Hydrofluoric acid neutralised: Disposal bottleneck for uiquicl special waste elimination

A state-of-the-art plant for neutralising (highly) toxic liquid production residues, which was also planned according to the latest safety standards, started operation near Leipzig (East Germany) last year after taking just six months to build. This especially alleviates a bottleneck in the disposal of hydrofluoric acid caused by increasing demand for products in various industries.

Foto: Lobbe
(01.06.2010) Hydrofluoric acid is used especially in solar cell and chip production to etch silicon surfaces. Q-Cells in Bitterfeld-Wolfen, Germany, is an important customer. Handling hydrofluoric acid is extremely complicated. This new plant provides the industry a reliable method of disposal that fulfils the highest safety standards. Thirteen specialist authorities were involved in the approval procedure to coordinate the conditions regarding immission control, waste, water, occupational safety, building and fire protection regulations. The supervising authority is the Leipzig Regional Administrative Authority (Regierungspräsidium).
About 24 tons of acid can be neutralised each day in the new plant. By the middle of 2009 the plant will be extended to cope with 72 tons of acid. The centrepieces are seven treatment reactors in which the acid is neutralised. The actual process is fully automatic. The entire plant, which Lobbe Industrieservice planned and built at the operating location in Espenhain, is controlled by computer and monitored by CCTV cameras. The company invested roughly three million euros in the new technology; more than 1.5 million euros of this was spent on technical safety precautions. The approved plant has now also been certified according to the German Federal Immission Control Act (BImSchG).
Lobbe now provides capacities for approximately 210,000 tons per year to treat liquid hazardous waste throughout Germany. Espenhain, where other liquid production residues such as nitric acid, hydrochloric acid and sulphuric acid as well as potash lye and nitrite-based lyes can be treated, handles 10,000 tons of this. Over the last years, Lobbe has also developed other special plants to treat soil containing heavy metals.
The new treatment technology created some technical planning challenges for the isometric projections of the piping system, which consists entirely of extremely high-quality media-resistant plastics. Right from the outset the aim was to be able to treat different acids and lyes parallel to each other, if necessary, under capacity utilisation and cost effectiveness aspects. From an organisational aspect, threefold acceptance control and individual sampling ensures that the materials cannot be mixed when they are received. The liquid residues are pumped to the respective reaction tanks via three pump stations. The pumps are clearly allocated to the tanks so that again it is not possible to mix the materials. The plant sections are rinsed neutral after every change of batch.
The acids and lyes are neutralised according to stringently defined parameters. During the process, the temperature gradients and the reactive behaviour are very important and must remain within very specific "windows". Absolutely safe operation is guaranteed through continuous temperature control in the stirred tanks and safeguards that switch the receiving pumps off if values exceed set limits. The neutralisation process, which leaves only sludge and water in the end, is completed when the target concentration is reached. The sludge is initially pumped into a receiving tank and from there into the chamber filter press. The water is pumped into a storage tank where it is analysed and then pumped to other treatment systems, depending on the result of the analysis.
Gases form in the reactor tanks during the neutralisation process. They are cleaned in a high-performance gas scrubber which replaces the air in the hall several times during this process with a capacity of 8,000 cubic metres per hour. The pollutant components of the ambient air are drawn through neutralisation fluids where the pollutants are absorbed. Optimum substance exchange is ensured because of the exceptionally large contact areas. A highly effective drip and aerosol separator stops the liquid being carried out with the cleaned air flow.
In general, it is assumed that the market for photovoltaic products will continue to grow and as a result, the need for process solutions is likely to increase. Lobbe Industrieservice will adapt its transport logistics to take account of the larger volumes of waste in Central Germany by putting a so-called "high-safety suction-pressure vehicle" into service around the middle of the year. It has a 12 cubic metre reactor with a special steel alloy. 90 per cent of all acids and lyes will be transported in this vehicle which can independently draw in the materials and pump them out again.
From a strategic aspect, Lobbe especially plans to develop the potentials in the areas of industrial service, hazardous waste disposal and environmental remediation in the chemical and petrochemical industries into a separate competence profile. According to Managing Director Dr. Reinhard Eisermann, over the coming years it will be necessary to anticipate the customers' future needs. New production technologies will also place new demands on modern service providers like Lobbe. Therefore, market observations and market analysis coupled with a functioning innovation management system will be needed more than ever, while the same applies to careful selection of skilled employees. Lobbe is currently able to choose from a qualified pool of engineers and chemists in Central Germany, mainly from the former GDR chemical companies. Consequently, the plant in Espenhain was realised exclusively with the company's own experts.
Hydrofluoric acid
 ... is the aqueous solution of hydrogen fluoride (HF). Hydrofluoric acid is a colourless, pungent smelling liquid that attacks glass severely and has a very corrosive effect on the skin, mucous membranes and the conjunctiva. A solution of 38.2 per cent HF in water forms an azeotropic boiling mixture with a boiling point of 112°C. Depending on the concentration, hydrofluoric acid is kept either in plastic tanks made from PTFE (Teflon) or in stainless steel tanks. Hydrofluoric acid is the most commonly used etching fluid in computer chip production and is also used in electroplating, façade cleaning and to dissolve quartz crusting on fluorites. Hydrofluoric acid is also used to refine petrol according to the so-called alkylation process. Hydrofluoric acid is a strong contact poison that is immediately absorbed by the skin. Because of this, underlying layers of tissue and even bones can be burned without any sign that the skin is damaged. Hydrofluoric acid damages the nervous system.

Author: Jörg Mueller, Lobbe Industrie-Service GmbH & Co KH, Iserlohn, Germany
Foto: Lobbe

Copyright: © Deutscher Fachverlag (DFV)
Quelle: Entsorga China 01_2010 (Juni 2010)
Seiten: 2
Preis inkl. MwSt.: € 0,00
Autor: Jörg Mueller

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