Removing Sulfide in Gas Field Produced Water by Electrooxidation
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摘要: 为了防止含硫气田采出水中硫化物危害环境和人类健康,必须对其进行处理。采用污染小、效率高的电化学氧化法对高盐、高硬气田采出水的脱硫过程进行研究。选用Ti/RuO2-SnO2-IrO2阳极材料,在极板间距0.05 m,电流密度200 A/m2,曝气量1 L/min,初始pH 9-10的条件下,模拟采出水(300 mg/L初始硫化物,2.5% NaCl)处理35 min后,脱硫率高达99.2%以上,单位能耗为5.52 kWh/kgS2-。此外,本研究发现,针对高硬体系下的阴极结垢问题,利用倒极方法可有效去除结垢物,保证装置稳定运行。
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关键词:
- 气田采出水 /
- 硫化物 /
- 电氧化 /
- 金属氧化物涂层钛电极 /
- 阴极结垢
Abstract: Certain amounts of sulfide are present in gas field produced water and it brings negative effects on environment and human health, therefore, it is essential to remove sulfide first. Since the electrochemical oxidation method has the advantages of high efficiency without secondary pollution, here we introduced it into the sulfide removal process under the conditions of high salinity and hardness. Based on the cyclic voltammetry characteristics, sulfide removal efficiency, and economic analysis, Ti/RuO2-SnO2-IrO2 was selected as the anode. The removal of sulfide by two-dimensional electrochemical oxidation follows zero-order kinetics, that is, in all reaction stages, residual sulfide concentration in solution has a linear relationship with time. Sulfide exists in the form of HS− in the solution. When HS− is oxidized, H+ will be released. Therefore, it is necessary to select a suitable initial pH and control the reaction time. The sulfide removal ratio and corresponding energy consumption of simulated gas field produced water with 300 mg/L sulfide and 2.5% NaCl were >99.2% and 55.2 kWh/kg S2−, respectively, with the electrode distance of 5 cm, current density of 200 A/m2, aeration rate of 1 L/min, the initial pH of 9-10, and running time of 35 min. Moreover, reversing cathode and anode was found to effectively solve the problem of scaling on cathode caused by high Ca2+ and Mg2+ concentration. -
表 1 川渝地区典型气田含硫情况及气田水中硫化物浓度[1]
Table 1. H2S content of typical gas fields and sulfide concentration in gas field water in Sichuan and Chongqing
H2S content of typical
sour gas field/(10−3kg·m−3)Sulfide mass concentration in gas
field water/(mg·L−1)Classification of sulfide-
containing gas field waterSulfide mass concentration range/(mg·L−1) Shapingchang (0.1-0.4) 0.1-32.0 Low < 20 Xihekou (1.0-4.0) 4.5-72.0 Medium 20-100 Longwangmiao (4.0-12.0) 100.0-150.0 High 100-200 Puguang (180.0-250.0) 600.0-800.0 Extra high > 200 Yuanba (80.0-85.0) 800.0-2500.0 Longgang (20.0-80.0) 820.0-1600.0 表 2 磨溪206#采出水水样水质
Table 2. Composition of gas field produced water from Moxi 206#
No. pH Conductivity/
(mS·cm−1)${\;\rho}_{ \rm{Sulfide}}$/
(mg·L−1)${\;\rho}_{ \rm{COD}} $/
(mg·L−1)${\;\rho}_{ \rm{NH_3-N}} $/
(mg·L−1)${\;\rho}_{ \rm{Cl^{-1}}} $/
(104mg·L−1)${\;\rho}_{ \rm{Na^{+}}} $/
(104mg·L−1)${\;\rho}_{ \rm{Ca^{2+}}} $/
(mg·L−1)${\;\rho}_{ \rm{Mg^{2+}}} $/
(mg·L−1)1 6.43 43.9 303 88.0 60.9 1.71 1.09 588 68.2 2 6.32 53.6 348 75.0 75.8 2.09 1.31 730 93.6 3 6.73 41.6 287 250 70.1 1.58 1.07 443 51.4 4 6.37 53.2 300 275 77.0 2.09 1.30 736 86.4 5 6.80 39.3 286 50.0 57.3 1.48 0.986 427 48.3 6 6.79 46.1 263 125 73.4 1.81 1.14 617 75.5 表 3 不同阳极材料的价格
Table 3. Prices of different anodes
Anode type Price/
(103CNY·m−2)Anode type Price/
(103CNY·m−2)Ti/TiO2-RuO2-IrO2 10.19 Ti/IrO2-RuO2 21.02 Ti/IrO2-Ta2O5 25.48 Ti/RuO2-SnO2-IrO2 11.47 Ti/IrO2-Ta2O5-SnO2 26.75 Ti/SnO2-Sb2O3 7.643 Ti/RuO2-SnO2 9.554 Ti/SnO2-Sb2O3-IrO2 29.30 表 4 不同极板间距下平均槽电压和能耗对比
Table 4. Comparison of average cell voltages and energy consumption with different electrode distances
Electrode distance/m Treated water volume/L Average cell voltage/V Time for complete removal
of sulfide/103sEnergy consumption
/(kWh/kgS2-)Energy consumption per ton
of water
/(kWh·t−1)0.03 0.190 4.32 2.04 58.7 18.3 0.05 0.340 5.04 3.84 71.8 22.4 0.07 0.480 5.87 5.34 83.5 26.0 0.09 0.620 6.48 7.02 93.6 29.1 0.11 0.760 7.43 8.22 102 31.7 0.20 1.43 11.4 15.0 152 47.3 Note: Initial sulfide concentration is 311.3 mg/L. Current is 1.425 A, i.e. current density is 200 A/m2. 表 5 不同电流密度下达到相同脱硫率(70%)时的平均槽电压和能耗对比
Table 5. Average cell voltages and energy consumption at different current densities with the same sulfide removal ratio (70%)
Current density
/(A·m−2)Current/A Average cell voltage/V Time for the same sulfide removal ratio/103s Energy consumption per ton of water/(kWh·t−1) 100 0.694 4.87 3.60 11.3 150 1.040 5.29 2.70 13.8 200 1.387 5.94 2.22 16.9 250 1.734 6.22 1.80 18.0 300 2.081 7.13 1.62 22.3 表 6 不同NaCl含量下的单位能耗
Table 6. Energy consumption with different NaCl concentrations
NaCl concentration
/%Current
/AAverage cell voltage/V The amount of removed sulfide after 50 min/10−5kg Energy consumption
/(kWh/kgS2−)0.25 1.387 12.5 7.01 206 0.50 1.387 10.8 7.11 176 1.0 1.387 8.01 7.48 124 2.0 1.387 6.36 8.43 87.2 2.5 1.387 5.99 8.44 82.1 5.0 1.387 5.24 9.29 65.2 7.5 1.387 4.56 8.81 59.8 10 1.387 4.32 8.93 55.9 表 7 不同初始硫化物浓度的动力学方程拟合模型
Table 7. Fitting kinetic equations for different initial sulfide concentrations
Initial sulfide concentration/(mg·L−1) Fitting kinetic equation Reaction rate constant
·(mg·(L·s−1))R2 174.0 c=174.0−0.1556t 0.1556 0.9994 326.9 c=326.9−0.1561t 0.1561 0.9996 398.9 c=398.9−0.1593t 0.1593 0.9995 511.2 c=511.2−0.1727t 0.1727 0.9993 565.5 c=565.5−0.1687t 0.1687 0.9978 -
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