Method for treating industrial water by physical separation, adsorption on resin and reverse osmosis, and corresponding plant

Abstract

The present invention relates to a method for treating industrial water containing organic matter, said method comprising: a step of physical separation producing wastes and an effluent; a step of adsorption of at least one part of said organic matter present in said effluent on at least one adsorbent resin chosen from the group comprising the non-ionic cross-linked resins and the microporous carbon resins; a step of reverse osmosis filtration downstream from said adsorption step.

Claims

1. A method of treating wastewater containing matter in suspension, insoluble hydrocarbons, organic matter including aromatic compounds and dissolved solids, the method comprising: removing the matter in suspension and the insoluble hydrocarbons from the wastewater by filtering the water with a microfiltration or ultrafiltration membrane module which produces a permeate and a concentrate containing the matter in suspension and the insoluble hydrocarbons, wherein the wastewater is produced water from petroleum or gas fields; heating the concentrate; after heating the concentrate, recovering the insoluble hydrocarbons in the concentrate by directing the concentrate to a centrifuge and centrifuging the concentrate; directing the permeate from the microfiltration or ultrafiltration membrane module through two separate columns disposed in series where one column contains a non-ionic cross-linked polymer resin and the other column contains microporous carbon resins; as the permeate flows through the two columns, removing the organic matter including the aromatic compounds by adsorbing the organic matter including the aromatic compounds onto the resins in the columns; and after the permeate has flowed through the two columns in series, removing the dissolved solids by directing the permeate from the microfiltration or ultrafiltration membrane module through a reverse osmosis filtration unit.

2. The method of claim 1 including regenerating the resins in the columns by directing a solvent into and through the columns resulting in a solvent charged with organic matter; regenerating the solvent charged with organic matter by directing the solvent charged with organic matter to an evaporation process and evaporating the solvent charged with organic matter to produce a condensed solvent that is recycled to the columns and an organic phase having adsorbed organic matter.

3. The method of claim 1 including regenerating the resins in the columns by directing steam into and through the columns; condensing the steam in the columns which results in the production of an aqueous phase constituted by water saturated with organic compounds.

4. The method of claim 1 wherein the water is not biologically treated, does not produce biological sludge and is not cooled.

5. A method of treating wastewater containing matter in suspension and organic matter including aromatic compounds and dissolved solids, the method comprising: removing the matter in suspension from the wastewater by filtering the water with a microfiltration or ultrafiltration membrane module which produces a permeate and a concentrate containing the matter in suspension, wherein the wastewater is produced water from petroleum or gas fields; directing the permeate from the microfiltration or ultrafiltration membrane module through two separate columns disposed in series where one column contains a non-ionic cross-linked polymer resin and the other column contains microporous carbon resins; as the permeate flows through the two columns, removing the organic matter including the aromatic compounds by adsorbing the organic matter including the aromatic compounds onto the resins in the columns; and after the permeate has flowed through the two columns in series, removing the dissolved solids by directing the permeate from the microfiltration or ultrafiltration membrane module through a reverse osmosis filtration unit.

6. The method of claim 5 including regenerating the resins in the columns by directing a solvent into and through the columns resulting in a solvent charged with organic matter; regenerating the solvent charged with organic matter by directing the solvent charged with organic matter to an evaporation process and evaporating the solvent charged with organic matter to produce a condensed solvent that is recycled to the columns and an organic phase having adsorbed organic matter.

7. The method of claim 5 including regenerating the resins in the columns by directing steam into and through the columns; condensing the steam in the columns which results in the production of an aqueous phase constituted by water saturated with organic compounds.

8. The method of claim 5 wherein the water is not biologically treated, does not produce biological sludge and is not cooled.

9. The method of claim 1 wherein the produced water contains benzene, toluene, ethylbenzene and xylene; and wherein the non-ionic crosslinked polymer resin reduces the concentration of benzene, toluene, ethylbenzene and xylene 99.5+/-0.5%.

10. The method of claim 5 wherein the produced water contains benzene, toluene, ethylbenzene and xylene; and wherein the non-ionic crosslinked polymer resin reduces the concentration of benzene, toluene, ethylbenzene and xylene 99.5+/-0.5%.

