JP3887972B2 - Gas temperature control method in compressor and compressor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a compressor that can be used in various chemical plants such as a cracked gas compressor for an ethylene plant and a process gas compressor for a butadiene plant, or can be used as a compressor for various refrigeration cycles, an air compressor, and the like. In particular, the present invention relates to a compressor in which the temperature of the compression target gas can be controlled by spraying a cooling liquid onto the compression target gas.
[0002]
[Prior art]
A centrifugal compressor, which is one of the typical compressors for compressing gas, takes in the gas to be compressed from the suction pipe while rotating the impeller fixed in a multistage manner on the rotating shaft, The compression target gas is compressed by applying compression energy to the target gas by rotation of the impeller. In such a compressor, it is difficult to avoid an increase in the temperature of the gas to be compressed as it is compressed.
[0003]
For example, when a centrifugal compressor is used as a cracked gas compressor for an ethylene plant, when the temperature of the gas to be compressed rises to a certain level or higher, a polymer with high viscosity is generated by polymerization of the cracked gas, which is impeller or It adheres to the wall surface of the return flow path, which is the flow path for the gas to be compressed. As a result, the flow path area of the compression target gas is narrowed, leading to a decrease in performance such as a decrease in compression efficiency. For this reason, the compressor generally controls the temperature of the compression target gas by spraying a cooling liquid onto the compression target gas.
[0004]
A conventional general configuration for such temperature control is as follows. That is, a cooling liquid spraying means is provided in the return flow path, and a required amount of the cooling liquid is sprayed onto the compression target gas while being controlled by the control means. As a reference for controlling the spray amount by the control means, the gas weight flow rate measured by the gas weight meter in the suction pipe is used, and usually the control is performed with a maximum of about 3 wt% of the gas weight flow rate as a guide. That is, the required amount of the cooling liquid is controlled at a predetermined weight ratio in accordance with the amount of gas to be compressed that is actually taken in by the compressor.
[0005]
[Problems to be solved by the invention]
The conventional control as described above controls the spray amount of the cooling liquid based on a theoretical estimation using only the compression target gas amount actually taken in by the compressor as an index. For this reason, depending on the actual operating state of the compressor, there is a case where the cooling liquid spray amount becomes excessive and the cooling liquid is not completely vaporized, and this causes the following problems. . That is, the cooling liquid that could not be vaporized flows through the return channel in a gas-liquid mixed state, thereby increasing the risk of causing erosion in the impeller. In addition, the flow of the gas-liquid mixture may cause a non-uniform flow in the return flow path, which may be an excitation source for the impeller, causing unstable vibration and even damage. In addition, if there is a non-vaporized component in the cooling liquid, the amount of drain generated increases, and this drain accumulates in the lower part of the return flow path, thereby narrowing the flow area of the compression target gas and causing a decrease in performance. .
[0006]
With regard to such problems in the prior art, efforts to solve this problem have already been made, as can be seen in, for example, JP-A-10-018976. The technique disclosed in Japanese Patent Laid-Open No. 10-018976 calculates not only the amount of gas to be compressed but also the theoretical saturation amount of the portion where the cooling liquid is sprayed, and controls the spray amount of the cooling liquid based on these indices. To prevent incomplete vaporization. However, this technique is also basically based on theoretical assumptions, and there are insufficient techniques for controlling the spray amount of the cooling liquid that is optimal under actual operating conditions of the compressor.
[0007]
Further, as described above, excessive accumulation of drain in the return flow path leads to a decrease in the performance of the compressor, but none of the conventional techniques considers this problem.
[0008]
The present invention has been made against the background of the above-described conventional circumstances. For a compressor configured to control the temperature of a gas to be compressed, the cooling liquid is always completely transferred under actual operating conditions. The purpose is to provide a gas temperature control method capable of proper vaporization, to provide a compressor capable of executing such a gas temperature control method, and to be able to cope with excessive drain storage The purpose is to provide a machine.
