Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/34—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances
  • B01D3/38—Steam distillation

Definitions

• the invention relates to a process and a device for removing the hydrocarbons contained, in the dissolved state and / or in the state of suspension of the emulsion type or not, in waters and in particular in waste waters such as production water from hydrocarbon fields, by steam stripping.
• Rejection of such waste water can be done after treatment of these waste waters in ⁇ installations allowing the delivery of purified waste water in accordance with the regulations on discharges.
• waste water polluted by hydrocarbons which is encountered in oil or gas production, the hydrocarbons can be present in suspension in the free state or weakly emulsified, in the case of rainwater, or in the state of emulsions, production or process water, or / and be in the dissolved state.
• the emulsification of hydrocarbons in wastewater can have a mechanical origin, linked to accidents in pipes, pipes, pumps which create more or less fine emulsions depending on the characteristics of the hydrocarbons and the energy transferred to fluids, or an origin chemical linked to the presence of surfactants, for example corrosion inhibitors, bactericides, demulsifiers or others, which create finer and more stable emulsions by polarization of the interfaces between the drop of hydrocarbon and the aqueous medium.
• surfactants for example corrosion inhibitors, bactericides, demulsifiers or others, which create finer and more stable emulsions by polarization of the interfaces between the drop of hydrocarbon and the aqueous medium.
• hydrocarbons present in the dissolved state their solubility is a function of the nature of the hydrocarbons, the temperature and the pressure of the medium.
• the techniques for removing hydrocarbons suspended in water, or de-oiling techniques are generally based on the principles of gravity separation and in particular on increasing the decantation speed of the hydrocarbon drops so that they be eliminated as quickly as possible.
• centrifugation technique and cycloning technique which are separations by centrifugal forces having a dynamic character for centrifugation and a static character for cycloning (hydrocyclone);
• Flotation technique which consists in dispersing microbubbles of air or other gas in the liquid medium so as to generate turbulences which cause the hydrocarbon particles to meet together, these effects being increased by the use of additives. flotation, which are necessary to destabilize chemical emulsions;
• coagulation / flocculation technique which consists in bringing together the particles in suspension, in order to settle them, by means of heavy solid, mineral additives of the hydroxide or lime type;
• coalescence technique which consists of fusing small diameter drops to generate larger ones often through a fibrous or granular material.
• the invention provides a process for stripping hydrocarbons with water vapor, which makes it possible, in a single operation, to remove both the suspended hydrocarbons, emulsified or not, and the hydrocarbons physically dissolved in waste water of various origins with recovery of said hydrocarbons and production of purified water meeting the standards of discharge regulations, said process being particularly suitable for the treatment of production water from hydrocarbon fields.
• the subject of the invention is therefore a process for removing the hydrocarbons contained, in the dissolved state or / and in the suspension state of the elution type or not, in water by stripping with steam, said process characterized in that a stream of the water to be treated is introduced into the upper part of a stripping column, which comprises an upper part and a lower part communicating through an intermediate part containing 2 to 20 and preferably 5 to 15 theoretical stages of gas / liquid contact, said stream of water flowing towards the lower part of the column passing through the intermediate part of the latter, the liquid contained in the lower part of the stripping column is supplied sufficient heat energy to generate a quantity of water vapor circulating against the current of the water stream to be treated and thus stripping the hydrocarbons it contains, a pressure of between 1 and 3 bars absolute, we evacuate in.
• a gaseous phase formed by water vapor and hydrocarbons stripped by water vapor and said gaseous phase is cooled to transform it into a condensed liquid phase having a temperature equal to or less than 30 ° C. and preferably equal to or less than 20 "C, said liquid condensed phase is separated by gravity into an upper hydrocarbon phase and an aqueous lower phase and said hydrocarbon and aqueous phases are removed separately and a stream of water is drawn off at the bottom of the stripping column purified water, by carrying out this drawing off with a molar flow rate substantially equal to the difference between the molar flow rate of water in the stream of water to be treated and the molar flow rate of said aqueous phase.
• the aqueous phase, separated from the hydrocarbon phase is recycled in the stream of water to be treated, before the introduction of the latter into the stripping column, by carrying out this recycling with a molar flow rate of aqueous phase substantially equal to the molar flow rate of water vapor in the gas phase discharged at the head of the stripping column and the purified water stream is drawn off with a molar flow rate substantially equal to the molar flow rate water from the water stream to be treated before recycling the aqueous phase in this stream.
• the stream of water to be treated is preheated, before its introduction into the stripping column, by indirect heat exchange with the stream of purified water withdrawn from the bottom of said column.
