WO2002006161A2

WO2002006161A2 - Recovery of glycol from waste water

Info

Publication number: WO2002006161A2
Application number: PCT/CA2001/001037
Authority: WO
Inventors: Glenn Murray Vanderlinden; Douglas Cornelius Vanderlinden
Original assignee: Glenn Murray Vanderlinden; Douglas Cornelius Vanderlinden
Priority date: 2000-07-17
Filing date: 2001-07-17
Publication date: 2002-01-24
Also published as: AU2001275620A1; WO2002006161A3

Abstract

A method for the treatment of a solution of glycol and water e.g. automotive anti-freeze, aircraft de-icing fluid, industrial HVAC coolants and heat transfer fluids, to effect separation of glycol therefrom. The method comprises feeding air into a chamber (2) and spraying a solution of glycol and water into the chamber (2). A solution enriched in glycol is obtained and air is discharged. Steps may be taken to remove contaminants from the solution prior to the teatment.

Description

RECOVERY OF GLYCOL FROM WASTE WATER

Field of the Invention The present invention relates to a method, apparatus and system for the recovery of glycol from waste water, and in particular for the recovery of glycol in a reusable form from waste water that is in the form of spent de-icing fluid at an airport or from an industrial location.

Background to the Invention

A large portion of North American experiences adverse weather conditions during the winter months. These weather conditions may be in the form of freezing rain or snow, including snowstorms and blizzards. With the increasing amount of air travel, there is pressure on airlines and airport authorities to fly aircraft during adverse weather conditions. They must do so in a safe manner, especially during aircraft takeoffs and landings under the adverse weather conditions. While airport authorities can take steps for snow clearance and removal of ice on runways, it is also necessary to remove snow and ice from the aircraft. The snow or ice that can accumulate on an aircraft body and wings adds weight and and distorts the aircraft wing surface profile, which can have severe effects on the ability of the aircraft to lift off of the runway during takeoff.

To minimize snow accumulation and create a clean wing surface, the aircraft is sprayed with de-icing fluids. The de-icing fluid is typically a glycol formulation composed of ethylene glycol, diethylene glycol and/or propylene glycol, or similar materials, and may contain additional ingredients. It is understood that such fluids may be formulated to effect removal of snow or ice already accumulated on the aircraft and/or to prevent further accumulation of snow or ice. For instance, some de-icing formulations are intended to remove snow and ice immediately prior to takeoff, and may not be very effective if the aircraft is required to stay on the ground for an extended period of time. Other de-icing formulations are intended to remain on the aircraft for a period of time. The latter de-icing fluids are more likely to remain on the aircraft during taxiing and even takeoff, with the result that the fluids are deposited on taxiways and takeoff runways.

Apart from immediate hazards in aircraft taxiing and particularly takeoff and landing due to accumulation of de-icing fluids on runway surfaces, collection of spent de-icing fluid at an airport is necessary due to the high biological oxygen demand that such fluids place upon water collection systems located around the airport. Moreover, glycol-contaminated water bodies may create noxious odours as the glycol components biodegrade. Consequently, there are increasing environmental legislative requirements for removal of de-icing fluids from airport stormwater systems.

The recovery of spent de-icing fluid is complicated by the weather conditions that typically exist at the time of recovery e.g. freezing temperatures and combinations of snow and/or ice. Moreover, various de- icing formulations tend to cling to airport surfaces, making recovery difficult. This is particularly the case with formulations that are intended to prevent accumulation of snow and ice for a period of time.

Two methods are used for collection of spent de-icing fluids. One system is known as an active or mobile collection system, using truck or trailer-mounted collection units that vacuum the spent de-icing fluids from the airport sur aces. Examples of active systems for removing de-icing fluid are disclosed in U.S. Patents 5,561 ,921 and 5,630,286.

The other method is known as a passive collection system, where the fluid is permitted to flow or is pumped into large holding tanks. Passive collection systems in use can store up to in excess of a million gallons of stormwater contaminated with spent de-icing fluid. This method of collection results in maximum dilution of fluids, and usually creates a mixture of fluids that is too weak to recycle, but yet is too high in biological oxygen demand for discharge to stormwater systems and/or to be subjected to biodegradation in existing sewage treatment systems.

Aqueous solutions containing glycol may also be obtained from a variety of other sources. For instance, the aqueous solution containing glycol may be obtained from industrial locations, examples of which include oilfields and automotive businesses.