[0009]
To accomplish the above object, controls the temperature of the compressed gas by spraying against compressed gas cooling liquid, in the gas temperature control method in the compressor, front of the impeller of the compressor and the next The amount of steam in the compression target gas of the cooling liquid is measured by a steam amount sensor provided in a return flow path connecting between the stage impellers via a return corner, and based on the measurement result, the steam amount sensor The spray amount of the cooling liquid sprayed to the diffuser side provided in the downstream portion of the front stage impeller can be controlled so as not to be directly applied to the front stage impeller .
[0010]
The present invention in order to attain the above objects, the compressor adapted to control the temperature of the compressed gas by spraying against compressed gas cooling liquid front of the impeller of the compressor and the next A steam amount sensor provided in a return flow path connecting between the stage impellers via a return corner, and a downstream portion of the front stage impeller provided in the return corner and not directly contacting the steam amount sensor. a spray nozzle for spraying the cooling liquid to the diffuser side provided, spraying of the cooling liquid sprayed from the spray nozzle on the basis of the steam volume in the compressed gas of the cooling liquid as measured by the amount of steam sensor And a control means for controlling the amount.
[0011]
In order to achieve the above object, the present invention provides a compressor that controls the temperature of the compression target gas by spraying a cooling liquid onto the compression target gas. A steam amount sensor provided in a return flow path connecting between the stage impellers via a return corner, and a downstream portion of the front stage impeller provided in the return corner and not directly contacting the steam amount sensor. A spray nozzle for spraying the cooling liquid to the diffuser side provided in the liquid, a liquid amount sensor for measuring the amount of the cooling liquid accumulated in the return flow path, and the compression on the upstream side and the downstream side of the spray nozzle A temperature sensor that measures the temperature difference of the target gas, and the amount of vapor in the compression target gas of the cooling liquid measured by the vapor amount sensor and the cooling accumulated in the return channel measured by the liquid amount sensor That the liquid volume and the temperature sensor of the body and a control means for controlling the necessity of spraying amount and the spray of the cooling liquid sprayed from the spray nozzle on the basis of the temperature difference between the compressed gas measured Features.
[0013]
According to the gas temperature control method and the compressor of the present invention, the vaporization state of the cooling liquid is directly detected by the vapor amount sensor in the return channel, and the spray amount of the cooling liquid is controlled based on this. Therefore, it is possible to substantially eliminate the occurrence of incomplete vaporization of the cooling liquid even under actual operating conditions, and effectively avoid the occurrence of various problems as described above due to incomplete vaporization of the cooling liquid. be able to.
[0014]
Further, according to the compressor of the present invention, the amount of the cooling liquid accumulated in the return flow path can be directly detected by the liquid amount sensor, so even if the drain is accumulated excessively, this state If necessary, it is possible to quickly take measures such as removing excess drain by temporarily shutting down the compressor operation, effectively avoiding performance degradation due to excessive storage of drain. be able to.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 and a partially enlarged view of FIG. 2 show a main part of a compressor according to an embodiment of the present invention. As shown in FIG. 1, the compressor according to the present embodiment is a single-shaft multi-stage centrifugal compressor, and a plurality of compression stages are formed in the axial direction on the rotary shaft 2 supported by the compressor casing 1. The number of impellers 3 (3a to 3d) (four in the example in the figure) is fixedly provided. The tip of each impeller 3 faces the return flow path 4 (4a to 4d) that is a flow path of the compression target gas. The return flow path 4 is a diffuser 5 that is a downstream portion of the impeller 3, a return corner 6 that is a downstream portion of the diffuser 5, and a downstream portion of the return corner 6, and rectifies the gas flow into an optimal flow. It consists of a return vane 7 that flows into the next stage impeller, and its airtightness can be maintained by a stage labyrinth 8 and an impeller eye labyrinth 9.
