MXPA99006589A - Distillation process with reduced fouling - Google Patents

Abstract

There is disclosed a method and apparatus for removing a contaminant from a fluid feed stream containing the contaminant. The method includes comprising the steps of providing a feed stream (10) and heating it in a first step (18) to at least partially remove some of the contaminants and recover energy from a concentrate and distillate generate. Further heating the feed stream in a second heating step (20) in a heated separator generates a saturated vapour fraction (30) and a concentrate liquid contaminant fraction. The vapour fraction may be compressed (32) to generate a temperature differential in the reboiler exchanger (34) with the vapour fraction being passed into contact with a reboiler exchanger to provide a stream of condensed vapour from the reboiler. The stream may be circulated through the reboiler exchanger and the heated separator to maintain from about 1%to about 50%by mass vapour in the stream. The apparatus includes a unique configuration of a vapour compressor, heated separator in combination with a forced circulation (42, 44, 38) circuit to generate the decontamination result.

Description

DISTILLATION PROCESS WITH REDUCED ACCUMULATION FIELD OF THE INVENTION The present invention is directed to a highly efficient water distillation process and to an apparatus therefor, and more particularly, the present invention is directed to a highly efficient water distillation process that minimizes the accumulation and fouling of operating equipment. during long periods of operation.

BACKGROUND OF THE INVENTION Generally speaking, water distillation is a highly effective method of vaporizing a distillate of pure water and recovering a concentrated liquid that has a large amount of non-volatile components. This method of the process can be an effective means to recover clean, pure water, from contaminated sources. However, water distillation processes typically have several problems, not least of which can be accumulation or fouling of the apparatus with minerals or other components coming from the fluid that is distilled. Common encrusting compounds consist of calcium, magnesium and silicon. The accumulation, or to a greater degree, the incrustation of heat transfer surfaces has a detrimental effect on the capacity of heat transfer components, causing conventional distillation processes to be inoperable. Another common problem with typical water distillation processes is that of the high power requirements. Without a means to effectively recover the power supply, the energy required is equivalent to the latent heat of vaporization of the water at a given pressure / temperature. Water distillation under this condition is not commercially viable for water repair applications. The methodology of the state of the art is directed to the current technology that has been established in U.S. Patent No. 4,566,947 and in French Patent No. 2,482,979. These references are general references for removing contaminants by distillation or other purification techniques and do not refer to the problems that are solved by the present invention. Several variables must be considered to overcome the problems with conventional distillation methods. The following three equations describe the basic relationships of heat transfer within a water distillation system: Q (total) U * A * LMTD (1) ^ > - (sensible heat) m * CP * (T1 - T2) (2) «(latent heat) m * L (3) where Q amount of heat transferred (BTU hr "1) U overall heat transfer coefficient or system capacity to transfer heat (BTU hr1 foot" 2 F "1) A heat transfer surface area (foot2) LMTD logarithmic mean of the temperature difference or thermal conduction of the system (F) m mass flow of the fluid in liquid or vapor state (Ib "1) Cp = heat specified from the fluid (BTU hr "1 F" 1) T1, T2 = temperature of the fluid entering or leaving the system (F) L = latent heat of vaporization or condensation (BTU Ib "1) In order to have an efficient distillation system, the quantity of heat exchanged and recovered, Q, expressed by the equations stated above, must be maximized, while at the same time fulfilling the practical limits for the remaining variables and avoiding the embedding and accumulation. For a given fluid and the fluid dynamics within a given heat exchanger apparatus, the variables U, Cp and L are relatively non-variable. Therefore, careful consideration must be given to variables A, QA "1, LMTD, m, and T1 and T2, to overcome the problems associated with the distillation of contaminated water." To fully overcome the problems related to distillation of contaminated water and eliminating fouling, other essential factors must be considered beyond the basic equations stated above: the regime by which heat is transferred into the distillation system, known as heat flow or QA "1 (BTU hr "1 foot" 2) the level of contaminants in the concentrate; the final boiling point of the concentrate in relation to the saturation temperature of the vapor stream; the degree of supersaturation and the precipitation level of the concentrate; and; - • the vaporization level of the evaporation stream. Until the arrival of the present invention, it was not possible to carry out for a continuous long-term period the maximum amount of heat transferred and recovered with a distiller-water process, without the tendency to accumulate or embed. A process has been developed which is both energy efficient and eliminates the incrustation problems previously found in the distillation of contaminated water, contaminated with organic, inorganic, metals, among them. (inter alia) INDUSTRIAL APPLICATION The present invention has suitability in the distillation technique.

