非木材自苛化碱回收及黑液燃烧法除硅机理的研究

发布时间：2018-07-27 20:01

【摘要】：本论文针对非木材纤维原料制浆厂广泛存在的“硅干扰”和白泥回收综合利用问题,提出一种新的黑液燃烧法除硅技术,并将其与黑液自苛化相结合,在黑液燃烧过程中完成黑液自苛化的同时降低黑液硅含量。从而为解决“硅干扰”问题、降低白泥产量提供理论依据。文章从以下几个方面展开了研究:(1)竹浆黑液VIE值测定方法的研究通过响应面优化设计,对竹浆黑液的固含量、加热时间、加热温度和黑液添加量四个因素进行优化,获得竹浆黑液VIE值测定最佳工艺条件,为碱回收黑液的燃烧提供合理的数据支撑。研究表明:通过响应面设计得到黑液VIE值与黑液固含量(A)、加热时间(B)、加热温度(C)、和黑液质量(D)之间关系的二次回归方程模型,且其合理性比较高。各因素对黑液VIE值显著性影响的大小顺序依次为:加热温度(C)加热时间(B)固形物含量(A)黑液质量(D)。进而得出竹浆黑液VIE值测定的最佳参数为:固形物含量55wt.%,加热时间40min,加热温度360℃,黑液添加量5g。(2)竹浆黑液流变性能的研究降低竹浆黑液黏度,改善其流变特性可以为优化竹浆黑液碱回收系统各单元设计提供有效帮助。采用AR2000ex旋转流变仪对不同浓度(50~78wt.%)的硫酸盐竹浆黑液在不同温度下的流变性能进行分析。结果表明:硫酸盐竹浆中高浓黑液在0.1~100s-1的剪切速率范围内近似于非牛顿流体,并产生剪切-稀化现象。在高温、高固形物含量条件下,剪切-稀化的特性更加明显。在较低温度下,黑液体系所表现出的弹性模量和黏性模量相当。当固形物含量比较高时,黑液体系的弹性固体特性比较明显,此时当外界受力不足以完全破坏其结构时,其回复的能力比较大,从而会产生增稠现象。此外,黑液在低剪切速率下黏度与剪切速率的关系呈现不规则变化,但在一定的剪切速率范围内,黏弹性特征符合幂律区规律。(3)ICP法分析黑液无机元素含量文章提出一种采用ICP分析黑液中无机元素含量(Si、Mg、Al、Ca、B)的方法。该方法采用硝酸/过氧化氢(测硅时添加氢氟酸)消解体系对黑液样品进行预处理。黑液样品的消解量为1g,硝酸和过氧化氢的添加量为:10:4,消解后所得样品为无色透明试样,满足ICP测样要求。且ICP法测定黑液体系中的硅、铝、钙、镁等元素具有较好的准确度和精度,实验所得相对标准偏差低于0.8%,回收率在98%~103%之间。(4)镁盐除硅剂除硅效果的研究分别采用氧化镁和硫酸镁作为燃烧法除硅剂添加到黑液当中。实验所得氧化镁的最大除硅率为33%。硫酸镁除硅剂的添加量为2.0%时,除硅率可以达到82%,反应生成类似Mg2Al4Si5O18的沉淀物,该物质的粒径大约为21.20μm,比表面积为47.30 m2/g。黑液样品的TG-FT-IR分析结果显示,黑液样品在210℃和840℃左右出现最大失重,最大失重处产生的主要热解产物有CO2、CH4、H2O、醛酮类化合物和醇酚类化合物等。(5)自苛化协同黑液燃烧法除硅的研究分别对添加硼酸钠苛化剂和同时添加硫酸镁除硅剂和硼酸钠苛化剂的黑液进行了研究。结果发现:硼酸钠具有较好的自苛化效果,当硼酸钠添加量为15%,即B/Na比为0.2时,自苛化率达到65%。硫酸镁和硼酸钠在黑液燃烧过程中具有协同效应,反应所得绿液不溶物主要含有O、Mg、Al、Si、B、Ca等元素,其可能的化学组成有:Ca(Si2O5)、CaB2(SiO4)、Ca2B2O5等。
[Abstract]:Aiming at the problem of "Silicon Interference" and the comprehensive utilization of white mud recovery in the non wood fiber raw material pulping plant, a new black liquid combustion method is put forward to remove silicon from the black liquor and reduce the silicon content at the same time in the process of black liquor combustion. The theoretical basis of reducing the production of white mud is provided. The article has been studied in the following aspects: (1) the study on the VIE value determination method of the black liquor of bamboo pulp is optimized by the response surface optimization. The optimization of four factors, the solid content of the black liquor, the heating time, the heating temperature and the amount of the black liquor, is optimized, and the best process bar for the determination of the VIE value of the black liquor of bamboo pulp is obtained. It provides reasonable data support for the combustion of alkali recovery black liquor. The study shows that the two regression equation model of the relationship between black liquid VIE value and black liquid solid content (A), heating time (B), heating temperature (C) and black liquor mass (D) is designed by the response surface, and its rationality is higher. The size of the influence of each factor to the VIE value of black liquor is smooth. The order of the order is: heating time (C) heating time (B) solid content (A) black liquid mass (D). Then the optimum parameters for determining VIE value of black liquor of bamboo pulp are as follows: solid content 55wt.%, heating time 40min, heating temperature 360, 5G. (2) black liquor of black liquor, the viscosity of bamboo pulp black liquor can be reduced and its rheological properties can be improved. The AR2000ex rotating rheometer is used to analyze the rheological properties of the black liquor of different concentrations (50~78wt.