JPH02119698A - Flow control device of compressor - Google Patents

Abstract

PURPOSE:To avoid an increase of power consumption and the dange of the occurrence of surging phenomenon by providing a polytropic head calculator for calculating the polytropic head and a function generator for outputting a preset value of a flow controller. CONSTITUTION:A temperature gauge 11 detects the gas temperature Ts of gas flowing in a compressor 1. A pressure gauge 12 detects the pressure Ps of gas flowing in the compressor 1, and a pressure gauge 13 detects the pressure PD of gas flowing out of the compressor 1. The detection value Ts, Ps and PD are input to a polytropic calculator 14 to calculate the polytropic head H. The polytropic head H is input to a function generator 15 to calculate the set flow of a flow controller 8. Thus, an increase of power consumption in case of low rotational frequency and the dange of the occurrence of surging phenomenon in case of high rotational frequency can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a flow rate control device for preventing a surging phenomenon in a compressor for increasing the pressure of gas, such as a compressor station in a gas pipeline or a compressor in an ammonia plant.

Prior Art FIG. 3 is a process flow diagram of a compressor showing a conventional flow rate control device. In FIG. 3, reference numeral 1 is a compressor, 2 is an inflow line, 3 and 4 are piping, 5 is a reflux line, 6 is a control valve, 7 is an outflow line, 8 is a flow rate controller, 9 is a flow meter, and 10 is a Each drive machine is shown.

Gas is supplied to the compressor 1 from piping 3 via inflow line 2.
The pressurized gas flows out from the outflow line 7 through the pipe 4. Further, a reflux line 5 is installed between the piping 4 and the piping 3, and a regulating valve 6 is installed in the reflux line 5. Further, a flow meter 9 for detecting the volumetric flow rate of gas is installed in the pipe 3, and a flow rate controller 8 adjusts the control valve 6 so that the flow rate is constant. This flow rate control is generally called surging prevention control. In other words, the surging phenomenon occurs when the suction volumetric flow rate of the compressor 1 becomes less than a predetermined amount.
The control valve 6 is opened to increase the flow rate to the compressor l.

Problems to be Solved by the Invention FIG. 4 shows a performance curve of a compressor, in which the horizontal axis represents the volumetric flow rate at the compressor inlet, the vertical axis represents the polytropic head, and the parameter represents the compressor rotation speed.

In the conventional flow rate control device, the setting value of the flow meter 8 is set to a constant value Q8o as shown by the dashed-dotted line in FIG. Therefore, when the compressor flow rate Qs becomes smaller than the set value Q8o, the control valve 6 of the reflux line 5
is opened to prevent the compressor flow rate from becoming smaller than the set value Qso, thereby preventing the surging phenomenon from occurring.

However, since the set value Qso is constant regardless of the compressor rotation speed, the compressor operates away from the surging line when the rotation speed is low, and close to the surging line when the rotation speed is high.

When the rotational speed is low, the compressor is operated away from the surging line, so the flow rate of the recirculation line is increased to increase the compressor flow rate, which increases the power consumption of the compressor. On the other hand, when the rotational speed is high, the engine is operated near the surging line, so there is a risk that surging will occur.

The present invention has been made in view of the above-mentioned circumstances.The present invention has been made in such a way that the compressor volume flow rate set value is set at approximately the same position from the surging line at any rotation speed, thereby reducing the increase in power consumption at low rotation speeds and reducing the increase in power consumption at low rotation speeds. An object of the present invention is to provide a flow rate control device that eliminates the risk of surging phenomenon occurring at times.

Means for Solving the Problems According to the present invention, there is provided a control valve installed in a gas recirculation line between a gas inflow line and a gas outflow line of a compressor, a flowmeter for detecting a compressor inflow flow rate, and the flowmeter. A flow rate controller for a compressor, comprising: a flow rate controller that adjusts the opening degree of the control valve based on a detected value;
a thermometer that detects the gas temperature of the gas flowing into the compressor;
A calculation formula using a second pressure gauge that detects the pressure of the compressor outflow gas, a detected value P8 of the first pressure gauge, a detected value P of the second pressure gauge, and a detected value TS of the thermometer as input. (% formula %) Here, al and a represent a polytropic head calculator that calculates the polytropic head H from constants, and a function generator that uses the polytropic head as input and outputs the setting value of the flow rate controller. A compressor flow rate control device is provided, further comprising: a flow rate control device for a compressor;

In the present invention, the pressure and temperature of the compressor inflow gas and the pressure of the compressor outflow gas are detected, the polytropic head is calculated from these detected values, and from this the set value of the flow rate controller is set slightly away from the surging line. I'm trying to set it up in parallel.

