METHODS TO COMBINE IGCC-POLYGEN CONFIGURATIONS WITH CARBON CAPTURE
Publication Date: 2012-Dec-31
The IP.com Prior Art Database
This invention proposes a new method of combining IGCC-polygen configurations for the production of hydrogen and power and the capture of carbon dioxide (CO2). Conventional polygen configurations require dedicated water-gas shift and AGR sections for different products and operating conditions. The proposed invention discloses a novel polygen configuration for high level carbon capture that uses only one common shift section that includes two shift stages and a combined AGR unit which will help reduce capital cost as well as maintenance expenditure.
This invention is related to integrated gasification combined cycle (IGCC) that converts coal and/or other types of carbon-containing feedstock into synthesis gas (syngas). When an IGCC plant produces power and chemical products, it is known as a polygeneration (polygen) plant. A conventional approach to polygen plants has two-stage water-gas shift for hydrogen production. A stream for carbon dioxide capture may originate from a separate stage of water-gas shift. Thus two acid gas removal (AGR) units for removal of impurities are required in this configuration, as shown in Fig. 1.
FIG. 1: Conventional polygen configuration with carbon capture system
Generally, coal and/or other feedstock are combusted in a gasifier and the raw syngas along with small amounts of impurities, liquid slag and fine solid particles is passed through a scrubber. In the conventional configuration of a polygen plant, as in Fig. 1, the syngas thus scrubbed is split into two first stage shift streams for hydrogen production and carbon capture respectively. The syngas for hydrogen production goes through a second stage shift before it enters the acid gas removal (AGR) unit. This AGR unit separates acid gas from the syngas rich in hydrogen, which is later be combined with acid gas coming from the carbon capture stream and is sent to a sulfur removal unit (SRU) or a tail gas unit (TGU), as illustrated in Fig. 1. The syngas with high hydrogen content is further purified with pressure swing adsorption (PSA). On the other hand, the syngas for carbon capture goes through the first stage shift then enters the second AGR unit in the plant. There are three main streams coming out of this AGR unit – i) clean syngas sent to combustion turbine(s) to generate electricity, ii) the acid gas and tail gas to be further treated in the SRU/TGU, and iii) a third stream high in CO2 content sent to CO2 capture and storage (CCS). This invention provides a more economical configuration by combining the water-gas shift and AGR sections for hydrogen production and carbon capture.
BRIEF DESCRIPTION OF DRAWINGS
A new method to combine IGCC-polygen plant configuration with carbon capture is disclosed in which:
Figure 1 shows the conventional configuration of a polygen plant with carbon capture system.
Figure 2 shows the proposed...