NEAR ZERO EMISSIONS PRODUCTION OF CLEAN HIGH PRESSURE STEAM

Abstract

Substantially pure high pressure steam is produced within a high pressure heat exchanger. Heat for the high pressure heat exchanger is provided from an outlet of an oxy-fuel combustion gas generator which discharges a steam/CO2 mixture at high pressure and temperature. The gas generator combusts oxygen and hydrocarbon fuel and mixes with water which can include contaminates therein in the form of dissolved solids or hydrocarbons. A separator is typically provided downstream of the gas generator and upstream of the heat exchanger and the steam/CO2 mixture is discharged from the gas generator at saturation temperature. A water fraction of the steam/CO2 mixture is discharged from the separator along with dissolved solids in concentrated brine form. The water heated into steam by the heat exchanger can be at least partially water separated within a condenser downstream of the heat exchanger.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit under Title 35, United States Code §119(e) of U.S. Provisional Application No. 61/710,963 filed on Oct. 8, 2012.

FIELD OF THE INVENTION

The following invention relates to systems for production of high pressure substantially pure steam with heat from combustion of a hydrocarbon fuel. More particularly, this invention relates to production of high pressure steam utilizing combustion of a hydrocarbon fuel with a primarily oxygen stream such that zero emissions or near zero emissions combustion provides the heat to raise the high pressure steam.

BACKGROUND OF THE INVENTION

A variety of different industrial machines and processes are driven by steam. Even when such machinery or processes are configured to tolerate impurities in the steam, such machinery and processes benefit from being driven by steam which is as pure as possible.

Contaminates in the water/steam can include dissolved solids, such as those typically present in waste water; gases such as carbon dioxide which cause the water to be at least mildly acidic; and sea water or other salt water sources which are highly abundant but require or benefit from purification before utilization. Hydrocarbon can also be such a contaminate and might be present in produced water coming out of a hydrocarbon recovery process which utilizes certain amounts of water to liberate the hydrocarbons from a geological formation. Such produced hydrocarbons benefit from having the hydrocarbon fuel components removed therefrom both for beneficial use of the hydrocarbon fuel and to avoid fouling of processes and equipment which would otherwise be able to utilize higher purity steam.

Temperatures at which water boils into steam vary based on the pressure of the water. Thermodynamic efficiencies and hence overall efficiency of various industrial processes are enhanced when steps such as pumping to high pressure occur when the water is in a liquid state and when other steps in industrial processes occur when the water is steam or superheated steam at a temperature greater than the condensing temperature of the steam at the pressure involved. In optimizing a variety of industrial processes and most efficiently operating a variety of steam utilizing machinery, it is desirable that the steam be provided at a high pressure. When referring to high pressure, a pressure of at least ten times standard atmospheric pressure is contemplated, and more typically more than fifty times atmospheric pressure, and extending up to one hundred or more times standard atmospheric pressure. At such higher pressures, the boiling point for water is significantly increased and significant heat is required to boil such high pressure water into steam.

A common prior art element for raising high pressure pure steam is a standard boiler utilized in a variety of different machinery and industrial processes. Such boilers typically first have a feed water pump providing water at an elevated pressure. The elevated pressure water is then fed through high pressure water handling tubes into walls of the boiler which surround a combustion region. Fuel along with air are introduced into this combustion chamber and undergo a combustion reaction with significant production of heat and products of combustion. These products of combustion are routed to a smoke stack and discharged into the atmosphere.

The boiler smoke stack discharges a largest fraction in the form of nitrogen which is present in the air and does not participate in the combustion reaction. Other constituents discharged into the atmosphere include steam, carbon dioxide, oxides of nitrogen, carbon monoxide, volatile organic compounds, ozone and potentially other compounds and pollutants which may have been present in the fuel utilized in the combustion reaction, including oxides of sulphur, mercury, other heavy metals and other toxic substances. The water entered into the boiler is effectively heated into high pressure steam for utilization by downstream processes and machinery.

Such a standard prior art boiler is undesirable for a variety of reasons. First, a supply of substantially pure water is necessitated by typical downstream processes and machinery utilized in the steam. Without such purity, problems encountered include acidity in the water causing corrosion of downstream equipment, dissolved solids in the steam precipitating as the steam is utilized in the machinery or processes and scaling or otherwise fouling of surfaces of downstream equipment, and constituents having different boiling points than steam condensing in portions of the processes or machinery which are suboptimal and decrease performance of the equipment. Further, potentially valuable contaminating constituents in the water, such as hydrocarbon fuels, are not beneficially utilized when they remain as impurities in the water stream entering the boiler.

Second, typical prior art boilers produce significant amounts of atmospheric pollution. Even when extensive countermeasures are taken to clean the exhaust at this smokestack, such countermeasures are expensive and incomplete.