• the recycling of the aqueous phase, resulting from the liquid condensed phase, in the stream of water to be treated is preferably carried out before the preheating of the stream of water to be treated.
• said part intermediate is generally fitted with gas / liquid contact plates or an equivalent height with suitable packing. All of said plates, respectively the equivalent lining height, correspond to a certain number of theoretical stages of gas / liquid contact, respectively to a certain equivalent theoretical lining height.
• theoretical stage of gas / liquid contact is meant an ideal gas / liquid contact zone for which the gas and / or liquid phases which exit therefrom are in thermodynamic equilibrium.
• the contribution of heat energy to the fluid contained in the lower part of the stripping column, to generate water vapor serving as stripping agent for hydrocarbons, can be carried out using any known technique and advantageously using the reboiling technique.
• the method according to the invention can be used to treat water from various sources polluted by hydrocarbons in the dissolved state and / or in suspension of the emulsion type or not, said hydrocarbons possibly being aromatic hydrocarbons, for example such as benzene, toluene , ethylbenzene, xylenes, paraffinic hydrocarbons, cycloaliphatic hydrocarbons, naphthenic hydrocarbons, mixtures of such hydrocarbons or the like.
• aromatic hydrocarbons for example such as benzene, toluene , ethylbenzene, xylenes, paraffinic hydrocarbons, cycloaliphatic hydrocarbons, naphthenic hydrocarbons, mixtures of such hydrocarbons or the like.
• Said method is particularly effective in eliminating the hydrocarbons contained in the waste water generated in oil and gas production, which, in addition to physically dissolved or / and suspended hydrocarbons of the emulsion type or not, may also contain various additives such as bactericides, anti- corrosion, hydrate inhibitor agents * .
• the method according to the invention makes it possible, very particularly, to treat water polluted by hydrocarbons in the physically dissolved or / and emulsified state and in particular water produced from hydrocarbon fields, the hydrocarbon content of which can range up to at 1% by weight or more, obtaining purified water whose hydrocarbon content is below the threshold, currently 40 ppm, set by the regulations on discharge.
• the invention also relates to a device for the elimination of the hydrocarbons contained, in the dissolved state and / or in the state of suspension of the emulsion type or not, in water by stripping with steam, said device being characterized in that it comprises a stripping column comprising an upper part and a lower part communicating by an intermediate part containing 2 to 20 and preferably 5 to 15 theoretical stages of gas / liquid contact, said column being provided, at the head, a vapor evacuation pipe and, at the bottom, a purified water withdrawal pipe and being equipped with a supply pipe for the water to be treated, opening into its upper part and, in its part bottom, of a heating system, a condenser having an inlet, connected to the vapor discharge duct of the stripping column, and an outlet, said condenser being arranged to produce a condensed liquid phase having a temperature ature equal to or less than 30 ⁇ C and preferably equal to or less than 20 ° C, a separator operating by gravity and having an inlet connected by a conduit to the
• the outlet for the aqueous phase which is provided with the separator, is connected by a conduit, provided with recycling means, to the conduit for supplying the water to be treated to the stripping column.
• the device according to the invention also comprises an indirect heat exchanger, the cold circuit of which is mounted in series on the pipe bringing the water to be treated to the stripping column and the hot circuit is placed in series on the pipe.
• liquid withdrawal unit mounted at the bottom of the stripping column.
• the connection between the conduit, provided with recycling means, which is mounted at the outlet for the aqueous phase at the bottom of the separator, and the conduit for supplying the water to be treated to the stripping column is preferably made upstream of the indirect heat exchanger.
• the device according to the invention comprises a stripping column 1 comprising an upper part 2 and a lower part 3 communicating through an intermediate part containing a number of gas / liquid contact plates corresponding to a number of Theoretical gas / liquid contact stages ranging from 2 to 20 and preferably from 5 to 15.
• Column 1 is provided, at the top, with a pipe 5 for discharging vapors and, at the bottom, with a pipe 6 for withdrawal of liquid and, in addition, it is equipped with a pipe 7 for supplying the water to be treated, said pipe opening at 8 in the upper part of the column 1.
• the column 1 In its lower part 3, the column 1 is associated, by tubing inlet 9 and outlet 10, to a reboiler 11 heated by indirect exchange of heat energy with a heat transfer fluid at an appropriate temperature circulating in a pipe 12.
• a reboiler 11 heated by indirect exchange of heat energy with a heat transfer fluid at an appropriate temperature circulating in a pipe 12.
• a heat transfer fluid at an appropriate temperature circulating in a pipe 12.
• an electric or boiler heating of the reboiler 11 On the duct 7, which brings the water to be treated to the column 1, is mounted in series the cold circuit of an indirect heat exchanger 13, the hot circuit of which is placed in series on the duct 6 for drawing off the current. purified water, which is fitted to the bottom of the column 1.