DISCLOSURE OF THE INVENTION The invention is predicated on the union of two distinct concepts, both of which have previously been uniquely identified in the state of the art, but which have not been uniquely configured with the synergistic effect resulting from the present invention. . It has been found that by starting a conventional vapor recompression circuit together with a uniquely configured forced convection heat transfer and recovery circuit, that very desirable results can be obtained in terms of maximizing heat transfer and maintaining the desired non-conductive forced convection circuit for inlay interchangers, which are typically found practicing normal distillation methods. An object of the present invention is to provide an improved efficient process for allocating water containing organic, inorganic compounds, metals or other contaminating compounds with the result that it is a fraction of purified water free of contaminants, which additionally does not involve any incrustation of the distillation apparatus. A further object of the present invention is to provide a method for removing contaminants in a fluid feed stream containing contaminants using a reboiler exchanger and a heated separator, characterized in that the method comprises the steps of: a) providing a current of feeding; b) heating the feed stream in a first stage to at least partially remove some of the contaminants from the feed stream and recover the energy of a concentrate and the distillate formed from the heating; c) heating the feed stream in a second heating step in the heated separator to generate a vapor fraction and a concentrated liquid pollutant fraction; d) compressing the steam fraction of step c) to generate a temperature differential in the reboiler exchanger; e) passing the vapor fraction in contact with the reboiler exchanger to provide a condensed distillate from the reheat exchanger; f) circulating at least a portion of the concentrate through the reboiler exchanger and the heated separator to maintain a circulating mass to vapor mass ratio from about 300 to about almost 2; and g) collecting the condensed distillate substantially free of contaminants to prevent fouling and the accumulation of the heated surfaces of the reboiler exchanger and the heated separator. It has been found that by controlling precisely the ratio of the circulating mass on a scale of less than 300 to almost twice that of the fraction of vapor that is compressed, several desirable advantages can be realized: 1.- The circulating concentrate through the the evaporator side of the reboiler will contain a precisely controlled fraction of vapor close to 1% to 50% of the mass of the circulating concentrate; 2.- By controlling precisely this fraction of steam, the rise in the temperature of the circulating concentrate remains very low (approximately 1F) and the cold heat exchange surfaces remain wet, at a temperature close to that of the circulating fluid. This reduces the risk of the accumulation of these surfaces; 3. With this controlled low vapor fraction, the concentrated fluid within the exchanger is subjected to an additional localized concentration factor of less than 1.1, avoiding localized precipitation of the scale components; - 4.- As the vapor fraction increases and the concentration factor increases while passing through the reboiler, the velocities of the current increase significantly thereby reducing the risk of accumulation; 5.- By allowing a controlled fraction of vapor inside the evaporation fluid, significant heat transfer can be made through the latent heat media, without embedding; 6.- Due to the elevation of the temperature of the evaporator side of the reboiler that is kept very low, the LMTD of the reboiler is maintained, with which the compression energy is kept very low; Y 7. - Adjusting the heat flow, the temperature of the surfaces wetted by condensation and evaporation are kept close to those of the saturated steam condition. The type of boiling experienced will vary from mainly forced convection to the boiling of stable core of wet surfaces. It is an object of the present invention to provide a method for removing contaminants from a feed stream having contaminants using a heated separator and a heat exchanger, and preventing buildup and fouling in the separator and in the heat exchanger. heat, characterized in that the method comprises: a) generating a vapor fraction of the feed stream exposed to the heated separator substantially free of contaminants and a separate fraction leading to the concentrated contaminants; b) compress the vapor fraction to raise the temperature of the fraction that carries the contaminants beyond the temperature - - "- of the heated separator, c) passing the vapor fraction in contact with the heat exchanger to form a condensed distillate, and d) keeping the heated surfaces of the heated separator and the heat exchanger at least in contact with the fraction Concentrate of contaminants by continuously circulating the fraction through the separator and the heat exchanger in a circulating mass to vapor mass ratio of approximately 300 to almost 2 to avoid the formation and accumulation of flakes of the hot surfaces.

