WO2013064484A1

WO2013064484A1 - Method of treating oily waters

Info

Publication number: WO2013064484A1
Application number: PCT/EP2012/071455
Authority: WO
Inventors: Marcelo COSTA; Kaj Jansson; Kari Saari
Original assignee: Kemira Oyj
Priority date: 2011-11-01
Filing date: 2012-10-30
Publication date: 2013-05-10

Abstract

A method for treating oily waters by adding to the oily water at least one peracid and/or its salt, and at least one flocculating polymer and/or at least one inorganic coagulant, in any order, to produce a clarified water phase and an organic phase, which may be separated from each other.

Description

METHOD OF TREATING OILY WATERS

Field of the art

The present disclosure relates to a method of treating water comprising oil, wherein a clarified water phase and an organic phase is formed.

Background

A major problem for industry handling oils relates to oil containing waters obtained during the extraction, processing and transportation of the oil, i.e. the oily water produced alongside the oil, and of the liquids from washing of equipment, instruments, production units, means of transport and storage facilities etc. Industries handling oils refers to industries working with all types of oils, e.g. petrochemical oil, vegetable oils and essential oils. Petrochemical oil containing waters usually contain in addition to oil, soluble toxic

contaminants such as sulphides, benzenes, toluenes, xylenes and

polyaromatic hydrocarbons. To avoid pollution of the environment the water should be separated from the oil and the oil recovered. Clarified water obtained from the treatment of oily water (water containing oil) can be discharged into the open sea, injected into injection wells in order to increase the recovery of crude oil contained in a reservoir, or forwarded to municipal or industrial wastewater systems for optional further treatments. The separated oily phase may also be processed further in different processes.

Different types of additives are used today to separate an oily phase from the water phase.

US 3 948 770 discloses a method for clarifying oily water wherein a flocculant mixture comprising a sodium or calcium montmorillonite clay and an anionic polyelectrolyte is used.

EP 2 058 040 discloses a process for treating effluents from oil production units to remove the oil, wherein an oxidizing agent, being a mixture of hydrogen peroxide and sodium hypochlorite, is used to promote a phase separation and then segregate the treated effluents into a phase with predominantly water and another phase containing oil. WO 2010/045090 discloses a process for treating wellbore fluid, wherein aqueous wellbore fluid is contacted with ozone and separated into an organic phase and a clarified water phase.

Summary

In view of the foregoing, there is a need for new ways to separate an oily phase from oil containing waters in a satisfactory manner. There also exists a desire to improve the clarification of separated waters.

The present embodiments relate to a method of treating oily waters, i.e. water containing oil, wherein the waters are separated into a clarified water phase and an organic phase. The clarified water shows a decreased colour and turbidity.

The method according to the present embodiments shows an improved colour and turbidity for clarified and separated waters.

According to the present embodiments the method relates to treating oily waters, wherein said water is brought in contact with and allowed to react with at least one peracid and/or its salt, and at least one flocculating polymer and/or at least one inorganic coagulant, in any order, wherein a clarified water phase and an organic phase is formed.

The oily waters to be treated may contain petrochemical oil(s), vegetable oil(s) or essential oil(s), or mixtures thereof. Examples of vegetable oils are palm, olive, soybean, rapeseed, corn, canola, sunflower, safflower, peanut, cottonseed, coconut, rice bran, and sesame oil. Examples of essential oils are lavender, peppermint, rose, cinnamon, clove, sandalwood and eucalyptus oil.

The oily waters to be treated may originate from the vegetable oil, essential oil and/or the petroleum industry. The vegetable oil industry and the petroleum industry include the global processes of exploration, extraction, refining, transporting (e.g. by pipeline, ship, or truck), sales of the oil products and naturally also includes accidental and/or non-accidental discharges of the oil products into the surroundings/environment. Short description of the drawings

Figure 1 is a photo of three containers comprising untreated oily water, oily water treated according to a conventional technique with hydrogen peroxide and sodium hydroxide, and oily water treated according to the present embodiments (PFA 25 mg/l, 30 min), respectively, of Example 1 .

Fig 2a discloses a photo of a container with untreated oily water of Example 2.

Fig 2b discloses a photo a container comprising oily water treated according to the embodiment of Example 2.

Fig 3a discloses a photo of a container with untreated oily water of

Example 3.

Fig 3b to 3d discloses photos of containers comprising oily water treated according to the embodiment of Example 3, wherein in each container a different flocculation polymer have been used.

Fig 4a discloses a photo of a container with untreated oily water of

Example 4.

Fig 4b discloses a photo of a container comprising oily water treated according to the embodiment of Example 4.