Once spent de-icing fluids or other types of waste water containing glycol is collected, it is useful to recover and reuse the glycol contained therein. Methods for the recovery of glycol from waster water solutions have been described. For example, U.S. Patent 5,194,159 discloses a process whereby operative fluids containing lower glycol are contacted with semi- permeable membranes under reverse osmosis conditions to permeate lower glycol to provide a reclaimed lower glycol product. U.S. Patent 5,411 ,668 discloses a process for the reclamation of used glycolic aircraft deicing compositions which comprises conventional ultrafiltration of the deicing fluid followed by treatment with ion exchangers and distillation. U.S. Patent 6,023,003 discloses a process for recovering glycol from glycol/brine streams which comprises repeated high temperature evaporation cycles to provide a concentrated glycol liquid. U.S. Patent 6,133,489 discloses a process for obtaining glycols with low aldehyde content from a glycol-containing mixture, which comprises treating the apparatus and the glycol-containing mixture with phosphorous acid or a salt thereof and subsequently recovering the glycol(s) by distillation.

While the aforementioned methods for glycol recovery are generally useful, it is desirable to provide a more simple, cost effective and efficient process for the recovery of glycol from spent de-icing fluids as well as other types of industrial fluids.

Summary of the Invention

The present invention is directed to an apparatus and methods for the treatment and recovery of glycol from aqueous solutions, especially aqueous waste solutions, from a variety of sources. According to an aspect of the present invention is a method for separating glycol from a waste water solution of glycol and water, the method comprising directing an atomized mist of waste water into a flow of air to create a turbulent mixture of waste water and air, directing said turbulent mixture through a set of orifices and panels, wherein such mixing results in the evaporation of water and a concentration of collectable glycol. Accordingly, one aspect of the present invention provides a method for the treatment of a solution of glycol and water to effect separation of glycol therefrom, comprising:

(a) feeding air into a chamber, said air having a relative humidity of less than 100%; (b) spraying a first solution of glycol and water into said chamber of air;

(c) collecting a second solution of glycol in said chamber, said second solution having a higher concentration of glycol than said first solution; and (d) discharging air from said chamber, said air so discharged having an increased relative humidity.

A further aspect of the present invention provides a method for the separation of glycol from an aqueous waste stream of glycol and one or more of hydrocarbons, solids, methanol, salts and other contaminants therein, the method comprising subjecting the stream to one or more of the following steps:

(a) subjecting the waste stream to treatment to effect separation of hydrocarbons and solids, said hydrocarbons being removed as a first light fraction and said solids separating as a heavy fraction; (b) subjecting the waste stream to non-thermal fractionation to separate methanol and other volatile matter therefrom; and

(c) subjecting the treated stream so obtained to effect separation of glycol therefrom, said treated stream being essentially free of hydrocarbons, solids, methanol and salts, said separation comprising the steps of: (i) feeding air into a chamber, said air having a relative humidity of less than 100%; (ii) spraying first solution of glycol and water into said chamber of air;

(iii) collecting a second solution of glycol in said chamber, said second solution having a higher concentration of glycol than said first solution; and

(iv) discharging air from said chamber, said air so discharged having an increased relative humidity.

Another aspect of the invention provides a method for the treatment of an aqueous solution of glycol to effect a concentration thereof, comprising: (a) feeding air into a chamber, said air having a relative humidity of less than 100%;

(b) spraying a first aqueous solution into said chamber of air;

(c) collecting a second aqueous solution in said chamber, said second solution having a reduced water content than said first solution; and (d) discharging air from said chamber, said air so discharged having an increased relative humidity.

According to a further aspect of the present invention is an apparatus for concentrating glycol from waste water sources containing water and glycol by evaporation of water, said apparatus comprising; - a housing having a base portion and defining an enclosed chamber;

- at least one spray nozzle for providing a flow of an atomized mist of waste water in said housing;

- particle separator means upstream of said spray nozzle; and

- a fan suction means adjacent and operatively connected to said housing for providing a flow of air countercurrent to the flow of said atomized mist of waste water such that said atomized mist of waste water is drawn towards and contacts with said particle separator means, wherein said water evaporates and said glycol collects and falls downwards from said particle separator means. According to a further aspect of the present invention is a system for concentrating glycol from waste water sources containing water and glycol by evaporation of water, said apparatus comprising;

- a waste-water filtration unit for pretreating waste-water;

- a housing having a base portion and defining an enclosed chamber, said housing being operatively connected to said filtration unit for receiving pretreated waste-water;

- particle separator means upstream of said spray nozzle; and

- a fan suction means adjacent and operatively connected to said housing for providing a flow of air countercurrent to the flow of said atomized mist of waste water such that said atomized mist of waste water is drawn towards and contacts with said particle separator means, wherein said water evaporates and said glycol is concentrated and collects and falls downwards from said particle separator means. The system may further comprise a waste-water filtration unit operatively connected to the housing to receive concentrated glycol for further filtering and cleaning for removal of certain contaminants.

