What is the purpose and function of operating boiler cleaning?

Necessity and significance: After operating for a long time, boilers inevitably develop problems such as scale and rust. The formation of scale reduces heat transfer efficiency, thereby lowering the boiler’s performance. Therefore, it is difficult to achieve the rated evaporation rate ； Furthermore, the reduced heat transfer leads to metal overheating; under the pressure in the boiler, the furnace tubes bulge or even explode ； Poor heat transfer leads to increased fuel consumption, higher operating costs, and a shortened boiler lifespan. Therefore, after scaling occurs in the boiler, necessary methods should be taken to remove the scale. Solution: To ensure that the boiler system operates in an optimized state, it is necessary to carry out specialized chemical treatment on the water system of the boiler system: removing scale and rust as well as applying anti-corrosion measures. 1. Chemical cleaning: Chemical cleaners are added to dissolve and remove any floating rust, scale, and oil deposits within the system, thereby restoring a clean metal surface ； 2. Routine maintenance: Add GR-943C boiler scale inhibitor to prevent metal rusting and inhibit the crystallization and precipitation of calcium and magnesium ions. The cleaning of boilers is carried out in two stages. The first stage involves removing scale and rust from the boiler’s convection tubes, superheater tubes, air preheater tubes, and water wall tubes; in other words, it involves treating the quality of the boiler water. We use GR-943 as a descaling agent, along with GR-201 as a neutral cleaning agent, which makes the process relatively cost-effective ； One part involves cleaning outside the tubes, that is, cleaning the boiler furnace. We use high-pressure water jet cleaning technology, which achieves very good results. The neutral, acid-free chemical cleaning technologies of GR-943 with descaling agent and GR-201 with scale remover have filled a gap both domestically and internationally, representing a leading level in this field; they have brought about a revolution in chemical cleaning and thus initiated a new era of green, neutral chemical cleaning. This technology enables cleaning to be carried out without stopping production, causing no corrosive damage to the equipment. The cleaning waste liquid meets the discharge standards without any treatment, causing no pollution to the environment. Replacing acid cleaning with neutral, acid-free chemical cleaning has become an inevitable trend. 1. Neutral operation cleaning can be carried out under neutral or slightly alkaline conditions (pH value 7–12); it does not alter the **specified operating parameters for the boiler water, and cleaning is done without shutting down the system. This reduces the losses associated with cleaning during shutdowns, and this is the sole characteristic of neutral cleaning. 2. Efficient scale removal: By using descaling agents such as GR-943 and GR-201, which operate on the principle of chemical coordination fields, these agents undergo coordination reactions with Ca2+, Mg2+ in water, as well as calcium and magnesium compounds. This prevents the formation of scale crystals and causes existing scale to gradually decompose, resulting in a gelatinous suspension that is discharged from the boiler. It can remove insoluble scales that cannot be cleaned by acid washing, with a high cleaning efficiency. 3. Safety and no corrosion: Both theoretical research and practical boiler operation have shown that cleaning and descaling under neutral, acid-free conditions results in a corrosion rate that is lower than that of water on metals; thus, no corrosive damage to the metals occurs. 4. Non-toxic, harmless, and pollution-free: The scale removal agents GR-943 and GR-201 are green and environmentally friendly products; the COD, BOD, and pH values of the wastewater from boilers after cleaning with these agents fully meet the **standards. 5. Easy to use: The medication can be added to the water supply; no specialized personnel are required, and it can be operated by regular staff, making it suitable for widespread adoption. 6. It consumes significantly less water; throughout the cleaning process, the water used is equivalent to that required for normal production, unlike acid cleaning which requires a large amount of fresh water for preparing chemicals, passivation, and repeated rinsing. High-pressure water jet cleaning technology uses water as the medium, and through a specialized equipment system, it generates multiple high-pressure water jets with various angles and intensities. Thoroughly cut, crush, compress, and scour the internal scaling, blockages, or surface deposits of the object to be cleaned, in order to achieve complete cleaning. No matter what type of scaling deposit it is – whether it’s rust, iron oxide scale, resin, chemical residues, paint, or epoxy – high-pressure water jet cleaning equipment can remove it completely, revealing the true color of the metal. It requires no chemicals, fluxes, or corrosives, making it safe and environmentally friendly to use. Blockages in the boiler’s heat exchange surfaces such as the air preheater, water wall, superheater, and economizer will lead to an increase in exhaust gas temperature, a decline in boiler efficiency, and higher power consumption for the induced draft fan ； Severe blockage will prevent the fan from creating negative pressure, resulting in insufficient oxygen in the furnace and forcing the boiler to shut down. Using high-pressure water jet technology, the cleaning effect is very significant.

