Shell coal IGCCS with carbon capture: Conventional gas quench vs. innovative configurations

The Shell coal integrated gasification combined cycle (IGCC) based on the gas quench system is one of the most fuel flexible and energy efficient gasification processes because is dry feed and employs high temperature syngas coolers capable of rising high pressure steam. Indeed the efficiency of a Shell IGCC with the best available technologies is calculated to be 47–48%. However the system looses many percentage points of efficiency (up to 10) when introducing carbon capture. To overcome this penalty, two approaches have been proposed. In the first, the expensive syngas coolers are replaced by a “partial water quench” where the raw syngas stream is cooled and humidified via direct injection of hot water. This design is less costly, but also less efficient. The second approach retains syngas coolers but instead employs novel water–gas shift (WGS) configurations that requires substantially less steam to obtain the same degree of CO conversion to CO2, and thus increases the overall plant efficiency. We simulate and optimize these novel configurations, provide a detailed thermodynamic and economic analysis and investigate how these innovations alter the plant’s efficiency, cost and complexity.

► We aim at defining the preferred IGCC design for dry feed gasifiers with CO2 capture. ► Multiple options of syngas cooling, humidification, and WGS are considered. ► Plants are designed, modeled, numerically optimized and costs are carefully assessed. ► Partial water quench has poor efficiency but low capital cost, then good performance. ► Gas quench with the ECN staged WGS design has the best thermo-economic performance.