Gas separation: processes – Liquid contacting – And degasification of a liquid
Patent
1998-04-13
2000-01-18
Smith, Duane S.
Gas separation: processes
Liquid contacting
And degasification of a liquid
95193, 95194, 95229, 95237, 96234, 96242, 96266, B01D 5314
Patent
active
060154519
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to vapour recovery systems suitable for recovery of entrained volatile organic compounds (VOC). It finds particular application in the recovery of vaporised VOC expelled from the holds of crude oil tanker ships during loading with crude oil. It also finds application in other situations where an intermittent supply of vaporised hydrocarbons is to be recovered.
The empty holds of crude oil tanker ships are held under inert gas; however, the empty holds inevitably contain some vaporised VOC and residual oil from the previous crude oil cargo. During loading of the holds with crude oil, these VOC, with the inert gas, are expelled from the holds, and further VOC are generated from the crude oil as it is loaded by vaporization from the surface.
Apart from at the start and end of loading operations, the flow of crude oil into the tanker hold is generally kept constant. Because of vaporization of VOC in the hold, the volumetric flow rate of vapour entering the apparatus substantially exceeds the flow of crude oil into the tanker hold. Towards the end of loading, the vapour can constitute up to 50% by volume of mixture entering the apparatus. Throughout the loading procedure, therefore, considerable amounts of VOC are expelled from the holds, entrains in inert gas.
The expelled VOC/inert gas mixture is commonly vented to atmosphere; however, it would be preferred to recover the VOC for use. A proposal for a system for achieving this has been made in WO-A-93/15166, which discloses a vapour recovery system in which a mixture of air and crude oil VOC is compressed and introduced into a washing column where it is washed with crude oil under pressure. The washed gases are then passed to an absorption column where they are contacted with petroleum at -25.degree. C., which absorbs the VOC. The VOC-rich petroleum is passed via a small buffer tank to a distillation (stripper) column operating at around atmospheric pressure. The recovered VOC-lean petroleum is cooled and recycled to the absorption column, while the recovered VOC vapour is conveyed from the top of the distillation column to the inlet of the system, where it is mixed with the incoming air and crude oil VOC prior to compression.
The plant of this document recovers the crude oil VOC as vapour; if it is not desired to mix it with incoming air and crude oil vapour, it must be dispersed or liquefied. Further, the plant only operates intermittently, when there is incoming air and crude oil VOC. Thus, the plant must be idle when no tanker ship is being loaded; the requirement for frequent shut down and start up of the column means that it is practical only to use a column operating at or near atmospheric pressure.
The system described above is adapted from that disclosed in WO-A-82/04260. WO-A-82/04260 discloses a petrol vapour recovery system, in which air and petrol vapour pass to an absorption column, where the petrol vapour is entrained in cold petroleum distillate. The petrol-rich petroleum distillate passes to a buffer tank so that variations in the concentration of petrol in the petroleum distillate are largely evened out. The absorption column is run so that the concentration of petrol in the petrol-rich petroleum distillate is substantially constant, so that the buffer tank can be quite small. The petrol-rich petroleum distillate passes from the buffer tank to a distillation (stripper) column, where the petrol vapour is separated from the petroleum distillate. The petroleum distillate is held in a cooled storage tank from where it passes into the absorption column. The petrol vapour is entrained in liquid petrol in a second absorption column.
The distillation column of this system operates at about atmospheric pressure, and the system operates intermittently, when loading is taking place. The absorption of the separated petrol vapour in liquid petrol is economically feasible at the relatively small scale on which petrol vapour recovery systems operate; such a plant for recovery of crude oil VOC would be exp
REFERENCES:
patent: 2423156 (1947-07-01), Reid
patent: 3830040 (1974-08-01), Hendrix
patent: 3855337 (1974-12-01), Foral, Jr. et al.
patent: 3861890 (1975-01-01), Doncer et al.
patent: 3947258 (1976-03-01), Decker
patent: 4263019 (1981-04-01), Minkkinen
patent: 4475928 (1984-10-01), Jacobsen
patent: 5476986 (1995-12-01), Jacobsen
Anderson Thomas B.
Drucker Elliott
Robinson John Dennis
Fluor Corporation
Smith Duane S.
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