Wet dust collector

For wet dust removal of boiler flue gas, due to the severe acidic corrosion and wear caused by the flue gas, using a marble water film dust collector yields very good results. 1 Basic components and properties of acid-resistant mortar materials. Acid-resistant mortar is prepared from water glass and acid-resistant cement. The water glass commonly used in construction in China at present is sodium glass; its chemical composition is silicic acid (Na2O·nSiO2), and the value of n in the molecular formula is known as the water glass modulus. Modulus = (SiO2 content × Na2O molecular weight) / (Na2O content × SiO2 molecular weight). The higher the modulus, the greater the viscosity, and correspondingly, the lower the solubility. The water glass commonly used is an aqueous solution of solid water glass, with a Baumé degree of roughly 24° to 48° (and a specific gravity of about 112 to 115). Sodium silicate has good bonding properties, is non-flammable and corrosion-resistant, and possesses high acid resistance (except against hydrofluoric acid, fluorosilicic acid, hot phosphoric acid above 300 °C, and higher fatty acids); it is however not resistant to alkalis. Acid-resistant cement available on the market generally consists of ground quartz sand or crushed natural rhyolite, along with a setting accelerator in the form of sodium fluosilicate (NaSiF6). The hardening of this acid-resistant paste occurs when water glass reacts with sodium fluosilicate, resulting in the formation of silica gel, as well as Na(OH), HF, and NaF. Subsequently, HF reacts with Na(OH) to produce NaF and water. 2 Preparation of acid-resistant mortar: Acid-resistant mortar uses water glass as the main binder. The modulus of the water glass solution used to prepare this mortar should be between 216 and 218, while its Baumé degree should be 45° (with a specific gravity of around 114). If the modulus of water glass is too low (e.g., below 214), curing occurs too rapidly, with a curing time of less than 20 minutes, leaving insufficient time for operators to carry out the construction tasks. If the modulus is too high (e.g., above 3), curing is too slow, which hinders the construction process. Sodium silicate should be stored in a sealed container to prevent reaction with CO2 in the air. Sodium fluosilicate is supplied along with acid-resistant cement, and its purity should be no less than 90–95 %. Store in a dry place; the humidity level during use should not exceed 1%. If the moisture content is too high, it needs to be dried before use, with the drying temperature kept below 60 °C. For acid-resistant powder materials (quartz powder, diabase powder), the humidity level must be no more than 1%, the acid resistance rate must be above 94%, and the fineness requirement is such that the residual weight on screens with 4900 pores/cm2 and 1600 pores/cm2 must be no more than 5% and 15–30% respectively. The recommended weight ratio for preparing acid-resistant mortar is as follows. Acid-resistant powder mixture: Sodium fluosilicate, water glass, (quartz powder or diabase powder) (100% purity): 100 : 515–616 : 37–44. The amount of sodium fluosilicate is generally 15% of the amount of water glass; if the purity of sodium fluosilicate is not 100%, the dosage is increased proportionally. First, mix the acid-resistant powder with sodium fluosilicate evenly, then gradually add water glass while stirring; the entire mixing process should be completed within 5 minutes. The amount mixed each time depends on the number of workers involved in the construction and the speed of work; it should be used up within about 30 minutes (when it starts to set after around 30 minutes), after which new mixture should be prepared. 3 Key Technical Measures During Construction The key to applying acid-resistant mortar is \"drying\", as its curing process involves the gradual dehydration of the formed Si(OH)4. During construction, special attention should be paid to waterproofing, moisture prevention, keeping things dry, and dry curing. This is often the main factor that determines success or failure. Appropriate measures need to be taken for this. 1) Since dust collectors are generally located on the ground floor of buildings, and the floors and walls on that floor are relatively humid, water can easily cause capillary action through the pores in soil, bricks, stones, and concrete. To prevent these phenomena from occurring, two measures can be taken. First, during construction, a deeper drainage ditch is dug along the exterior wall to allow water from the surrounding soil to flow into this ditch and be drained away, thereby reducing the moisture content in the soil and thus minimizing the source of humidity in the indoor floors and walls. Second, when building brick walls, a waterproof mortar should be used to create a moisture-proof layer. A layer of asphalt membrane waterproofing is installed under the concrete floor to cut off the source of moisture. 