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Non hazardous alternative to caustic soda Neutralac SLS45 produced by Lhoist

The world’s first non-hazardous alternative to caustic soda for the neutralisation of acidic wastewater – Neutralac® SLS45 – is now in full production in the UK.

Neutralac® SLS45 was developed for the treatment of acidic effluents and the removal of pollutants in the wastewater and effluent treatment sectors by Lhoist, the leading lime producer, which has 89 manufacturing plants in 21 countries.

Neutralac® SLS45 is a direct replacement for caustic soda (sodium hydroxide) and can be used in all existing caustic soda silos and pipework on site. Yet it is non corrosive and offers long term price stability. It is in free flowing liquid form and has the same strength and properties of caustic soda. It is a highly reactive and environmentally friendly neutralising and condition alkali suspension.

The Neutralac story started in 2006 at a Lhoist’s main R& D facility in Belgium. Scientists and researchers developed a hydrated lime suspension that exactly matched the 45% solids level of caustic soda. Previously, the typical hydrated lime solids percentage of a lime based neutralisation agent would be around 18 per cent – not strong or efficient enough to meet the demanding needs of the wastewater and effluent treatment sectors.

The researchers achieved this breakthrough by subjecting the suspension to a series of processes, including hydraulic procedures, the innovative use of milling and grinding equipment and the introduction of additives. The process is covered by patents to prevent inferior copycat products coming onto the market.

A pilot production plant was set up in Germany, mainly to supply Neutralac® SLS45 to the German car makers who needed bulk supplies of a neutralisation agent offering top quality cleaning and flocculation characteristics without the health and safety hazards presented by caustic soda.

As the wastewater and effluent treatment sectors caught on to the benefits afforded by Neutralac® SLS45, so production plants were set up in France and the US. But the UK plant, which came into full production stream in November 2009, is the world’s largest Neutralac® SLS45 plant. It is based in Buxton, Derbyshire which has vast deposits of highest grade lime, vital to the production of Neutralac® SLS45. It is by far the largest Neutralac® SLS45 plant in terms of capacity.

Let’s look at the problems caustic soda presents in the wastewater and effluent treatment processes and how Neutralac® SLS45 addresses these.

First and foremost, producers are becoming more concerned about the risks presented by caustic soda. As legislation in the health & safety sector continues to tighten, so producers are seeking a non hazardous solution which offers all the benefits and characteristics of caustic soda. Neutralac® SLS45 has a much lower risk potential for both users and equipment compared to the corrosive properties of caustic soda and similar sodium hydroxide-based materials. Being non corrosive, any splashes or spillages present no threat to operatives. This means the plant operator can save money on protective clothing and takes comfort from the knowledge that it has greatly reduced the threat of health and safety breaches. Plant and equipment, including storage silos and pipework, also need much less maintenance and have a much longer life due to the non corrosive nature of Neutralac® SLS45.

Long term price stability is another benefit offered by Neutralac® SLS45. Caustic soda, being a by-product of the production of chlorine-based products in plastics manufacture, cannot offer price consistency. Like any commodity, its price fluctuates depending on supply and demand for plastics. This can fluctuate by as much as 150% over a relatively short time frame. Purchasers of bulk caustic soda therefore cannot accurately budget for future pricing and profitability if one of their main raw materials – caustic soda – is subject to wide price fluctuation. The price consistency of Neutralac® SLS45 enables Lhoist to provide its customers with longer term fixed price contracts which not only help them to plan for the future but also reduces the associated reagent cost for flocculent and polymer products.

UK manufacture of Neutralac® SLS45 means that users have assured delivery with a much reduced risk of their production process being interrupted through lack of raw material. It ensures both consistent product quality and delivers the ability to rapidly adjust production capacity to meet changing market needs. There are logistics and environmental benefits to UK production, too, because a higher neutralisation equivalent can be transported for less and a smaller amount of storage is needed. This minimises the carbon footprint of companies by halving the number of delivery vehicles arriving on site.

The ground-breaking feature of Neutralac® SLS45 is its high strength, with a solids proportion of 45 per cent. This gives it an extremely high neutralisation potential, at least equal to that of caustic soda. The industry standard KIWA test, to measure the reactivity of re-agents, demonstrates its speed of reaction and performance equivalence to caustic soda in terms not only of neutralisation potential but also its reaction speed. Such is this speed of reaction that it reduces the need (and cost) of other reagent additives.

Physically, Neutralac® SLS45 is almost water-like, unlike the normally high viscosity of (lower strength) milk of lime. It is free flowing and keeps its liquid properties meaning it is easy to re-suspend and is low settling. Its low viscosity ensures good dispersion and pumpability. Not only does it perform well for acid neutralisation, it also offers more efficient heavy metal precipitation than caustic soda. By increasing the filtration performance, it naturally aids the process of flocculation (clumping) of solids and fats without the need to add additional chemicals, a further time and cost saving benefit to the user. The end result of this is a higher solid content in the residual filter cake making for easier removal and disposal.

Users immediately benefit from an easy-to-use, field-tested product than can be instantly substituted for their existing alkali products. However, users can take advantage of Lhoist’s’ technical expertise tailored to each individual application to ensure the highest degree of production efficiency and low dosage cost-effectiveness before "taking the plunge". Lhoist can survey customers’ plant, process and materials used and carry out an on-site assessment of alkalis used. A field trial storage and dosing unit can be installed for use in parallel with existing systems, allowing user to transparently validate the efficiency of Neutralac® SLS45. When the user does specify Neutralac® SLS45 for the main plant he can then take advantage of Lhoist’s extensive after-sales service and support.

The benefits of Neutralac® SLS45 in action are demonstrated at Enfield-based Rimex Metals Group specialist in metal finishing. Rather than use caustic soda it had traditional used low solids content lime suspension to treat effluent. By replacing the incumbent lime suspension with the high solids content of Neutralac® SLS45, Rimex has made considerable cost savings and introduced a less hazardous and more environmentally friendly product. Treatment processes involving Neutralac® SLS45 lead to final effluent treatment and separation results as high as 99.7% for sulphate and heavy metals and up to 99.9% for phosphate.

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