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“十三五”规划实施以来,我国对工业废水的处理要求日趋严格,尤其是“水十条”的出台,使脱硫废水零排放成为必然趋势[1-3]。目前,脱硫废水零排放处理工艺多采用预处理+浓缩减量+蒸发固化[4-9],其存在设备占地面积大、投资和运行成本高[10],直接蒸发固化工艺存在烟道腐蚀等风险[11];另一方面,当前电力环保新形势下电厂机组运行负荷普遍偏低,急需开发低成本的脱硫废水处理技术。利用渣水系统中的碱性炉渣处理脱硫废水中的重金属或酸性物质,以废治废,具有投资成本低,工艺改造简单等优势[12-16];但脱硫废水水质复杂,含盐量高,且pH较低,排入渣水系统后对渣水系统的腐蚀风险尚未可知。
本研究通过模拟实验,采用动态失重法和电化学法,系统地研究了添加不同比例脱硫废水的捞渣机补水混合液,对渣水系统中捞渣机、链条、水冷壁、关断门和冷灰斗等一系列直接接触混合液的关键部件金属材料的腐蚀影响,考察了温度、pH和电导率对材质的腐蚀规律;探讨了多因素共同存在下对金属材料的腐蚀规律;并提出了防腐蚀策略,本研究可为利用渣水系统处理脱硫废水提供理论指导和数据支持。
脱硫废水对渣水系统的腐蚀影响
Effect of desulfurization wastewater on slag water system corrosion
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摘要: 利用渣水系统处理脱硫废水是燃煤电厂脱硫废水实现低成本零排放处理的一个重要发展方向。为考察脱硫废水引入渣水系统后对设备材质的腐蚀行为的影响,采用动态失重法与电化学法分别对系统内的金属材质进行了腐蚀行为研究,分别考察了温度、pH、电导率3个因素对渣水系统的影响。结果表明: 1Cr18Ni9Ti钢和304不锈钢的腐蚀速率低于0.1 mm·a−1,属耐腐材质,适用于该电厂的运行工艺;而T12钢、65Mn钢、Q235钢、20CrMnTi钢等腐蚀速率高于1.0 mm·a−1,无法长期满足电厂的运行条件,应采取相应的防腐措施。此研究结果可以为燃煤电厂常用金属材质的腐蚀行为提供了科学依据和数据参考,为电厂的安全稳定运行提供借鉴和指导。Abstract: The utilization of slag water system to treat desulphurization wastewater is an important development direction for realizing low cost zero discharge treatment of desulphurization wastewater from coal-fired power plants. In order to investigate the influence of desulfurization wastewater on the corrosion behavior of equipment materials after the introduction of slag water system, the dynamic weight loss method and electrochemical method were used to study the corrosion behavior of metal materials in the system, and the influences of temperature, pH and conductivity on the slag water system were investigated. The results showed that the corrosion rates of 1Cr18Ni9Ti steel and 304 stainless steel were lower than 0.1 mm·a−1, which belonged to the corrosion resistant material and was suitable for the operation process of the power plant. However, the corrosion rates of T12 steel, 65Mn steel, Q235 steel and 20CrMnTi steel were higher than 1.0 mm·a−1, which could not meet the operating conditions of the power plant for a long time. Therefore, the corresponding anti-corrosion measures should be taken. This study provides scientific basis and data reference for the corrosion behavior of commonly used metal materials in coal-fired power plants, and provides reference and guidance for the safe and stable operation of power plants.
