本文選題：煤分級利用 + 激光燃燒診斷　； 參考：《浙江大學》2017年博士論文

【摘要】：在煤及生物質燃料的利用過程中,為了實現高效低污染,對燃料的分級轉化利用成了 一個重要手段。其中,煤及生物質的氣化利用是分級轉化利用的重要環(huán)節(jié)之一。通過氣化過程產生的煤氣,可以直接用于燃氣輪機進行高效低污染燃燒發(fā)電,還可以用作眾多化工生產的原材料。但是在分級轉化的氣化工藝中,會出現來源不同的煤及生物質原料。這些燃料的特性差異,加上氣化工藝本身的不同,氣化煤氣的組份存在著較大的不確定性。煤氣的主要組份包括氫氣,一氧化碳,甲烷,氮氣和二氧化碳等。其中作為重要的可燃組份,氫氣的燃燒特性和通常使用的天然氣有著很大的區(qū)別。加上大量的不可燃組份,比如氮氣和二氧化碳,造成燃料熱值較低,這都會給煤氣的高效低污染燃燒利用造成很大的挑戰(zhàn)。所以了解含有不同組份的煤氣的燃燒特性,開發(fā)合理的穩(wěn)定燃燒手段成了重要的研究課題。另外,在不少煤和生物質的氣化燃燒過程中,會釋放出大量的堿金屬元素,這不僅僅會造成爐膛的結渣腐蝕,還會極大地影響煤氣的品質。含堿金屬的煤氣,往往會造成燃氣輪機葉片的腐蝕。所以,對于氣化燃燒過程中,堿金屬的釋放規(guī)律的研究,以及探索實用的堿金屬監(jiān)測手段成為重要的研究內容。本文主要通過不同先進激光診斷技術對以上課題中的關鍵問題展開了相應的研究。本文首先是對含有不同組份的煤氣的層流火焰速度進行了精確的測量。層流火焰速度是燃料燃燒反應的重要特性之一,可廣泛用于燃燒機理的驗證和發(fā)展。本文使用的層流火焰速度測量方法包括熱流量爐法和基于激光誘導OH熒光(OH-PLIF)技術的本生燈法。通過不同比例的氫氣和一氧化碳來模擬實際煤氣的可燃組份,通過不同比例的氮氣和二氧化碳來模擬實際煤氣中稀釋氣體的比例。氫氣在可燃組份中的比例從5%變化到75%,稀釋氣體比例從0%變化到50%。這些組份比例的大范圍變化基本涵蓋了不同類型的煤氣。通過實驗結果可以看出,煤氣的層流火焰速度隨當量比的變化趨勢和甲烷等碳氫燃料有著很大的不同。煤氣層流火焰速度峰值往往位于比較燃料富燃的區(qū)域,而不是通常的當量比1的附近。氫氣量的增加可以極大地提高層流火焰速度,稀釋度的增加可以明顯減小層流火焰速度。通過對煤氣燃燒機理的模擬分析發(fā)現,這些燃燒特性很大程度上都是受到燃燒過程中生成的H自由基的控制。本文總結了不同煤氣的層流火焰速度和其燃燒反應區(qū)的H自由基濃度峰值之間的線性變化關系。通過總結實驗獲得的大量層流火焰速度,還總結出了用于估算不同煤氣層流火焰速度的經驗公式。另外,本文還通過OH-PLIF技術研究了不同煤氣在較低湍流狀態(tài)下,即皺褶區(qū)的火焰的燃燒特性。通過含有中心射流孔的平面火焰爐,生成了不同煤氣在不同出口雷諾數下的預混射流火焰。這些火焰主要是在預混湍流火焰的起皺火焰區(qū)域和皺褶火焰區(qū)域�；鹧娴腛H-PLIF瞬態(tài)圖展示了不同工況下火焰的前鋒面結構。本文分析計算了不同煤氣在不同出口雷諾數下的湍流火焰速度。和對應的層流火焰速度相比較,湍流火焰速度隨氫氣比例以及稀釋度的變化具有非常類似的趨勢。較高的氫氣比例造成較高的湍流火焰速度,較高的OH濃度以及較小的火焰尺寸。稀釋度具有相反的效果。出口雷諾數的增加同樣可以增加湍流火焰速度和OH濃度。通過對實驗獲得的湍流火焰速度和對應煤氣的層流火焰速度的比值的分析發(fā)現,對于起皺區(qū)和皺褶區(qū)的火焰,湍流度對湍流燃燒的影響規(guī)律不因煤氣組分的不同而變化。另外,還通過OH-PLIF技術和甲醛-PLIF技術研究了氮氣稀釋和二氧化碳稀釋對低湍流度湍流火焰的影響。同樣,稀釋度的增加,極大地降低了 OH和甲醛的濃度,延遲了火焰的燃燒。對于相同湍流度下的火焰,稀釋對火焰鋒面局部結構的影響并不明顯,但是會增加整體皺褶率。比較二氧化碳稀釋氣體和氮氣稀釋氣體,區(qū)別比較大的是燃燒區(qū)的OH濃度。而對于未燃區(qū)的甲醛濃度,受不同稀釋氣體的影響較小。進一步,為了探討先進的穩(wěn)定燃燒手段,本文主要針對等離子體強化燃燒手段,研究了等離子體中的重要組分,即臭氧的強化燃燒特性。研究了臭氧強化燃燒的機理。本文通過甲醛-PLIF技術對臭氧強化甲烷/空氣預混燃燒過程中甲醛生成的影響進行了研究。研究發(fā)現,臭氧的加入可以極大地促進火焰中甲醛的生成。在加入4500ppm的臭氧,對于當量比為1.4的甲烷空氣預混火焰,反應區(qū)甲醛的濃度提高了 50%以上。實驗獲得了在不同當量比下甲醛的增加率。通過實驗數據和機理模擬結果的對照,驗證了包含臭氧反應子機理的燃燒反應機理的可靠性。臭氧的加入,不僅僅增加了甲醛的濃度,而且明顯提前了甲醛的生成時間。通過對甲醛的研究,可以看出,臭氧對于燃燒的促進作用主要發(fā)生在燃燒的預熱區(qū)。最后,通過可調諧半導體激光吸收光譜(TDLAS)技術實現了對煤及生物質氣化燃燒過程中鉀原子濃度的定量測量,用于了解煤和生物質氣化過程中堿金屬的釋放規(guī)律。比較不同的固體燃料,發(fā)現燃料本身的特性對堿金屬的釋放特性具有很大的影響。煤炭里面較多的固定碳使得其鉀的釋放主要發(fā)生在焦炭燃燒階段。生物質較多的揮發(fā)份以及大量的水溶性堿金屬,使其鉀的釋放主要發(fā)生在揮發(fā)份燃燒階段。另外還比較了燃料在燃燒和氣化過程中鉀的不同釋放特性。氣化過程削弱了揮發(fā)分和焦炭的消耗反應,使得整個鉀釋放過程有所變弱。
[Abstract]:In the use of coal and biomass fuel, in order to achieve high efficiency and low pollution, the classification and utilization of fuel has become an important means. The gasification utilization of coal and biomass is one of the important links in the conversion and utilization of coal and biomass. The gas produced by the gasification process can be directly used for high efficiency and low pollution combustion of gas turbine. Power generation can also be used as a raw material for many chemical production. However, in the gasification process of classified conversion, there will be different sources of coal and biomass. The characteristics of these fuels, as well as the different gasification processes, have a large uncertainty in the composition of the gasification gas. The main components of the gas include hydrogen, carbon monoxide. Methane, nitrogen and carbon dioxide, etc. as important combustible components, there is a great difference between the combustion characteristics of hydrogen and the natural gas used. A large number of non combustible components, such as nitrogen and carbon dioxide, cause a low fuel heat