二氧化硫由于其對環(huán)境的破壞性和對人類健康的危害性，是當(dāng)今人類面臨的主要大氣污染物之一。工業(yè)用能和電力行業(yè)中的燃煤是產(chǎn)生SO2的主要的人為來源。目前我國二氧化硫排放量居世界首位，SO2污染已成為我國經(jīng)濟(jì)可持續(xù)發(fā)展的一個(gè)重要制約因素。我國目前的濕法煙氣脫硫技術(shù)基本由國外引進(jìn)，昂貴的投資和運(yùn)行費(fèi)用尚不能被國內(nèi)一般電廠和工業(yè)鍋爐所接受。研究和開發(fā)具有自主知識(shí)產(chǎn)權(quán)的新型煙氣脫硫技術(shù)是我國控制和解決SO2污染的重要手段。本文以此為目的在對典型濕法煙氣脫硫設(shè)備噴淋塔全面研究的基礎(chǔ)上，
Sulfur dioxide is one of the main air pollutants that human beings are facing today because of its damage to the environment and harm to human health. Industrial energy consumption and coal combustion in the power industry are the main anthropogenic sources of SO2 generation. At present, China's sulfur dioxide emissions rank first in the world, and SO2 pollution has become an important constraint factor for the sustainable development of China's economy. The current wet flue gas desulfurization technology in China is basically imported from abroad, and the expensive investment and operation costs cannot be accepted by the general domestic power plants and industrial boilers. Research and development of new flue gas desulfurization technology with independent intellectual property rights is an important means to control and solve SO2 pollution in China. Based on the comprehensive study of spray tower of typical wet flue gas desulfurization equipment,
提出的液幕式濕法煙氣脫硫技術(shù)從試驗(yàn)研究、理論建模和數(shù)值模擬等方面進(jìn)行了深入研究。首先，利用自行設(shè)計(jì)和搭建的噴嘴霧化測試系統(tǒng)對壓力式噴嘴的霧化特性進(jìn)行了詳細(xì)的試驗(yàn)研究。采用高速動(dòng)態(tài)攝像儀與扇形排狀量筒結(jié)合計(jì)算機(jī)圖像處理技術(shù)對液滴粒徑分布、徑向噴淋密度分布和霧化角等進(jìn)行了測量和數(shù)據(jù)處理，得到噴嘴的霧化壓力與霧化液滴粒徑、徑向噴淋密度分布及霧化角之間的關(guān)系。在此基礎(chǔ)上，試驗(yàn)分析了氣體動(dòng)力學(xué)參數(shù)、噴淋密度等因素對噴淋式吸收塔阻力特性的影響；以及煙氣流速、循環(huán)漿液量、液氣比、漿液pH值、煙氣入口SO2濃度和脫硫劑粒徑等因素對脫硫效率的影響。運(yùn)用兩相流運(yùn)動(dòng)學(xué)理論，建立了吸收塔內(nèi)單顆粒液滴的運(yùn)動(dòng)方程。
The proposed liquid curtain wet flue gas desulfurization technology has been deeply studied from experimental research, theoretical modeling and numerical simulation. First of all, the atomization characteristics of the pressure nozzle were studied in detail by using the self-designed and built nozzle atomization test system. The droplet size distribution, radial spray density distribution and atomization angle were measured and processed with high-speed dynamic camera and fan-shaped measuring cylinder combined with computer image processing technology. The relationship between atomization pressure of nozzle and droplet size, radial spray density distribution and atomization angle was obtained. On this basis, the effects of aerodynamic parameters, spray density and other factors on the resistance characteristics of spray absorption tower were analyzed experimentally; The effects of flue gas flow rate, circulating slurry volume, liquid-gas ratio, slurry pH value, SO2 concentration at flue gas inlet and particle size of desulfurizer on desulfurization efficiency are also discussed. Based on the kinematics theory of two-phase flow, the motion equation of a single droplet in the absorber is established.