2) Before construction, the windows can be sealed using materials such as bamboo*, which helps to reduce the entry of humid outdoor air and facilitates the expulsion of water vapor generated by heating inside the room. 3) Construction is preferably carried out during the dry seasons, but regardless of when it is done, indoor heating and drying should be carried out in advance. The duration of drying varies depending on various conditions; generally, it is sufficient when the back side of the interior walls is dry. Of course, if time permits, the drier, the better. It is best to use a dust-free heat source, such as an electric furnace. 4) It is best to pre-mark or outline the exact position of each tile on the surface of the laying layer according to its size, so that the tiles that need to be cut can be prepared accordingly. This facilitates the workers to carry out operations in an orderly and continuous manner. 5) The selected tiles should be cleaned and dried before construction. 6) Construction workers should wear clean work shoes when entering the building, and those mixing materials should wear masks (sodium fluosilicate powder is toxic). 7) When laying acid-resistant tiles, it is required to use the grout extrusion method to lay them and expel air. The construction thickness of acid-resistant mortar should be kept at around 8 mm. 8) The room temperature during construction should be around 20 °C. 9) Acid-resistant mortar requires dry curing; moisture must be strictly prevented from entering it, and it must not be washed with water for cleaning the floor. If allowed to cure naturally at a room temperature of 10–20 °C, it takes about two weeks. When the room temperature is between 20 °C and 30 °C, it takes about a week. If the room temperature is below 10 °C, heating during curing is necessary; this not only accelerates curing but also dries the air, which facilitates curing. The optimal room temperature for curing is 30 ℃ to 35 ℃, which allows a curing time of only 3 to 5 days. The reason is that as the temperature rises, the solubility of sodium fluosilicate increases, which accelerates the curing of the acid-resistant mortar and enhances its strength. Is it true that the higher the maintenance temperature, the better? No. When the temperature rises to 60 ℃–80 ℃, the acid-resistant mortar solidifies very quickly; however, the shrinkage resulting from this rapid solidification, combined with the thermal expansion of the tiles, causes the tiles to become loose and fall off. After the curing process is completed in low temperatures, the heat source cannot be removed suddenly; a rapid drop in temperature can also cause separation due to uneven temperature contraction of various materials. 10) After the curing of the mortar is complete, it should be treated with an acid solution of 40%–50% concentration (or 15%–25% hydrochloric acid, or nitric acid at around 40% concentration can also be used). Because in acid-resistant mortar, only about 70% of the water glass reacts with sodium fluosilicate. Acid treatment can react the excess water glass to form sodium sulfate that precipitates, thereby creating a good silicate paste and **improving water resistance. Each acid treatment resulted in the precipitation of a white sodium sulfate powder. Before the second acid treatment, the sodium sulfate powder that precipitated in the first step must be brushed away completely. The interval between each acid treatment should be at least 5 hours; 8 hours is generally a suitable duration, as otherwise the acidification reaction from the previous treatment will not be complete. Generally, 4 to 5 acid treatments are sufficient. The above methods have been developed through years of practice, research, and experimentation, with continuous efforts to improve them; practice has proven them to be successful. The above section on cement is excerpted from Anonymous’ “Application of Acid-Resistant Cement in Power Construction,” and it is quite detailed. The same principle is applied in the construction of marble water film dust collectors for boilers, and the actual results are very good.

How to calculate the dust collector? Why isn’t it there?

It is recommended to look up a manual on dust collectors or similar materials; there are several types of wet dust collectors, and the calculation methods vary as well. 3# wull1981

Acid-resistant cement is expensive and difficult to apply, so some people use diabase + silica powder + water glass to prepare acid-resistant mortar, which is then used for grouting after the marble has been laid in place.