Flow adjusting method for variable inlet pressure reciprocating compressor

Abstract

According to the flow adjusting method of the variable-inlet-pressure reciprocating compressor, the use sequence of all stages of air cylinders is reasonably formulated according to the change period of the inlet pressure of the compressor, and the purpose of precise flow adjustment can be achieved in combination with the backflow operation of the adjusting valve; the energy-saving effect is obvious through the method that all stages of cylinders are put into use step by step; the working characteristics of the compressor unloader are fully and reasonably utilized, and compared with a traditional scheme that single backflow adjustment is conducted or multiple compressors with different pressure intervals are arranged, the operation procedure is simple, and project investment is saved.

Description

Technical Field

[0001] The invention relates to the technical field of compressor flow regulation, and in particular to a flow regulation method for a variable inlet pressure reciprocating compressor. Background Art

[0002] Photovoltaic power generation, water electrolysis hydrogen production, hydrogen storage and transportation are emerging areas of comprehensive utilization of hydrogen energy. In the past two years, a large number of such projects have been planned and constructed. Among them, in the hydrogen transportation link, it is often necessary to set up a hydrogen compressor to pressurize the hydrogen and send it to downstream users. In this type of application scenario, there are conditions of hydrogen production, storage, and transportation during the day, and small amounts of hydrogen production (purchased valley electricity) and transportation at night. The compressor is an important equipment for hydrogen transportation, and its inlet pressure changes periodically with the internal pressure of the spherical tank.

[0003] The periodic change of the inlet pressure of the reciprocating compressor leads to the change of the compressor output flow (standard state). At the same time, the compressor is required to output a stable flow and pressure, which brings the problem of flow regulation. According to the conventional reciprocating compressor reflux regulation method, it is difficult for the unit to adapt to such a wide range of pressure changes. If only reflux regulation is relied on, it will also cause energy waste, and the selection of reflux regulating valve is difficult. Developing a new flow regulation method is of great significance for energy saving and smooth operation of the compressor. Summary of the invention

[0004] The purpose of the present invention is to provide a flow regulation method for a variable inlet pressure reciprocating compressor to solve the flow regulation problem when the inlet pressure of the reciprocating compressor changes. The present invention is suitable for flow regulation of a reciprocating compressor with more than two stages of compression.

[0005] The present invention comprises the following steps:

[0006] 1) For reciprocating compressors with more than two stages, each cylinder is equipped with an unloader, which acts directly on the gas valve; a return line is set at the outlet of each cylinder, and a reflux regulating valve is set on the return line;

[0007] 2) According to the inlet pressure of each stage of the compressor, the pressure value of each stage of the compressor cylinder is calculated, so as to formulate the action control logic of the unloader, and at the same time formulate the opening control logic of each stage of the return flow regulating valve, and the above two control logics are hierarchically controlled and written into the unit control system;

[0008] 3) When the compressor inlet pressure changes from low pressure to high pressure, the compressor inlet pressure is used as the control reference point, and the full unloading and partial unloading operations of the compressor unloaders at all levels are controlled by the control program, so that the compressor gradually switches from the multi-stage compression state of full cylinder compression to the single-stage compression state of only high-pressure cylinder compression, and the outlet reflux regulating valves of each level are actuated according to their corresponding control pressures, and finally the compressor outputs the required gas volume;

[0009] 4) When the compressor inlet pressure changes from high pressure to low pressure, the compressor inlet pressure is used as the control reference point, and the full unloading and partial unloading operations of the compressor unloaders at each stage are controlled by the control program, so that the compressor gradually switches from the one-stage compression state in which only the high-pressure stage cylinder is compressed to the multi-stage compression state in which all cylinders are compressed. The outlet reflux regulating valves at each stage are actuated according to their corresponding control pressures, and finally the compressor outputs the required gas volume.

[0010] Preferably, the unloader is a pneumatic unloader, which adopts a wind-loaded and windless unloading type or a wind-loaded and windless loading type.

[0011] Preferably, the reflux regulating valve is a pneumatic regulating valve, and the regulating signal comes from the next-level pressure signal.

[0012] Preferably, each stage of the cylinder is provided with an air inlet buffer tank and an air outlet buffer tank.

[0013] Preferably, the gas discharged from each stage of the gas outlet buffer tank is sent to a corresponding cooler for cooling, and then sent to the next stage or refluxed.

