Purpose of alumination acid washing in packed towers

Purpose: To remove impurities and dirt from the surface of the material, as well as to passivate its surface for corrosion protection.

Acid washing acid washing； pickling ； Acid pickling usually refers to a method for cleaning metal surfaces. 　　Generally, the parts are immersed in an aqueous solution such as sulfuric acid to remove films such as oxides from the metal surface. It is a pre-treatment or intermediate treatment for processes such as electroplating, enamel coating, and rolling. (1) The method of using acid solutions to remove oxide scale and rust from the surface of steel is called pickling. Oxides of iron such as scale and rust (Fe3O4, Fe2O3, FeO, etc.) undergo a chemical reaction with acid solutions, forming salts that dissolve in the acid and are thus removed. Acids used for pickling include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, chromic acid, hydrofluoric acid, and mixed acids. The most commonly used ones are sulfuric acid and hydrochloric acid. The pickling processes mainly include immersion pickling, spray pickling, and acid paste rust removal. The impregnation and pickling method is generally used, while the spraying method can be employed in large-scale production. Steel parts are generally pickled in a sulfuric acid solution of 10% to 20% (by volume) at a temperature of 40°C. When the iron content in the solution exceeds 80 g/L and the ferrous sulfate content exceeds 215 g/L, the pickling solution should be replaced. At room temperature, pickling steel with a 20%–80% (by volume) hydrochloric acid solution does not easily lead to corrosion or hydrogen embrittlement. Due to the strong corrosive effect of acids on metals, corrosion inhibitors need to be added. After cleaning, the metal surface turns silver-white; at the same time, the surface is passivated, enhancing the corrosion resistance of the stainless steel. 　　(II) To eliminate adsorption on the surface of the diatomite carrier and reduce peak tailing, the carrier must be treated with acid or alkali before use. Pickling involves immersing the carrier in 6 mol/L hydrochloric acid for 2 hours, or in concentrated hydrochloric acid at elevated temperature for 30 minutes; thereafter, it is filtered, washed with water until neutral, and dried. Pickling can remove impurities such as iron, aluminum, calcium, and magnesium from the surface, but it cannot remove silanol groups. The pickling carrier is suitable for analyzing acidic samples.

Simply put, pickling is used to remove rust or the oxide layer, while vanadium is used to seal pores, a process also known as passivation. The inspection standards are implemented in accordance with **the standards (which can be consulted)!