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That former water treatment was done by using Zinc inhibitor from a competitor. At the start up of the polymerisation, the polymer reactor (heat exchanger) has to be heated until 60 – 70 °C. As the polymerisation reaction is exothermic, this process has to be cooled down. This procedure has to be done at the start up of polymerisation, and the temperature of the cooling water is maintained at about 50°C. Steam is injected into the cooling water and the reactor is heated by a quasi closed system cycle. After the polymerisation process has started, the cooling water is then pressed into the hot water cycle and the reactor is cooled until a working temperature of 50 °C. During this short period of time the heat exchanger pipes were blocked from deposits of zinc phosphate, zinc hydroxide, zinc carbonate, zinc silicate and also calcium formulations.
Innowac Recommendation:
After our survey and water analysis, we noted the deposits were formed by the solubility product of zinc in combination with the carbonate, hydroxide, silicate and phosphate ions. We changed the zinc inhibitor to our phosphate program Innowac KI 105 and decreased the cycle water pH from 8 to 7.2, thus lessening the carbonate consumption. Result:
The corrosion rate is 0.01 – 0.03 mm / year on mild steel coupon and no deposits were found by normal shut downs. We have been treating this system for more than 9 years now.
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