A further object of the present invention is to provide a method for removing contaminants from a fluid feed stream containing volatile and non-volatilizable contaminants employing a reboiler exchanger and a heated separator, characterized in that the method comprises the steps of : a) provide a feed stream; b) heating the feed stream in a first stage to at least partially remove some of the contaminants from the feed stream and recover the energy from a concentrate and distillates generated from the heating; c) heating the feed stream in a second heating step in the heated separator to generate a vapor fraction and a concentrated fraction of liquid contaminant; d) passing the vapor fraction through a distillation column while in contact with a reflux of distillate from the restoration fraction; e) compressing the vapor fraction to generate a temperature differential in the reboiler exchanger; f) passing the vapor fraction in contact with the reboiler exchanger to provide a condensed distillate from the reboiler exchanger, g) recirculating a portion of the condensed distillate to the distillation column as a reflux of distillate; h) circulate at least a part of the concentrate through the reboiler exchanger and the heated separator to maintain a ratio of - mass circulating to mass of steam of approximately 300 to approximately almost 2; and i) collecting the condensed distillate substantially free of contaminants; With respect to the apparatus, yet a further object of the present invention is to provide a fluid treatment apparatus for treating a feed stream containing at least one contaminant to produce a free tributary of said at least one contaminant, characterized in that the apparatus comprises in combination: steam recompression means including a first heating means for heating the feed stream; spacer means heated in fluid communication with the first heating means to form a vapor fraction and a concentrated fraction; compressor means for compressing the vapor fraction; heat exchange means in fluid communication with the compressor means to recover the latent heat of the condensed vapor; and a forced circulation circuit including: a pump means; means of heat exchange; pumping means in fluid communication between the heated separator means and the exchanger means; _ fluid communication means between the heat exchanger means and the heated separator means forming a forced circulation circuit; the pumping means for selectively varying a rate of fluid flow through the exchanger means to selectively vary the amount of vapor fraction through the exchanger means. In a general way, in a possible mode, the distilled water is evaporated and passed through a mesh pad to remove any retained water before entering the compressor. The compressor raises the pressure and temperature of the steam stream above that of the heated separator to allow effective heat transfer through the reboiler heat exchanger. The steam stream subsequently enters the reboiler where it is superheated and condensed to the distillate. The heat energy is transferred to the circulating concentrate of the heated separator where, in order to control the mass of the circulating concentrate to the steam stream, on a scale of less than 300 to almost 2, less than 50% of the vapor, more precisely less than 10. % of the steam is generated in the circulating concentrated stream. This vapor phase absorbs the heat transferred by the latent heat of vaporization, while at the same time it allows the temperature to rise in the circulating concentrate to increase more than approximately 1 F. The clean distilled water at the temperature and pressure of condensation, they pass through the preheater to recover the sensible heat part of the system for the incoming feed stream. Simultaneously, a part of the concentrated stream is removed from the heated separator to control the desired concentration of contaminants. This concentrated purge stream at the temperature and pressure of the heated separator is passed through an additional preheater to impart the remaining sensible heat to the feed stream. Additional techniques of pre and post-treatment can be employed as batch or continuous process methods to remove or contain contaminants during the distillation operation, pH control methods can be used to ionize the volatile components or alter the solubility conditions in the concentrated to further increase the exposed distillation process. The reclaimed distilled water can be controlled by the level of purity and the temperature level, which allows it to be reused as process water, reused as distilled water or released into natural water springs that meet or exceed virtually all environmental standards. water quality In terms of the ease of this process, it can be easily used to decontaminate processed industrial water such as that in the refinery, petrochemical, pulp and paper, food, milling, automotive / different or other transportation industries and the manufacturing industries. In addition, applications for leaching water from landfill, desalination, pre-water recovery, well water cleaning, lake recovery, oil field wastewater recovery, as well as to produce any form of feedwater are contemplated. of the kettle, and valuable components concentrated from dilute streams. This list is not meant to be exhaustive, but instead as exemplary. Having thus described the invention, reference will now be made to the accompanying drawings, which illustrate the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of the general process according to an embodiment of the invention described; Figure 2 is an alternate embodiment of Figure 1; Figure 3 is a further alternative embodiment of Figure 1; Figure 4 illustrates, in a schematic form, the typical pressure and temperature conditions around the evaporation components; Figure 5 is a process condensation / evaporation curve for the reboiler exchanger of the system; Figure 6 illustrates the scheme of the flow pattern for the plate of the reboiler / plate exchanger; Figure 7is a graph illustrating the level of vaporization in the reboiler, which occurs in the circulating fluid in relation to the proportion of the mass of the circulating fluid to the mass of vapor; Figure 8 is a graph illustrating the effect resulting from the concentration located in the reboiler with varying vapor fractions; and Figure 9 is a graph showing the test data obtained from a pilot distillation unit. Similar numbers are used in the text to denote similar elements.

MODES FOR CARRYING OUT THE INVENTION Referring now to Figure 1, shown is an example of one embodiment of the present invention. A contaminated water feed stream, generally designated by the number 10, is introduced into a pretreatment stage, generally designated by twelve to remove volatile water and / or perform another pH or condition the stages to prepare the stream of water. feed 10. The volatile components are vented from the feed stream at 14, while fewer volatile components are discharged from the feed stream at 16.