%) at different temperatures. The results show that the high concentration black liquor in the sulphate bamboo pulp is similar to the non Newtonian fluid within the range of the shear rate of 0.1~ 100s-1. Under the conditions of high temperature and high solid content, the characteristics of shear thinning are more obvious. At lower temperatures, the elastic modulus and the viscosity modulus of the black liquor system are equal. When the solid content is high, the elastic solid characteristics of the black liquor system are more obvious, when the external stress is not enough to completely break. In addition, the relationship between viscosity and shear rate is irregular in the low shear rate, but in a certain range of shear rate, the viscoelastic characteristics conform to the law of power law. (3) a ICP method is used to analyze the content of inorganic elements in black liquid, and a kind of ICP is proposed. The method of analyzing the content of inorganic elements in black liquor (Si, Mg, Al, Ca, B). The method is pretreated with nitric acid / hydrogen peroxide (adding hydrofluoric acid) digestion system for black liquor samples. The elimination amount of black liquor samples is 1g, the amount of nitric acid and hydrogen peroxide is added as 10:4, and the samples are colorless transparent samples, which meet the requirements of ICP testing. The ICP method for the determination of silicon, aluminum, calcium and magnesium in the black liquor system has good accuracy and precision. The relative standard deviation of the experiment is less than 0.8% and the recovery rate is between 98%~103%. (4) the study on the effect of silicon removal by magnesium salt desilication agent is added to the black liquor by Magnesium Oxide and Magnesium Sulfate as the burning process desilication agent. The experimental Magnesium Oxide When the maximum removal rate of silicon removal is 2%, the addition of 33%. Magnesium Sulfate desilicon is 2%, the silicon removal rate can reach 82%, and the precipitate similar to Mg2Al4Si5O18 is generated. The particle size of the substance is about 21.20 mu m, and the TG-FT-IR analysis results of the specific surface area of 47.30 m2/g. black liquor show that the maximum weight loss of the black liquor samples around 210 and 840 centigrade, the maximum The main pyrolysis products produced by the weightlessness are CO2, CH4, H2O, aldehydes and ketones and alcohols and other compounds. (5) the study on the addition of sodium borate caustic and the addition of the Magnesium Sulfate and sodium borate caustic agent by the self caustic synergistic black liquor combustion method has been studied. The results show that sodium borate has good self causation. When the addition amount of sodium borate is 15%, that is, when the B/Na ratio is 0.2, the self caustic rate reaches 65%. Magnesium Sulfate and sodium borate in the black liquor combustion process, and the green liquid insoluble compounds mainly contain O, Mg, Al, Si, B, Ca and so on. The possible chemical compositions are Ca (Si2O5), CaB2 (SiO4), etc.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X793

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