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Technical upgrade of high-pressure and medium-pressure nitrogen system at Sino-China Chemical Gasification Plant / Author/Source: Sino-China Chemical Date: 2022-05-13 Clicks: 9 The nitrogen system at Sino-China Chemical serves as the \"lifeline\" and \"foundation\" for the operation of the entire methanol plant; a stable supply of nitrogen is essential to ensure the safety of the plant, acting in a role similar to that of a \"firefighter\". Under the condition of dual furnaces operating at high load, the extraction volume from the medium-pressure nitrogen pipeline network in the air separation unit is around 16,000 m3, which is significantly higher than the designed value of around 3,000 m3. This not only increases the cooling loss of the low-pressure plate heat exchangers, reduces the output of liquid oxygen production and raises energy consumption, but also prevents the medium-pressure nitrogen from reaching the desired pressure level. Driven by the company’s vigorous efforts in technological upgrades as part of its \"energy conservation and consumption reduction\" initiatives, the technical upgrade project to reduce nitrogen pressure from 8.0 MPa to 0.7 MPa in air separation units was developed. There is only one user of the 8.0 MPa nitrogen system; under normal operating conditions, the gasifier hardly uses any purified nitrogen at all. As a result, discharging nearly 1,000 m³ of nitrogen from the air separation unit into the atmosphere would constitute a serious waste of resources. To make better use of nitrogen at this pressure level, and after obtaining data support through various analyses, the gasification plant approved a project for technical upgrades to high-, medium-, and low-pressure nitrogen systems in September 2021. The project plans to add devices such as throttle valves to throttle high-pressure nitrogen and feed it into the medium-pressure nitrogen pipeline network after the nitrogen compressor. Since the project was launched, the gasification plant has closely monitored its progress, keeping track of the arrival of pipes and valves in a timely manner. To ensure that the openings made in the project pipelines would not affect the stable operation of the equipment, end connections were created at two of these pipelines during the overhaul in October 2021. Since May, valves and materials have arrived at the plant one after another. Taking advantage of the favorable construction conditions during the hot summer months, the gasification branch has stepped up its efforts to carry out the project construction. On May 8, with everything pre-prepared in advance, the high-reduction medium-pressure nitrogen pipeline was constructed in one go and passed the leak test at a pressure of 6.5 MPa. After the pressure testing was completed, in order to accelerate the recovery of the vented nitrogen, the branch factory organized technicians to carry out commissioning tests on the pipeline that same afternoon. The technicians conducted comprehensive testing to ensure the pipeline’s ability to function under various abnormal conditions, and they successfully completed the commissioning process around 7 p.m. After the implementation of this technical upgrade project, the amount of medium-pressure nitrogen extracted decreased from 15,600 m3 to around 14,400 m3, while the exhaust volume of the air compressors dropped by about 1,000 m3. With the current load remaining unchanged, the energy consumption of the air compressors was reduced, and the daily production of liquid nitrogen increased by approximately 2 tons. The gasification plant closely monitors data changes and continues to optimize system adjustments, striving to maximize the benefits of the technical renovation project.