磷酸二氢铵对生物质固钾、灰熔融及燃烧特性的影响研究

发布时间：2018-06-04 11:19

本文选题：磷酸二氢铵 + 固钾　；参考：《山东大学》2015年硕士论文

【摘要】：生物质直燃发电是生物质能规模化利用的主要技术之一,但是由于生物质本身的以钾元素为代表的碱金属含量较高,由此容易引起燃用生物质的锅炉积灰、结渣、腐蚀等问题。本文选用5种典型生物质,通过模拟及实验方式研究了磷酸二氢铵(ADP)对生物质燃烧特性、固钾及灰熔融性的影响。(1)采用热力学平衡计算软件FactSage模拟探究生物质燃烧烟气氛围中ADP脱除KCl的效果,包括ADP的添加量对脱除KC1的影响和温度对ADP脱除KCl的影响。结果表明：在700～1000℃温度范围内,ADP脱除KC1的主要产物为磷酸氢二钾(PHP), KCl转化率随磷钾摩尔比(α)增大而增大,PHP的生成率随着温度的增加而增加。在不同反应温度下,最佳α=0.5；ADP与KCl的反应温度窗口较宽,在700～900℃的温度范围下ADP对KCl有很好的脱除效果；但温度高于900℃时,反应效果显著降低。(2)采用沉降炉系统探究反应时间(t)、反应温度(T)、磷钾摩尔比(α)对ADP与KCl的反应特性的影响。结果表明ADP可以与KCI反应生成多磷酸钾盐、磷酸氢钾盐和磷酸二氢铵钾盐。相同的T下,当a1.0时,产物主要以磷酸盐、偏磷酸盐、聚磷酸盐或高聚磷酸盐为主；而在a1.0时的情况下,产物主要为磷酸氢盐、磷酸氢铵盐和过量的未参与反应的ADP。即ADP的添加量对最终反应产组成形式的影响要大于反应时间的影响。在t=1 s的时候,两组反应均检测出了KCl的存在,而在t=2 s的时候,两组反应均未检测到KCl的存在,说明KCl的反应程度受t的影响大于受α的影响。(3)在固定床反应系统上用稻杆(RS)与ADP在空气氛围中不同温度下的燃烧反应来探究ADP在不同温度下对生物质燃烧中固钾特性的影响。实验结果表明：在a=1.0、T=700℃C和T=900℃时固钾率(η)分别达到23.1%和21.0%,比原始稻杆η提高了55.1%和63.1%；而T=500℃时,η比原始秸秆η无明显提高。固钾增长率(β)在500℃时很小,即加入ADP后固钾的效果不明显。但当T=700℃及T=900℃时β分别为55.06%和63.11%,表明ADP在燃烧过程中固钾性能良好,β随着温度的增加而增大。(4)采用灰熔点测定仪探究ADP对生物质灰熔融性的影响,实验结果表明,5种典型生物质在添加ADP之后灰熔融性有了不同程度的改善。对于含钾量较大的草本植物(玉米杆、棉杆和稻杆)加入ADP可大幅提高特征熔融温度,a=1.0时,其流动温度分别提高到1475℃、1380℃和1500℃；而对于含钾量较低的木本植物(杨木和松木),加入ADP提高特征熔融温度的幅度较小。实验采用SEM观察生物质灰的微观形貌并结合K-Ca-P三相图分析生物质成灰机制,得出ADP的加入可以抑制生物质灰的表面熔融现象,改善成灰特性,并且随着温度的升高ADP的固定钾的能力逐渐加强,且改善生物质灰熔融性的效果与生物质含钾量呈正相关。(5)采用TG/DTG分析了ADP对生物质的燃烧特性的影响,结果表明：5种生物质原样具有相似的燃烧特性。加入ADP后生物质的DTG曲线变得更加平缓、稳定,表明显加入ADP的生物质样品燃烧更加的缓和均匀；ADP本身具有阻燃作用,提高了生物质的燃尽温度及降低生物质燃烧指数。(6)对生物质及其添加ADP的试样进行燃烧动力学分析的结果表明,ADP的加入能够降低生物质燃烧过程中低温段的活化能,同时使生物质高温段燃烧的频率因子减少,降低了反应活性。本研究结果为生物质燃烧中钾元素转化捕集和改善灰熔融性提供一定的理论基础,对研究生物质成型燃料添加剂,以及解决碱金属所引起的结渣、积灰、腐蚀等问题具有指导意义。
[Abstract]:Biomass direct fired power generation is one of the main technologies for the scale utilization of biomass energy. However, because of the high content of alkali metal represented by the potassium element of biomass, it can easily cause the boiler ash, slag, corrosion and so on. In this paper, 5 kinds of typical raw materials have been selected to study phosphoric acid two by simulation and experimental methods. The effect of ammonium hydrogen (ADP) on the combustion characteristics of biomass, potassium fixation and ash fusion. (1) the effect of ADP removal of KCl in the atmosphere of biomass burning flue gas was simulated by the thermodynamic equilibrium calculation software FactSage, including the effect of ADP addition on the removal of KC1 and the effect of temperature on the removal of KCl by ADP. The results showed that, A within the temperature range of 700~1000 degrees, A The main product of DP removal of KC1 is two potassium hydrogen phosphate (PHP), and the conversion rate of KCl increases with the increase of phosphorus and potassium molar ratio (alpha). The formation rate of PHP increases with the increase of temperature. At different reaction temperatures, the optimum alpha =0.5; the reaction temperature window of ADP and KCl is wider, and ADP is good for removing KCl under the temperature range of 700~900; but temperature is very good for KCl. The reaction effect was significantly reduced when the degree was higher than 900. (2) the effect of reaction time (T), reaction temperature (T), and phosphorus and potassium molar ratio (alpha) on the reaction characteristics of ADP and KCl was investigated by the settler system. The results showed that ADP could react with KCI to produce potassium polyphosphate, potassium hydrogen phosphate and ammonium phosphate two potassium phosphate. Under the same T, when a1.0, the products were mainly in the case of a1.0. Phosphate, polyphosphate, polyphosphate, or polyphosphate are the main products; in the case of a1.0, the