Boilers also require substantially thick walled pipes to withstand the pressure differential between the inside of the high pressure water lines lining the boiler and the outside of these pipes where the combustion reaction is taking place. The thickness of these pipes adds significant cost to the materials which make up the boiler, the labor which goes into manufacture of the boiler, and also decreases a rate of heat transfer through the walls of the pipes when compared to thinner walled pipes which could be utilized if a lesser pressure differential existed between the hot and cold sides of the heat exchanger. Furthermore, when the fuel is combusted in air with the associated pollutants being generated therein, some potential exists for degradation of the surfaces of these thick walled pipes, such as by precipitation of scaling solids onto the relatively cooler pipe walls within the boiler, which scaling would be minimized or not occur if a cleaner combustion reaction were producing the heat for the boiler.

Accordingly, a need exists for better ways to efficiently produce substantially pure high pressure steam for various high pressure utilizing processes and machinery.

SUMMARY OF THE INVENTION

This disclosure defines a new process using pressurized oxy-fuel combustors, steam separators, oxy-fuel reheaters, and pressurized heat exchangers to: (1) produce clean water, (2) clean steam, and (3) a concentrated waste water stream from dirty/produced water supplies such as those resulting from the production of crude oil or bitumen. The resulting clean steam and CO₂ may be used for the production of additional crude oil or bitumen by processes such as steam assisted gravity drain (SAGD) or enhanced oil recovery (EOR) using CO₂ flooding or the steam and CO₂ may be used for other industrial purposes. The disposal of the concentrated waste water steam may be accomplished by injection into a deep saline aquifer, evaporation in a pond with subsequent harvesting and disposal of the solid residue, processing in a crystallizer with subsequent disposal of the solids or further processed to recover useful products.

The overall scheme for producing clean steam and CO₂ from dirty/produced water using high-pressure oxy-fuel combustors, steam separators, oxy-fuel reheaters, and pressurized heat exchangers is depicted in FIG. 1. The oxy-fuel combustor operates on a gaseous fuel, substantially pure O₂ and dirty/produced water. The gaseous fuel may be natural gas or other gaseous fuel composed primarily of light hydrocarbons, CO, CO₂, and/or H₂. The O₂ is normally separated from air using various conventional commercial processes (e.g., cryogenic distillation, pressure-swing adsorption, ion transfer membranes).

The dirty/produced water refers to water containing substantial quantities of dissolved solids, gases, and dissolved or suspended oils (e.g., brackish water, waste water, water from saline aquifers, produced water from oil or bitumen production). The O₂ and fuel gases are burned in near stoichiometric proportions in the presence of atomized dirty/produced water in an oxy-fuel combustor. The products of combustion are composed predominantly of wet steam, CO₂, and a concentrate of the feed water at high pressure and high temperature. The quality of steam which is preferably delivered to a first separator is typically roughly 80% wt steam/CO₂ and 20% wt feed water concentrate but may be of higher or lower quality depending upon the nature of the dissolved solids.

The concentrated brine underflow from the first separator optionally passes through a heat exchanger (HX) to heat the incoming feed water and exits the system for disposal. Disposal may involve injection into a deep saline aquifer, evaporation in a pond with appropriate harvesting and disposal of the solid residue, or crystallization and disposal of the solids contained in the stream.

The saturated steam/CO₂ from the first separator passes preferably into an oxy-fuel reheater where it is direct-heated to a superheated state by near stoichiometric combustion of O₂ and a gaseous fuel, generally the same fuel that supplies the primary oxy-fuel combustor. The superheated steam/CO₂ flows to at least one heat exchanger such as a superheat exchanger (SuperHX) where it heats lower-pressure saturated clean steam to a superheated state. The steam/CO₂ from the SuperHX preferably flows to a second heat exchanger (SatHX) where it heats sub-cooled high-pressure clean water to the saturation conditions and the steam is partially condensed. The wet steam/CO₂ mixture from the SatHX preferably then flows to a third heat exchanger (PreHX) where it preheats high-pressure clean water and additional steam is condensed. The exiting wet steam/CO₂ mixture preferably flows to a condenser/separator where residual steam is condensed and the condensate is separated from CO₂.

The condensate formed from the dirty/produced water is depressurized, such as through a let-down value or a hydro turbine device, and flows into the de-ionized water (DI H₂O Storage) tank which serves as the water supply for the production of clean steam. Depressurization (along with agitation or sparging, as required) causes dissolved gases (primarily CO₂) to come out of solution and be vented (or captured). The DI H₂O Storage tank may incorporate cooling capabilities if necessary to meet downstream polisher temperature requirements.

The degassed water supply is pumped to a polisher to remove residual cations and anions. The cool polished water is then pumped at high pressure through the condenser/separator and PreHX to a first Mix. In the first mixer, the preheated water is mixed with saturated lower-pressure water from the second Sep. and sent to the SatHX where it is heated to its saturation temperature by superheated steam/CO₂. The saturated high-pressure water is flashed via a throttling device into the second Sep. where saturated steam passes overhead and saturated water underflows to the first Mix. and, optionally, also to the second Mix. If the desired clean steam product is superheated steam, the saturated steam is passed through the SuperHX before exiting. If saturated steam is desired it bypasses the SuperHX and directly exits. If wet stream is desired, it bypasses the SuperHX and enters the second Mix. along with saturated water from a liquid discharge of the second Sep. to form the desired steam quality and exits.