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表 1 腐蚀实验材质
Table 1. Materials used for corrosion test
设备名称 材质 型号与设计量 备注 水冷壁 T12钢 锅炉型号为SG-1913/25.4-M971 — 冷灰斗、上槽体 1Cr18Ni9Ti钢 内衬混凝土#400矾土水泥 内衬混凝土 关断门、管道 304不锈钢 管道壁厚为5 mm — 上槽体 65Mn钢 钢板厚度为9.5 mm 锌基底漆 刮板 Q235B钢 工作长度为1 508 mm — 链条 20CrMnTi钢 捞渣机专用模锻链 — 表 2 电厂捞渣机上清液和脱硫废水水质
Table 2. Water quality of supernatant and desulfurizing wastewater from the slag dredger of power plant
水质 温度/℃ pH 电导率/
(mS·cm−1)氯离子浓度/
(mg·L−1)捞渣机上
清液水质62.5~75.0 5.8~8.0 14.5~35.0 4 000~17 637.67 脱硫废水水质 37.6 5.9~6.5 30.6-37.7 7 000~19 350.59 表 3 不同比例脱硫废水和捞渣机上清液配制的混合液水质
Table 3. Water quality of mixture of desulfurization wastewater and supernatant of slag dredger in different ratios
水样编号 温度/℃ pH 电导率/(mS·cm−1) 氯离子浓度/(mg·L−1) 1 50 5 15.0 5 180.69 2 65 7 30.0 11 787.95 3 80 9 45.0 19 146.04 表 4 材质主要化学成分
Table 4. Main compositions of materials
% 材质 C Si Mn S P Cr Ni Ti Cu Fe 1Cr18Ni9Ti钢 ≤0.12 ≤1.00 ≤2.00 ≤0.030 ≤0.035 17.00~19.00 8.00~11.00 0.50~0.80 — ≥66.015 T12钢 1.15~1.24 ≤0.35 ≤0.40 ≤0.030 ≤0.035 — — — — ≥97.945 304不锈钢 ≤0.08 ≤1.0 ≤2.00 ≤0.03 ≤0.035 18.0~20.0 8.0~10.5 8.0-11.0 — ≥55.355 65Mn钢 0.62~0.70 0.17~0.37 0.90~1.20 ≤0.035 ≤0.035 ≤0.25 ≤0.25 — ≤0.25 ≥96.91 Q235B钢 ≤0.20 ≤0.35 ≤1.4 ≤0.045 ≤0.045 ≤0.30 ≤0.30 — ≤0.30 ≥97.06 20CrMnTi钢 0.17~0.23 0.17~0.37 0.80~1.10 ≤0.030 ≤0.030 1.00~1.30 ≤0.30 0.04~0.1 ≤0.30 ≥96.293 表 5 T12钢的腐蚀正交实验结果
Table 5. Orthogonal test results of corrosion of T12 steel
实验组 因素 腐蚀速率/
(mm·a−1)温度/℃ pH 电导率/(mS·cm−1) 1 50 5 15 1.781 6 2 50 7 30 2.323 2 3 50 9 45 1.288 1 4 65 5 30 2.341 1 5 65 7 45 1.651 4 6 65 9 15 1.774 6 7 80 5 45 1.923 2 8 80 7 15 2.387 8 9 80 9 30 2.672 5 K1 5.392 9 6.045 9 5.944 0 K2 5.767 1 6.362 4 7.336 8 K3 6.983 5 5.735 2 4.862 7 k1 1.797 6 2.015 3 1.981 3 k2 1.922 4 2.120 8 2.445 6 k3 2.327 8 1.911 7 1.620 9 极差R 1.590 6 0.627 2 2.474 1 表 6 1Cr18Ni9Ti钢的腐蚀正交实验结果
Table 6. Orthogonal test results of corrosion of 1Cr18Ni9Ti steel
实验组 因素 腐蚀速率/
(mm·a−1)温度/℃ pH 电导率/(mS·cm−1) 1 50 5 15 0 2 50 7 30 0.000 9 3 50 9 45 0.000 2 4 65 5 30 0.002 2 5 65 7 45 0.001 5 6 65 9 15 0 7 80 5 45 0.064 7 8 80 7 15 0.000 7 9 80 9 30 0 K1 0.001 1 0.066 9 0.000 7 K2 0.003 7 0.003 1 0.003 1 K3 0.065 4 0.000 2 0.066 4 k1 0.000 4 0.022 3 0.000 2 k2 0.001 2 0.001 0 0.001 0 k3 0.021 8 0.000 1 0.022 1 极差R 0.064 3 0.066 7 0.065 4 表 7 304不锈钢的腐蚀正交实验结果
Table 7. Orthogonal test results of corrosion of 304 stainless steel
