Technical informationTECHNOLOGY

VOL.16 NO.1 (published in Jun-2008)

VOL.16 NO.1 (published in Jun-2008)
Technological Trend in Waste Incineration Residue Treatment
(*Energy and Environment Development Dept.)


Increasing need for the volume reduction and detoxifying and recycling of waste incineration residue has given birth to the melting and quenching methods in which the residue is turned into molten slag at a high temperature. In Japan, nearly one hundred facilities have working melting furnaces. In the melting process, most of the dioxins contained in the incineration residue are disintegrated, and the molten slag thus formed does not leach heavy metals, turning it non-toxic while reducing its volume. The melting process, however, consumes large amount of energy. For energy conservation and prevention of global warming, research and application studies are underway to develop a technology that enables detoxifying and utilizing incineration residue while using much less energy.

Development of Sewage Sludge Gasification System - Report No.3
-Three-month Continuous Operation-
Akihiro SAIGA*,Keiji TATSUMI*,Kazutake HAYASHI*,
Ryo TAKETANI**and Takahide HANEDA**
(*Energy and Environment Development Dept.,**Technical Research Institute, Tokyo Gas Co.)


We have been devoloping a sludge gasification system that enables effective utilization of the energy in the sewage sludge, and its volume reduction. Recently, we conducted a three-month continuous operation of the sludge gasification and power generation demonstration plant of 15ton/day throughput with 200kW power generation capacity. Since its inception in 2004, it has been proving us with operational data. The 90-day, 2,000 hour operation, a first in Japan, was accomplished, maintaining 92%-plus carbon conversion rate and 60~65% cold-gas efficiency for the duration, while tar-cracking and removal rate of approximately 98% was maintained. No problem due to tar was encountered, assuring steady operation. The power generation, at 200kW output, demonstrated a high generation efficiency of 38%. The demonstration test has proven that this gasification system is suitable for commercial application.

Denitrification of Effluent from Sludge Digestion
and Dewatering Process by ANAMMOX method
Keita TAKAKI*,Masayoshi SAKAGAMI*and Masahiko OKUDA**
(*Energy & Environmental Research Center,**Energy & Environment Development Dept.)


The need for the intensive removal of nitrogen and phosphorus from enclosed bodies of water has grown rapidly so as to prevent eutrophication. Currently, biological treatment is most commonly used as a means of nitrogen removal. It does require large facility, and results in high treatment cost.Lately, a new biological nitrogen removal technology called Anammox method (Anaerobic Ammonium Oxidation) is gaining attention, and we have been developing this technology for several years. The authors aimed at its practical use in the sewage treatment arena, and demonstrated application of Anammox method to the effluent from sludge digestion and dewatering processes that contains high concentration of nitrogen (ammonium). Optimum conditions and methods of operation have been established by a long-term demonstration run that has proven approximately 80% nitrogen removal. It has also achieved an operating speed that is more than 5 times as fast as the conventional methods, leading to the possibilities of great reduction in the operating cost and the size of the plant.

Operational Report of Ichihara New Energy Plant
Hidenobu NAKAGAWA*,Masahiro OKAWA*and Jun ABE*
(*Energy Engineering Dept. Ⅱ)


We have built for and delivered to Ichihara New Energy Co.a facility that incinerates non-recyclable materials such as plastics and wood waste using a special step-type stoker furnace. It uses the steam from a tail-end type boiler to generate electricity. The electric power thus generated is mostly exported, with a small portion used in-house. Additionally, heat is recovered from the turbine exhaust in the form of heated water that is sent to a greenhouse next door. We have also introduced a combustion control system for plant automation. This article reports on the outline of the plant, and the results of the test operation.

Operation Report of Bagasse Combustion Boiler for Suger Refineries
Keiji MUKAI*and Yuzuru NAKAE*
(*Energy Engineering Dept. Ⅰ)


At sugar refineries, sugar cane is shredded and pressed to squeeze out the sugar. When the sugar is removed, it is called bagasse, and many refineries use it as a biomass fuel. It is burned, and its thermal energy is recovered in the form of steam that generates electricity to be used in the plant as the source of heat and power.

We have built our largest boiler for Erawan Sugar Co., of Nongbualamphu province, in northeast Thailand. This article reports on the outline of this facility and its operation.

Operational Report of Wood Waste Burning Boiler
Keiji MUKAI*,Nagamasa HIDAKA*,Kenji KATAOKA*and Yuji HIROKAWA*
(*Energy Engineering Dept. Ⅰ)


With the prevailing anxiety regarding global warming, biomass fuels are gaining serious interest as something to replace fossil fuels, reducing environmental load. Above all, use of wood biomass is becoming very popular because it is widely available, and does not increase carbon dioxide in the atmosphere. It is a source of "carbon neutral" energy.

We are building increasing number of thermal recycling plants that burn wood biomass directly, starting with one delivered to Biopower Katsuta Ltd. This article reports on the major plants commissioned during the 2007~2008 period.

Development of Water-Cooled Stoker
(*Mechanical Design and Engineering Dept.)


We have been developing a water-cooled stoker that can handle high-calorie materials and high-temperature combustion with low air ratio while assuring longevity for its fire grates. The fire grates were cast with cooling-water pipes embedded in them. Heating tests using an electric furnace and combustion tests using an experimental small-scale stoker have been conducted, confirming the heat transfer characteristics of the water-cooled fire grates. In order to ascertain the longevity of the grates, we installed a water-cooled stoker in an industrial-waste incinerator and started demonstration tests burning wastes with the high estimated LHV of 16.7MJ/kg. (4,000kcal/kg) in March 2007. These water-cooled grates were installed where they would be exposed to such severe condition that existing air-cooled grates would need replacing within a year or two of operation. The water-cooled grates have been maintaining an average temperature below 200℃ , and stable operation is continuing. Follow-up monitoring of the grate longevity is going on, with satisfactory results.

Research on Formation and Removal of Ammonium Chloride from Non-catalytic Denitration
Akihiro MATSUMOTO*,Hiroshi MINOYA**,HWANG In-Hee**,
Toshihiko MATSUTOU**and Takayuki MATSUO**
(*Energy & Environment Development Dept.,Takuma Co., Ltd.,**Hokkaido University)


Non-catalytic denitration is a method of deoxidizing NO into N2 by injecting urea or NH3 into a waste incineration furnace. This method has an advantage over the catalytic de-NOx system as it uses simpler equipment, reducing operation cost. However, un-reacted NH3 reacts with HCl in the exhaust gas, forming NH4Cl that generates white plume. In this research, we studied the conditions of plume formation in the exhaust gas treatment system, and the possibility of preventing it by the addition of reagents in the bag filter (BF). For this purpose, a lab-scale experimental BF was built, and NH4Cl formation and removal tests have been conducted using NH3 and HCl control gases. Since the mol ratio of NH3 and HCl contained in the dust captured by the filter element remained approximately 1:1 regardless of the test conditions, it was assumed that most of the NO is captured in the form of NH4Cl. We therefore based our observation on the premise : capture ratio=NH4Cl generation ratio. The NH4Cl generation ratio increased as the temperature dropped, and by lowering the BF operation temperature to around 160℃ , most of the un-reacted NH3 seemed to be captured as NH4Cl. In addition, activated carbon applied to the surface of the BF elements would adsorb NH3. By adding activated carbon mist to the exhaust gas treatment process, therefore, better plume control will be achieved.