VOL.20 NO.2 (published in Dec-2012)

Photo in Cover :The West Environmental Energy Center of Kanazawa City

VOL.20 NO.2 (published in Dec-2012)

Feed-in Tariff Scheme for Renewable Energy-Focusing on Biomass Power Generation-

Susumu UNO* and Tomohisa OHTA*
(*Tokyo Technology Research & Planning)

(Abstract)

The Feed-in Tariff Scheme to accelerate investment in renewable energy sources was initiated. This scheme obligates electric utilities to purchase power generated by the facilities certified by the Minister of Economy, Trade and Industry using renewable energy sources such as solar power, wind power, geothermal power, medium/small-scale hydro power, and biomass power. The feed-in tariff costs are to be covered by the surcharge collected from customers. Purchase price of biomass energy sources in the FY2012 are as follows: 13.65 yen/kWh for biomass made from recycled wood, which often comes from construction projects,17.85 yen/kWh for solid sludge, 25.2 yen/kWh for whole timber biomass, 33.6 yen/kWh for biomass made from forest thinning, 40.95 yen/kWh for biogas that comes from sewage, and the purchase period was for 20 years. Purchase price and purchase period will be reviewed every year. Meanwhile, for the purpose of promoting renewable energy, system revisions and tax incentive programs are in place.

A Report on the Operation of the West Environmental Energy Center of Kanazawa City
-Mixed Incineration of Sewage Sludge-

Shingo TADOKORO*
(*Environmental Engineering Dept. Ⅱ)

(Abstract)

The West Environmental Energy Center of Kanazawa City (hereinafter called "the Center") was completed in March 2012. The Center has been engaged in the mixed incineration of sewage sludge since the start-up of the pre-existing facilities, and it has experienced various troubles relating to the sludge-conveying equipment, incinerators, and the sludge-feeding port of the feeding hopper. The newly constructed facilities have been designed on the basis of these experiences, and by incinerating stable dried sludge (with moisture content of 45%) mixed with waste at a low calorific power of about 10 MJ/kg, a more stable incineration system (according to the performance test, the incinerator is operated with the gas temperature at the incinerator outlet being about 920℃ on a daily average) has been established. In addition, as regards soot/dust and the concentration of NOX/SOX, which we were concerned about during the designing stage, no considerable difference was found in the comparative test between the case of mixed incineration of wastes with sewage sludge and that of single incineration of sludge.

Report of Operation of the Hitachinaka-Tokai Clean Center

Kohei BESSHI*
(*Environmental Engineering Dept. Ⅱ)

(Abstract)

The Hitachinaka-Tokai Clean Center was completed in April 2012. This facility generates electricity utilizing the waste heat from the incineration of waste. The electricity generated is being used in the facility to melt incineration ash in a plasma-type ash-melting furnace. During the planning of the facility, the operation plan and the capacity of the ash-melting furnace had been determined with a focus on reducing as much as possible the annual amount of electricity purchased. The plan had involved a reduction of the amount of electricity purchased to 15% of that required for continuous operation by operating the ash-melting furnace intermittently during periods of simultaneous operation of the two incinerators. It had been envisaged that this would increase the revenue from purchases and sales of electricity in the first 20 years by a factor of 2.9 taking into account the initial cost increase due to the capacity increase. We confirmed from the result of the actual operation of the facility that the facility was reducing the amount of purchased electricity as planned by operating the ash-melting furnace intermittently.

Renovation of the Hamamatsu City Nanbu Waste Incineration Plant

Masahiro OKAWA* and Naoki TADAKARA*
(*Environmental Engineering Dept. Ⅱ)

(Abstract)

The work to renovate the waste incineration plant had been started in June 2009 and completed in March 2012. The purpose of the renovation work had been to restore the functions of the waste incineration equipment that had deteriorated as a result of the many years of operation to make the equipment capable of continuing operating in a stable manner, and to enhance the capacity of the existing power generation equipment to increase the amount of electricity that can be sold to reduce the operating cost. During the renovation, the incinerators had been renovated one by one so that the waste incineration operation of the plant could be continued. We confirmed that the power generation equipment after the renovation was capable of continuing power generation operation at the rated output value in a stable manner.

Temporary Plant for Incinerating Disaster Wastes

Junichi KUMAGAI*, Akihiro MATSUMOTO*, Hideki TAKEGUCHI* and Norito UCHIYAMA*
(*Environmental Engineering Dept. Ⅰ)

(Abstract)

Disposing of the huge amounts of disaster wastes generated by the Great East Japan Earthquake and the tsunamis that followed is essential to allow the areas hit by the earthquake and tsunamis to be restored as quickly as possible. In this report, we will report mainly on the course of the design of the temporary incinerators in the Miyako area whose construction and operation was ordered to us by the Iwate Prefectural Government in September 2011 through a contract, and on the current status of the operation of the incinerators. The plant has two incinerators, each with a daily capacity of 47.5 tons, which makes the plant capable of incinerating 95 tons of wastes each day. The combustion appliance of the plant are fixed-bed water-cooled stokers. There had been many constraints including the short construction period and lack of information on the types, etc., of the disaster wastes, but we started operating the plant after the performance test conducted in March 2012 in which it was confirmed that the plant was capable of disposing of wastes as designed and satisfied the exhaust gas- and incineration ash-related numerical requirements.

