Chloromethane screw compressor sealing system and sealing process thereof

Abstract

The invention relates to a sealing technology of a screw compressor, in particular to a sealing system of a chloromethane screw compressor, which not only can meet the variable speed requirement of the screw compressor, but also can be suitable for the working condition that chloromethane gas contains a few impurities, and comprises a female rotor and a male rotor which are arranged in a compressor shell, the two ends of the female rotor and the two ends of the male rotor are connected with bearing mechanisms respectively, and the sealing structure is characterized in that the two sides of the female rotor and the two sides of the male rotor are each provided with a carbon ring seal and a double-end-face mechanical seal, and meanwhile the invention further provides a corresponding sealing technology.

Description

Technical Field

[0001] The invention relates to a sealing technology for a screw compressor, in particular to a sealing system for a chloromethane screw compressor and a sealing process thereof. Background Art

[0002] Methyl chloride is an important methylating agent in organic synthesis in the chemical industry. Its process requires compressing methyl chloride into high-pressure gas. Due to the flammable and explosive properties of methyl chloride and the prohibition of oil and water, reciprocating piston compressors were generally used to compress methyl chloride. In recent years, in order to reduce costs and increase efficiency, dry gas sealed screw compressors have begun to be used to compress methyl chloride. However, dry gas seals are generally used for constant speed screw compressor seals and are not suitable for use on variable speed screw compressors. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a sealing system for a chloromethane screw compressor, which can not only meet the variable speed requirements of the screw compressor, but also be applicable to the working condition where the chloromethane gas contains a small amount of impurities. At the same time, the present invention also provides a corresponding sealing process.

[0004] The technical solution is as follows: a sealing system for a chloromethane screw compressor, comprising a female rotor and a male rotor installed in a compressor housing, wherein both ends of the female rotor and the male rotor are respectively connected to bearing mechanisms, and is characterized in that both sides of the female rotor and the male rotor are respectively provided with carbon ring seals and double-end mechanical seals.

[0005] It is further characterized in that the carbon ring seal comprises an inlet end carbon ring seal and an exhaust end carbon ring seal, the inlet end carbon ring seal and the exhaust end carbon ring seal are respectively connected to a first sealed gas pipeline and the second sealed gas pipeline, the first sealed gas pipeline is provided with a first regulating valve and a first pressure gauge, the exhaust end carbon ring seal is also connected to a compressor inlet pipe through a balancing pipe, the balancing pipe is provided with a second pressure gauge, the second sealed gas pipeline is provided with a second regulating valve, and the balancing pipe and the second sealed gas pipeline are both connected to a differential pressure transmitter; The double-end mechanical seal includes an intake end double-end mechanical seal and an exhaust end double-end mechanical seal, the intake end double-end mechanical seal includes an intake end female rotor mechanical seal and an intake end male rotor mechanical seal, the exhaust end double-end mechanical seal includes an exhaust end female rotor mechanical seal and an exhaust end male rotor mechanical seal, the intake end female rotor mechanical seal, the intake end male rotor mechanical seal, the exhaust end female rotor mechanical seal, and the exhaust end male rotor mechanical seal are all connected to the oil inlet main pipe through an oil supply pipe, a stop valve, an orifice plate and a pressure gauge are provided on the oil supply pipe, and a third pressure gauge and a self-operated differential pressure regulating valve are provided on the oil return pipe connected to the exhaust end double-end mechanical seal.

[0006] A sealing process for a sealing system of a chloromethane screw compressor, characterized in that sealing gas enters the carbon ring seal at the inlet end and the carbon ring seal at the exhaust end through a first sealing gas pipeline and a second sealing gas pipeline respectively, a first regulating valve regulates the sealing gas pressure so that the sealing gas pressure at the inlet end is higher than the inlet pressure of the process gas fed into the compressor, a differential pressure transmitter provides a differential pressure signal to the second regulating valve, and the second regulating valve regulates the sealing gas pressure so that the sealing gas pressure at the exhaust end is higher than the pressure of a balance pipe; sealing oil enters the double-end mechanical seal at the inlet end and the double-end mechanical seal at the exhaust end through an oil inlet pipeline, is collected to an oil return main pipe for discharge through an oil return pipe, the sealing oil pressure entering the double-end carbon ring seal at the inlet end is higher than the sealing gas pressure entering the carbon ring seal at the inlet end, and a self-acting differential pressure regulating valve on the oil return pipe connected to the double-end mechanical seal at the exhaust end regulates the sealing oil pressure of the double-end carbon ring seal at the exhaust end to be higher than the sealing gas pressure of the carbon ring seal at the exhaust end.

[0007] Its further feature is that the pressure point on the high-pressure side of the self-operated differential pressure regulating valve is the return oil pressure of the double-end mechanical seal at the exhaust end, and the pressure point on the low-pressure side is the sealing gas pressure of the carbon ring seal at the exhaust end.

