US 20060048920 A1
The invention relates to gaseous sources from which to reclaim energy using a pressurized direct contact heat exchanger, and in particular, those sources containing a condensable vapor. While the main applications involve water as the condensable vapor, the process is applicable to other vapors, e.g. those in the chemical and petroleum industries where various organic solvents are used. The reclaimed energy can be in the form of a hot fluid, process steam and or electricity. It has particular application to: a pressure combustion furnace and the DOE's Clean Coal Technology; the combustion of wet fuels (biomass, peat); pulp & paper; electrolysis of alumina or water; detoxidation, thermal depolymerization, enhanced oil recovery (and sequestering of carbon dioxide), phytotechnology,
1. A process for continuously reclaiming any additional energy residing in hot pressurized non-condensable gases containing a condensable vapor, produced when processing material, and converting said energy into a more useful form, comprising the steps of:
a) providing a source from which to reclaim said additional energy from said gases continuously being produced within and or emanating from the source, and if necessary, converting the source to a higher pressure, so that hot pressurized gases are produced;
b) continuously bringing the pressurized gases into intimate contact with a cooler liquid, in a pressurized direct-contact heat exchanger, a vertical vessel consisting of various sections, including a hot well, where the gases will enter at the bottom, flow counter-current to a flow of the cooler liquid and where any condensable vapor will condense and the gases will become drier, and leave at the top where the cooler liquid enters, said exchanger being divided into several areas; a first area being where any evaporative and heating property of the gases could be used to dry materials, a second area where part of the condensing and heating property of any vapor in the gas will be utilized to heat the cooler liquid to the highest temperature it could have when in equilibrium with the gases at the given pressure and thereby cool the gases as well as allowing heated liquid and condensed vapor to collect in the hot well within the area while still maintaining the highest possible hot well temperature, and continuously removing liquid from the hot well as reclaimed energy for further use or alternatively, continuously removing the liquid in the hot well and sending it to a flash chamber to produce vapor with the cooler flashed liquor reintroduced into said second area to cool further gases; and a third area wherein the gas and liquid will continue to progressively exchange heat content and supply heated liquid to the hot well, until the gas approaches the temperature of the cool liquid entering at the top;
c) continuously replenishing the cool liquid entering at the top of the exchanger
d) continuously removing the cooled gases from the top of the exchanger as reclaimed energy for further use.
2. The process of claim I comprising the steps of continuously removing heated liquid from the hot well and flash evaporating it in a flash chamber at a pressure lower than the pressure corresponding to the equilibrium or hot well temperature to thereby (1) convert some of the water in the liquid into steam and (2) cool the liquid to a temperature corresponding to the pressure of the flashed steam and allow it to collect in a sump in the flash chamber, continuously removing cooled liquid from the flash chamber and re-introducing it to the direct contact heat exchange section; at a point in the second area where the gas in the area is at about the same temperature as that of the liquid in the sump, so as to cool further gases, and where the gas and cooled liquid will progressively exchange heat content, until the gas as it cools approaches the temperature of the liquid from the flash chamber; continuously removing the flashed steam from the flash chamber for further use;
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The present application is a continuation-in-part of application Ser. No. 10/780,199 filed Jul. 9, 2004.
The invention relates to gaseous sources from which to reclaim energy using a pressurized direct contact heat exchanger. In particular, those sources containing a condensable vapor While the main applications involve water as the condensable vapor, the process is applicable to other vapors, e.g. those in the chemical and petroleum industries where various organic solvents are used.
The reclaimed energy-can be in the form of a hot fluid, process steam and/or electricity. It has particular application to: a pressure combustion furnace and to DOE's Clean Coal Technology; the combustion of wet fuels (biomass, peat); pulp &paper; electrolysis of alumina or water; wet oxidation, thermal depolymerization, enhanced oil recovery (and sequestering of carbon dioxide), phytotechnology,
If the source is not already under pressure, the invention converts it to a higher pressure.
Present processes release large volumes of gas into the atmosphere, resulting in a loss of energy, especially the latent heat of any condensable vapor, resulting in low thermal efficiencies.
While various direct contact heat exchange systems have been proposed to recover this energy, all of them operate at close to atmospheric pressure and recover mainly the sensible heat and the temperature of the recovered fluids are near or below the boiling point of the fluid at the recovered pressure.
