Success in “extending the life span of parts” Evolution of garbage incinerators brought about by a single technology

Ebara Environmental Plant Co., Ltd. (hereafter, Ebara Environmental Plant) designs and manages garbage disposal facilities, etc. The company has been working to extend the life span of parts used in garbage incinerators called “grates,” which has been an issue for many years. Together, we promoted this project at the “Ebara Manufacturing Technology Advanced Center (EMTAC),” a base that supports manufacturing for the entire Ebara Group. Using the technology “laser wall welding” developed by EMTAC, we have succeeded in extending the life span of the grate by more than 3 times. Ichita Hajime of the Production Process Innovation/Quality Assurance Management Department Manufacturing Technology Development Department New Technology Development Division, and Masamitsu Koshima of the Ebara Environmental Plant (EEP) Common Infrastructure Division Equipment and Equipment Design Division, who are members of EMTAC, talked about this challenge.

Koshima: There are several types of garbage incinerators, but what I'm involved in this story is called a “stalker type incinerator.” It was a project to extend the life of the part called the “grate” used in this stalker incinerator.

Koshima: One of the parts of the movable floor that transports the refuse in a waste incinerator is the "grate. Each grate is not very large, but hundreds of them are laid out and moved back and forth to agitate and transport the refuse as it is burned.

The inside of a garbage incinerator burns at close to 1000 degrees Celsius, and it is not uncommon for them to operate 24 hours a day for about 300 days a year. If a grate is used in that environment, it will gradually wear out and need to be replaced. This is because grates originally have corners, but they roll up due to high temperature corrosion and wear. Then, the way the garbage burns becomes uneven, leading to a situation where garbage cannot be properly transported, so regular replacement is necessary. However, replacing grates is a difficult task, and since work inside a garbage incinerator is carried out wearing protective clothing, the heat can also be severe.

Therefore, I thought about extending the life span of the grate and reducing the frequency of replacement. Not only does it lower replacement costs, but it also reduces the burden on workers working on site.

Additionally, this initiative will lead to a reduction in CO² emissions. This is because the manufacture of the grate itself emits a lot of CO², so if the life span is extended and the frequency of replacement is reduced, CO² emissions during manufacturing can be reduced.

Ichita : EMTAC is an organization that provides group-wide horizontal support for EBARA's manufacturing and works with divisions and group companies to solve problems faced by each manufacturing site together. We are also developing technologies for this purpose, and this time we utilized a technology called “laser overlay welding” for the grates. I am in charge of the development and verification of this technology at EMTAC.

Ichita:Overlay welding, to start, is a method of coating (overlaying) metal parts with melted high-performance metal or the same type of metal. This kind of welding can improve the performance of the original metal (base metal) or be used to repair worn parts. It is also a way to increase strength, overlaying a harder metal on the surface of a softer metal.

Laser overlay welding is achieved by using a laser. Because it can be done with lower heat input than other overlaying methods, it has benefits that include the base metal being less likely to deform, strong adhesion, and the overlay metal being less likely to peel off. With this project, we tried to increase the durability and extend the service life of new grates by applying laser overlay welding to the surface.

Koshima : life of grates has been a long-standing challenge in our industry. In response to this issue, each company has been devising materials and implementing various approaches, such as cooling with air or water. While life can now be extended due to these approaches, the current situation is that parts costs increase when materials are upgraded, and that cooling with air or water requires that amount of cooling equipment and energy for cooling still remain. If you use energy, you're emitting the amount of CO² that makes that energy, right?

Koshima : The first meeting was in 2020/10, so we were able to introduce the actual product in just six months after that. There were doubts about whether this initiative would actually be effective in increasing longevity, and whether it would be cost-effective even if it were effective, but since there was almost no risk, I wanted to introduce the actual machine as soon as possible. Therefore, at the time of the first meeting, it was decided as a common goal of EEP and EMTAC to introduce a laser meat grate during maintenance at the Fukushima City Arakawa Clean Center in April 2021, and I think we were able to achieve this by working closely together on development towards that goal. I think it was a pretty tough schedule for EMTAC, but I really appreciate your support.

Koshima : Since the frequency of grate replacement can also be reduced, the amount of CO² emitted by grate manufacturing can also be reduced to 1/3 or less, and the load on grate replacement workers can also be reduced. Based on these results, other facilities operated and maintained by EEP are also proceeding with the introduction of laser wall grates.

Ichita : In the future, I hope this technology will spread not only at the Ebara Environmental Plant, but also at various businesses and sites, and there are still places where it can be useful. If you have even the slightest interest, please speak to EMTAC.

Koshima : I think we were able to communicate with real
Ichita : that use this technology? If you don't understand that, there is also a possibility that they will release something that costs too much due to excessive specifications. Once again, I felt the importance of developing technology while listening to voices from the field.

Ichita : company with a long history, but when I actually work, I feel like I'm working on something new. This project is one of them. I hope we can continue to increase these efforts.

We are working on an integrated system from the design and construction of garbage disposal facilities and energy plants, operation and maintenance, and even recycling of by-products such as electricity and ash generated from them. There are few companies that are responsible for design, construction, and subsequent operation and maintenance, and management, which can be said to be a characteristic of the company. Also, in recent years, we have been focusing on developing technologies and systems to return garbage to society by converting garbage into electricity, steam/hot water, recycled stone, chemical raw materials, etc.