The pretreated feed stream 12 that exits, is then passed to a preheater 18 to raise the temperature of the feed stream to increase the recovery of sensible heat before introduction into a heated separator 20. The feed stream can be divided in multiple streams and passed through other secondary sensitive heat recovery preheaters to maximize the full recovery potential of the unit. These provisions will be appreciated by those skilled in the art. The multiple preheaters can be configured as a single multiple service preheater or separate units as designated by 18 and 22. The separate feed streams are recombined and heated to almost the temperatures of the heated separator, before entering the heated separator 20. If If desired, the feed stream can also be introduced into the forced circulation stream to create a local dilution effect in the reboiler. The heated separator may comprise a multiple separation unit, such as a cyclone separator. The lower section, usually designated by the number 22, has a cyclonic action to suspend the solid material in the concentrate and discharge what is referred to as "purge" or concentrate as designated by line 24. The purge regime 24, continuous or batch, controls the concentration of the components in the heated separator 20, thus regulating the degree of saturation of the concentrate, the degree of supersaturation , the subsequent precipitation of the solids and the boiling temperature inside the heated separator 20. The purge 24, at the temperature of the heated separator is passed through the secondary preheater 26 for heat recovery for the supply current for the line 28. The purge stream 2 is 'reduced' to a temperature within about 3F to approach the feed stream at 22. The upper section of the heated separator 20, which contains highly saturated steam, is dedicated to vapor / liquid separation and may contain these characteristics as a mesh pad (not shown) for attaching the liquid drops of the stream. The vapor leaving the heated separator 20 and generally indicated by the line 30 constitutes the distillate with environmental quality and depending on the components present in the feed stream it may comprise potable water or boiler-quality feed water. is transferred to the compressor 32 to raise the pressure and temperature of the steam stream T by that of the heated separator 20. The steam stream can be at any pressure leaving the heated separator, including under vacuum. This vapor is saturated mainly under the conditions of the heated separator 20, however, it can be supersaturated if the concentrate contains components at a sufficient concentration to increase the boiling point of the vapor. This concept is known as boiling point elevation or BPR and must be understood in such a way that compression can be roughly compensated. Does the additional energy imparted to the steam stream produce the required LMTD or thermal conduction necessary to effect heat transfer within the heat exchanger? reboiler, generally designated by the number 34. The compressor or blower, designated by the number 32 can be any device known to those skilled in the art, which can induce from about 3 to 10, psi of hydrostatic head in the steam and flow to the desired level of the vapor mass. The actual hydrostatic head required of the compressor 32 is specifically determined by each unit by the steam conditions in the heated separator 20 and the LMTD required by the reboiler 34. The steam leaving the compressor 32 is mainly superheated steam. The degree of overheating is dependent on the discharge pressure, and the efficiency of the compressor device 32. The reboiler exchanger 34 functions to condense the compressed steam received from the compressor 32 to the distillate that drains from the reboiler 34 through a receiver of condensate 4, designated by the number 36. This stage captures the superheating and latent heat of the steam stream and accepts it by means of the thermal device into the concentrated circulation stream designated by number 38. The distillate accumulated in the receiver 36 is usually a saturated liquid at a specific temperature and pressure condition. The additional sensitive heat The content in the distillate is recovered by passing the hot distillate using the pump 40 backwards through the preheater 18, where the exiting current is cooled to approximately 3F within the input feed stream from 12 onwards. that by using a concentrate circulation pump 42 to circulate a prescribed amount of concentrate from the heated separator 20, through the reboiler exchanger 34, which is significant, it can be performed without the risk of accumulating or embedding the surfaces of the exchanger. The amount of the circulating concentrate is specifically selected to be in a range of less than 300 to almost 2, thus accurately generating a vapor fraction of almost 1% to less than 50% in stream 38 leaving the exchanger. reboiler 34. This mass flow can be varied and fixed to the desired parameter using a control device generally designated by the numeral 44. More specifically, the desired objective for the vapor fraction in the circulating current 38 that exits, when the very contaminated feed, the vapor fraction is less than 10%. The steam generated in stream 38 is equivalent in mass to the amount that passes through the compressor and recovered as distillate at 46. The steam created in the reboiler exchanger 34, even though it is very small in mass fraction (from about 1 to 10% of the circulating mass), absorbs most of the heat transferred from the condensation side of the reboiler 34. The selection of the vapor fraction and the circulation rate of concentrate is an important factor in reducing the accumulation and fouling. Up to a higher limit, this parameter is very important to establish a very low temperature rise over the concentrated circulating fluid to maintain an effective LMTD without a temperature found in the reboiler exchanger 34. Any elevation of the temperature will quickly eliminate the LMTD and stop the heat transfer. For example, if the pressure of the circulating concentrate in the reboiler so that the fluid can not create some steam, the temperature would increase the absorption of sensible heat until the LMTD would not exist and in this way the heat transfer would decay. The overpressure of the concentrated circulating system, which consists of static and friction load losses, is designed to be minimal. In fact, the overpressure is mainly equal to the static charge loss of the exchanger, as the dynamic pressure drop of the exchanger is minimized. The circulating concentrated flow is then selected to achieve almost 1% to 10% of the vapor friction at the outlet line 38. The resulting temperature rise is very low and the LMTD remains at its design value. Referring now to Figure 2, an alternate process scheme is shown which allows the purge 24 of the heated separator 20, which is adjusted to the overall concentration effect or concentration factor (CF) of the system, to create a supersaturated concentrate with regarding one or many of the components to cause precipitation. As the solids form and simulate within the heated separator 20, the purge 24 is passed through a solid / liquid separation device, generally designated by the number 50 to remove solids or sediments. As an alternative, the solid / liquid separation device 50 can be located between the reboiler pump 42 and the exchanger 34, in a retrograde or full flow arrangement. The recovered liquid is further recycled back to the heated separator 20 as indicated by 52 and a part representing the purge amount, is further passed through the preheater 26 to recover the heat and cooled to about 3F. the solid / liquid separation device 50 can be in any form such as hydroxygel, centrifugal settler, gravity settler, centrifuge, separation by settling, and known to those skilled in the art. This process is particularly attractive when the main objective is to recover a compound as a solid, OR when the compound is of significant commercial value. Referring further to Figure 3, a further variation of the process is shown, by which the vapor stream may contain a part of a particular contaminant from the feed stream. The heated separator 20 is equipped with a fractionating column 54 in front of the compressor 32 and the suction line of the compressor 30. The column 54 is used to fractionate and purify the contaminant using multiple stages in combination with the reflux of cold water, clean, designated by the number 56. The reflux may be provided from either upstream or downstream of the precalcant 18 or a combination, depending on the reflux temperature required. This variation of the process is attractive when the feed stream contains, for example, volatiles such as hydrocarbons, glycols, ammonia, etc. Figure 4 illustrates the typical pressure and temperature relationships of the various streams around the vaporization part of the