U.S. Pat. Nos. 3,920,505 and 4,079,585 are previous disclosures relating to the recovery of waste sulfite liquors using a pressurized heat exchange process.
The basis embodiment of the invention comprises:
(a) providing a source from which to reclaim any additional energy from pressurized gases, continuously being produced within and/or emanating from the source, and if necessary, converting the source to a higher pressure, so that pressurized gases are produced;
(b) continuously bringing the pressurized gases into intimate contact with a cooler liquid, in a pressurized direct-contact heat exchanger, a vertical vessel consisting of various sections, including a hot well, where the gases will enter at the bottom, flow counter-current to a flow of the cooler liquid and where any condensable vapor will condense and the gases will become drier, and leave at the top where the cooler liquid enters, said exchanger being capable of being divided into several areas/sections; the first area being where any evaporative and heating property of the gases could be used to dry materials, a second area where part of the condensing and heating property of any vapor in the gas will be utilized to heat the cooler liquid to the highest temperature it could have when in equilibrium with the gases at the given pressure, and thereby cool the gases; as well as allow heated liquid and condensed vapor to collect in the hot well within the area, while still maintaining the highest possible hot well temperature, and continuously removing liquid from the hot well as reclaimed energy for further use or alternatively, continuously removing the liquid in the hot well and sending it to a flash chamber to produce vapor and the cooler flashed liquor reintroduced into this second area to cool further gases; and the third area is where the gas and liquid will continue to progressively exchange heat content and supply heated liquid to the hot well, until the gas approaches the temperature of the cool liquid entering at the top.
(c) continuously replenishing the cool liquid entering at the top of the exchanger
(d) continuously removing the cooled gases from the top of the exchanger as reclaimed energy for further use.
Other embodiments are listed below
To avoid complexity, valving and other obvious operations are not always shown, or labeled e.g. exhaust steam from steam turbines could go to a condenser; the gas compressor in
The following drawings are schematic representations of the various embodiments/applications of the present invention:
The following embodiments are process sequences that provide a wide range of choice to fit a wide variety of circumstances, applications and available technologies. Because of the wide range of process variables involved and technologies to choose from it is nearly impossible to describe in any detail how a particular embodiment is carried out. For example, while many of the embodiments below will use water as the condensable vapor it will be understood that wherever feasible there embodiments can be used for other condensable vapors, such as the many organic solvents used in the chemical industry. In most cases computer simulation will be required to balance the various variables such as the rate of recirculation of the hot well liquid through the flash chamber; the cool liquid supply; the excess liquid removal, which can be done at the appropriate location: etc.
The embodiments as illustrated and described is such as to obtain maximum thermal efficiency, noting that, the higher the pressure and the lower the temperature of the gas leaving the pressurized direct contact heat exchanger, the lower the vapor content of the exit gases and the higher the thermal efficiency. Embodiments involving lower pressures are also being included, see
The gases can contain two components of heat, sensible heat and latent heat. If there is little or no condensable vapor in the gases, if will essentially be all sensible heat and the cooler liquid will extract heat and become hotter. If there is condensable vapor the cooler liquid will condense the vapor and the resulting heat will be absorbed by the cooler liquid and become hotter
Examples of further use for the condensed vapor in the hot well are numerous and well known in the trades in which a particular condensed vapor is involved, and which will also depend on the temperature of the condensed vapor in the hot well, which is determined by the pressure of the hot gases and the vapor pressure of the condensed liquid.
For example, if the condensed vapor is water and the pressure of the gases in the heat exchanger is 200 psia the temperature in the hot well will be somewhat below 195 C (382 F) depending on the efficiency of the heat exchange, Similarly, further use of the gases will depend on the type of non condensable gas involved and the dryness of the gas will depend on the pressure and temperature of the exiting gases, i.e. Henry's Law of Partial Pressures. For example, using the following equation for gas saturated with water vapor at t° F.:
These higher pressures are required when higher hot well temperature are desired and/or when the invention is used in connection with a flash evaporator/chamber to produce fairly high steam pressures and to concentrate effluents. The lower end of pressure spectrum, e.g. in the range of that produced by a rotary blower, can be used to reclaim the energy as illustrated below in
The cool dry pressurized gases are source of energy for the production of electricity using a turbo-expander connected to a generator.
