FR3004443A1 - PROCESS AND INSTALLATION FOR TREATING HOT INDUSTRIAL WATER. - Google Patents

Abstract

A process for the treatment of industrial waters having a temperature above 70 ° C and containing insoluble pollutants, suspended solids, and soluble organic material, said process comprising a step of micro-filtration or ultrafiltration on membranes leading to a filtrate and a concentrate, characterized in that said membranes are selected from the group consisting of polytetrafluoroethylene (PTFE) submerged membranes and polyvinylidene polyfluoride (PVDF) tubular membranes, and in that it comprises a step of adsorption of the suspended material contained in said filtrate, said adsorption step being carried out on at least one adsorbent resin selected from the group consisting of nonionized crosslinked polymeric resins and microporous charcoal resins. Corresponding installation.

Description

Process and installation for treating hot industrial water. Field of the invention The invention relates to the field of the treatment of industrial aqueous effluents having a high temperature. More specifically, the invention relates to the treatment of such hot waste water from the gas and oil or petrochemical industries, such as production facilities for oil and / or gas fields or refineries.

PRIOR ART The production waters of oil and gas fields are characterized by a temperature which may be high, in practice may be greater than about 55 ° C. and may in some cases rise up to 98 ° C., by pollution of hydrocarbons that are insoluble in water. water, and by the presence of suspended solids and organic matter soluble in water. The processes currently used for the treatment of such hot oil and gas field production water use techniques of microfiltration or ultrafiltration of effluents on ceramic membranes upstream of biological treatment techniques previously filtered effluents.

The first step of filtration on ceramic membranes allows the reduction of insoluble hydrocarbons and suspended solids while the second stage of biological treatment allows the reduction of soluble organic matter. In order for the biomass involved in the biological treatment stage to develop and function properly, it is imperative that the effluent be cooled to a temperature compatible therewith before undergoing the second stage. As the integrity of the organic membranes is liable to be altered by high temperatures, such membranes can not therefore be used in the context of these processes, for which reason they use ceramic membranes.

These methods have limitations in terms of operating costs, performance and operability. First, ceramic membranes are expensive to buy and maintain. When the flow rate of effluent to be treated is high, the number of membrane filtration units used must be too, which increases the investment and operating costs. In addition, the ceramic coatings (Ti02, CSi) of these membranes can catalyze certain reactions of oxidation of the organic matter, or of the combination of certain organic compounds, with metals available in these waters giving rise to the formation of organic compounds. -métalliques. These compounds are sources of clogging ceramic membranes and lead, in practice, to an increase in their cleaning frequency. Moreover, such waters can have a high hardness resulting in particular from high levels of alkaline earth elements, mainly calcium and / or magnesium. This high hardness, combined with the high interfacial flow rates, in practice generally between 1.5 and 5 m / s, necessary for the operation of these membranes, can cause premature erosion of these membranes and, consequently, the need for anticipate their replacement. Moreover, as indicated above, the implementation of a biological treatment for the removal of the soluble organic matter requires a prior cooling of the water to make them compatible with this type of treatment. However, cooling equipment increases in a global manner the size of facilities and, as a result, investments. In addition, such cooling can lead to a negative energy balance of the treatment. This is all the more true that there is an interest in reusing the treated water in the context of the processes from which it is derived, in particular to produce extraction steam. Indeed, these sites are often in places where water is scarce and therefore expensive. Cooling water intended, after treatment, to be reheated in order to be reused in the form of, for example, steam, therefore has a negative impact on the energy balance. It will also be noted that the biological treatment generates sludge whose quantity is proportional to the effluent flow rate treated and to the concentration of organic matter contained therein. This sludge is a waste whose treatment involves an economic and technical problem. In summary, these treatment techniques on ceramic membranes and biological treatment are of limited interest in the treatment of industrial hot water, including production water from oil and gas fields. OBJECTIVES OF THE INVENTION An object of the present invention is to provide an improved process for treating aqueous industrial effluents that may have a high temperature. In particular, it is an object of the present invention to describe such a method which, in at least some embodiments, makes it possible to reduce the costs of existing processes using filtration on ceramic membranes, while at the same time performing at least similar performances. them.