OBJECTS OF THE INVENTION

Accordingly, a primary object of the present invention is to provide high pressure substantially pure steam from combustion of a hydrocarbon fuel without atmospheric pollution.

Another object of the present invention is to provide a high pressure heat exchanger which can exchange heat from a high pressure stream of steam and carbon dioxide to a stream of substantially pure high pressure water.

Another object of the present invention is to provide a high pressure heat recovery steam generator which generates substantially pure steam in multiple stages from a stream of high pressure high temperature mixed steam and carbon dioxide.

Another object of the present invention is to provide a method for generating substantially pure steam from a zero emissions combustion based heat source.

Another object of the present invention is to provide a substantially pure stream of high pressure steam from produced water including a variety of contaminates such as waste water, sea water or water and hydrocarbons produced from a hydrocarbon extraction facility.

Another object of the present invention is to provide a method for treatment of waste water.

Another object of the present invention is to provide a system for purification of sea water or other salt water for drinking water supply or other purposes requiring purified water.

Another object of the present invention is to provide a system for generating substantially pure high pressure water which utilizes at least a portion of impurities in the water as a fuel source for a combustor which generates heat for raising of the high pressure steam.

Another object of the present invention is to provide a system including an oxy-fuel combustion gas generator and a high pressure heat recovery steam generator which includes a separator therebetween to remove solids from a steam/CO₂ mixture discharged from the oxy-fuel combustion gas generator.

Other further objects of the present invention will become apparent from a careful reading of the included drawing figures, the claims and detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a system according to one embodiment of this invention including an oxy-fuel combustion gas generator to generate a mixture of steam and carbon dioxide and a multi-stage high pressure heat recovery steam generator for transferring heat from the steam/carbon dioxide mixture to a substantially pure water stream to produce substantially pure steam output.

FIG. 2 is a table identifying exemplary temperature, pressure, flow rate and vapor fraction characteristics for fluids in the system of FIG. 1, at various different points in the system of FIG. 1.

FIG. 3 is a schematic of a process similar to that shown in FIG. 1 but somewhat simplified to show the heat recovery steam generator as a single element.

FIG. 4 is a flow chart identifying various inputs that can be potentially provided into a basic oxy-fuel combustion gas generator and pressurized heat recovery steam generator system and the various outputs from such a system according to this invention.

FIG. 5 is a schematic flow chart similar to that which is disclosed in FIG. 1 but further including depiction of an air separation unit (ASU) for provision of oxygen into the system and further including an oil and associated gas separator downstream from a source of water including hydrocarbon materials therein and with a fuel blender for blending of associated gas from the produced hydrocarbon into natural gas or other hydrocarbon fuels for the gas generator.

FIG. 6 is a flow chart similar to that which is depicted in FIG. 5 and further generally depicting how associated gas and natural gas can be blended for both a gas generator and a reheater of the system in a simplified depiction of the system of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, wherein like reference numerals represent like parts throughout the various drawing figures, reference numeral 100 (FIG. 1) is directed to a typical embodiment system for production of substantially pure high pressure steam from a less pure source of water (referred to as produced water) and oxygen and fuel combusted together within an oxy-fuel combustion gas generator. The system begins with a source of oxygen, a source of hydrocarbon fuel and a source of water which is typically less than pure water; and results in production of more pure high pressure steam. The system 100 potentially also produces substantially pure carbon dioxide and deionized water, while concentrating contaminates in a concentrated brine discharge and without any atmospheric emissions. Other figures depict variations on this typical system 100 when optimized for particular types of initially contaminated water, or when optimized to produce steam of different purity or output other products including carbon dioxide and deionized water or when optimized for utilization of hydrocarbons within produced hydrocarbons or extraction of hydrocarbons for collection away from the system 100.

In essence, and with particular reference to FIG. 4, the basic configuration of a more generalized and somewhat generic depiction of this invention is disclosed. This generalized high pressure substantially pure steam production system 60 generally includes a conceptual boundary 61 with process equipment inside the boundary 61 and various supplies of fluids into the boundaries of the system 61 and discharge of fluids out of the boundary 61. Inputs into the boundary 61 generally include oxygen along line 64, natural gas or other hydrocarbon fuel along line 65, and water along line 66.

This water is depicted in the system 60 of FIG. 4 as deionized water. In other embodiments this water could be produced water which would most typically be water produced from a hydrocarbon extraction facility, such as a steam assisted gravity drain (SAGD) system or other enhanced oil recovery (EOR) system utilizing water and/or carbon dioxide and potentially other constituents, resulting in the produced water including at least some hydrocarbons therein. The definition of produced water also broadly includes less pure water sources including waste water, sea water, and other water sources with dissolved solids, or other contaminating constituents therein.