[0016]
The compression target gas that has flowed in through the suction pipe 11 is pressurized by the rotation of the impeller 3a at the front stage and discharged from there. The compression target gas discharged from the impeller 3a flows into the diffuser 5, reaches the return vane 7 through the return corner 6, and then flows into the next stage impeller 3b. The same is repeated after the impeller 3b, and each time the velocity energy of the compression target gas is changed to pressure energy due to the change in the gas flow in the return flow path 4 on the stationary side with respect to the dynamic impeller 3. It is compressed by being changed.
[0017]
In this process, the temperature of the compression target gas rises, but the cooling target gas is sprayed to cool the compression target gas so that it does not exceed a certain level. For this purpose, a temperature control system is provided for cooling the compression target gas with a cooling liquid that can evaporate in a normal temperature state in the compression target gas, such as water.
[0018]
As shown in FIGS. 1 and 2, the temperature control system controls the spray nozzle 12 that sprays the cooling liquid onto the compression target gas in the return flow path 4 and the supply amount of the cooling liquid to the spray nozzle 12. The valve 13, the flow rate controller 14 that controls the control valve 13, the cooling liquid supply tank 15, and the compression in the return flow path 4 downstream from the spray position of the cooling liquid by the spray nozzle 12 and before reaching the next impeller 3. A temperature sensor 16 that detects the temperature of the target gas, and a vapor amount of the cooling liquid in the compression target gas in the return flow path 4 downstream from the spray position of the cooling liquid by the spray nozzle 12 and before reaching the impeller 3 at the next stage. The amount of the compression target gas flowing in from the suction pipe 11 and the liquid amount sensor 18 for detecting the amount of drain accumulated in the bottom of the return flow path 4. Comprising gas weight meter 19 for measuring the amount.
[0019]
Commercially available sensors can be used for any of the above-mentioned sensors. For example, as for the vapor amount sensor 17, if water is used as a cooling liquid, a probe type using a polymer film moisture sensitive element is used. It is preferable to use a sensor that can convert humidity of 10 to 90% ph into an electrical signal and output it under various gas atmospheres. The relationship between the vapor amount sensor 17 and the spray nozzle 12 is preferably such that the sprayed cooling liquid is not directly applied to the vapor amount sensor 17, and for that purpose, on the diffuser 5 side above the return corner 6. It is preferable to provide the spray nozzle 12 so that the cooling liquid is sprayed at a slightly approached position.
[0020]
In such a temperature control system, the temperature information about the compression target gas obtained by the temperature sensor 16, the vapor amount information of the cooling liquid in the compression target gas obtained by the vapor amount sensor 17, and the liquid amount sensor 18 are obtained. Drain amount information in the return flow path 4 and weight flow information of the compression target gas obtained by the gas weight meter 19 are provided to the flow controller 14. The flow rate controller 14 obtains the necessary spray amount of the cooling liquid and the necessity of spraying based on these pieces of information, and thereby controls the control valve 13.
[0021]
Details of this control will be described below with reference to a flowchart shown in FIG. 3 as an example. First, the liquid amount sensor 18 measures the amount of drain accumulated at the bottom of the return corner 6 in the return flow path 4, and the temperature sensor 16 measures the temperature of the compression target gas. Next, it is determined whether or not the drain amount L measured by the liquid amount sensor 18 exceeds a predetermined amount (for example, 10 @ -5 m @ 3). At the same time, whether or not the temperature difference ΔT between the temperature of the compression target gas measured by the temperature sensor 16 and the temperature of the compression target gas upstream of the spray nozzle 12 is a predetermined value or more (for example, 10 ° C. or more). Alternatively, it is determined whether or not the temperature of the compression target gas measured by the temperature sensor 16 is equal to or higher than a predetermined temperature. In the former case, information from a temperature sensor provided separately from the temperature sensor 16 in order to detect the temperature of the compression target gas upstream of the spray nozzle 12 is also used.
