A few questions about boilers
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I recently changed jobs, and my boss asked me to take a look at the boiler water softening system. I haven’t dealt with this before, and I have a few questions I’d like to ask. It is a 2-ton boiler that burns coal; the steam pressure is around 4 kilograms. The feed water is groundwater with a water hardness of 2.6 mmol/l. A sodium ion exchange column is used, with a diameter of 0.75 m and a height of 1.5 m. The required hardness level of the water entering the boiler is below 0.1 mmol/l. 1. According to the manufacturer, this column is capable of softening 1000 tons of water (6 m3/h × 24 hours × 7 days). Yet it needs to be regenerated after producing only 300 tons of water – why is that? 2. Are my requirements for water quality too strict? 3. After each salt soaking process, there is a backwash for 2 hours and a forward wash for 1 hour. However, from the first day to the second day of water production, the hardness remains around 0.17 mmol – could this be due to insufficient cleaning? 4. Is it necessary for boiler operators to add sodium carbonate to soft water in order to keep the pH level around 12? 5. I want to add alkali to the incoming water in order to reduce the temporary hardness – is that possible? What base to add? Can I use hot salt water at 80°C when making soak salts? Are there any requirements regarding the pH value of the incoming water for sodium ion exchange columns, and are there any requirements regarding the temperature of the incoming water?
I work in boiler operation, and I’d like to share some insights. According to the standards for testing chemical water, the quality of water that enters the chemical water treatment process should meet the specified parameters for chemical water (please refer to the relevant standards). Since your plant uses groundwater, it’s inevitable that the incoming water will have high salt content, high hardness, and many impurities. Issue 1: This problem is related to the quality parameters of the incoming water； 2. Strict requirements are placed on the quality of water used in boilers to ensure their safe, stable, and economical operation ； 3. It is recommended to improve the water treatment process or to regulate the chemical inputs appropriately according to the requirements of the water treatment equipment ； 4. The quality parameters of the boiler water must be met strictly in accordance with the design requirements. Excessively high alkalinity in the boiler water can cause metal alkali corrosion; it is therefore necessary to follow the relevant standards for boiler water testing and treatment ； 5. I’m an outsider; please let a chemistry professional explain it
Is there any expert who can answer my questions?
After the ion exchange columns in the 10t boiler room were regenerated and used for one day, the levels of calcium and magnesium ions in the water increased significantly. By examining the regular usage patterns of the ion exchange columns as well as the existing auxiliary equipment, it was determined that the reasons for the improper functioning of these columns were as follows: 1. The operating procedures were not followed correctly; the flow rate of the soft water during operation was not properly controlled, and the concentration and flow rate of the regeneration solution were not maintained within the specified ranges. 2. The volume of the regeneration liquid tank is too small, failing to provide enough regeneration liquid for thorough regeneration of the ion exchange resin. 3. The ion exchange column is poisoned by iron ions. Based on analysis and calculation, the proposed treatment method can be divided into two steps: Step 1: Add a regeneration liquid storage tank with a volume of 4 m3, and carry out large-scale backwashing, regeneration, displacement, small-scale forward washing, and normal washing of the ion exchange column in strict accordance with the operating procedures, while observing its operational performance. Step 2: If the ion exchange column still does not function properly after Step 1, the column can be opened to check whether the epoxy resin coating on its inner wall is damaged. If the epoxy resin coating is intact, the column can be safely cleaned using 1–2% dilute hydrochloric acid, thereby allowing it to function properly again ； If the epoxy resin anti-corrosion layer is damaged, it can only be replaced by applying new epoxy resin. To ensure the proper and stable operation of the ion exchange column in the future, it is recommended to strictly control the concentration and flow rate of the regeneration solution in accordance with the operating procedures during use. At that time, I worked on finding a solution for the ion exchange columns in our company. After examining those columns, it was found that the resin had been poisoned and that the anti-corrosion coating inside the columns was severely damaged, requiring re-coating with an anti-corrosive material. After further treatment, it returns to normal, and can be used for half a month each time after birth.
I’m facing the same issue as you. My new company is still in the setup phase; equipment such as 20t boilers is still being installed, and I’m not familiar with the various parameters related to the water softener. I’m also very interested in knowing the answers to the questions you’ve raised.