Feasibility analysis of high-low temperature Fischer-Tropsch synthesis integration in olefin production

A novel system combining high- (HTFT) and low-temperature Fischer-Tropsch synthesis (LTFT) in olefin production is proposed. Utilizing syngas from coal gasification as the feed gas, the combined system integrates the advantages of HTFT and LTFT and results in an increased range of products, namely alpha-olefins (mainly C-4, C-6, and C-8), synthetic lubricant, gasoline, diesel, and naphth. The system avoids the risk of product market fluctuation and especially realizes the objective of diversifying production and maximizing economic benefit. Innovative ethylene oligomerization process is suggested to increase the alpha-olefins production. Different schemes of Fischer-Tropsch synthesis process are simulated by the aid of Aspen Plus software and a feasibility analysis on each of them is also done. In an economic perspective, the optimal ratio of HTFT to LTFT for the HTFT-LTFT combined plant with ethylene oligomerization scheme is 3:2. The project presents a low fresh water consumption of 0.138 kWh/USD, electricity consumption of 3.78 x 10(-3) kWh/USD and CO2 emission of 2.52 kWh/USD, and is expected to have a net present value of 8.66 billion USD and an annual average of return on investment of 42.03% under the current crude oil price 0.25-0.31 USD/L (2015-2017). These data demonstrate that the combined system has excellent economic profits and a remarkable ability to resist market risks compared to traditional single HTFT or LTFT process under a low crude oil price (below 0.5 USD/L). (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.