process. Numerical references of Figures 1 to 3 are made for this discussion. Although the specific process parameters are shown by way of example, they are modifiable to suit any specific distillation application. This diagram shows the conditions based on a fluid without boiling point elevation and the heated separator 20 operating at pressure slightly above atmospheric, 16 pisa and at 212.5 F. the rise of circulating concentrate temperature is less than 1 F for a 2.5 psi reboiler pressure drop. The vapor fraction of the circulating current is approximately 10%. The conditions around the reboiler exchanger 34 can be represented in a vaporization / condensation curve as shown in Figure 5. On the condensing side of the superheated exchanger it enters point C at approximately 250 F and 21.5 steps and is condensed to the pressure Saturated steam at point C, approximately 231.8 and 21.4 psia. This zone is commonly referred to as the superheat zone and consists of approximately 2% of the surface area of the exchanger, the remaining area being the area by which the latent heat of condensation is released. A slight drop in pressure and temperature will occur through the exchanger 34 due to the inherent pressure drop of the heat exchanger. The exit conditions reach approximately 231.6 F and 21.4 psia. The surface temperature on the condensing side will be lower than the saturation temperature of the inlet vapor, thus forming a condensed film on the surface of the heat exchanger. The heat transfer will therefore occur outside of the wet wall condition which maintains the effective temperature of the film at the saturation temperature of the vapor. The distillate will drain from the exchanger to the condensate receiver 36 at point D keeping the reboiler free of liquid and exposing the entire surface of the exchanger to the condensation process. On the vaporation side the concentrate enters the exchanger in a counter-flow manner from the bottom at the point at approximately 212.5 F and 18.6 psia after the circulation pump 42. The circulation speed is adapted in such a way that the ratio The mass of concentrate is at least 10 times higher than the speed or rate of the vapor. The temperature of the concentrated fluid begins to rise at point A 'and then rises to approximately 213.2F as point B is reached, where the static charge is exceeded and the pressure reduced to 16.1 psia. While the concentrate rises to the exchanger 34, steam begins to form by forced convection, absorbing the latent heat transferred. Increasing the mass of fluid on the vapor side until the ratio of the circulating mass to the mass of steam falls within the desired scale, the boiling effect is controlled within the forced convection, and the boiling regions of the stable core . Because of the flow of High liquid mass, surface and heat transfer remains wet at a temperature equivalent to the saturation temperature of the newly formed vapor. Ensuring further that the flow rate (QA "1) for an exchanger is below 6000 BTU hr" 1ft "2, for an exchanger it is below the temperature elevation for the steam side can be maintained below 1F and the wet film surface is maintained, thus eliminating the risk of fouling.If the flow rate is too high, the pressure drop due to the instantaneous acceleration of the vapor temporarily exceeds the static charge, available, resulting in unstable temporary backflow and the possible failure of the wet heat transfer surface.This may result in the accumulation of the heat transfer surface below the heat fluxes of 6000 BTU hr "1ft" 2, and within the range of the mass'concentrated circulating to the mass of vapor less than 300, there exists a region where the vapor and the liquid can coexist in stable operation and maintain a surface of heat transfer completely wet on the vaporación side of the reboiler, without the risk of accumulation or incrustation. The reference to points A to D is also found in Figure 6. • Figure 6 illustrates the elevation view of a highly efficient heat transfer exchanger 58, known to those skilled in the art as a plate and frame exchanger, by means of which the rows of the packed plates 60 generally stacked are disposed between two solid frames 62 and 64. These devices are well known for their compact size and their ability to have very high U-values or coefficients of very high heat transfer. This type of exchanger, arranged as a single-pass countercurrent flow configuration, is well suited for the present invention and specifically offers the following benefits for practicing the present invention: 1. - The plate-type exchanger offers a fixed, low static charge, and a very low pressure drop in the concentrated circulating fluid or vapor side, while providing a relatively high heat transfer coefficient; 2.- The heat flow can be easily adjusted by adding more surface area or plates in a given frame; 3. The condensation side of the plate frame design is free of drainage and has low pressure drop, while maintaining a relatively high heat transfer coefficient; 4.- The highly effective heat transfer coefficient allows surface temperatures to be very close to both fluid flow temperatures reducing the risk of accumulation; 5.- The high turbulence and the equivalent high fluid velocities result in low accumulation and keep the solids in homogeneous suspension as they pass through the exchanger; 6.- There are no hot or cold spots and there are no dead flow regions inherent to the design of the plate frame, reducing the risk of accumulation or embedding; 7.- The plates are smooth and well finished reducing the risk of accumulation; and 8.- The low fluid residence time reduces the risk of precipitation, since there is insufficient time to reach equilibrium and generate fouling contaminants. More generally, the plate-type plate heat exchanger is very compact and can be cost effectively provided with bizarre alignment plates to resist corrosion of the fluid and common stress corrosion cracking for salting type applications. Other types of exchangers, shell and tube type, of double pipe of finned tube, of spiral type, can also be considered by those skilled in the art, as long as the specific requirements of the invention are maintained. Figure 7 is a diagram showing the preferred design interval, globally designated by 66, for the proportion of the concentrated mass flow circulating in relation to the mass flow of steam. The desired range of about 10 to 100 results in a vapor fraction of less than 10% to almost 1%. Figure 8 is a diagram showing the resulting impact on the local concentration factor CF exchanger relative to the risk of additional supersaturation and precipitation within the heat exchanger. Generally, the concentration factor of the system can be expressed as follows: CFjOTAL = CFpuRGA • CFiNTER CHANGER The concentration that reaches the steady state in the heated separator results from the stable removal of the vapor in equilibrium with a continuous purge of the heated separator. The value of the CFTOTAL is typically in the order of minus 5 to about 20 times, depending on the level and type of contaminants in the feed stream. Also dependent on the mass of steam that is removed from the reboiler, the CFINTER CHANGER is determined (between 1.0 and 1.1) and the rate or purge rate is adjusted in such a way that the desired levels of concentration are not exceeded in the reboiler. A typical example can be shown as follows: The feed stream contains 20,000 TDS and this is desired not to exceed 100,000 TDS in the concentrate. It is determined that the most effective mass proportion will be 20, resulting in a vapor fraction of 5%, from Figure 7. The CF | NTERCAIVIBIATOR is located from Figure 8 which is approximately 1.07 is calculated to make (100,000 / 20000) = 5 CFPURGA is calculated to be (5 / 1.07) = 4.7 Therefore, the corrected purge rate or rate must be (1 / 4.7) = 21% of the input power supply current. Therefore, making use of a vapor recompression process in combination with a forced convection heat transfer system, and following the steps of carefully selecting the mass flow rate of the circulating system to the mass flow of the steam stream to be less than 300 to about 2, more specifically at a ratio of about 10 to 100, selected a heat flux less than 6000 BTU hr "1 ft" 2, and manipulating a purge stream to achieve the desired concentration effect (CF), e! The result is a very efficient water distillation unit that is not susceptible to accumulation or fouling during long incrustation periods. Combining the two known process schemes with a unique heat exchange configuration, and more particularly designed with a specific circulation rate of concentrate, not previously taught by the prior art, allows the present invention to provide an effective method for distilling free water of contaminants, without the risk of accumulation and embedding. The following examples serve to illustrate the invention.