Brief Description of the Drawings The present invention is illustrated by the embodiments shown in the drawings, in which:

Figure 1 is a schematic representation of a top view of a spray chamber in accordance with a first embodiment of the present invention; Figure 2 is a schematic representation of a side view of the spray chamber of Figure. 1 ;

Figure 3 is a schematic representation of a top view of a spray chamber in accordance with a second embodiment of the present invention;

Figure 4 is a schematic representation of a side view of the spray chamber of Figure 3; and Figure 5 is a schematic representation of the system of the present invention. Detailed Description of the Invention

A first preferred embodiment of an apparatus in accordance with the present invention is shown in Figure 1. The apparatus has housing 2 with a base 1. Housing 2 is an enclosed chamber in which are located spray nozzles 8, coarse particle separator panel 3 and fine particle separator panel 4. Suction fan 5 is located outside of housing 2, opposite to the air intake 10. The direction of the flow of air through housing 2 is indicated by arrow. Typical air flow volumes range from about 10,000 cfm to about 50,000 cfm. However, higher air volumes can be used if the chamber 2 and pump 7 are increased proportionately.

Figure 2 shows a side view of the apparatus showing the fan 5 and air pre-heater 12 as external to chamber 2a. The chamber 2a is equipped with an air pre-heater 12 and fluid pre-heater 1 associated therewith. Fluid spray nozzles 8 are mounted on a quick release spray bar which removes through air intake opening 10. The direction of the spray from spray nozzle 8 is counter-current to the flow of air through the apparatus, which is the preferred direction of the spray. The fluid spray system operates at pressures between about 150 and about 350 psi to create water droplets ranging in size from about 10 to about 300 microns. Water droplet size is controlled through a pressure control valve that can operate manually or automatically.

Control panel 15 contains electrical components, breakers, fusing, motor starters, relays and programmable logic controls to operate the unit in an unattended manner. Control panel 15 also contains an automated concentration sensor which continuously monitors fluid concentration levels and automatically pumps off the contained fluid when it reaches target concentration. Control panel 15 also contains low and high level switches and an automated feed valve to control fluid levels and periodically replace fluid which has been evaporated.

Chamber 2a is shown as having vertical particle separators 3 and 4 which are used in the directing of air flow through chamber 2a and through orifice 13 of panel 3 and orifice 14 of panel 4. Spray nozzle 8 is located immediately in front of orifice 13 of panel 3. The humidified air and sprayed mixture passes through chamber 2a and contacts panel 3 which is staggered rows of vertically arranged angles. The coarse water particles contact the angles and are pushed to the floor of chamber 2a in an area shielded from vacuum by a floor plate, creating an area of low pressure. Resultant foaming is minimized by the spraying effect in chamber 2. The humidified air passes through orifice 13 where it enters panel 4. Panel 4 contains two rows of vertically arranged S shaped plates, each containing a capture vane or fluid hook in the S .plate where the air and fine fluid particles begin to turn. The heavier particles are forced against the inner hook by centrifugal force, allowing the lighter, humidified air to exit the panel through orifice 14. A second row of S shaped plates repeats the process. Effective demisting in these panels removes most of (i.e. about 99.9%) of all fluid particles greater than 20 micron nominal sizing. Fluid removed by panel 4 is directed through a collection floor back to the fluid sump 16 to spray again.

In preferred embodiments of the invention, the size of orifice 13 and 14 are adjustable, with respect to one or both of panels 3 and 4. Adjustment would permit optimization of the method with respect to particular solutions being subjected to the method, atmospheric conditions or for other reasons.

In use, air is drawn into chamber 2a by fan 5. The air may be preheated at air pre-heater 12. It is understood that use of air pre-heater 12 is optional, and such use would depend on, for instance, the temperature of the ambient air, the relative humidity of that air and the solution being treated.

An aqueous glycol solution is fed to spray nozzle 8 and sprayed counter-current to the flow of air through chamber 2a. It is preferred that liquid passing from spray nozzle 8 be atomized. It is believed to be important to control the degree of atomization relative to the vapour pressure of the material e.g. glycol, from which water is being stripped. The counter current spray from spray nozzle 8 and the flow of air from fan 5 cause a turbulent mix of atomized liquid and air within chamber 2a. Any of the spray that condenses is collected at the bottom of chamber 2a. It is understood that the spraying of the aqueous glycol solution from spray nozzle 8 is conducted so as to effect atomization of the liquid. There are a number of variables to be considered in order to effect atomization, including water pressure, water volume, volume of air fed to the nozzle, air flow in the chamber, ambient air temperature, ambient air humidity and the like.