[0022]
If the drain amount is excessive, spraying of the cooling liquid is not performed (in the case of initial start), or if it has already been performed, it is stopped. In this case, it is desirable to perform drainage or the like by stopping the operation of the compressor as necessary. Even if the drain amount is not excessive, if the temperature difference ΔT is greater than or equal to a predetermined value (or if the temperature of the gas to be compressed is lower than or equal to the predetermined temperature), that is, the gas to be compressed has a danger such as generation of a polymer. If the temperature does not reach the temperature, the spraying of the cooling liquid is not performed, or if it has already been performed, it is stopped.
[0023]
On the other hand, when the drain amount is not excessive and the temperature difference ΔT is not more than a predetermined value (or when the temperature of the compression target gas is not less than the predetermined value), the cooling liquid is sprayed at the A level. At this A level, the cooling liquid is usually sprayed in an amount that is, for example, 3 wt% of the weight flow rate of the compression target gas taken into the compressor.
[0024]
While the operation is continued in this state, the vapor amount sensor 17 measures the vapor amount of the cooling liquid in the compression target gas, and determines whether or not the result is a predetermined amount or less (for example, 85% or less). If the vapor amount is less than or equal to the predetermined amount, spraying of the cooling liquid at the A level is continued as it is. On the other hand, if the vapor amount is equal to or greater than a predetermined amount, the possibility of incomplete vaporization of the cooling liquid increases, so the cooling liquid spray amount at a level reduced from the cooling liquid spray amount at the A level. (For example, 90% of A level or less)
[0025]
【The invention's effect】
According to the present invention, with respect to a compressor configured to control the temperature of the compression target gas, the cooling liquid sprayed for cooling the compression target gas is always completely vaporized regardless of the operating state of the compressor. Therefore, various problems associated with incomplete vaporization of the cooling liquid can be effectively avoided.
[Brief description of the drawings]
FIG. 1 is a block diagram of a main part of a compressor according to the present invention.
FIG. 2 is an enlarged view of a part of FIG.
FIG. 3 is a flowchart relating to temperature control in the compressor of FIG. 1;
[Explanation of symbols]
4 Return flow path 14 Flow rate controller (control means)
17 Steam sensor 18 Liquid sensor

Claims (3)

In a gas temperature control method for a compressor that controls the temperature of the compression target gas by spraying a cooling liquid onto the compression target gas , a return corner is provided between the front impeller and the next impeller of the compressor. The amount of steam in the compression target gas of the cooling liquid is measured by a steam amount sensor provided in the return flow path connected to the downstream side of the preceding impeller so as not to be directly applied to the steam amount sensor based on the measurement result. A gas temperature control method characterized in that a spray amount of the cooling liquid sprayed to a diffuser side provided in a section can be controlled. In the compressor that controls the temperature of the compression target gas by spraying the cooling liquid onto the compression target gas , a return corner is provided between the front impeller and the next impeller of the compressor. A steam amount sensor provided in a return flow path to be connected , and the cooling liquid is sprayed to a diffuser side provided in a downstream portion of the front stage impeller so as not to be directly applied to the steam amount sensor. And a control means for controlling the spray amount of the cooling liquid sprayed from the spray nozzle based on the steam amount in the compression target gas of the cooling liquid measured by the steam amount sensor. Compressor characterized by. In the compressor that controls the temperature of the compression target gas by spraying the cooling liquid onto the compression target gas, a return corner is provided between the front impeller and the next impeller of the compressor. A steam amount sensor provided in a return flow path to be connected, and the cooling liquid is sprayed to a diffuser side provided in a downstream portion of the front stage impeller so as not to be directly applied to the steam amount sensor. A spray nozzle, a liquid amount sensor for measuring the amount of cooling liquid accumulated in the return flow path, a temperature sensor for measuring a temperature difference of the compression target gas upstream and downstream of the spray nozzle, The amount of vapor in the compression target gas of the cooling liquid measured by the vapor amount sensor, the amount of cooling liquid accumulated in the return flow path measured by the liquid amount sensor, and the temperature sensor measured. Compressor, characterized by comprising a control means for controlling the necessity of spraying amount and the spray of the cooling liquid sprayed from the spray nozzle on the basis of the temperature difference between the serial compressed gas.

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