EXAMPLE 1 This example calculation is a means to demonstrate the heat balance around the reboiler exchanger. This example represents a distillation design basis designed to recover 53,000 USGPD of clean distillate from a contaminated source.

EXCHANGER INFORMATION Area Area 3,200 ft2 Type Packaged plate rack Corrected LMTD 10.33 F Calculated service performance (3,200) * (542) * (10.33) 17,908,217 BTU hr "1 Calculated heat flow (17,908,217) / (3200) 5596 BTU hr" 1 ft "2 CONDENSATION SIDE Input conditions - 250 F @ 21.5 psia (overheated) Output conditions 231.6 F @ 21.4 psia Saturated condensing temperature 231.8 F @ 21.5 psia Latent heat of condensation 957.6 BTU Ib "1 @ 21.5 psia Steam flow 36.7 Usgpm = 18,352 Ib hr" 1 QUALISEDWATCH (18,352) * (1.0) * (250-231.8) QCONDENSED (17,908,217-334,006) 17,574.21 1 BTU hi-1 Calculated flow (17,574,211) / (957.6) 18,352 Ib hr "1 Evaporation side Entry conditions 212.5F © 18.6 psia Output conditions 213.2F @ 16.1 psia Latent heat of vaporization 968.7 BTU hr "1 @ 16.1 psia Preparation of circulating mass to vapor mass 10 Concentration circulation regime 370 Usgpm 184,926 Ib hr" 1 Vapor flow 18,352 Ib hr "1% vapor (18,352 / 184,926) = 10% QEVAPORATED (18,352) * (968.7) 17,778,769 BTU hr" 1 SENSITIVE Q (184,926) * (1.0) * (213.2-212-5) 129,448 BTU hr "1 QTOTAL (17,775,747) + (129,448) 17,908,217 BTU hr" 1 This example illustrates that 10% of the vapor fraction created in the circulating fluid will capture 99% of the heat transferred from the condensing side and will increase the temperature of the circulating fluid by less than 1 F, even though there is 10 times the mass of the fluid circulating.

