Simulation of a syngas from coal production plant coupled to a high temperature nuclear reactor

[摘要] ENGLISH ABSTRACT: In light of the rapid depletion of the world's oil reserves, concerns about energysecurity prompted the exploration of alternative sources of liquid fuels fortransportation. One such alternative is the production of synthetic fuels with theindirect coal liquefaction process or Coal-To-Liquids (CTL) process. In thisprocess, coal is burned in a gasifier in the presence of steam and oxygen toproduce a synthesis gas or syngas, consisting mainly of hydrogen and carbonmonoxide. The syngas is then converted to liquid fuels and a variety of usefulchemicals in a Fischer Tropsch synthesis reactor. However, the traditionalprocess for syngas production also produces substantial amounts of carbondioxide. In fact, only about one third of the carbon in the coal feedstock ends upin the liquid fuel product using traditional CTL technology. If additional hydrogenwas available, the carbon utilisation of the process could be improvedsignificantly. The high temperature reactor (HTR) is a gas cooled Generation IVnuclear reactor ideally suited to provide electrical power and high temperatureheat for the production of carbon neutral hydrogen via high temperatureelectrolysis. The integration of an HTR into a CTL process therefore provides anopportunity to improve the thermal and carbon efficiency of the CTL processsignificantly. This thesis presents a possible process flow scheme for a nuclearassisted CTL process. The system is evaluated in terms of its thermal or syngasproduction efficiency (defined as the ratio of the heating value of the producedsyngas to the sum of the heating value of the coal plus the HTR heat input) aswell as its carbon utilisation. If the hydrogen production plant is sized to produceonly enough associated oxygen to supply in the needs of the gasification plant,syngas is produced at about 63% thermal efficiency, while 71.5% of the carbonis utilised in this process. It was found that the optimum HTR outlet temperatureto produce hydrogen with a high temperature steam electrolysis process is850°C. If enough process heat and electrical power are available and process equipment capacities are sufficient, the carbon utilisation of the process could beimproved even further to values in excess of 90%.

[发布机构] Stellenbosch University