Process for the concentration of amine water

Abstract

A process for concentrating amine water is achieved by dehydrating the amine water by membrane distillation at a temperature ranging from 30 C. to 95 C. and at a pressure ranging from 1.0 bar to 1.5 absolute bar.

Claims

1. A process for concentrating amine water, the process comprising: heating the amine water to a temperature ranging from 30 C. to 95 C., wherein the amine water comprises water and nitrogen-containing chemical compounds and the amine water has a concentration of total nitrogen that ranges from 10,000 mg/L to 100,000 mg/L, a sulfur sulfide concentration that ranges from 1,000 mg/L to 10,000 mg/L, a boron concentration that ranges from 10 mg/L to 1,000 mg/L, and a chemical oxygen demand that ranges from 100,000 mg/L to 1,000,000 mg/L; feeding the heated amine water to a first sector of a membrane distillation unit, wherein the membrane distillation unit comprises a membrane between a second sector of the membrane distillation unit and the first sector, whereby a distillate in vapour phase permeates through the membrane into the second sector, leaving a concentrate in the first sector; maintaining the first sector and the second sector at atmospheric pressure; flowing a carrier gas through the second sector to saturate the carrier gas with the distillate in vapour phase in a saturated stream; and cooling the carrier gas saturated with vapor distillate by heat exchange with a fluid at an initial temperature ranging from 0 C. to 25 C. so that the vapor distillate condenses to yield a distillate in liquid phase and gaseous stream of the carrier gas and any non-condensable, wherein the distillate in liquid phase has a chemical oxygen demand, a concentration of total nitrogen, a concentration of boron, and a concentration of sulfur sulfide that are each at least 99% lower than the amine water fed.

2. The process according to claim 1, wherein the heating is to a temperature ranging from 40 C. to 90 C.

3. The process according to claim 1, wherein the nitrogen-containing chemical compounds are amines.

4. The process according to claim 3, wherein the amine is an alkanolamine.

5. The process according to claim 4, wherein the alkanolamine is N-methyldiethanolamine.

6. The process according to claim 1, wherein the concentration of total nitrogen ranges from 20,000 mg/L to 100,000 mg/L.

7. The process according to claim 6, wherein the concentration of total nitrogen ranges from 30,000 mg/L to 100,000 mg/L.

8. The process according to claim 1, wherein the sulfur sulfide concentration ranges from 2,000 mg/L to 10,000 mg/L.

9. The process according to claim 8, wherein the sulfur sulfide concentration ranges from 3,000 mg/L to 10,000 mg/L.

10. The process according to claim 1, wherein the chemical oxygen demand ranges from 200,000 mg/L to 1,000,000 mg/L.

11. The process according to claim 10, wherein the chemical oxygen demand ranges from 300,000 mg/L to 1,000,000 mg/L.

12. The process according to claim 1, wherein the amine water has an electrical conductivity that ranges from 500 S/cm to 150,000 S/cm.

13. The process according to claim 12, wherein the electrical conductivity ranges from 5,000 S/cm to 150,000 S/cm.

14. The process according to claim 13, wherein the electrical conductivity ranges from 10,000 S/cm to 150,000 S/cm.

15. The process according to claim 1, wherein the concentration of boron ranges from 50 mg/L to 1,000 mg/L.

16. The process according to claim 15, wherein the boron concentration ranges from 100 mg/L to 1,000 mg/L.

17. The process according to claim 1, wherein the membrane is selected from the group consisting of inorganic polymers, organic polymers, inorganic copolymers, inorganic copolymers, and combinations thereof.

18. The process according to claim 1, wherein the membrane is selected from the group consisting of: organic polymers containing halogens, organic copolymers containing halogens, organic polymers not containing halogens, organic copolymers not containing halogens, and combinations thereof.

19. The process according to claim 1, wherein the membrane is selected from the group consisting of: organic polymers containing fluorine, organic copolymers containing fluorine, organic polymers not containing fluorine, copolymers not containing fluorine, and combinations thereof.

