本文關(guān)鍵詞：高粘度范圍內(nèi)灰的沉積及粘結(jié)特性的實(shí)驗(yàn)研究　出處：《清華大學(xué)》2014年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 高粘度 灰沉積 燒結(jié) 脖頸抗拉強(qiáng)度 計(jì)算公式

【摘要】：灰沉積一直是影響電站鍋爐正常運(yùn)行的難題之一，，嚴(yán)重威脅著鍋爐的安全、經(jīng)濟(jì)運(yùn)行。本文以高粘度范圍內(nèi)（灰的溫度低于其臨界溫度時(shí)的粘度范圍）灰的沉積和粘結(jié)特性作為研究對(duì)象，采用實(shí)驗(yàn)測試與理論分析方法開展了灰的沉積特性及其影響規(guī)律、粘結(jié)機(jī)理與模型的研究，對(duì)于深入認(rèn)識(shí)高粘度范圍內(nèi)灰的沉積過程具有重要的理論和實(shí)際意義。 本文首先從高粘度范圍內(nèi)灰的沉積特性著手，在灰沉積特性測試實(shí)驗(yàn)裝置上開展了換熱面溫度、灰顆粒撞擊速度、沉積時(shí)間、灰的粒徑以及灰的化學(xué)成分對(duì)高粘度范圍內(nèi)灰沉積行為的影響規(guī)律研究。實(shí)驗(yàn)結(jié)果表明，高粘度范圍內(nèi)的灰顆粒具有較強(qiáng)的沉積傾向，其沉積過程可以分為兩個(gè)階段：在初始階段發(fā)生的為積灰過程，隨著沉積物的生長逐步轉(zhuǎn)變?yōu)榻Y(jié)渣現(xiàn)象。較低的換熱面溫度、較大的灰顆粒速度和較大的粒徑能夠顯著抑制灰的沉積過程。堿金屬和堿土金屬含量較高的灰顆粒在高粘度范圍內(nèi)具有較強(qiáng)的沉積傾向�；业幕瘜W(xué)成分及其所處的環(huán)境條件是影響高粘度范圍內(nèi)灰沉積行為的兩個(gè)關(guān)鍵因素。 然后，開展了灰的化學(xué)成分與燒結(jié)特之間關(guān)系的規(guī)律與模型研究。通過將生物質(zhì)與兗礦煙煤進(jìn)行混燃，改變了燃料中灰的化學(xué)成分，在沉降爐和燒結(jié)溫度測量實(shí)驗(yàn)裝置上開展了灰的成分變化對(duì)于燒結(jié)特性的影響規(guī)律研究。實(shí)驗(yàn)結(jié)果表明，生物質(zhì)灰中的堿金屬含量較高，導(dǎo)致燒結(jié)溫度遠(yuǎn)低于煤灰，且混合燃料灰的燒結(jié)溫度隨著生物質(zhì)含量的升高而降低�；业臒Y(jié)溫度隨堿酸比的增大而減小，提出了基于灰的化學(xué)成分的燒結(jié)溫度計(jì)算模型，計(jì)算結(jié)果與實(shí)驗(yàn)值符合良好。 最后，從粘結(jié)機(jī)理著手，針對(duì)固體橋力主導(dǎo)的高粘度范圍內(nèi)灰的粘結(jié)過程進(jìn)行了研究。開發(fā)了高溫條件下灰的固體橋力及抗拉強(qiáng)度的測量實(shí)驗(yàn)系統(tǒng)，獲得了溫度、接觸時(shí)間和接觸壓力對(duì)于高粘度范圍內(nèi)灰的脖頸抗拉強(qiáng)度的影響規(guī)律，發(fā)現(xiàn)了灰的脖頸抗拉強(qiáng)度與溫度之間呈現(xiàn)雙峰分布曲線的關(guān)系，高粘度范圍內(nèi)灰的脖頸抗拉強(qiáng)度遠(yuǎn)小于同溫度下的材料抗拉強(qiáng)度。通過對(duì)實(shí)驗(yàn)結(jié)果進(jìn)行無量綱化處理，提出了高粘度范圍內(nèi)灰的無量綱脖頸抗拉強(qiáng)度計(jì)算公式，并對(duì)該公式進(jìn)行了驗(yàn)證，計(jì)算值與實(shí)驗(yàn)值符合較好。該計(jì)算公式為建立以灰顆粒受力分析為基礎(chǔ)的高粘度范圍內(nèi)灰的沉積模型奠定了基礎(chǔ)。
[Abstract]:Ash deposition has always been one of the difficult problems affecting the normal operation of power plant boilers, which seriously threatens the safety of boilers. Economic operation. In this paper, the deposition and bonding characteristics of ash in high viscosity range (when the temperature of ash is lower than its critical temperature) are studied. The deposition characteristics of ash and its influence law, bonding mechanism and model were studied by means of experimental test and theoretical analysis. It has important theoretical and practical significance for further understanding the deposition process of ash in high viscosity range. In this paper, the heat transfer surface temperature, ash particle impact velocity and deposition time are carried out on the test device of ash deposition characteristics from the point of view of the ash deposition characteristics in the high viscosity range. The influence of particle size and chemical composition of ash on the ash deposition behavior in high viscosity range is studied. The experimental results show that the ash particles in high viscosity range have a strong deposition tendency. The deposition process can be divided into two stages: in the initial stage, ash deposition process, with the sediment growth gradually changed to slagging phenomenon, lower heat transfer surface temperature. Larger ash particle velocity and larger particle size can significantly inhibit the ash deposition process. The ash particles with higher alkali metal and alkali earth metal content have a strong tendency to deposit in the high viscosity range. The chemical composition of ash and its location. Environmental conditions are two key factors affecting ash deposition behavior in high viscosity range. Then, the relationship between ash chemical composition and sintering characteristics was studied. By mixing biomass with Yankuang bituminous coal, the chemical composition of ash in fuel was changed. The influence of ash composition change on sintering characteristics was studied in the settling furnace and sintering temperature measuring device. The experimental results showed that the alkali metal content in biomass ash was higher than that in biomass ash. The sintering temperature is much lower than coal ash, and the sintering temperature of mixed fuel ash decreases with the increase of biomass content, while the sintering temperature of ash decreases with the increase of alkali-acid ratio. The calculation model of sintering temperature based on the chemical composition of ash is presented. The calculated results are in good agreement with the experimental values. Finally, the bond process of ash in the high viscosity range dominated by solid bridge force is studied from the point of view of bonding mechanism, and an experimental system for measuring the solid bridge force and tensile strength of ash under high temperature is developed. The effects of temperature, contact time and contact pressure on the tensile strength of the neck of ash in the high viscosity range were obtained, and the relationship between the tensile strength of the neck and the temperature was found. The tensile strength of the neck of the ash in the high viscosity range is much lower than that of the material at the same temperature. By dimensionless treatment of the experimental results, a formula for calculating the dimensionless tensile strength of the neck of the ash in the high viscosity range is proposed. The formula is verified, and the calculated value is in good agreement with the experimental value. This formula lays a foundation for the establishment of ash deposition model in high viscosity range based on the analysis of the force of ash particles.
【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
【分類號(hào)】：TM621.2

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