Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1995-08-07
1998-10-06
Burn, Brian M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568680, 568868, B01D 1500
Patent
active
058178899
DESCRIPTION:
BRIEF SUMMARY
This is the U.S. National Stage Application of PCT/FR94/01249 filed Oct. 27, 1994, now WO95/11876 published May 4, 1995.
The invention relates to a process for the purification of a glycol solution based on one or more glycols and additionally containing water and, as impurities, dissolved salts and hydrocarbons in the dissolved and/or emulsified state. The invention relates, in particular, to the regeneration of glycol solutions of the abovementioned type, which are formed during various treatments of effluents of gas or petroleum production by glycols, especially dehydration treatment of natural gases or alternatively, treatment for prevention of the formation of gas hydrates, particularly, hydrates of natural gases or of petroleum gas, in the discharge pipes of the multiphase effluents from petroleum or gas production.
The glycols used for the treatment of the effluents of petroleum or gas production are diols, in which the OH groups are located at the end of the molecular chain and which are included in the general formula HO--(C.sub.n H.sub.2n O).sub.p --C.sub.n H.sub.2n OH, in which n is an integer ranging from 2 to 4, preferably equal to 2 or 3, and p represents 0 or an integer ranging from 1 to 4, preferably 0 or an integer equal to 1 or 2.
Three glycols corresponding to the abovementioned formula are widely used in the petroleum and gas industry and in particular in the field of the production of natural gas. These are monoethylene glycol (MEG) of formula HOCH.sub.2 CH.sub.2 OH (n=2 and p=0 in the general formula), diethylene glycol (DEG) of formula HOCH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 OH (n=2 and p=1 in the general formula) and triethylene glycol (TEG) of formula HOCH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 OH (n=2 and p=2 in the general formula).
Glycols such as MEG, DEG and TEG are used to prevent the formation of gas hydrates in pipes serving to discharge the multiphase effluents arising from sites for petroleum or gas production. The hydrates are solid products, which are formed by association of molecules of water and gas, especially natural gas or petroleum gas, under certain temperature and pressure conditions. These solid products may damage the pipes in which the petroleum or gas effluents circulate or may prevent the discharge of the said effluents by plugging the pipes. Injection of MEG, DEG or TEG into the said pipes has the effect of displacing the pressure and temperature conditions for formation of the hydrates to values which are sufficiently different from the pressure and temperature conditions prevailing in the pipes, in order to allow the petroleum or gas effluents in these pipes to flow without incident. These glycols are separated from the petroleum or gas effluents containing them and are regenerated in plants located at the terminal for reception of the said effluents. Regeneration is carried out by a well known stripping technique using steam and optionally an extra gas, this stripping generally being carried out in a regeneration column equipped with a boiler including a system of indirect heat exchange containing tubes or plates through which a heat exchange fluid circulates.
The implementation of regeneration of the glycol which is recovered, in the form of a mixture with water, at the terminal for reception of the petroleum or gas effluents comes up against difficulties of two types.
Firstly, it often arises that deposit water plugs containing high levels of salts, for example alkali metal or alkaline-earth metal chlorides and sulphates such as NaCl, KCl, Na.sub.2 SO.sub.4, CaCl.sub.2, MgCl.sub.2, BaCl.sub.2 and SrCl.sub.2, are extracted from the deposit with the gas and the liquid hydrocarbons produced by the deposit. The water contained in the petroleum or gas effluent, which forms by condensation of steam in the discharge pipe, mixes with this deposit water to such an extent that it is necessary, at the terminal, to regenerate a mixture of glycol and salt water. If the salt content exceeds a certain threshold, the salts are deposited in the hottest p
REFERENCES:
patent: 4518396 (1985-05-01), Rawson
Blanc Claude
Morin Daniel
Pondebat Chantal
Burn Brian M.
Elf Aquitaine Production
Padmanabhan S.
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