The oxygen along line 64, natural gas or other fuel along line 65 and water along line 66 are fed into the gas generator 62. The gas generator converts these inputs into a steam/CO₂ mixture along line 67 which is fed to a pressurized heat recovery steam generator (HRSG) 63. An example of such a gas generator 62 can be found in U.S. Pat. No. 6,206,684, incorporated herein by reference. The steam/CO₂ mixture is discharged from this pressurized HRSG 63 along line 70. This steam/CO₂ mixture is then discharged out of the boundary 61 and can have the steam and CO₂ separated from each other for use separately or remain together and utilized in processes calling for such a steam/CO₂ mixture. In at least one embodiment at least a portion of the steam/CO₂ mixture can be recycled back to the water inlet along line 66 back to the gas generator 62.

A separate water source is also fed through the boundary 61 along line 68 into the pressurized HRSG 63. This water along line 68 is substantially pure water at high pressure and is raised to steam within the pressurized HRSG 63 to produce high pressure steam within line 69 discharged out of the boundary 61 of the system for beneficial use of this steam. Such use can be within an oil field to produce further produced water which might be fed back into the system along with the water at line 66, or the steam might be utilized in other steam utilizing processes. The steam 69 could also have power extracted therefrom, such as by running steam through a steam turbine, and then utilizing the pure water for pure water utilizing processes including food processing, industrial processes which require substantially pure water, or as a drinking water source. In the flow chart of FIG. 4, exemplary pressure, temperature and flow rate parameters are depicted consistent with the key also provided in FIG. 4, with such numerical values merely being one typical set of values utilizable in the system 60 of FIG. 4.

More specifically, and with reference to FIGS. 1 and 2, particular details of a typical system 100 according to one embodiment of this invention are described. In FIG. 1 the system 100 is described including elements within the system described with labels and various flow lines between equipment designated with reference numerals. FIG. 2 provides a table 110 with specific values for temperature, pressure, flow and vapor fraction for the fluid passing along these lines at the various different locations of FIG. 1, in this one exemplary example. It is understood that these values could be increased or decreased in various alternative embodiments, or fluctuate during the operation of a single embodiment. Also, some of the numerical values are identified as “TBD.” It is understood that one of skill in the art could use a variety of different optimization and design parameters to select an appropriate value which would balance the system and optimize performance.

In the particular example of FIG. 1, the system is configured to take “produced water” into the system as a water input. This produced water in a most typical embodiment is water that includes a hydrocarbon therein and is in the form of water at an output of a hydrocarbon recovery operation or facility, such as a steam assisted gravity drain (SAGD) facility or outflow pumped from an oil well undergoing enhanced oil recovery (EOR) procedures, such as with water flooding or injection of steam or elevated temperature water with or without carbon dioxide.

Also, within this definition of “produced water” would be other water streams which are less than pure water. Examples include waste water, such as effluent at a waste water treatment plant or other waste water coming from a discharge of some processing facility. The waste water might include solid particulates which would be pre-filtered out of the water but also have dissolved solids which would enter into the system 100. Produced water could also be in the form of sea water or other salt containing water. Thus, the term “produced water” is generally provided to refer to any water which is less than substantially pure and typically either of a sufficiently poor quality that it cannot be utilized with optimal performance within a high pressure steam utilizing process or machine, or includes hydrocarbons of value either for their heating value or as separate commodities, such that it is desirable to either utilize the entrained hydrocarbons for heat or separate entrained hydrocarbons for collection away from the system.

An oxy-fuel combustor (also called a gas generator) is provided in the system 100 which receives oxygen 1 and fuel 2, typically at an injector end of an elongate combustion chamber. An igniter would also typically be provided at the injector end to initiate combustion. At least one water line 11 also feeds water inlets into the oxy-fuel combustion gas generator. The water inlets are most preferably at multiple locations within the oxy-fuel combustor with at least one water inlet adjacent an injector end and near a fuel and oxygen inlet into the oxy-fuel combustor, and other water inlets downstream from an injection end of this oxy-fuel combustor. It is also conceivable that some of this water would be provided after the oxy-fuel combustor but before additional downstream equipment, especially if no hydrocarbons in the water 11 are to be combusted in the gas generator.

The water 11 entering into the oxy-fuel combustor is high pressure water typically elevated in pressure by a pump upstream of the oxy-fuel combustor. This water is also preferably heated before passing through the pump (or conceivably after passing through the pump). For instance, a produced water stream 5 passes through a heat exchanger which exchanges heat with concentrated brine 12 exiting a first separator. This concentrated brine 12 has reduced heat after passing through this heat exchanger and is discharged from the system as concentrated brine 6.

