The Research Of Corrosion-prevent Problem In Low-pressur Boiler Chemical Cleaning

In the process of industrialization, low-pressure boilers are extensively used in heating and increasing pressure in industrial production and people's lives. The water of the low-pressure boiler used is hard water, for example, groundwater and river water, water treatment often uses ion exchange technique. The more times the boiler uses, the more scale deposit it produces. Although we use the soften water, the scales effect heat conductivity, waste fuel and threat the boiler's safe function. So, we must clean the low-pressure boiler regularly. At present, the cleaning method is acid cleaning+ corrosion inhibitor. The acid used in chemical cleaning always erode the boiler itself, the corrosion inhibitor will lighten the affection of acid's corrosion. The cleaning efficiency and the corrosion-preventing efficiency are affected by many factors, such as the consistence of acid cleaning liquid, the cleaning time, the cleaning temperature and the consistence of corrosion inhibitor e.g. The cleaning waste liquid has many acid substance and dissolved substance, it can't be discharge directly. It must be disposed so that discharged to the natural water.In this study, we explore the problem of corrosion preventing on the progress of low-pressure boiler's chemical cleaning based on simulation experiment. With the test pieces of corrosion-preventing, tuned the consistence of acid cleaning liquid, the dosage of corrosion inhibitor, time of heating and temperature of heating, simulated the progress of boiler cleaning, we found the best corrosion-preventing condition, For low-pressure boiler's chemical cleaning do simulation operation, as soon as cleaning the water scale, saving material and reducing the boiler's fuels. In this study, the best corrosion conditions we received were:heating time of 3.5 hours, washing temperature is 50℃, inhibitor concentration 0.25g/10ml, acid lotion concentration of 3%. On the basis of the experimental conditions we implement a low-pressure boiler chemical cleaning project.With the help of the Blue Shield cleaning company, we do the low-pressure heating boiler chemical cleaning for the Prudential Group, Shandong Province, the process of chemical cleaning is as follow:Acid pickling tankâ†'Chemical cleaning pumpâ†'the front and left water wallâ†'Steam drumâ†'the right and behind water wallâ†'temporary systemâ†'acid pickling tank. In the cleaning process we add acid cleaning solution of 3% and corrosion inhibitors 0.25g/10ml, determine the acid chemical cleaning time -3.5 hours, the chemical cleaning of the heating temperature is 50℃. Cleaning waste water uses acid-base method for processing, cleaning effect and cleaning waste disposal liquid are all meet the state standards:1. For supervision and inspection corrosion specimens, the corrosion inhibition efficiency is 6.804g/(m2·h), much smaller than the standard value;2. To inspect the monitor pipe show that the chemical cleaning effect is perfect and the passivity effect was very good;3. Checking the boiler drum and the water wall inside, we gather up the sediment around 4kg;4. Discharging with acid-base pre-treatment, the cleaning waste liquid is up to the national wastewater discharge standards and are discharged into the sewage treatment facilities in the group together with other waste water treatment before discharge.