Where water is the condensed liquid in the hot well it could obviously be used to heat large living and business complexes especially in remote places. Further use for the cool gases and water in the hot well are described in the various embodiments below. While the various areas or zones of the pressurized direct contact exchanger are some times shown in one chamber, they could be located in separate chambers or sections Here the hot well is shown near the top of lower zone so as to illustrate that the area below it could be used to dry solid materials. Normally it would be near the bottom.
Various technologies are available in determining how the chambers are constructed and the best type of heat exchanger to use, while maintaining maximum heat exchange and minimum pressure drop, e.g. the Field gas scrubber; bubble columns; packed towers; turbo-gas absorber; cascades; collecting the cooler liquid at any point in the pressurized exchanger and recycling it in the exchanger until its temperature approaches that of the gas; etc. While the cooling liquid introduced into various areas is shown as entering at one point, depending on the mixing technology used, it could be introduced at various points in each area or section. To increase the dwell time of contact between the gas and the cooler liquid, a portion of the descending liquid may be withdrawn from the top section and re-circulated back through the gas This procedure may be repeated at any place in the exchanger where it seems appropriate. The top location could be the best place to remove any liquid in order to maintain a water balance as its heat content would be the least.
A particular heat exchange process used for gases at atmospheric pressure is the “Fluidized Spray Tower” technology, recently developed by William D. Carson and disclosed in U.S. patent application 20030015809). The disclosure of which is hereby incorporated by reference, as embodiments of that Process, designed to recover heat from non-condensable gases containing a condensable vapor, are directly pertinent to this invention, designed to recover heat from gases at pressures and temperatures greatly higher than presently attempted.
As illustrated schematically in
The whole chamber or any one of the separate chambers could be located within the confines of the Source depending on the process producing the hot gases and other factors. Further elaboration is given in various embodiments below.
Existing high pressure process 'sources include: (a) pressurized combustion projects in the Clean Coal Technology Program sponsored by the US Department of Energy, where pressures up towards 250 psia are reached using combustion furnaces developed by such firms as Foster Wheeler, ABB (now Alstom Power), & Babcock & Wilcox; (b) high pressure char oxidation; processing of wood in digesters; etc.
Combustion/incineration of materials that produce water vapor, e.g. wet combustibles. While some emphasis is on biomass fuels, the process could have application to the combustion of (a) solid/liquid fossils fuels; (b) fuels intermediate between the two i.e. lignite (brown coal), peat, etc, where the high moisture content is a deterrent to their use; (c) Diverse fuels, such as Tire Derived Fuel (TDF), and various sludges, etc. (2) Diverse processes such the smelting of ores; wet oxidation; chemical, electrochemical, metallurgical processes (blast furnaces), and intermediary operations such as: drying; stripping, extraction; boiling and the like.
It is also possible, to collect other non-condensable gases containing water vapor (which are outside of the source) and turbo-compressing them to a pressure sufficient to introduce them into the source process. For example, in the above paragraph the air-steam mixtures could be turbo-compressed and introduced into a combustion furnace. Other such mixtures include naturally occurring ones such as fog banks, low clouds, mists, steam eruptions from the earth, etc.
In most of the following embodiments, water will be the “condensed vapor” used in the examples. Embodiments involving the flash evaporator will generally also be used along with the use of low pressure steam turbines but it is understood that wherever there is need to increase the thermal efficiency of the turbines the above embodiments shown in FIGS. C & D can be used.
The following embodiment involves expanding the alternative use of the hot well liquid of the main embodiment as follows:
continuously removing heated liquid from the hot well and flash evaporating it in a flash chamber at a pressure lower than the pressure corresponding to the equilibrium or hot well temperature to thereby (1) convert some of the water in the liquid into steam and (2) cool the liquid to a temperature corresponding to the pressure of the flashed steam and allow it to collect in a sump in the flash chamber, continuously removing cooled liquid from the flash chamber and re-introducing it to the direct contact heat exchange section; at a point in the second area where the gas in the area is at about the same temperature as that of the liquid in the sump, so as to cool further gases, and where the gas and cooled liquid will progressively exchange heat content, until the gas as it cools approaches the temperature of the liquid from the flash chamber; continuously removing the flashed steam from the flash chamber for further use;
This further embodiment is illustrated in
As mentioned above the temperature of the water in the hot well will depend on the pressure in the exchanger and correspondingly this will determine the pressure of the steam from the flash chamber. As mentioned, at 200 psia the temperature in the hot well will be somewhat below 195 C (382 F) so this could produce steam pressures in a range somewhere below 200 psia depending on the flashing potential used and several other factors, including the enthalpy of the gases,
It should be noted that the pressurized direct contact heat exchanger in combination with a flash chamber/evaporator can concentrate cool effluents containing solids, used to cool the gases, which if combustible can be burnt in a combustion furnace. Examples are given below Another feature of this combination, is that when the efficiency of lower pressure steam turbines has been significantly increased, it will not be necessary to use the embodiments illustrated in
Which of the above embodiments is chosen could depend on which is less expensive approach.
