Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
1Carbon Neutral Initiatives for Works andPlants of MHI Group

JUNNOSUKE NAKATANI*1 YUICHI OTANI*2

HIDEYUKI UECHI*3

KATSUYA SOEDA*4TATSUO NAKAGAWA*5

HAYATO SAKAKI*6

Mitsubishi Heavy Industries Ltd. Group (MHI Group) announced its Mission Net Zero goalin October 2021 to reduce CO2 emissions from its business activities to Net Zero by 2040. Thisinitiative targets Works and Plants, which are the main sources of emissions from businessactivities, and aims to minimize CO2 emissions intensity on the demand side through a scientificapproach, to materialize a feasible means to achieve that, and to realize an energy transition on
the supply side. This report focuses on the minimization of CO2 emissions intensity on the demandside and introduces an initiative example where an approximately 50% reduction was attained.
MHI Group will use this initiative as a showcase to contribute to the achievement of carbon
neutrality around the world by offering MHI Group's products and services "in total, fromengineering to equipment installation and O&M".

|1. IntroductionMHI Group business activities in 2021 had direct CO2 emissions from Works/Plants andother facilities (corresponding to Scope 1, CO2 emissions from the combustion of gas and otherfuels) and indirect CO2 emissions from the use of electricity in Works/Plants and offices(corresponding to Scope 2) that totaled 138,000 tons and 374,000 tons, respectively. In this way,
MHI Group's production factories are the main CO2 emissions source of its business activities.
MHI Group has more than 20 production bases throughout Japan, and under the basic policy of3E+S (Energy security, Economic efficiency, Environment, and Safety), the bases have been
actively working on energy saving for their energy-intensive facilities such as boiler facilities, heat
treatment furnaces, electric furnaces, heating and drying furnaces, steam utilization facilities andprocesses, and air conditioning facilities, in other words, global environmental conservation andCO2 emissions reduction.
Figure 1 shows the roadmap toward Mission Net Zero, which is MHI Group's current goal.
MHI Group aims to achieve carbon neutrality by 2040 by strengthening and accelerating theexisting initiatives and actively introducing our own technologies, such as high-temperature heatpumps, hydrogen technology, and CCUS (Carbon dioxide Capture, Utilization, and Storage), toWorks/Plants. In order to realize this, it is necessary to consider both the demand side, which
consumes energy, and the supply side, which provides energy.
In addition to the above, MHI Group possesses a wide range of required technologies andproducts that contribute to carbon neutrality and is promoting technological development. Byutilizing various product technologies such as heat pumps, engineering technologies, energymanagement technologies, and their basic technologies, and applying them to Works/Plants, MHI*1 Chief Staff Manager, Technology Planning & Management Department, Technology Strategy Office, Mitsubishi Heavy Industries,Ltd.
*2 General Manager, Heat Transfer Research Department, Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.
*3 Chief Staff Researcher, Heat Transfer Research Department, Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.
*4 Chief Staff Engineer, Facilities Management Department, Value Chain Headquarters, Mitsubishi Heavy Industries, Ltd.
*5 Deputy Director, Foundry Center, Value Chain Headquarters, Mitsubishi Heavy Industries, Ltd.
*5 Foundry Center, Value Chain Headquarters, Mitsubishi Heavy Industries, Ltd.

Mitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
2Group aims to achieve carbon neutrality and meet the demands of the international community, as
well as to use this initiative as a showcase for "total services" from engineering to equipment
installation and O&M and to contribute to the achievement of carbon neutrality around the world
and the realization of a sustainable society.

Figure 1

Roadmap toward Mission Net Zero|2. Concept and policy of initiative
Figure 2 shows the approach to be considered in proceeding with this initiative.

Figure 2 Consideration concept

It is necessary to consider the two sides of energy, the demand side, which uses electricity
and fuel (heat), and the supply side, which produces them. On the demand side, it is necessary toeliminate waste and thoroughly reduce the amount of energy used. Rationalization and optimizationof manufacturing procedures in product manufacturing as well as reduction and straightening ofprocesses in Works/Plants are important. It is also important to optimize production planning andenergy flow, promote heat cascading, and use heat pumps for reuse of heat. On the supply side, it isimportant how to use non-fossil energy sources and how to best mix them to meet the demand thathas been optimized (minimized) by consideration on the demand side.

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Therefore, we first minimized the CO2 emissions intensity on the demand side, and thenconstructed a carbon-neutral energy supply system on the supply side.
Figure 3 shows a concrete approach to the consideration. Step 1 is to calculate the theoreticalamount of energy that is truly necessary to achieve the required objectives in energy consumption
processes in Works/Plants, including a review of the processes. The calculated value is an ideal
value with zero losses, but it is a simple and easy-to-understand target value for minimizing theCO2 emissions intensity. It is important how to attain the closest possible value to this ideal value,
and the concrete measures to realize it are developed in Step 2. Step 3 is to consider the energy
supply system using non-fossil energy while applying the concrete measures considered in Step 2.
Figure 4 shows a schematic view of CO2 emissions reduction for achieving carbon neutrality
through Step 1 to Step 3, which will minimize CO2 emissions as well as capital investment for theintroduction of non-fossil energy systems.