value, which will cause a great challenge to the efficient and low pollution combustion of the gas. It is an important research topic to understand the combustion characteristics of gas containing different components and to develop a reasonable means of stable combustion. In addition, a large number of alkali metal elements will be released during the gasification and combustion process of coal and biomass, which will not only cause the slag corrosion in the furnace, but also greatly influence the quality of the gas. Gas is often caused by corrosion of gas turbine blades. Therefore, the research on the release law of alkali metals and the exploration of practical alkali metal monitoring methods have become an important research content in the process of gasification and combustion. This paper mainly studies the key problems in the above topics through different advanced laser diagnostic techniques. The first is the accurate measurement of the laminar flame velocity of the gas with different components. The laminar flame velocity is one of the most important characteristics of the fuel combustion reaction. It can be widely used in the verification and development of the combustion mechanism. The laminar flame velocity measurement methods used in this paper include the heat flux furnace method and the laser induced OH fluorescence (OH-PLIF). This method is used to simulate the combustible components of the actual gas by different proportions of hydrogen and carbon monoxide. The proportion of the diluted gas in the actual gas is simulated by different ratios of nitrogen and carbon dioxide. The proportion of hydrogen in the combustible component varies from 5% to 75%, and the proportion of the diluted gas body from 0% to 50%.. The gas laminar flame velocity varies greatly with the methane and other hydrocarbon fuels. The peak velocity of the gas laminar flow flame is often located in the area where the fuel is relatively rich, not the usual equivalent ratio of 1. Increasing the velocity of laminar flame can greatly increase the velocity of laminar flame, and the velocity of laminar flame can be reduced obviously. Through the simulation analysis of the gas combustion mechanism, it is found that these combustion characteristics are largely controlled by the H free radicals generated during the combustion process. The linear relationship between the peak value of the H free radical concentration in the combustion zone is linear. By summing up a large amount of laminar flame velocity obtained by the experiment, an empirical formula for estimating the velocity of different gas laminar flow flame is also summarized. In addition, this paper also studies the flame of different gas in the lower turbulent state, that is the wrinkle zone through the OH-PLIF technology. Combustion characteristics. Through a plane flame furnace containing a central jet hole, the premixed jet flame of different gas is generated at the Reynolds number at different outlet. The flame is mainly in the wrinkle flame area and the fold flame area of the premixed turbulent flame. The flame's OH-PLIF transient diagram shows the front surface structure of the flame under different working conditions. The turbulent flame velocity of different gas in different outlet Reynolds number is calculated and calculated. Compared with the corresponding laminar flame velocity, the turbulent flame velocity has a very similar trend with the change of hydrogen ratio and dilution