[0008] After adopting the present invention, a carbon ring seal + a double-end mechanical seal is used to seal it in the cavity, and the sealing gas pressure and the sealing oil pressure are reasonably controlled to ensure the sealing performance, which can not only meet the variable speed requirements of the screw compressor, but also be suitable for the working condition where the methyl chloride gas contains a small amount of impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a front view of the interior of the compressor of the present invention; Figure 2 This is a top view of the interior of the compressor of the present invention; Figure 3 This is a process flow chart of carbon ring sealing; Figure 4 This is the process flow chart of double-end mechanical seal. DETAILED DESCRIPTION

[0010] See Figure 1 , Figure 2 As shown, a sealing system for a chloromethane screw compressor includes a female rotor 3 and a male rotor 7 installed in a compressor housing 1, the two ends of the female rotor 3 and the male rotor 7 are respectively connected to a bearing mechanism 5, the bearing mechanism 5 includes a bearing and a support thereof, both sides of the female rotor 3 and the male rotor 7 are respectively provided with a carbon ring seal and a double-end mechanical seal, the carbon ring seal includes an inlet end carbon ring seal 2 and an exhaust end carbon ring seal 4, the double-end mechanical seal includes an inlet end double-end mechanical seal 8 and an exhaust end double-end mechanical seal 6, and one end of the female rotor 3 and the male rotor 7 are connected to meshing synchronous gears 9.

[0011] See Figure 3As shown, the carbon ring seal 2 at the inlet end and the carbon ring seal 4 at the exhaust end are respectively connected to the first sealed gas pipeline 10 and the second sealed gas pipeline 11, the first sealed gas pipeline 10 and the second sealed gas pipeline 11 are connected to the sealed gas mother pipe 12, the mother pipe pressure gauge PG01, the pressure differential gauge PDG01 and the filter 13 are arranged on the sealed gas mother pipe 12, the first sealed gas pipeline 10 is provided with a first regulating valve PCV01 and a first pressure gauge PG02, the first regulating valve PCV01 is a self-operated pressure regulating valve, the carbon ring seal 4 at the exhaust end is also connected to the compressor intake pipe 15 through the balance pipe 14, the compressor intake pipe 15 introduces process gas into the compressor, the second pressure gauge PG03 is installed on the balance pipe 14, the second sealed gas pipeline 11 is provided with a second regulating valve PV01, the balance pipe 14 and the second sealed gas pipeline 11 are both connected to the pressure differential transmitter PDT01, and the pressure differential transmitter PDT01 feeds back the pressure differential signal to the second regulating valve PV01.

[0012] See Figure 4 As shown, the double mechanical seal at the inlet end includes a female rotor seal at the inlet end and a male rotor seal at the inlet end, and the double mechanical seal at the exhaust end includes a female rotor seal at the exhaust end and a male rotor seal at the exhaust end. The female rotor seal at the inlet end, the male rotor seal at the inlet end, the female rotor seal at the exhaust end, and the male rotor seal at the exhaust end are all connected to the oil inlet mother pipe 17 through the oil supply pipe 16. The pressure transmitter PT1 is arranged on the oil inlet mother pipe 17. The four-way oil supply pipe 16 is provided with a stop valve (J04, J03, J02, J01), an orifice plate (R04, R03, R02, R01) and a pressure gauge (PG05, PG04, PG03, PG02), adjusting the stop valve opening can change the oil supply pressure and limit the oil supply amount. The return oil pipe 18 connected to the double-end mechanical seal at the exhaust end is provided with a third pressure gauge PG01 and a self-operated differential pressure regulating valve PDCV01. The return oil pipe 18 connected to the double-end mechanical seal at the exhaust end and the return oil pipe 19 connected to the double-end mechanical seal at the intake end are combined to the return oil main pipe 20 for discharge. The return oil pipe 19 is also provided with a stop valve J05, an orifice plate R05, and a pressure gauge PG06. The return oil pipe 18 and the return oil pipe 19 are also provided with a thermometer TG1 and a thermometer TG2, respectively.

[0013] See Figure 3As shown, the carbon ring sealing process flow: the sealing gas is divided into two paths after passing through the filter 13, one path passes through the first regulating valve PCV01 and enters the carbon ring seal 2 at the intake end, and the other path passes through the second regulating valve PV01 and enters the carbon ring seal 4 at the exhaust end. For the carbon ring seal 2 at the intake end, since the temperature and pressure of the process gas at the compressor inlet are stable and low, it is not easy to produce polymers, so there is no debris in the gap between the carbon ring seal 2 at the intake end and the shaft, that is, the process gas pressure in this gap is a fixed value. After the sealing gas pressure is adjusted by the first regulating valve PCV01 (the sealing gas pressure at the intake end is higher than the process gas intake pressure), the pressure of the first pressure gauge PG02 is stable, which can ensure that the process gas cannot leak from the carbon ring seal 2 at the intake end. For the exhaust end carbon ring seal 4, the process gas is compressed by the compressor at high temperature and high pressure, which may cause polymers to be blocked in the gap between the exhaust end carbon ring seal 4 and the shaft, and then the pressure of the process gas in the exhaust end carbon ring seal 4 is variable (this pressure can be measured by the second pressure gauge PG03). The second regulating valve PV01 adjusts the sealing gas pressure of the exhaust end carbon ring seal 4 to always be higher than the pressure in the balance pipe 14 by 0.05MPa through the signal fed back by the differential pressure transmitter PDT01, thereby playing a sealing role. Among them, the sealing gas refers to high-pressure methyl chloride gas, and the process gas refers to methyl chloride gas.