20. The process according to claim 19, wherein the membrane is a membrane selected from the group consisting of: oxides, sulfides, zeolites, metal-organic materials, carbonaceous materials, polysilanes and their copolymers, polysiloxanes and their copolymers, polysulfones and their copolymers, polyacrylates and their copolymers, proteins, polyamides and their copolymers, polyurethanes and their copolymers, polyketones and their copolymers, polyesters and their copolymers, polysaccharides, polyethers and their copolymers, polyaromatics and their copolymers, polyolefins and their copolymers, and combinations thereof.

21. The process according to claim 20, wherein the membrane is polypropylene.

22. The process according to claim 1, further comprising maintaining the first sector and the second sector at a temperature in the range 30-95 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further aims and advantages of the present disclosure will appear more clearly from the following description and from the accompanying figures, given purely by way of a non-limiting example, which represent preferred embodiments of the present disclosure.

(2) FIG. 1 schematically illustrates a module for the concentration of amine water according to the process described and claimed in the present patent application.

(3) In the Figure the feed (1), i.e. the amine water, is heated (2), for example in a heat exchanger, before being fed to the MD membrane distillation unit in a first sector at atmospheric pressure, for example between 1 and 1.5 absolute bar (3). From here the distillate in vapour phase permeates through a polymeric membrane (10), leaving the concentrate (7) in the first sector. On the opposite side with respect to the first atmospheric pressure sector there is a second atmospheric pressure sector (4) in which carrier gas (5) flows which drags the distillate in vapour phase becoming saturated. Said saturated gaseous stream of distillate in vapour phase is cooled (6), for example in a heat exchanger, forming a distillate in liquid phase (8) and a gaseous stream containing the carrier gas and any non-condensable (9).

(4) FIG. 2 is similar to FIG. 1 where however the carrier gas (5) is static.

DETAILED DESCRIPTION OF THE DISCLOSURE

(5) The Applicant now describes in detail the process for concentrating amine water subject of the present patent application, also referring to FIG. 1.

(6) The amine water is concentrated by dehydrating it through membrane distillation (MD) conducted by maintaining the pressure between 1 and 1.5 absolute bar, definable as atmospheric pressure, and the temperature in the range 30-95 C.

(7) The amine water can preferably be an amine water which comprises water and chemical compounds containing nitrogen, characterized in that the concentration of total nitrogen varies in the range of between 10000 mg/L and 100000 mg/L. Preferably the concentration of total nitrogen in the amine water can vary in the range between 20000 mg/L and 100000 mg/L, more preferably in the range between 30000 mg/L and 100000 mg/L, still more preferably it is equal to 66000 mg/L. Preferably the process described and claimed in the present patent application allows to concentrate amine water in which the nitrogen-containing chemical compounds are the amines, more preferably an alkanolamine, still more preferably N-methyldiethanolamine.

(8) The amine water (1) is heated to temperatures in the range from 30 C. to 95 C., preferably from 40 C. to 90 C., more preferably to 70 C.

(9) For this purpose, heat exchangers external to the MD system or internal to the same system can be used, for example selected from coils, plates, or tube bundle exchangers.

(10) Once heated, the amine water is fed to one or more MD units, each comprising one or more sectors maintained at a pressure that varies in the range 1-1.5 absolute bar, definable as atmospheric pressure (3), adjacent to a polymeric membrane (10), which in turn is adjacent to one or more sectors (4) maintained at a pressure that varies in the range 1-1.5 absolute bar (atmospheric pressure).

(11) A carrier gas (5) can be fed to said MD unit in a dedicated sector maintained at a pressure which varies in the range 1-1.5 absolute bar (atmospheric pressure), distinct from that in which the amine water is fed.

(12) The carrier gas can be fed at an initial temperature which preferably varies in the range of between 10 C. and 95 C.