The mixture of air and atomized liquid that is obtained in chamber 2 is drawn through panel 3 and 4 where coarse particle separation and demisting takes place. Evaporation of water from the atomized liquid commences when the liquid passes from spray nozzle 8, and continues as the mixture of air and atomized liquid passes through orifices 13 and 14, and beyond. The air is then discharged from housing 2 through fan 5 and exhaust stack 6. It is preferred that the air be discharged vertically to further reduce the likelihood of entrained liquid being discharged with the air. In addition, the air that is discharged should be directed away from the intake to fan 5, so that discharged humid air is not recycled.

Water evaporates from the atomized droplets of liquid in the air, but the low vapour pressure of glycol under the conditions of operation minimizes contamination of the air with glycol. Panels 3 and 4 and flow path remove entrained droplets of liquid in the air. The liquid obtained, which is an aqueous solution enriched in glycol or even an essentially pure glycol, is collected for further processing, recycle, for sale or other use. It should be understood that multiple passes of an aqueous glycol solution through the nozzle may be required in order to obtain glycol substantially free of water. Moreover, it may be acceptable for many uses of the glycol to effect a concentration of glycol in the aqueous solution, rather than substantially complete removal of water. The air that enters chamber 2a has a relative humidity that is below

100% RH, although air with a relative humidity of 100% RH can be heated to reduce the relative humidity and effect evaporation of water. It is understood that the method would tend to be optimized with lower humidities, but reduction in humidity may not be economical. Nonetheless, humidities lower than 60%, lower than 50% and most preferably lower than 40% are preferred. If necessary, the air may be heated in pre-heater 12, or the fluid may be preheated 11 in order to effect a lowering of the relative humidity. The air discharged from housing 2 will have a higher relative humidity.

A further embodiment of the invention is shown in Figure 3. In this embodiment the apparatus 100 has housing 102 with a base 103. Housing 102 encloses chamber 104 in which is located spray nozzle 107. Fan 105 is located outside of chamber 104, and has air pre-heater 106 associated therewith. It is preferred that air pre-heater 106 be located between chamber 104 and fan 105, to reduce the exposure of the fan motor to heated air. Chamber 104 terminates at panel 108. Housing 102 also has baffle 109, panel 110 and panel 111. This embodiment of the apparatus is more clearly seen in Figure 4. Spray nozzle 107 is shown as being located immediately in front and adjacent to panel 108. The direction of the flow of air through housing 102 is indicated by arrow 112. The direction of the spray from spray nozzle 107 is counter-current to the flow of air through the apparatus, as is indicated by the arrow 113, which is the preferred direction of the spray.

Figure 4 shows a plan view of the apparatus of Figure 3. Fan 105 and air pre-heater 106 are shown as external to chamber 104. Chamber 104 is shown as having baffles 114, which are used in the directing of air flow 112 through chamber 104 and through orifice 117 of panel 108. Spray nozzle 107 is located immediately in front of orifice 117 of panel 108. Baffle 109 is located immediately down stream of orifice 117 so that the air mixture passing out of chamber 104 through orifice 117 contacts baffle 109. Baffle 109 has centrally-located cone 118 which diverts the flow of the air mixture through 90°. Thus, spray nozzle 107, orifice 117 and cone 118 are aligned. The surface of baffle 109 is preferably covered with a chevron or other pattern of grooves that are shaped to cause flow of liquid on the surface of baffle 109 away from the direct path of the flow of the air mixture and downwards. Such a pattern effects separation and removal of liquid in the air mixture passing through orifice 117.

Baffle 109 is spaced apart from the opposed walls 116A and 116B of housing 102. Panel 110 has orifice 115 therein that is also aligned with orifice 117 and cone 118. The air mixture passing around baffle 109 undergoes a 180° change in direction as it passes around the end of baffle 109 and is directed through orifice 115. It is preferred that gap 119 between baffle 109 and housing 2 be of smaller cross-section than the spacing between baffle 109 and panel 110, so as to cause changes in the velocity of the air mixture. Panel 111 has orifices therein (not shown) for passage of air.

In preferred embodiments of this embodiment of the invention, the position of baffle 109 is adjustable, with respect to one or both of panels 108 and 110. Adjustment of baffle 109 would permit optimization of the method with respect to particular solutions being subjected to the method, atmospheric conditions or for other reasons.