[0014] See Figure 4 As shown in the figure, the process flow of double-end mechanical seal; the high-pressure sealing oil is divided into 4 oil supply pipes through the inlet, and enters the female rotor mechanical seal at the intake end, the male rotor mechanical seal at the intake end, the female rotor mechanical seal at the exhaust end, and the male rotor mechanical seal at the exhaust end respectively. The sealing oil passes through the double-end mechanical seal at the intake end and the double-end mechanical seal at the exhaust end and is then collected and discharged into the return oil pipe. For the double-end mechanical seal 8 at the intake end, since the sealing gas pressure of the carbon ring seal 2 at the intake end is fixed, its oil supply pressure only needs to be guaranteed to be higher than the sealing gas pressure, which is generally 0.1MPa higher. For the double-end mechanical seal 4 at the exhaust end, the sealing gas pressure of the carbon ring seal 4 at the exhaust end is variable, and the sealing oil pressure needs to be higher than the sealing gas pressure. Therefore, a self-operated pressure differential regulating valve PDCV01 is installed on the return oil pipe of the double-end mechanical seal 6 at the exhaust end to ensure that the pressure difference between the two pressure points is stable at 0.1MPa. The pressure point on the high-pressure side is the return oil pressure of the double-end mechanical seal 6 at the exhaust end, and the pressure point on the low-pressure side is the gas pressure of the carbon ring seal 4 at the exhaust end. A small amount of sealing oil may leak into the gap between the mechanical seal and the carbon ring seal, which can be opened after shutdown. Figure 3 The V01, V02, V03, and V04 hand valves of the medium carbon ring seal drain pipeline are used for draining. Among them, the sealing oil refers to the high-pressure lubricating oil.

Claims

1. A sealing system for a chloromethane screw compressor, comprising a female rotor and a male rotor installed in a compressor housing, wherein both ends of the female rotor and the male rotor are respectively connected to bearing mechanisms, wherein: Both sides of the female rotor and the male rotor are respectively provided with a carbon ring seal and a double-end mechanical seal; the carbon ring seal includes an inlet end carbon ring seal and an exhaust end carbon ring seal, the inlet end carbon ring seal and the exhaust end carbon ring seal are respectively connected to the first sealed air pipeline and the second sealed air pipeline, the first sealed air pipeline is provided with a first regulating valve and a first pressure gauge, the exhaust end carbon ring seal is also connected to the compressor intake pipe through a balancing pipe, the balancing pipe is installed with a second pressure gauge, the second sealed air pipeline is provided with a second regulating valve, the balancing pipe and the second sealed air pipeline are both connected to a differential pressure transmitter ; The double-end mechanical seal includes an inlet end double-end mechanical seal and an exhaust end double-end mechanical seal, the inlet end double-end mechanical seal includes an inlet end female rotor seal and an inlet end male rotor seal, the exhaust end double-end mechanical seal includes an exhaust end female rotor seal and an exhaust end male rotor seal, the inlet end female rotor seal, the inlet end male rotor seal, the exhaust end female rotor seal, and the exhaust end male rotor seal are all connected to the oil inlet main pipe through an oil supply pipe, a stop valve, an orifice plate and a pressure gauge are provided on the oil supply pipe, and a third pressure gauge and a self-operated pressure differential regulating valve are provided on the oil return pipe connected to the exhaust end double-end mechanical seal.

2. A sealing process for a sealing system of a chloromethane screw compressor, characterized in that: The sealing gas enters the carbon ring seal at the inlet end and the carbon ring seal at the exhaust end through the first sealing gas pipeline and the second sealing gas pipeline respectively. The first regulating valve adjusts the sealing gas pressure so that the sealing gas pressure at the inlet end is higher than the inlet pressure of the process gas sent to the compressor. The differential pressure transmitter provides a differential pressure signal to the second regulating valve. The second regulating valve adjusts the sealing gas pressure so that the sealing gas pressure at the exhaust end is higher than the balance pipe pressure. The sealing oil enters the double-end mechanical seal at the inlet end and the double-end mechanical seal at the exhaust end through the oil inlet pipeline, and is collected to the oil return main pipe for discharge through the return oil pipe. The sealing oil pressure entering the double-end carbon ring seal at the inlet end is higher than the sealing gas pressure entering the carbon ring seal at the inlet end. The self-operated differential pressure regulating valve on the return oil pipe connected to the double-end mechanical seal at the exhaust end adjusts the sealing oil pressure of the double-end carbon ring seal at the exhaust end to be higher than the sealing gas pressure of the carbon ring seal at the exhaust end.

3. The sealing process of a sealing system for a chloromethane screw compressor according to claim 2, characterized in that: The pressure point on the high-pressure side of the self-operated differential pressure regulating valve is the return oil pressure of the double-end mechanical seal at the exhaust end, and the pressure point on the low-pressure side is the sealing gas pressure of the carbon ring seal at the exhaust end.

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