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BASF Seal Sands is a major producer of Acrylonitrile (AN). AN is used principally
as a precursor in the manufacture of synthetic polymers, especially acrylic
fibres and nylon. The chemical is made up from the elements Carbon, Hydrogen
and Nitrogen, and is a colourless liquid which is both flammable and toxic.
AN is produced using Propylene (a gas derived from oil), Ammonia (a substance
found in some household cleaners) and Oxygen (from the air). These gases
react to form AN using particles of catalyst (fine sand grains with a special
coating) at a temperature over 400°C.
World-wide, 5 million tonnes of AN are produced each year. Over half
of this is used to make acrylic fibres, which are used to make clothing
and carpets etc. A further third is used to make durable plastics such as
Acrylonitrile Butadiene Styrene (ABS) or Styrene Acrylonitrile (SAN). These
can be used in pipes and fittings, cars, telephone and computer casings
and packaging.
Of the AN which BASF Seal Sands manufacture, a large proportion is used
to make Adiponitrile (ADN) and Hexamethylenediamine (HMD) (which are intermediates
for nylon), while the balance is shipped to other chemical plants to make
plastics or fibres.
The Challenge – Saving Water in Quench
to Drain & Flush Applications
In the past, BASF Seal Sands mainly used mechanical seals supported with
the quench to drain method (API Plan 62) or the flush method (API Plan 32).
As discussed previously, these methods can waste vast quantities of water,
which incurs costs in terms of purchasing the water and then treating it
to bring it to the minimum required site standard. All of the water used
via API Plan 62, plus water ingested into the process via API Plan 32 (which
potentially may need removing by way of evaporation), is treated in an effluent
plant before disposal. To compound the costs, BASF predominantly use treated
water (de-mineralised water), which is more expensive than standard potable
water, and therefore the cost of using the quench to drain and flush methods
were even greater.
BASF employ AKER KVAERNER as a Pump Management Team.
The Pump Management Team identified that the water usage and poor support
of the existing mechanical seal unit were leading to unsatisfactory reliability
and low MTBF. AESSEAL plc were tasked to propose a solution.
AESSEAL plc proposed solutions to replace a number of original sealing
arrangements seals with double mechanical cartridge seals in conjunction
with water management systems. The closed loop thermosyphon system provided
the water and effluent savings, whilst the controlled constant positive
barrier fluid pressure provided a clean, lubricating, fluid film to the
mechanical seal faces. The water saving, effluent saving, increased MTBF
and zero product emission tasks were achieved.
In just 16 pumping applications, by July 2004, AESSEAL plc had helped
to save 60,217,600 litres (15,907,810 gallons) of water. An example of how
one application helped to save this huge amount of water is shown:
In this single application:
WATER SAVINGS
2,102,000 litres per year /
555,289 galls (US) per year
MAINTENANCE SAVINGS
£865.00 per year / €1,297.50 per year /
$1,557.00 per year
TOTAL COST SAVINGS
£1,285 per year / €1,928 per year /
$2,313 per year
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