In use, air is forced into chamber 104 by fan 105. The air may be preheated at air pre-heater 106. It is understood that use of air pre-heater 106 is optional, and such use would depend on, for instance, the temperature of the ambient air, the relative humidity of that air and the solution being treated. An aqueous glycol solution is fed to spray nozzle 107 and sprayed counter-current to the flow of air through chamber 102. It is preferred that liquid passing from spray nozzle 107 be atomized. It is believed to be important to control the degree of atomization relative to the vapour pressure of the material e.g. glycol, from which water is being stripped. The counter current spray from spray nozzle 107 and the flow of air from fan 105 cause a turbulent mix of atomized liquid and air within chamber 104. Any of the spray that condenses is collected at the bottom of chamber 104. It is understood that the spraying of the aqueous glycol solution from spray nozzle 107 is conducted so as to effect atomization of the liquid. There are a number of variables to be considered in order to effect atomization, including water pressure, water volume, volume of air fed to the nozzle, air flow in the chamber and the like.

The mixture of air and atomized liquid that is obtained in chamber 104 is directed by baffles 114 through orifice 117 and onto panel 118. Use of baffles 114 is optional. The mixture of air and atomized liquid impacts on baffle 109, and especially on cone 118 i.e. a rapid flow of the mixture is effected by fan 105. Evaporation of water from the atomized liquid commences when the liquid passes from spray nozzle 107, and continues as the mixture of air and atomized liquid passes through orifice 117 and contacts baffle 109, and beyond. However, baffle 109 is primarily intended to effect separation of liquid from the air such that air passing from the apparatus may be free of entrained liquid. The initial separation is effected by contact with baffle 109, including cone 118. Liquid collects on the surface of baffle 109 and cone 118. Such liquid tends to flow away from cone 118 by virtue of the flow of air mixture impacting on cone 118. This may be facilitated by the use of chevrons or other grooves on the surface of baffle 109 and cone 118. Such grooves preferably direct the liquid away from cone 118 and downwards, to assist the effects of gravity in directing liquid to the bottom of housing 102. Such liquid may be caused to flow into chamber 104 for removal or recycle. The flow of air and remaining atomized liquid is then forced around baffle 109, and then through gap 119 between baffle 109 and walls 116A and 116B of housing 102. If gap 119 causes constriction in the flow of air and atomized liquid, followed by expansion, the consequent changes in velocity and pressure effect further separation of atomized liquid from the air. The air mixture then flows through orifice 115 of panel 110 and is passed through panel 111. The air is then discharged from housing 102. It is preferred that the air be discharged vertically to further reduce the likelihood of entrained liquid being discharged with the air. In addition, the air that is discharged should be directed away from the intake to fan 105, so that discharged humid air is not recycled.

Water evaporates from the atomized droplets of liquid in the air, but the low vapour pressure of glycol under the conditions of operation minimizes contamination of the air with glycol. The panels and flow path remove entrained droplets of liquid in the air. The liquid obtained, which is an aqueous solution enriched in glycol or even an essentially pure glycol, is collected for further processing, recycle, for sale or other use. It should be understood that multiple passes of an aqueous glycol solution through the nozzle may be required in order to obtain glycol substantially free of water. Moreover, it may be acceptable for many uses of the glycol to effect a concentration of glycol in the aqueous solution, rather than substantially complete removal of water.

The air that enters chamber 104 is preferred to have a relative humidity that is below 100% RH, although air with a relative humidity of 100% RH can be heated to reduce the relative humidity and effect evaporation of water. It is understood that the method would tend to be optimized with lower humidities, but reduction in humidity may not be economical. Nonetheless, humidities lower than 60%, lower than 50% and most preferably lower than 40% are preferred. If necessary, the air may be heated in pre-heater 106 in order to effect a lowering of the relative humidity. The air discharged from housing 102 will have a higher relative humidity.

