US 4,784,753 AGranted

Deasphalting process comprising power recovery from the stage of separating deasphalted oil from the deasphalting solvent

AssigneeInstitut Francais du Petrole

InventorsGerard Hotier, Pierre Renard

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Abstract

In a deasphalting process wherein the deasphalted oil is separated from the deasphalting solvent, the invention consists of performing said separation in at least two separate steps, differing by their temperatures, and of recovering heat from the deasphalted oil. The oil to be deasphalted (26) passes through an extractor (1), then through heat recuperators (3) and (4). The oil-solvent separation is achieved in two steps (5) and (11), under supercritical conditions, at different temperatures. The process has the particular advantage of saving power since external heat is provided (10) to only part of the charge.

Claims9

Dependent claims

In a deasphalting process, wherein an asphalt-containing oil is subjected to extraction by means of a solvent selected from hydrocarbons having 3 to 6 carbon atoms and mixtures thereof, an oil phase of raw extract and an asphalt phase of raw raffinate are separately recovered and solvent is separated from each of said phases, the improvement in the solvent separation comprising:

(a) in a first step, heating said oily phase of raw extract to a temperature T.sub.1 at a pressure P.sub.1 which together are supercritical with respect to the solvent, so as to settle said oily phase into two phases, respectively a first phase of recovered solvent and a first extract phase of increased oil content and decreased solvent content, and separating said settled two phases from each other, and
(b) in a second step, heating said first extract phase of increased oil content and decreased solvent content separated in the first step to a temperature T.sub.2 at a pressure P.sub.2 which together are supercritical with respect to the solvent, so as to settle said first extract phase into two phases, respectively a second phase of recovered solvent and a second extract phase of increased oil content, and separating said settled two phases from each other, and recycling said first phase and said second phase of recovered solvent to said extraction, wherein at least a portion of the heat supplied to said first extract phase in the second step is heat of external origin, and at least a portion of the heat supplied to said oily phase of raw extract in the first step is supplied by a heat exchange with said first phase of recovered solvent before recycle thereof to said extraction and a heat exchange with said second extract phase of increased oil content, T.sub.1, T.sub.2, P.sub.1 and P.sub.2 being defined as follows:
Tc+1.5 x.sub.2 -2x<T.sub.1 <Tc+1.5 x.sup.2 -2x+45
T.sub.1 +2-<T.sub.2 <T.sub.1 +80
Pc+5<P.sub.1 <Pc+30
Pc<P.sub.2 <P.sub.1 +20
wherein Tc and Pc are respectively the critical temperatures and the critical pressure of the solvent, the temperatures being expressed in celsius degrees and the pressures in bars, and x is the average number of carbon atoms of the solvent molecule, the second extract phase of increased oil content forming the desired deasphalted oil wherefrom residual solvent, when present, can be separated.

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Dependencies are inferred from the claim text.

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Abstract

(a) in a first step, heating said oily phase of raw extract to a temperature T.sub.1 at a pressure P.sub.1 which together are supercritical with respect to the solvent, so as to settle said oily phase into two phases, respectively a first phase of recovered solvent and a first extract phase of increased oil content and decreased solvent content, and separating said settled two phases from each other, and
(b) in a second step, heating said first extract phase of increased oil content and decreased solvent content separated in the first step to a temperature T.sub.2 at a pressure P.sub.2 which together are supercritical with respect to the solvent, so as to settle said first extract phase into two phases, respectively a second phase of recovered solvent and a second extract phase of increased oil content, and separating said settled two phases from each other, and recycling said first phase and said second phase of recovered solvent to said extraction, wherein at least a portion of the heat supplied to said first extract phase in the second step is heat of external origin, and at least a portion of the heat supplied to said oily phase of raw extract in the first step is supplied by a heat exchange with said first phase of recovered solvent before recycle thereof to said extraction and a heat exchange with said second extract phase of increased oil content, T.sub.1, T.sub.2, P.sub.1 and P.sub.2 being defined as follows:
Tc+1.5 x.sub.2 -2x<T.sub.1 <Tc+1.5 x.sup.2 -2x+45
T.sub.1 +2-<T.sub.2 <T.sub.1 +80
Pc+5<P.sub.1 <Pc+30
Pc<P.sub.2 <P.sub.1 +20
wherein Tc and Pc are respectively the critical temperatures and the critical pressure of the solvent, the temperatures being expressed in celsius degrees and the pressures in bars, and x is the average number of carbon atoms of the solvent molecule, the second extract phase of increased oil content forming the desired deasphalted oil wherefrom residual solvent, when present, can be separated.

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