• a condenser 14 which has an inlet 15 and an outlet 16 and which is cooled by a refrigerant circuit, for example air cooler or cold fluid circuit, to produce a phase liquid condensate having a temperature equal to or less than 30 ° C and preferably equal to or less than 20 ⁇ C, at its inlet 15 connected to the duct 5 for evacuating vapors from the stripping column 1 e t its output 16 connected, by a conduit 17, to the input 18 of a separator 19 of the gravity separator type.
• a refrigerant circuit for example air cooler or cold fluid circuit
• Said separator has, in its middle part, an outlet 20 for hydrocarbons, which is extended by a discharge duct 21, and, in its lower part, an outlet 22 for an aqueous phase, which outlet 22 is connected, by a conduit 23 provided with recycling means 24 consisting, for example, of a pump, in the conduit 7 for supplying the water to be treated to the stripping column, said connection being made upstream of the indirect heat exchanger 13 mounted in series on the duct 7.
• a pressure regulating valve is mounted on the duct 5 or on the duct 17 to control the pressure at the head of the stripping column 1.
• the operation of this device can be diagrammed as follows:
• the stream of water to be treated which contains hydrocarbons in the dissolved state or / t in the suspension state of the emulsion type or not, arrives via the conduit 7 and passes in 1 * indirect heat exchanger 13, where it is preheated by indirect exchange of calories with the water freed from the hydrocarbons drawn off at the bottom of the stripping column 1 by the conduit 6.
• the preheated stream of water to be treated is then introduced, via inlet 8, in the upper part 2 of the stripping column.
• the water stream to be treated flows by gravity to the lower part 3 of the column, passing through the intermediate part 4 provided with gas / liquid contact stages.
• the liquid arriving in the lower part 3 of the column 1 is subjected to a reboiling by passage, through the tubing 9, in the reboiler 11 and return, by the tubing 10, in the lower part 3 of the column 1, so to generate an appropriate amount of water vapor for. stripping of hydrocarbons.
• the pressure at the top of said column 1 is maintained between 1 and 3 bar absolute by means of the pressure regulating valve, not shown, mounted on line 5 or on line 17.
• the heat energy for reboiling is supplied by indirect heat exchange with a heat transfer fluid at an appropriate temperature circulating in the tube 12.
• the water vapor generated by the reboiling circulates in the column 1, from the lower part 3 to the upper part 2 passing through the intermediate part 4 , that is to say against the current of the water stream to be treated, and carries out the stripping of the hydrocarbons contained in said water stream.
• a gas phase is evacuated consisting of a mixture of water vapor and hydrocarbons stripped from the water stream to be treated by the water vapor generated by reboiling, said gas phase being cooled in the condenser 14, by indirect heat exchange with a suitable coolant, to form a condensed liquid phase having a temperature equal to or less than 30 ° C and preferably equal to or less than 20 ° C.
• This liquid condensed phase is brought to the separator 19, in which it separates into an upper hydrocarbon phase, which is discharged through line 21, and into an aqueous phase, which is evacuated through line 23 and which is recycled in the stream of water passing through line 7, by carrying out this recycling upstream of the heat exchanger 13 and with a molar flow rate substantially equal to the molar flow rate water vapor from the gas phase discharged from column 1 through line 5 at the head of this column.
• a stream of purified water is drawn off, via line 6, by carrying out this drawing off with a molar flow rate substantially equal to the molar flow rate of water in the water stream to be treated before recycling of the aqueous phase. in this stream, which stream of purified water, after passing through the heat exchanger 13 to preheat the stream of water to be treated, is directed to the place of discharge.
• the water stream to be treated arrived via line 7 with a flow rate, measured before recycling of the aqueous phase through line 23, equal to 4.6 m 3 / hour and, after preheating in the heat exchanger 13, 1 'water introduced into the stripping column 1, via inlet 8, had a temperature equal to 100 ° C.
• a pressure was maintained at the head of column 1 equal to 1.4 bar absolute, which corresponds to a temperature at the bottom of said column equal to 112 ° C and the reboiler 11 was supplied with a calorific power equal to 220 kW.
• EXAMPLE 2 By operating under conditions analogous to those described in Example 1, however using a calorific power equal to 320 kW for reboiling, 4.6 m 3 / hour of a stream of water were treated. for producing a gas field containing 1500 mg / 1 of a mixture of hydrocarbons having the composition given in the example
• the pressure at the top of the stripping column was equal to 1.4 bar absolute and the temperature at the bottom of said column had a value of 112 ⁇ C.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Physical Water Treatments (AREA)
• Degasification And Air Bubble Elimination (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

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Family Applications (1)

Country Status (5)

Cited By (3)

Citations (4)

• 1992
  • 1992-02-27 FR FR9202297A patent/FR2687928A1/fr active Granted
• 1993
  • 1993-02-26 WO PCT/FR1993/000193 patent/WO1993016779A1/fr unknown
  • 1993-02-26 NL NL9320001A patent/NL195054C/nl not_active IP Right Cessation
  • 1993-02-26 GB GB9321966A patent/GB2273667B/en not_active Expired - Fee Related
  • 1993-10-26 NO NO933852A patent/NO300003B1/no not_active IP Right Cessation

Patent Citations (4)

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