The aqueous solution of glycol and water may be obtained from a number of sources but common sources are de-icing fluid obtained from an airport, particularly an airport runway and certain industrial fluids. As used herein, an airport runway is understood to include the runways used for takeoff and landing, the runways used for taxiing of aircraft, the apron where the aircraft is loaded and any central de-icing pad at an airport. It is the apron or central de-icing pad where the aircraft is most commonly sprayed with de- icing fluids. Other sources of glycol and water solutions include automotive anti-freeze, industrial HVAC coolants and heat transfer fluids. Such fluids would typically be contaminated with dirt and other solid matter. In addition, the fluid may be contaminated with hydrocarbons e.g. fuel, by methanol in waste water from oil and gas sources, by benzene in waste water in automotive antifreeze, by components in de-icing formulations and by salts used in the cleaning of airport runways or other areas from ice and snow. Other sources may have different contaminants. Depending on the particular source of the aqueous solution of glycol, a number of pre-treatment steps to remove contaminants from the solution may be required in order to obtain an aqueous solution that is suitable for feeding to the embodiments of the apparatus spray units described above. For instance, the waste water solution may be filtered and/or stored in a holding tank to remove solid matter. Such solid matter could plug nozzles used in the separation step and/or cause other damage to apparatus or processing problems. In addition, hydrocarbons should be separated and volatile organic contaminants should be removed. Any such volatile organic contaminants, particularly contaminants that are more volatile than water, would tend to be discharged from the apparatus with air, and hence cause pollution and/or contravene governmental regulations for gaseous streams discharged into the atmosphere.

In particular, it may be necessary to subject the waste water solution of glycol to a filtration system to remove solid matter. The feed liquid obtained may then be treated with surfactants or other materials in a pre-treatment tank to cause hydrocarbons and further solid material to separate from the liquid. Hydrocarbons are typically floated to the surface of the feed liquid, where they may be skimmed off and sent to a separate storage tank. Such hydrocarbons may be treated for disposal, or blended with other solutions for further use. The solids in the liquid feed tend to settle to the bottom of the pre-treatment tank, where they accumulate and may be removed from time to time. Such solids would then normally be treated so that they would meet the appropriate governmental regulations for disposal of such a product. The feed liquid that is obtained from the pre-treatment step is substantially free of emulsified hydrocarbons and suspended solids. In embodiments, the feed liquid may then be treated for removal of methanol, benzene or other volatile organic contaminants. In particular, contaminants that have a vapour pressure such that the contaminant would separate in the method as a volatile material, and hence be discharged with air, should be removed to reduce pollution and meet environmental regulations. One such method for the treatment for removal of methanol involves pumping the feed stream through a non-thermal fractionation unit that is operated at a vapour pressure that is suitable to effect release of methanol from the feed liquid. Such a non-thermal fractionation unit is operated at ambient temperature. The methanol/water vapour mixture that is separated may be suitable for re- use e.g. in a de-icing fluid or coolant, or may be disposed of.

The resultant aqueous solution of glycol may then be suitable for separation of glycol as described above. It should also be understood that the methods of the present invention may be regarded as methods of removal of water from the aqueous solution, as discussed herein, which results in a more concentrated solution i.e. a solution enriched in glycol. While the solution may be subjected to other purification steps, including those described herein, prior to the separation or concentration of glycol, it is generally preferable for economic reasons to effect removal of water and subsequently treat the solution for further purification. It is also understood that a partial concentration of the glycol may be effect, then additional purification steps carried out followed by further concentration of the glycol.

The mixture of glycol or glycol and water that is obtained from the separation step may be subjected to a chemical flocculation step, which effects further removal of suspended solids, emulsified oils and salt-based components that may be in the mixture. In addition, various metals may be chelated and removed especially to prevent corrosion or other damage to apparatus used in the process or in subsequent end-uses. The resultant treated material tends be low in turbidity, and may be effectively treated in membrane filtration steps, or by other means. If levels of metals and chlorides remain at an unacceptable level, the solution may then be subjected to a micro-filtration or nano-filtration using a polymetric or ceramic membrane filtration unit (i.e., Duraclean¹⁰ or DuraFlow¹⁰ units). The membrane filtration unit may be washed with acid and/or base solutions for cleaning.

The resultant solution may be subjected to further treatment steps e.g. use of an ion exchange medium to remove any remaining metals and/or chlorides.

Combinations of the above steps may be used to reduce the amounts of metals and chlorides to levels at which such contaminants are effectively not detectable. The method may be operated so that the air that is discharged has minimal contamination by glycol. In addition, the method may be operated, especially with recycle or multi-pass, to obtain glycol that is substantially free of water. Alternatively, the treated solution may contain substantial amounts of water e.g. at least 20% or any other amount of water that is acceptable for use of the product obtained. The method may be operated to obtain a predetermined water content in the glycol.

