Patent Application
20070193739
A cavitation device is used to reduce the water content of used or wastep solutions and slurries, including oil well fluids and muds, solution mining fluids, industrial oil/water emulsions, and other used or wastep aqueous industrial fluids. A main reason for reducing the water content of such fluids is to facilitate their disposal or reuse. Thermal energy from the steam and vapor produced by the non-scaling cavitation device is recycled in steam turbines or piston expander engines, or otherwise facilitates evaporation or condensation to useful fresh water.
In oil and other hydrocarbon production, drilling, completion and workover, fluids are typically circulated down the string of tubes and upwards around the outside of the tubes, contacting the formation surface of the wellbore from which the hydrocarbons are to be produced. In the case of a completion, drilling, or workover fluids an original clear brine is typically prescribed to have a density which is a function of the formation pressure. Oil well fluids may include calcium, zinc, ammonium and/or cesium as cations, and chloride, formate and particularly bromide as anions from any source. Typical sources include cesium chloride or formate, calcium chloride, sodium chloride, sodium bromide, calcium bromide, zinc chloride, zinc bromide, ammonium chloride, and mixtures thereof as well as their cation and anion forming moieties from other sources. The salts and other additives in the completion, drilling, or workover fluid may be partially diluted by the formation water, as a result of contact with the formation. The brines can also become diluted deliberately by the well operator, who may add water to replace fluid lost into the formation, or to reduce the density following a decision that it is too high. Oil field fluids commonly include as ingredients not only various salts but also polymers, corrosion inhibitors, densifying agents such as barium compounds, biocides, solids such as mud additives, and other compounds. Whether or not they are diluted, the oil field operator is ultimately faced with the problem of disposal or reuse. Frequently, finding a permissible site for disposal of such solutions and slurries is difficult and very expensive Disposal is also difficult for other common oil well fluids such as water/oil (or oil/water) emulsions of widely varying composition, including muds. A related point is that if the excess water in dilute fluids is not eliminated or recovered for various purposes, the volume of fluid at the wellsite continues to increase. The cost of trucking to an approved disposal or processing site can be prohibitive in many instances, and accordingly a significant reduction in the volume of such materials is needed in the art. All such fluids originating in the hydrocarbon production industry—the oil and gas fields—may be referred to herein collectively as “oil well fluids.” All such fluids for which our invention is useful, including oil well fluids, may be referred to herein collectively as “industrial fluids.” They will all include at least some water which is to be removed.
Conventional methods of dewatering such fluids, such as distillation or simple evaporation, are very susceptible to scale formation on the heat exchange surfaces, which soon renders the distillation or evaporation equipment inoperable. Conventional methods tend also to be energy inefficient, and do not lend themselves to the use of thermal and electrical energy commonly available at the well site.
Production of hydrocarbons from underground formations generally includes water from the same formations. In 2007 the ratio of water produced to oil produced worldwide is about 5 barrels of water for every barrel of oil produced. As oilfields mature the produced water volumes typically increase. Unfortunately the water produced with oil is not fresh water and is typically highly contaminated with both dissolved salts and suspended solids that include very hard to remove oil droplets. It typically comes from much greater depths than the fresh water aquifers.
At the same time there is only a small amount of chloride-free, fresh water in the world compared to the amount of sea water. It has been logical and common practice to extract fresh water from sea water or other “brackish” waters. One can simply boil sea water and then condense the steam as fresh water. Today desalination of sea water into fresh water is a commonly accepted technology in wide use around the world. Units range from a few gallons per day to 1,000,000's gallons per day. The technology for desalination is evolving with several dominate technologies generally defined as either evaporation or reverse osmosis and as of 2007 the two technologies represent about 50% of the new plants built; although, with the current rate of new membrane technology development it is generally expected that the use of reverse osmosis will grow relative to evaporation. Each has its advantages and there are numerous methods defined in the literature to describe both technologies in detail.
Like seawater, the water produced from hydrocarbon extraction contains chlorides, and it seems logical that technology from desalination could apply to such produced water. In some produced water applications desalination technology does work and is being used successfully. Unfortunately there are some key differences between seawater and produced water. Seawater can be considered a consistent feedstock; therefore, you can design for the most efficient operation based on a number of choices and then amortize the cost of the plant over a long life. You can control the flow into the plant and assume the feedstock will never change. Furthermore, generally size is not an issue and size can improve efficiency particularly with heat exchangers, membranes etc.