The oxy-fuel combustor combusts the hydrocarbon fuel with oxygen to produce products of combustion including steam and carbon dioxide. The produced water 11 added to the oxy-fuel combustor is heated within the oxy-fuel combustor so that an outlet of the oxy-fuel combustor discharges a steam/CO₂ mixture 10. This mixture 10 is fed into a first separator. This first separator is provided to primarily remove salts and other dissolved solids from the steam/CO₂ mixture 10. In particular, most preferably the pressure of the steam/CO₂ mixture is quite high (i.e. 1,500 psi) and the temperature is moderately high but not sufficient to cause the steam/CO₂ to be superheated, but rather to be saturated with some liquid fraction. A degree of liquid fraction supplied in this steam/CO₂ mixture can be controlled by controlling an amount of the produced water 11 which bypasses the oxy-fuel combustor or enters later stages of the oxy-fuel combustor, but joins with the steam/CO₂ mixture before entry into the first separator.

Such a condensing wet steam/CO₂ flow into the first separator will tend to have a liquid water fraction of the steam condensed into liquid at a lower portion of the first separator. Dissolved solids will tend to remain with this liquid fraction as a concentrated brine.

The first separator can be shaped to optimize this separation further, such as by being shaped cylindrically and with an elongate form and with a gaseous outlet elevated above a liquid outlet. Optionally, an offset inlet, such as in the form of a cyclone separator, can be provided to further enhance efficiency of separation. Potentially catalysts or other inducers of solids separation from the steam in the form of materials or particular flow control element geometries could also be provided within the first separator to most effectively separate any dissolved solids into a small liquid fraction resulting in a concentrated brine 6.

If the produced water 5 includes entrained hydrocarbons therein, beneficially such hydrocarbons entering said gas generator sufficiently close to the injector end of the oxy-fuel combustor and where sufficient temperature exists within the combustor to cause the hydrocarbons within the water to be combusted. Excess oxygen can be supplied sufficient to drive such combustion, preferably to complete combustion of any such hydrocarbons within the produced water, to complete reaction into steam and carbon dioxide.

A gaseous outlet from the first separator can be passed directly to a pressurized heat recovery steam generator. However, in this particular embodiment it is desirable that this wet steam/CO₂ mixture exit the first separator and pass into a reheater. The reheater includes an inlet for oxygen 3 and an inlet for fuel 4 along with wet steam/CO₂ and combusts the oxygen 3 with fuel 4 to produce additional products of combustion including steam and carbon dioxide which are then mixed with the steam/CO₂ mixture from the first separator to produce a final mixture of steam and carbon dioxide having a greater ratio of carbon dioxide to steam than the steam/CO₂ mixture 10. This new steam/CO₂ mixture has been heated to a higher temperature and is a superheated steam/CO₂ mixture 13.

This mixture 13 is then fed into a high pressure heat recovery steam generator (HRSG) identified as a superheat exchanger (SuperHX). Pressure of the steam/CO₂ mixture 13 has remained similar as that when discharged from the original gas generator, and in this embodiment is identified for illustration purposes as approximately 1,500 psi. Thus, a very high temperature and high pressure superheated gas mixture of steam and carbon dioxide 13 passes into the SuperHX where it gives up heat to a substantially pure steam 23 also entering the SuperHX before the steam/CO₂ mixture discharges from the SuperHX along line 14. Typically, this steam/CO₂ mixture still contains one hundred percent vaporized steam, but typically near a saturation temperature for the high pressure involved.

This steam/CO₂ mixture then passes into a second portion of the HRSG referred to as a saturated heat exchanger (SatHX). In the SatHX further heat exchange to pure water 21 occurs until the steam/CO₂ mixture is discharged from the SatHX along line 15. At this point, the high pressure steam/CO₂ mixture has now begun to condense and is typically a combination of liquid and gaseous water as well as gaseous carbon dioxide.

Next, the steam/CO₂ mixture passes into a final stage of the pressurized HRSG of this embodiment which is referred to as a preheat exchanger (PreHX). The steam/CO₂ mixture exists the PreHX along line 16 after giving up heat to substantially pure water 19 with the steam/CO₂ mixture now having little to no remaining gaseous steam along with gaseous carbon dioxide.

The steam/CO₂ then passes into a condenser. In this condenser remaining vaporized water condenses into a liquid so that a majority of gases remaining within the condenser are in the form of carbon dioxide. This carbon dioxide is discharged from the condenser through a gaseous outlet 9 from the condenser. This CO₂ discharge 9 includes substantially pure CO₂ which may include other non-condensible gases which might include argon from an air separation unit or excess oxygen provided to drive combustion reactions within the gas generator and/or reheater to completion, and potentially small trace amounts of other non-condensible gases.

The CO₂ can beneficially be utilized for enhanced oil recovery (EOR) or utilized for other processes which call for substantially pure carbon dioxide. If the carbon dioxide needs to be drier, it can be further cooled and otherwise processed to condense remaining water vapor from the carbon dioxide. The CO₂ can also be further pumped, if required to be at a higher pressure.

