發(fā)布時間：2017-12-31 07:13

  本文關鍵詞：高堿煤熱化學轉化過程中堿金屬遷移轉化特性研究　出處：《中國科學院工程熱物理研究所》2017年博士論文　論文類型：學位論文

  更多相關文章： 準東高堿煤 堿金屬鈉 循環(huán)流化床 遷移轉化 氣化

【摘要】：準東高堿煤田是我國近年來發(fā)現(xiàn)的最大整裝煤田。準東高堿煤具有高揮發(fā)分、低灰分、反應活性好、儲量豐富、開采成本低等特點,適宜用作動力燃料和氣化用煤。但由于準東高堿煤中堿金屬含量高,在電廠煤粉鍋爐直接燃用過程中出現(xiàn)了爐內(nèi)燃燒器區(qū)結渣嚴重,鍋爐爐膛出口煙溫升高,高溫換熱面沾污嚴重,低溫受熱面積灰嚴重,部分過熱器發(fā)生超溫爆管等問題。目前準東高堿煤在現(xiàn)役機組上無法直接利用。為有效解決準東高堿煤利用過程中出現(xiàn)的結渣、沾污和腐蝕問題,本研究將循環(huán)流化床技術應用于準東高堿煤利用,開展高堿煤循環(huán)流化床熱化學轉化過程中堿金屬遷移轉化特性的研究,為高堿煤的大規(guī)模利用提供新的思路和工藝路線。本研究采用實驗研究和理論分析相結合的方法,以化學反應動力學和熱力學等基礎理論為指導,采用管式爐、循環(huán)流化床并結合化學熱力學計算軟件,利用1C、XRD、XRF及SEM-EDX等先進的分析手段,對準東高堿煤熱化學轉化過程中堿金屬的遷移轉化規(guī)律及煙氣冷卻過程中堿金屬的析出特性進行研究。獲得的主要結論如下:(1)準東高堿煤的基本物理化學特性與我國常規(guī)動力用煤顯著不同。煤中C1含量隨礦區(qū)不同而具有較大差異。煤灰中Na_2O含量較高,大于2%,屬于結渣煤種。具有良好的著火特性和燃盡特性。準東高堿煤中堿金屬鈉主要以水溶態(tài)形式存在,而堿金屬鉀元素與鈉元素不同,主要以不溶態(tài)形式存在。(2)預處理方法對準東高堿煤以及高堿煤氣化灰中堿金屬含量測定的準確性具有重要影響。為了準確獲得準東高堿煤及氣化灰樣品中的堿金屬含量,建議采用氧彈燃燒法進行煤中堿金屬含量的測定。另外,對于堿金屬鈉含量的測定,萃取法也可以相對準確的反映煤中堿金屬鈉的含量,同時獲得煤中堿金屬的賦存形態(tài)。(3)由于不同準東高堿煤中堿金屬含量不同,賦存形態(tài)不同,在煤氣化過程中的轉化途徑不同,其運行特性也有所不同。煤灰中Na_2O含量較高的天池木壘煤(灰中Na_2O含量7.28%)在循環(huán)流化床煤氣化運行過程中易于發(fā)生失流現(xiàn)象,而煤中Cl含量高的沙爾湖煤(煤中C1含量1.13%)則易于發(fā)生金屬換熱面的腐蝕。試驗結果及熱力學平衡計算結果表明,提高反應溫度和降低反應壓力可促進堿金屬的氣相析出。(4)反應氣氛對高堿煤熱化學轉化過程中堿金屬鈉的遷移轉化特性具有重要影響。隨著當量空氣系數(shù)的增加,氣相堿金屬鈉增加,固相堿金屬鈉減小�；抑形捶磻紝A金屬鈉具有固留作用。增加氣化劑氧氣濃度和水蒸氣濃度,可促進灰中堿金屬鈉由水溶態(tài)鈉向不溶態(tài)鈉轉化。在低當量空氣系數(shù)還原性氣氛和高當量空氣系數(shù)氧化性氣氛下,提升管內(nèi)的結渣問題和尾部換熱面的沾污問題尤為嚴重。在熱化學轉化初期,煤顆粒中水溶態(tài)堿金屬鈉一部分將會以氣相鈉的形式析出。在氧化性氣氛條件下,氣相鈉將會發(fā)生硫酸化反應生成硫酸鈉,而在還原性氣氛條件下,氣相鈉將保持原析出形態(tài)不變。另一部分水溶態(tài)堿金屬鈉則在高溫作用下向鹽酸溶態(tài)鈉及不溶態(tài)鈉形式轉化。(5)基于吉布斯自由能最小理論的化學熱力學平衡計算結果顯示,不同反應條件對不同煤種中堿金屬平衡分布的影響作用不同。升高反應溫度可促進堿金屬鈉的揮發(fā)及熔融。反應壓力主要影響堿金屬的氣相與固相平衡,升高反應壓力會抑制堿金屬的氣相析出,增加堿金屬的固相固留率。相較于氧化性氣氛,還原性氣氛下熔融態(tài)鈉的含量更高,表明在高堿煤實際熱化學轉化過程中,還原性氣氛下,更易于發(fā)生結渣。在富氧水蒸氣氣氛條件下大量堿金屬鈉被固留于固相中,氣相堿金屬較少且未有熔融態(tài)物質生成,計算結果與試驗結果基本一致。富氧水蒸氣氣化技術是解決準東高堿煤熱化學轉化過程中結渣沾污問題的極具發(fā)展前景的技術。
[Abstract]:The high alkali is the largest integrated coalfield coalfield discovered in China in recent years. The high alkali coal with high volatile, low ash content, good reaction activity, abundant reserves, low cost mining, suitable for use as fuel and coal gasification. But due to the high base of coal in Zhundong high content of alkali metals in pulverized coal fired boiler in power plant the direct use of appeared in the process of the burner slagging serious, boiler furnace outlet Wen Shenggao, high temperature heat transfer surface contamination is serious, low temperature heated area ash is serious, part of the superheater tube burst occurred. The problems at present in the existing high alkali Zhundong coal unit cannot be used directly. To solve the problem of high alkali Zhundong coal the use of slag in the process of contamination and corrosion problems, this study apply circular fluidized bed technology in Zhundong coal using high alkali, carry out coal in circulating fluidized bed thermochemical conversion process of high alkali alkali metal transfer characteristics The research, to provide ideas and new process route for the large-scale use of high alkali coal. This research adopts experimental research methods combined with theoretical analysis, with chemical reaction kinetics and thermodynamics theory, a tube furnace, the circulating fluidized bed combined with chemical thermodynamics calculation software, using 1C, XRD analysis method advanced XRF and SEM-EDX, studied the precipitation characteristics of alkali metal of high alkali coal conversion Zhundong thermochemical process of alkali metal migration and flue gas cooling process. The main conclusions are as follows: (1) the basic physical and chemical properties of Zhun Donggao base and China's conventional coal power coal is significantly different. The content of C1 in the coal mining area with different and have great difference. Higher Na_2O content of fly ash is more than 2%, which belongs to the slagging coal. With the ignition and burnout characteristics of good alkali metal sodium. High alkali coal mainly in Zhundong water In soluble