Optimize the process equipment and operation status of the substation 1. The double valve of the sewage valve after the separation of the dust collector The original design of the sewage valve after the separators of the stations along the Jingxi gas pipeline is a valve sleeve type sewage valve, due to sewage discharge When the valve is opened and closed, the pressure difference between the valve and the front is large (generally about 2.7 MPa). The long-term operation will inevitably cause the drain valve to leak, and the flushing will intensify the leakage, which will not only cause gas loss, but also to the gas station. Bring security risks. To replace the drain valve, the separator must be deactivated and a leak will occur soon after the drain valve is replaced.

In order to completely solve the problem of leakage of the sewage valve, a sealing plug valve can be added before the original sewage valve. When starting the sewage operation, first open the front plug valve, then open the outer valve sleeve type drain valve; when stopping the drain operation, first close the valve sleeve type drain valve, then close the plug valve, so that the differential pressure of the plug valve is always Small, the impact of the valve is also very small, so that the natural gas mainly flushes the outer valve sleeve type drain valve, so that the plug valve is always protected. If the valve sleeve type drain valve is severely flushed, the front plug valve can be closed and replaced directly.

After the double valve modification of the sewage valve of the separator, the leakage amount of the sewage valve is greatly reduced, the safety hazard of the gas station is reduced, and the inspection operation of the sewage valve is more convenient. Through production practice, we believe that this solution is reasonable and feasible.

2. Location of the inbound temperature measurement point The inbound temperature detection devices of the original gas station of the Jingxi line are installed in front of the inbound ball valve. When the joint between the casing and the main line of the bimetal thermometer leaks, The main pipe section where the leak point is located needs to be deflated and stepped down before the inspection operation can be performed. In this way, not only the operation procedure is complicated, but also the maintenance takes a long time (only at least 2 hours is required for venting), and the venting amount is large, at least 8×104 m3 or more (the venting pipe section is calculated according to 25 km, and the pressure is 2.6 MPa), not only It causes energy waste and jeopardizes downstream gas safety.

In the gas production process, the natural gas temperature is almost unchanged before and after the inbound ball valve. In the construction process of the station, after the communication with the designer, the detection point of the inbound temperature is moved to the inbound ball valve.

Once there is a leak or other abnormal condition at the connection point between the bimetal thermometer sleeve and the gas pipeline, the inlet and outlet valves can be closed and the station can be emptied. After adjusting the position of the inbound temperature detection point, it not only reduces the amount of emptying (the venting of the station is generally several tens of cubic meters), but also shortens the inspection time and improves the safety of the gas transmission.

3. Increasing the pressure regulating valve heating device During the winter gas transmission process, especially in cold weather, the gas supply of the pressure regulating valve is often interrupted, which jeopardizes the safety of downstream gas.

The reason for this is that natural gas contains traces of water vapor (the natural gas water dew point in Jingbian gas field is generally -20 ° C, while the lowest temperature in the downstream area is -10 ° C). When the pressure of natural gas is reduced by 1 MPa, the gas temperature will drop by 3 to 6 °C. And the lower reaches of the Jingxi line

Pressure balance and compressor operation optimization 1. Improve pipeline gas transmission capacity In the process of long-distance natural gas transmission, how to make full use of pipeline gas transmission capacity to meet downstream users' gas demand is worthy of serious study.

The gas pipeline capacity calculation formula is: Qv=5033.11d8/3(p12-p2)/GTZ"L0.5[1](1) where: Qv is the pipeline passing capacity, m3/d; d is the inner diameter of the pipeline, Cm; p1 is the starting point pressure of the pipeline, MPa (absolute); p2 is the end point pressure of the pipeline, MPa (absolute); G is the relative density of natural gas (for air); T is the average absolute temperature of natural gas, K; Z is the compression coefficient of natural gas; For the length of the pipe, km.

