【摘要】：生物質(zhì)能是當(dāng)今世界上僅次于煤炭、石油和天然氣的第四大能源,占世界能源消費(fèi)總量的14%;我國是農(nóng)業(yè)大國,秸稈資源豐富。然而秸稈資源除了分布分散、能量密度低、運(yùn)輸成本高等缺點(diǎn)外,熱轉(zhuǎn)化及燃燒過程中堿金屬和氯元素等引起等的顆粒物排放高、受熱面積灰、結(jié)渣和腐蝕現(xiàn)象,以及燃料熱值低等問題均限制其廣泛應(yīng)用。研究改善秸稈成型燃料品質(zhì)及其清潔利用,對(duì)替代煤炭和發(fā)展可再生能源具有戰(zhàn)略意義,是技術(shù)創(chuàng)新和行業(yè)可持續(xù)發(fā)展的基礎(chǔ)。而成型加工、添加劑改性、熱解提質(zhì)等是解決此類弊端的有效手段。本文從改良秸稈原料角度出發(fā),通過尋求合適的添加劑及成型熱解工藝達(dá)到提高秸稈燃料品質(zhì)及清潔燃燒的目的。采用實(shí)驗(yàn)、模擬分析、理論分析等方法研究添加劑對(duì)秸稈成型燃料燃燒中鉀遷移及控制、氯和硫等污染物控制的作用規(guī)律,并在此基礎(chǔ)上提出秸稈摻配添加劑—成型—熱解提升成型炭品質(zhì)的方法,系統(tǒng)研究熱解溫度和添加劑對(duì)成型炭理化、燃燒、灰熔融和污染物排放等特性的影響。本文開展的主要工作如下:選取NH_4H_2PO_4和Ca(H_2PO_4)_2作為磷基添加劑制備秸稈成型燃料,研究添加劑對(duì)灰熔融性及燃料燃燒成灰特性、鉀轉(zhuǎn)化的作用規(guī)律和機(jī)理。得出適宜的P/K摻配比為1.0～2.0,兩種添加劑均可以明顯提高成型燃料灰熔點(diǎn),并明顯改善成型燃料燃燒時(shí)熔融和結(jié)渣問題。添加劑在700～1100℃內(nèi)均有效抑制鉀析出,其中NH4H2PO4在1100℃時(shí)的固鉀效果最佳,此時(shí)玉米秸稈(MS)和棉稈成型燃料(CS)的固鉀率分別增長了 52.86%和64.89%。磷基添加劑與秸稈中的鉀元素結(jié)合生成高熔點(diǎn)K-Ca-P化合物,從而提高了灰熔點(diǎn)、改善了燒結(jié)和熔融現(xiàn)象并控制鉀析出,有利于秸稈成型燃料的清潔燃燒。選取BaCO_3、CaO和CaCO_3作為添加劑制備秸稈成型燃料,研究添加劑氯、硫等固定特性的影響。800℃后CaCl_2的分解反應(yīng)開始明顯,BaCl_2更穩(wěn)定,且BaCO_3在800～1000℃之間固氯能力明顯優(yōu)于CaO和CaCO_3。適宜的Ba/Cl摩爾比為2.5,BaCO_3對(duì)CS在1000℃燃燒時(shí)固氯率增長了5.35倍。模擬KCl、NH_4H_2PO_4/Ca(H_2PO_4)_2和BaCO_3三種物質(zhì)在500～1200℃反應(yīng)產(chǎn)物,結(jié)果表明NH_4H_2PO_4和Ca(H_2PO_4)_2可以較好的將KCl轉(zhuǎn)化為磷鉀鹽,但只增加1.5倍NH_4H_2PO_4添加量,950℃后KCl中接近75%的氯轉(zhuǎn)化為氣相HCl;只增加1.5倍BaCO_3添加量僅促進(jìn)約1%的氣相鉀析出。結(jié)合實(shí)驗(yàn)結(jié)果,在添加NH_4H_2PO_4/Ca(H_2PO_4)_2的基礎(chǔ)上摻配BaCO_3,適宜的Ba/K摩爾比為0.5～1,CS在1000℃燃燒時(shí)固氯率分別達(dá)到22.03%和26.20%。添加劑固硫能力由大到小依次為BaCO_3、CaCO_3、CaO。因此,通過摻配BaCO_3可顯著降低氯、硫污染物排放,達(dá)到清潔燃燒的目的。針對(duì)秸稈熱值低、炭產(chǎn)物難成型的問題,采用秸稈摻配添加劑—成型—熱解技術(shù)制備成型炭,研究熱解溫度(250-650℃)和磷基添加劑對(duì)成型炭理化特性和燃燒特性的影響。所得成型炭具有理想的抗跌碎特性和抗吸水能力。隨著熱解溫度的升高,MS中有機(jī)官斷裂、聚合重組,芳香結(jié)構(gòu)生成,添加劑不同程度上促進(jìn)熱解進(jìn)程。熱解中添加劑晶粒附著在纖維表面,和鉀反應(yīng)生成K-Ca-P化合物從而實(shí)現(xiàn)鉀轉(zhuǎn)化。所得成型炭熱值明顯提高,能量密度在10～15GJ/m3之間,優(yōu)于原始生物質(zhì)成型燃料或者粉狀、顆粒狀和纖維狀燃料。熱分析結(jié)果顯示隨著解熱溫度的升高,秸稈成型炭固定碳燃燒階段增強(qiáng)。因此,摻配添加劑—成型—熱解技術(shù)既有利于熱解階段鉀轉(zhuǎn)化和固定,又可以顯著提高秸稈成型燃料的熱值。研究了磷基添加劑和熱解溫度對(duì)成型炭灰熔融性、燃燒成灰特性、鉀轉(zhuǎn)化規(guī)律、氮氧化物和硫氧化物排放特性的影響。結(jié)果表明,實(shí)驗(yàn)熱解溫度下獲得的秸稈成型炭具有嚴(yán)重結(jié)渣傾向,軟化溫度隨熱解溫度的升高而降低;添加劑改良的成型炭軟化溫度顯著提高,熱解溫度為650℃時(shí)NH_4H_2PO_4和Ca(H_2PO_4)_2分別將軟化溫度提高490℃和422℃。添加劑改良的成型炭燃燒時(shí)鉀析出得到較好的控制,1000℃燃燒時(shí)最低固鉀率仍高于60%,并未出現(xiàn)熔融現(xiàn)象。表征分析和模擬結(jié)果表明,兩種磷基添加劑改善灰熔融性的作用原理不盡相同,盡管都具有將鉀轉(zhuǎn)化為高熔點(diǎn)K-Ca-P化合物的能力,NH_4H_2P0_4可更有效地抑制鉀析出和硅酸鉀鹽生成,而Ca(H_2PO_4)_2轉(zhuǎn)化為硅酸鈣和鈣磷化合物,從而改善灰熔融性。添加劑改良的成型炭SO_2和NO排放量均低于煤;獲得相同熱量的前提下,與生物質(zhì)原樣相比,磷基添加劑改良的成型炭具有低排放的優(yōu)勢(shì)。綜上所述,磷基添加劑改良的秸稈成型炭具有熱值高、熔點(diǎn)高、污染物低排放的優(yōu)點(diǎn),為秸稈成型燃料提質(zhì)及清潔燃燒提供理論技術(shù)指導(dǎo)。
