The process flow of citric acid in boiler pickling generally includes the following steps:

1. Preparation

① System inspection: carry out a comprehensive inspection of the boiler and related systems to ensure that the equipment is intact and there is no leakage and other problems. Close the valves that have nothing to do with the pickling, connect the pickling pipeline to ensure that the sealing of the pickling system.

② Drug preparation: according to the volume of the boiler and scale conditions, calculate and prepare the required citric acid, corrosion inhibitor, co-solvent and other drugs. The general concentration of citric acid is 2% - 4%, the amount of corrosion inhibitor added according to its type and instructions to determine, usually 0.1% - 0.3%.

③ Water quality testing: water quality testing of the water used to prepare the acid to ensure that the water quality meets the requirements, to avoid impurities in the water to affect the effect of pickling or damage to the boiler.

2. Water flushing

①Start the flushing pump: inject enough demineralized water or softened water into the boiler, start the flushing pump and circulate the water in the boiler system for flushing. The purpose of flushing is to remove dust, sand and other loose impurities in the boiler, and check the water flow and sealing of the system.

② monitoring water quality: in the flushing process, the regular collection of water samples for testing, monitoring the turbidity of the water quality, pH and other indicators. When the turbidity of the water samples to reach a certain standard (such as less than 10NTU) and pH value stabilized in the neutral or so, flushing qualified.

3. Acid washing

① Preparation of acid solution: add citric acid, corrosion inhibitor and water in the cleaning tank according to the calculated ratio, mix well and prepare the acid cleaning solution. Then slowly inject the acid solution into the boiler system to ensure that the acid solution is evenly distributed in the boiler.

② Circulation pickling: start the pickling pump to circulate the acid in the boiler system. During the circulation process, control the temperature of the acid solution at about 80 - 90 ℃ to improve the effect of pickling. At the same time, the concentration and pH value of the acid solution are tested regularly, and citric acid is replenished in time according to the test results to keep the concentration of the acid solution stable. Pickling time is generally 3 - 6 hours, the specific time is determined according to the thickness and nature of the scale.

③ Observe the pickling situation: During the pickling process, observe the pickling situation in the boiler through the observation hole or sampling port, such as the color change of the acid solution and the dissolution of scale. If it is found that the scale dissolves slowly or the concentration of acid decreases too quickly, the reasons should be analyzed in time and take appropriate measures.

4. Rinsing after pickling

① Acid discharge: after the end of acid washing, the acid in the boiler will be discharged to the specialized waste acid treatment pool for treatment. In the process of discharging acid, attention should be paid to prevent the acid from leaking and causing pollution to the environment.

② water flushing: after the discharge of acid, immediately inject demineralized or softened water into the boiler for flushing. Flushing, start the flushing pump, so that the water circulates in the boiler system, until the discharged water pH value of 6 - 7, and the citric acid content in the water is less than the specified value (such as less than 0.1%), flushing qualified.