Unfortunately, water obtained in hydrocarbon production is not a consistent feedstock. It can vary even in the same field, and composition can change over time. Harsh chemicals are often used in the production of hydrocarbons and the well treatment chemicals contaminate the associated produced water. Typically, produced water contains significant dissolved and suspended organics. Produced water is reactive and changes over time. The water in the formation is in a reduced state; whereas, seawater is fully oxidized and non reactive. Surface handling of produced water often adds oxygen that oxidizes the components of the produced water. Changes in temperature and pressure cause significant scale deposition. Unlike a seawater desalination plant where you control the flow into the plant, with produced water, you must cope with the flow from the formation. Not only does the produced water volume from a well typically increase with time, there are upsets that change everything. An example of an upset might be where oil overwhelms an oil/water separator and the oil intrudes into the desalination process. Typically a desalination plant requires pretreatment of the seawater feedstock. Given the variability of the produced oilfield water it has been very difficult to design the pretreatment system particularly for reverse osmosis membranes.
To evaporate produced water there are some major issues. One is economics. Generally most produced water is re-injected into the same or similar formations. Downhole disposal is an environmentally acceptable alternative to evaporation and it is one of the least expensive alternatives; however, it often requires trucking or piping that adds considerable cost. The other major problem is scale. Scale is inversely soluble with heat. As temperature increases the scaling salts are less soluble. Scale is detrimental to an evaporation process that uses heat. The scale will form first on hot surfaces and that includes heat exchanger surfaces. First there is loss of efficiency. as the scale starts to insulate the hot heat exchanger surface from the fluid. Scale buildup also plugs the heat exchanger. Unfortunately, corrosion must also be considered. Heat can speed the corrosion process and since most produced waters contain chlorides, one must consider chloride stress cracking of metals.
While evaporation in the oilfield is not as simple as desalination, it can be accomplished with a careful process design and it is a proven effective way to dispose of brine. Evaporation is a key technology in numerous industries, including food, chemicals and minerals processing. There are a wide variety of processes and many variations. Different evaporation processes and components were considered in developing this technology. Generally the methods to design such systems are to work out the mass and heat balances of the system and then each component. Components generally include a flash tank where steam vapor separates from the liquid, a source of heat, pumps to add fluid to the process and remove fluid, crystallizers to remove dry solids, solids handling equipment, heat exchangers, mixers, calandrias, evaporative cooling towers, condensers, vacuum pumps, compressors, piping, heat-transfer fluids, vents, packing trays, mist eliminators, economizers, and combinations of all these components. Furthermore the chemistry of the water must be considered as part of the design process. Typically with seawater desalination there is a pretreatment to remove hardness, or to mitigate its effect in the process. Unfortunately oilfield waters typically contain an order of magnitude greater concentration of hardness. Furthermore the hardness can vary from a relatively benign calcium carbonate compound to a nuisance calcium sulfate, but there is also hazardous barium sulfate scale and even radioactive strontium sulfate scaling. In designing a plant a chemical balance must be considered along with the heat and mass balance. Oilfield water chemistry is well defined in various reference books such as the classic textbook by Dr. Charles Patten entitled “Oilfield Water Chemistry” available through DA Campbell and Associates. There are many text books on water chemistry, but Patten is different because it deals with oilfield waters. There are graphs to predict scale formation based on water analysis, pressures and temperatures that are proven reliable and universal for oilfield waters. The scaling indexes have since been refined and reduced to computer programs.
Many evaporation technologies and system layouts are well known and have been practiced for at least 100 years, if not longer.
For example, a simple system might be a source of heat and a flash tank.
One could use any number of components to improve the design and function of a flash tank. For example there is natural circulation and forced circulation to consider. Fluid to be evaporated can be pumped into the tank to turn it into a simple continuous process. For example if you pump the same weight of water into the evaporation tank to equal the pounds of steam vapor being removed then you would have a continuous process. If you consider the mass balance and heat balance you need to know that it takes 1 BTU of heat to raise the temperature of one pound of water one degree. Unfortunately it then takes 970.4 BTU per pound of water to vaporize that water into steam. To evaporate water using this method, you must add heat, generally know as sensible heat, to raise the temperature of the base fluid from the starting point to the boiling point. Then you must add the latent heat of vaporization to run the evaporation. The mass and heat balance are simple equations and for one pound of water evaporated, you need to add the sensible heat to the latent heat and then you can decide how much you want to process per hour and you will know how much energy is required and then you can design your system around your requirements using standard chemical engineering texts, vendor input, handbooks, etc. It is typical to start with a proposed Process and Instrumentation Diagram or P&ID and then work though the mass balance and heat balance. In doing such work it becomes obvious that this simple design is not efficient. If steam is the ultimate goal, or if steam is required in another process then this simple flash tank evaporator works, and one can continue through the design to size the unit and then specify components to build the system. These types of units are typically called steam boilers. They are packaged readily available for purchase, lease or rental in a multitude of sizes and configurations from a variety of sources. Steam drove the industrial revolution and again the technology is very well known and has evolved over time. A conventional steam boiler is not an ideal evaporator of oilfield waters because scale and corrosion rapidly foul the unit and can even cause serious injury.
