Sulfuric acid storage tank

Specification of sulfuric acid storage tank: Capacity 0.1-150 cubic meters, thickness 4-16mm.
Types of sulfuric acid storage tanks: vertical, horizontal, flat head, elliptical head, circular, square, conical, flat bottom, circular bottom, inclined bottom, conical bottom, etc
Working conditions: normal pressure or under pressure

1、 Concentrated sulfuric acid storage tank

Concentrated sulfuric acid can be stored in carbon steel and can be divided into dilute sulfuric acid, concentrated sulfuric acid, fuming sulfuric acid, etc. Depending on the concentration, concentrated sulfuric acid with a mass fraction greater than 70% can undergo passivation when encountering iron. Sulfuric acid will oxidize the surface of the steel, forming an oxide layer. Due to the low water content and absence of free ions in concentrated sulfuric acid, the oxide layer will no longer be corroded by oxidation, but a certain amount of corrosion allowance should be left.

1. The corrosion principle of sulfuric acid on carbon steel:
   The corrosion process of carbon steel in sulfuric acid is a typical electrochemical corrosion. The chemical reaction formula is expressed as follows:
   Fe+H2SO4→H2 +FeSO4
   The nature, surface state, cathodic impurities, pH value, and temperature of metal materials can all affect the hydrogen depolarization corrosion of metals.
2. Characteristics of sulfuric acid corrosion
   The corrosiveness of sulfuric acid with different concentrations has the following prominent characteristics:
   At a certain temperature, the corrosion rate of dilute sulfuric acid on carbon steel increases with the increase of concentration; After reaching a certain concentration, the corrosion rate sharply decreases with the increase of concentration.
   Another characteristic of sulfuric acid corrosion is that the corrosiveness of sulfuric acid at the same concentration increases significantly with temperature.
   The corrosiveness of sulfuric acid is not only related to concentration and temperature, but also greatly influenced by impurities in the acid.
   In addition, some physical factors such as medium flow rate, solid particles, scaling, etc. also affect corrosiveness.
   
3. Attention to the use of carbon steel concentrated sulfuric acid storage tanks:

• Attention should be paid to preventing moisture absorption. Desiccant can be added to the breathing line of the concentrated sulfuric acid storage tank, or nitrogen sealing can be added to large storage tanks to isolate water vapor.
• Clean the inner surface of the storage tank thoroughly without leaving too much foreign matter
• When the flow rate of concentrated sulfuric acid is above 0.67m/s, it will cause turbulent corrosion and damage the passivation layer, especially at the inlet and outlet positions of the pipeline

2、 Dilute sulfuric acid storage tank

Due to the high corrosiveness of dilute sulfuric acid even at lower temperatures, it is necessary to use more corrosion-resistant materials, such as 316L stainless steel at certain concentrations and temperatures. However, compared to the high price of 316L sulfuric acid storage tanks, using carbon steel lined PTFE storage tanks can significantly save costs and have a wider adaptability to various concentrations of sulfuric acid. (Refer to the Corrosion Data Manual)

A 20 cubic meter steel lined PTFE dilute sulfuric acid storage tank customized by a chemical plant in Chengdu

Large dilute sulfuric acid storage tank adopts polytetrafluoroethylene plate lining process

3、 Supporting the transportation pipeline for sulfuric acid storage tanks

Carbon steel pipes can transport concentrated sulfuric acid under certain conditions, but the flow rate should be controlled below the critical speed of 0.67m/s. Exceeding this flow rate can cause turbulent corrosion, especially at the inlet and outlet positions of the pipeline. It is recommended to use PTFE lined carbon steel pipes for stronger corrosion resistance and wider adaptability. In the sulfuric acid pipeline renovation of the chemical plant undertaken by our company, after the customer's original sulfuric acid pipeline suffered severe corrosion, it was replaced with PTFE lined carbon steel pipe for more than a year, and the current condition is good.