Yet another object of the present invention is to describe such a method which, in at least some embodiments, makes it possible to reduce the washing frequency of the membranes used, thereby leading to savings in washing reagents and reducing dirty water treatment costs. Yet another object of the present invention is to propose such a method which, in at least some embodiments, makes it possible to recover the pollutants contained in the waters, thus making it possible to reuse these in the form of products. Another object of the present invention is to disclose an installation for carrying out such a method. DESCRIPTION OF THE INVENTION These various objectives, or at least some of them, are attained thanks to the present invention which concerns a process for the treatment of industrial waters having a temperature of between 55 ° C. and 98 ° C., preferably between 65 ° C. and 98 ° C. ° C and 85 ° C, and containing water-insoluble pollutants, suspended solids, and water-soluble organic matter, said process comprising a micro-filtration or ultrafiltration membrane step leading to a filtrate and a concentrate. The process according to the invention characterized in that said membranes are chosen from the group consisting of immersed membranes made of polytetrafluoroethylene (PTFE) and polyvinylidene polyfluoride (PVDF) tubular membranes, and that it comprises a step of adsorption of the suspended material contained in said filtrate, said adsorption step being carried out on at least one adsorbent resin selected from the group consisting of nonionized crosslinked polymeric resins and microporous charcoal resins, also by nature non-ionized.

Thus, the invention proposes a treatment method which does not implement a biological treatment step, and therefore without sludge resulting from such treatment, and which, thanks in addition to the use of suitable membranes, can be used. implemented without any cooling step of the hot effluents. In fact, both the membranes and the adsorbent resins selected in the context of the process according to the invention do not see their degraded performance due to the high temperature of the treated water. The present invention therefore consists in the combined use of specific membranes and non-ionized adsorbent resins (which excludes ion exchange resins) in the form of non-ionized crosslinked polymer resins and / or microporous charcoal resins, for the treatment of hot industrial water. This treatment, which may constitute a pretreatment for subsequent steps, such as reverse osmosis, ion exchange or ion deionization (EDI) demineralisation, effectively reduces the pollution to insoluble compounds, materials in question. suspension, and soluble organic matter. Since the process according to the invention does not require the cooling of the waters to be treated, the energy balance thereof is improved compared with the processes of the prior art which implement such a cooling step. According to a preferred variant, said process further comprises a centrifugation step of said concentrate obtained at the end of the filtration step leading to the obtaining of a hot aqueous phase and a step of returning it at the top of the said filtration step. This step further improves the energy efficiency of the process, a large part of the calories carried by the concentrate is thus not unnecessarily lost, which is particularly interesting when the treated water is intended to be reused at a high temperature. , for example to be transformed into steam). The present invention will find its application for the treatment of any type of hot industrial water, in practice having a temperature greater than 55 ° C and less than or equal to 98 ° C. However, according to a particularly advantageous variant, the process will be applied to the production water of oil or gas fields, said insoluble pollutants then being constituted by hydrocarbons. In practice, these waters have an insoluble hydrocarbon concentration of between 10 and 3000 mg / l and a concentration of suspended solids of between 30 and 500 mg / l. Their temperature can go up to 98 ° C. On oil or gas fields, water is very generally scarce and expensive. A constant preoccupation of the operators of these sites is to limit water consumption, especially by reusing industrial waste water. Thus, in this case as possibly in others, the method according to the invention further includes a step of recovering said waters at the end of said adsorption step with a view to their industrial re-use. According to one embodiment of the process according to the invention, use will be made of a single specific adsorbent resin dedicated to the elimination of a target organic compound.

According to other embodiments, said adsorption step will be carried out on two or more adsorbent resins allowing the elimination of one or more organic compounds. The choice of the adsorbent resin or resins will be made according to the nature and the concentration of pollutant (s) present (s) in the effluents to be treated.

Preferably, the method according to the invention comprises a stage of regeneration in situ of said at least one adsorbent resin. Such a regeneration step allows the reuse of the resins and their maintenance in optimal operating state in terms of organic matter removal efficiency and adsorption capacity.