实验组 因素 腐蚀速率/
(mm·a−1)温度/℃ pH 电导率/(mS·cm−1) 1 50 5 15 0.002 7 2 50 7 30 0 3 50 9 45 0.000 9 4 65 5 30 0.000 2 5 65 7 45 0.000 2 6 65 9 15 0 7 80 5 45 0.068 7 8 80 7 15 0.001 3 9 80 9 30 0 K1 0.003 6 0.071 6 0.004 0 K2 0.000 4 0.001 5 0.000 2 K3 0.070 0 0.000 9 0.069 8 k1 0.001 2 0.023 8 0.001 3 k2 0.000 1 0.000 5 0.000 1 k3 0.023 3 0.000 3 0.023 3 极差R 0.066 4 0.070 7 0.069 6 表 8 65Mn钢的腐蚀正交实验结果
Table 8. Orthogonal test results of corrosion of 65Mn steel
实验组 因素 腐蚀速率/
(mm·a−1)温度/℃ pH 电导率/(mS·cm−1) 1 50 5 15 1.437 7 2 50 7 30 1.978 3 3 50 9 45 1.450 1 4 65 5 30 2.054 1 5 65 7 45 1.734 6 6 65 9 15 2.128 7 7 80 5 45 1.260 5 8 80 7 15 2.182 6 9 80 9 30 2.112 5 K1 4.866 1 4.752 3 5.749 0 K2 5.917 4 5.895 5 6.144 0 K3 5.555 6 5.691 3 4.445 2 k1 1.622 0 1.584 1 1.916 3 k2 1.972 5 1.965 2 2.048 3 k3 1.851 9 1.897 1 1.481 7 极差R 1.051 3 1.142 9 1.698 8 表 9 Q235B钢的腐蚀正交实验结果
Table 9. Orthogonal test results of corrosion of Q235B steel
实验组 因素 腐蚀速率/
(mm·a−1)温度/℃ pH 电导率/(mS·cm−1) 1 50 5 15 1.684 6 2 50 7 30 1.644 2 3 50 9 45 0.985 3 4 65 5 30 2.433 5 5 65 7 45 2.849 0 6 65 9 15 2.289 0 7 80 5 45 3.542 4 8 80 7 15 1.786 1 9 80 9 30 1.815 0 K1 4.314 1 7.660 5 5.759 7 K2 7.571 5 6.279 3 5.892 7 K3 7.143 5 5.089 3 7.376 7 k1 1.438 0 2.553 5 1.919 9 k2 2.523 8 2.093 1 1.964 2 k3 2.381 2 1.696 4 2.458 9 极差R 3.257 4 2.241 2 1.617 0 表 10 20CrMnTi钢的腐蚀正交实验结果
Table 10. Orthogonal test results of corrosion of 20CrMnTi steel
实验组 因素 腐蚀速率/
(mm·a−1)温度/℃ pH 电导率/(mS·cm−1) 1 50 5 15 1.285 7 2 50 7 30 1.488 8 3 50 9 45 0.986 3 4 65 5 30 1.272 2 5 65 7 45 1.007 7 6 65 9 15 1.512 7 7 80 5 45 1.042 9 8 80 7 15 1.801 8 9 80 9 30 1.557 6 K1 3.760 8 3.600 8 4.600 2 K2 3.792 6 4.298 3 4.318 6 K3 4.402 5 4.056 6 3.036 9 k1 1.253 6 1.200 3 1.533 4 k2 1.264 2 1.432 8 1.439 5 k3 1.467 5 1.352 2 1.012 3 极差R 0.641 7 0.697 5 1.563 3 表 11 不同材质的电化学极化曲线的参数
Table 11. Parameters of electrochemical polarization curves of different materials
材质 密度/(g·cm−3) 自腐蚀电位/V 阳极Tafel斜率/mV 阴极Tafel斜率/mV 腐蚀电流/(A·cm−2) 腐蚀速度/(mm·a−1) 1Cr18Ni9Ti钢 7.85 −0.296 3.324 6.611 1.72×10−6 0.02 T12钢 7.85 −0.615 10.144 4.903 7.85×10−4 9.13 304不锈钢 7.93 −0.185 2.009 12.040 3.48×10−6 0.04 65Mn钢 7.81 −0.477 13.657 2.413 1.58×10−4 1.85 Q235B钢 7.85 −0.615 10.202 2.854 8.23×10−4 9.57 20CrMnTi钢 7.82 −0.471 10.491 2.710 1.13×10−4 1.32 -
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