As part of the efforts to protect the climate and environment, the limits on pollutant levels, hydrofluoric acid and HF have become more stringent in recent years. It is considered highly toxic, contributes to global warming and is partly responsible for the increase in fluorides in the soil and bodies of water. Because fluorine compounds are often found in clays, the ceramics industry is considered one of the main contributors.
If the formation of HF cannot be avoided through appropriate changes to the production process, operators of ceramics kilns, calcining plants and the glass processing industry have to meet these stricter requirements with a correspondingly high-performance HF scrubber. Operators of small to medium-sized facilities in particular are affected by the stricter emission limits. It should be noted that for most of these applications, HF is the only critical pollutant that can be effectively eliminated at a moderate cost. Because of this, Steuler Equipment Engineering has developed a unique HF dry scrubbing process which, thanks to its compact, modular design, can in most cases be cost-effectively installed in close proximity to the kiln itself.
The design of the Steuler HF dry scrubber is ingeniously simple, it is practically maintenance-free, has no mechanical components whatsoever and requires no additional source of power.
The HF dry scrubber unit consists of a simply constructed steel reactor without any moving internals or attachments. It is filled with several layers of dry absorption honeycombs. They are made from a specially developed extruded calcium-hydroxide-based material. The HF-containing flue gas is fed into the reactor and flows through the open lime honeycomb and permeates its porous wall structure. When the gaseous HF comes into contact with the lime structure, a chemical reaction takes place, neutralizing the aggressive acid and converting it into a high-quality, harmless reusable material: calcium fluoride or CaF2.
The dry scrubber regulates itself without the need for expensive automation systems! The HF is reliably and effectively removed simply by dimensioning the highly reactive absorption block according to the operating parameters and maintenance intervals of the kiln. When the absorption block is used up, it can be replaced within a few hours and the dry scrubber can operate again with maximum availability for several months. Depending on plant size and desired uninterrupted uptime, the fresh lime modules can be fitted into the designated steel cassettes prior to use, and lifted in through the open reactor door with a forklift when the time comes to swap them out.
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Advantages of the Steuler HF dry scrubber
- Low capital investment and operating costs
- Compact, modular design often allows for installation in close proximity to the kiln, including when retrofitting, eliminating the need for expensive, failure-prone bulk storage systems
- Temperature range of up to 300°C, which is well above the other HF dry scrubbers on the market based on a fabric filter design
- Lower pressure drop resulting in lower energy costs
- No failure-prone, high-maintenance mechanical components, such as screw conveyors, scraping devices, pneumatic conveyors, etc.
- Automation-free – no expensive control systems that can fail during operation
- High, defined utilization ratio of the highly reactive lime absorber
- The end product, calcium fluoride, is non-toxic and a high-quality reusable material, which if used locally means no additional effort or costs are incurred for disposal.