generated gas are detected. With a second detection end, the first control loop for controlling the supply flow rate ratio of coal and the gasifying agent by the information obtained from the first detection end, and the second obtained at the second detection end. A control device for a coal gasification furnace, comprising: a second control loop for correcting the control target value of the first control loop based on information on the generated gas calorific value. 2. The method according to claim 1, wherein the concentration ratio of carbon monoxide and carbon dioxide in the gas sampled from the vicinity of the gasifier outlet is used as the information of the first detection end. Control device for coal gasifier. 3. The coal gas according to claim 1, wherein a temperature detection end provided in a gas production line inside or near the gasification furnace is the first detection end. Control device for chemical reactor. 4. The preheating temperature of the gasifying agent according to claim 3, wherein a correction value of the set temperature of the first control loop obtained by the second control loop is used so that correction is unnecessary. A control device for a coal gasification furnace, which controls the 5. The coal gasifier according to claim 1, wherein information calculated from the temperature inside the combustor is used as generated gas calorific value information obtained at the second detection end. Control device.