As previously mentioned, a further arrangement is where, if the pressure and temperature of the hot gases from the source process are high enough, after removing any particulates, they are passed through a gas turbine connected to a generator to produce electricity, before being sent to the pressurized direct contact heat exchanger. This is particularly advantageous for a combustion process where high gas temperatures are achievable as illustrated in
Oxygen, if required in any of the embodiments, is supplied by a source under a pressure greater than the pressure required for the source of the pressurized hot gases This makes the process more efficient by eliminating the need for a turbine compressor. The electrolysis of water or steam is one such source, where it is more efficient at the higher pressures, with pressurized hydrogen as a valuable by-product This is illustrated in
By using cool liquids, containing dissolved or suspended materials as the cooling liquid, the liquid can be concentrated by the recycling of the liquid through the pressurized direct contact heat exchanger and flash evaporator. Once the concentration of the materials in the circulating liquor reaches the desired level, a portion can be removed at a rate that will prevent further concentration.
If appropriate, the liquid may be used in the source process, e.g. where that process is one of combustion and the material in the liquid is combustible. This is illustrated in
Other examples would be (a) the desalination of salt water, the liquor would provide a source of salt and the condensed steam a source of salt-free water suitable for irrigation; (b) concentration of dilute sugar sources, i.e. cane, beet and maple sugars, where any residues or forest biomass can be combusted under pressure to produce the hot gases; water associated with oil from the wells (producer water) when separated from the oil can serve as the cool liquid and when concentrated can be added to the oil and burnt and the noncombustible pollutants removed in the ash for proper disposal; etc.
It is also possible that the first area of step (b) in the embodiment of
Undesirable solids and/or gases present in the hot gases can be removed in the heat exchanger by maintaining the circulating liquid alkaline for acidic gases and acidic for alkaline gases. The substances so formed can then be concentrated and removed from the flash evaporator (see above).
This could allow greater use of fossil fuels containing a high sulphur content. If the solids/gases are very soluble in the water, they could be put through a scrubbing chamber prior to the pressurized direct contact heat exchanger, were a minimum of liquid could reduce their concentration.
In certain applications, it is desirable to minimize the presence of the non-condensables in the source process, e.g. in the pressurized thermomechanical pulping of wood chips, by presteaming the chips prior to their entering the refiner.
If the steam from the flash evaporator is unsuitable for a particular use, or cannot be cleaned by conventional means, it is passed through a reboiler for further use.
As illustrated in
Alternatively, the two pipes could consist of concentric inner and outer pipes, with the steam flowing down the inner pipe to melt the hydrate, which will flow up the outer concentric pipe which is wide enough to trap the methane and in which the pressure is less than that of the liberated methane. Some of the methane could be used in a conventional boiler to produce the steam and the water supplied from the hot well. The end product would be a pressurized, substantially dry methane gas.
This could also be applicable to number of fossil fuels, e.g. unmineable, gassy coal beds containing methane; wells of natural gases, volatile oils, etc after the wells have been somewhat depleted; where the steam will act as a sweep gas.