A lower end of the condenser includes a water outlet 17 which leads to a water storage tank. This water storage tank is referred to as a deionized water storage tank in this embodiment with it including a cooling water circuit as well as a vent for any non-condensible gases which might have remained with the water. A polisher loop is preferably provided to route the water through a series of pumps and a polisher along line 18 to remove remaining ions from the water and supply the water as deionized water especially for systems which require that supplied water be deionized water. Deionized water can be discharged from the system at various locations, including from the deionized water storage tank along line 8.

The polished water 18 is preferably fed back through the condenser where it acts as coolant to condense the steam/CO₂ mixture 16 and also to elevate temperature of this substantially pure water supply discharged from the condenser at 19. The substantially pure water supply then passes through the PreHX to be heated further and pass into line 20.

Before this water further passes into the SatHX at line 21, the water preferably passes into a first mixer. This first mixer provides a location where condensed water vapor can be added to the pure water for further heating such water vapor supplied along line 25. The water at line 21 is still preferably liquid at the high pressures involved. The water then passes through the SatHX where it is further heated and discharged at line 22. At line 22, the water has been heated to close to a boiling point for the high pressure involved (approximately 1,450 psi). This water then preferably passes through an expansion valve which drops the pressure somewhat and rapidly converts the high pressure high temperature water to slightly lower pressure and substantially entirely steam within a second separator.

This second separator includes a lower end for any remaining liquid water to exit along line 28 and be returned along line 25 back to the first mixer. The substantially pure steam leaving the second separator can be passed to the SuperHX along line 30 or can bypass the superheat exchanger along line 31 or can pass directly into a second mixer along line 29. This second mixer defines a location where some water directly from the second separator along line 29 can be mixed with water passing through the SuperHX and discharged along line 24 before passage into the mixer. Liquid water from the second separator can also optionally be fed forward into this second mixer along line 26. The resulting steam in this second mixer can have a quality and temperature and pressure optimized for discharge along line 27 and removal from the system 100 along line 7 as steam having desired properties for discharge from the system.

With particular reference to FIG. 3, a system 40 is disclosed which is in many ways similar to the system 100 of FIG. 1 but somewhat simplified. In particular, a single heat recovery steam generator, referred to as a SuperHX, is shown. Also, the option of the produced water passing through the heat exchanger before supply along line 48 to water inlets along line 43, or alternatively passing directly from a produced water supply 47 to the water inlet 43 of the oxy-fuel combustor, is disclosed.

Generally, the system 40 includes an oxygen inlet 41 and a fuel inlet 42 into the oxy-fuel combustor along with water inlets 43. An outlet of the oxy-fuel combustor for a steam/CO₂ mixture is provided along line 44 which passes into a separator. Concentrated brine discharges from the separator along line 45 and can optionally exchange heat with produced water 47 before being discharged from the system 40 as concentrated brine along line 46.

A high pressure gaseous flow from the separator along line 49 is passed through a reheater where a further combustion of oxygen 50 and fuel 51 superheats the steam/CO₂ mixture at line 52. This superheated steam/CO₂ mixture then exchanges heat in the SuperHX with pure water along line 58. This steam/CO₂ mixture is then discharged from the SuperHX along line 53 and then passes into a condenser where a water portion of the steam/CO₂ mixture condenses into water and a gaseous portion in the form of substantially carbon dioxide discharges from the condenser at line 55.

The water leaves the condenser along line 54 and passes into a water storage tank. This water can be deionized and discharged along line 57 from the system. Water can also pass through a polisher along line 56 and then through the condenser for preheating before passing along line 58 into the SuperHX, where the water is boiled into steam and passes along line 59 for discharge from the system as high pressure steam. Because the steam/CO₂ mixture is high pressure within the SuperHX and the water at line 58 is also at high pressure within the SuperHX (although the water/steam flow would typically be lower pressure than the steam/CO₂ mixture flow), this pressure differential is less than it would be if the steam/CO₂ mixture were at atmospheric pressure or near atmospheric pressure, thus simplifying and decreasing a size of the heat exchange components within the superheat exchanger over what they would otherwise be.

With particular reference to FIGS. 5 and 6, details of further systems 80, 90 are disclosed which are only slightly varied relative to each other. In these further flow diagrams details unique from those of previous systems 40, 100 are emphasized. An air separation unit can be provided which receives air and power and outputs oxygen upstream of the gas generator and reheater. Produced water is referred to in the system 80 as “produced hydrocarbons” and includes hydrocarbons of some form which could be solid, liquid or gaseous. A three phase oil separator is provided which receives the produced hydrocarbons. This three phase oil separator includes an output for oil and/or bitumen which can condense within or settle by gravity separation or other methods out of the three phase oil separator. Associated gas is also removed from the three phase oil separator utilizing known techniques.

