Historically the handling and production of chemicals requires specific knowledge, machines and accessories. Chemical companies continuously specialize and optimize their products starting from basic chemicals like chlorine and sulfuric acid to highly complex precursors for the pharmaceutical and plastic industry. This leads to a big number of highly specialized equipment manufacturers. In no other industrial sector the knowledge about processes, potential dangers and liquid properties is as important as in the chemical industry. The continuous exchange between process engineers and pump technology suppliers is the basis of a successful solution to handle the different substances.
No other industry requires such broad varieties of pumps as the chemical industry. In every production step all kind of pump technologies are found, starting at the unloading area of raw materials, their reconditioning area, in all transformation processes, the storage area and finally the related environmental processes of wastewater treatment and gas cleaning.
Basis for the pump technology and material selection is the pumped medium. Chemical and physical properties but also risk and hazard evaluations are important factors. At best, pump manufacturers and planning companies work closely together already at an early stage of the design phase to find a reliable and safe solution.
Successful application examples
For tank and truck unloading applications in the chemical industry centrifugal pumps are often used. Due to the high flow rates and moderate differential heads these kind of pumps brings a huge variety of designs, materials and sealing concepts. Additionally to the chemical resistance, also safety aspects like explosion protection and dry run protection are often important.
In thermal separation processes like distillation liquids are circulated in a continuous substance stream. Next to proper material selection an additional major problem in these applications is the fact that liquids are often pumped close to their vapor pressure. Pumps used in this kind of applications stand out due to their excellent suction behavior (low NPSH requirements).
Washing water streams in flue gas cleaning areas of industrial plants and waste incineration carry a huge amount of critical ingredients and solid particles. Centrifugal pumps which have to deliver high flow rates additionally have to withstand a corrosive and abrasive exposure.
In addition side processes such as lime milk dosing have similar characteristics. The main requirements for suitable and reliable pump solutions are especially a proper material and shaft seal design.
Next to classical water pumps also chemical pumps can be found in industrial wastewater treatment plants. For dosing of lime, hypochlorite or for the collection in a sump pump chemical resistance is a major issue.
The production of chlorine in industrial scale is usually be made by electrolytic separation of sodium chloride (NaCl) and hydrogen chloride (HCl). In most cases the high flow rates are suitable for centrifugal pumps. The corrosive characteristic reduces the number of suitable alternatives compared to other applications. In the salt processing as well as in the electrolysis cell and for sodium hydroxide (NaOH) applications nowadays pumps made from plastic as well as titanium and nickel alloys are used.
Due to its various properties (e.g. for drying of substrate streams) sulfuric acid is a very important substance for process technologies. However, due to its corrosion behavior this acid is a challenge for materials and machines. It´s behavior changes significantly by variation of temperature and concentration. However, it does not follow the rule “higher concentration leads to higher corrosion”. The reduction of concentration can even lead to a more critical corrosiveness. Pumps for sulfuric acid need to be selected based on temperature and pressure followed by a suitable material and seal concept selection.