Detailed description of the exemplary embodiments

The method according to the present embodiments relates to treating water, e.g. raw water, process water and waste water, comprising oil, which oil may be chosen from petrochemical, vegetable and essentail oil, wherein the method involves said water being brought in contact with and allowed to react with at least one peracid and/or its salt, and at least one flocculating polymer and/or at least one inorganic coagulant. The different compounds may be added in any order and/or combination. In an exemplary embodiment the method involves addition of all three mentioned compounds, i.e. at least one peracid and/or its salts, at least one flocculation polymer and at least one inorganic coagulant. The water comprising oil will after reaction with said added compounds result in separated phases. The treated water will have a clarified water phase and an organic phase. The clarified water phase comprises predominantly water. For example, the clarified water may have a hydrocarbon content of which is less than the ingoing water to be treated. The treated clarified water phase and the organic phase may be separated from each other by means of at least one separating device. The separation of the water phase and the organic phase may be performed by decantation, centrifugation, and/or filtration. An organic phase part may be separated from the liquid clarified water phase by means of e.g. a decanting device, a centrifuge and/or a filter.

According to the exemplary embodiments, the different compounds to be added and reacted with the water containing oil can be added in various combinations and/or various orders, and each compound may occur and be added more than once in the method.

According to one embodiment the at least one inorganic coagulant or the at least one flocculating polymer may be added before, after or

simultaneously with the at least one peracid and/or its salt to the water comprising oil.

According to another embodiment the at least one peracid and/or its salt, the at least one flocculating polymer and the at least one inorganic coagulant are added to the water comprising oil simultaneously.

According to another embodiment the at least one peracid and/or its salt, the at least one flocculating polymer and the at least one inorganic coagulant are added to the water comprising oil in the following order: (1 ) the at least one inorganic coagulant, (2) the at least one flocculating polymer and (3) the peracid and/or its salts; or in the following order: (1 ) the peracid and/or its salt, (2) the at least one inorganic coagulant and (3) the at least one flocculating polymer.

According to another embodiment the at least one peracid and/or its salt, the at least one flocculating polymer and the at least one inorganic coagulant are added to the water comprising oil in the following order: the at least one inorganic coagulant and the at least one flocculating polymer are added simultaneously, followed by the peracid and/or its salt; or in the following order: the peracid and/or its salt is added, followed by the at least one inorganic coagulant and the at least one flocculating polymer added simultaneously. According to another embodiment the at least one peracid and/or its salts, the at least one flocculating polymer and the at least one inorganic coagulant are added to the water comprising oil in the following order: the at least one inorganic coagulant, followed by the at least one flocculating polymer and the peracid and/or its salt added simultaneously; or in the following order: the at least one flocculating polymer and the peracid and/or its salt are added simultaneously, followed by the at least one inorganic coagulant. Note that peracid and/or its salt, flocculating polymer and inorganic coagulant may each be added more than one time in the embodiments. The addition of e.g. the polymer may be divided into two portions, leaving the method to include a part of the polymer to be added and therafter either acid and/or its salt and/or coagulant is added and then followed by the remaining part of the polymer. This divided addition may apply for all three said components.

In various embodiments, at least one peracid and/or its salts may be used. Exemplary salts of the at least one peracid include ammonium, sodium and potassium salts. The peracid may be organic or inorganic. Exemplary inorganic peracid compounds include peroxocarbonic acid, peroxysulfuric acids and/or their salts, i.e. either the peroxymonosulfuric acid, or the peroxydisulfuric acid. In an exemplary embodiment the peracid is a

peroxymonosulfuric acid and/or its salts. In another exemplary embodiment, the peracid is ammonium peroxymonosulfate, sodium peroxymonosulfate or potassium peroxymonosulfate. Exemplary organic peracid compounds include percarboxylic acids and/or their salts. Exemplary percarboxylic acids are selected from the group consisting of performic acid, peracetic acid, perpropionic acid, perbutyric acid, perisobutyric acid, perheptoic acid, peroctanoic acid, perglycolic acid, perglutaric acid, persuccinic acid, perlactic acid, percitric acid, perdecanoic acid, percrotonic acid, perisocrotonic acid, peracrylic acid, permethacrylic acid, percyclohexanoic acid, perbenzoic acid, pertoluic acid, monoperphthalic acid and per-m-chlorobenzoic acid. In an exemplary embodiment, the peracid may beperformic acid, peracetic acid, perpropionic acid, perbutyric acid, perisobutyric acid, or combinations thereof. In another exemplary embodiment, the peracid is performic acid and/or peracetic acid. In various exemplary embodiments, the at least one peracid and/or its salts is chosen from peroxysulfuric acids and percarboxylic acids and their salts, or mixtures thereof. In some embodiments, the at least one peracid is chosen from percarboxylic acids and their salts, or mixtures thereof. Examplary percarboxylic acids are perform ic acid and peracetic acid. Percarboxylic acids may also be in the form of an equilibrium mixture comprising percarboxylic acid, carboxylic acid, hydrogen peroxide and water. The at least one peracid and/or its salt may be selected from percarboxylic acid and/or its salts.

