The Cato Ridge site of NCP Chlorchem is utilised for the production of sodium hypochlorite, for the warehousing of chlorine drums and cylinders and for the blending of water treatment chemicals.
NCP Chlorchem operated a chlorine storage depot at the Umbogintwini Industrial Complex. The neighbouring land was earmarked for a high-density retail business and residential type development that was not compatible with a major hazardous installation (MHI) and it was therefore required to relocate the depot.
Several sites were evaluated to determine their suitability for the relocation of the depot. The Cato Ridge area was identified as the most feasible location. Interested and affected parties were involved during the selection process for the site and all stages of the environmental impact assessment (EIA) which took several years to complete.
A positive record of decision (ROD) was received at the end 2008 and the facility was successfully commissioned in October 2009.
Chlorine and Sodium Hypochlorite
Chlorine is utilised for water disinfections purposes including the production of potable (drinking) water; the disinfections of treated wastewater; and the disinfection of swimming pools in order to help minimise the risk of water borne diseases. The depot is being used to supply approximately 85 end users in the KwaZulu- Natal area with chlorine.
Chlorine is a toxic gas and there are risks associated with the transportation, storage and use of chlorine. NCP Chlorchem mitigates these risks by using highly sophisticated safety systems, coupled with its years of experience in the manufacture and handling of this product.
Sodium hypochlorite has two major uses. It is extensively used as bleach (a dilute sodium hypochlorite solution) in domestic households as well as in the pulp and paper industry. It can also be used in the place of elemental chlorine to chlorinate and disinfect water.
Although sodium hypochlorite is more expensive to produce than chlorine, sodium hypochlorite raises fewer safety and environmental concerns. It is recognised that although sodium hypochlorite is widely used for water treatment internationally, South Africa almost exclusively uses chlorine. However it is anticipated that South Africa will most likely, over time, follow international trends in terms of the use of sodium hypochlorite for water treatment purposes. The production of sodium hypochlorite by NCP Chlorchem will support and enable initiatives in this regard.
Full and empty chlorine drums (1000 kg) and cylinders (70 kg) are stored in the depot for distribution. The drums and cylinders are filled at the Chloorkop site, where chlorine is produced using membrane cell technology. The chlorine gas produced is turned into a liquid by compression before being transferred to the drums, cylinders and road tankers for distribution. When filled, these containers will have a pressure of 800kPa.
The filled cylinders and drums are transported to Cato Ridge by road interlink trailers and are off- loaded inside the confines of the warehouse building.
Leaks can occasionally occur with the use of chlorine cylinders and tanks , but NCP Chlorchem has many years of experience in handling these types of incidents. Generally, in the case of packed chlorine products, any leak will most likely occur when the valves are operated by the customer in the normal process of dosing chlorine and, to this extent, the probabilities of a leak occurring in the warehouse at the Cato Ridge site is minimal.
As an integral part of the manufacturing process, cylinders and drums of chlorine are only dispatched from the filling plant at the Chloorkop site once a period of at least 24 hours has passed to ensure that any latent valve leaks are identified, isolated and rectified.
The storage of drums and cylinders of chlorine is in an enclosed facility at the Cato Ridge site. This facility is linked to an emergency system that converts any chlorine gas, which may be released in the event of an incident, into sodium hypochlorite using a Powell Sentry Scrubber.
Manufacturing of Sodium Hypochlorite
The sodium hypochlorite production unit was built, supplied and commissioned by Powell Fabrication and Manufacturing Inc who specialises in the manufacture and supply of sodium hypochlorite plants for the industry.
The physical plant is constructed with the highest quality components available to insure long service life with a minimum of maintenance. The plant is fully automated, and only requires manual intervention under exceptional alarm conditions.
The raw materials used for the manufacture of sodium hypochlorite are caustic soda lye and chlorine, and both of these raw materials are supplied in road tankers from the Chloorkop site in Gauteng.
Raw materials and final products are contained in storage tanks in bundled areas whilst, in addition, all loading and off-loading areas drain into these bundled areas.
The sodium hypochlorite process utilises a unique liquid/liquid reaction that produces high quality bleach at a minimum operating cost and with maximum safety compared to the gas/liquid reaction normally used in other existing commercial processes. The product produced is filtered and cooled before being transferred to one of the product storage tanks, ready for dispatch.
Finished products, both in bulk and pre-packs, are dispatched by road transport.
Safety features included into the plant are in excess of minimum safety levels recommended. The plant is equipped with numerous safety devices, which are intended to shut down the plant if a process upset threatens personnel or product quality.
The Sentry Scrubber unit evacuates and neutralises vapour chlorine that has been contained from various areas of the production facility, if a leak occurs. The captured solution is pumped back into the bleach plant to be converted into the final product bleach once normal operations are again established.
All safety systems and scrubbers are supported by emergency power systems in the event of a power outage whilst all staff of the Cato Ridge site are fully trained in the handling of chlorine emissions from any chlorine container at the NCP Cato Ridge site.
Customers, who may experience problems with chlorine leaks, have the service of an on-site hazardous chemicals team that will ensure that the container is safely sealed before returning it to the Cato Ridge depot. Alternatively, if the application of any specialised safety equipment is required, the NCP Chlorchem Hazchem Team will be dispatched to secure the leaking container and return it directly to the Chloorkop site.
Raw materials and final products are contained in storage tanks in bundled areas. The loading and off-loading area drains into the bund.
Major feedstocks consist of Alifloc, ACH and polyamines and these are used to blend different flocculants.
Final products, both in bulk and pre-packs, are dispatched by road transport.