Mitsubishi Heavy Industries Technical Review Vol. 61 No. 2 (June 2024)
1Demonstration of CO2 Capture from Flue Gas of WasteIncineration Facility for Use in Methanation

YUKI ENDO*1TOSHIKI SHIMIZU*2SHINSUKE NAKATANI*3

AKIRA KANEKO*4

AYUMI IWAMOTO*5

Mitsubishi Heavy Industries, Ltd. (MHI) and MHI Environmental & Chemical Engineering
Co., Ltd. (MHIEC), together with the City of Yokohama and Tokyo Gas Co., Ltd. (Tokyo Gas),
started a demonstration test of the carbon dioxide capture and utilization (CCU) process, in which
CO2 is separated and captured from the flue gas of the Tsurumi waste-to-energy (WTE) plant of theResources & Waste Recycling Bureau, Yokohama City, and then used as a resource. The captured
CO2 is transported to a different demand location, where it is subject to methanation. This CCU
demonstration project based on regional cooperation is Japan’s first of its kind. The project
purpose and overview are presented in this report.

|1. Introduction
The Japanese Government’s Plan for Global Warming Countermeasures, which was revisedin 2021, sets a target of reducing greenhouse gas (GHG) emissions by 46% by 2030 from thebaseline year of 2013. A further 50% reduction will be aimed in order to achieve carbon neutrality(CN) by 2050. In 2020, the GHG emissions from the waste treatment sector accounted for 3.5% of
the total emissions in Japan, and about 80% of these emissions came from the incineration ofwaste, etc.
Also with a view to achieving CN by 2050, in the Sixth Strategic Energy Plan, the synthetic
methane produced by methanation of hydrogen and CO2 is considered to have high potential for
decarbonizing city gas, because of its applicability to the existing infrastructures and facilities suchas city gas pipelines.
Burning biomass releases CO2, which is also counted as the CO2 from waste incineration.
With this in mind, if CO2 is captured to achieve net zero of GHG emissions and the captured CO2
can be supplied in a circular manner as a resource to the industrial and civilian sectors (i.e.,realizing a circulation of carbon), this will be able to greatly contribute to transition towards CN inJapan.
This report presents the ongoing demonstration test at the Tsurumi WTE plant, in which CO2
in flue gas is separated and captured for use in methanation.

|2. Demonstration project structureThis demonstration project is jointly conducted by the City of Yokohama, Tokyo Gas, MHIand MHIEC. The role of each participant is shown in Figure 1.

*1 Manager, Project Management Unit, Engineering Division, Mitsubishi Heavy Industries Environmental & Chemical Engineering Co.,Ltd.
*2Engineering Manager, Project Management Unit, Engineering Division, Mitsubishi Heavy Industries Environmental & Chemical*3Manager, Low Carbon Solutions Technology Development Department, GX Solutions, Mitsubishi Heavy Industries, Ltd.

Engineering Co., Ltd.
*4

Low Carbon Solutions Technology Development Department, GX Solutions, Mitsubishi Heavy Industries, Ltd.

*5Ecosystems Research Department, Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.

Mitsubishi Heavy Industries Technical Review Vol. 61 No. 2 (June 2024)
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Role of each participant in demonstration project(1)|3. Demonstration project purpose and facility overview
The purpose of this demonstration project is to confirm the capability of separating andcapturing CO2 from the flue gas generated at a waste incineration facility in a stable manner, which
is followed by the use of the captured CO2 as feedstock for methanation. The adopted technology
for separation and capture is a proven method of chemical absorption. The possible concerns aboutburning waste are the quickly changing combustion properties, and the impact of trace amounts ofacid gases and trace constituents on the absorption solution degradation and the methanation
process, which we investigated.
The demonstration test is outlined as CO2 in the flue gas from the Tsurumi WTE plant being
separated and captured, followed by transportation by tank containers for approximately 800
meters to the Tokyo Gas Yokohama Techno Station for use in methanation. Figure 2 shows thelocations of the two facilities. Figure 3 is a flow diagram of the demonstration process. Theexterior views of the equipment are given in Figure 4.

Figure 2

Locations of facilities

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Figure 3

Flow diagram of demonstration process(1)Figure 4 Exterior views of equipment (left: separation and capture system, and right:compressor)

The temperature of flue gas from the Tsurumi WTE plant is approximately 180°C. At theinlet of the stack, part of the flue gas is diverted from the existing flue gas duct and sent to the CO2
separation and capture system. This flue gas containing CO2 is cooled by the quencher before it ispressurized by the blower installed downstream of the quencher. The flue gas is then sent to theabsorber, in which it comes in contact with the amine absorption solution, allowing CO2 to beabsorbed into the absorption solution. The flue gas from which CO2 is removed is washed withwater before returned to the stack as a flue gas with almost no CO2. On the other hand, theabsorption solution containing large amounts of CO2 is sent to the regenerator, where it is heated torelease CO2. The absorption solution is thus regenerated. This absorption solution is returned to theabsorber for reuse. The captured CO2 is sent to the compressor, where it undergoes the processes ofcompression and dehumidification before being stored in ISO tank containers.
Table 1 gives the specifications of the CO2 separation and capture system. Two ISO tankcontainers are prepared for use. The compressor at the Tsurumi WTE plant is used to fill thecontainers. Once filling is completed with one container, the other empty container takes its place.
The filled container is transported to the methanation facility of Tokyo Gas.
Table 1 Specifications of CO2 separation andcapture system
CO2 capture capacity
CO2 purity

0.3 t/d99.9 vol%-dry|4. Demonstration test results
This demonstration was conducted in two stages. It started with the operation of the CO2
separation and capture system in January 2023. In June 2023, the compressor was installed. The
methanation test using ISO tank containers commenced on July 28, 2023.
The captured CO2 was supplied to the methanation facility installed on the premises of theTokyo Gas Yokohama Techno Station. The performance of the facility was evaluated. The
produced methane was fed to commercial gas engine generators or was used for boiler operation
testing, without being purified.

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At present, both the CO2 separation and capture system and the methanation facility areoperating continuously in a stable manner. We will collect more data such as long-term operationaldata, thereby enabling the CO2 separation and capture system to be rolled out widely for theapplication to waste incineration facilities.

|5. Conclusion
One of the contributions expected toward achieving CN by 2050 is the promotion ofdecarbonization by introducing the technology for capturing and effectively utilizing CO2 fromwaste incineration facilities. This project is based on regional cooperation and is Japan’s first of its
kind, aiming to demonstrate the separation and capture of CO2 generated at a waste incineration
facility and the use of captured CO2 in methanation. The role of a waste incineration facility, whichis expected to be fulfilled as a regional base of decarbonization, is significant. Looking forward, wewill improve the reliability of our CO2 capture system by acquiring the long-term operational data,
as well as expand the range of effective applications.

References(1)

Yokohama City Press Release, (in Japanese)
https://www.city.yokohama.lg.jp/city-info/koho-kocho/press/shigen/2021/0224_CCUjissyousiken.html