本文選題：煤粉燃燒　切入點(diǎn)：細(xì)顆粒物排放　出處：《清華大學(xué)》2014年博士論文

【摘要】：和石油天然氣等化石燃料不同，煤炭特有的無(wú)機(jī)礦物質(zhì)成分使得其在燃燒氣化利用過(guò)程中面臨更多挑戰(zhàn)。如在煤粉燃燒過(guò)程中，部分無(wú)機(jī)礦物質(zhì)通過(guò)蒸發(fā)-凝結(jié)-團(tuán)聚等機(jī)制形成細(xì)顆粒物，污染大氣環(huán)境；其余絕大部分礦物質(zhì)成分通過(guò)破碎-熔融脫落-聚并等機(jī)制形成飛灰粗顆粒，在爐膛內(nèi)部和尾部煙道中沉積在對(duì)流換熱器管路表面，惡化傳熱特性進(jìn)而降低電廠效率。因此，研究煤粉燃燒過(guò)程中無(wú)機(jī)礦物質(zhì)的演化特性十分重要。本文基于這樣的背景研究了我國(guó)幾種典型動(dòng)力用煤燃燒過(guò)程中細(xì)顆粒物的生成、演化與沉積特性。 首先，通過(guò)高溫一維爐細(xì)顆粒物采樣試驗(yàn)研究了不同煤階煤種細(xì)顆粒物排放特性的差別。結(jié)果顯示低階高鈉準(zhǔn)東煤生成的超細(xì)顆粒數(shù)量明顯多于高階煙煤。進(jìn)一步的形貌和成分分析表明低階煤中富含的水溶態(tài)和離子可交換態(tài)礦物成分是亞微米顆粒的主要來(lái)源，而內(nèi)在礦物質(zhì)通過(guò)還原反應(yīng)形成的易揮發(fā)亞氧化物/金屬單質(zhì)是高階煙煤亞微米顆粒的主要來(lái)源。采用特征時(shí)間分析的方法探討了易揮發(fā)礦物蒸氣在爐內(nèi)的演化特性，其中礦物蒸氣均相成核/異相凝結(jié)作用貫穿爐內(nèi)燃燒全過(guò)程，而微米級(jí)顆粒間的碰撞-聚并作用概率很低。低階準(zhǔn)東煤燃燒過(guò)程中金屬蒸氣向顆粒表面異相沉積主要受擴(kuò)散機(jī)制控制，而高階神華煙則更多受到表面化學(xué)反應(yīng)的影響使得礦物蒸氣更容易在微米級(jí)顆粒表面沉積。 其次，本文基于一維爐積灰試驗(yàn)探討了積灰形成機(jī)理。試驗(yàn)結(jié)果表明準(zhǔn)東煤積灰傾向性明顯高于其它燃料，甚至高于草本生物質(zhì)燃料。微觀形貌觀察顯示準(zhǔn)東煤粘性積灰內(nèi)層生成量較多，而且很多飛灰粗顆粒表面沾有大量粘性細(xì)顆粒物，這些現(xiàn)象都表明準(zhǔn)東煤積灰具有較高的粘結(jié)特性。離散動(dòng)力學(xué)計(jì)算表明積灰內(nèi)層大大增加了飛灰粗顆粒與積灰管壁碰撞過(guò)程中的能量耗散，，進(jìn)而增強(qiáng)了積灰管的捕集效率。此外，輸運(yùn)理論定量計(jì)算顯示高鈉準(zhǔn)東煤的積灰內(nèi)層形成量比高階神華煙煤要多，因此準(zhǔn)東煤飛灰更容易被積灰管捕集形成更高的積灰傾向性。 最后，比較研究了富氧和常規(guī)兩種不同燃燒氣氛下細(xì)顆粒物排放特性和積灰特性的差異。一維爐試驗(yàn)結(jié)果表明真實(shí)煙氣循環(huán)富氧條件下?tīng)t內(nèi)細(xì)顆粒物濃度明顯高于常規(guī)燃燒，而理論計(jì)算顯示富氧條件下單位質(zhì)量灰分生成的亞微米顆粒反而略低于常規(guī)工況，因此煙氣循環(huán)攜帶的細(xì)顆粒物才是濃度增加的主要來(lái)源。此外高流速引起的高撞擊效率是常規(guī)條件下積灰速率高于富氧條件的主要原因。
[Abstract]:Unlike fossil fuels such as oil and natural gas, coal's unique inorganic minerals make it more challenging in the process of combustion and gasification, such as in pulverized coal combustion. Some inorganic minerals form fine particles by evaporation-condensation agglomeration, which pollute the atmospheric environment, and most of the other minerals form fly ash coarse particles through the mechanism of crushing, melting, shedding and coalescence. Deposition on the surface of the convective heat exchanger pipe in the furnace and the tail flue, which deteriorates the heat transfer characteristics and reduces the efficiency of the power plant. It is very important to study the evolution characteristics of inorganic minerals during pulverized coal combustion. Based on this background, the generation, evolution and deposition characteristics of fine particles in the combustion process of several typical power coal in China are studied in this paper. First, The difference of emission characteristics of fine particles from different rank coal was studied by sampling test of fine particles in one dimensional furnace at high temperature. The results showed that the quantity of ultrafine particles produced by low-rank high-sodium coal was obviously higher than that of high-order bituminous coal, and the further shape of coal was more than that of high-order bituminous coal. The analysis of appearance and composition shows that the water-soluble and ion-exchangeable mineral components in low-rank coal are the main sources of submicron particles. The main source of high-order bituminous coal submicron particles is the volatile oxide / metal single mass formed by the reduction reaction of internal minerals. The evolution characteristics of volatile mineral vapor in the furnace are discussed by the method of characteristic time analysis. Among them, the homogeneous nucleation / heterogeneous condensation of mineral vapor runs through the whole process of combustion in the furnace. However, the probability of collision-aggregation interaction between micron particles is very low. The heterogeneous deposition of metal vapor to particle surface is mainly controlled by diffusion mechanism. Higher order Shenhua smoke is more affected by surface chemical reaction, which makes mineral vapor deposit on micron particle surface more easily. Secondly, based on one-dimensional furnace ash deposition test, the formation mechanism of ash deposit is discussed, and the results show that the tendency of coal ash deposition in Jindong coal is obviously higher than that of other fuels. Even higher than herbaceous biomass fuel, the microscopic observation showed that the amount of cohesive ash deposits in the inner layer of Jindong coal was more, and many coarse particles of fly ash had a large amount of fine particles. All these phenomena indicate that the ash deposit of Jindong coal has a high bonding property. The discrete dynamic calculation shows that the inner layer of ash deposit greatly increases the energy dissipation during the collision between coarse particles of fly ash and the wall of ash deposit pipe. In addition, the transport theory quantitative calculation shows that the formation amount of ash deposit inner layer of high sodium Zhundong coal is more than that of high order Shenhua bituminous coal, so the fly ash of Jindong coal is easier to be captured by ash deposit tube to form a higher tendency of ash accumulation. Finally, the characteristics of fine particulate matter emission and ash deposition in oxygen-enriched and conventional combustion atmospheres are compared. The results of one-dimensional furnace test show that the concentration of fine particulate matter in the furnace is obviously higher than that in conventional combustion under the condition of real flue gas circulation and oxygen-enrichment. The theoretical calculation shows that the sub-micron particles produced by ash per unit mass under oxygen-enriched conditions are slightly lower than those under normal conditions. In addition, the high impact efficiency caused by high velocity of flow is the main reason that the ash deposition rate is higher than that under the condition of oxygen enrichment.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TM621.2

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