If you do not need the steam, then it becomes a cost. With desalination, you need fresh water for civilizations to survive. You can afford to pay for fresh water. Oilfield water is a cost that you want to minimize since it offsets the revenue from the hydrocarbons. It is not only a cost, but often an environmental hazard. Using a conventional steam boiler is a very inefficient way to evaporate oilfield waters. The first law of thermodynamics is the conservation of energy. If you make steam, the energy in the steam goes somewhere. If you evaporate produced oilfield waters, the steam in the simple evaporation design goes to global warming. That is both costly and not environmentally sound. If you take advantage of the first law of thermodynamics and “recycle” the steam into the evaporation process, you become far more efficient. That is it takes less energy. For example you could run a simple evaporation process but use the steam to further evaporation with a simple evaporative cooling tower.
If you add a cooling tower to your process essentially you can double the evaporation of the system. One could term this multiple-effect evaporation. There are numerous multiple effect evaporators and generally to be economical you need at least five effects. Simply you must utilize the 2nd law of thermodynamics which says heat moves from hot to cold. Steam at atmospheric pressure cannot boil water at atmospheric. It can only provide sensible heat—that is heat the water to the vaporization point. It cannot boil the water because heat will not move between two bodies that are the same temperature. As you compress steam it goes up in temperature. With some compression you can get more heat in the steam and then take advantage of the second law of thermodynamics. With a multiple-effect arrangement generally the first evaporation tank is at the highest pressure. High pressure steam goes to the next flash tank that is operating at lower pressure and the heat boils that liquid. That steam moves to the third, tank that is lower pressure than the second tank and so on. Systems have been built with 20 or 30 effects. It still takes 970 BTU/pound of water evaporated, but by recycling the steam through multiple effects; you can divide the 970 BTU/pound by the number of effects to get the actual number of BTU's used for pound evaporated. For example, if you have 5 effects essentially you can evaporate water 5 times more efficiently or put another way use only 200 BTU per pound.
Another well known method to enhance evaporation is by using compression. You can use one flash tank, but compress the steam and use a heat exchanger to condense the steam into fresh water. The fluid circulates from the flash tank through a heat exchanger where you condense high pressure steam on the outside of the same heat exchanger. By condensing the steam you get back the latent heat of vaporization and fresh water as a by product. The steam must be hotter than the evaporative fluid. By compressing the steam the temperature goes up and heat moves from the hot to cold or from the hot steam into the lower temperature (although still hot) fluid being evaporated. Vapor compression can either be by thermocompressor or by mechanical vapor recompression (MVR). A thermocompressor simply mixes high pressure steam with low-pressure steam to raise the temperature of the steam. The MVR system relies on an engine driving compressor. MVR can be a very efficient process. There are numerous references in the literature to the efficiency of compression. Systems can equal 50-effect evaporators. If you have high pressure steam, or another high pressure gas thermocompression makes the most sense; otherwise, MVR would be the choice.
All of the above systems use, and require, one thing in common: heat exchangers that are prone to fouling in oilfield environments. Heat exchangers by definition have a hot surface. Again heat moves from hot to cold; therefore, heat moves from the hottest fluid to the heat exchange surface (usually metal) and then to the colder fluid. That means the heated surface is hotter than the fluid and scale is inversely soluble with temperature. That means scale starts to form on the heat transfer surface. As scale forms heat transfer efficiency decreases. There are numerous designs to minimize scale build up on heat transfer surfaces. There are mechanical devices to even scrape the surfaces to prevent scale buildup. A crystallizer is simply a heat exchanger designed to handle very high solids, and is often used in the situations were scale can be a problem. There are a multitude of heat exchanger designs and patented systems to improve heat transfer and to prevent scale buildup. Chemicals can also be used to treat for scale and are often utilized in the oilfield since scale even builds up downhole; however, chemicals add to the cost of systems and an important goal is to minimize costs.
