VOL.27 NO.1 (published in Jun-2019)

Photo in Cover :Environmental Forest Center, Kizugawa

VOL.27 NO.1 (published in Jun-2019)

Transitions of NOx Reduction Technology in Waste Incineration

Kazuhiro SATO*, Masaaki KURATA*, Takeshi YASUE**
(*Mechanical Design & Engineering Dept., **Environmental Engineering Dept. 1)

(Abstract)

Nitrogen oxide reduction technology in waste incineration comprises mostly dry methods such as the combustion control method, and selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) methods, and it is being advanced in concurrence with the reinforcement of the laws and regulations including the Air Pollution Control Law. Our company has developed technology which can stably remove nitrogen oxides to below the emission standard value while reducing the equipment cost and the maintenance cost, and has made efforts to introduce it into actual plants. This article explains the transition of emission regulations for waste incinerators related to nitrogen oxides, the transition of nitrogen oxide reduction technology in our company, and our latest technology.

Operation Report on the Environmental Forest Center, Kizugawa

Jiro HIROSUMI*
(*Environmental Design Dept. 3)

(Abstract)

The “Environmental Forest Center, Kizugawa,” a waste treatment facility which was ordered by Kizugawa City, was completed in August, 2018. The incineration scale of this facility is 94 t/24 h, and the thermal energy from incinerating waste is recovered to cover the internal power consumption through power generation with a steam turbine generator, with the surplus power being sold. This article reports on the features and operating conditions of this facility.

Plant Renewal Plan Utilizing Building Stock(Suminoe Plant renewal and operation project)

Kohei BESSHI*
(*Environmental Engineering Dept. 1)

(Abstract)

In September 2018, we received an order for the Suminoe Plant renewal and operation project from the Osaka city Yao city Matsubara city environment facilities association. This project is one in which the building stock was utilized so that the internal facilities are renewed while keeping the existing building. Though there was a problem in the Building Standards Law in utilizing the existing building, we solved it by preparing a minute renewal plan which took into consideration the exemption stipulation in the law. In addition, this plan was prepared so that the renovation added functions and values which had not been present in the existing plant, such as earthquake resistance improvement, tsunami countermeasures, and rooftop gardening.

Imabari City Waste Management Center, “Phase Free” Disaster Prevention Base

Masahiro TOZAKI*
(*Environmental Engineering Dept. 1)

(Abstract)

The Imabari City Waste Management Center was opened in April 2018 with the aim of contributing to the local community as “a gathering place for local residents” during normal times and “disaster prevention base (evacuation shelter)” during disasters, not to speak of the stable treatment of waste. Its feature in particular is that it implements measures to improve the values of the facility during both normal times and disasters in terms of hardware and software by adopting a new concept called “Phase Free” and utilizing disaster prevention efforts during normal times, and we were awarded the “Grand Prix,” the highest award, in the “Japan Resilience Award (Resilience Grand Prize) 2019.” This article reports on the “Phase Free” efforts in this facility, and the disaster prevention efforts in terms of both hardware and software.

Study on Methods to Reduce Nitrogen Oxides in Step Grate Stoker Sludge Incinerators

Yasuo HORII*, Takaaki MIZUNO*, Naoki KABUTAN*, Kenichi SHISHIDA*
(*Sewerage Engineering Dept.)

(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 the sludge incineration system using the step grate stoker furnace we have constructed satisfy the regulation values of Air Pollution Control Law, it may be necessary to introduce NOx reduction technology if a more strict regulation value is applied by the local government. In order to confirm the effect of reducing the concentration of NOx in exhaust gas, we conducted a combustion test using a stoker combustion demonstration facility installed within our own plant and a material to be combusted (simulated dried sewage sludge) in which each component was adjusted to be equivalent to dry sludge in this study. As a consequence, we confirmed that the NOx concentration in the exhaust gas could be reduced from 150 ppm to 50 ppm or lower with low air-ratio combustion and exhaust gas recirculation, which are NOx emission suppression methods based on combustion control, and that the N2O concentration at that time was 5 ppm or lower and the emission amount approximately 0. 01 kg-N2 O/t-wet, making it possible to simultaneously reduce NOx and N2O.

Development of Indirect Heating Sludge Dryer

Yasuo HORII*, Takaaki MIZUNO*, Naoki KABUTAN*, Kenichi SHISHIDA*
(*Sewerage Engineering Dept.)

(Abstract)

We adopt an indirect heating sludge dryer as one type of water content reduction technology in the sludge incinerating power generation system using a step grate stoker furnace. In order for this type of dryer to perform stable sludge incinerating power generation at a treatment plant with large fluctuations in the quantity or quality of dehydrated sludge or a treatment plant where the sludge generation quantity and the properties of sludge are expected to fluctuate as the area for sludge treatment is increased, it is necessary to adjust the moisture evaporation speed (amount of water evaporation per unit heat transfer area), which is the treatment capacity. Based on this background, we have developed a dryer with an expanded adjustment range for quantitative and qualitative fluctuations in sludge, which is a conventional dryer with the addition of a function to adjust the moisture evaporation speed. We conducted a demonstration on this dryer in an actual sewage treatment plant, and confirmed that the moisture evaporation speed could be adjusted within the range of 70 to 130%. In addition, we conducted continuous operation for 24 hours in each season, and found that the moisture evaporation speed varied depending on the season and that it tended to become higher the lower the combustible content.

Waste Heat Recovery System from Low- temperature Exhaust Gas

Takahiro IWAMOTO*, Takayuki KUDOH*, Yasuyuki FUJITA*
(*Energy & Environmental Development Dept.)

(Abstract)

In recent years, there is a growing demand for the effective utilization of waste heat generated from municipal solid waste incineration plants to be increased. In order to recover the waste heat from the low temperature range which has not been recovered conventionally due to the problem of low-temperature corrosion, our company is developing a waste heat recovery system from low-temperature gas which features a heat exchanger adopting a fluoroplastic with corrosion resistance. By adopting this system, it will be possible to recover heat from exhaust gas at the outlet of the bag filter, and improve the power generation efficiency. We manufactured demonstration equipment of 1/3 of the scale of the actual facility and carried out a test on heat recovery from refuse-derived fuel combustion exhaust gas, and confirmed that the actual measurement values for the heat exchange performance of the heat exchanger adopting fluoroplastic were equivalent to the theoretical calculation values.

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