In an embodiment of the invention, a solution of glycol containing water is obtained and then subjected to alternate steps in decrease the water content i.e. increase the glycol content, of the solution. For example, an aqueous glycol solution having a glycol content of for instance 70-80% could be subjected to steps to increase the glycol content to for instance 98% or other required glycol content. One such alternate step is to subject the aqueous glycol solution to infra red heat in sufficient intensity and for sufficient time to achieve the decrease in water content. It is understood that one or more of the above steps in the treatment of the aqueous solution for removal of contaminants may be eliminated, depending on the quality of the aqueous solution of glycol that is to be fed and treated according to the present invention, and the quality of the treated solution. If the steps are used, they are preferably used in the sequence discussed above. It is understood that treatment steps may be eliminated, other treatment steps may be used, and/or the sequence of steps may be altered.

The system of the present invention is shown in Figure 5 and is understood to be applicable to the embodiments of the invention shown in Figures 3 and 4, however, the system is also applicable to the embodiments of the invention shown in Figures 1 and 2, incorporating the spray systems illustrated therein. In the embodiment of Figure 5, the aqueous waste stream is treated prior to being fed to the apparatus shown in Figure 5 for removal of solid material, for the separation of hydrocarbons and further solid material and for the separation of methanol or other volatile material, as necessary, as discussed above.

In Figure 5, waste stream 221 after any such pre-treatment is fed through valve 222 to feed pump 223. Feed pump 223 pumps feed liquid through transfer line 224 to the evaporation unit for processing until desired concentration is achieved. Solution in holding tank 235 may be fed through transfer line 236 to treatment feed tank 233. From treatment tank 233, solution may be fed through valve 232 to fluid mix tank 225. In fluid mix tank 225, the feed liquid is treated with chemicals e.g. surfactants, to effect flocculation of solid material that may be in the feed liquid. The treated feed liquid is fed from fluid mix tank 225 through valve 226, pump 227 and valve 228, to decanting container 229. In decanting container 229, flocculated material is separated, de-watered and discharged through outlet 230. The remaining liquid is fed through transfer line 31 to ceramic or polymetric filter 250, which has been discussed above. The treated fluid from filter 250 is passed through a transfer line to ion exchange unit 251 , which has been discussed above. From ion exchange unit 251 , the treated fluid is discharged through outlet 252.

As discussed above, some or all of the above treatment steps may be used.

It is understood that the method of the present invention may be operated as a continuous process and may be fully automatic. However, in preferred embodiments of the invention, the method is operated as a batch process, with or without recycle of at least part of solutions in some steps in the method.

The method and apparatus of the present invention provide for the recovery of glycol from aqueous glycol solutions in a manner that does not require the heating of the solutions in order to effect the separation. The method may be operated so that exhausted air will meet environmental regulations for such air. In addition, the method is versatile in that it is able to accept pure solutions of glycol in water or solutions that are contaminated with solids, hydrocarbons, methanol and/or salts, as would typically be obtained from an airport or other sources.

The method may be used to treat a variety of aqueous solutions of glycol, including automotive anti-freeze, aircraft de-icing fluids, industrial HVAC coolants and heat transfer fluids.

The method of the present invention may also be used to treat aqueous solutions that do not contain glycol, using procedures and steps similar to those discussed above with respect to glycol. In particular, the method may be used to concentrate such solutions, by removal of water therefrom, to facilitate handling and/or transportation of the solutions, reduce volumes of liquid that require further treatment or for any other reason where a more concentrated solution is beneficial.

Although preferred embodiments of the invention have been described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.

Claims

CLAIMS:

1. A method for separating glycol from a waste water solution of glycol and water, the method comprising directing an atomized mist of waste water into a flow of air to create a turbulent mixture of waste water and air, directing said turbulent mixture through a set of orifices and panels, wherein such mixing results in the evaporation of water and a concentration of collectable glycol.

2. The method of claim 1 , wherein said flow of air is from about 10,000 cfm to about 50,000 cfm.

3. The method of claim 2, wherein said atomized mist of waste water is provided at pressures of between about 150 and about 350 psi.

4. The method of claim 2, wherein said air has a relative humidity of below 100%.

5. The method of claim 4, where said air has a relative humidity of below 40%.

6. The method of claim 1 , wherein said panels comprise a first panel and a second panel in series, said first panel comprising a vertical panel having staggered rows of vertically arranged angles and said second panel comprising two rows of vertically arranged S shaped plates, each S shaped plate having a capture vane or fluid hook.

7. The method of claim 6, wherein said first and second panels each have an orifice therein for effecting a flow path of atomized waste water and air.