(13) The carrier gas can be selected from nitrogen, oxygen, carbon dioxide, methane, or mixtures thereof.

(14) The polymeric membranes used for the purposes of the present patent application are hydrophobic and porous. The term hydrophobic membrane refers to membranes characterized by a contact angle with water greater than or equal to 70, preferably in the range between 70 and 180, more preferably in the range between 100 and 150. The term porous membranes means membranes characterized by pores with a nominal diameter that varies in the range between 0.1 and 5.0 m.

(15) Said hydrophobic and porous polymeric membranes allow to obtain a vapour saturated carrier gas (distilled in vapour phase, enriched by water) and a concentrate (7). Amine water can preferably circulate with a linear speed in the range 0.3-3.0 m/s. The carrier gas can preferably circulate with a linear speed in the range 0.0-7.0 m/s, preferably between 0.1-7.0 m/s.

(16) As previously said, an MD unit comprises one or more sectors maintained at a pressure which varies in the range 1-1.5 absolute bar (atmospheric pressure) adjacent to a polymeric membrane, said membrane being in turn adjacent to one or more sectors maintained at pressure varying in the range 1-1.5 absolute bar.

(17) The sectors can be in the press filter type configuration, in the case of membranes in the form of sheets, or in the tube bundle type exchanger configuration, in the case of membranes in the form of hollow fibres.

(18) The carrier gas saturated with vapour distillate is cooled by heat exchange (6) with a fluid which is at an initial temperature which varies in the range from 0 C. to 25 C. (9) so as to obtain a distillate in liquid phase (8).

(19) For this purpose, heat exchangers external to the MD system or internal to the same system can be used, for example selected from coils, plates, or tube bundle exchangers.

(20) The saturated gas of vapour distillate can also be cooled by direct contact with a fluid at an initial temperature which varies in the range 0-25 C. Said fluid can be selected from water, nitrogen, oxygen, carbon dioxide, pure or mixed methane.

(21) The distillate in liquid phase, enriched by water, can be sent to subsequent treatments until reaching a quality suitable for reuse or discharge into the environment.

(22) Said treatments can include a further membrane distillation operation.

(23) Furthermore, the process described and claimed can comprise a stage in which the concentrate (7) (enriched by the high-boiling chemical compounds including methyldietylamine (MDEA) is sent to pyrolysis or disposal.

(24) Furthermore, the gas enriched by non-condensable (9) can be sent to subsequent treatments until reaching a quality suitable for reuse or discharge into the environment.

(25) The technical solution object of the present patent application allows the concentration by dehydration of the amine water under milder conditions than those described in the prior art, lower temperatures and atmospheric pressure instead of the vacuum, through MD.

(26) Failure to use the vacuum unexpectedly allows to maximize its effectiveness.

(27) In the present patent application, hydrophobic and porous membranes comprising inorganic or organic polymers and copolymers or combinations thereof, preferably organic polymers and copolymers or combinations thereof, more preferably organic polymers containing halogens and their copolymers, or combinations thereof, can be used; or organic polymers not containing halogens and their copolymers or combinations thereof can be used. still more preferably the hydrophobic and porous membranes can be organic polymers containing fluorine and their copolymers, or combinations thereof; or organic polymers not containing fluorine and their copolymers, or combinations thereof. still more preferably said membranes can be selected from oxides, sulfides, zeolites, metal-organic materials, such as for example metal-organic frameworks; carbonaceous materials, such as for example graphene; polysilanes and their copolymers; polysiloxanes and their copolymers; polysulfones and their copolymers; polyacrylates and their copolymers; polycarbonates and their copolymers; proteins, polyamides and their copolymers; polyurethanes and their copolymers; polyketones and their copolymers; polyesters and their copolymers; polysaccharides, polyethers and their copolymers; polyaromatics and their copolymers; polyolefins and their copolymers; or combinations thereof. Polyolefins containing fluorine, polyolefins not containing fluorine, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, or combinations thereof are preferred; among them the most preferred is polypropylene.