One method to evaporate produced water is to remove the scale-forming chemicals first and then further process the water with the steam into a crystallizer or conventional MVR system. If you remove the hardness, any of the conventional evaporation systems will work. It is common practice to precipitate scale with chemicals or by other means. One method is to seed liquid as you heat it to precipitate the scale in the “fluid” instead of on the heat transfer surfaces. You can also keep the fluid below the scaling index by selecting systems that run at lower temperatures, or by using vacuum, among other methods. Seeding compounds and techniques are selected according to the composition of the concentrate and the type of scale likely to deposit under the circumstances.
The present method avoids the use of conventional heat exchangers in the dirty fluids to a great extent, recycles thermal energy wherever feasible, and promotes scale-free evaporation to obtain useful fresh water without undue energy use. As will be seen below, a cavitation device, or SPR, is a versatile device for converting shaft horsepower into heat without using a conventional heat exchange surface. The SPR can be used in various heat and energy saving systems to realize cost savings in many ways while making copious amounts of useful fresh water and concentrating otherwise used wastep fluids so they can be economically reused or disposed of.
This invention dewaters dilute and contaminated solutions and slurries—industrial fluids—by passing them through a cavitation device which generates shock waves to heat the fluid and facilitate the removal of moisture, thereby reducing the volume of wastep material for disposal. Preferably the cavitation device is one manufactured and sold by Hydro Dynamics, Inc., of Rome, Ga., most preferably the device described in U.S. Pat. Nos. 5,385,298, 5,957,122 6,627,784 and particularly 5,188,090, all of which are incorporated herein by reference in their entireties. In recent years, Hydro Dynamics, Inc. has adopted the trademark “Shockwave Power Reactor” for its cavitation devices, and we use the term SPR herein to describe the products of this company and other cavitation devices that can be used in our invention. The cavitation device will heat the fluid without accumulating any scale. The reason is that the generation of thermal energy takes place within the fluid and not on a heat exchange surface.
Definition: We use the term “cavitation device,” or “SPR,” to mean and include any device which will impart thermal energy to flowing liquid by causing bubbles or pockets of partial vacuum to form within the liquid it processes, the bubbles or pockets of partial vacuum being quickly imploded and filled by the flowing liquid. The bubbles or pockets of partial vacuum have also been described as areas within the liquid which have reached the vapor pressure of the liquid. The turbulence and/or impact, which may be called a shock wave, caused by the implosion imparts thermal energy to the liquid, which, in the case of water, may readily reach boiling temperatures. The bubbles or pockets of partial vacuum are typically created by flowing the liquid through narrow passages which present side depressions, cavities, pockets, apertures, or dead-end holes to the flowing liquid; hence the term “cavitation effect” is frequently applied, and devices known as “cavitation pumps” or “cavitation regenerators” are included in our definition. Steam generated in the cavitation device can be separated from the remaining, now concentrated, water and/or other liquid which frequently will include significant quantities of solids small enough to pass through the reactor.
The term “cavitation device” includes not only all the devices described in the above itemized U.S. Pat. Nos. 5,385,298, 5,957,122 6,627,784 and 5,188,090 but also any of the devices described by Sajewski in U.S. Pat. Nos. 5,183,513, 5,184,576, and 5,239,948, Wyszomirski in U.S. Pat. No. 3,198,191, Selivanov in U.S. Pat. No. 6,016,798, Thoma in U.S. Pat. Nos. 7,089,886, 6,976,486, 6,959,669, 6,910,448, and 6,823,820, Crosta et al in U.S. Pat. No. 6,595,759, Giebeler et al in U.S. Pat. Nos. 5,931,153 and 6,164,274, Huffman in U.S. Pat. No. 5,419,306, Archibald et al in U.S. Pat. No. 6,596,178 and other similar devices which employ a shearing effect between two close surfaces, at least one of which is moving, such as a rotor, and/or at least one of which has cavities of various designs in its surface as explained above.
The solution or slurry is increased in temperature in the SPR and then passed to a next step either for utilizing the heat energy of the fluid or to enhance the efficiency of its vaporization. The vapor or steam associated with the heated fluid can be used, for example, to operate a steam turbine or steam engine, or it can be subjected to recompression to make its heat energy readily available for reuse, or it can be passed through a membrane to enhance the efficiency of vaporization, or simply passed to a cooling tower.