The pH after the addition of the peracid and/or its salt may be in the range of 4 to 9, or 5 to 9, or 6 to 8.5. Peracid and/or its salt may be added to the oily water to be treated in an amount of about 1 to 5000 mg per liter of oily water to be treated, or 1 to 2000 mg per liter of oily water, or 1 to 1000 mg per liter of oily water, or 1 to 500 mg per liter of oily water, or 1 to 250 mg per liter of oily water. The peracid and/or its salt may be allowed to react with the water comprising oil for about 0.5 minutes to 2 hours, or 0.5 to 60 minutes, or 1 to 30 minutes, or 1 to 20 minutes.

In the exemplary embodiments, types of inorganic coagulants may be used, such as, for example, aluminium, calcium and iron salts. Exemplary inorganic coagulants include alum, aluminium chlorohydrate, aluminium sulfate, aluminium chloride, aluminium hydroxide, polyaluminium chloride (PAC), iron chloride, iron sulfate, iron chloride sulfate, calcium oxide, calcium hydroxide, and/or calcium chloride, and mixtures thereof. In an exemplary embodiment, the inorganic coagulant may be iron chloride sulphate, aluminium chloride, aluminium sulphate, or mixtures thereof.

The inorganic coagulant may be added to the water comprising oil in an amount of about 1 to 3000 mg per liter of oily water, or 10 to 1000 mg per liter of oily water, or 50 to 500 mg per liter of oily water. If the inorganic coagulant is polyaluminium chloride it may contain about 4-6%, e.g. about 5- 5.5%, aluminium. Also, the inorganic coagulant may be allowed to react with the water comprising oil for about 0.1 minutes to 2 hours, or 0.1 to 60 minutes, or 0.1 to 30 minutes, or 0.1 to 20 minutes. Flocculating polymers can be used in the exemplary embodiments. Exemplary flocculating polymers include anionic, cationic, non-ionic, and amphoteric polymers, and mixtures thereof. Flocculating polymers may be chosen from polyamines, polyepiamine, polyDADMAC, Mannich products, poly(ethylene)imines, polyacrylamides, polyethylene oxide, natural polymers e.g. starch, modified starch and polysaccharides, glues, and rubber. In an exemplary embodiment, the flocculating polymer is a polyacrylamide. The flocculating polymer may be added to the water comprising oil typically in an amount of about 0.5 to 10 mg per liter of oily water, or 1 to 4 mg per liter of oily water, or 1 to 3 mg per liter of water comprising oil. The flocculating polymer may be allowed to react with the water comprising oil for 0.1 minutes to 2 hours, or 0.1 to 60 minutes, or 0.1 to 30 minutes, or 0.1 to 20 minutes.

By using the method of the embodiments process oil and particles present in the organic phase after the reaction with the above mentioned components may be separated from the water phase. The present process leaves the clarified water phase with a reduced colour and turbidity.

Examples

Example 1

A sample of an oily production water from an on shore terminal that had a TOG (total oil & grease) content of 58 mg/l, a turbidity of 240 NTU and a redox potential of -56 mV was mixed with a performic acid equilibrium solution (Desinfix 135 Kemira Oyj) comprising 13.5 wt% performic acid. The dosage of performic acid (PFA) as an active substance was 25 mg/l and 50 mg/l of the treated water. The mixture was allowed to react for 3 min or 30 min under mixing. After said the reaction the pH was adjusted to about 7 with NaOH-solution and 100 mg/l of polyaluminum chloride solution (PAC) (PAX- 1060, Kemira Oyj) and 2 mg/l of flocculating polymer (Superfloc 1883 RS, Kemira Oyj), based on the treated water, were added. The mixing was continued for 5 min and after that the water was analyzed. A comparative experiment was made using the current practice (NaOH + H2O2 at pH 9) to treat such oily waters, wherein 500 mg/l H2O2 as an active substance, based on the treated water, was added, followed by mixing for 3 minutes, thereafter the NaOH wass added, followed by mixing for 2 minutes.The results can be seen from the Table 1 and from the Fig. 1 .