(28) The chemical compounds listed above can be used in the preparation of the membranes as single chemical compounds or the combinations thereof, that is, as mixtures of the same or as successive layers of the same.

(29) Polyolefins not containing fluorine are less expensive and less problematic from an environmental point of view (both during production and disposal) than those containing fluorine used in similar processes (E. Corsini et al., Perfluorinated Compounds Emerging Persistent Organic Pollutants with Potential Immunotoxicity, Toxicology Letters 230 (2) 2014 263-270).

(30) The membranes used maintain their performance unaltered for at least 300 hours of service without being affected by the chemical aggressiveness of the amine water.

(31) Preferably the process described and claimed in the present patent application allows to concentrate amine water which further comprises sulfur sulfide whose concentration varies in the range between 1000 mg/L and 10000 mg/L, preferably in the range between 2000 mg/L and 10000 mg/L, more preferably in the range between 3000 mg/L and 10000 mg/L, still more preferably equal to 3950 mg/L.

(32) Preferably, the process described and claimed in the present patent application allows to concentrate amine water further characterized by a chemical oxygen demand which varies in the range between 100000 mg/L and 1000000 mg/L, more preferably between 200000 mg/L and 1000000 mg/L, still more preferably between 300000 mg/L and 1000000 mg/L, still more preferably equal to 711000 mg/L.

(33) Preferably, the process described and claimed in the present patent application allows to concentrate amine water further characterized by an electrical conductivity which varies in the range between 500 S/cm and 150000 S/cm, more preferably that varies in the range between 5000 S/cm and 150000 S/cm, still more preferably between 10000 S/cm and 150000 S/cm, still more preferably it is 10180 S/cm.

(34) Preferably the process described and claimed in the present patent application allows to concentrate amine water which further comprises a boron concentration which varies in the range between 10 mg/L and 1000 mg/L, preferably in the range between 50 mg/L and 1000 mg/L, more preferably in the range between 100 mg/L and 1000 mg/L, more preferably equal to 358 mg/L.

(35) In a preferred form, the process described and claimed in the present patent application allows to concentrate amine water comprising nitrogen-containing chemical compounds, characterized in that the concentration of total nitrogen can vary in the range between 10000 mg/L and 100000 mg/L, preferably between 20000 mg/L and 100000 mg/L, more preferably between 30000 mg/L and 100000 mg/L; further comprising sulfur sulfide whose concentration varies in the range between 1000 mg/L and 10000 mg/L, preferably in the range between 2000 mg/L and 10000 mg/L, more preferably in the range between 3000 mg/L and 10000 mg/L.

(36) In a preferred form, the process described and claimed in the present patent application allows to concentrate amine water comprising nitrogen-containing chemical compounds, characterized in that the concentration of total nitrogen can vary in the range between 10000 mg/L and 100000 mg/L, preferably between 20000 mg/L and 100000 mg/L, more preferably between 30000 mg/L and 100000 mg/L; further comprising sulfur sulfide whose concentration varies in the range between 1000 mg/L and 10000 mg/L, preferably in the range between 2000 mg/L and 10000 mg/L, more preferably in the range between 3000 mg/L and 10000 mg/L; said amine water also having a chemical oxygen demand which varies in the range between 100000 mg/L and 1000000 mg/L, more preferably between 200000 mg/L and 1000000 mg/L, still more preferably between 300000 mg/L and 1000000.

