本文選題：牛糞 + 熱解特性　； 參考：《華中農(nóng)業(yè)大學(xué)》2017年博士論文

【摘要】：隨著人們生活水平的提高,對(duì)奶制品、肉制品的需求大幅增加,促進(jìn)了我國(guó)奶牛、肉牛養(yǎng)殖業(yè)的規(guī)�；l(fā)展。牛糞是奶牛、肉牛養(yǎng)殖過(guò)程中不可避免的污染物,若大量的牛糞得不到及時(shí)處理,不僅會(huì)影響?zhàn)B殖場(chǎng)的發(fā)展,還會(huì)污染周邊的環(huán)境,對(duì)人們的生命健康構(gòu)成威脅。牛糞中含有豐富的有機(jī)成分,具有轉(zhuǎn)化為生物燃料的潛能。熱化學(xué)方法具有處理效率高,周期短,能夠在熱處理過(guò)程中殺死糞便中病毒細(xì)菌,且產(chǎn)生一氧化碳、氫氣、生物炭、生物油等高附加值燃料。其中氫氣是一種燃燒生成水、清潔無(wú)污染的燃料,被認(rèn)為是能夠替代化石燃料的最理想的未來(lái)能源之一。本研究擬采用氣化技術(shù)將牛糞轉(zhuǎn)化為富氫氣體,從牛糞熱解機(jī)理入手,通過(guò)試驗(yàn)研究牛糞原位氣化和分步氣化2種模式下主要工藝參數(shù)對(duì)產(chǎn)物特性的影響,以實(shí)現(xiàn)高效處理牛糞并制備富氫氣體的目的。其主要研究?jī)?nèi)容及結(jié)果如下:(1)開(kāi)展了牛糞熱解機(jī)理的研究。根據(jù)范式洗滌原理對(duì)牛糞進(jìn)行處理獲得不同成分組合的洗滌纖維,采用熱重分析實(shí)驗(yàn)方法探討牛糞中不同組分洗滌纖維的熱解特性。結(jié)果表明牛糞中中性洗滌溶解物的含量最大為39.35%,半纖維素和纖維素含量次之,分別為26.24%、24.05%,木質(zhì)素的含量較低。以纖維素為主要成分的酸性洗滌纖維,熱解速率最大,為14.31%/min,強(qiáng)酸洗滌纖維熱解速率最小為1.62%/min。牛糞不同組分在熱解過(guò)程中相互影響而不是簡(jiǎn)單的疊加,纖維素的加入使木質(zhì)素的熱解速率和溫度區(qū)間發(fā)生變化,半纖維素的存在對(duì)纖維素的熱解揮發(fā)具有一定的抑制作用,使得纖維素的熱解速率由14.31%/min降低到7.62%/min,木質(zhì)素、纖維素和半纖維素三組分的熱解存在耦合作用。(2)建立了牛糞熱解動(dòng)力學(xué)模型。采用離散分布活化能模型深入分析了牛糞熱解特性及其各化學(xué)組分之間的耦合關(guān)系,對(duì)超高、超低升溫速率下熱解特征進(jìn)行了預(yù)測(cè)和對(duì)比分析,研究了揮發(fā)分析出過(guò)程中所對(duì)應(yīng)的起始溫度、終止溫度、峰值溫度以及峰值速率等特征參數(shù)隨升溫速率的變化規(guī)律。結(jié)果表明牛糞的熱解過(guò)程可以通過(guò)27個(gè)主導(dǎo)反應(yīng)來(lái)精準(zhǔn)表征,且這些反應(yīng)可以分成4組分別代表牛糞4組分(中性洗滌溶解物,半纖維素,纖維素和木質(zhì)素)的熱解過(guò)程。各組分的分解沒(méi)有明確的邊界,它們相互作用、相互耦合。隨著升溫速率的不同,各組分之間的這種關(guān)聯(lián)耦合特性亦發(fā)生變化。(3)開(kāi)展了高濕牛糞原位氣化制備富氫氣體關(guān)鍵工藝參數(shù)的研究。以濕牛糞為研究對(duì)象,在固定床反應(yīng)器內(nèi)采用單因素試驗(yàn)的方法,對(duì)不同溫度、水分質(zhì)量分?jǐn)?shù),升溫速率和進(jìn)料溫度條件下原位熱解氣化產(chǎn)氣率、成分、熱值,氫氣產(chǎn)率和碳轉(zhuǎn)化率的變化進(jìn)行研究和分析。試驗(yàn)結(jié)果表明,隨著溫度和水分質(zhì)量分?jǐn)?shù)的增加,氫氣的體積百分含量、熱解氣的產(chǎn)率和熱值增加;升溫速率和進(jìn)料溫度對(duì)氫氣的體積百分含量和產(chǎn)氣率的影響不顯著。濕牛糞的原位氣化結(jié)果表明牛糞有制備氫氣的潛能,氫氣的最大產(chǎn)率為536.64ml/g,氫氣的含量最高達(dá)到了50.57%。原位氣化過(guò)程中各反應(yīng)相互重疊,反應(yīng)復(fù)雜且熱解產(chǎn)生的揮發(fā)分對(duì)生物半焦的反應(yīng)活性和蒸氣氣化反應(yīng)有抑制作用。(4)開(kāi)展了“牛糞低溫炭化-半焦高溫氣化”兩步氣化制取富氫氣體的研究。在低溫炭化階段重點(diǎn)分析操作參數(shù)對(duì)牛糞低溫炭化反應(yīng)機(jī)理的影響,主要采用正交設(shè)計(jì)研究了溫度、含水率、升溫速率、進(jìn)料量、反應(yīng)時(shí)間對(duì)產(chǎn)物分布的影響,采用全因素實(shí)驗(yàn)設(shè)計(jì)研究溫度和含水率對(duì)產(chǎn)物分布和炭特性的影響,采用單因素試驗(yàn)分析溫度和炭化時(shí)間對(duì)干牛糞低溫炭化的影響。結(jié)果表明溫度是影響產(chǎn)物分布和炭特性的主要因素,當(dāng)含水率固定在75%,隨著炭化溫度從400℃增加到600℃,固體半焦的產(chǎn)率從47.30%降低到37.70%。含水率的對(duì)產(chǎn)物分布有一定的影響,但含水率的影響受溫度的限制,且含水率主要改變液體和氣體的產(chǎn)率。水蒸氣的存在抑制了反應(yīng)器內(nèi)重油的二次裂解反應(yīng),促進(jìn)了重油的水蒸氣氣化反應(yīng)。溫度是影響固體半焦C、H、O、固定碳、揮發(fā)份、灰分含量以及半焦熱解特性、晶體結(jié)構(gòu)、礦物質(zhì)含量的主要因素,含水率對(duì)牛糞半焦的特性影響不明顯。其中600℃條件下制備的半焦C含量高達(dá)80.59%。因此以制備半焦為目的的炭化過(guò)程中,可以主要考慮溫度的影響。(5)進(jìn)行了兩步氣化過(guò)程中高溫氣化段的試驗(yàn)研究。主要研究了半焦氣化反應(yīng)機(jī)理和操作參數(shù)對(duì)半焦高溫氣化產(chǎn)氣效果的影響,并選取不同特性的半焦為原料進(jìn)行氣化重整試驗(yàn),分析半焦對(duì)產(chǎn)氣效果的影響。試驗(yàn)結(jié)果表明:提高氣化溫度能夠增加產(chǎn)氣率和產(chǎn)氫率,適宜的水蒸氣流速能夠促進(jìn)氫氣的產(chǎn)率,高溫加熱模式有助于制取富氫氣體,牛糞灰可以促進(jìn)半焦氣化過(guò)程中焦油的產(chǎn)生,但會(huì)抑制氣化過(guò)程,影響氣相得率。半焦高溫氣化的較優(yōu)的工藝參數(shù)為氣化溫度850℃,水蒸氣流速1.66g/min,高溫進(jìn)料方式,氫氣的最大產(chǎn)率為1105.30ml/g,氫氣百分含量最高達(dá)到了59.08%。不同溫度制備的半焦在最佳參數(shù)下的氣化結(jié)果表明高溫條件制備的半焦有助于氫氣的產(chǎn)生,根據(jù)氫氣產(chǎn)率的大小對(duì)原料排序?yàn)?BC-500BC-600BC-350BC-400BC-300牛糞,其中BC-300~BC-600分別表示在炭化溫度300℃~600℃,反應(yīng)時(shí)間30min條件下制取的牛糞半焦。在相同的氣化條件下,牛糞和BC-300在氣化過(guò)程中的轉(zhuǎn)化率高于BC-500和BC-600,但牛糞和BC-300的產(chǎn)氣率低于BC-500和BC-600的產(chǎn)氣率。這表明牛糞和BC-300中的組分主要轉(zhuǎn)化為了生物油。因此高溫度制備的半焦有利于氣化制氫,且能夠降低生物油的產(chǎn)率。(6)牛糞的組分和熱特性研究表明牛糞具有熱化學(xué)處理的潛能,可以采用熱化學(xué)方法處理牛糞。原位氣化和分步氣化的研究結(jié)果表明:a.牛糞具有氣化制氫的潛能;b.相比于原位氣化,分步氣化的方法提高了氫氣的產(chǎn)率并減少生物油的產(chǎn)率;c.高溫下制備的半焦是較優(yōu)的氣化材料。d.牛糞半焦的氣化產(chǎn)氫量?jī)?yōu)于牛糞氣化的產(chǎn)氫量,且半焦氣化可以減少生物油的產(chǎn)率;e.850℃的氣化溫度是半焦氣化的適宜溫度;f.牛糞半焦的質(zhì)量是牛糞原料的40%左右,可減少高溫段氣化裝置成本及能耗。因此,牛糞分步氣化制取富氫氣體是一種處理牛糞污染物、制取富氫氣體的有前景的、有潛力的技術(shù)。