Advantageously, said stage of regeneration in situ of said at least one adsorbent resin is carried out by a regeneration medium selected from the group consisting of water vapor heated to a temperature of between 120 ° C. and 200 ° C., preferentially between 120 ° C and 150 ° C, a low-boiling solvent, a base, an acid, or by the combination of two or more of these regeneration media. According to one variant, said regeneration medium is a low-boiling solvent, such as an alcohol or a ketone, the process then furthermore comprising a subsequent step of recycling said solvent by evaporation, leading to the obtaining of two phases. a condensed phase consisting of regenerated solvent that can be reused in a subsequent step of in situ regeneration of the at least one adsorbent resin and an organic phase consisting of adsorbed organic materials. According to another variant, said regeneration medium is water vapor, the process then further comprising a subsequent step of condensation of said water vapor leading to the production of two phases: an aqueous phase consisting of water saturated with organic compounds, and an organic phase consisting of adsorbed organic materials. In this case, the process also includes, preferably, a step of treating said aqueous phase consisting of water saturated with organic compounds, by passing it on said at least one adsorbent resin so as to de-saturate it with organic compounds and leading to a water suitable for reuse in a subsequent stage of regeneration in situ of said at least one adsorbent resin. When said industrial water treated using the process according to the invention is production water from oil and / or gas fields, said organic phase consisting of adsorbed organic matter obtained during the regeneration of the resin consists of oil and various organic materials. such as benzene, toluene, xylene, ethylbenzene and styrene which can thus be recovered. The invention then allows the recovery of organic compounds as products, which was not allowed by the prior art. The present invention also relates to any installation for carrying out the method described above characterized in that it comprises: - means for supplying industrial water; at least one ultrafiltration or microfiltration unit on membranes, said membranes being chosen from the group consisting of immersed membranes made of polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) tubular membranes; at least one column of adsorbent resin chosen from the group consisting of non-ionized crosslinked polymer resins and microporous charcoal resins; means for discharging treated water; said at least one column being provided upstream of said at least one filtration unit. Preferably, the plant comprises means for centrifuging the concentrate from said at least one ultrafiltration or micro-filtration unit and a recycling line for rerouting the aqueous phase from said centrifugation means at the head of said unit. .

Advantageously, the plant according to the invention comprises means for regenerating said at least one resin, using at least one regeneration medium selected from the group consisting of water vapor heated to a temperature of between 120 ° C and 200 ° C, preferably between 120 ° C and 150 ° C, a low-boiling solvent, a base, an acid, or by the combination of two or more of these regeneration media. When the regeneration medium is a low-boiling solvent, such as ethanol, the installation preferably comprises means of recycling by evaporation / condensation of said solvent after passing over said at least one column. When the regeneration medium is steam, the installation preferably comprises means for condensing the water vapor after passing on said at least one column, means for conveying the aqueous phase thus obtained at the head of said column, and recovery means at the bottom thereof of a water capable of being heated to give regeneration vapor. Detailed description of an embodiment of the invention. The invention, as well as the various advantages that it presents, will be better understood, thanks to the description which follows of an embodiment according to this one, given by way of illustration and not limitation. This embodiment is described with reference to Figure 1 which shows a schematic view of a pilot plant implementing a method according to the invention for the treatment of production water from oil fields. The pilot plant comprises means 1 for supplying polluted water to be treated to an ultrafiltration pretreatment unit employing two ultrafiltration membrane modules 2,3 mounted in cascade. The membranes of these modules, available commercially, are polyvinylidene fluoride (PVDF). They are attached to a polyester potting and the average diameter of their pores is 30 nm. This filtration unit allows the removal of suspended solids and insoluble hydrocarbons in water, in practice free oils, contained in the effluents. The recovery of the insoluble hydrocarbons stopped by the membranes is carried out by separating the cumulative materials on the interface of the membranes, corresponding to the concentrate, heating and centrifugation. The heating is carried out in a tank 21 and centrifugation in a centrifuge 22. These hydrocarbons are recovered in 95% yield in recoverable form through line 20. The pilot plant also includes feed means 11 and means discharging 12 of a solution of washing reagent in situ ultrafiltration membranes. After having undergone this ultrafiltration step, the effluents are directed, in the case of the example, to an optional buffer tank 13 and then directed to two columns mounted in series 4.5 containing two specific resins.