(37) In a preferred form, the process described and claimed in the present patent application allows to concentrate amine water comprising nitrogen-containing chemical compounds, characterized in that the concentration of total nitrogen can vary in the range between 10000 mg/L and 100000 mg/L, preferably between 20000 mg/L and 100000 mg/L, more preferably between 30000 mg/L and 100000 mg/L; further comprising sulfur sulfide whose concentration varies in the range between 1000 mg/L and 10000 mg/L, preferably in the range between 2000 mg/L and 10000 mg/L, more preferably in the range between 3000 mg/L and 10000 mg/L; said amine water also having a chemical oxygen demand that varies in the range between 100000 mg/L and 1000000 mg/L, more preferably between 200000 mg/L and 1000000 mg/L, still more preferably between 300000 mg/L and 1000000; said amine water also having electrical conductivity which varies in the range between 500 S/cm and 150000 S/cm, more preferably which varies in the range between 5000 S/cm and 150000 S/cm, still more preferably between 10000 S/cm and 150000 S/cm.

(38) In a preferred form, the process described and claimed in the present patent application allows to concentrate amine water comprising nitrogen-containing chemical compounds, characterized in that the concentration of total nitrogen can vary in the range between 10000 mg/L and 100000 mg/L, preferably between 20000 mg/L and 100000 mg/L, more preferably between 30000 mg/L and 100000 mg/L; further comprising sulfur sulfide whose concentration varies in the range between 1000 mg/L and 10000 mg/L, preferably in the range between 2000 mg/L and 10000 mg/L, more preferably in the range between 3000 mg/L and 10000 mg/L; said amine water also characterized by a chemical oxygen demand which varies in the range between 100000 mg/L and 1000000 mg/L, more preferably between 200000 mg/L and 1000000 mg/L, still more preferably between 300000 mg/L and 1000000; said amine water also characterized by an electrical conductivity that varies in the range between 500 S/cm and 150000 S/cm, more preferably that varies in the range between 5000 S/cm and 150000 S/cm, still more preferably between 10000 S/cm and 150000 S/cm; said amine water which further comprises a boron concentration which varies in the range between 10 mg/L and 1000 mg/L, preferably in the range between 50 mg/L and 1000 mg/L, more preferably in the range between 100 mg/L and 1000 mg/L.

(39) In all the preferred forms according to the present patent application, the nitrogen concentration, the sulfur sulfide, the chemical oxygen demand, the electrical conductivity and the boron concentration can vary in the preferred ranges previously listed.

(40) The data shown in the examples show that the quality of the distillate in liquid phase obtainable through MD conducted by applying vacuum in the distillate sector is lower than that obtainable through MD conducted by maintaining the distillate sector at atmospheric pressure.

(41) The MD conducted by maintaining the distillate sector at atmospheric pressure is therefore the most effective system for concentrating amine water.

(42) Some application examples of the present disclosure are now described, which have a purely descriptive and non-limiting purpose and which represent preferred embodiments.

EXAMPLES

(43) The MD tests were carried out by means of a system equipped with a tubular module made of AISI 316 L stainless steel with an internal diameter of 25 mm and a length of 300 mm. A beam of polypropylene capillary membranes AccurelS S6/2 membrane, with an internal diameter of 1.8 mm, was housed inside the module; wall thickness of 0.45 mm; total area of 131 cm.sup.2; pore diameter of 0.2 m; contact angle with water of 120 measured with a Biolin Scientific Attension T200 angle meter.

(44) It was operated by completely recycling the distillate and the concentrate to the 2 L feed tank. The latter was placed on a DLab MS-H280-Pro stirring-heating magnetic plate with integrated temperature probe to maintain the system temperature at the value defined for each test.

(45) The feed was sent to the module by means of a Plastomec P051 polypropylene magnetic drive pump in order to have a linear speed tangential to the external surface of the capillary membranes of 2.6 m/s. The system has been prepared so that the lumen of each capillary membrane can be maintained in the flow of carrier gas or alternatively under vacuum.