[Abstract]:With the improvement of people's living standards, the demand for dairy products and meat products has been greatly increased, which has promoted the large-scale development of dairy cattle and cattle breeding in China. Cow dung is an inevitable pollutant in the process of cow and beef cattle breeding. If a large amount of cow dung is not treated in time, it will not only affect the development of the farm, but also pollute the surrounding environment. It is a threat to the health of people. The cow dung contains rich organic ingredients and has the potential to convert into biofuel. The thermochemical method has high treatment efficiency, short cycle, and can kill the virus bacteria in the feces during heat treatment, and produce high added value fuel such as carbon monoxide, hydrogen, biological carbon and bio oil. It is considered to be one of the most ideal future energy sources to replace fossil fuels. This study is intended to convert cow dung into hydrogen rich gas by gasification technology. From the mechanism of cow dung pyrolysis, the main technological parameters of the 2 models of cattle manure in situ gasification and stepwise gasification are studied by experiments. The main research contents and results are as follows: (1) the study of the mechanism of cow dung pyrolysis was carried out. The washing fiber of different composition of cow manure was obtained according to the principle of normal form washing, and the different components washing in cow dung was studied by thermogravimetric analysis. The results show that the maximum content of neutral detergent dissolved in cow dung is 39.35%, the content of hemicellulose and cellulose is 26.24%, 24.05%, and lignin is lower. The acid washing fiber with cellulose as the main component has the highest pyrolysis rate of 14.31%/min and the minimum pyrolysis rate of strong acid washing fiber is 1.62. The different components of%/min. cow dung affect each other in the pyrolysis process rather than the simple superposition. The addition of cellulose makes the pyrolysis rate and temperature range of lignin change. The presence of hemicellulose has a certain inhibitory effect on the pyrolysis and volatilization of cellulose, making the thermal hydrolysis rate of cellulose reduced from 14.31%/min to 7.62%/min and lignin. The pyrolysis of three components of cellulose and hemicellulose has a coupling effect. (2) a kinetic model of cow dung pyrolysis is established. The pyrolysis characteristics of cow dung and the coupling relationship between the chemical components are deeply analyzed by the discrete distribution activation energy model. The characteristics of the thermal solution at ultra high and ultra-low heating rates are predicted and compared, and