钠碱法烟气脱硫废水回收利用研究

发布时间：2018-01-17 00:25

  本文关键词：钠碱法烟气脱硫废水回收利用研究　出处：《东北石油大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 钠碱法 含盐脱硫废水 回收利用 机械蒸汽再压缩 冷冻结晶

【摘要】：钠碱法烟气脱硫即将NaOH(或Na2CO3)溶液直接加入吸收塔,吸收废气中的SO2。与传统的石灰石/石膏法相比,钠碱法脱硫效率高、结垢现象少、副产物无二次污染等优点。该法所产生的脱硫废水无机盐物质含量超过1%,属于高含盐废水。此类废水直接排放将会使周边土壤、水体的含盐量升高从而对环境产生破坏,同时还浪费了资源。实现工业生产过程中高含盐废水排放量最小化或零排放,对环境保护具有重要的意义。本文研究对象为某热电厂钠碱法烟气脱硫废水,对该废水进行水质分析知该废水主要成分为无机盐类,其中Na2SO4含量最高在40~60 g/L之间。由此可知,应采用物理方法对该废水进行浓缩处理,将无机盐和水进行分离后分别加以回收利用。结合脱硫废水含盐量较高的特点及对几种高含盐废水的物理处理技术在经济、技术、环保等方面进行比较分析可知,机械蒸汽再压缩蒸发技术(MVR)在浓缩处理该高含盐脱硫废水方面更具优势。由于MVR技术在国内应用的实例较少且技术尚未成熟,大多数还处于实验室研究阶段且多集中于其性能的研究上。因此,文中对MVR系统进行了简单的介绍,并以该脱硫废水为研究对象对该系统性能进行了简单的分析。通过对MVR系统进行物料、能量衡算及传热方程的计算,建立了该系统的数学模型并分析了蒸发器内蒸发压强、压缩机压缩比、原料浓缩比等因素对MVR系统换热面积、压缩机功耗、制热能效系数等的影响。通过对它们之间的关系曲线分析及对系统投资成本及操作费用的综合考虑,得出本系统的最佳操作条件为蒸发压强在60~80 kPa,压缩机压缩比取1.6~2.2为宜。且可以在保持浓缩比不变的情况下,将浓缩液反复进行蒸发浓缩操作以达到所需浓度。对特定工艺操作条件下MVR系统及三效蒸发系统处理该脱硫废水进行能耗费用及冷却水处理费的比较得出,在废水处理量为1800 kg/h的工况下MVR系统每年可较三效蒸发系统节省近66.3万元的操作费用。由此可知,MVR蒸发技术相对于三效蒸发系统而言节能效果显著,明显降低了企业的操作费用,具有较好的应用前景。最后,根据硫酸钠的溶解度在32.4℃以下随温度的降低而迅速下降的特点,本文采用冷冻结晶的方法处理MVR系统排放的浓缩液,使硫酸钠以芒硝的形式析出,得到的芒硝可以达到回用要求。
[Abstract]:NaOH (or Na _ 2CO _ 3) solution is added directly to the absorber to absorb so _ 2 from waste gas. Compared with the traditional limestone / gypsum method, the sodium alkali method is more efficient than the traditional limestone / gypsum method. The desulfurization wastewater produced by this method has more than 1 inorganic salt content, which belongs to the high salt wastewater. The direct discharge of this kind of waste water will make the surrounding soil. The increase of salt content in water causes damage to the environment and waste of resources to minimize or zero discharge of high-salt wastewater in industrial production. It is of great significance to environmental protection. The main component of the wastewater is inorganic salt after the analysis of the water quality of the waste water, which is a kind of sodium-alkali flue gas desulphurization wastewater from a thermal power plant. The highest content of Na2SO4 was between 40 ~ 60 g / L, which suggested that the wastewater should be concentrated and treated by physical method. The inorganic salt and water are separated and recycled respectively. Combined with the characteristics of high salt content in desulphurization wastewater and the physical treatment technology of several kinds of high-salt wastewater, it is economical and technical. Environmental protection and other aspects of comparative analysis. The mechanical steam recompression evaporation technology (MVR) has more advantages in the concentrated treatment of the high salinity desulfurization wastewater. Because of the few examples of MVR application in China and the immature technology. Most of them are still in the stage of laboratory research and mostly focus on their performance. Therefore, this paper briefly introduces the MVR system. The performance of the desulfurization wastewater is analyzed simply, and the material, energy balance and heat transfer equation of the MVR system are calculated. The mathematical model of the system is established and the factors such as evaporator evaporation pressure compressor compression ratio and raw material concentration ratio on the heat transfer area and compressor power consumption of the MVR system are analyzed. The influence of heating energy efficiency coefficient etc. Through the analysis of the relationship curve between them and the comprehensive consideration of the system investment cost and operation cost. The optimum operating conditions of the system are as follows: evaporation pressure is 6080 KPA, compressor compression ratio is 1.6 ~ 2.2, and the concentration ratio can be kept constant. The concentrated liquid is repeatedly evaporated and concentrated to reach the required concentration. The comparison of energy consumption cost and cooling water treatment cost between the MVR system and the three-effect evaporation system for the treatment of the desulphurization wastewater under the specific process operation conditions is obtained. Under the condition that the wastewater treatment capacity is 1 800 kg/h, the MVR system can save nearly 663,000 yuan per year compared with the three effect evaporation system. Compared with the three-effect evaporation system, the MVR evaporation technology has a remarkable energy-saving effect, significantly reduces the operating costs of the enterprise, and has a good application prospect. According to the characteristic that the solubility of sodium sulfate decreases rapidly with the decrease of temperature below 32.4 鈩，

本文编号：1435507