Production costs of liquid fuels by indirect coal liquefaction

Abstract

Since the oil crisis of 1973 considerable interest has been shown in the production of liquid fuels from alternative sources. In particular, processes utilizing coal as the feedstock have received considerable interest. These processes can be divided into indirect, direct liquefaction and pyrolysis. This paper describes the modelling of indirect coal liquefaction processes in order to perform a technical and economic assessment of the production of liquid fuels from coal and lignite, using a variety of gasification and synthesis gas conversion technologies. The technologies are modelled on a ‘step model’ basis where a step is defined as a combination of individual unit operations which together perform a significant function on the process streams, such as a methanol synthesis step or gasification and physical gas cleaning step. Sample results of the modelling, covering a wide range of gasifiers, liquid synthesis processes and products are presented in this paper. There are a large number of combinations of feeds (3), gasifiers (10), products (6), other technical parameters (up to 20) and economic or financial parameters (17), as well as sensitivity studies, giving a total number of possible results in excess of 50 000. The main results show that methanol is the most attractive fuel relative to current market prices, followed by fuel alcohol, diesel from the Shell Middle Distillate Synthesis process, diesel from the Mobil Methanol Olefins Gasoline Diesel (MOGD) process, gasoline from the same process and finally gasoline from Mobil Methanol to Gasoline (MTG) process. There was a variation in production costs of up to 100% for most products depending on type of gasifier chosen and type of feedstock.