Application Case of A Natural Gas Treatment Plant in Changqing Oilfield
User: Natural Gas Processing Plant in Changqing Oilfield
As the largest natural gas ethane recovery unit in China, a natural gas processing plant in Changqing Oilfield is a key project of CNPC to improve quality and efficiency. To achieve the supply of raw materials for the process of producing ethylene from ethane as soon as possible, the project not only adopts the international advanced "refrigerant refrigeration + expansion refrigeration + double gas overcooling + low temperature distillation" ethane recovery main body technology, but also adopts advanced technology in engineering design and construction.CNPC fully leverages its overall advantage and uses, the international advanced SP3D three-dimensional collaborative design platform, "and full life cycledigital factory" mode, to achieve digital and intelligent management of the entire process of design, procurement, construction, operation and maintenance.
After the completion of the natural gas treatment plant, it can realize annual processing 20 billion cubic meters of natural gas, annual production of 1.05 million tons of ethane, 450,000 tons and stable light hydrocarbon, equivalent to the output value of a domestic medium-sized oil field, it also marks that China's natural gas development has not only completed the transformation from scale-based development to profit-based development, but also realized the high-quality closed-loop development of CNPC's industrial chain in Shaanxi.
The circulating water closed cooling tower system of the natural gas processing plant uses air cooling + water cooling to cool the circulating water. Due to the cooling water of the circulating water closed cooling tower uses groundwater directly as supplementary water, the system has an obvious tendency to scale after concentration, and it is easy to deposit and adhere to the cooling tower filler, spray device, and heat exchange tubes, affecting the heat exchange effect, resulting in the internal circulation temperature difference decreases and the expected heat exchange effect cannot be achieved. Due to the adhesion and deposition of scale and biological slime, it is easy to cause corrosion under the scale. In severe cases, it may cause leakage points in the heat exchange tube bundle of the cooling water tower. After on-site investigation, it was found that scaling had occurred in the external circulation spray water system.
Monitoring parameter: conductivity
The conductivity of spray water replenishment is 2290μs/cm, and the total salinity is 1705.08mg/L, which is greater than the designed 1000mg/L. When the spray water is constantly evaporating and the water is constantly replenished, the conductivity increases from 2290 μs/cm to 10140 μs/cm after 1 hour of operation, the conductivity increased nearly 5 times, the total salinity increased from 1705.08mg/L to 3880.07mg/L, and the concentration multiple reached 2.3 times.If the spray water is not replaced, the conductivity can reach 34900 μs/cm after 48 hours of operation, and the concentration factor reaches about 30 times.Therefore, when the spray water quality is not up to standard and water quality pretreatment is not carried out, the spray water forms severe scaling and crystallized salts in the circulating water heat exchange tube bundle, spray water main pipe, closed cooling tower filler and spray tank, causing the heat exchange effect of circulating water spray is reduced, and the filler is blocked, resulting in insufficient air inlet volume of the air-cooled fan and reduced air-cooling effect.
To solve the above problems, the company installed an inductive conductivity online measuring instrument in its cooling tower to monitor the conductivity of the spray water in real time when the spray water quality does not meet the standard and water quality pretreatment is not carried out, the alarm is activated to provide an accurate basis for subsequent water treatment and spray water replenishment.
The inductive conductivity electrode produced by Shanghai Boqu Instrument Co., Ltd.,it has a large measurement range and anti-fouling characteristics, which solves the problem of sensor fouling caused by the high salinity of water samples on site, reduces the workload of on-site operation of maintenance personnel, and its ultra-large range of 0-2000ms/cm covers the measurement requirements required on site.