Table 1

Example 2

A sample of an oily production water from an on shore terminal that had a color of 370 units/I on the Pt-Co scale, a turbidity of 2100 NTU, total suspended solids (TSS) of 220 mg/l, and an initial pH of about 6.7 was mixed with a peracetic acid equilibrium solution comprising 33 wt-% peracetic acid. The dosage of peracetic acid (PAA) as an active substance was 200 mg/l of the treated water. The mixture was allowed to react for 3 min under mixing. After the reaction, 100 mg/l of a polyaluminum chloride solution (PAX-1060, Kemira Oyj) and after that 2 mg/l of a flocculating polymer (Superfloc A 1883, Kemira Oyj), based on the treated water, were added. The mixing was continued for 5 min and after that the water was analyzed. The results can be seen from the Table 2 and from the Fig. 2a-b. Table 2

Example 3

A sample of an oily production water from an on shore terminal that had a color of 370 units/l on the Pt-Co scale, a turbidity of 2100 NTU and total suspended solids (TSS) of 220 mg/l and an initial pH of about 6.7 was mixed with a peracetic acid equilibrium solution comprising 33 wt-% peracetic acid. The dosage of peracetic acid (PAA) as an active substance was 200 mg/l of the treated water. The mixture was allowed to react for 3 min under mixing. After the reaction, 100 mg/l of polyaluminum chloride solution (PAX-1060, Kemira Oyj) and after that 2 or 8 mg/l of one of three different flocculating polymers (Superfloc A 1883, A 1883 LWM and C 1592 RS, Kemira Oyj), based on the treated water, were added. The mixing was continued for 5 min and after that the water was analyzed. The results can be seen from the Table 3 and from the Fig. 3a-d.

Table 3

Treatment Figure PAA PAC Polymer Turbidity Color Final pH

(mg/l) (mg/l) (mg/l) (NTU) (units/l) untreated 3a 2100 370 6.7

A 1883 3b 200 100 2 12.8 47 6.7

A 1883 200 100 8 10.3 64 7.0

A 1883 3c 200 100 2 15.4 60 6.7 LMW

C 1592 3d 200 100 2 15.5 57 6.8 RS Example 4

A sample of an oily production water from an on shore terminal that had a color of 374 units/I on the Pt-Co scale, a turbidity of 2100 NTU, total suspended solids (TSS) of 590 mg/l, a TOG content of 1 18 mg/l and an initial pH of about 8.0 was mixed with 100 mg/l of a polyaluminum chloride solution (PAX-1060, Kemira Oyj). The mixture was allowed to react for 3 min under mixing. After the reaction, 2 mg/l of flocculating polymer (Superfloc A 1883, Kemira Oyj) was added and peracetic acid equilibrium solution comprising 33 wt-% peracetic acid. The dosage of the peracetic acid (PAA) as an active substance was 200 mg/l of the treated water. The mixing was continued for 5 min and after that the water was analyzed. The results can be seen from the Table 4 and from the Fig. 4a-b.

Table 4

Treatment Figure PAC Polymer PAA Turbidity Color Final

(mg/l) (mg/l) (mg/l) (NTU) (units/I) PH untreated 4a 2100 374

treated 4b 100 2 200 2.5 108 7.5

Claims

1 . A method of treating oily waters, comprising:

adding to the oily water at least one peracid and/or its salt, at least one flocculating polymer and/or at least one inorganic coagulant, to produce a clarified water phase and an organic phase.

2. The method according to claim 1 , wherein the at least one inorganic coagulant is selected from aluminium, calcium and iron salts, or mixtures thereof; preferably the at least one inorganic coagulant is selected from the group consisting of alum, aluminium chlorohydrate, aluminium chloride, aluminium sulfate, aluminium hydroxide, polyaluminium chloride, iron chloride, iron sulfate, iron chloride sulfate, calcium oxide, and calcium hydroxide, or mixtures thereof.

3. The method according to claim 1 or 2, wherein the at least one flocculating polymer is selected from anionic, cationic, non-ionic, and amphoteric polymers, or mixtures thereof;

preferably the at least one flocculating polymer is selected from the group consisting of polyacrylamides, polyamines, polyepiamine, polyDADMAC,

Mannich products, poly(ethylene)imines, polyethylene oxide, natural polymers e.g. starch, modified starch and polysaccharaides, glues, and rubber;

preferably the at least one flocculating polymer is selected from

polyacrylamides.

