Regular Article

Oiling low temperature separation process for dehydration and de-hydrocarbon of natural gas and practical application

¹ Key Laboratory of Gas Process Engineering, Chemistry and Chemical Engineering Institute, Southwest Petroleum University, Chengdu 610500, Sichuan Province, China
² China Petroleum Engineering Southwest Company, Chengdu 610041, Sichuan Province, China

^* Corresponding author: zhulinswpi65@gmail.com

Received: 16 August 2021
Accepted: 23 March 2022

Abstract

In order to reach the specification of water and hydrocarbon dew point, most of the water and C₃ and heavier hydrocarbons need to be removed from natural gas. Low Temperature Separation (LTS) process by throttling expansion or refrigeration is commonly employed for natural gas dehydration and de-hydrocarbon as the most economical method. In case of some special natural gas which contains small quantity of the wax (mainly C₁₆₊ components), wax is easily deposited in the throttling facilities that leads the blockage of internals of low temperature separator and affects safety operation. Oiling LTS process, a novel process for this kind of special natural gas, is investigated in this work. The oil is injected into the natural gas to reduce the wax precipitation temperature and thus to avoid wax blockage. It is a kind of improvement and innovation process based on conventional treatment ones. According to the simulation analysis and practical application for a natural gas processing plant in Aksu, China, the new process presents good performance. Also, it is found that the best injection point is at the inlet pipe of raw gas pre-cooler and the optimal injecting stream is from the three-phase separator. Also, the injection oil flowrate is determined by refrigerating temperature and the concentration of wax. Meanwhile, the detailed economic analysis of oiling LTS process was involved. Comparing the conventional process, its adding investment is around 423,583$ accounting on 5% total capital cost of this unit. However, from the comprehensive aspects, this optimized process presents a good economic benefit.