It can be seen from equation (1) that increasing the starting pressure of the long-distance pipeline and reducing the end pressure, or both methods can improve the pipeline gas transmission capacity. The starting point pressure is generally determined by the outlet pressure of the upstream purification plant. If it is to be increased, it can only be pressurized by the compressor, but it is limited by the compressor capacity and the maximum pressure that the pipeline can withstand. Reducing the end pressure of the gas pipeline can also improve the gas transmission capacity, but it must be carried out under the premise of ensuring the downstream gas pressure, and the lower the downstream network pressure, the greater the gas transmission capacity of the pipeline, and the faster the gas flow rate. The more serious the pipe is washed. The design pressure of the Weihe River Qingguan Station at the end of the Jingxi Line is 2.75 MPa. At the peak of the gas supply in the winter of 2002, the pressure at the end of Xi'an Station has dropped to 0.66 MPa. MPa, the gas flow rate at the end of the pipeline is up to 26m / s, far exceeding the normal flow rate allowed by the pipeline, which becomes an unsafe factor affecting pipeline operation, affecting the service life of the pipeline, and therefore can only reduce the end pressure to a limited extent.

2. Fully utilizing the gas storage capacity of the pipeline When the temperature changes greatly, the sudden change of the gas consumption in the downstream will inevitably occur. However, due to the fact that there is no seasonal peaking facility at the current Jingxi line, in addition to relying on the adjustment capability of the upstream gas field, It is also necessary to make full use of the adjustment capacity of Jingxi Pipeline itself. Otherwise, the end pressure will be too low or too high. If the downstream pressure is too low, it will affect the downstream gas; if the downstream pressure is too high, the pipeline will overpressure and endanger the safety of the pipeline.

The gas transmission capacity of Jingxi Pipeline is designed according to the maximum demand at the peak of winter gas supply. During the low peak period of gas use, the pipeline runs below the design point, and the end pressure is generally maintained at about 2.5 MPa. In the winter when the peak of gas supply comes, the downstream gas consumption will increase sharply due to the temperature drop. At this time, it is necessary to increase the operating pressure of the entire pipeline, especially the pressure at the end of the pipeline (which can be maintained at about 3.3 MPa), and the storage capacity of the pipeline can be utilized. To alleviate the downstream pressure drop caused by the sudden increase in gas consumption, and increase the upstream intake air amount to maintain the balance of the inlet and outlet gas of the pipeline as much as possible.

At the end of the winter gas supply peak, the downstream gas consumption will suddenly drop. Even if the upstream air intake is required to be reduced, the downstream pressure will continue to rise. At this time, the pipeline operating pressure must be reduced. It is possible to reduce the end pressure to 1.8 MPa while appropriately reducing the upstream intake air so that the pipe pressure does not rise too high.

3. Optimize the operation of the compressor. Use the compressor to increase the delivery pressure of natural gas at the beginning of a certain pipe section, and reduce the end pressure of the pipe section to improve the conveying capacity of the pipe section. From the operation of a single compressor, the higher the inlet pressure, the lower the outlet pressure, the lighter the load of the compressor, the smaller the loss, the lower the energy consumption, and the longer the service life. For the gas pipe section between the two compressors, the outlet pressure of the upstream side compressor is equivalent to the starting point pressure of a certain pipe section, and the inlet pressure of the downstream side compressor is equivalent to the end pressure of the pipe section. The higher the compressor outlet pressure, the lower the inlet pressure, the greater the gas transmission capacity of the entire pipeline, but it will also increase the operating load of the single machine, which is not conducive to the normal operation of the equipment. When multiple compressors are operated in combination, if there is no external gas transmission volume, the rotation speed of each compressor should be adjusted appropriately so that the displacement of the compressor is equal and in the normal working area, so that the pressure of the entire gas pipeline is only Will be basically balanced.

In short, according to the operation status of the Jingxi natural gas pipeline, through the reasonable adjustment of the starting and ending pressures of the long-distance pipeline, optimize the compressor operation, give full play to the gas transmission capacity of the existing pipeline, improve the pipeline transportation efficiency, and increase the filtration through the station. In the gas supply branch, the flow regulating valve is added to control the downstream gas consumption, the double valve modification is performed on the dust collector drain valve, the electric heating device is added to the pressure regulating valve, and the noise of the gas supply branch road is reduced. It greatly improves the safety of gas supply at the station and ensures the normal use of gas by users in the downstream market.

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