Articles & Case Studies

Neutralac transforms effluent treatment at Rimex Metals

Posted: Tuesday 8th July 2014

The treatment of effluent has been a major concern for the Rimex Metals Group.

Specialists in metal finishing and architectural metals Rimex produces surface finishes on stainless steel and other metals. The company has manufacturing facilities throughout the world and a global distribution network.

In the UK the company traditionally used low solids content lime suspension to treat effluent which is collected in two separate sumps, one for chromic acid based and the other for phosphoric/sulphuric based effluent.

By replacing the incumbent lime suspension with the high solids content of Neutralac SLS45 from Lhoist UK, the company has made considerable savings and introduced a less hazardous and more environmentally friendly product.

Firstly, the effluent containing chrome is reduced from hexavalent chromium using sodium metabisulphite. The reaction time is pH dependent and works more rapidly under acidic conditions. Due to the sulphate process the pH is controlled to around pH1.3 with hydrochloric acid.

All the effluent is dosed with an aluminium reagent before being neutralised with Neutralac SLS45. This is a two step process, with the final pH being around pH11.5, found to be the optimum pH for the formation of calcium aluminium sulphate oxide. The effluent containing calcium, aluminium and sulphate ions, is then passed through an ultrasonic reactor. The reaction chemistry and kinetics are altered so that the sodium oxide is formed. This material is a very fine precipitate.

Epofloc L1-R is then dosed to ensure heavy metals removal but it also starts the flocculation process. The effluent is them pumped to a lamella settler for separation of solids and liquid. A flocculant is added en route to the lamella.

Phosphate is finally removed by precipitation with aluminium and calcium.

The final results are dependant on dosage rates but they can be as high as up to 99.7 percent for sulphate and heavy metals and up to 99.9 percent for phosphate.

By introducing Neutralac SLS45 reagent costs have been reduced by as much as 20 percent. Adrian Walker, Colouring Division manager of Rimex, is delighted with the results. He said: “We have also made logistical savings because a higher neutralisation equivalent can be transported for less and lower storage volume is needed. In turn this minimizes our carbon footprint by halving the number of delivery vehicles arriving on site.

“Neutralac has proved to be easier to handle, easier to pump and dose and it has eliminated the previous blockages, consequently preventing costly plant downtime.”

He concluded: “Neutralac is a joy to use. Blockages are a thing of the past and the lower number of delivery vehicles reduces my workload considerably.”

Neutralac is safer and easier to handle than caustic soda and other alkali products. Its solid content means high neutralisation potential and it reacts quickly reducing the reagent costs. Unlike other lime based products, Neutralac is free flowing and keeps its liquid qualities making it easy to re-suspend and is low settling.




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