4. The method according to anyone of the claims 1 -3, wherein the at least one peracid and/or its salt is selected from peroxocarbonic acid,

peroxysulfuric acids and percarboxylic acids and their salts, and preferably selected from percarboxylic acid and its salts.

5. The method according to claim 4, wherein the salt of said peroxysulfuric acids and/or percarboxylic acids is a salt chosen from ammonium, sodium and potassium acid salt.

6. The method according to claim 4 or 5, wherein the at least one

percarboxylic acid is selected from performic acid, peracetic acid,

perpropionic acid, perbutyric acid, perisobutyric acid, perheptoic acid, peroctanoic acid, perglycolic acid, perglutaric acid, persuccinic acid, perlactic acid, percitric acid, perdecanoic acid, percrotonic acid, perisocrotonic acid, peracrylic acid, permethacrylic acid, percydohexanoic acid, perbenzoic acid, pertoluic acid, monoperphthalic acid and per-m-chlorobenzoic acid, and more preferably chosen from performic acid, peracetic acid, perpropionic acid, perbutyric acid, perisobutyric acid, and more preferably from performic acid and/or peracetic acid selected, or mixtures thereof.

7. The method according to anyone of the claims 1 -6, wherein the at least one inorganic coagulant or the at least one flocculating polymer are added before, after or simultaneously with the at least one peracid and/or its salt to the water comprising oil.

8. The method according to anyone of the claims 1 -6, wherein the at least one peracid and/or its salt, the at least one flocculating polymer and the at least one inorganic coagulant are added to the water comprising oil:

(a) simultaneously;

(b) in the following order: (1 ) the at least one inorganic coagulant, (2) the at least one flocculating polymer and (3) the peracid and/or its salt;

(c) in the following order: (1 ) the peracid and/or its salt, (2) the at least one inorganic coagulant and (3) the at least one flocculating polymer;

(d) in the following order: the at least one inorganic coagulant and the at least one flocculating polymer are added simultaneously, followed by the peracid and/or its salt;

(e) in the following order: the peracid and/or its salt is added, followed by the at least one inorganic coagulant and the at least one flocculating polymer added simultaneously; (f) in the following order: the at least one inorganic coagulant, followed by the at least one flocculating polymer and the peracid and/or its salt added simultaneously; or

(g) in the following order: the at least one flocculating polymer and the peracid and/or its salt are added simultaneously, followed by the at least one inorganic coagulant.

9. The method according to anyone of the claims 1 -8, wherein the clarified water phase and the organic phase are separated from each other, into at least two phases, by means of at least one separating device.

10. The method according to claim 9, wherein the separation of the water phase and the organic phase is performed by decantation, centrifugation, filtration.

1 1 . The method according to any of the claims 1 -10, wherein the pH after the addition of the peracid and/or its salt is in the range of 4 to 9, preferably 5 to 9, and preferably 6 to 8.5.

12. The method according to any of the claims 1 -1 1 , wherein the peracid and/or its salt is added to the water comprising oil in an amount of 1 to 5000 mg per liter of oily water to be treated, preferably 1 to 2000 mg per liter of oily water, preferably 1 to 1000 mg per liter of oily water, preferably 1 to 500 mg per liter of oily water and more preferably 1 to 250 mg per liter of oily water.

13. The method according to any of the claims 1 -12, wherein the inorganic coagulant is added to the water comprising oil in an amount of 1 to 3000 mg per liter of oily water, preferably 10 to 1000 mg per liter of oily water, and preferably 50 to 500 mg per liter of oily water.

14. The method according to any of the claims 1 -13, wherein the flocculating polymer is added to the water comprising oil in an amount of an amount of about 0.5 to 10 mg per liter of oily water, preferably 1 to 4 mg per liter of oily water, and more preferably 1 to 3 mg per liter of oily water.

15. The method according to any of the claims 1 -14, wherein peracid and/or its salt is allowed to react with the water comprising oil for 0.5 minutes to 2 hours, preferably 0.5 to 60 minutes, preferably 1 to 30 minutes, preferably 1 to 20 minutes;

and

inorganic coagulant is allowed to react with the water comprising oil for about 0.1 minutes to 2 hours, preferably 0.1 to 60 minutes, preferably 0.1 to 30 minutes, and more preferably 0.1 to 20 minutes;

and/or

flocculating polymer is allowed to react with the water comprising oil for 0.1 minutes to 2 hours, preferably 0.1 to 60 minutes, preferably 0.1 to 30 minutes, and more preferably 0.1 to 20 minutes.

16. The method according to any of the claims 1 -15, wherein the oily water to be treated orginates from the vegetable oil, essential oil and/or petroleum industry.