Description

5. LIST OF FIGURES

(1) Other features and advantages of the invention shall appear more clearly from the following description of particular embodiments, given by way of a simple, illustratory and non-exhaustive embodiment and from the appended drawings, of which:

(2) FIG. 1 illustrates a simplified diagram of an example of an installation according to the invention;

(3) FIG. 2 illustrates a detailed embodiment of a plant according to the invention.

6. DESCRIPTION OF A PARTICULAR EMBODIMENT

(4) The invention as well as its different advantages will be understood more clearly from the following description of an embodiment given by way of a non-exhaustive illustration.

6.1. Plant

6.1.1. General Architecture

(5) FIG. 1 illustrates the general architecture of a plant for treating water according to the invention.

(6) As shown in this FIG. 1, such a plant comprises water leading-in means, such as a pipe, for leading in polluted water to be treated towards a physical separation unit 2.

(7) This physical separation unit 2 can comprise one or more cascade-mounted microfiltration or ultrafiltration type membrane filtration modules. The membranes of these modules, which are commercially available, are of the immersed or pressurized type made of polytetrafluoroethylene (PTFE) or are tubular and made of polyvinylidene fluoride (PVDF).

(8) In variants, this physical separation unit could for example include tubes enclosing filtration membranes, and these tubes can be polymeric (vinyl polychloride), composite or metallic pumps for supplying and pumps for cleaning.

(9) This physical separation unit 2 leads to the implementation of a step of separation enabling the elimination of the matter in suspension and of the water-insoluble hydrocarbons, in practice free oils, contained in the effluents which are discharged by means of an outlet of wastes 21. These wastes are sent towards a zone 3 for treatment by heating and centrifugation in order to recover the insoluble hydrocarbons separated from water. These hydrocarbons are recovered with an efficiency of 95%, in a form that can be valorized, by the pipe 30.

(10) The plant also includes means for leading in 12 and means for discharge 13 of a solution of reactant for the in situ washing of the physical separation unit 2.

(11) The effluents coming from the physical separation unit 2 are directed towards at least one column 4 containing at least one adsorbent resin chosen from the group comprising non-ionic cross-linked resins and microporous carbon resins. The step of treatment by adsorption on resin enables the elimination of the soluble organic matter initially present in the water to be treated.

(12) After having travelled through the column 4, the water is conveyed to at least one reverse osmosis filtration unit 5.

(13) The plant comprises means for regenerating resins. These means of regeneration comprise means for injecting 41, such as a pipe or an injector for injecting steam and/or solvent into the column 4. Through such means, the matter adsorbed on the resins can be detached from the resins.

(14) When the regeneration step is performed by means of a solvent, the solvent charged with organic matter can, entirely or partly, be recovered at the outlet of the column 4 by the pipe 42 in order to undergo evaporation within an evaporator 6 leading to the obtaining of two phases: a condensed phase, constituted by recycled, regenerated solvent, discharged by a pipe 61, and an organic phase constituted by adsorbed organic matter discharged by a pipe 62.

(15) When the regeneration step is performed with steam, the steam can be discharged after condensation by the pipe 42, the condensation leading to the obtaining of two phases: an aqueous phase constituted by water saturated with organic compounds and an organic phase constituted by adsorbed organic matter. The aqueous phase can then be made to pass on the column of adsorbent resin so as to de-saturate it of organic compounds. This leads to water that can be re-utilized to make steam during a subsequent step of in situ regeneration of the resins.

(16) The reverse osmosis filtration unit 5 comprises membranes made of composite polyamide (of a spiral-wound type with low clogging that can take pressures of up to 41 bars). It has the advantage of having low clogging and the ability to withstand temperatures of up to 85 C. This unit could include several passes (filtration of the permeate coming from the reverse osmosis unit through the unit) or several stages (several cascade-mounted reverse osmosis units: the concentrate coming from one unit being filtered in the following unit). The treated water coming from the reverse osmosis filtration unit is collected by the pipe 51 while the wastes coming therefrom are discharged by the pipe 52. The reverse osmosis step reduces the alkalinity, the salinity, the hardness, the silica and the boron.

6.1.2. Example of One Embodiment

(17) The embodiment described with reference to FIG. 2 represents the schematic view of a pilot plant implementing a method according to the invention for the treatment of production water from petroleum fields.

