生物質(zhì)雙床氣化氣氛下床料聚團(tuán)機(jī)理研究
發(fā)布時(shí)間：2018-08-15 13:12
【摘要】：生物質(zhì)雙流化床氣化工藝能夠產(chǎn)生高熱值煤氣,同時(shí)達(dá)到較高的碳轉(zhuǎn)化率。但在生物質(zhì)流化床氣化和燃燒過程中,床料顆粒易發(fā)生聚團(tuán)失流化。床料聚團(tuán)問題嚴(yán)重阻礙流化床的穩(wěn)定運(yùn)行。聚團(tuán)物的形成與生物質(zhì)灰熔特性密切相關(guān)。雙流化床系統(tǒng)中氣化器和燃燒器內(nèi)的氣氛完全不同,但生物質(zhì)灰在不同氣氛下引起床料聚團(tuán)的機(jī)理尚不清楚。國(guó)內(nèi)生物質(zhì)雙流化床氣化中試規(guī)模研究相對(duì)較少。本論文主要從生物質(zhì)灰熔特性、生物質(zhì)灰和鉀鹽引起的床料聚團(tuán)機(jī)理以及雙流化床氣化中試三個(gè)方面展開研究,主要研究?jī)?nèi)容和結(jié)果如下:首先,以熱機(jī)械分析儀為工具,提出一種生物質(zhì)灰的灰熔溫度測(cè)量方法,并分別以特征溫度Ts、Tm和T90表示灰樣的燒結(jié)溫度、劇烈熔化溫度和完全熔化溫度。與角錐法相比,該方法的重復(fù)性更好,且能夠更靈敏地測(cè)量到灰樣的燒結(jié)和初始熔化�；覙釉趧×胰刍A段的收縮是由硅酸鉀熔化引起的,硅酸鉀是引起床料顆粒粘結(jié)的主要物質(zhì),Tm可用于衡量不同生物質(zhì)灰熔化引起的床料聚團(tuán)失流化的傾向。其次,研究生物質(zhì)灰和石英砂床料在不同氣氛下的聚團(tuán)失流化機(jī)理。實(shí)驗(yàn)結(jié)果表明,與空氣和二氧化碳?xì)夥障啾?氫氣氣氛和水蒸氣氣氛下的床料聚團(tuán)失流化溫度更低。在空氣氣氛和氫氣氣氛下,床料顆粒的聚團(tuán)主要是由生物質(zhì)灰熔化引起;而在水蒸氣氣氛下,床料顆粒表面先形成硅酸鉀包裹層,硅酸鉀的熔化引起床料顆粒間的粘結(jié)。在氣化和燃燒氣氛下,床料聚團(tuán)均是由生物質(zhì)灰熔化引起的,但氣化氣氛下的聚團(tuán)失流化溫度更低。FactSage模擬計(jì)算結(jié)果表明,與燃燒氣氛相比,更多的K在氣化氣氛下轉(zhuǎn)化進(jìn)入熔渣相,生物質(zhì)灰和床層中的熔渣相比例均明顯增加。氣氛主要是通過改變鉀鹽的轉(zhuǎn)化來影響床料聚團(tuán)失流化溫度和聚團(tuán)機(jī)理。研究不同鉀鹽與石英砂床料的聚團(tuán)失流化機(jī)理,并研究氣氛對(duì)聚團(tuán)機(jī)理和鉀鹽轉(zhuǎn)化的影響。KCl和K_2SO_4分別在水蒸氣氣氛和氫氣氣氛下與石英砂中SiO_2反應(yīng)生成硅酸鉀,硅酸鉀的熔化引起床料顆粒的聚團(tuán)失流化;在任何氣氛下,K_2CO_3均能夠與石英砂中SiO_2發(fā)生反應(yīng)生成硅酸鉀,但與空氣氣氛相比,K_2CO_3和石英砂在水蒸氣氣氛和氫氣氣氛下的聚團(tuán)失流化溫度更低。FactSage計(jì)算結(jié)果表明,在氫氣氣氛和水蒸氣氣氛下,K_2CO_3容易轉(zhuǎn)化生成KOH,后者的熔化引起床料在更低溫度下發(fā)生聚團(tuán)失流化。在流化床燃燒和氣化實(shí)驗(yàn)中,小麥秸稈和玉米秸稈均會(huì)引起床料顆粒的聚團(tuán)失流化,而松木木屑燃燒和氣化過程中無失流化現(xiàn)象發(fā)生。與其他兩種生物質(zhì)相比,松木木屑中的K含量和K/Ca均最低。在雙流化床氣化過程中,通過控制流化床中K與床料的比例和選取合理的燃燒溫度及氣化溫度,能夠有效避免聚團(tuán)失流化的發(fā)生。在水蒸氣氣化條件下,煤氣熱值最高可達(dá)13 MJ/Nm3�？諝鈿饣退魵鈿饣瘲l件下的循環(huán)倍率分別為11.4和14。
[Abstract]:Biomass double fluidized bed gasification process can produce high calorific value gas and achieve high carbon conversion. However, in the process of biomass fluidized bed gasification and combustion, fluidization of pellets is easy to occur. The agglomeration problem of bed material seriously hinders the stable operation of fluidized bed. The formation of aggregates is closely related to the melting characteristics of biomass ash. The atmosphere in the gasifier and burner is completely different in the double fluidized bed system, but the mechanism of the agglomeration caused by biomass ash in different atmosphere is not clear. The pilot scale study of biomass double fluidized bed gasification in China is relatively few. In this paper, the characteristics of biomass ash melting, the agglomeration mechanism caused by biomass ash and potassium salt and the pilot-scale gasification of double fluidized bed gasification are studied. The main research contents and results are as follows: firstly, the thermal mechanical analyzer is used as a tool. A method for measuring the ash melting temperature of biomass ash is proposed. The sintering temperature, the violent melting temperature and the complete melting temperature of the ash sample are indicated by the characteristic temperature TsTm and T90, respectively. Compared with the angular cone method, this method is more reproducible and can be used to measure the sintering and initial melting of ash samples more sensitively. The shrinkage of ash samples in the violent melting stage is caused by the melting of