The fluid heated by the SPR, or a portion of it, can be immediately recycled to the SPR to heat it further. Vapor or steam generated in the SPR can be separated to be passed to one of the above-mentioned steps, before, after, or at the same time as the remaining fluid.
Our invention includes the optional step of filtering the fluid before it enters the SPR, or after it is concentrated by the SPR. Because the SPR is able to handle large proportions of solids in the fluid it processes, our invention enables the postponement of filtration until after the fluid is reduced in water content by passing through the SPR to heat it and facilitate removal of vapor; filters and the filtration process can therefore be engineered to handle smaller volumes of liquid with higher concentrations of solids.
In another aspect, our invention includes a method of processing a used oil well fluid comprising optionally filtering the used oil well fluid, passing the used oil well fluid through a heat exchanger utilizing wastep heat from a power source such as the exhaust of a Diesel engine, powering a cavitation device with the power source, passing the oil well fluid through the cavitation device to increase the temperature thereof, optionally recycling at least some of the used oil well fluid through the cavitation device to further increase the temperature of the used oil well fluid, passing the used oil well fluid into a flash tank to separate steam and vapor from the used oil well fluid and to obtain a concentrated fluid, removing at least a portion of the concentrated fluid from the flash tank, and reusing the at least a portion of the concentrated fluid in an oil well. The use of a Diesel engine is not essential; the cavitation device may be powered by any more or less equivalent source of mechanical energy, such as a common internal combustion engine, a steam engine, an electric motor, or the like. Wastep heat from any of these, either in an exhaust gas or otherwise, may be utilized in a known manner to warm the oil well fluid before or after passing it through the SPR.
While the SPR is quite capable of elevating the temperature of an aqueous solution or slurry to the boiling point of water (at atmospheric pressure) or higher, it is not essential in our process for it to do so, as the flash tank, membrane, or other vapor recovery device may be operated under a vacuum to draw off vapors at temperatures below the boiling point at atmospheric pressure.
a and 1b show variations of a cavitation device as utilized in our invention.
In
a and 1b show two slightly different variations, and views, of the cavitation devices sometimes known as a cavitation pump, or a cavitation regenerator, and sometimes referred to herein as an SPR, which we use in our invention to regenerate solutions comprising heavy brine components.
a and 1b are taken from FIGS. 1 and 2 of Griggs U.S. Pat. No. 5,188,090, which is incorporated herein by reference along with related U.S. Pat. Nos. 5,385,298, 5,957,122, and 6,627,784. As explained in the 5,188,090 patent and elsewhere in the referenced patents, liquid is heated in the device without the use of a heat transfer surface, thus avoiding the usual scaling problems common to boilers and distillation apparatus.
A housing 10 in
Another variation which can lend versatility to the SPR is to design the opposing surfaces of housing 10 and rotor 11 to be somewhat conical, and to provide a means for adjusting the position of the rotor within the housing so as to increase or decrease the width of the clearance 12. This can allow for different sizes of solids present in the fluid, to reduce the shearing effect if desired (by increasing the width of clearance 12), to vary the velocity of the rotor as a function of the fluid's viscosity, or for any other reason.
Operation of the SPR (cavitation device) is as follows. A shearing stress is created in the solution as it passes into the narrow clearance 12 between the rotor 11 and the housing 10. This shearing stress causes an increase in temperature. The solution quickly encounters the cavities 17 in the rotor 11, and tends to fill the cavities, but the centrifugal force of the rotation tends to throw the liquid back out of the cavity, which creates a vacuum. The vacuum in the cavities 17 draws liquid back into them, and accordingly “shock waves” are formed as the cavities are constantly filled, emptied and filled again. Small bubbles, some of them microscopic, are formed and imploded. All of this stress on the liquid generates heat which increases the temperature of the liquid dramatically. The design of the SPR ensures that, since the bubble collapse and most of the other stress takes place in the cavities, little or no erosion of the working surfaces of the rotor 11 takes place, and virtually all of the heat generated remains within the liquid.
Temperatures within the cavitation device—of the rotor 11, the housing 10, and the fluid within the clearance spaces 12 between the rotor and the housing—remain substantially constant after the process is begun and while the feed rate and other variables are maintained at the desired values. There is no outside heat source; it is the mechanical energy of the spinning rotor—to some extent friction, as well as the above described cavitation effect—that is converted to heat taken up by the solution and soon removed along with the solution when it is passes through exit 18. The rotor and housing 10, particularly in its interior 20, indeed tend to be lower in temperature than the liquid in clearances 12 and 13. There is little danger of scale formation even with high concentrations of heavy brine components in the solution being processed.
