Analysis and study on operating conditions of water ring vacuum pump in gas drainage station
Low concentration gas generator direct access drainage station for gas drainage station water ring vacuum pump to run when a certain impact, based on the importance of the safe operation of the gas extraction stations, the article to the gas station after the completion of water ring vacuum pump operation condition are analyzed in targeted, and puts forward the measures to improve the system pressure, the results showed that as long as the technology of water ring vacuum pump take reasonable measures, for the construction of the low concentration gas power stations will not bring safe hidden trouble of gas extraction station operation.
High gas mines or gas outburst mines have permanent surface gas drainage stations. Due to the limitations of mine drainage conditions, most surface gas drainage stations have low gas concentration. The main comprehensive utilization method is to use low-concentration gas generator sets to generate electricity. Low concentration gas conveying system generally adopts the water mist and low concentration gas mixture transportation mode, usually before the gas into the generator set to simple processing, gas quality is poorer, more water and dust into the gas generator set, lead to a series of problems, mainly for power generation efficiency decline, reduced output and equipment availability greatly reduced, operation maintenance cost, etc. Therefore, gas pretreatment system should be set up for low concentration gas generator set to improve the operation economy, stability and reliability. The low-concentration gas pretreatment system has a large resistance. At the same time, due to many technical problems in low-concentration gas pressure, the majority of low-concentration gas conveying power completely relies on the exhaust backpressure of the pumping station. The access of the gas conveying system will affect the vacuum operation of the water ring of the pumping station to a certain extent. In view of the above situation, this paper analyzes the operating conditions of water ring vacuum pump after the completion of gas power station, and puts forward measures to improve the pressure of the system.
1. Calculation of resistance of low concentration gas transportation
There are many low-concentration gas generator sets, including water blocking flame arrester, screen filter, dry flame arrester for gas, flow measurement device, atomization device, low-concentration gas pretreatment device, various valves, etc.
1) working condition 1: under the design flow, the pre-treatment device is not considered for the low-concentration gas, the system pressure loss is 7540Pa, the water ring vacuum exhaust pressure is 99.54kpa, the motor shaft power is 374kW, and the motor standby coefficient is 1.06, basically meeting the requirements. Therefore, when the gas conveying system is not equipped with a gas pretreatment device or the gas conveying distance is not far, the back pressure of the water ring vacuum pump will not increase after the system is directly connected, and the supporting motor can meet the requirements of the system, and the low-concentration gas generator set will not endanger the safe operation of the pumping station.
2) working condition 2: under the design flow, the gas conveying system considers the pretreatment device, the pressure loss of the system is 12040Pa, the vacuum exhaust pressure of the water ring is 104.04kpa, and the motor shaft power needs to be 413kW. The original motor cannot meet the operation needs of the pumping station, so technical measures should be taken. Therefore, when the low-concentration gas conveying system is well set up for gas pretreatment or long-distance conveying and there is no pressurization measure, the backpressure of the water ring vacuum pump increases greatly, and the supporting motor cannot meet the requirements of the system, and the pumping capacity of the pumping station will be affected after the system is directly connected.
3) working condition 3: when the actual flow is 90% of the designed flow, the exhaust pressure is 104.04kpa, the pump shaft power is 372kW, and the standby coefficient of the motor is 1.07, basically meeting the requirements. Therefore, when the system resistance is larger, the exhaust backpressure of the water ring vacuum pump is higher, but the pumping and discharging mixed flow is reduced, the matching motor can also meet the requirements.
2. Measures to improve system pressure
1) strengthen extraction management and reduce the leakage of vacuum system, which can improve the concentration of extraction gas, reduce the amount of extraction mixture, effectively reduce the power of water ring vacuum pump and improve the motor surplus coefficient. For example, the initial gas extraction concentration of the gas extraction station in the air shaft of xuandong coal mine of jizhong energy resources was 15%, the water ring vacuum pump output after the completion of the gas power station was slightly insufficient, and the gas extraction concentration was increased to 20% after the coal mine strengthened the gas extraction measures, which could completely meet the needs of the gas power station and ensure the safety of the coal mine.
2) when the above measures cannot meet the requirements, the motor power can be appropriately increased on the premise that the electrical system of the pumping station is basically unchanged. For example, the motor power of water-ring vacuum pump in the mudditch gas extraction station in pingshu coal mine of Yang coal group is 400kW. The low-concentration gas power station plans to adopt deep freezing dehydration technology, which has a large system resistance. The original motor power is insufficient. The modified gas extraction station can meet the needs of low concentration gas transportation.
3) if the above technical measures still fail to meet the requirements, an intermediate pump station can be set up after technical and economic comparison, and water ring vacuum pump or hydraulic jet pump can be used for pressurization to overcome the resistance of gas conveying system. Such as LuAn group and a margin of coal mine gas extraction stations when the design of water ring vacuum pump low back pressure, the gas drainage CaiLiang greatly, the original water ring vacuum pump can not meet the needs of the low concentration gas transportation, extraction transformation condition is poor, system adopts set in the middle water ring vacuum pump pressure, can meet the demand of the gas transmission, but covers and investment is larger, operation and management requirements.
4) vacuum psa purification technology can also be used for low-concentration gas to carry out long-distance transportation or gas pretreatment after the low-concentration gas concentration is increased. However, the low concentration gas vacuum psa purification scheme has higher investment and operation cost, so it is not suitable for low concentration gas power generation.
3, low concentration of gas generator design recommendations
1) the low-concentration gas power station should be close to the gas drainage station. The installation of pipe accessories, pipe layout and pipe material selection should be safe and reasonable to minimize the system resistance.
2) build a new low-concentration gas drainage station. When designing and selecting water ring vacuum pump, the selection range of back pressure can be appropriately increased according to comprehensive utilization conditions.
3) construction of low-concentration gas generator sets should earnestly implement the following three links: carefully collect detailed data of gas drainage station design, comprehensively understand the basic situation of each professional design, so as to ensure accurate data; Actual operation data of gas extraction station should be tested on site, including downhole extraction status, actual extraction amount, extraction concentration, motor power and other data. Data testing should be conducted in different time periods and compared with the original design. Understand the mine mining plan and subsequent gas extraction plan, and make a preliminary plan on the scale of gas conveying system.
To sum up, comprehensive analysis should be carried out on the above factors in the early stage of gas generator set construction, and reasonable rectification measures should be formulated according to the original design of gas generator set, actual operation status, later extraction plan and other factors, which is the key to ensure the safe production of low-concentration gas generator set, gas drainage station and coal mine.
4, the conclusion
1) low concentration gas generator set gas pretreatment device can improve the unit operation condition, improve the operation efficiency, stability, reliability, should actively promote, but the system resistance is bigger, can affect the safe operation of the gas extraction from standing water ring vacuum pump, and cause a certain hidden danger to coal mine safety production, the low concentration gas pretreatment technology in the field of gas power generation application promotion of a bottleneck, measures should be taken.
2) during the construction of low-concentration gas power generation, the gas power station, gas conveying system and gas drainage system shall be fully and carefully analyzed to confirm the influence degree of low-concentration gas generator set on water ring vacuum pump of gas drainage station, and then corresponding technical measures shall be taken to ensure the safe operation of water ring vacuum pump of gas drainage station.