Four Japanese companies have developed a cogeneration system that recovers hot wastewater with high efficiency from a gas engine in the form of steam, announced the companies on Thursday.

A gas engine cogeneration system uses a gas engine to drive a power generator to generate electricity, while the system's waste heat found in the exhaust gas and the coolant of the gas engine are used as steam and hot water. Such systems have been widely introduced in office buildings, hotels, factories and the like.

"This system combines products marketed by the three manufacturers and can use the waste heat of a gas engine to efficiently convert hot water into steam," said a joint release issued by Tokyo Gas Co., Ltd., Mitsubishi Heavy Industries, Ltd., Miura Co., Ltd., and Kobe Steel, Ltd.

Specifically, the new system combines a "high-temperature specification gas engine" manufactured by Mitsubishi Heavy Industries that heats wastewater to a higher temperature to recover more steam; a "steam generator that uses the heat of wastewater" manufactured by Miura to efficiently convert hot wastewater into low-pressure steam; and a "compact screw-type steam compressor" manufactured by Kobe Steel that further pressurizes the converted low-pressure steam to make it suitable for use in factory production processes, said the release.

By combining these technologies, improvements were made to the high-temperature specification gas engine, and controls were developed for the efficient operation of the system.

"As a result of this new design, the steam recovery efficiency of this system has improved by approximately 10 percent compared with that of the system with only an exhaust gas boiler, and a combined efficiency of approximately 71 percent for power generation and steam use has been realized," it said.

Consideration was also given to convenience so that the settings can be changed in accordance with the usage conditions. For example, when the required amount of steam decreases, the user can switch to the operation of a conventional gas engine cogeneration system.

Mitsubishi Heavy Industries and the Tokyo Gas Group plan to begin selling this system in July 2015.

Truong Duy