The formation of scale reduces heat transfer efficiency, thereby lowering the boiler’s performance. Therefore, it is difficult to achieve the rated evaporation rate. Moreover, the reduced heat transfer leads to overheating of the metal, and under the pressure in the boiler, the furnace tubes may bulge or even explode. The poor heat transfer also increases fuel consumption, raises operating costs, and shortens the lifespan of the boiler. Therefore, after scaling occurs in the boiler, necessary methods should be taken to remove the scale. II. Design principles for the cleaning system 1. Temporary pipes must not contain sand, gravel, or other debris; the slope of horizontally laid temporary pipes in the direction of drainage must be at least 1/200. The pipeline welding area should be located in a easily observable position. The weld joint should not be located near important equipment. 2. A filter screen with a size of less than 5 mm should be installed at the pump inlet, and the water level in the tank should be at least 2 m above the pump inlet. Prevent cavitation. 3. A temporary level gauge and a level alarm device are installed on the steam drum, and a Φ25 throttle orifice plate is added at the downcomer outlet of the steam drum. 4. A hydrogen vent hole of at least Φ32 should be provided at the top of the boiler drum. III. Preparatory work before cleaning 1. The system has been installed, the water pressure test has passed, and there is sufficient water storage and supply. 2. Ensure an adequate supply of various medications and testing instruments in accordance with technical and safety requirements; install monitoring devices to guarantee accurate medication testing. 3. Equipment and systems that have nothing to do with chemical cleaning should be removed or properly isolated; the superheater should be isolated, as well as the level gauges, instruments, sampling pipes, and chemical dosing pipes. 4. To maintain the temperature of the boiler cleaning fluid, the furnace and the outlet of the tail flue should be sealed. IV. Cleaning Procedure 1. Connect the economizer cleaning circuit: Cut the inlet and outlet pipes of the economizer, and connect hoses, flanges, valves, an acid-resistant pump, and a circulation tank to form a circulating cleaning circuit. 2. Cleaning and passivation of the economizer: First, fill the circulation circuit with clean water to clean it, checking for any leaks; then drain the clean water and inject the “Osk-I” descaling and passivating agent. Circulate the fluid from bottom to top, monitor the pH level and keep it below 1. Heat the mixture using steam to a temperature of 50–55°C, and allow it to circulate for 8 hours. Next, swap the inlet and outlet of the pump and circulate the fluid from top to bottom for 4 hours. After that, pour the remaining liquid from the cleaned economizer into the steam-water separator outlet of the boiler drum, and close the boiler’s blowdown valve. The economizer is then flushed with clean water until the pH level reaches approximately 7. 3. Circulation loop connecting the steam drum and water wall tubes: Connect the pump’s outlet to the outlet of the steam-water separator, with the pump’s inlet being the circulation tank. The main sewage pipe is connected to the circulation tank. 4. Cleaning and passivation of the steam drum, water-cooled tube walls, and header: A circulation method with fluid entering from above and exiting from below is used; the heating temperature is maintained between 50–55°C. “Ganai 98” is injected to keep the pH level below 1. This process is carried out for 10 hours, after which the pump is stopped and the system is left to soak for 8 hours. The pump is then started again for another hour of circulation, followed by the disposal of the waste liquid and thorough rinsing with water.