(46) The distillate in vapour phase was condensed by means of a straight barrel liebig glass refrigerant maintained at 0 C. by means of a Lauda RC6 thermo-cryostat with external circulation of the mixture of water and Petronas ParafluBlu 1/1 v./v. The distillate in liquid phase was collected in a glass flask connected to the refrigerant. Amine water containing MDEA having the following chemical-physical characteristics was used as a feed: pH of 12.7 measured by the Eutech PH510 instrument with Hanna HI1230 probe; electrical conductivity (EC) of 10180 S/cm measured by the Hanna EC215 instrument with Hanna H176303 probe; chemical oxygen demand (COD) of 711000 mg/L; total nitrogen content (N) of 66000 mg/L; sulfur sulfide content (S.sup.2) of 3950 mg/L; boron content (B) of 358 mg/L.

(47) The measurements of COD, N, S, B, respectively, were carried out with a test tube kit using the Merck Spectroquant Pharo 300 ultraviolet-visible spectrophotometer equipped with the Merck Spectroquant TR320 reactor.

(48) Boron was introduced as boric acid (Sigma Aldrich ACS-Grade, purity greater than 99.5% weight) as a tracer. Measurements of the distillate flow rate were carried out in liquid phase every 15 min from which it was possible to trace the flow and 50 mL samples of the same to measure its chemical-physical properties, in this text also generically indicated with the term G.

(49) The respective retentions R have been calculated from the chemical-physical characteristics of the feed and the distillate according to the equation:
R(G) %=[(G) Feed(G) Distillate]*100/(G) Feed.

Example 1: Test at 50 C. (Distillate Sector at Atmospheric Pressure)

(50) The lumen of each capillary membrane was maintained in the carrier air flow (Air Liquide Alphagaz 1, purity greater than 99.999%) in order to have a linear speed of 4 m/s. An average distillate flow of 0.75 L/m.sup.2*h was obtained. Table 1 shows the pH of the distillate and the retentions referring to the chemical-physical characteristics that indicate contamination after different service times (N.D. if not determined). The data shown show the membrane stability for at least 300 h of service.

(51) TABLE-US-00001 TABLE 1 t pH R (EC) R (COD) R (N) R (S) R (B) [h] [] [%] [%] [%] [%] [%] 50 8.5 99.48 99.97 99.97 N.D. 99.98 150 8.7 99.45 99.96 99.97 99.88 99.97 300 9.4 99.55 99.95 99.96 99.95 99.98

Example 2: Test at 70 C. (Distillate Sector at Atmospheric Pressure)

(52) The MD test described in Example 1 was repeated by operating at 70 C.

(53) An average distillate flow of 2.20 L/m.sup.2*h was obtained. Table 2 shows the pH of the distillate and the retentions referring to the chemical-physical characteristics that indicate contamination after different service times. The data shown show the membrane stability for at least 300 h of service.

(54) TABLE-US-00002 TABLE 2 t pH R (EC) R (COD) R (N) R (S) R (B) [h] [] [%] [%] [%] [%] [%] 100 8.5 99.50 99.90 99.96 99.90 99.95 300 9.4 99.60 99.93 99.96 99.95 99.95

Comparative Example 1: Test at 50 C. (Distillate Sector Under Vacuum)

(55) The lumen of each capillary membrane was maintained under a 20-mbar vacuum by connecting a water jet pump to a slot on the line downstream of the condenser. An average distillate flow of 5.0 L/m.sup.2*h was obtained. Table 3 shows the pH of the distillate and the retentions referring to the chemical-physical characteristics that indicate contamination (N.D. if not determined). The data reported show that the MD conducted by maintaining the distillate sector at atmospheric pressure is the most effective system for concentrating amine water, allowing greater retentions referring to the chemical-physical characteristics indicating contamination and therefore the production of best quality water.

(56) This cannot be deduced from the teachings found in the state of the art.

(57) TABLE-US-00003 TABLE 3 t pH R (EC) R (COD) R (N) R (S) R (B) [h] [] [%] [%] [%] [%] [%] 50 8.3 95.60 96.10 96.11 N.D. 96.13 200 8.3 95.50 95.80 96.01 96.00 96.10