Evaluation of energy integration aspects for IGCC-based hydrogen and electricity co-production with carbon capture and storage

Abstract

Integrated Gasification Combined Cycle (IGCC) is a power generation technology in which the solid feedstock is partially oxidized with oxygen and steam to produce syngas. In a conventional IGCC design without carbon capture, the syngas is purified for dust and hydrogen sulphide removal and then sent to a Combined Cycle Gas Turbine (CCGT) for power generation. Carbon capture technologies are expected to play an important role in the coming decades for reducing the greenhouse gas emissions. In a modified IGCC design for carbon capture, the syngas is catalytically shifted to maximize the hydrogen level and to concentrate the carbon species in the form of carbon dioxide which can be later captured in a pre-combustion arrangement. After carbon dioxide capture, the hydrogen-rich syngas can be either purified in a Pressure Swing Adsorption (PSA) unit and exported to the external customers (e.g., chemical industry, PEM fuel cells) or used in a CCGT for power generation. This paper investigates the most important energy and process integration issues for hydrogen and electricity co-production scheme based on coal gasification process with carbon capture and storage (CCS). The evaluated coal-based IGCC case produces around 400 MW net electricity and has a flexible hydrogen output in the range of 0–200 MW (LHV) with a 90% carbon capture rate. The principal focus of the paper is on the evaluation of energy integration aspects so as to maximize the overall plant energy efficiency. Optimization includes heat and power integration of the main plant sub-systems (e.g., integration of steam generated in gasification island, with the requirements for syngas treatment, power generation in the combined cycle, best use of PSA tail gas in the power block, heat and power demand for acid gas removal unit, integration of air separation unit and gas turbine compressor etc.), sensitivity analysis (e.g., influence on ambient conditions).