Optimization design of natural gas differential pressure power generation under flow fluctuation

Abstract

“Double carbon” is a two-stage carbon emission reduction goal proposed by China, and differential pressure power generation, as a natural gas (NG) residual pressure energy power generation technology, can effectively utilize natural gas residual pressure energy and also realize zero carbon emission. Aiming at the problem of low efficiency of differential pressure power generation due to the large fluctuation of natural gas flow rate, this paper calculates the potential of differential pressure power generation by using the exergy analysis method and confirms the feasibility of differential pressure power generation. Meanwhile, three optimization schemes are proposed to enhance the efficiency of pressure energy utilization in the purification plant, and economic analysis is used to compare the optimization results. Calculation results show that: when the average flow rate of natural gas is $300\times {10}^4$ m³/d, the theory of using differential pressure power generation can convert $647.3\times {10}^4$ kW·h of electric energy per year, while the case's annual power generation is $376.3\times {10}^4$ kW·h, which accounts for 58% of the theory; optimization results show that: the optimize the duration of power generation scheme, continuous power generation scheme, and high efficiency power generation scheme increase the annual power generation compared to the case by 5%, 9%, and 11%, and the net profit increases by 1.6%, 4.9%, and 10% respectively; therefore, it is feasible to adopt natural gas differential pressure power generation technology in purification plant, in which the payback period of high-efficiency power generation scheme is the shortest, only 3.24 years.