the volatiles are studied. The results show that the pyrolysis process of cow dung can be accurately characterized by 27 dominant reactions, and these reactions can be divided into 4 groups to represent 4 components of cow dung (neutral detergent solution, semi fiber). The decomposition of vitamin, cellulose and lignin. The decomposition of components has no definite boundary, they interact with each other. With the difference of heating rate, the coupling characteristics of each component also change. (3) the study of the key technological parameters for the preparation of hydrogen rich gas by in situ gasification of high humidity cow dung. In a fixed bed reactor, a single factor test was used to study and analyze the change of gas production rate, composition, calorific value, hydrogen yield and carbon conversion rate at different temperatures, water mass fraction, heating rate and feed temperature. The results showed that the temperature and water mass fraction were found. Increasing the volume fraction of hydrogen and increasing the yield and calorific value of thermal gas, the effect of heating rate and feed temperature on the volume percentage and gas production rate of hydrogen is not significant. The results of in situ gasification of wet cow dung show that the cow dung has the potential of producing hydrogen, the maximum yield of hydrogen is 536.64ml/g, and the highest hydrogen content reaches 50.57%. original. The reaction overlaps each other during the gasification process, and the reaction is complex and the volatiles produced by pyrolysis have a inhibitory effect on the reactivity and vaporization of the biological char. (4) a study on the production of hydrogen rich gas by two step gasification of "low temperature carbonization and semi coke high temperature gasification" of cow dung is carried out. The effect of temperature, water content, heating rate, feed volume and reaction time on the distribution of products was studied by orthogonal design. The effects of temperature and water content on the distribution of products and carbon properties were studied by full factor experimental design. The temperature and carbonization time were used to analyze the low temperature carbon of dry cow dung. The results show that temperature is the main factor affecting the distribution and characteristics of the products. When the water content is fixed at 75%, with the carbonization temperature increasing from 400 to 600, the yield of solid semi coke from 47.30% to 37.70%. water content has a certain effect on the distribution of products, but the effect of water content is limited by temperature, and the water content is main. Change the yield of liquid and gas. The existence of water vapor inhibits the two cracking reaction of heavy oil in the reactor and promotes the vaporization of heavy oil. Temperature is the main factor affecting the C, H, O, fixed carbon, volatiles, ash content and semi coke, crystal structure, mineral content, and water content to cow dung semic. The effect of the characteristics is not obvious. The C content of the semi coke prepared under 600 centigrade is up to 80.59%., so the effect of temperature can be mainly considered during the carbonization process for