In an industrial facility, emissions occur at a number of various locations. The Wallstein Group can , design, manufacture, and supply an appropriate scrubber system for any water-soluble pollutant. Depending on the substance, they are either physically dissolved or chemically bonded by adding lye and/or acid and, in some cases, an oxidizing or reducing agent.
Examples of use
1) Glass industry
Mixtures of sulfuric acid, hydrogen fluoride and hexafluorosilicic acid are used for acid polishing of crystal glass. Chemical abrasion of the crystal glass surface produces, along with hydrofluoric acid, gaseous Silicon tetrafluoride (SiF4) which can be washed in a two-stage packed-bed scrubber in an efficient and fail-safe way.
In the first stage, hydrofluoric acid is used to separate SiF4 and convert it into H2SiF6 (hexafluorosilicic acid). This process stage safely prevents formation of silicon dioxide (SiO2) which could otherwise lead to clogging of the packing and droplet separator. The hydrofluorosilic acid can be reused, greatly reducing the volume of sewage.
In order to maintain the hydrofluoric acid emission standards, a second stage is used which, depending on the customer’s requirements, operates either with water in a purely physical process, or chemically through addition of lye.
The reduced volume of sewage is fed to a treatment stage.
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2) Pharmaceutical industry
When pharmaceutical agents are produced, acidic vapors are released which need to be purified before they are discharged into the atmosphere. A packed bed absorption column is used to separate pollutants in an efficient and fail-safe way.
The following photograph shows a complete system with an exhaust air scrubber, liquid pipelines including an instrument panel (on the wall), and a switch cabinet (right). All of these components have been supplied, assembled and commissioned by Wallstein.
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3) Chemical industry
In order to extract tantalum, a rare earth metal, the ore mixture is first dissolved in concentrated hydrofluoric acid (HF), after which tantalum is separated with methyl isobutyl ketone. The highly concentrated HF produced in the dissolving tanks is precleaned through physical absorption in a concentrate scrubber. During this process, a large part of the HF is recovered. Afterwards, the residual gas is separated in the main alkaline scrubber together with low-pollution workshop exhaust air.
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