The first column 4 contains a commercially available nonionized crosslinked polymeric resin (resin 1) selected for its ability to adsorb aromatic compounds such as BTEX (Benzene, Toluene, Ethylbenzene, Xylene) and polycyclic compounds such as PAHs ( eg naphthalene); the characteristics of this resin are given in Table 1 below: Physical and chemical properties Neutral ionic form Functional group none Matrix Cross-linked polystyrene Structure Porous beads Coefficient of uniformity 1.1 max Average size of beads 0.44 to 0.54 mm Bulk density 600 g / I Water retention capacity 600 g / kg resin + / - 5% Specific surface area (BET method) 800 m2 / g approx. Pore volume 1.2 cm3 / g approx. Average pore diameter 5 at 10 nm Stability at pH 0 to 14 Stability at temperature -20 ° C to 120 ° C Table 1 The second column 5 contains a microporous char resin (resin 2), also commercially available, selected for its ability to fix more advantageously trace compounds. The characteristics of this resin are given in Table 2 below: Physical and chemical properties Neutral ionic form Functional groups none Matrix carbon Particle size 0.4 to 0.8 mm (> 90%) Bulk density 550 to 650 g / I +/- 5% Specific surface area (BET method) 1200 m2 / g approximately Pore volume approx. 0.15 cm3 / g Pore average diameter 8 nm Stability at temperature -20 ° C to 300 ° C Table 2 After passing through in columns 4 and 5, the treated water is discharged through a pipe 10. The pilot plant comprises regeneration means 8, 9 of the resins, either with water vapor 8 or with a solvent 9. such means, the materials adsorbed on the resins can be detached therefrom. When the regeneration is carried out by means of a solvent, the organic-laden solvent may, in whole or in part, be recovered at the outlet of the columns through line 19 in order to undergo evaporation leading to the obtaining of two phases: one phase condensed, consisting of recycled regenerated solvent, and returned to line 16, and an organic phase consisting of adsorbed organic material. The waste is discharged through line 18. When the regeneration is carried out with steam, it can be evacuated after condensation through line 17, the condensation leading to the production of two phases: an aqueous phase consisting of water saturated with organic compounds, and an organic phase consisting of adsorbed organic materials. The aqueous phase can then be passed through the first column of adsorbent resin so as to desaturate it in organic compounds, this leading to a water that can be reused to make steam during a subsequent stage of regeneration of resins in situ. . The characteristics of the production water of a petroleum field treated with the installation described above are set out in Table 3 below. Parameters Unit Range of Value Temperature ° C 20 - 70 pH upH 6.5 - 7.5 Chloride mg / L 2500 - 5000 Sulfate mg / L 500 - 2000 Alkalinity ppm CaCO3 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 L 1 - 30 Naphthalene mg / L 0.5 - 5 Benzyl alcohol mg / L 5 - 30 2-methyl phenol mg / L 1-5 3-methyl phenol mg / L 1-5 4-methyl phenol mg / L 1- 5 TOC mg / L 20 - 150 Table 3 In terms of treatment performance, ultrafiltration has reduced the concentration of oils and suspended solids to levels according to Table 4 below. Compounds Concentration in the treated effluent (in mg / 1) Abatement rate (in%) Insoluble hydrocarbons 0.2 to 0.5 99 to 99, 96 Suspended substances 0.1 to 0.5 99 to 99.9 Polyaromatic Hydrocarbons 20 to 50 80 to 90 Table 4 The resins, for their part, made it possible to obtain the reductions summarized in Table 5 below: Resin 1 (%) Resin 2 (%) Benzene 99.5 ± 0, 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 Naphthalene 99.7 ± 0.3 99.9 ± 0.1 Benzyl alcohol 84.0 ± 1.0 99.5 ± 0.5 2 -methyl phenol 99.5 ± 0.5 99.9 ± 0.1 3-methyl phenol 99.5 ± 0.5 99.9 ± 0.1 4-methyl phenol 99.5 ± 0.5 99.9 ± 0.1 TOC 50.0 ± 5.0 85.0 ± 5.0 Table 5 In terms of regenerability, the resins were regenerated with steam. This regeneration has allowed the adsorption capacities of the resins to be recovered at 80%, which means that the production cycle of new resins is 20% higher than that used. In addition, the condensation of the vapor made it possible to separate the organic materials adsorbed on the first resin. The conditions and results of this regeneration are shown in the following Table 6. Cycle time 7 days Characteristic of the vapor Resin 1: 125 ° C to 2.4 bar Resin 2: 150 ° C to 5.0 bar% of recovered material 99% ± 1 Table 6 Ethanol regeneration gave the same results performance than steam, in terms of recovery of adsorption capacities and levels of organic materials recoverable after evaporation and recovery of ethanol. With the regeneration mode combining the vapor as a regeneration medium and ethanol, one out of ten regeneration cycles showed a better performance in terms of recovery rate of the adsorption capacity of the resins, which is found increased and reaching 95%.

