The plant at Borealis in Stenungsund (Sweden) operates 24 hours a day, year after year. The process is only stopped every six years for service and maintenance to be carried out. Borealis has now replaced the raw gas compressor motor at the cracker plant in order to boost capacity and ensure continuous operation. A 24.5 MW motor will ensure the operational availability of the petrochemical plant.
The Borealis cracker plant in Stenungsund, Sweden’s only location for the production of ethylene, which amongst other things is used as a raw material in plastic production, lies at the heart of the petrochemical hub that the west coast community has become.
The cracker plant converts hydrocarbon chains into smaller components in order to produce the right type of molecular composition, which can then be made into longer plastic chains or other products such as ethylene oxide. Around 400 shipping vessels call at Borealis’ own port in Stenungsund every year carrying hydrocarbons such as ethane, propane, naphtha and butane in both gaseous and liquid form, which are then stored in huge underground caverns, tanks or spheres. In the cracking process, the raw material is heated to 900 °C in one of the nine furnaces, which are as tall as high-rise buildings. At this temperature, the hydrocarbon chains crack and divide into smaller components before being subsequently cooled down to –100 °C in cooling towers.
“The lighter the fractions being separated, the lower the temperature,” explains Samu Salo, Operations Manager of the cracker plant. The refined gases, primarily ethylene and propylene, are then delivered to customers in Stenungsund including Ineos, Akzo Nobel and Perstorp, in addition to one of Borealis own polyethylene factories, which produces polyethylene primarily for use in pipes, wire and cables.
The cracker plant also produces ETBE, an octane-enhancing additive for petrol, in addition to by-products such as fuel gas, which is formed during the cracking process. Some of the fuel gas is used in Borealis’ own furnaces, while the rest is sold.
Continuous Operation for Six Years
The availability requirements of the cracker plant are extremely high. The plant operates continuously without any stoppages. This involves large quantities of hydrocarbons, which must be continuously processed. The plant must operate without fault for years at a time as it is only stopped every six years for a few weeks for maintenance.
An unplanned production stoppage would have major consequences for Borealis and its customers due to the large quantities of hydrocarbons involved.
“It simply mustn’t fail. If the raw gas compressor did stop, everything would stop, and for safety reasons, we would have to burn the product by flaring it, which would result in major financial losses for us,” explains Samu Salo.
The plant would then be quickly forced to burn, or flare, the large quantities of hydrocarbons using the 122-meter high flare that is constantly operational — a huge expense in terms of production losses.
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