Any solids present in the solution, having dimensions small enough to pass through the clearances 12 and 13 may pass through the SPR unchanged. This may be taken into account when using the reconstituted solution in for oil well purposes. On the other hand, subjecting the water-soluble polymers to the localized cavitation process and heating may break them down, shear them, or otherwise completely destroy them, a favorable outcome for many purposes. The condition known as “fish-eyes,” sometimes caused by the gelling of water-soluble polymers, can be cured by the SPR. These effects will take place in spite of the possible presence of significant amounts of solids.
Concentrated and heavy or dense brines are more liable to crystallize in use than dilute brines, and accordingly their crystallization temperatures are of concern. The crystallization point of a highly salt-laden solution does not imply merely that a small portion of the salts may crystallize out, but that the entire solution will tend to gel or actually solidify, a phenomenon of great concern during the transportation of such solutions or in storage, for example. The ability to concentrate heavy brine components and their ratios to each other in a solution using a cavitation device leads to better control over crystallization temperature and the ability to achieve a good balance between crystallization temperature and density. Complex relationships between the concentrations and ratios of heavy brine component ions and other constituents in the solution rather precisely obtained by our invention means that the crystallization temperature of a completion or workover fluid can be more readily controlled while conserving substantially all of the components available to be saved.
The ability to concentrate heavy brine components content in a solution using a cavitation device also leads to better control over solution density. Relationships between the rather precisely obtained concentrations of heavy brine component ions and other constituents in the solution means that the density of a completion or workover fluid can be more readily matched with the density of the drilling fluid.
Where the fluid treated is a heavy brine containing cesium, it will commonly contain at least 2.5% cesium by weight. Our invention includes a method of treating a hydrocarbon producing formation comprising introducing into the formation through a well an oil well fluid containing at least 2.5% by weight cesium, whereby the fluid becomes diluted so that it contains less than 2.5% cesium by weight, circulating the fluid from the well, and passing at least a portion of the fluid through a cavitation device to remove moisture therefrom and produce a regenerated fluid containing at least 2.5% cesium by weight in the fluid.
Similar percentages may be found in cesium solutions used in mining cesium, and our invention may be quite useful for concentrating cesium solutions in cesium mining.
In FIGS. 2A-D, a dilute solution, slurry or emulsion (hereafter sometimes a fluid) enters in line 32 from the lower left, as depicted. It may come directly from a well, from a hold tank, or indirectly from another industrial fluid source. The SPR (cavitation device) 30 requires a motor or engine to rotate it. Here, a Diesel engine or other power source, designated Mech. Power 40, powers the SPR through shaft 41 and generates hot exhaust gases or other wastep heat, which is/are passed to heat exchanger 42, where the thermal energy of the exhaust gas or other wastep heat is used to heat the incoming fluid in line 32 through a heat exchange surface or other conventional or expedient manner. Optionally the heat exchanger may be bypassed in a line not shown. The incoming fluid continues through line 31 to the SPR 30 which may be any cavitation device described above; for illustrative purposes, it may be substantially as shown in
Supplemental pumps, and various filters, meters and valves, not shown, may be deployed throughout the system of FIGS. 2A-D, as in any of the other system configurations described herein to assure the desired flow rates and pressures, and to direct the fluids in the system to and through the various options described; automatic or manual controls for the valves pumps and other components may also be installed. Likewise, the system may utilize various electric and mechanical power and thermal energy sources available on site to drive pumps and/or assure the evaporation of water from the incoming fluid in line 32. It should be understood that any electric power generated by the system will result in savings in commercial power otherwise available at the site.
Referring now to
a and 4b are flow diagrams showing the use of membranes to enhance evaporation of water in an SPR system. In
In the configuration of
This application claims the full benefit of copending application Ser. No. 11/352,889, filed Feb. 13, 2006, which in turn claims the benefit of provisional application 60/652,549 filed Feb. 14, 2005 and 60/652,711 filed Feb. 14, 2005.
| Number | Date | Country | |
|---|---|---|---|
| 60652549 | Feb 2005 | US | |
| 60652711 | Feb 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11352889 | Feb 2006 | US |
| Child | 11705300 | Feb 2007 | US |