The associated gas could be discharged from the system. In the system 80 of FIG. 5 this associated gas preferably passes on to a fuel blending process which also receives natural gas or other hydrocarbon fuel and the associated gas is blended with the natural gas or other fuel to produce fuel at a fuel inlet of the gas generator which has a heating value desired for the flow rate of oxygen also input into the gas generator.

The three phase oil separator also includes a water outlet which outlets produced water which also typically includes remaining hydrocarbons therein. This produced water can be preheated by the stream of concentrated brine leaving the steam separator downstream of the gas generator (GG) and upstream of the reheater (RH). The produced water is thus elevated in temperature before it also passes into the gas generator. Hydrocarbons within the produced water can be combusted within the gas generator along with the fuel. The gas generator thus discharges a mixture of steam/CO₂ at high pressure. Other portions of the system 80 are configured similar to the systems 100 and 40. In this embodiment a cooling water flow of water which is already substantially pure water passes through the condenser first and then passes through the pressurized heat recovery steam generator to raise substantially pure high pressure steam for other processes.

In the system 90 of FIG. 6 associated gas which could be provided downstream from a three phase oil separator, such as that depicted in FIG. 5, is combined with natural gas or other hydrocarbon fuel upstream of either the gas generator (GG) or upstream of the reheater (RH). The associated gas would also typically pass through some form of fuel blender such as that depicted in FIG. 5. Other portions of the system 90 depicted in FIG. 6 are similar to details of the system 80 of FIG. 5.

This disclosure is provided to reveal a preferred embodiment of the invention and a best mode for practicing the invention. Having thus described the invention in this way, it should be apparent that various different modifications can be made to the preferred embodiment without departing from the scope and spirit of this disclosure. When structures are identified as a means to perform a function, the identification is intended to include all structures which can perform the function specified.

Claims

1. A zero or near zero emissions system for producing substantially pure high pressure steam, comprising in combination:

a high pressure source of oxygen having a pressure at least ten times standard atmospheric pressure;

a high pressure source of hydrocarbon fuel having a pressure at least ten times standard atmospheric pressure;

a high pressure source of water having a pressure at least ten times atmospheric pressure;

a gas generator having a fuel inlet, an oxidizer inlet and a water inlet;

said oxidizer inlet coupled to said high pressure source of oxygen, said high pressure source of oxygen being a majority oxygen;

said fuel inlet coupled to said high pressure hydrocarbon fuel source;

said water inlet coupled to said high pressure source of water;

said gas generator combusting the hydrocarbon fuel and the oxygen to produce steam and CO2 and adding water from the water inlet to the produced steam and CO2 before said outlet to provide a steam/CO2 mixture discharged from said gas generator at said outlet; and

a high pressure heat exchanger downstream of said outlet of said gas generator having a high pressure steam/CO2 mixture line downstream of said gas generator outlet with a pressure in said high pressure steam/CO2 mixture line at least ten times greater than atmospheric pressure and a substantially pure high pressure water line with a pressure at least ten times greater than atmospheric pressure, said high pressure steam/CO2 mixture line in heat transfer relationship with said high pressure substantially pure water line to heat water in said substantially pure water line into substantially pure high pressure steam with a pressure at least ten times greater than atmospheric pressure.

2. The system of claim 1 wherein no expander is located between said outlet of said gas generator and said high pressure steam/CO2 mixture line of said heat exchanger.

3. The system of claim 1 wherein a dissolved solids separator is located between said outlet of said gas generator and said high pressure steam/CO2 mixture line of said heat exchanger, said separator including an inlet for the steam/CO2 mixture from said gas generator, a discharge for the steam/CO2 mixture and an output for a concentrated brine including solids removed from the steam/CO2 mixture discharged from said gas generator outlet.

4. The system of claim 3 wherein a reheater is located between said discharge of said separator and said high pressure steam/CO2 mixture line of said heat exchanger, said reheater including a fuel inlet coupled to said source of hydrocarbon fuel and an oxidizer inlet coupled to said source of high pressure oxygen, said reheater combusting the hydrocarbon fuel and the oxygen to produce additional steam and CO2 and adding the steam/CO2 mixture from said discharge of said separator before a reheater output to produce a further heated steam/CO2 mixture discharged from said reheater output.

5. The system of claim 3 wherein said concentrated brine outlet of said separator is coupled to a heat exchanger in heat transfer relationship with said high pressure source of water upstream of said water inlet of said gas generator.

6. The system of claim 5 wherein said high pressure source of water is produced water including non-water constituents therein.

7. The system of claim 6 wherein said source of high pressure water in the form of produced water includes fuel entrained therein, said fuel at least partially combusted in said gas generator with the hydrocarbon fuel from said source of hydrocarbon fuel and the oxygen from said high pressure source of oxygen.

8. The system of claim 7 wherein said high pressure source of water includes fuel entrained therein including associated gas as at least a portion of the fuel entrained therein, and wherein a separator is provided between said high pressure source of water and said gas generator water inlet to remove at least a portion of the associated gas from the produced water.

