燃煤电厂高盐脱硫废水固化基础实验

Basic experimental on solidification for high salt desulfurization wastewater in coal-fired power plant

  • 摘要: 脱硫废水零排放背景下,常规的蒸发和结晶工艺无法有效避免二次污染,提出了一种脱硫废水烟气浓缩及水泥化固定的技术路线。在烟气浓缩塔中,利用部分电除尘器后的烟气对脱硫废水进行蒸发浓缩,浓缩后的脱硫废水与水泥、粉煤灰等材料拌合后制得固化体,从而实现污染物的水泥化固定。实验将模拟高盐水与水泥、粉煤灰和河砂拌合,制得固化体,养护至特定龄期后,对其抗压强度和结合氯离子能力进行检测。通过控制单变量的方法,实验探究了不同组分材料的配比对固化体的抗压强度和结合氯离子能力的影响,并利用XRD对固化体粉末进行了产物表征。结果表明:在水泥配比为1.08时固化体的抗压强度最高,粉煤灰配比大于0.25后固化体的抗压强度提升明显,模拟高盐水配比越大,固化体的抗压强度越低,河砂量对固化体的抗压强度影响小。实验中制得的固化体在养护28 d后,其抗压强度值在30 MPa以上,能达到《混凝土路缘石》标准中路缘石的最低抗压强度要求。随着水泥配比的增大,固化体的结合氯离子能力增大21.7%,且受水泥水化所需水量的限制,其增大趋势渐缓;由于粉煤灰在水化过程中的产物与氯离子生成的Friedel’s盐量较少,随着粉煤灰配比的增大,固化体的结合氯离子能力仅增大4.9%。XRD的结果验证了水泥固化过程中Friedel’s盐的存在。

     

    Abstract: Under the background of zero liquid discharge of flue gas desulfurization ( FGD) wastewater,the conven-tional evaporation and crystallization process can’t effectively avoid the secondary pollution of FGD wastewater. Thus, a technical route of concentrating FGD wastewater using flue gas wasteheat and solidification with cement is proposed. In the concentration tower,the FGD wastewater is evaporated and concentrated by using part of the flue gas after the electric precipitator,and the concentrated FGD wastewater can be mixed with cement,fly ash and other materials to obtain solidified blocks,thereby realizing the solidification of the pollutants. Simulated high-salt water is mixed with ce-ment,fly ash and river sand to obtain measurement blocks in the experiment. After curing to a specific time,the compressive strength and the Cl- binding capacity of the blocks is tested. The impact of different component materials on the compressive strength and the Cl- binding capacity of the blocks is investigated by using the method of controlling univariate,and the powder from measurement blocks is characterized by XRD. The results show that the compressive strength of measurement blocks reaches the highest value when the cement ratio is 1. 08,and increases when the fly ash ratio is greater than 0. 25. The higher the percentage of high-salt brine,the lower the compressive strength,and the percentage of river sand in block has little effect on the compressive strength of blocks. After 28 days of curing,the measurement blocks prepared in the experiment has a compressive strength value of more than 30 MPa,which can meet the minimum compressive strength requirement of the curb in the standard of Concrete Curb. With the increase of the pecentage of cement,the Cl- binding capacity of the blocks increases by 21. 7% ,and the increase trend is limited by the amount of water required for cement hydration,so it is gradually slowed down. Due to the lower amount of Friedel’s salt which is produced by the reaction of the pruduct of fly ash in the process of cement hydration with Cl- , the Cl- binding capacity of the blocks only increases by 4. 9% with the increase of the pencentage of fly ash. The re-sults of XRD verify the existence of Friedel ’s salt during the solidification.

     

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