the purpose of preparing the semi coke. (5) the experimental study on the high temperature gasification section in the two step gasification process is carried out. The mechanism of the semi coke gasification reaction and the operation parameters are mainly studied on the high temperature gas of the semi coke. The effect of gas production is changed, and the gasification reformer test is carried out with different characteristics of the char as raw material. The effect of semi coke on gas production is analyzed. The results show that the gasification temperature can increase gas production rate and hydrogen production rate, the suitable steam flow velocity can promote hydrogen production, and the high temperature heating mode helps to produce hydrogen rich gas. The fecal ash can promote the production of tar in the process of semi coke gasification, but it can inhibit the gasification process and affect the gas phase yield. The better technological parameters of the high temperature gasification of semi coke are the gasification temperature 850 C, the flow velocity of 1.66g/min, the high temperature feeding way, the maximum hydrogen yield of 1105.30ml/g, and the highest hydrogen content reached 59.08%. different temperature system. The gasification results of the prepared semi coke under the optimum parameters indicate that the semi coke prepared at high temperature is helpful to the production of hydrogen. According to the size of the hydrogen yield, the raw material is ordered as BC-500BC-600BC-350BC-400BC-300 cow dung, and the BC-300~BC-600 shows the cow dung semi coke at the temperature of 300 C, ~600, and 30min, respectively. Under the same gasification conditions, the conversion rate of cow dung and BC-300 in the gasification process is higher than that of BC-500 and BC-600, but the gas production rate of cow dung and BC-300 is lower than that of BC-500 and BC-600. This indicates that the components of cow dung and BC-300 are mainly converted to bio oil. Therefore, the high temperature prepared char is beneficial to the gasification of hydrogen and can reduce the bio oil. Yield. (6) studies on the composition and thermal characteristics of cow dung show that cow dung has the potential of thermochemical treatment and can be treated by thermochemical method. The results of in situ gasification and stepwise gasification show that A. cow dung has the potential of gasification for hydrogen; B. is compared to in situ gasification, and the method of stepwise gasification improves the yield of hydrogen and reduces bio oil. The yield of the semi coke prepared by C. at high temperature is better than that of.D. cow dung gasification, and the yield of hydrogen production is better than that of cow dung gasification. The gasification temperature of e.850 centigrade is the suitable temperature for the gasification of semi coke, and the quality of F. cow dung is about 40% of the cow dung raw material and can reduce the gasification at high temperature. Therefore, it is a promising and promising technology to produce hydrogen rich gas by step gasification of cow dung.

【學(xué)位授予單位】：華中農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ116.2

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