[Abstract]:Biomass energy is the fourth largest energy in the world after the coal, oil and natural gas, accounting for 14% of the total energy consumption of the world; China is an agricultural power, and the straw resources are abundant. However, in addition to the disadvantages of distributed dispersion, low energy density, high transportation cost, etc., the problems of high emission of particulate matter such as alkali metal and chlorine in the process of heat conversion and combustion, such as high heating area ash, slagging and corrosion, and low fuel heat value, all restrict its wide application. The research improves the quality of straw-forming fuel and its clean utilization, and is of strategic significance to replace coal and to develop renewable energy, and is the basis for technological innovation and sustainable development of the industry. And the forming and processing, the additive modification, the pyrolysis upgrading and the like are effective means for solving the defects. In this paper, the purpose of improving the quality of the straw fuel and the clean combustion is achieved by looking for suitable additives and forming the pyrolysis process from the viewpoint of improving the raw material of the straw. The effects of additives on the control of potassium migration and control, chlorine and sulfur in the combustion of straw-shaped fuel were studied by means of experiment, simulation analysis and theoretical analysis. The effects of pyrolysis temperature and additives on the physical and chemical, combustion, ash fusion and pollutant discharge of the formed carbon were investigated. The main work in this paper is to select NH _ 4H _ 2PO _ 4 and Ca (H _ 2PO _ 4) _ 2 as the phosphorus-based additive to prepare the straw-forming fuel, and to study the effect and mechanism of the additive on the ash-melting property and the ash-forming property and the potassium transformation of the fuel. The proper P/ K ratio is 1.0-2.0, the melting point of the fuel ash can be obviously improved by the two additives, and the problem of melting and slagging in the combustion of the formed fuel is obviously improved. The effect of the additive on the precipitation of potassium was inhibited in 700-1100 鈩，

本文編號(hào)：2484197