Introduction of a new DBO incineration facility - full overview of waste management, energy recovery, and related technologies in 2007

Introduction of a new DBO incineration facility - full overview of waste management, energy recovery, and related technologies in 2007

In 2007, the major issues surrounding waste disposal in Japan were the tightness of landfill sites and the environmental impact of incineration. against the backdrop of dioxin contamination, which became a social problem in the 1990s, the government established the Law Concerning Special Measures against Dioxins (enacted in 1999), and local governments rushed to introduce high-performance incinerators. The focus of attention in this trend was the development of incineration facilities based on the Design-Build-Operate (DBO) method, in which design, construction, and operation are outsourced to a single contractor. This method was designed to reduce costs and improve efficiency at the same time, with the private sector taking charge of everything from design and construction to operation, rather than the municipality building the facility on its own.

The new system introduced in the article is not simply an incineration process, but is equipped with a waste power generation system with highly efficient energy recovery. Conventional incineration facilities have focused on "waste volume reduction," but in the 2000s, following the Basic Law for Establishing a Recycling-based Society and the revision of the Waste Disposal and Public Cleansing Law, the emphasis shifted to effective energy utilization. In order to increase power generation efficiency, the latest technologies such as stoker furnaces and gasification melting furnaces were introduced, and district heat supply through the use of residual heat was also considered.

In addition, PPP (public-private partnership) was a key concept amid the financial difficulties faced by local governments. While a huge initial investment was required to construct the facilities, it was inevitable to comply with stricter environmental regulations. Therefore, a division of roles was sought whereby the private sector would be responsible for investment and operation, while the local government would ensure stable waste disposal and compliance with environmental standards. In the background was the Kyoto Protocol, which came into effect in 2005, and Japan made an international commitment to a greenhouse gas reduction target (6% reduction from 1990 levels). Energy recovery through waste power generation was seen as an effective way to achieve this reduction target, and at the same time, as a "quasi-domestic energy source" to cope with soaring fossil fuel prices.

The DBO system was technologically supported by advanced combustion, power generation, exhaust gas treatment, and ash recycling. Stoker furnaces and fluidized bed furnaces are the mainstream, with low NOx and stable combustion achieved by two-stage air combustion and oxygen trim control. Boilers are designed for high temperature and high pressure (400-450℃, 4-6MPa class), and corrosion resistant materials are used to improve power generation efficiency. The turbine is of the extraction condensate type, which provides both power generation and local heat supply. Residual heat is used to preheat feedwater and air, and to recover latent heat from the flue gas condenser, and in some cases, an absorption refrigerator is installed to supply cold heat (trigeneration).

The flue gas treatment system is based on a multi-stage configuration. Acid gas is neutralized with slaked lime, dioxin and mercury are adsorbed by activated carbon, and collected by a fabric filter in the final stage; for NOx, in addition to low NOx combustion in the furnace, SNCR using urea and ammonia is installed, and if necessary, SCR catalysts are installed. A continuous exhaust gas monitoring system (CEMS) was installed to constantly check O₂, CO, NOx, SOx, HCl, and dust.

Ash treatment and recycling are also important elements. In the 2000s, many gasification melting furnaces were introduced to completely melt the ash and convert it into slag, thereby realizing dioxin decomposition and recycling at the same time.

In addition, new technologies were introduced into the operation and management of the facility. Refuse quality is equalized by maintaining negative pressure in the refuse pit and mixing by crane, and power generation efficiency and exhaust gas performance are stabilized by optimizing combustion through AI control and model prediction control. On the maintenance side, Condition Based Maintenance (CBM) and vibration monitoring were introduced to minimize downtime.

In terms of contracts, performance-linked KPIs (power generation efficiency, operating rate, compliance with exhaust gas standards, ash recycling rate, etc.) were clearly defined, and the private sector bore some of the risk. The private sector was also encouraged to optimize costs throughout the entire life cycle of the facility.

All in all, the new incineration facility built in 2007 under the DBO scheme was a symbolic effort that combined the latest technology with a contractual scheme, against the backdrop of environmental regulations, energy security, and municipal financial difficulties of the time. Reducing environmental impact, maximizing energy use, and sustainable operation in collaboration with the private sector - this trinity concretely shaped the transition to a "recycling-oriented society" at that time.