Construction of a Garbage Disposal Plant in Toshima City - The Realities of Municipal Solid Waste Policies and Related Technologies in the 1990s

Construction of a Garbage Disposal Plant in Toshima City - The Realities of Municipal Solid Waste Policies and Related Technologies in the 1990s

In the 1990s, Tokyo had an urgent need for high-performance incineration facilities and their decentralized location amid the tightening of final disposal sites and the growing concern about dioxin. In 1991, the Tokyo Metropolitan Government adopted the "principle of disposal within one's own ward" and clarified its policy to stably burn waste in each ward and shorten the distance of transportation. In addition to new facilities in Sumida and Minato wards, Komazawa Park in Setagaya Ward, Marunouchi 3-chome in Chiyoda Ward, Minami-Senju 3-chome in Arakawa Ward, and Ichigaya-Honmuracho in Shinjuku Ward were put on the chopping block as candidate sites, and in the same vein, a new plant was planned in Kami-ikebukuro (former site of a mammoth pool). The planned capacity is 400 tons per day, and construction is scheduled for completion in June 1999. The plant was designed to use waste heat for air conditioning and hot water supply within the building, with the aim of making the ur
ban facility function as an "energy hub" as well.

Kami Ikebukuro is characterized by the fact that it is located in the center of the city and is packed with the most advanced measures of the time, both in terms of equipment and operation. First, the combustion section uses two fluidized bed incinerators. The advantage of this system is that it is stable for low-heat and water-containing refuse and does not emit CO or unburned content, since fine-grained refuse is kept in a fluidized state in a high-temperature sand bed for uniform combustion. The simultaneous addition of lime can neutralize some of the acidic gases in the furnace, and the combustion temperature can be easily fine-tuned, making the system controllable and suitable for municipal refuse.

The core of the flue gas treatment is the standard high-performance flow of the time: quench, dry or semi-dry reaction tower (slaked lime spray), activated carbon spray, and bag filter. The quench is intended to quickly pass through the dioxin zone, which is easily resynthesized at 200-400°C. The fabric filter collects fine particles with high efficiency. Activated carbon was effective in adsorbing trace hazardous materials such as dioxin and mercury. For nitrogen oxides, SNCR (selective non-catalytic reduction) by spraying urea and ammonia water at the incinerator outlet was the basic method, and depending on the location, scale, and required emission standards, SCR (catalytic reduction) was considered in a later stage design. The combination of these two technologies will enable the plant to operate in line with the then-strengthened national standards and EU standards (0.1 ng-TEQ/Nm³).

Since the site is located in a dense urban area, the pit (refuse storage tank) and loading yard are managed under negative pressure, and the sucked air is used for combustion to suppress odor diffusion. An activated carbon deodorization system was installed as necessary, and noise was reduced by muffling the blower and induction fan, and by sound insulation of the exterior walls. In terms of safety and reliability, an operating philosophy that uses CEMS (continuous emission monitoring) to constantly measure major pollutants and link it to automatic control of the furnace is in widespread use. The disclosure of this continuous monitoring data became the core of consensus building at the residents' explanatory meeting.

In resource recycling, ferrous and nonferrous metals are recovered by magnetic separation and eddy current separation in the pretreatment stage. Bottom ash is granulated and sorted after metal recovery to be used as roadbed material, and fly ash is treated by adding chelating agents and cement solidification to suppress heavy metal elution. At that time, ash melting (plasma coke method) to convert ash into slag began to spread, and attempts were made to simultaneously reduce the final landfill volume and toxicity.

Exhaust heat is used to drive an absorption refrigerator and is supplied to air conditioning, hot water supply, and a heated swimming pool. Depending on site conditions, small-scale turbine power generation and heat supply to surrounding facilities (district heating and cooling) were also combined to pursue value as an energy source.

These technologies have changed the role of the waste incineration plant from simply "burning" to "safely recovering resources and heat to the maximum extent possible and coexisting with the city. The plan for Kami-Ikebukuro embodied the technological achievement that Tokyo had reached in the 1990s as a comprehensive solution to meet the three conditions of strict environmental requirements, urban location, and social consensus.