potassium silicate, which is the main material that causes the agglomeration of the bed materials to be bonded, and TM can be used to measure the tendency of the fluidization of the agglomeration of the bed materials caused by the melting of different biomass ash. Secondly, the agglomeration and fluidization mechanism of ash and quartz sand bed materials in different atmospheres are studied. The experimental results show that the loss of fluidization temperature of bed material in hydrogen and steam atmosphere is lower than that in air and carbon dioxide atmosphere. In the atmosphere of air and hydrogen, the agglomeration of bed particles is mainly caused by the melting of biomass ash, while in the atmosphere of water vapor, the surface of bed material particles first forms a layer of potassium silicate, and the melting of potassium silicate leads to the bonding between the particles of bed materials. In gasification and combustion atmosphere, the agglomeration of the bed material is caused by biomass ash melting, but the fluidization temperature of the agglomeration in gasification atmosphere is lower. FactSage simulation results show that, compared with the combustion atmosphere, the fluidization temperature of the bed material is lower than that of the combustion atmosphere. More K was transformed into slag phase in gasification atmosphere, and the proportion of biomass ash and slag phase in the bed increased obviously. The atmosphere mainly influences the fluidization temperature and agglomeration mechanism of bed material by changing the transformation of potassium salt. The agglomeration and fluidization mechanism of different potassium salts and quartz sand bed materials were studied. The effects of atmosphere on agglomeration mechanism and potassium salt conversion were studied. KCl and K_2SO_4 reacted with SiO_2 in water vapor atmosphere and hydrogen atmosphere to form potassium silicate, respectively. The melting of potassium silicate leads to the agglomeration loss of fluidization of the bed material particles. In any atmosphere, K2COS3 can react with SiO_2 in quartz sand to form potassium silicate. However, compared with the air atmosphere, the fluidization temperature of K _ 2COC _ 3 and quartz sand in water vapor atmosphere and hydrogen atmosphere is lower. FactSage calculation results show that, K2CO3 is easily converted to KOH in hydrogen and steam atmosphere, and the melting of K2CO3 leads to agglomeration loss of fluidization at lower temperature. In fluidized bed combustion and gasification experiments, both wheat straw and corn straw can cause agglomeration and fluidization of bed particles, while no loss of fluidization occurs in the combustion and gasification of pine wood chips. Compared with the other two kinds of biomass, the K content and K/Ca in pine wood sawdust were the lowest. In the process of double fluidized bed gasification, by controlling the ratio of K to bed material and selecting reasonable combustion temperature and gasification temperature, the agglomeration loss of fluidization can be avoided effectively. Under the condition of steam gasification, the maximum calorific value of gas is 13 MJ / Nm ~ (3). The cycling rates of air gasification and steam gasification are 11.4 and 14.4 respectively.
