本文關(guān)鍵詞：生物質(zhì)模型化合物堿金屬的釋放及堿金屬對灰熔融特性的影響　出處：《華北電力大學(xué)(北京)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 煤 生物質(zhì) 堿金屬 釋放 灰熔融特性

【摘要】：煤和生物質(zhì)是我國火力發(fā)電的主要燃料。燃料中堿金屬鉀和鈉的存在,能夠造成鍋爐的積灰、結(jié)渣和腐蝕等一系列問題,嚴(yán)重影響鍋爐的經(jīng)濟(jì)、安全運(yùn)行。生物質(zhì)中堿金屬鉀的含量較高而鈉的含量較低,煤中堿金屬的含量普遍較低,但高鈉煤(如準(zhǔn)東煤)中鈉的含量較高。因此,根據(jù)生物質(zhì)和煤燃料特性的不同,論文主要研究生物質(zhì)中堿金屬鉀的釋放規(guī)律,以及堿金屬鈉和鉀對灰熔融特性的影響規(guī)律。通過實(shí)驗(yàn)探究了負(fù)載KCl的纖維素、木聚糖、木質(zhì)素、果膠和松木在熱解過程中Cl和K的釋放和遷移規(guī)律以及CH_3Cl的生成機(jī)理。研究發(fā)現(xiàn),部分KCl中的K以有機(jī)K的形式轉(zhuǎn)移到了有機(jī)物中,并在更高的溫度下得到釋放。負(fù)載KCl的松木、木質(zhì)素和果膠由于含有碳環(huán)上的甲氧基官能團(tuán),能在熱解中產(chǎn)生大量的CH_3Cl,CH_3Cl主要在低溫下(200-350℃)生成,因而能夠被高溫和高升溫速率所抑制。利用智能灰熔融儀研究了合成灰中Na_2O的含量對灰熔融溫度的影響。實(shí)驗(yàn)表明,當(dāng)灰分中Na_2O的含量低于3%時(shí),提高Na_2O的含量能夠降低合成灰的初始變形溫度,但對軟化溫度、半球溫度和流動溫度影響較小;當(dāng)灰分中Na_2O的含量在3-10%范圍內(nèi)時(shí),提高Na_2O的含量能夠使合成灰的4個(gè)特征溫度全部降低。利用FactSage 7.0軟件包計(jì)算了隨著灰分中Na_2O含量升高和溫度升高的過程中礦物質(zhì)的變化趨勢。熱力學(xué)分析表明,鈉長石、霞石的產(chǎn)生是提高Na_2O的含量能夠降低灰熔融溫度的原因,含鈉礦物質(zhì)的產(chǎn)生替代了熔點(diǎn)更高的含鈣礦物質(zhì)(如鈣長石),同時(shí)與含鈣礦物質(zhì)發(fā)生低溫共熔,從而降低灰的熔融溫度。研究了不同成分合成灰中K_2O的含量對灰熔融溫度的影響。實(shí)驗(yàn)表明,對于CaO含量較低(0-5%)的煤灰,適量增加K_2O的含量(0-5%)有助于降低灰分的初始變形溫度、軟化溫度和半球溫度,但對流動溫度幾乎沒有影響;對于CaO含量較高(20-25%)的煤灰,適量增加K_2O的含量(0-5%)能夠使灰的4個(gè)特征溫度全部降低;對于生物質(zhì)灰,當(dāng)K_2O的含量低于30%時(shí),增加K_2O的含量有助于降低灰熔融溫度,繼續(xù)增加K_2O的含量(至50%)則對灰熔融溫度幾乎沒有影響。經(jīng)過熱力學(xué)計(jì)算分析可知,K_2O對灰熔融溫度的降低作用與含鉀礦物質(zhì)鉀長石、白榴石的產(chǎn)生相關(guān),含鉀礦物質(zhì)能與其他礦物質(zhì)發(fā)生低溫共熔,降低灰熔融溫度。研究了煤灰中不同氧化物的含量對灰熔融溫度的影響。向煤灰中分別添加Na_2O、MgO、SO_3和CaO來探究它們對灰熔融特性的影響規(guī)律。研究表明,提高Na_2O的含量(0-5.5%)能夠降低煤灰的熔融溫度,這與在合成灰中得到的結(jié)論相吻合;提高SO3的含量(6.5-13%)能夠升高煤灰的熔融溫度;提高M(jìn)gO的含量(3-9%)對煤灰的熔融溫度起到先降低后升高的作用;提高CaO的含量(13-47%)對煤灰的熔融溫度起到先降低后升高的作用。
[Abstract]:Coal and biomass are the main fuel for thermal power generation in China. The existence of alkali metal potassium and sodium in fuel can cause a series of problems, such as ash accumulation, slagging and corrosion of the boiler, which seriously affect the economic and safe operation of the boiler. Alkali metal in the biomass was higher and the content of sodium with low content of alkali metal in coal is generally low, but high sodium coal (such as coal) were higher in sodium. Therefore, according to the different characteristics of biomass and coal fuel, the paper mainly studies the release rule of alkali metal potassium in biomass, and the influence rule of alkali metal sodium and potassium on ash fusion characteristics. The release and migration of Cl and K in the pyrolysis process of cellulose, xylan, lignin, pectin and pine wood loaded with KCl and the formation mechanism of CH_3Cl were investigated through experiments. It was found that the K in part of KCl was transferred into organic matter in the form of organic K and released at a higher temperature. KCl loaded pine, lignin and pectin, which contain methoxy functional groups on the carbon ring, can produce a lot of CH_3Cl in pyrolysis. CH_3Cl is mainly generated at low temperature (200-350 degrees), and therefore can be inhibited by high temperature and high heating rate. The