JPH073185B2 - Exhaust gas pressure recovery turbine bypass valve control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for controlling a bypass valve provided in a gas turbine for recovering exhaust gas pressure energy of an industrial furnace operated at high pressure.

[Prior Art] In an iron-making blast furnace (hereinafter referred to as a blast furnace), it is common practice to increase the gas pressure in the reaction zone in the furnace to increase the iron output, and to reduce the pressure energy of the exhaust gas. In order to recover the gas, the speed control valve of the gas turbine is controlled so that the blast furnace top gas pressure becomes the value set by the furnace top gas pressure setter, the turbine is operated by the passing energy, and it is converted into electric power by the directly connected generator. We are trying to recover energy.

Since the capacity of the turbine is smaller than the maximum amount of gas discharged from the furnace from the viewpoint of investment efficiency, a bypass valve is installed in the turbine for control when the amount of gas is large, and a bypass valve that operates depending on the gas pressure at the furnace top is used. It is controlled by the meter.

FIG. 3 is a block diagram of a gas flow rate adjusting circuit of a conventional exhaust gas pressure recovery turbine, where 1 is a blast furnace, 2 is a turbine for recovering exhaust gas pressure energy from the blast furnace 1, 3 is a governor of the turbine 2, and 4 is a governor 3. An open / close speed control valve, 5 is a generator directly connected to the turbine 2, 6 is a top gas pressure transmitter installed at the top of the blast furnace 1, and 7 is a top pressure setting device that is a control target of the governor 3. , 8 is a bypass valve that connects the gas inlet and outlet of the turbine 2, 9 is a bypass valve controller that controls the opening of the bypass valve 8, and 10 is a bypass valve that is set to a pressure slightly higher than the furnace top pressure setting device 7. It is a bypass pressure setting device that is a control target of the controller 9.

Since the top pressure of the furnace fluctuates drastically within a short period of time, the bypass valve 8 may open and close frequently even on average in the control range of the speed regulating valve 4, which causes a problem in maintenance. When is less than the set value, the servo control gain of the bypass valve controller 9 is lowered to prevent the bypass valve 8 from frequently operating. When the gas pressure becomes equal to or higher than the set value, the bypass valve controller 9 is made to operate normally, and the gas that cannot be processed by the turbine 2 is released by the bypass valve 8.

FIG. 4 is a graph showing an example of the transition of the furnace top gas pressure and the operation of the bypass valve 8, where (a) is the opening of the speed control valve 4,
(B) is the top gas pressure, (c) is the opening of the bypass valve 8,
(D) shows the control sensitivity of the bypass valve controller 9.
When the gas pressure at the top of the furnace becomes greater than the set value at point 12, the bypass valve controller 9 is set to the normal sensitivity (hereinafter sometimes referred to as high sensitivity), and the bypass valve 8 opens rapidly to cause an abnormal rise in the gas pressure at the top of the furnace. To prevent.

[Problems to be Solved] When the speed control valve 4 of the exhaust gas pressure recovery turbine 2 is fully opened and the total amount of gas cannot be contained, the furnace top gas pressure gradually rises and the furnace top gas pressure is controlled by the bypass valve 8. Will be. In that case, the bypass valve controller 9 is operated with high sensitivity. After that, when the gas pressure at the top of the blast furnace 1 is restored due to a change in the inside of the blast furnace 1, the bypass valve controller 9 switches from high sensitivity to low sensitivity operation, and it takes a long time to fully close the bypass valve ( Figure 4, line 13). This causes fluctuations in the furnace top pressure or a decrease in power generation.

The present invention is intended to solve the above problems, and to obtain a control method of an exhaust gas pressure recovery turbine bypass valve, in which the furnace outlet gas pressure is made constant while suppressing excessive opening and closing, and the amount of energy recovery is improved. With the goal.

[Means for Solving the Problems] In the method for controlling an exhaust gas pressure recovery turbine bypass valve according to the present invention, the control sensitivity of the bypass valve is set to be normal when the gas pressure at the furnace outlet is higher than a predetermined set pressure, and the furnace outlet is provided. When the gas pressure is less than the set pressure and the bypass valve opening is less than or equal to a predetermined amount, the sensitivity is low.

[Operation] Conventionally, the servo control sensitivity of the bypass valve controller 9 is switched by the inlet gas pressure. However, when the amount of gas decreases faster than the movement of the bypass valve 8 when the amount of gas decreases, the amount of bypass gas becomes excessive and the inlet gas pressure drops, which also switches the control sensitivity of the bypass valve controller 9 to low. , The bypass valve 8 remained open and slowed down.

In the present invention, the switching condition from high sensitivity to low of the bypass valve controller 9 is characterized in that the opening degree of the bypass valve 8 is taken into consideration in addition to the low inlet gas pressure. Do not switch the sensitivity from high to low when the opening of the bypass valve 8 is a predetermined value or more so that the control operation is not delayed and the gas is unnecessarily released while the valve 8 is open. I have to.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to the drawings.
The above-mentioned reference numerals indicate the same parts, and the description thereof will be omitted.

FIG. 1 is a block diagram of a gas flow rate adjusting circuit of an exhaust gas pressure recovery turbine by a method of controlling an exhaust gas pressure recovery turbine bypass valve as one embodiment, and 11 is an operation for switching a control gain of a bypass valve controller 9 It is a vessel.

