The pH value of the boiler feed water is too low

Boiler feed water with such a low pH can cause serious problems. First, check the pH of the water at the outlet of the mixed-bed reactor and at the outlet of the deaerator; if it is low there as well, there may be a problem with the mixed-bed reactor or even the anion exchange resin bed upstream of it. Also, check the level of total organic carbon (TOC) in the water to see if it is high; a high TOC level can result in the formation of acidic substances upon decomposition or degradation. Make sure the amount of alkali added is sufficient to maintain the required pH range for the water supply. The boiler pressure is also not low, and it is dangerous when the pH level tends to be low.

During a visit to a facility, it was observed that the chemical water station produced qualified deionized water. Before this water was supplied to the boiler deaerator, an ammonia addition system was used to adjust the pH value of the chemical water. I’m not sure if your boiler feed water is equipped with an ammonia addition system (it’s being studied* for boiler water).

Start by investigating at the source to determine the real reason for the low pH of the water supply, and then find solutions to address that reason. I believe there are always more solutions than problems.

It seems that the water produced by reverse osmosis is acidic, with a pH value below a certain threshold; this definitely causes corrosion to the equipment. Therefore, in order to control the pH value, ammonia must be added for adjustment! As for the deionized water, it might be better to add a decarburizer to remove carbon dioxide from the water. Individual deception

When the pH value of the feedwater is lower than 7 due to improper control, the feedwater becomes acidic, causing acidic corrosion to pipes and equipment; the corrosion product, iron oxide, also enters the boiler water. Both the condensate pipes and the feedwater pipes are made of carbon steel; due to poor airtightness of the condenser, inadequate deoxidation in the deaerator, as well as reasons related to the start-up and shutdown of the unit, it is inevitable for rust to enter the boiler along with the feedwater. Especially in the early stages after restarting the unit after it has been shut down, the iron content in the feedwater is relatively high. The two cycle flushes at the beginning of startup in stream boilers are specified to remove rust and reduce the iron content in the boiler water. In areas of the boiler’s evaporation surface where the heat load is high, such as the fire-facing side of the water wall at the flame center, iron scale forms. The rate of scale formation is proportional to the square of the heat load. By cutting open the water wall tubes, it is evident that more scale accumulates on the fire-side of the water wall tubes compared to the backfire side. Since the thermal conductivity of iron scale is lower than that of metal, it raises the temperature on the surface of the water wall tubes, causing them to bulge and expand, eventually leading to tube rupture. Additionally, underscale corrosion forms beneath the scale, accelerating the damage to the water wall tubes.

We want to add an ammonia addition device, but there is no supply of ammonia in our area, and purchasing it in reagent grade is quite expensive. There are still some troubles.

For a 50t/h chemical water plant, 4 50L liquid ammonia tanks are sufficient for adding liquid ammonia. The turnover is no problem.

4 50L liquid ammonia tanks? Is an ammonia compressor needed to maintain the pressure in the liquid ammonia tank?

Adjusting with ammonia – well, it’s quite difficult to get the value between 8.8 and 9.2. It’s okay though; it seems there aren’t any other good methods either

Can it be adjusted using hydrogen, oxygen, and sodium hydroxide? President Shen?