A collector receives air-steam emissions from the paper and pulp mill, especially those from the drier section of the paper machines (other sources not indicated include those from thermomechanical pulping processes). This air-steam mixture, monitored for the correct amount of air required for combustion, is passed through a turbine compressor where it is compressed to a pressure high enough for the process to generate a steam pressure suitable for the dryers of the papermachine, as well as operate a gas turbine e.g. 250 psia and higher. The compressed air-steam mixture goes to the pressure combustion furnace where combustible wet fuels are burnt to produce hot flue gases. Auxiliary fuel, oil or gas, can be added to the hot gases and burnt to maintain uniform combustion and an optimum temperature for the gas turbine. (see above)
These hot gases are passed through a particulate remover and a gas turbine and then through a first section or area of the pressurized direct contact heat exchanger, a drier, which dries biomass material, e.g. forest waste and bark including, liquid concentrate from the flash evaporator, to a moisture content amenable to combustion in the pressure combustion furnace. From the drier the flue gases pass to the main second section or area of the pressurized direct contact heat exchanger a scrubber, where they come into intimate contact with a liquid concentrate, containing dissolved and suspended solids from paper & pulp effluents. In applications where only an effluent concentrate is to be combusted or the wet fuels are dry enough to combust, the drier would be omitted and the flue gases would pass directly to the pressurized direct contact heat exchanger. The above concentrate would be generated in the initial start-up of the process as the dilute effluent is concentrated in the flash evaporator.
By continuously removing the heated concentrate and evaporating it in the flash evaporator at a pressure lower than that corresponding to the equilibrium or hot well temperature, so as to (a) convert some of the water in the concentrate into steam, (b) further concentrate the liquid, and (c) cool the concentrate to a temperature lower than the hot well temperature, and then returning the cooled concentrate from the flash evaporator to be reheated in the pressurized direct contact heat exchanger; and removing the steam from the flash evaporator, much of the heat content of the flue gases is converted into process steam.
The saturated flue gases from the main pressurized direct contact heat exchanger, after they are cooled to approximately the temperature of the liquid concentrate from the evaporator, are passed through the last section or area of the pressurized direct contact heat exchanger to come into intimate contact with cool dilute effluent to further cool the flue gases and preheat the effluent;
Thus depending on the temperature of the entering effluent and the efficiency of the pressurized direct contact heat exchanger heater, if the pressure of the flue gases is around 250 psia the water content in the flue gases could be approximately 0.10 lbs per lb of dry flue gas, which is that of the water content of most ambient air, and the thermal efficiency of the process could approach 90% depending on other factors.
Then by continuously removing some of the heated concentrate and adding the required preheated dilute effluent, the proper liquid concentration and balance in the system can be maintained.
The cooled flue gases from the pressurized direct contact heat exchanger heater are passed through a turbine expander to recover some of remaining enthalpy, which is used to compress the air-steam mixture. If necessary they can be put through a particulate remover before going through the turbine expander. Any make-up power for the compression can be supplied by a motor or, while not shown in the drawing, the cooled flue gases can be passed through a combustion chamber in which oil or gas can be burnt to heat the gases to the required temperature before they pass through a turbine expander. (See the above embodiment) Any excess power can used to generate electrical energy by Arranging for the motor to also act as a generator.
To remove any acidic gases from the flue gases, alkaline substances can be added to the liquor circulating in the pressurized direct contact heat exchanger. By a proper choice of substances these will reappear in the ash being removed from the furnace, a portion of which may then be extracted using hot dilute effluent and returned to the pressurized direct contact heat exchanger.
The rest of the drawing illustrates how the water from effluents and the steam in the emissions from the paper and pulp mill is recycled back to mill. The steam from the flash evaporator if necessary is passed through a particular remover or a reboiler and then sent back to the paper machine dryers, or some used in the pulp mill. Any excess steam can be used to generate electrical energy using condensing steam turbines. The condensate from the dryers is used as clean make-up water at the wet end of the paper machine. This water reappears again in the white waters from the wet end which are sent to a fiber recovery system, from which they appear in the effluents from that system and are sent to the effluent collector, where they join effluents from the pulp mill. Condensate from the steam turbines can be used similarly in the paper & pulp mill where it will return via the effluents from the mill. To increase the efficiency of the steam turbines the steam from the evaporator can be processed as illustrated in
In a further embodiment energy can be removed from the pressurized direct contact heat exchanger for various purposes, and the resulting cooled liquid returned to the pressurized direct contact heat exchanger to be reheated. For example, a primary flash evaporator produces steam at the highest possible pressure level, the flashed liquid from the primary is then flashed in a secondary flash evaporator to produce steam at a lower level, if desired this sequence could be continued or, at any stage, the flashed liquid could be used to indirectly heat other media e.g. hot water heating of a building, with the final cooler liquid returned to the pressurized direct contact heat exchanger for re-heating. Similarly, by subdividing the hot well liquid and liquid after flashing and using several independent circulating systems, the rates of circulation, which may depend on the rate of steam production, are not inflexibly tied in with rates and methods of cooling the combustion hot gases.