[0014] The present invention formulates the logic of gradually putting the cylinders of each level into use according to the inlet and outlet pressure values ​​of the cylinders of each level when operating at full load, taking the compressor inlet pressure as a reference, and formulates the logic of gradually putting the cylinders of each level into use (putting the cylinder of level n into use → putting the cylinder of level n-1 into use → ... → putting the cylinder of level 2 into use → putting the cylinder of level 1 into use, or reverse), and at the same time coordinates the action of the regulating valve of each level of outlet, thereby realizing flow regulation. The putting of the cylinder of level n into use means that the unloader of the cylinder of level n is in a normal operating state. At this time, the other cylinders are not put into use, the unloader is in an unloading state, the cylinder is equivalent to a gas pipeline, and the cylinder of this level does not do work.

[0015] The present invention has the following beneficial effects:

[0016] (1) The present invention provides a flow rate regulation method for a variable inlet pressure reciprocating compressor, which achieves significant energy saving effect by gradually putting cylinders of each level into use.

[0017] (2) The present invention provides a flow regulation method for a variable inlet pressure reciprocating compressor. According to the change cycle of the compressor inlet pressure, a reasonable order of commissioning of each stage of cylinders is formulated, and combined with the reflux operation of the regulating valve, the purpose of precise flow regulation can be achieved.

[0018] (3) The flow regulation method of a variable inlet pressure reciprocating compressor of the present invention fully and reasonably utilizes the working characteristics of the compressor unloader. Compared with the traditional single reflux regulation or the scheme of setting multiple compressors in different pressure ranges, the operation procedure is simple and the project investment is saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1is a flow chart of a flow rate regulation method when a four-row three-stage compressor is used in the present invention;

[0020] In the figure: 1. primary air intake buffer tank; 2. secondary air intake buffer tank; 3. tertiary air intake buffer tank; 4. first unloader; 5. second unloader; 6. third unloader; 7. fourth unloader; 8. fifth unloader; 9. sixth unloader; 10. seventh unloader; 11. eighth unloader; 12. primary cylinder; 13. secondary cylinder; 14. tertiary cylinder; 15. primary exhaust buffer tank; 16. secondary exhaust buffer tank; 17. tertiary exhaust buffer tank; 18. primary cooler; 19. secondary cooler; 20. tertiary cooler; 21. primary reflux regulating valve; 22. secondary reflux regulating valve; 23. tertiary reflux regulating valve; 24. air inlet; 25. instrument air; 26. air outlet. DETAILED DESCRIPTION

[0021] Taking a photovoltaic hydrogen production project as an example, during the daytime working condition (7:00 to 17:00), the hydrogen pressure produced by photovoltaic power generation and water electrolysis is about 1.45MPa (G), which enters the spherical tank for storage. Ten spherical tanks are set up to meet the needs of continuous hydrogen supply during nighttime working conditions. The compressor extracts hydrogen from the spherical tank, boosts the pressure and sends it to downstream users. With the commissioning of the electrolyzer, hydrogen is continuously produced, and the tank pressure (compressor inlet pressure) rises from 0.3MPa (G) to 1.45MPa (G) and maintains it. The filling of the spherical tank and the downstream hydrogen supply are carried out simultaneously; during the nighttime working condition (17:00 to 7:00 the next day), photovoltaic power generation and hydrogen production stop, and the hydrogen stored in the spherical tank (produced during the day) is extracted by the compressor. As the tank capacity decreases, the compressor inlet pressure continues to drop from 1.45Mpa (G) to 0.3Mpa (G), and the above process changes once a day. The compressor outlet pressure is 3.2Mpa (G), and the downstream users are refinery hydrogenation units.

[0022] In the above working conditions, the hydrogen produced by water electrolysis is required to be stably supplied to the downstream device for 8400 hours a year. According to the hydrogen supply volume, three compressors are set up, with a single compressor output flow of 14000m 3 n / h, inlet pressure 0.3~1.45Mpa(G), outlet pressure 3.2Mpa(G), using reciprocating compressor, based on the maximum pressure ratio calculation, using three-stage four-row compression.

