Capture and Compression Process of the Tomakomai Ccs Demonstration Project

Abstract

The Tomakomai CCS Demonstration Project was launched in April 2012 by the Ministry of Economy, Trade and Industry (METI), aiming for the practical use of CCS in Japan by around 2020. It required 4 years for EPC work of the demonstration facilities and CO2 injection was started on April 6, 2016. On November 22, 2019, the project achieved the target of 300,000 tonnes of cumulative injection and injection was terminated, whereas monitoring operations are being continued. Many important results were obtained through the demonstration, and those regarding capture and compression processes are summarized as follows:
• The capture process of the Tomakomai demonstration consists of an absorber, a stripper and a low-pressure flash tower with the absorber having a dual function of bulk absorption (lower part) and lean absorption (upper part). This process configuration, called a two-stage absorption process, achieved an average amine reboiler heat of 0.9 GJ/t-CO2, which is 1/2 to 1/3 of a conventional one stage absorption process that ranges from 2 to 3 GJ/t-CO2. Furthermore, process simulation studies of an “innovative process layout” suggested that the amine reboiler heat could be reduced to 0.487 GJ/t-CO2, which is 1/4 to 1/6 of the conventional heat requirement.
• The CO2 control system of two serial compressors which increases the pressure of captured CO2 up to 9.7 MPaG was able to achieve fully automatic control against periodic fluctuation of the CO2 flow rate after modification. The pressure of the captured CO2 (50 kPaG) upstream of the CO2 compressors could be stabilized; consequently, the CO2 flash of the low-pressure flash tower could also be stabilized,
• It was verified that the pressure control of the captured CO2 is very important in maintaining the steady flash effect of the low-pressure flash tower and subsequent stable performance of the bulk absorption in the absorber.
• The CO2 partial pressure of the absorber inlet was adjusted to conditions similar to those of a hydrogen production unit (HPU), ammonia production unit (APU) and integrated coal gasification combined cycle (Air Blown IGCC). The low amine reboiler heat obtained by the two-stage absorption process and the innovative process layout have the potential to be applicable to these processes, and greatly reduce the fuel cost as well as the corresponding avoided cost of CCS.

Keywords: CO2 Capture, CO2 Capture Process, CO2 Capture Energy, CO2 Compressor, CO2 Compressor Control System