通過理論分析和計(jì)算得到了臨界霧化粒徑與煙氣流速的關(guān)系以及液滴在塔內(nèi)停留時(shí)間與粒徑、煙氣流速的關(guān)系。建立了吸收塔氣側(cè)阻力計(jì)算模型，計(jì)算表明離散相阻力是吸收段氣相阻力的主要阻力，計(jì)算與試驗(yàn)數(shù)據(jù)吻合較好。得到該裝置的工況運(yùn)行參數(shù)。其次，分別對順流/逆流液幕塔內(nèi)氣液兩相流動(dòng)、傳熱和脫硫特性進(jìn)行了全面試驗(yàn)研究和理論分析。得到液幕床層高度與液體噴射速度、煙氣流速、噴嘴直徑的關(guān)系，提出順流/逆流吸收塔壓降與液氣比、煙氣流速的關(guān)聯(lián)式和液幕床床層高度的計(jì)算公式 。根據(jù)液幕床吸收塔內(nèi)氣液兩相溫度分布的規(guī)律，首次提出液幕塔內(nèi)氣液平均傳熱系數(shù)的計(jì)算公式和順、逆流塔內(nèi)氣液兩相傳熱傳質(zhì)的幾何參數(shù)范圍。
Through theoretical analysis and calculation, the relationship between critical atomization particle size and flue gas flow rate, and the relationship between droplet residence time in the tower and particle size and flue gas flow rate were obtained. The calculation model of the gas side resistance of the absorption tower is established. The calculation shows that the discrete phase resistance is the main resistance of the gas phase resistance in the absorption section, and the calculation is in good agreement with the test data. The operating parameters of the device are obtained. Secondly, the gas-liquid two-phase flow, heat transfer and desulfurization characteristics in the co-flow/counterflow liquid curtain tower were comprehensively studied and theoretically analyzed. The relationship between the height of liquid curtain bed and liquid injection velocity, flue gas velocity and nozzle diameter is obtained. The correlation formula between the pressure drop of downstream/countercurrent absorption tower and the liquid-gas ratio, flue gas velocity and the calculation formula for the height of liquid curtain bed are proposed. According to the law of gas-liquid two-phase temperature distribution in the liquid curtain absorption tower, the calculation formula of gas-liquid average heat transfer coefficient in the liquid curtain tower and the geometric parameter range of gas-liquid two-phase heat and mass transfer in the forward and reverse flow tower are proposed for the first time.
總結(jié)歸納發(fā)現(xiàn)，在試驗(yàn)參數(shù)范圍內(nèi)，提高煙氣流速或增大噴液量均能有效提高脫硫效率，噴液量對脫硫效率的影響較煙氣流速的影響大。得到順流/逆流塔的較佳運(yùn)行工況點(diǎn)：在順流塔煙氣流速為6.44m/s，循環(huán)漿液量為27m3/h（液氣比為14L/m3），氧化漿池pH值為5.6～5.8，脫硫效率為93.7%；逆流塔煙氣流速為2.31m/s，循環(huán)漿液量為54m3/h（液氣比為27.5L/m3），氧化漿池pH值5.6～5.8時(shí)可使脫硫效率達(dá)到96.8%。采用鏡像分析和熱重分析方法對脫硫產(chǎn)物的物理結(jié)構(gòu)和成分分析結(jié)果表明，脫硫產(chǎn)物中石膏含量較高，但由于設(shè)備氧化工藝等問題，中間產(chǎn)物含量偏高，改進(jìn)氧化系統(tǒng)增強(qiáng)氧化效果可得到滿足工業(yè)和民用的石膏。針對液幕塔的氣液傳質(zhì)特點(diǎn)，采用表面更新理論建立了塔內(nèi)SO2吸收過程的物理和數(shù)學(xué)模型。
It is concluded that within the range of test parameters, increasing the flue gas flow rate or increasing the liquid injection volume can effectively improve the desulfurization efficiency, and the effect of liquid injection volume on the desulfurization efficiency is greater than that of the flue gas flow rate. The better operating conditions of the downstream/countercurrent tower are obtained: the flue gas flow rate of the downstream tower is 6.44m/s, the circulating slurry volume is 27m3/h (the liquid-gas ratio is 14L/m3), the pH value of the oxidation slurry tank is 5.6~5.8, and the desulfurization efficiency is 93.7%; The flue gas flow rate of the countercurrent tower is 2.31m/s, the circulating slurry volume is 54m3/h (liquid-gas ratio is 27.5L/m3), and the desulfurization efficiency can reach 96.8% when the pH value of the oxidation slurry tank is 5.6~5.8. The physical structure and composition of desulfurization products are analyzed by image analysis and thermogravimetric analysis. The results show that the content of gypsum in desulfurization products is high, but the content of intermediate products is high due to equipment oxidation process and other problems. Improving oxidation system to enhance oxidation effect can meet the requirements of industrial and civil gypsum. According to the characteristics of gas-liquid mass transfer in the liquid curtain tower, the physical and mathematical models of SO2 absorption process in the tower were established using the surface renewal theory.
