濕法煙氣脫硫裝置目前應用多的是采用石灰石(或石灰)-石膏濕法脫硫工藝。以石灰石(或石灰)作吸收劑洗滌煙氣中的二氧化硫,生成亞硫酸鈣,再與加入的空氣進行氧化反應,后生成石膏, 脫除二氧化硫,凈化煙氣。整個反應過程均在吸收塔內完成,反應溫度一般為50℃左右。
The most commonly used wet flue gas desulfurization device currently uses the limestone (or lime) gypsum wet desulfurization process. Limestone (or lime) is used as absorbent to wash sulfur dioxide in flue gas to generate Calcium sulfite, and then oxidize with added air to generate gypsum, remove sulfur dioxide and purify flue gas. The entire reaction process is completed in the absorption tower, and the reaction temperature is generally around 50 ℃.
其主要工藝流程如下:鍋爐引風機出口的煙氣,由脫硫增壓風機升壓經煙氣換熱器(降溫側)降溫后進入吸收塔。當吸收塔采用立式噴霧塔時,吸收塔上部為吸收區,該區布置有噴淋層。吸收塔循環泵將石灰石漿液,亞硫酸鈣或石膏混合漿液送入噴咀霧化,霧化漿液自上而下通過吸收塔二氧化硫吸收區,與氣流接觸產生化學反應,生成亞硫酸鈣后流入吸收塔下部反應槽,由氧化風機鼓入空氣,亞硫酸鈣氧化成硫酸鈣-二水石膏。脫硫凈化后的煙氣經除霧器去除液滴后進入煙道,再由煙氣換熱器(升溫側)升溫后至煙囪排放。
The main process flow is as follows: The flue gas at the outlet of the boiler induced draft fan is pressurized by the desulfurization booster fan and cooled by the flue gas heat exchanger (cooling side) before entering the absorption tower. When the vertical spray tower is adopted for the absorption tower, the upper part of the absorption tower is the absorption area, which is arranged with a spray layer. The circulating pump of the absorption tower sends the limestone slurry, Calcium sulfite or gypsum mixed slurry to the nozzle for atomization. The atomized slurry passes through the sulfur dioxide absorption area of the absorption tower from top to bottom, contacts with the air flow to produce chemical reaction, generates Calcium sulfite, flows into the reaction tank at the lower part of the absorption tower, and is blown into the air by the oxidation fan. Calcium sulfite is oxidized into calcium sulfate gypsum dihydrate. The flue gas after desulfurization and purification enters the flue after removing droplets through the mist eliminator, and is then heated by the flue gas heat exchanger (heating side) before being discharged into the chimney.
由上述工藝流程可知,設置煙氣換熱器有2個作用。一是降低進入吸收塔的原煙氣溫度,滿足脫硫工藝的要求,其降溫的熱量用于加熱凈煙氣;二是(也是主要的)利用原煙氣的熱量加熱凈煙氣,提高排煙溫度(一般要求不低于80℃),減輕煙道和煙囪遭受低溫濕煙氣的腐蝕,同時使煙囪出口的煙氣有足夠的抬升高度,從而改善周圍大氣的環境質量。
From the above process flow, it can be seen that setting up a flue gas heat exchanger has two functions. One is to reduce the temperature of the raw flue gas entering the absorption tower to meet the requirements of the desulfurization process, and the cooling heat is used to heat the clean flue gas; The second (and most important) is to use the heat of the original flue gas to heat the clean flue gas, increase the exhaust temperature (generally not less than 80 ℃), reduce the corrosion of the flue and chimney from low-temperature wet flue gas, and at the same time, make the flue gas at the chimney outlet have sufficient lifting height, thereby improving the environmental quality of the surrounding atmosphere.
