(Abstract)

At present, examination is being carried out by the domestic committee regarding the specifications of the international standard ISO for the sewerage industry. From this examination, I describe the progress to date and the current situation regarding the standardization Working Group (WG) and the Sub Committee (SC) on ISO/TC275 (Sludge recovery, recycling, treatment and disposal) and ISO/TC282 (Water reuse), in which Japan has participated in discussion by dispatching a secretariat, chairperson or experts.

(Abstract)

Waste treatment plants of the future will have to continue stable waste treatment as before, while coping with the shortage in human resources due to the declining birthrate, aging population and population decline. In order to solve this problem, our company is working on further automation of plant operation. In this paper, we will introduce advanced technology for controlling the quality of waste fed into the incinerator using image analysis and automatic combustion stabilization technology using artificial intelligence (AI). In addition, as the number of plants adopting the DBO method and Long-term Comprehensive Operation Consignment has increased, there is a demand for efficient plant management from private business operators. This article will also introduce our efforts on operation support with utilization of big data on plants obtained from the “Operation and Maintenance Administration Support System (POCSYS^®),” which has been in operation since 2016.

(Abstract)

We conducted a waste survey in Telangana State, India, as a measure to introduce a Waste to Energy plant in India, where waste problems have become prominent.

By conducting on-site survey and interviews on the state of general waste management in the corresponding region, we determined the sources and flows of waste, and confirmed the amount of waste generated from each source. In addition, we sampled waste from each source and conducted composition analysis and chemical analysis on 10 samples. Based on the results of these analyses, we estimated that the waste in this region could be processed by incineration, although it was lower in calorific value and had a tendency to be higher in ash content than general waste in Japan.

With this survey, we obtained information which would be helpful to determine the scale (incineration capacity) and the design waste characteristics of a Waste to Energy plant for the corresponding region.

(Abstract)

Although it is effective to raise the steam temperature in order to improve the efficiency in waste power generation, there are limitations to the steam temperature conditions so that the high-temperature corrosion of the superheater tube can be suppressed. Our company has previously conducted exposure tests in which tube materials were set inside an operating waste power generation boiler with the goal to address an increase in the steam temperature. In this paper, we will report on the effects of the gas atmosphere temperature and the tube surface temperature in the tube material on the high-temperature corrosion behavior of heat-resisting steel, which we learned through high-temperature corrosion tests using a corrosion test system capable of providing ash with a temperature gradient equivalent to one in an environment to which the superheater tube is exposed, in a joint study with Hokkaido University.

(Abstract)

The step grate stoker furnace we adopt in our sewage sludge incinerating power generation system has a tendency for the nitrogen oxide concentration in exhaust gas to be high, while it has the advantage of lower dinitrogen oxide emissions than fluidized bed incinerators. While it does not exceed the emission standards of the Air Pollution Control Act, introduction of nitrogen oxide reduction technology would be necessary if emission standards are made stricter by the local municipality and the like. In this study, we installed exhaust gas recirculation equipment in an existing sewage sludge incineration system adopting the step grate stoker furnace, and conducted tests on reduction of nitrogen oxide emissions through combustion control without use of any chemicals. As a consequence, we were able to reduce nitrogen oxide concentration to 86 ppm with low air ratio combustion at air ratio of 1.27. In addition, we combined exhaust gas recirculation with low air ratio combustion to conduct continuous operation at air ratio of 1.29 and exhaust gas recirculation rate of 10 %, and confirmed stable operation with nitrogen oxide concentration of 59 ppm and carbon monoxide concentration of 0 ppm. The dinitrogen oxide emission in this case was 0.02 kg-N2O/t-wet or lower, and we confirmed that simultaneous reduction of nitrogen oxides and dinitrogen oxide was possible in actual facilities.

(Abstract)

We developed a waste heat recovery system from low-temperature gas which features a corrosion-resistant heat exchanger adopting a fluoroplastic as the material, for the purpose of improving the heat utilization rate in municipal solid waste incineration plants. With the adoption of a fluoroplastic, which has high corrosion resistance, it is possible to avoid the problem of low-temperature corrosion and recover heat from exhaust gas in the low temperature range. In addition, it is possible to increase the overall heat utilization quantity for the plant and improve the power generation efficiency. In this article, we will describe the waste heat recovery system from low-temperature gas, and report on the long-term durability evaluation test using exhaust gas from a municipal solid waste incineration plant.