effect of the content of Na_2O in the synthetic ash on the ash melting temperature was studied by an intelligent ash melting instrument. Experiments show that when the content of ash in Na_2O is lower than 3%, improve the content of Na_2O can reduce the initial deformation temperature of synthetic ash, but has little effect on softening temperature, Hemisphere temperature and flow temperature; when the ash content in Na_2O in the range of 3-10%, improve the content of Na_2O can make the 4 characteristic temperature of synthetic ash all decreased. The FactSage 7 software package was used to calculate the mineral changes in the process of increasing the content of Na_2O and increasing the temperature in ash. The thermodynamic analysis shows that sodium feldspar, nepheline is produced to improve the content of Na_2O can reduce the ash melting temperature, sodium mineral substitute the higher melting temperature of calcium minerals (such as calcium feldspar), simultaneous eutectic with calcium containing minerals, thereby reducing the melting temperature of ash. The effect of the content of K_2O in different synthetic ashes on the melting temperature of the ash was studied. Experiments show that for low CaO content (0-5%) of the ash, the amount of the increase of the content of K_2O (0-5%) helps to reduce the ash content of the initial deformation temperature, softening temperature and Hemisphere temperature, but almost no effect on the flow temperature; with high content of CaO (20-25%) the amount of fly ash, the content of K_2O increased (0-5% 4) can make the characteristic temperature of ash for biomass ash, all decreased; when the content of K_2O is lower than 30%, the increase of the content of K_2O is helpful to reduce the ash melting temperature, the increase of K_2O content (up to 50%) of the ash melting temperature has little influence. Through thermodynamic calculation and analysis, it is known that the reduction of K_2O to ash fusion temperature is related to the production of potassium bearing minerals, potassium feldspar and garnet. Potassium containing minerals can co occur with other minerals at low temperature and reduce the ash fusion temperature. The influence of the content of different oxides in coal ash on the melting temperature of ash was studied. Na_2O, MgO, SO_3 and CaO were added to the coal ash to investigate their influence on the ash melting characteristics. Research shows that improve the content of Na_2O (0-5.5%) can reduce the melting temperature of ash, which is consistent with the conclusions obtained in the synthesis of ash; improve the content of SO3 (6.5-13%) can increase the melting temperature of ash; improve the content of MgO (3-9%) on the ash melting temperature has decreased first and then increased; improve the content of CaO (13-47%) on the ash melting temperature plays the role of first decreased and then increased.
【學(xué)位授予單位】：華北電力大學(xué)(北京)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TK6

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