EXAMPLE 2 A pro-type unit was designed to recover 10,000 US gpd of clean distillate from a leached landfill lake. The unit was tested over a long period of time and detailed data were collected from the performance test during this period. The pilot operated successfully during a period of 4 prolonged months and on inspection was negligible in the reboiler and the heated separator. The equipment used in the pilot test included a Spencer® Compressor Model GF36204E at a differential pressure of 3.0 psi. Standard single-pass plate-frame heat exchangers were used during the test. The characteristics of the leached fluid, the concentrated purge, and the treated effluent were as follows: Parameter Units Feeding Purge Effluent Lixiviada'2 'Approx10% (2) treated'2' BOD mg I "1 26 88 < 10 COD mg I "1 277 1, 207 11 TOC mg l "1 59 549 6 TSS mg I "1 33 145 <2 VSS mg I "1 15 29 < 2 TDS mg l "1 5,473 53,000 < 50 Parameter Units Feeding • Liquefied Effluent Purge'2 'Approx10% (2' treated'2 ' Calcium mg I "1 96 435 <0.05 Magnesium mg I "1 228 1, 990 <0.05 Sodium mg l "1 550 4,650 < 2 Iron mg l "'5 469 .6 Total P mg 1"'1.5 1.5 <0.01 Ammonia As N mg 1"'53 124 0.38'1' Total Alcanidad mg l "'2,353 2,930 1 As CaC03 Chlorides mg l" 217 784 0.2 Sulfates mg 1"350 20,000 <2 Total phenols mg 1"0.08 0.45 .017 Coliform Total Col / 1 OOcc 673 < 3 0 Color TCU 166 800 < 5 Turbidity NTU 131 220 0.1 Note (1) pH adjustment in the pretreatment to control ammonia. Note (2) the values are shown as average values during the trial period The effluent is of such quality that it can be discharged to surface water collectors by virtually exceeding all regulatory guidelines. The energy consumption of the compressor was measured and recorded for several operating points, including compressor drop and recycling conditions. The energy consumption measured was plotted in Figure 9 as energy consumption per 1,000 US ga! for the various distillate flows. The curve of the test data was corrected for the inefficiencies of the compressor over the flow range and a uniform value of the energy consumption of 50 KW-hr / 1000 US gal was derived. Allowing normal compressor efficiencies of approximately 70%, the energy consumption required for the high efficiency distillation unit is approximately 65 KW-hr / 1000 US gal. The purge current averaged approximately 10% of the feed stream over the entire test period, resulting in the average concentration factor (CF) of 4 out of 10. A visual inspection was completed after the test, showing no signs of incrustation in the equipment of the heated separator and the reboiler In terms of the employability of the apparatus within the system, it will be readily appreciated by those skilled in the art as to what the examples of the heated separators, preheater, reboiler, pumps, compressors / blowers, etc., will be very desirable Other modifications will be readily appreciated without departing from the scope of the invention Although the embodiments of the invention have been described above, it is not limited thereto and will be apparent to those skilled in the art. technique that numerous Modifications form part of the present invention as long as they do not depart from the spirit, nature and scope of the invention claimed and described.

Claims (22)

1. A method for removing contaminants from a fluid feed stream containing contaminants using a reboiler exchanger and a heated separator, characterized in that the method comprises the steps of: a) providing a feed stream; b) heating the feed stream in a first stage to at least partially remove some of the contaminants from the feed stream and recover the energy of a concentrate and the distillate formed from the heating; c) heating the feed stream in a second heating step in the heated separator to generate a vapor fraction and a concentrated fraction of liquid contaminant; d) compressing the vapor fraction of step c) to generate a temperature differential in the reboiler exchanger; e) passing the steam fraction in contact with the reboiler exchanger to provide a condensed distillate from the reheat exchanger; f) circulating at least a portion of the concentrate through the reboiler exchanger and the heated separator to maintain a circulating mass to vapor mass ratio of about 300 to about almost 2; and g) collecting the condensed distillate substantially free of contaminants to prevent scaling and accumulation of the heated surfaces of the reboiler exchanger and the heated separator.

2. The method according to claim 1, characterized in that the method further includes the step of removing at least a portion of said concentrate from the heated separator to control the level of said contaminants.