In an embodiment the cooled gases from the top of zone are cooled further, in order to reclaim further latent heat, by bringing them into indirect contact with the cooler gases between expansion stages in the gas expander. This is an example of how inter-stage-cooling and inter-stage-heating could be practiced in a counter-current or parallel arrangement.
One can be combine various embodiments wherein the electricity produced is one of direct current which is then fed directly to the electrolysis of water, thereby increasing the efficiency of the overall process. This can also apply to any electricity produced in, steps (e) & (g). Similarly, in the case of the electrolysis of steam, the process can supply the direct current as well as the steam as illustrated in
In some arrangements, advantages of other operations can be made use of in the pressurized direct contact heat exchanger process. For example, transportation of materials by pipeline can often be less expensive than that by land or air. Thus, after the appropriate comminution of the material and its suspension in water, it can be pumped to the primary site, where the wetted material is not a problem and the excess water can be used to cool the gases in pressurized direct contact heat exchanger and any dissolved/suspended material in the water concentrated in the flash evaporator. This could be very useful for pressure combustion processes, where the combustible material (e.g. coal, peat, and various biomasses) can be transported to the combustion site by pipeline.
While the pressurized indirect contact heat exchanger is shown as a separate chamber outside of the source, it could be located within the confines of the source depending on the process producing the hot pressurized gases. Where the source is a combustion process, the pressurized indirect contact heat exchanger could consist of tube banks located within the combustion chamber.
A pressurized indirect contact heat exchanger can be introduced into any one of the above embodiments depending on the desired outcome.
In certain circumstances it may be possible to maximize the thermal efficiency further by combining both gas and steam turbine technologies with the pressurized direct contact heat exchanger Process, by extracting some of the energy first in a gas turbine, then further energy in a pressurized indirect contact heat exchanger using high pressure steam turbines (as shown in the above) and finally the remaining energy in a pressurized direct contact heat exchanger using the steam generated there either as process and/or in lower pressure steam turbines. Where the generation of electrical energy is the prime objective, this embodiment could offer the highest thermal efficiency. This could be the case for generation of electricity from coal, especially high sulphur coils. (See embodiment above)
Another application involves coal bed methane and the sequestering of carbon dioxide, where unmineable, gassy coal beds are swept with pressurized gases containing carbon dioxide which releases the methane and traps the carbon dioxide. The gases containing carbon dioxide are also effective in increasing oil recovery, by reducing its viscosity and providing a driving force towards the wells The addition of water/steam improves the sweep efficiency and the water can be recovered in the pressurized direct contact heat exchanger.
In these applications, by using the already pressurized gases from the pressurized direct contact heat exchanger the cost of the pressurization of the gases is avoided. In this technology, while one objective is the removal of the polluting carbon dioxide, in other situations nitrogen is also used to sweep the methane from the coal, so how this application is used could depend on the proportion of carbon dioxide and nitrogen in the gases from the pressurized direct contact heat exchanger as well as the use of the end product of this application, which will be pressurized gases containing methane, e.g. this methane can be used to further heat the hot gases as described above.
The present invention also has application to processes which produce gases which on combustion yield hot pressurized non-condensable gases containing water vapor. The following is an example: a pressurized fluidized-bed gasifier transforms coal into a coal gas containing hydrogen and methane (and carbon monoxide), which after suitable cleaning is combusted with a gas turbine to produce electricity, the hot gases containing water vapor exit the turbine at a pressure sufficient to operate the pressurized direct contact heat exchanger and produce low pressure steam as well as operate a pressurized indirect contact heat exchanger which can supply high pressure steam to the gasifier, as illustrated in an embodiment above, Whether or not the pressurized indirect contact heat exchanger produces steam for high pressure steam turbines is a separate consideration. In present systems, the hot gases from the turbine are sent to a conventional heat recovery steam generator, so that the energy in the water vapor is lost to the atmosphere.
