成果報告書詳細
管理番号20100000001309
タイトル*平成21年度中間年報 戦略的石炭ガス化・燃焼技術開発(STEP CCT)石炭利用プロセスにおける微量成分の環境への影響低減手法の開発 高度除去技術(H19-H22)
公開日2010/10/21
報告書年度2009 - 2009
委託先名バブコック日立株式会社
プロジェクト番号P07021
部署名クリーンコール開発推進部
和文要約和文要約等以下本編抜粋:1.研究開発の内容及び成果等(1)目的 石炭は,世界的に埋蔵量が豊富であり,埋蔵地も偏りが少ないことから今後とも重要な燃料であると考えられる。石炭を燃料とする石炭焚火力発電所では,システムの高効率化と同時に環境負荷を低減するための技術開発が進められてきた。例えば,石炭焚ボイラから発生する排ガス中には,光化学スモッグや酸性雨の原因となる窒素酸化物(NOx)や硫黄酸化物(SOx)が含まれており,これらを除去するために高性能な脱硝装置や脱硫装置を開発してきた。
英文要約Development of methods to reduce environmental impact of trace elements resulting from coal utilization- Advanced removal technology of trace elements for pulverized coal-fired boilers
(1) Background and Purpose Impacts of trace elements derived from coal on environment have been shown in recent years.
It has been reported that trace elements such as mercury exhausted from coal-fired power plants are harmful for human through food chains especially in North America using low quality coals.
Therefore regulations for the emissions are becoming severer year after year.
In this study we are going to make clear the mercury behaviors in flue gas treatment systems for coal-fired plants, and develop methods to prevent its discharge into the atmosphere so as to correspond the regulations. The target of mercury emission level is 3μg/kWh, which is the most severe regulation value in the world and proposed in CANADA-WIDE STANDARDS.
(2) Approach
First, we obtained fundamental data of mercury behaviors i.e. oxidation in flue gas, adsorption on fly ash and absorption in desulfurization absorbent by laboratory scale tests using simulated
gas in 2007 fiscal year. Next, based on the laboratory results, we determined mercury speciation and evaluated removal properties in each gas treatment device using actual exhausts of existing
bench scale test furnace (coal feed rate: 40kg/h) and flue gas treatment apparatus in 2008 fiscal year. Subsequently, in 2009 fiscal year, we have obtained necessary data by an existing pilot scale test plant (coal feed rate: 100 - 120 kg/h) to define operating conditions of each device and
design commercial plants.
(3) Results
In 2009 fiscal year, based on the laboratory results obtained in 2007 and the bench scale test results obtained in 2008, required configuration and operating conditions of the system were determined so as to achieve the target emission level. Then the following studies were conducted
with actual coal-fired flue gas by the pilot scale test plant.
a) Test coals
Two Canadian coals, Quinsam and Coal Valley, were tested.
One Chinese coal from Shanxi province was imported for the future tests. 
b) Mercury oxidation properties
Mercury oxidation properties across the DeNOx catalyst and the influences of gas composition were evaluated. In the catalyst reactor most mercury converted into oxidized form, which was easy to remove from flue gas by the downstream devices. Mercury oxidation was improved with increasing chlorine content in coal, and the mercury removal was increased with the mercury oxidation rate.
c) Mercury removal across dry electrostatic precipitator (DESP)
Effects of DESP operating temperature and mercury oxidation on mercury removal efficiency across the DESP were evaluated. DESP could not remove elemental mercury from the flue gas, because elemental mercury was hardly adsorbed on fly ash. On the other hand, decreasing DESP temperature from 160℃ to 90℃ increased the adsorption of oxidized mercury on fly ash, and it was effective for high efficiency mercury removal.
d) Mercury removal in wet flue gas desulfurization (WFGD)
Influence of liquid/gas ratio (L/G) on mercury removal in WFGD was evaluated. Little elemental mercury dissolved in the absorbing solution. In contrary, oxidized mercury had high solubility and the removal efficiencies across WFGD were more than 90%. L/G had little influences on mercury removal as far as in the operation range of actual plants.
Increasing of mercury concentration in the absorbing solution caused decreasing of mercury removal because of elemental mercury re-emission from the solution.
e) Studies under oxy-fuel combustion condition
Characteristics of mercury oxidation by DeNOx catalyst, adsorption on fly ash and absorption in desulfurizaion absorbent under oxy-fuel combustion conditions were studied by retrofitting the pilot scale test plant into an oxy-fuel system.
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