【學(xué)位授予單位】：中國(guó)科學(xué)院大學(xué)(中國(guó)科學(xué)院過程工程研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ541
本文編號(hào)：2184306
[Abstract]:Biomass double fluidized bed gasification process can produce high calorific value gas and achieve high carbon conversion. However, in the process of biomass fluidized bed gasification and combustion, fluidization of pellets is easy to occur. The agglomeration problem of bed material seriously hinders the stable operation of fluidized bed. The formation of aggregates is closely related to the melting characteristics of biomass ash. The atmosphere in the gasifier and burner is completely different in the double fluidized bed system, but the mechanism of the agglomeration caused by biomass ash in different atmosphere is not clear. The pilot scale study of biomass double fluidized bed gasification in China is relatively few. In this paper, the characteristics of biomass ash melting, the agglomeration mechanism caused by biomass ash and potassium salt and the pilot-scale gasification of double fluidized bed gasification are studied. The main research contents and results are as follows: firstly, the thermal mechanical analyzer is used as a tool. A method for measuring the ash melting temperature of biomass ash is proposed. The sintering temperature, the violent melting temperature and the complete melting temperature of the ash sample are indicated by the characteristic temperature TsTm and T90, respectively. Compared with the angular cone method, this method is more reproducible and can be used to measure the sintering and initial melting of ash samples more sensitively. The shrinkage of ash samples in the violent melting stage is caused by the melting of potassium silicate, which is the main material that causes the agglomeration of the bed materials to be bonded, and TM can be used to measure the tendency of the fluidization of the agglomeration of the bed materials caused by the melting of different biomass ash. Secondly, the agglomeration and fluidization mechanism of ash and quartz sand bed materials in different atmospheres are studied. The experimental results show that the loss of fluidization temperature of bed material in hydrogen and steam atmosphere is lower than that in air and carbon dioxide atmosphere. In the atmosphere of air and hydrogen, the agglomeration of bed particles is mainly caused by the melting of biomass ash, while in the atmosphere of water vapor, the surface of bed material particles first forms a layer of potassium silicate, and the melting of potassium silicate leads to the bonding between the particles of bed materials. In gasification and combustion atmosphere, the agglomeration of the bed material is caused by biomass ash melting, but the fluidization temperature of the agglomeration in gasification atmosphere is lower. FactSage simulation results show that, compared with the combustion atmosphere, the fluidization temperature of the bed material is lower than that of the combustion atmosphere. More K was transformed into slag phase in gasification atmosphere, and the proportion of biomass ash and slag phase in the bed increased obviously. The atmosphere mainly influences the fluidization temperature and agglomeration mechanism of bed material by changing the transformation of potassium salt. The agglomeration and fluidization mechanism of different potassium salts and quartz sand bed materials were studied. The effects of atmosphere on agglomeration mechanism and potassium salt conversion were studied. KCl and K_2SO_4 reacted with SiO_2 in water vapor atmosphere and hydrogen atmosphere to form potassium silicate, respectively. The melting of potassium silicate leads to the agglomeration loss of fluidization of the bed material particles. In any atmosphere, K2COS3 can react with SiO_2 in quartz sand to form potassium silicate. However, compared with the air atmosphere, the fluidization temperature of K _ 2COC _ 3 and quartz sand in water vapor atmosphere and hydrogen atmosphere is lower. FactSage calculation results show that, K2CO3 is easily converted to KOH in hydrogen and steam atmosphere, and the melting of K2CO3 leads to agglomeration loss of fluidization at lower temperature. In fluidized bed combustion and gasification experiments, both wheat straw and corn straw can cause agglomeration and fluidization of bed particles, while no loss of fluidization occurs in the combustion and gasification of pine wood chips. Compared with the other two kinds of biomass, the K content and K/Ca in pine wood sawdust were the lowest. In the process of double fluidized bed gasification, by controlling the ratio of K to bed material and selecting reasonable combustion temperature and gasification temperature, the agglomeration loss of fluidization can be avoided effectively. Under the condition of steam gasification, the maximum calorific value of gas is 13 MJ / Nm ~ (3). The cycling rates of air gasification and steam gasification are 11.4 and 14.4 respectively.
【學(xué)位授予單位】：中國(guó)科學(xué)院大學(xué)(中國(guó)科學(xué)院過程工程研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ541
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