Wednesday, April 6, 2011

Whangarei Oil Refinery

NZ’s only oil refinery is located at Whangarei Head- an area deemed to be geologically stable and conveniently located.  Tankers from the Far East, Indonesia, Australia, and NZ deliver up to 130,000 tons per load- enough to run the refinery for 10 days.  The crude is stored in 2 mil gal and smaller tanks. 
From there it is boiled and the resulting gas is pumped to the distillation columns where its various components condense onto trays.  Products with high boiling points, such as residue, heavy gasoil, and light gasoil cool quickly and condense low in the column.  Higher in the column kerosene, gases, TOPS, and naphtha are deposited on trays.  Light and heavy gasoil will be refined into diesel, kerosene becomes jetfuel, and TOPS and naphtha become petrol.
From here the products are forwarded to desulphurization plants.  Under heat and pressure in the presence of a hydrogen catalyst, sulfur is separated in the form of toxic H2S gas. 
Next, the platformer utilizes a platinum catalyst and hydrogen to raise octane levels from around 50 to standard 91 and 95 petrol levels. 
Elsewhere, the Long Reside from the original distillation column goes through the most complex series of treatments.  First, it is pumped to a High Vacuum Unit, where  Waxy Distillate and Vacuum Gasoil rise up a column under vacuum conditions, and leave Short Residue at the bottom of the column.  This Short Residue goes to the Butane De-Asphalting Unit, where it meets a counter flowing stream of hot Butane.  The lighter components are absorbed into the butane and leave the top of the column.  Heavy asphalt components remain.  These are further distilled in a High Vacuum Unit to produce Bitumen.
The plant features a hydrogen manufacturing unit where a catalytic furnace combines butane, plat former gas, and steam to produce hydrogen gas.  A byproduct of this process is CO2 gas, which is sold for soft drinks. 
The Hydrocracker is the heart of the refinery.  Inside four giant reactors, under great pressure and heat, long hydrocarbon chain molecules are broken down (‘cracked’) into shorter chians.  This process turns  the heavy waxy feed into petrol, kerosene, and diesel components. 
Waste sulfur dioxide gas form various processes is transmuted to liquid sulfur, which is transported by road tanker to a Whangerei plant where it is used in the manufacture of fertilizer.  Old systems recovered 96% of sulfur, and new improvements have upped that number to 99.8%.  In order to depressure the plant, gases are disposed of safely using 90m high flare stacks, where a pilot flame burns continuously. 
End products are pumped down the 10” Auckland pipeline at the rate of 400,000litres/hour. 
The New Zealand Refining Company Ltd is one of the biggest employers in the Northland area, with 300 staff and up to 180 contractors on site. 

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