degree. Higher hydrogen ratio causes higher turbulent flame velocity, higher OH concentration and smaller flame size. The increase of the dilution has the opposite effect. The increase of the exportation Reynolds number can also increase the turbulent flame velocity and the OH concentration. The analysis of the turbulent flame velocity and the ratio of the laminar flame velocity to the gas is found that the turbulence intensity affects the turbulent combustion in the wrinkling and wrinkle zone. In addition, the effects of nitrogen dilution and carbon dioxide dilution on low turbulence turbulence flame were studied by OH-PLIF and formaldehyde -PLIF technology. Similarly, the increase of the dilution degree greatly reduced the concentration of OH and formaldehyde and delayed the combustion of flame. The influence of the structure is not obvious, but it will increase the overall wrinkle rate. Comparing the carbon dioxide dilution gas and the nitrogen diluent gas, the difference is much larger than the OH concentration in the combustion zone. However, the concentration of the formaldehyde in the unburned area is less affected by the different dilution gases. The important components in the plasma are studied. The characteristics of the enhanced combustion of the ozone are studied. The mechanism of the enhanced combustion of ozone is studied. The effect of the formaldehyde -PLIF technology on the formation of formaldehyde in the pre mixed combustion of methane / air is studied in this paper. The study shows that the addition of ozone can greatly promote the formation of the ozone. Formaldehyde is generated in the flame. The concentration of formaldehyde in the reaction zone is increased by more than 50% in the pre mixed methane air premixed flame with the equivalent ratio of 1.4. The increase rate of formaldehyde under the different equivalent ratio is obtained. The combustion reaction containing the ozone reaction mechanism is verified by the comparison of the experimental data and the simulation results of the mechanism. The addition of ozone does not only increase the concentration of formaldehyde, but also obviously advance the formation time of formaldehyde. Through the study of formaldehyde, it can be seen that the promoting effect of ozone on combustion mainly occurs in the preheated area of combustion. Finally, the coal is realized by the tunable semi conductor laser absorption spectroscopy (TDLAS) technology. The quantitative measurement of the concentration of potassium in the combustion process of biomass gasification is used to understand the release of alkali metals in coal and biomass gasification. The characteristics of different solid fuels have been compared and the characteristics of the fuel itself have a great influence on the release characteristics of alkali metals. The more fixed carbon inside coal makes the release of potassium mainly occurring. In the combustion stage of coke. The volatilization of biomass and a large amount of water-soluble alkali metals, the release of potassium is mainly in the stage of volatile combustion. In addition, the different release characteristics of potassium in the combustion and gasification process are compared. The gasification process weakens the reaction of the volatile and coke consumption, making the whole potassium release process available. It's weak.

【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TQ534

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