Claims (17)

REVENDICATIONS1. A method of treating industrial water having a temperature greater than 55 ° C and less than or equal to 98 ° C and containing insoluble pollutants, suspended solids, and soluble organic material, said process comprising a micro-filtration step or ultrafiltration device on membranes leading to a filtrate and a concentrate, characterized in that said membranes are chosen from the group consisting of immersed polytetrafluoroethylene (PTFE) membranes and tubular polyvinylidene fluoride (PVDF) membranes, and in that it comprises a step of adsorption of the suspended matter contained in said filtrate, said adsorption step being carried out on at least one adsorbent resin selected from the group consisting of nonionized crosslinked polymeric resins and microporous charcoal resins. 2. Method according to claim 1 characterized in that it comprises a centrifugation step of said concentrate leading to obtaining a hot aqueous phase and a step of returning it at the head of said filtration step. 3. Method according to any one of claims 1 or 2 characterized in that said hot industrial water is production water oil or gas fields, said insoluble pollutants being constituted by hydrocarbons. 4. Method according to claim 3 characterized in that said industrial waters have an insoluble hydrocarbon concentration of between 10 and 3000 mg / I, a concentration of suspended solids of between 30 and 500 mg / l. 5. Method according to any one of claims 1 to 4 characterized in that it comprises a step of recovering said water at the end of said adsorption step for industrial re-use. 6. Method according to any one of claims 1 to 3 characterized in that said adsorption step is carried out on a specific adsorbent resin dedicated to the removal of a target organic compound. 7. Method according to any one of claims 1 to 3 characterized in that said adsorption step is carried out on two or more adsorbent resins for the removal of one or more organic compounds. 8. Method according to any one of claims 1 to 7 characterized in that it comprises a step of regeneration in situ of said at least one adsorbent resin. 9. Method according to claim 8 characterized in that said in situ regeneration step of said at least one adsorbent resin is performed by a regeneration medium selected from the group consisting of water vapor heated to a temperature between 120 ° C and 200 ° C, preferably between 120 ° C and 150 ° C, a low-boiling solvent, a base, an acid, or by the combination of two or more of these regeneration media. 10. The method of claim 9 characterized in that said regeneration medium is a low-boiling solvent, such as alcohol, and in that it further comprises a subsequent step of recycling said solvent by evaporation. leading to the production of two phases: a condensed phase consisting of regenerated solvent that can be reused in a subsequent step of in situ regeneration of the at least one adsorbent resin and an organic phase consisting of adsorbed organic materials. 11. The method of claim 9 characterized in that said regeneration medium is water vapor and in that it further comprises a subsequent step ofondensation of said water vapor leading to obtaining two phases: an aqueous phase consisting of water saturated with organic compounds, and an organic phase consisting of adsorbed organic materials. 12. The method of claim 11 characterized in that it comprises a step of treating said aqueous phase consisting of water saturated with organic compounds of passing it on said at least one adsorbent resin so as to de-saturate it. organic compounds and leading to a water suitable for reuse in a subsequent stage of regeneration in situ of said at least one adsorbent resin. 13. Installation for carrying out the method according to any one of claims 1 to 12 characterized in that it comprises: - means for supplying industrial water; at least one ultrafiltration or microfiltration unit on membranes, said membranes being chosen from the group consisting of submerged polytetrafluoroethylene (PTFE) membranes and polyvinylidene fluoride (PVDF) tubular membranes; at least one column of adsorbent resin chosen from the group consisting of non-ionized crosslinked polymer resins and microporous charcoal resins; means for discharging treated water; said at least one column being provided upstream of said at least one filtration unit. 14. Installation according to claim 13 characterized in that it comprises means for centrifuging the concentrate from said at least one ultra-filtration or micro-filtration unit and a recycling line for rerouting the aqueous phase from said centrifugation means at the head of said unit. 15. Installation according to claim 13 or 14 characterized in that it comprises means for regenerating said at least one resin, using at least one regeneration mediate selected from the group consisting of water vapor heated to a temperature between 120 ° C and 200 ° C, preferably between 120 ° C and 150 ° C, a low-boiling solvent, a base, an acid, or by the combination of two or more of these media regeneration. 16. Installation according to claim 15 characterized in that it comprises recycling means by evaporation / condensation of said solvent after passing over said at least one column. 17. Installation according to claim 15 characterized in that it comprises means for condensing water vapor after passing over said at least one column, means for conveying the thus aqueous phase obtained at the head of said column. and recovery means at the bottom thereof of a water capable of being heated to give regeneration vapor.