FIG. 2 is a flow chart showing the control operation of the calculator 11. In step 31, the furnace top pressure signal Pt from the furnace top gas pressure transmitter 6 and the bypass set pressure Pb set in the bypass pressure setter 10 are set. Read in.

At step 32, the furnace top pressure signal Pt is compared with the bypass set pressure Pb, and if Pt is small, the routine proceeds to step 34. If Pt is large, in step 33, a command is issued to the bypass valve controller 9 to make it highly sensitive, and the process proceeds to step 39.

In step 34, the bypass valve opening Yb is read from the command output voltage of the bypass valve controller 9, and in step 35, the bypass valve opening Yb is the predetermined opening α%,
For example, 5%, and if larger, go to step 39. If the bypass valve opening Yb is small, in step 36, the governor opening is determined from the command output voltage of the governor 3.
Yg is read, and in step 37, the governor opening Yg is β%, for example 90%, and if it is larger, the process proceeds to step 39. If the governor opening Yg is small, in step 38, a command is issued to the bypass valve controller 9 to set it to low sensitivity.

In step 39, it is judged whether or not the calculation is continued by referring to the operation switch on the operation panel. If it is continued, the process returns to step 31, and if it is not continued, this program is terminated.

The apparatus of this embodiment is configured in this way and operates as follows.

The exhaust gas of the blast furnace 1 is guided to the exhaust gas pressure recovery turbine 2 and gives pressure energy to the turbine 2, and the generator 5 generates electric power. A speed control valve 4 is provided at the gas inlet of the turbine 2 and is controlled so that the furnace top gas pressure becomes constant.
FIG. 5 is a graph showing an example of changes in the furnace top gas pressure and the like during the operation of this embodiment, (a) is the speed control valve 4 opening,
(B) is the top gas pressure, (c) is the bypass valve 8 opening,
(D) shows the control sensitivity of the bypass valve controller 9.

When the amount of blast furnace generated gas exceeds the capacity of the turbine 2, the furnace top pressure rises. By the pressure increase, the bypass valve controller 9 is switched to high sensitivity, and the bypass valve 8 is opened and closed at a regular speed to prevent the furnace top pressure from rising excessively. Next, when the amount of blast furnace generated gas decreases, the furnace top pressure decreases, and the speed control valve 4 and the bypass valve 8 enter the closing operation. In the present embodiment, unlike the conventional case, the bypass valve controller 9 remains at the high sensitivity setting, so that the bypass valve 8 rapidly closes (see FIG. 5, line).
14).

When the amount of gas continues to decrease and the opening degree of the bypass valve becomes α% or less, the bypass valve controller 9 is set to low sensitivity for the first time.
It is in a state where it prevents sensitive opening and closing movements.

In this way, the operation of the bypass valve 8 in the closed period is quicker than in the conventional case, so that the amount of gas pressure energy that has escaped via the bypass valve 8 can be suppressed, and with the increase in the generated power amount, Fluctuations in the furnace top pressure can be reduced.

Note that, in the low sensitivity command to the bypass valve controller 9, the low sensitivity command is not issued when the governor opening is close to full opening as in step 37, and the bypass valve operation is delayed in the bypass valve low sensitivity control state. It is also possible not to cause an abnormal rise in the furnace top pressure.

[Advantages of the Invention] In the method for controlling an exhaust gas pressure recovery turbine bypass valve of the present invention, the control sensitivity of the bypass valve is made normal when the gas pressure at the furnace outlet is higher than a predetermined set pressure, and the gas pressure at the furnace outlet is Since the sensitivity is low when the bypass valve opening is smaller than the set pressure and equal to or less than a predetermined amount,
The bypass valve can be closed at high speed, the gas pressure at the top of the furnace is stable, the operating conditions of the blast furnace are stable, and the gas energy that was conventionally flowing through the bypass valve is efficiently recovered, resulting in great economic benefits. Obtainable.

[Brief description of drawings]

FIG. 1 is a block diagram of a gas flow rate adjusting circuit of an exhaust gas pressure recovery turbine by an exhaust gas pressure recovery turbine bypass valve control method as one embodiment, and FIG. 2 is a flow chart showing a control operation of an arithmetic unit of the embodiment, Fig. 3 is a block diagram of a gas flow rate adjusting circuit of a conventional exhaust gas pressure recovery turbine, Fig. 4 is a graph showing the operation of a furnace top gas pressure and a bypass valve, etc. by the conventional method, and Fig. 5 is the method of the above embodiment. It is a graph which shows operation | movement of a furnace top gas pressure and a bypass valve. 1 ... Blast furnace, 2 ... Turbine, 3 ... Governor, 4 ... Regulator, 5 ... Generator, 6 ... Top gas pressure transmitter, 7 ...
… Furnace top pressure setting device, 8 …… Bypass valve, 9 …… Bypass valve controller, 10 …… Bypass pressure setting device, 11 …… Computing device.

Claims (1)

[Claims] 1. A bypass valve of an exhaust gas pressure recovery turbine installed in an exhaust gas system at the outlet of a high-pressure operation furnace for recovering gas pressure energy and having a short circuit between the gas inlet and the gas outlet and controlled by the gas pressure at the furnace outlet. The control sensitivity of the bypass valve is normal when the gas pressure at the furnace outlet is higher than a predetermined set pressure, the gas pressure at the furnace outlet is smaller than the set pressure, and the bypass valve opening degree. The method for controlling an exhaust gas pressure recovery turbine bypass valve is characterized in that the sensitivity is low when is less than or equal to a predetermined amount.