(18) The pilot plant comprises means for leading in polluted water to be treated to a unit of physical separation by ultrafiltration herein implementing two cascade-mounted ultrafiltration membrane modules 2, 2. The membranes of these modules, which are commercially available, are made of polyvinylidene fluoride (PVDF). They are fixed to a coating made of polyester and the mean diameter of their pores is 30 nm. This filtration unit enables the elimination of the matter in suspension and the water-insoluble hydrocarbons, in practice free oils, contained in the effluents.

(19) The recovery of the insoluble hydrocarbons stopped by the membranes is achieved by separation of the matter that has collected on the interface of the membranes, corresponding to the concentrate, by heating and by centrifugation. The heating is done in a tank 31 and the centrifugation is done in a centrifuge 32. These hydrocarbons are recovered with an efficiency of 95%, in a form that can be valorized, by the pipe 30.

(20) The pilot plant furthermore includes means for conveying 12 and means for discharging 13 a solution of reactant for in situ washing of the ultrafiltration membranes.

(21) After having undergone this ultrafiltration step, the effluents are directed, in the example, towards an optional buffer tank 60 and then directed towards two series-mounted columns 4, 4 containing two specific resins.

(22) The first column 4 contains a commercially available non-ionic cross-linked polymer resin (resin 1) selected for its capacity to adsorb aromatic components such as BTEX (benzene, toluene, ethylbenzene, xylene) and the polycyclic compounds such as the PACs (e.g. naphthalene). The characteristics of this resin are given in the Table 1 here below:

(23) TABLE-US-00001 TABLE 1 Physical and chemical properties Ionic form neutral Functional groups none Matrix Cross-linked polystyrene Structure Porous beads Coefficient of uniformity 1.1 max Mean size of beads 0.44 to 0.54 mm Bulk density 600 g/l Water retention capacity 600 g/kg resin +/5% Specific surface area (BET method) About 800 m.sup.2/g approximately Volume of pores 1.2 cm.sup.3/g approximately Average diameter of pores 5 to 10 nm pH stability 0 to 14 Temperature stability 20 C. to 120 C.

(24) The second column 4 contains a microporous carbon resin (resin 2), also commercially available, selected for its ability to fix compounds in trace states more advantageously. The characteristics of this resin are given in the Table 2 here below:

(25) TABLE-US-00002 TABLE 2 Physical and chemical properties Ionic form neutral Functional group none Matrix carbon Grain size 0.4 to 0.8 mm (>90%) Bulk density 550 to 650 g/l +/5% Specific surface area (BET method) About 1200 m.sup.2/g Volume of pores About 0.15 cm.sup.3/g Average diameter of pores 8 nm Temperature stability 20 C. to 300 C.

(26) After having travelled successively in transit in the columns 4 and 4, the water is conveyed towards a reverse osmosis filtration unit 5.

(27) The pilot plant comprises means for regenerating resins, either by steam or by a solvent. These means for regeneration comprise pipes for leading in steam 41 and/or solvent 41 leading into the columns 4, 4. Through such means, the matter adsorbed on the resins can be detached from them.

(28) When the regeneration is done by means of a solvent, the solvent charged with organic matter can be entirely or partly recovered at the outlet from the columns by the pipe 42 in order to undergo an evaporation leading to the obtaining of two phases: a condensed phase, constituted by recycled, regenerated solvent and brought to the pipe 61 leading into the pipe 41, and an organic phase constituted by adsorbed organic matter, discharged by a pipe 62. When the regeneration is done with steam, this steam can be discharged after condensation by the pipe 17, the condensation leading to the obtaining of two phases: an aqueous phase constituted by water saturated in organic compounds and an organic phase constituted by adsorbed organic matter. The aqueous phase can then be passed over the first column of adsorbent resin so as to desaturate it of organic compounds. This gives water that can be re-utilized to make steam during a subsequent step of in situ regeneration of the resins.

(29) The characteristics of the production water from a petroleum field treated by means of the plant described here above are explained in the Table 3 here below.