By creating a false ceiling below the canopy or covering over the enclosed space, the oxygen and water vapour, generated by the biomass, being lighter than the carbon dioxide, can be segregated and removed and used in the pressurized direct contact process (and the carbon dioxide recycled to the enclosed space or “greenhouse”).
Some or all of the biomass can be used for combustion/human consumption and any waste from the latter use can be recycled through the combustion cycle.
If air liquefaction is used in place of or in addition to water electrolysis to produce the pressurized oxygen then the nitrogen from the liquefaction can be used along with the hydrogen (in case of the latter) to produce ammonia with can then be used to produce the urea.
A further symbiotic situation is where the above is combined with EnviroMission's (Australian firm) “solar tower” (a vertical wind farm) where a chimney, connected to and surrounded by a shallow, circular, acrylic greenhouse, (7 km in diameter) will provide sufficient draft for the hot air generated by the greenhouse, to power turbo-generators to produce electricity.
A special embodiment is as follows: A fuel cell takes in hydrogen and a gas containing oxygen and generates electricity and expels hot gases laden with water vapour. By operating the fuel cell at elevated pressures and passing the hot gases through the pressurized direct contact heat exchanger the efficiency of the cell is increased If the gases are not hot enough, pressurized combustible gases/oil can be burnt within the gases to increase their temperature and consume any remaining oxygen or they can be heated by any of the methods described above.
Possibly combining this with pressurized water electrolysis other efficiencies might develop. See below. If only hydrogen & oxygen are used, any residual hydrogen & oxygen could also be recycled back to the fuel cells, rather than put through a turbine expander to produce electricity. If air is used in place of the oxygen the energy in the residual pressurized nitrogen would be recovered in the turbine expander.
Other embodiments involve electrochemical processes where the “overvoltage”, etc generates heat, which is generally dissipated, thereby decreasing the efficiency of the process.
One such embodiment involving electrolysis is illustrated in
It should be noted that the proportion of carbon monoxide in the hot gas depends on the alumina content in the hot bath. By carefully controlling this content (e.g. keeping track of the cell voltage) this proportion can be kept to a maximum and the carbon dioxide to a minimum and the carbon monoxide bleed off.
A further embodiment involving electrolysis is that of the electrolysis of water, which was mentioned above in a general way in a symbiotic association with other processes.
In particular it relates to those hydrogen-oxygen generators that operate at relatively high pressures, e.g. high pressure water electrolysis presently allow the generation of hydrogen at pressures up to 5 MPa. (750 psi). One such unit under development/available is made by GHW (Gesellschaft fur Hochleistungswasserelektroly seure). Generally these operate at normal temperatures, however by a similar choice of material, these can be made to operate at fairly high temperatures at was done in the Cerametec process mentioned below.
Where necessary present oxygen-hydrogen generators are cooled to keep the temperature below 100 C (e.g. 65-60 C) mainly to avoid the formation of too much water vapor. In the present embodiment, since the temperature is much higher, a fair amount of steam with pass along with the gases, as illustrated in
Most of the rest of
When the above embodiment is combined with pressure combustion (see embodiment above) only one stream of gas would be involved as illustrated in
It should be noted that the above embodiment,
Further examples of symbiosis are illustrated in
(a) Here the process in
(b) A further example is Phytotechnology (
A further embodiment involves the general processing of substances in a reactor under high pressure as illustrated in
Any gas produced in the reactor can be separated from the aqueous medium in a special separator chamber, as shown in
An example of a reactor process is that of wet oxidation (combustion), where substantial steam is present with the gas that is produced, and the heat content of the gas and steam is recovered more efficiently, by passing the cool make-up water (e.g. condensed steam) through the pressurized heat exchanger. A dry cool gas is also produced, the energy of which is recovered in a turbine expander.
Alternatively, if the gas is pressurized carbon dioxide (a) it could be used for oil enhancement as shown in
Reactants include compressed air or pressurized oxygen and any oxidizable material, including inorganics, with a COD. Examples are: (a) Caustic streams: refinery spent caustic and soda pulping liquor; (b) Dangerous, obnoxious and toxic substances: effluents containing cyanide, phenols, etc. (c) Waste biological sludges.