Report of Operation of a Bagasse Fired Co-Generation Boiler Plant

Yuzuru NAKAE*, Masahide YAMASHITA* and Keiji MUKAI*
(*Energy Engineering Dept. Ⅰ)

(Abstract)

Sugar factories, which produce sugar from sugarcane, are utilizing the residue left after shredding sugarcane and squeezing it to extract the sugar content (the residue is hereinafter referred to as "bagasse") as boiler fuel and collecting and using the waste heat from the boilers to provide the heat and electricity required for the sugar production in the factories. Kumejima Sugar Co., Ltd., which is one of our customers, recently purchased a bagasse fired co-generation boiler from us to replace their existing aged boilers. They purchased the new boiler in order to automate the fuel feeding and ash removal work and improve the boiler efficiency so that they can have more surplus bagasse, which can be utilized as fertilizer. Through the performance test of the plant, it was confirmed that the plant was capable of providing heat and electricity as designed and of satisfying the numerical requirements of the exhaust gas emissions regulations. In addition, the plant is capable of operating the boiler with a high boiler efficiency of 85.6% through low-air ratio burning (the oxygen concentration in the exhaust gas was 5.1% (dry)), which has made it possible for the company to have more surplus bagasse than before the introduction of the new boiler.

A Report on the Commissioning of a Biomass Incineration Plant for a Paper Manufacturing Company

Keiji MUKAI*, Takayuki HATAGI*, and Kenji KATAOKA*
(*Energy Engineering Dept. Ⅰ)

(Abstract)

We have delivered a plant for the Tonegawa Factory of Rengo Co., Ltd., and this incinerates the waste from the paper manufacturing process at the Factory in a stoker-type incinerator and recovers thermal energy from the combustion exhaust gas by a natural circulation boiler. This plant is equipped with a bag filter and a wet gas-cleaning equipment of dispersed liquid type, which has functions such as filtration and desulfurization, in order to satisfy the strict exhaust gas standards. Additionally, this gives adequate consideration to the environment by such means as the design, which allows the generated combustion ash to be treated for regulating the particle size using crusher and vibrating screen for later active recycling. This document reports on the overview of the plant and the result of commissioning.

Step-Type Stoker Sludge Incineration System as a Measure for Reducing Greenhouse Gas Emissions

Naoki KABUTAN*
(*Sewerage Engineering Dept.)

(Abstract)

In recent years, reduction of greenhouse gas emissions has come to the fore as a challenge also for sewage plants, and 24% of the emissions are caused by N2O from sludge incineration facilities. "A Guide to the Development of Plans for the Promotion of Prevention of Global Warming in Sewage Systems," published by the Ministry of Land, Infrastructure, Transport and Tourism says that it is possible to reduce N2O emissions by 60% by increasing the combustion temperature in the sludge incinerator from 800℃ to 850℃. In this document, by comparing the report on the operation of the Step-Type Stoker Sludge Incineration System (hereinafter called "Stoker Incinerator"), which our company has delivered, and N2O emissions with those of other combustion methods, we will introduce the mechanical stoker-type incinerator as an effective incinerator for reducing greenhouse gas emissions.

Observation of Combustion Behavior in the Mechanical Stoker Incinerator

Hiroki YAMASAKI*, Munechika ITO*, Jun HAYASHI** and Fumiteru AKAMATSU**
(*Energy and Environmental Development Dept. Ⅰ, **Graduate School of Engineering Osaka University)

(Abstract)

For the purpose of understanding the combustion behavior in the mechanical stoker incinerator, we conducted a woodchip combustion test using an experimental small-scale stoker incinerator. We investigated the gas flow in the incinerator by numerical simulation and the flame structure using a high-speed camera, and measured the temperature by the Two Color Method as well as the radical chemiluminescence from the diffusion flame, all in the region of the secondary air injection. We observed from the images of the flame that, when the secondary air was injected, the flame surface area per unit volume increased, and the combustion reaction was promoted. In addition, in our temperature measurement using the Two Color Method, we could obtain highly responsive information on the temperature, and found the possibility of detecting the difference of combustion condition. On the other hand, we couldn't observe OH radical chemiluminescence from the diffusion flame in the incinerator.

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