3. The method according to claim 1, characterized in that the method also includes the step of altering the circulation regime of said concentrate.

4. The method according to claim 3, further characterized in that said circulation rate of said concentrate is circulated to maintain from about 1% to about 50% by mass of the vapor.

5. . . The method according to claim 1, further characterized in that said feed stream is subjected to a pretreatment protocol before heating.

6. The method according to claim 5, further characterized in that said pretreatment protocol includes at least one of filtration, ion exchange, distillation, precipitation and evaporation.

7. The method according to claim 1, characterized in that the method further includes the step of recycling the concentrated liquid contaminant fraction.

The method according to claim 1, characterized in that the method further includes the step of raising the temperature of the vapor fraction by compression.

The method according to claim 8, further characterized in that said temperature of the vapor fraction subjected to compression is greater than the temperature of said vapor fraction within said heated separator.

10. The method according to claim 1, characterized in that the method further includes the step of subjecting said condensed vapor to the subsequent treatment protocol.

11. The method according to claim 10, further characterized in that said subsequent treatment protocol includes at least one of filtration, ion exchange, distillation, precipitation and evaporation.

The method according to claim 11, characterized in that the method further includes the step of recirculating the condensed vapor to the first stage for the extraction of heat from the feed stream.

13. The method according to Claim 1, subsequent to step e), characterized in that it also includes the steps of: a) supersaturating the concentrate to precipitate at least one selected solid; b) filter the concentrate; and c) recovering said at least one selected solid.

14. - The method according to claim 1, further characterized in that said circular passage retains moisture on the heated surfaces of said heated separator and said reboiler to reduce the formation of flakes and accumulation.

15. A method for removing contaminants from a feed stream having contaminants using a heated separator and a heat exchanger, and preventing buildup and fouling in the separator and in the heat exchanger, characterized in that the The method comprises: a) generating a vapor fraction of the feed stream exposed to the heated separator substantially free of contaminants and a separate fraction leading to the concentrated contaminants; b) compressing the vapor fraction to raise the temperature of the fraction that carries the contaminants beyond the temperature of the heated separator; ~ c) passing the vapor fraction in contact with the heat exchanger to form a condensed distillate; and d) keeping the hot surfaces of the heated separator and the heat exchanger at least in contact with the concentrated fraction of contaminants by continuously circulating the fraction through the separator and the heat exchanger in a mass to mass ratio of steam of approximately 300 to almost.2, to avoid the formation and accumulation of flakes of the hot surfaces.

16. The method according to claim 15, further characterized in that the circulating mass comprises approximately 10% concentration by mass of steam.

17. The method according to claim 15, further characterized in that said steam is condensed in a plate-piaca type heat exchanger. -. ,. - • - -

18. A method for removing contaminants from a fluid feed stream containing volatile and non-volatilizable contaminants employing a reboiler exchanger and a heated separator, characterized in that the method comprises the steps of: a ) provide a feed stream; b) heating the feed stream in a first stage to at least partially remove some of the contaminants from the feed stream and recover the energy from a concentrate and distillates generated from the heating; c) heating the feed stream in a second heating step in the heated separator to generate a vapor fraction and a concentrated fraction of liquid contaminant; d) passing the vapor fraction through a distillation column while in contact with a reflux of distillate from the restoration fraction; e) compressing the vapor fraction to generate a temperature differential in the reboiler exchanger; f) passing the vapor fraction in contact with the reboiler exchanger to provide a condensed distillate from the. reboiler intercarbidity, g) recirculating a portion of the condensed distillate to the distillation column as a reflux of distillate; h) circulating at least a portion of the concentrate through the reboiler exchanger and the heated separator to maintain a circulating mass to vapor mass ratio of from about 300 to about 2; and i) collect the distillate condemned as substantially free of contaminants.

19. A fluid treatment apparatus for treating a feed stream containing at least one contaminant to produce a free effluent of said at least one contaminant, characterized in that the apparatus comprises, in combination: steam recompression means including a first heating means for heating the feed stream; spacer means heated in fluid communication with the first heating means to form a vapor fraction and a concentrated fraction; compressor means for compressing the vapor fraction; heat exchange means in fluid communication with the compressor means to recover the latent heat of the condensed vapor; and a forced circulation circuit that includes: a pumping means; means of heat exchange; pumping means in fluid communication between the heated separator means and the exchanger means; fluid communication means between the heat exchanger means and the heated separator means forming a forced circulation circuit; - .. the pumping means for selectively varying a rate of fluid flow through the exchanger means to selectively vary the amount of vapor fraction through the exchanger means.

20. The apparatus according to claim 19, further characterized in that said apparatus is self-cleaning.

21. The apparatus according to claim 19, further characterized in that said pumping means circulates said fluid continuously to maintain from about 1% to about 50% of the vapor e-masa mass in said fluid.

22. The apparatus according to claim 19, further characterized in that said means of the heated separator form a value fraction substantially free of contaminant and a concated fraction of contaminant.