Eco Clean Plaza Miyazaki encompasses facilities not only for waste incineration but also recycling and final waste management. It treats waste from Miyazaki city as well as nine nearby localities. The incineration facilities were designed and constructed by MHI and completed in October 2005. They incorporate three stoker type incinerators (Note1) each having a waste treatment capacity of 193 tpd, and related facilities. Power generation capacity using waste heat is 11,200 kW.

Under the refurbishment work, upgrades have been made to major equipment superannuated after more than 15 years in operation, to achieve stable combustion and operation over the long term. Replacements include equipment involved in combustion, cooling of combustion gas, waste gas treatment, waste heat utilization, ventilation, and ash removal, as well as electrical instrumentation. Plant service life extension work was carried out adopting MHIEC's proprietary new combustion control system. Stable combustion has been realized with a lower air ratio(Note2) than previously.

A CO2 reduction rate of 31.86 per cent (Note3) was attained, significantly higher than the original 17.25 per cent target. Factors contributing to the higher rate include: replacement to a feeder and boiler piping that enable higher durability responding to the low air ratio; increased power generation making efficient use of waste steam, achieved by changing to a low-temperature denitration catalyst; and the compound effects of adopting high-efficiency motors, converting to inverter type equipment, and optimisation of plant equipment.

The refurbishment work was difficult because it had to be undertaken amid continuing waste treatment, and because it coincided with the spread of the coronavirus pandemic. Nevertheless, work proceeded on schedule thanks to the further strengthening of coordination with all relevant counterparts and meticulous care exercised throughout, enabling the project to be successfully completed on time.

MHIEC succeeded MHI's environmental protection business in 2008, taking over its accumulated technological development capabilities in environmental protection systems and abundant expertise in the construction, operation, and maintenance of waste management facilities both in Japan and overseas. Based on this robust track record, the company is well positioned to propose comprehensive solutions encompassing all aspects from plant construction to operation and maintenance. Going forward, the Company will continue proactively proposing solutions for extending the service life of existing waste treatment facilities, coping with global warming, and reducing maintenance, management and other lifecycle costs, to contribute to realization of a carbon neutral society.

1A stoker furnace is the main type of waste-to-energy plant. Air is supplied from below a fire grate made of heat-resistant castings to propel the materials to be burned (waste, etc.).2Air ratio is calculated by dividing the real volume of air fed into the incinerator by the theoretical minimal amount of air necessary for waste combustion.3CO2 reduction rate based on the Ministry of the Environment's published material.