A look at the treatment process at the Shinagawa Incineration Plant
Shinagawa Incineration Plant in Tokyo converts rubbish into energy
A waste management plant in Tokyo is solving the city’s rubbish problem while producing clean electricity.
Trucks are loaded with rubbish and brought to the Shinagawa Incineration Plant in the capital where the refuse is weighed and put into the bunker.
Up to four days of rubbish per processing can be accumulated in the refuse bunker where two installed cranes stir the refuse below to ensure even burning.
The cranes automatically transfer the mixed waste from the refuse hopper to the incinerator which burns steadily using automatic combustion control at 850°C. Here the volume of the rubbish is reduced by a factor of 12.
A staircase-shaped fire grate, installed inside the refuse incinerator, is divided into three sections, including a dry fire grate, a combustion fire grate and a post combustion fire grate to incinerate waste completely.
The exhaust gas is funnelled into an area with a different atmosphere that suppresses dioxide generation by keeping the gas at over 850°C for two or more seconds. This high temperature is maintained by a gas burner at both the beginning and the end of combustion.
The gas generated when incinerating waste, also called exhaust gas, is sent to a gas cooler after the heat is converted to energy in the boiler. There, the high temperature gas is rapidly cooled to 150°C. This rapid cooling of the gas prevents the reformation of dioxins.
Afterwards, a special agent is blown into the exhaust gas which is then sent to the back filter. A cylindrical filter installed inside the back filter removes particulates, dioxins, sulphur oxide and hydrogen chloride. The gas then reacts with the sodium hydroxide solution in the gas scrubber, removing hydrogen chloride and sulphur oxide, making mercury harmless.
Water used throughout the process and any emitted by the plant is treated and reused. A reactor breaks down dioxins and other harmful substances remaining in the nitrogen oxide and exhaust gas. Finally, the purifying exhaust gas is released into the atmosphere from a 90 metre-high chimney.
Tokyo incinerator recycles everything from A to Z
The fires of Shinigawa Incineration Plant stop for just two months a year for maintenance.
While one is being maintained, the other still functions, keeping the plant open year round.
“It takes up to 30 minutes for garbage to turn into ash,” said Hidenori Yokoyama, the plant’s manager.
“While it’s burning, energy is being produced from the fire heat. There are 10,000 people living in 47 housing complexes 500 metres away from the plant in the Shinagawa Yashio Park Town so the heat generated here creates hot water which is sent to those houses,” he said.
A single crane of the two used to mix the rubbish can pick up three tonnes at a time. “That’s the equivalent of three trucks,” he said. “
The maximum capacity of garbage that can be held in the bunker is 8,000 tonnes and mixing takes three to four hours.”
The waste is picked up from households twice a week by 300 trucks daily. “We have 7,000 truck in total,” he said. “Ninety per cent of the final ashes go to Tokyo Bay in a landfill site and 10 per cent gets recycled as cement.”