products are mainly hydrogen phosphate, the addition of ammonium phosphate and excess ADP., ADP, is greater than the effect of the reaction time. At the time of t=1 s, the two reactions detected K In the presence of Cl, the presence of KCl was not detected in the two groups at the time of t=2 s, indicating that the degree of KCl reaction was affected by T greater than that of alpha. (3) the effects of the combustion reaction of the rice rod (RS) and ADP in the air atmosphere at different temperatures in the fixed bed reaction system were used to explore the effect of ADP on the characteristics of potassium fixation in the combustion of biomass at different temperatures. The experimental results showed that the potassium fixation rate (ETA) reached 23.1% and 21% at a=1.0, T=700 C C and T=900, respectively, which was 55.1% and 63.1% higher than that of the original rice rod. While at T=500, the ETA was not significantly higher than that of the original straw. The growth rate of potassium fixation (beta) was very small at 500 degrees C, that is, the effect of fixing potassium after adding ADP was not obvious. It is 55.06% and 63.11%, which shows that ADP has good potassium retention performance during the combustion process and increases with the temperature. (4) the effect of ADP on biomass ash fusion is investigated by the ash melting point analyzer. The experimental results show that the ash melting property of the 5 typical biomass is improved in varying degrees after adding ADP. The addition of ADP to ADP can greatly increase the temperature of the characteristic melting. When a=1.0, the flow temperature is increased to 1475, 1380 and 1500, respectively. For the woody plants with lower potassium content (poplar and pine), adding ADP to improve the characteristic melting temperature is smaller. The micromorphology of the biomass ash is observed by the experiment. Combined with K-Ca-P three phase diagram to analyze the mechanism of biomass ash formation, it is concluded that the addition of ADP can inhibit the surface melting of biomass ash and improve the characteristics of ash forming, and with the increase of temperature, the ability of ADP to fixed potassium is gradually strengthened, and the effect of improving biomass ash fusion is positively related to the content of potassium in biological substance. (5) ADP is used to analyze ADP The effects on the combustion characteristics of biomass show that the 5 biomass samples have similar combustion characteristics. After the addition of ADP, the DTG curve of biomass becomes more gentle and stable. The combustion of biomass samples with the apparent addition of ADP is more smooth and uniform; ADP itself has a flame retardancy, which improves the burning temperature of biomass and reduces the growth of biomass. The material combustion index. (6) the results of the combustion dynamics analysis of the biomass and the sample adding ADP show that the addition of ADP can reduce the activation energy of the low temperature section during the combustion of biomass, and reduce the frequency factor of the combustion in the high temperature section of biomass, and reduce the reactivity. The results of this study are the transformation of potassium in biomass combustion. It provides a theoretical basis for the collection and improvement of ash fusibility, and has a guiding significance for the study of biomass briquette fuel additives, and the solution of slag, ash accumulation and corrosion caused by alkali metals.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM619;TK6

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