The Gorgon project needs no introduction. Located off the north-west coast of Western Australia, it is one of the world's largest natural gas projects, set in an environmentally sensitive area.
To protect the island's unique habitats, stringent environmental conditions have been imposed in terms of air, noise and light emissions, thus making the emission control system absolutely critical to the projects viability.
Luhr Filter, specialists in dust and fume control solutions, were chosen by KMH Environmental to supply an emission control system for a waste incinerator facility serving the LNG processing plant on Barrow Island.
"KMH's preference was for a 'one stop' supplier of the entire pollution control system," says Trevor Baud, the General Manager of Luhr Filters. "This included a heat exchanger which had the added benefit of a compact build to fit in the limited real estate."
"The solution we put forward was tailored to the specific and unique environmental requirements of the Barrow Island project – it was very much about collaboration and innovation to achieve the requisite results.
"KMH were also keen to limit the number of sub-contractors they had to deal with, and we offered them a turn-key plant for the gas cleaning, integrating design and supply of all the equipment."
The Luhr Solution
Luhr Filter has been designing robust solutions for air pollution control in the Australian market for over 30 years; the Barrow Island project joins many other successful projects in a diverse number of industries. All of which required Luhr to provide customised dust and fume control solutions with careful consideration to the nuances of location, industry, environmental requirements, and budget constraints, to ensure delivery of a superior outcome.
The Barrow Island project required that all putrescible waste created on site – from the accommodation camps during construction and eventually, production – had to be incinerated rather than going to landfill. The flue gas from the incinerators had to be treated in order to meet world-class environmental standards for emission of particulate, acid gases, metals and dioxins.
KMH Environmental designed an incinerator system with primary and secondary combustion chambers in modular units to minimise labour requirements on site.
Dry Absorption system
With an impressive track record as a global supplier of incinerator gas cleaning systems, the Luhr dry scrubbing systems were selected as the preferred technology for the job.
The dry absorption system integrates Luhr's unique technologies for heat exchangers, absorption reactors, utilisation of the absorbent and the baghouse style filters with reverse pulse bag cleaning.
The first stage of the gas cleaning system is a compact Luhr flat tube gas-to-air heat exchanger. Flue gas from the incinerator stack passes on the outside of the flat heat exchanger tubes at low pressure loss with cooling air being fan forced through the tubes.
The absorbents – hydrated lime and pulverised activated carbon – are supplied premixed in bulk bags and injected pneumatically into the gas stream upstream of the absorption reactor. The Luhr absorption reactor allows sufficient residence time for the first stage absorption of the gas pollutants. Coarse and agglomerated particles are milled or disintegrated when passing through a drum partly filled by grinding spheres, until the size is sufficiently reduced for the fines to be carried by the gas stream into the dust collector.
The bag house filter collects the fly ash and completes the gas absorption in the filter cake on the bags. The filter is cleaned sequentially with pulses of compressed air reversing the gas flow through the bags. The main portion of the removed dust cake – ash and partly reacted absorbent – is recirculated by screw conveyors to the inlet of the absorption reactor, where the absorbent is reactivated in the milling drum. Several recirculation cycles ensure that the absorbent capacity is fully exploited. Since a large amount of absorbent is held in circulation, a surplus is always available to cater for peaks in the stream of pollutants.
This unique system of recirculating and discharging the reacted absorbent by mechanical means, combined with reduced heat losses through thermal insulation and trace heating, ensures reliable operation of the solids handling plant. The baghouse type dust collectors are supplied to site sub-assembled with the horizontally mounted Luhr flat bags installed. The compact build of these dust collectors has multiple benefits – facilitating transport to remote sites and reducing overall plant size.
A fan downstream of the bag filter provides controlled draught for the incinerator and the gas treatment system and discharges the gas to the stack. Collected incinerator fly ash and spent absorbent is discharged from the bag filter hopper.
Luhr Filter is currently supplying two similar pollution abatement systems for Exxon's LNG exploration and production facilities in PNG, to go on stream by mid 2012.
"Luhr's dry absorption system is favoured by the chemical, oil and gas industries because their projects usually require some form of customisation," says Baud, "and that's what we specialise in."