濕法煙氣脫硫裝置中換熱器的設置
Setting of heat exchangers in wet flue gas desulfurization devices
2.1 煙囪出口排煙溫度的選擇
2.1 Selection of smoke exhaust temperature at chimney outlet
煙氣脫硫裝置是否設置煙氣換熱器,主要取決于排煙溫度。當采用半干法、濕氨法、電子束干法或海水脫硫工藝時,吸收塔或反應器后的煙氣溫度亦在50～65℃,同樣存在是否需要設置煙氣換熱器,提高排煙溫度的問題。排煙溫度如何確定,不管從環保角度,還是煙囪結構設計方面考慮,我國目前還無標準規定。據了解,國外僅德國從煙氣擴散的角度出發,在有關的條例中規定煙囪出口的排煙溫度不小于72℃。近年來,國內引進國外技術和設備建設的濕法脫硫裝置,多數亦裝設了煙氣換熱器,出換熱器后進入煙囪的煙氣溫度不低于80℃,煙囪出口的排煙溫度接近72℃。
Whether a flue gas desulfurization device is equipped with a flue gas heat exchanger mainly depends on the exhaust temperature. When using semi dry method, wet ammonia method, electron beam dry method, or seawater desulfurization process, the flue gas temperature after the absorption tower or reactor is also between 50-65 ℃. There is also the issue of whether to install a flue gas heat exchanger to increase the exhaust gas temperature. There is currently no standard regulation in China on how to determine the exhaust temperature, whether from the perspective of environmental protection or the design of chimney structures. It is understood that only Germany, from the perspective of smoke diffusion, stipulates in relevant regulations that the exhaust temperature at the chimney outlet shall not be less than 72 ℃. In recent years, most wet flue gas desulfurization plants that have introduced foreign technology and equipment have also installed flue gas heat exchangers. The temperature of the flue gas entering the chimney after exiting the heat exchanger is not less than 80 ℃, and the exhaust temperature at the chimney outlet is close to 72 ℃.
2.2 國內、外煙氣脫硫裝置中煙氣換熱器的設置
2.2 Setting of flue gas heat exchangers in domestic and foreign flue gas desulfurization devices
根據已了解的情況和國外幾家著名的脫硫公司來華技術交流提供的資料,美國大部分火電廠的煙氣脫硫裝置中未設置煙氣換熱器,而日本、德國多數火電廠的煙氣脫硫裝置中設置了煙氣換熱器。如德國,盡管條例中規定煙囪出口的排煙溫度應不低于72℃,但也有少數電廠,煙氣脫硫裝置中未設煙氣換熱器,吸收塔出口的低溫濕煙氣由除霧器去除液滴后直接經電廠冷卻塔中央排放,或在吸收塔頂部設濕煙囪排放。
According to the known situation and information provided by several famous foreign desulfurization companies for technical exchange in China, most thermal power plants in the United States do not have flue gas heat exchangers installed in their flue gas desulfurization devices, while most thermal power plants in Japan and Germany have flue gas heat exchangers installed in their flue gas desulfurization devices. For example, in Germany, although regulations stipulate that the exhaust temperature at the chimney outlet should not be lower than 72 ℃, there are also a few power plants that do not have a flue gas heat exchanger in the flue gas desulfurization device. The low-temperature wet flue gas at the absorption tower outlet is directly discharged through the center of the power plant cooling tower after being removed by the mist eliminator, or a wet chimney is installed at the top of the absorption tower for discharge.
日本富士化學公司為我國漳州后石電廠提供的6套海水脫硫裝置,也沒有設置煙氣換熱器,吸收塔出口的低溫濕煙氣直接經240ｍ高的鋼制濕煙囪直接排放。在國內已建和在建的部分煙氣脫硫裝置中煙氣換熱器的設置情況來看,只有漳州后石電廠的6套海水脫硫裝置采用鋼制濕煙囪直接排放,還有一部分電廠采用部分煙氣脫硫后與未脫硫煙氣混合后排放,其余基本上設置了煙氣加熱器。
The six sets of seawater desulfurization devices provided by Fuji Chemical Company in Japan for the Houshi Power Plant in Zhangzhou, China, do not have flue gas heat exchangers. The low-temperature wet flue gas at the outlet of the absorption tower is directly discharged through a 240m high steel wet chimney. In terms of the installation of flue gas heat exchangers in some of the flue gas desulfurization devices that have been built or are under construction in China, only the six sets of seawater desulfurization devices in Zhangzhou Houshi Power Plant are directly discharged using steel wet chimneys. Some power plants also use partial flue gas desulfurization to mix with undesulfurized flue gas before discharge, while the rest are basically equipped with flue gas heaters.
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2023-06-25
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