該模型全面考慮了漿液中各種離子以及各種有限速率的反應(yīng)，同時(shí)考慮了氣相傳質(zhì)阻力、液相傳質(zhì)阻力和石灰石溶解阻力的影響。通過模型分析確定了濕法煙氣脫硫工藝中吸收段和氧化段的反應(yīng)機(jī)理。模型計(jì)算得到了逆流式液幕塔的脫硫效率與煙氣流速和液氣比的關(guān)系、煙氣中SO2濃度隨吸收塔高度的變化曲線和循環(huán)漿液pH值隨高度的變化規(guī)律。對塔內(nèi)各段SO2的吸收速率進(jìn)行了分析，發(fā)現(xiàn)液柱上升段對SO2吸收較少，液滴下落階段是SO2吸收的主要階段。逆流式液幕床層底端SO2的吸收為液相傳質(zhì)阻力控制。計(jì)算結(jié)果與試驗(yàn)結(jié)果吻合較好，基本上反映了反應(yīng)塔內(nèi)的實(shí)際過程。
The model considers all kinds of ions in the slurry and all kinds of finite rate reactions, as well as the effects of gas phase mass transfer resistance, liquid phase mass transfer resistance and limestone dissolution resistance. The reaction mechanism of the absorption section and the oxidation section in the wet flue gas desulfurization process was determined by model analysis. The relationship between desulfurization efficiency of countercurrent liquid curtain tower and flue gas flow rate and liquid-gas ratio, the variation curve of SO2 concentration in flue gas with the height of absorption tower and the variation law of pH value of circulating slurry with the height were obtained by model calculation. The absorption rate of SO2 in each section of the tower was analyzed. It was found that the rising section of the liquid column absorbed less SO2, and the falling phase of the liquid drop was the main phase of SO2 absorption. The absorption of SO2 at the bottom of the countercurrent liquid curtain bed is controlled by the resistance of liquid phase mass transfer. The calculated results are in good agreement with the test results, and basically reflect the actual process in the reactor.
采用GAMBIT軟件構(gòu)造三維網(wǎng)格模型，運(yùn)用Fluent 6.0軟件對液幕塔內(nèi)氣液兩相流動(dòng)和傳熱過程進(jìn)行了數(shù)值模擬。采用離散相模型，考慮兩相間的相互作用，在歐拉坐標(biāo)系下采用RNG k-ε模型來描述氣相湍流，在拉格朗日坐標(biāo)系下對液滴顆粒相進(jìn)行描述，建立液幕塔內(nèi)氣液流動(dòng)和傳熱的三維數(shù)學(xué)模型。
GAMBIT software was used to construct a three-dimensional mesh model, and fluent 6.0 software was used to simulate the gas-liquid two-phase flow and heat transfer process in the liquid curtain tower. The discrete phase model is adopted, and the interaction between two phases is considered. RNG k is adopted in Euler coordinate system- ε The model is used to describe the gas phase turbulence, describe the droplet particle phase in the Lagrange coordinate system, and establish a three-dimensional mathematical model of gas-liquid flow and heat transfer in the liquid curtain tower.
數(shù)值模擬了不同液氣比時(shí)塔內(nèi)氣液流動(dòng)和傳熱狀況，計(jì)算與試驗(yàn)結(jié)果吻合較好。表明所建立的模型和采用的算法具有良好的預(yù)測性和可靠性。針對逆流塔內(nèi)煙氣偏流現(xiàn)象進(jìn)行了流場優(yōu)化設(shè)計(jì)，計(jì)算表明當(dāng)煙氣入口通道與塔體連接處夾角為圓角時(shí)，塔內(nèi)氣液流場分布均勻性較好。
The gas-liquid flow and heat transfer in the tower at different liquid-gas ratios were numerically simulated, and the calculated results were in good agreement with the experimental results. It shows that the model and the algorithm have good predictability and reliability. The flow field optimization design is carried out for the phenomenon of flue gas deflection in the countercurrent tower. The calculation shows that when the angle between the flue gas inlet channel and the tower body is a fillet, the gas-liquid flow field in the tower is well distributed.
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2023-01-18