8. The method of claim 6, wherein de-misting of said mixture of waste water and air occurs in said panels.

9. The method of claim 1 , wherein said collectable glycol is about 80% or more glycol.

10. A method for the treatment of a solution of glycol and water to effect separation of glycol therefrom, comprising: (a) feeding air into a chamber, said air having a relative humidity of about 100% or less;

(b) spraying a first solution of glycol and water into said chamber of air;

(c) collecting a second solution of glycol in said chamber, said second solution having a higher concentration of glycol than said first solution; and

(d) discharging air from said chamber, said air so discharged having an increased relative humidity.

11. The method of Claim 10, wherein the air discharged from the chamber is essentially free of glycol.

12. The method of Claim 11 , wherein at least part of the second solution of glycol of step (c) is recycled to step (b).

13. The method of Claim 11 , wherein the first solution of glycol and water is sprayed into the chamber in the form of an atomized liquid.

14. The method of Claim 13, wherein the first solution of glycol and water is sprayed into said chamber counter-current to flow of said air through said chamber.

15. The method of Claim 11 , wherein the second solution of glycol contains a pre-selected concentration weight of glycol.

16. The method of Claim 11 , wherein the spray of the first solution of glycol and water contacts at least one panel having chevron grooves thereon.

17. The method of Claim 11 , wherein the solution of glycol and water is obtained from an airport.

18. The method of Claim 11 , wherein the solution of glycol and water is obtained from an industrial location.

19. The method of Claim 11 , wherein the air being fed to the chamber is heated.

20. The method of claim 11 , wherein the aqueous solution being sprayed is heated.

21. A method for the separation of glycol from an aqueous waste stream of glycol and one or more of hydrocarbons, solids, methanol, salts and other contaminants therein, comprising subjecting the stream to one or more of the following steps:

(a) subjecting the waste stream to treatment to effect separation of hydrocarbons and solids, said hydrocarbons being removed as a first light fraction and said solids separating as a heavy fraction;

(b) subjecting the waste stream to non-thermal fractionation to separate methanol and other volatile matter therefrom; and

(c) subjecting the treated stream so obtained to effect separation of glycol therefrom, said treated stream being essentially free of hydrocarbons, solids, methanol and salts, said separation comprising the steps of: (i) feeding air into a chamber, said air having a relative humidity of less than about 100%;

(ii) spraying first solution of glycol and water into said chamber of air; (iii) collecting a second solution of glycol in said chamber, said second solution having a higher concentration of glycol than said first solution; and

22. The method of Claim 21 , wherein the second glycol solution of (c)(iii) is subjected to at least one of the following steps:

(d) subjecting the waste stream to flocculation;

(e) subjecting the waste stream to microfiltration and/or nanofiltration; and

(f) subjecting the waste stream to an ion exchange step to remove remaining metals and chlorides.

23. The method of Claim 22, wherein steps (d)-(f) are carried out in sequence.

24. The method of Claim 22, wherein at least one of steps (d)-(f) is omitted.

25. The method of Claim 22, wherein the aqueous waste stream is obtained form an airport.

26. The method of Claim 22, wherein the aqueous waste stream is obtained from an industrial location.

27. A method for the treatment of an aqueous solution to effect a concentration thereof, comprising:

(a) feeding air into a chamber, said air having a relative humidity of less than 100%;

(b) spraying a first aqueous solution into said chamber of air; (c) collecting a second aqueous solution in said chamber, said second solution having a reduced water content than said first solution; and

28. An apparatus for concentrating glycol from waste water sources containing water and glycol by evaporation of water, said apparatus comprising;

- a housing having a base portion and defining an enclosed chamber;

- particle separator means upstream of said spray nozzle; and

- a fan suction means adjacent and operatively connected to said housing for providing a flow of air countercurrent to the flow of said atomized mist of waste water such that said atomized mist of waste water is drawn towards and contacts with said particle separator means, wherein said water evaporates and said glycol collects and falls downwards from said particle separator means.

29. A system for concentrating glycol from waste water sources containing water and glycol by evaporation of water, said apparatus comprising;

- a waste-water filtration unit for pretreating waste-water;

- a housing having a base portion and defining an enclosed chamber, said housing being operatively connected to said filtration unit for receiving pretreated waste-water; - at least one spray nozzle for providing a flow of an atomized mist of waste water in said housing; - particle separator means upstream of said spray nozzle;

- a fan suction means adjacent and operatively connected to said housing for providing a flow of air countercurrent to the flow of said atomized mist of waste water such that said atomized mist of waste water is drawn towards and contacts with said particle separator means, wherein said water evaporates and said glycol is concentrated and collects and falls downwards from said particle separator means; and

- a waste-water filtration unit operatively connected to the housing to receive concentrated glycol for further filtering and cleaning for removal of certain contaminants.