9. The system of claim 8 wherein said associated gas separator includes a gas outlet upstream of a fuel blender, said fuel blender located between said high pressure source of hydrocarbon fuel and said fuel inlet of said generator, said fuel blender blending at least a portion of the associated gas with the hydrocarbon fuel from said high pressure source of hydrocarbon fuel to deliver at least a portion of the associated gas with the hydrocarbon fuel to said fuel inlet of said gas generator.

10. The system of claim 8 wherein said associated gas separator also includes a liquid hydrocarbon outlet for removing liquid hydrocarbons from the produced water before routing of the produced water into said water inlet of said gas generator.

11. The system of claim 1 wherein said heat exchanger includes at least two separate heat exchangers in series along said steam/CO2 mixture line downstream of said gas generator outlet and along said substantially pure high pressure water line, and wherein said substantially pure high pressure water line includes a feedback line between said at least two stages of heat exchangers returning a portion of the substantially pure high pressure water back to a location on said substantially pure high pressure water line preceding a first stage of said heat exchanger, such that a liquid fraction of the substantially pure high pressure water can be fed back for further heating and a higher quality of superheated steam is discharged from said heat exchanger.

12. The system of claim 11 wherein said substantially pure high pressure water line is located downstream of a pump and a condenser, said condenser located downstream of said high pressure steam/CO2 mixture line of said heat exchanger, with said condenser including an outlet for gases including carbon dioxide and a liquid outlet for substantially pure water for supply to said pump and said substantially pure high pressure water line of said heat exchanger.

13. A method for producing substantially pure high pressure steam, comprising in combination:

providing a gas generator having a fuel inlet coupled to a high pressure source of hydrocarbon fuel, an oxidizer inlet coupled to a high pressure source of oxygen, the source of oxygen being a majority oxygen, a water inlet coupled to a high pressure source of water, said high pressure sources of oxygen, hydrocarbon fuel and water each having a pressure of at least ten times standard atmospheric pressure;

combusting the hydrocarbon fuel and the oxygen within the gas generator to produce steam and CO2 and adding water from the water inlet of the gas generator to the produced steam and CO2 before an outlet from said gas generator to produce a steam/CO2 mixture;

discharging the steam/CO2 mixture from the gas generator at a gas generator outlet; and

exchanging heat between the steam/CO2 mixture downstream of the gas generator outlet and substantially pure high pressure water in a substantially pure high pressure water line having a pressure of at least ten times standard atmospheric pressure.

14. The method of claim 13 including the further step of separating solids from the steam/CO2 mixture downstream of the outlet of the gas generator and before said exchanging heat step.

15. The method of claim 14 including the further step of reheating the steam/CO2 mixture after said separating of solids step and before said exchanging heat step by routing the steam/CO2 mixture to a reheater including an oxygen inlet coupled to said source of oxygen and a fuel inlet coupled to said source of hydrocarbon fuel and combusting the oxygen and fuel to produce additional steam and carbon dioxide and combining the created steam and carbon dioxide with the steam/CO2 mixture and discharging a new higher temperature steam/CO2 mixture from an output of the reheater.

16. The method of claim 14 wherein said separating of solids step includes discharging a concentrated brine from a separator interposed between the outlet of the gas generator and before said exchanging heat step, the concentrated brine exchanging heat with high pressure water from the high pressure source of water upstream of the water inlet of the gas generator.

17. The method of claim 14 wherein the high pressure source of water includes fuel entrained therein, and wherein said combusting step includes combusting fuel entrained with the water with oxygen within the gas generator.

18. The method of claim 17 including the further step of separating associated gas from the high pressure source of water upstream of the water inlet of the gas generator and routing the separated associated gas to a fuel blender between the high pressure source of hydrocarbon fuel and the fuel inlet of the gas generator for blending of at least a portion of the associated gas from the high pressure source of water with the hydrocarbon fuel from the high pressure source of hydrocarbon fuel before entry into the fuel inlet of the gas generator.

19. The method of claim 18 including the further step of separating liquid hydrocarbons from the high pressure source of water and discharging the separated liquid hydrocarbons from the system.

20. The method of claim 13 wherein said exchanging heat step includes at least two separate stages of exchanging heat between the steam/CO2 mixture and the substantially pure high pressure water, and wherein a liquid portion of the high pressure water between the stages of exchanging heat is fed back to an upstream portion of the substantially pure high pressure water for further heating thereof in an earlier stage of the exchanging heat step.

21. The method of claim 13 including the further step of condensing the steam/CO2 mixture after said exchanging heat step, separating at least a portion of CO2 from the steam/CO2 mixture, pumping a water portion of the steam/CO2 mixture to a pressure at least ten times greater than standard atmospheric pressure and supplying the pressurized water as at least a portion of water in the substantially pure high pressure water line of said exchanging heat step.