form, and alkali metal potassium and sodium, mainly in insoluble form. (2) has an important influence on the accuracy of the determination of high alkali and high alkali Zhundong coal gasification ash alkali metal content in pretreatment method. In order to obtain the accurate content of alkali metal and alkali coal gasification ash Zhundong high in the sample determination suggested by oxygen bomb combustion method for alkali metal in coal content. In addition, for the determination of alkali metal sodium content, also can accurately reflect the relative content of sodium alkali metal in coal extraction, and speciation of alkali metal in coal. (3) due to the different high alkali Zhundong coal the alkali content in different, different forms, different ways of transforming the coal gasification process and its operation characteristics are also different. Higher Na_2O content in coal ash Tianchi Mulei coal (7.28% Na_2O ash content) in a circulating fluidized bed gasification process Easy to lose flow phenomenon, and the high Cl content in coal schallsee coal (1.13% C1 content in coal) is prone to the heat transfer surface of metal corrosion. The experimental results and thermodynamic equilibrium calculation results show that the higher reaction temperature and lower reaction pressure can promote the alkali metal vapor precipitation (4) has an important influence. The migration and transformation characteristics of reaction atmosphere transformation process of alkali metal sodium in high alkali coal. With the increase of air equivalent thermal coefficient, vapor of alkali metal sodium increased, solid alkali metal sodium decreased. Ash unreacted carbon has a retention effect on alkali metal sodium. The increase of gasification agent concentration of oxygen and water vapor concentration, can promote ash alkali metal sodium by water soluble sodium into insoluble sodium. The reducing atmosphere and the high equivalent coefficient of air oxidizing atmosphere in the low equivalent air coefficient, the riser slagging problem and the tail of the heat transfer surface contamination problem is particularly serious In the early form of thermochemical conversion, precipitation of coal particles in water soluble alkali metal sodium vapor will be a part of sodium. In the oxidizing atmosphere conditions, gas phase reaction of sodium sulfate will occur with sodium sulfate, and in reductive conditions, sodium vapor will remain unchanged. Another form of primary precipitation part of the water soluble alkali metal sodium under high temperature to the hydrochloric acid soluble and insoluble sodium sodium form. (5) the Gibbs free energy of chemical thermodynamic equilibrium theory of the minimum calculation results show that based on the different reaction conditions of different kinds of coal in different alkali metal equilibrium distribution effect. The reaction temperature can promote the volatile and molten alkali metal sodium. The main effect of reaction pressure alkali metal gas phase and solid phase equilibrium, increasing the reaction pressure will inhibit alkali metal vapor phase precipitation, solid alkali metal retention rate. Compared to the oxidizing atmosphere, but also the original Atmosphere in molten sodium higher, showed that the conversion in high alkali coal actual thermochemical process, reducing atmosphere, more prone to slagging. In the oxygen rich water vapor atmosphere under the condition of a large number of alkali metal sodium is retention in the solid phase, gas phase and no less alkali metal molten material formation the calculation results are consistent with the experimental results. The oxygen rich steam gasification technology is very promising to solve the contamination problem node transformation process of slag in high alkali coal chemical Zhundong technology.

【學位授予單位】：中國科學院工程熱物理研究所
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TQ530.2

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