[0023] like Figure 1 As shown, for the above units, in order to adapt to the working conditions of variable inlet pressure, the following measures are taken:

[0024] The compressor is provided with four cylinders, including two primary cylinders 12, one secondary cylinder 13 and one tertiary cylinder 14; the primary air intake buffer tank 1, the primary cylinder 12, the primary exhaust buffer tank 15, the primary cooler 18, the secondary air intake buffer tank 2, the secondary cylinder 13, the secondary exhaust buffer tank 16, the secondary cooler 19, the tertiary air intake buffer tank 3, the tertiary cylinder 14 and the tertiary cooler 20 are connected in sequence; the two primary cylinders 12 are provided with the first unloader 4, the second unloader 5, the third unloader 6 and the fourth unloader 7; the secondary cylinder 13 is provided with the fifth unloader 8 and the sixth unloader 9; the tertiary cylinder 14 is provided with the seventh unloader 10 and the eighth unloader 11; an instrument air 25 pipeline is provided, The unloader acts directly on the air valve and adopts the type of air loading and wind-free unloading; a return line is set at the outlet of each stage of the cooler, and a reflux regulating valve is set on the return line for reflux regulation. The regulating valve adopts a pneumatic regulating valve, and the regulation signal comes from as follows: the first-level reflux regulating valve 21 is controlled by the pressure of the second-level air intake buffer tank 2, and refluxes to the inlet pipeline of the first-level air intake buffer tank 1; the second-level reflux regulating valve 22 is controlled by the pressure of the third-level air intake buffer tank 3, and refluxes to the inlet pipeline of the second-level air intake buffer tank 2; the third-level reflux regulating valve 23 is controlled by the pressure of the third-level exhaust buffer tank 17, and refluxes to the inlet pipeline of the third-level air intake buffer tank 3; the air inlet 24 is connected to the first-level air intake buffer tank 1, and the air outlet 26 is connected to the third-level cooler 20.

[0025] Through calculation, the hierarchical control logic of the cylinders at each level and the opening of the regulating valves is formulated. The detailed plan is as follows:

[0026] During daytime operation, when the compressor inlet pressure changes from 0.3Mpa(G) to 1.45Mpa(G), the compressor gradually switches from three-stage compression (the first-stage cylinder, the second-stage cylinder, and the third-stage cylinder are all in use) to two-stage compression (the second-stage cylinder and the third-stage cylinder are in use) and one-stage compression (the third-stage cylinder is in use). The specific action process is as follows. The adjustment target is to ensure that the compressor can deliver gas stably at the rated gas volume:

[0027]

[0028]

[0029] During nighttime operation, when the compressor inlet pressure changes from 1.45Mpa(G) to 0.3Mpa(G), the compressor gradually switches from one-stage compression (three-stage cylinders in use) to two-stage compression (second and third-stage cylinders in use) and three-stage compression (first, second and third-stage cylinders are all in use). The specific action process is the reverse process of daytime operation.

[0030] By repeating the above process, the flow rate of the compressor can be adjusted, so that the downstream users can smoothly transmit gas, which is energy-saving and efficient (energy saving is about 40%).

Claims

1. A flow regulation method for a variable inlet pressure reciprocating compressor, characterized in that The following steps are involved: 1) For reciprocating compressors with more than two stages, each cylinder is equipped with an unloader, which acts directly on the gas valve; a return line is set at the outlet of each cylinder, and a reflux regulating valve is set on the return line; 2) According to the inlet pressure of each stage of the compressor, the pressure value of each stage of the compressor cylinder is calculated, so as to formulate the action control logic of the unloader, and at the same time formulate the opening control logic of each stage of the return flow regulating valve, and the above two control logics are hierarchically controlled and written into the unit control system; 3) When the compressor inlet pressure changes from low pressure to high pressure, the compressor inlet pressure is used as the control reference point, and the full unloading and partial unloading operations of the compressor unloaders at all levels are controlled by the control program, so that the compressor gradually switches from the multi-stage compression state of full cylinder compression to the single-stage compression state of only high-pressure cylinder compression, and the outlet reflux regulating valves of each level are actuated according to their corresponding control pressures, and finally the compressor outputs the required gas volume; 4) When the compressor inlet pressure changes from high pressure to low pressure, the compressor inlet pressure is used as the control reference point, and the full unloading and partial unloading operations of the compressor unloaders at each stage are controlled by the control program, so that the compressor gradually switches from the one-stage compression state in which only the high-pressure stage cylinder is compressed to the multi-stage compression state in which all cylinders are compressed. The outlet reflux regulating valves at each stage are actuated according to their corresponding control pressures, and finally the compressor outputs the required gas volume.

2. The flow rate regulation method of a variable inlet pressure reciprocating compressor according to claim 1, characterized in that: The unloader is a pneumatic unloader; it adopts a wind-loaded, windless unloading type or a wind-unloaded, windless loading type.

3. The flow rate regulation method of a variable inlet pressure reciprocating compressor according to claim 1, characterized in that: The reflux regulating valve adopts a pneumatic regulating valve, and the regulating signal comes from the inlet pressure signal of the next level.

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