2010 CHE4170 - Timoleo Gas and LNG Plant Video
CADDAM Engineering, in conjunction with the Timor Leste Government, would like to present the design proposal for the Timoleo Gas and LNG Plant.
Located on the southern coast of Timor Leste, in the Viqueque district, this natural gas processing plant will provide economic and social benefits to the Timorese people. These include - local employment and the establishment of a nation wide natural gas network. The 1.2 square kilometre area provides an industrial space for a combined cycle power station, liquefaction, ethylene and gas processing plants.
The plant is to provide 3 Mega Tonnes per year of liquefied natural gas to the adjacent liquefaction plant as well as produce 200 Peta Joules of sales gas per year, of which, 60% will be diverted to the neighbouring combined cycle power station. Furthermore, CADDAM Engineering aim to maximise the recovery of valuable products, including ethane and condensate. A design that is safe, technically, environmentally and economically feasible has been developed to successfully meet these processing objectives.
The design scope for this project can be divided into three main processing sections
1. Gas purification
2. Fractionation
3. Refrigeration
The feed gas from the Greater Sunrise field is processed in two parallel trains before recombining at the depropaniser in the fractionation section. Gas purification consists of a mercury removal unit, amine sweetening process and dehydration system. For improved safety, these processes are further separated into a hydrogen sulphide contaminated area and a hydrogen sulphide free area.
Non-regenerative mercury removal, using metal sulphide absorbent, was selected due to the ability of this technology to remove mercury in the presence of water. This allowed removal of mercury at the earliest stage of the plant, preventing contamination of processing equipment downstream as well as eliminating the presence of mercury in the carbon-dioxide and water waste streams, exiting the amine and dehydration units respectively.
Following mercury removal, the gas is sent to an amine sweetening unit where a mix of MDEA and piperazine are used to remove carbon-dioxide and hydrogen sulphide from the processing gas. A well established and reliable technology, this unit removes carbon dioxide to levels below 10 parts per million and hydrogen sulphide to below 4 parts per million. The 95%mol carbon-dioxide stream produced is currently incinerated. In the event of the implementation of a carbon tax in the future, this stream could be captured for sequestration making the design "carbon-capture ready".
Once hydrogen sulphide is no longer present, the gas enters the hydrogen sulphide free zone for the removal of water. The cryogenic nature of the downstream processes necessitates the use of molecular sieves to reduce water content to trace amounts for safe operation. Temperature swing adsorption was selected. The 3 columns contain 29% Sorbead and 71% 4A molecular sieve. The clean gas is then sent to the fractionation train for the separation of saleable products.
A direct approach based on heuristic guidelines was used for the sequencing of the fractionation train. Fractionation begins with the demethaniser for the production of sales gas and LNG. An Ortloff Recycle Split Vapour process is used to separate the ethane from the methane. This well established process incorporates mechanical and Joule-Thomson expansion, allowing for a high ethane recovery of 96% in the deethaniser. The ethane stream provides a feed for the adjacent ethylene plant.
At this point, the two trains recombine prior to introduction to the depropaniser. In this way, a single depropaniser and debutaniser service the entire processing plant. 91% propane recovery is achieved while the majority of butane leaves in the butane product stream. The condensate product contains the remaining hydrocarbons but does not meet the Reid vapour pressure specification due to high pentane concentrations. As such, it must be stored in a fixed roof tank with a vapour handling system.
The gas process plant is serviced by a multi-stage propane refrigeration system as this requires simpler design as compared to a cascade system. Also, propane is manufactured on-site and is therefore readily available for use. On-site gas turbines provide electricity and heating of circulated hot oil.