Example The present invention will be described in detail below with reference to FIGS. 1 and 2.

FIG. 1 is a process flow diagram of a compressor showing a flow rate control device for a compressor according to the present invention. According to FIG. 1, in addition to the conventional flow control device shown in FIG.
A thermometer 11, a pressure gauge 12, 13, a polytropic head calculator 14, and a function generator 15 are newly installed.

A thermometer 11 is provided in the pipe 3 to detect the gas temperature Ts of the gas flowing into the compressor. A pressure gauge 12 is provided in the pipe 3 to detect the pressure Ps of the compressor inflow gas temperature,
The pressure gauge 13 is provided in the pipe 4 and detects the pressure PD of the compressor outflow gas. These detected values Ts, Ps, P
D is input to the polytropic head calculator 14, and the polytropic head H is calculated according to the following equation.

H=aI−Ts・((Po/Ps)”I)・
...(1) al, constant 1 a, constant 2 Equation (1) is the basic equation... (2): Compressibility coefficient Absolute gas constant 2 Gravity acceleration average molecular weight Specific heat ratio In polytropic efficiency, the compressor is Assuming that the flowing gas components do not change, the compressibility coefficient Z, which is a gas physical property, and the average molecular fi
1M, the specific heat ratio is considered to be constant, and the polytropic efficiency is also considered to be almost constant, so it can be considered as a constant. Therefore, it is sufficient to set a + +a as a constant in the polytropic head calculator 14 in advance.

Next, the polytropic head H, which is the output value of the polytropic head calculator 14, is input to the function generator 15 to calculate the set flow rate of the flow rate controller 8. The function f(H) of the function generator 15 is set parallel to the surging line, as shown by the dashed line in FIG.

The surging line itself can be used as the function f(H), but considering the delay in the operation of the control valve 6 and the detection delay of the flow meter 9, it is necessary to set the surging line a little away from the surging line, allowing for a certain degree of safety factor. It is preferable to use the function f(H) as a function f(H).

Furthermore, the output value of the function generator 15, that is, the flow rate indicated by the dashed dotted line in FIG. Operate the control valve 6.

Effects of the Invention According to the flow rate control device of the present invention, the compressor flow rate setting value can be maintained at a value parallel to the surging line as shown by the dashed line in Fig. 2, so that the original function of preventing surging phenomenon is not fulfilled. At the same time, the risk of increased power consumption due to excessive flow rate when the rotational speed is low and the risk of surging occurring when the rotational speed is high, which is the case with conventional devices, is eliminated.

[Brief explanation of the drawing]

FIG. 1 is a process flow diagram showing the flow rate control device according to the present invention, FIG. 2 is a diagram showing the compressor performance curve and the set flow rate of the device of the present invention, FIG. 3 is a process flow diagram showing the conventional device, and FIG. FIG. 3 is a diagram showing a compressor performance curve and a set flow rate of a conventional device. ■... Compressor, 2... Inflow line, 3° 4... Piping, 5... Reflux line, 6... Control valve, 7... Outflow line, 8... Flow fl controller, 9... Flow meter, 10...Driver, 11...Thermometer, 12.13...Pressure gauge, 14...
Polytropic head calculator, 15...Function generator. Fig. Fig. Fig. kelp and 9-ri°X mouth rice J1 series. Figure 1

Claims (1)

[Scope of Claims] A control valve installed in a gas recirculation line between a gas inflow line and a gas outflow line of the compressor, a flow meter for detecting the flow rate of the inflow to the compressor, and a detected value of the flow meter to detect the control valve. A flow rate controller for a compressor is equipped with a first pressure gauge that detects the pressure of the gas flowing into the compressor, a thermometer that detects the gas temperature of the gas flowing into the compressor, and a first pressure gauge that detects the pressure of the gas flowing into the compressor; A second pressure gauge that detects the pressure of the gas, a detected value P_S of the first pressure gauge, a detected value P_D of the second pressure gauge, and a detected value T_S of the thermometer are used as input to calculate formula H= a
_1・T_S・{(P_D/P_S)^a_2-1} Here, a_1 and a_2 are a polytropic head calculator that calculates the polytropic head H from a constant, and a polytropic head calculator that calculates the polytropic head H from a constant, and a A flow rate control device for a compressor, further comprising a function generator that outputs a set value.