(30) TABLE-US-00003 TABLE 3 Parameter Unit Range of values Temperature C. 20-70 pH upH 6.5-7.5 Chloride mg/L 2500-5000 Sulfate mg/L 500-2000 Alkalinity ppm CaCO.sub.3 500-2000 Sodium mg/L 1500-3500 Calcium mg/L 200-2000 Magnesium mg/L 50-300 Dissolved salts mg/L 5000-10000 Benzene mg/L 1-30 Toluene mg/L 1-30 Ethylbenzene mg/L 1-10 Xylene mg/L 1-5 Phenol mg/L 1-30 Naphtalene mg/L 0.5-5 Benzyl alcohol mg/L 5-30 2-methylphenol mg/L 1-5 3-methylphenol mg/L 1-5 4-methylphenol mg/L 1-5 TOC mg/L 20-150

(31) In terms of performance of treatment, ultrafiltration reduced the concentration of oils and matter in suspension to levels according to the Table 4 here below,

(32) TABLE-US-00004 TABLE 4 Concentration in treated Reduction rate Compound effluent (in mg/l) (in %) Insoluble hydrocarbons 0.2 0.5 99 to 99.96 Matter in suspension 0.1 0.5 99 to 99.9 Polyaromatic 20 50 80 to 90 hydrocarbons

(33) The resins for their part were used to obtain the reduction levels collated in the table 5 here below:

(34) TABLE-US-00005 TABLE 5 Resin 1 (%) Resin 2 (%) Benzene 99.5 0.5 99.9 0.1 Toluene 99.5 0.5 99.9 0.1 Ethylbenzene 99.5 0.5 99.8 0.1 Xylene 99.5 0.5 99.8 0.1 Phenol 96.5 0.5 99.9 0.1 Naphtalene 99.7 0.3 99.9 0.1 Benzyl alcohol 84.0 1.0 99.5 0.5 2-methylphenol 99.5 0.5 99.9 0.1 3-methylphenol 99.5 0.5 99.9 0.1 4-methylphenol 99.5 0.5 99.9 0.1 TOC 50.0 5.0 85.0 5.0

(35) In terms of regeneration capacity, the resins were regenerated by steam. This regeneration enables the absorption capacities of the resins to be recovered by up to 80%. In addition, the condensation of the steam made it possible to separate the organic matter adsorbed on the first resin. The conditions and the results of this regeneration are indicated in the table 6.

(36) TABLE-US-00006 TABLE 6 Duration of cycle 7 days Characteristics of steam Resin 1: 125 C. at 2.4 bar Resin 2: 150 C. at 5.0 bar % of valorized matter 99% 1

(37) Regeneration with ethanol gave the same performance as that of steam, in terms of recovery of adsorption capacities and organic matter content capable of being valorized after evaporation and recovery of ethanol.

(38) The mode of regeneration that combines steam as a regeneration medium with ethanol, one in every ten regeneration cycles, showed better performance in terms of rate of recovery of capacity of adsorption of resins. This capacity is increased and reaches 95%.

(39) The reverse osmosis filtration unit 5 comprises membranes made of composite polyamide. They have the advantage of having low clogging and an ability to withstand temperatures of up to 85 C. This unit herein comprises two cascade-mounted stages. It could include a single dual-pass stage. The number of stages or passes could be greater. The treated water coming from the reverse osmosis filtration unit is collected by the pipe 51 for example for re-utilization as industrial water, for example to produce steam. The wastes coming therefrom are discharged by the pipe 52. The reverse osmosis reduces alkalinity, salinity, hardness silica and boron.

(40) The behavior of the reverse osmosis in terms of cleaning frequency is similar to the classic cases of desalination by reverse osmosis at ambient temperature.

(41) The conversion rate (flow rate of the permeate/flow rate of supply) of the reverse osmosis unit in using a dual-stage configuration reaches 83%.

(42) The pressure needed, with a salinity of 20000 mg/L, for a conversion rate of 83% in a dual-stage configuration at 60 C. is 25 bars instead of 46 to 50 bars for 25 C.

(43) The quality of the water obtained in a single-pass configuration of reverse osmosis is collated in the following table 7:

(44) TABLE-US-00007 TABLE 7 Parameters mg/L Salinity 70-450 Alcalinity 10-40 mg/L CaCO.sub.3 Hardness 3-30 mg/L CaCO.sub.3 Silica 0.8-6.5

(45) The quality of water obtained in a dual-pass configuration of reverse osmosis is collated in the following table 8:

(46) TABLE-US-00008 TABLE 8 Parameters mg/L Salinity 10-12 Alcalinity 0.3-1 mg/L CaCO.sub.3 Hardness 0.1-0.15 mg/L CaCO.sub.3 Silica 0.02-0.15