Figure 3

Consideration approach

Figure 4
Schematic view of CO2 emissions reduction towardachievement of carbon neutrality|3. Initiative example
In promoting these initiatives, we have selected a model factory from among ourmanufacturing bases for study and are working to minimize the CO2 emissions intensity of thecasting process at Foundry Center in Kobe Shipyard & Machinery Works Futami Plant, where theratio of thermal energy is comparatively high.
Figure 5 shows an example of the casting process. In the casting process, a lot of energy isconsumed in the drying process after mold making, the material melting process, the preheatingprocess of the ladle that receives materials (i.e., molten metal) in the melting furnace and pours theMitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
4molten metal into the mold, and the heat treatment process. This report introduces an initiative casefor the ladle preheating process.

Figure 5

Example of casting process

Because of its application, the ladle is preheated to a high temperature by using a gas burner
before molten metal is poured into it to avoid damage such as cracking caused by thermal shock
when molten metal at a temperature of 1,500°C or higher is poured from the melting furnace, andto avoid solidification of molten metal due to temperature drops caused by heat radiation during therequired setup time between processes, and other problems. The time required for this preheating isdetermined empirically based on past experience, and a lot of energy is consumed.
The key points to minimize the CO2 emissions intensity of this process are to shorten thesetup time to reduce the loss due to heat radiation and to predict the decrease in molten metal
temperature due to heat radiation according to the ladle preheating time.
For shortening the setup time, work items and their purposes were thoroughly reviewed toreduce unnecessary and duplicated work and adopt measures that make it easier for operators towork (e.g., changing work positions). On the other hand, for predicting the decrease in molten
metal temperature, the prediction accuracy was improved by making full use of our analysis
technologies for heat transfer, etc., that have been developed for a wide range of products andverifying the analysis results with minimum data, such as the temperature measurement datanecessary for the setup work. Figure 6 shows a schematic diagram of estimating ladle preheatingtime based on the setup time and the molten metal temperature prediction result from heat transferanalysis, using the molten metal temperature required in the next process as the criterion. The ladlepreheating time was optimized (shortened) based on this evaluation, and then verified in the actualprocess. As a result, it was confirmed that the ladle was not damaged during operation and the gas
consumption required for preheating was successfully reduced by a significant amount of about
50%.
In each process, operating conditions such as temperature are organically related to theprocess conditions of the preceding and following processes. Moving forward, to minimize CO2emissions intensity at this Foundry Center, we will reexamine the manufacturing processes andoperating conditions to optimize the casting process as a whole, rather than each process
individually. Based on that, we will construct a system that can achieve carbon neutrality in theenergy supply.
Although still under development and having uncertainties in cost and supply, there areseveral possible means and combinations instead of the use of conventional fossil fuels such as citygas, including the use of solar heat, heating with electric heaters powered by renewable energy, theuse of hydrogen, ammonia fuel, and biomass, and the utilization of high-temperature heat pumps
and heat cascading/storage aiming for zero factory waste heat. In addition, we will build an EMSMitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
5(Energy Management System) factory optimization tool that incorporates these uncertainties toreduce CO2 emissions intensity by observing equipment operating conditions in real time during its
operation, and also to reduce process waste, improve the equipment utilization rate, reduce costs,
and shorten work lead times by comparing and analyzing Works/Plants production plans and actualresults.

Figure 6 Schematic diagram of molten metal temperature prediction
based on heat transfer analysis and ladle preheating time estimation|4. Conclusion and future prospect
In order to achieve carbon neutrality in Works/Plants, it is essential to minimize the CO2emissions intensity there and then make an energy transition in the energy supply system. This
report focused on initiatives to minimize CO2 emissions intensity and introduced an example casewhere such an initiative for a ladle preheating process in casting achieved a significant reduction of
about 50% in CO2 emissions intensity and was applied to an actual process. Consequently, theeffectiveness of a method to derive the amount of energy that is truly necessary with a scientificapproach and then consider concrete measures that can achieve it was demonstrated.
This example case started from the viewpoint of energy reduction, but the contribution ofprocess review to shorten the setup time was significant. As shown in Figure 7, there is a highaffinity between energy reduction, elimination of waste in processes, process straightening, andcost reduction and work lead time shortening as an effect obtained thereby. These are important
perspectives to consider in the reduction of CO2 emissions intensity.

Figure 7 Affinity between energy, process
straightening, cost reduction, and lead timeMitsubishi Heavy Industries Technical Review Vol. 59 No. 4 (December 2022)
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MHI Group has a wide variety of factories and energy consumption facilities. In the future,
we will select a model factory for taking initiatives, after determining the effects of their expansion
to other factories, and optimize the entire manufacturing process to minimize CO2 emissions
intensity while maximizing the results of the initiatives. After that, we will build a system thatenables carbon neutrality in energy supply.
We believe we can achieve the carbon neutrality of MHI Group Works/Plants through these
initiatives and respond to the demands of the international community. We will also use the resultsof these initiatives as a showcase to provide our customers with our products and services "in total,from engineering to equipment installation and O&M", thereby contributing to the achievement ofcarbon neutrality around the world and the realization of a sustainable society.