Which of the embodiment in
The embodiment illustrated in
The following embodiment illustrated in
Here the hot water could be sent to a boiler (possibly located in the Source) to produce very high pressure, high temperature steam for process or for generating electricity using highly efficient steam turbines. If cool enough the steam condensate could be recycled back to the pressurized heat exchanger. The hot water could of course be used for other purposes. In terms of Carson's Fluidized Spray Tower illustrated in
The present invention could have particular application to existing high pressure combustion projects in the Clean Coal Technology Program sponsored by the US Department of Energy, (mentioned above).
(a) In various projects, a water paste of coal and limestone and compressed air are fed to pressurized circulating fluidized-bed combustor where combustion takes place at a pressure of about 200 psig, the hot flue gas pass through equipment to remove the particulates, etc, then through a gas turbine and the heat in the gas from the turbine is recovered in a conventional steam generator, in which case the latent heat of any water vapor in the final flue gas is lost.
Various details are left out since they vary from one type of process to the other. Since the limestone removes about 95% of the sulfur and the ash content in the hot gas is low, the hot well water should be suitable to produce the high pressure high temperature steam for the steam turbines. Here (
(b) In another series of projects, a pressurized gasifer is supplied with steam, oxygen, and a water paste of coal and limestone to produce a fuel gas rich in hydrogen and carbon monoxide, which is cleaned and used to fire a gas turbine. Again it appears that the latent heat of any water vapor in the final flue gas is lost, which could be high since hydrogen is one of fuel gas components.
As a further example of symbiosis, a high pressure electrolysis of water plant (see
In another embodiment,
Here the process is concerned with the present technique of using high pressure steam to lower the viscosity of the bitumen in the sands so that it will flow towards a well which will raise it above the ground. In the present embodiment care is taken to collect as much steam and gas as possible emanting from the oil well and compress it to the same gas pressure as that for the gases coming from a pressurized combustion furnace, which will also contain water vapor. Both gases are combined and processed through the pressurized direct contact heat exchanger to recover the heat energy in the gases as well as produce very hot well water which is used to make the high pressure steam in a boiler in the pressurized furnace.
This high pressure steam can also be used to produce electricity with which to operate the system, using high efficiency condensing steam turbines. The condensate can then be used to cool the gases in the heat exchanger. Where it is introduced could depend on its temperature. As indicated the coolest water available is introduced at the top of the heat exchanger and its temperature will determine the thermal efficiency of the process.
Depending on the type of fuel used to fire the furnace, it may be necessary to clean the gases before they go to the heat exchanger so as to ensure that hot well water is suitable for the production of the high pressure steam. The gas cleaning technology is well known and used in the Clean Coal Program sponsored by the US Department of Energy. To that end it might be desirable to mix limestone with the fuel so as trap any sulfur compound in the fuel so that they will exit with the ash and not the gas steam. The pressure in the furnace will depend on the temperature that is desired for the hot well water, as well as the degree of thermal efficiency desired, as was explained above.
The present invention can also be used to break the bitumen down into various fractions using the any of the above embodiments, one of which is illustrated in
As an alternative to the above the gas and steam from the oil well can be processed as described in
Other embodiments involving lower pressures are situations where drying (and boiling) is involved e.g. web drying. Here the drying could be accelerated by subjecting the web to a mild vacuum using either the suction side of rotary blower or a vacuum pump and the steam and any entrained air could go a pressurized direct contact heat exchanger, such as the fluidized spray tower mentioned above, where some of the steam would be condensed using the water in the hot well of the second heat exchanger as cooling water. The water in the hot well can be sent to a high pressure boiler to produce high pressure steam.
The remaining steam containing low amounts of air can then to connected to the suction side of a high pressure water pump being fed cooler water e.g. the condensate from the steam turbines and then sent to a pressurized direct contact heat exchanger as disclosed above in connection with
This embodiment can be very effectively used with a new paper technology referred to a Impulse Drying where a very hot roll is heated by either very hot steam or a gas flame or magnetic induction This is illustrated in
While alternatively a low pressure chamber could be used, the above low vacuum chamber would seem more advantageous.
It should be noted to avoid cleaning gases using expensive equipment one can by using an indirect heat exchanger use the unclean hot well water to heat the condensate from the steam turbines and send this now clean hot water to the boiler to make high pressure steam.
The preceding description of the invention is merely exemplary and is not intended to limit the scope of the present invention in any way thereof.