FIELD OF THE INVENTION
The present invention relates generally to heating water. More specifically, the present invention relates to a high efficiency, high capacity, submerged combustion apparatus and method for heating water and other liquids.
BACKGROUND OF THE INVENTION
Submerged combustion is a high efficiency system for heating water and other liquids. The liquid is heated by direct contact heat and mass transfer with hot products of combustion. The liquid is generally water, but other solutions may be heated. Various systems are employed to provide the direct contact transfer between the products of combustion and the liquid to be heated. The thermal efficiency of a submerged combustion system heating liquids can be higher than 90%. A submerged combustion water heater with a stack gas temperature of 70 degrees F. has a thermal efficiency of about 100%.
The submerged combustion system is used for heating large quantities of liquids at high efficiencies in many industrial and commercial applications. In addition to heating liquids, submerged combustion is utilized for concentrating water solutions by evaporating water from the solution.
The conventional heater is equipped with submerged combustion burners firing into a liquid bath. The products of combustion are discharged into the bath. The discharge location is generally at a liquid submergence depth greater than two feet. The burner system includes a large high horsepower blower for providing combustion air. The submerged combustion burner provides heat, circulation, and turbulence for heat transfer.
There are many patents describing submerged combustion water heaters. The patents describe submerged pressurized products of combustion being bubbled through various combinations of holes and weirs to contact and heat water. The products of combustion are at a pressure sufficiently high to overcome the submergence depth. Deeper submergence depths require larger and higher horsepower combustion air blowers. In an application where the burner assembly discharges into water with an equivalent depth of 48 inches, the blower discharge pressure would need to be 48 inches water column plus the additional pressure drop of the system. Other patents disclose various water spray arrangements contacting the products of combustion to heat water. These patents do not teach or suggest the products of combustion and water flow arrangement of this disclosure nor do they present the arrangement used to contact the products of combustion with the water flow to heat water as taught in this specification.
Objectives
Several objectives of this patent follow:
- To provide a high thermal efficiency system for heating water and other fluids.
- To provide a submerged combustion system with operates with low combustion gas back pressure.
- To provide a high capacity water heating system.
- To provide a single burner water heating system.
- To provide an arrangement with less potential for apparatus vibration.
- To provide a burner/blower system with low installed horsepower.
- To provide a submerged combustion system heating water with low water pressure drop across the apparatus.
- To provide a high capacity submerged combustion system for heating water circulating in a loop and heating once through water flow applications.
- To provide the heat source for a complete system for vaporizing LNG.
- To provide a submerged combustion system meeting air quality regulations.
- To provide a submerged combustion heater for many commercial and industrial applications including vaporizing water and other fluids and concentrating solutions.
- To provide a system which can be quickly and easily started and shutdown.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, a submerged combustion water heating apparatus comprising a combustion chamber, a burner assembly firing into the combustion chamber and producing products of combustion, at least one set of perforated plates, wherein the products of combustion flow generally through apertures in the perforated plate, a submerged combustion water inlet plenum, a water inlet means and a submerged combustion water outlet plenum, wherein water is directed through the submerged combustion inlet plenum, through the water inlet means to flow generally across at least one set of perforated plates and be heated by the products of combustion and collected in the submerged combustion water outlet plenum.
In accordance with another aspect of the invention, a submerged combustion method of heating a fluid including the steps of providing a source of products of combustion and a fluid inlet means, providing at least one set of perforated plates, directing fluid to flow through fluid inlet means and generally across at least one set of perforated plates, passing products of combustion through apertures in the perforated plate, contacting the fluid and the products of combustion, heating the fluid using products of combustion and collecting the heated fluid.
In accordance with yet another aspect of the invention, a submerged combustion heat source vaporizer comprising a combustion chamber, a burner assembly firing into the combustion chamber and producing products of combustion, at least one set of perforated plates, wherein products of combustion flow generally through apertures in at least one set of perforated plates, a submerged combustion heat source water inlet plenum, a submerged combustion water inlet means, and a submerged combustion heated water plenum, wherein water is directed through the submerged combustion heat source water inlet plenum and through the submerged combustion water inlet means to flow generally across the perforated plate and be heated by the products of combustion and be collected in the submerged combustion heated water plenum, an annular space, wherein the submerged combustion heated water plenum communicates with the annular space, at least one inlet manifold and at least one outlet manifold, rows of spiral tube heat transfer circuits for containing and vaporizing fluids being positioned generally within the annular space and communicating with at least one inlet manifold, a water outlet plenum communicating with the annular space, wherein the water outlet plenum communicates with the submerged combustion heat source water inlet plenum, and at least one pump circulating water from the water outlet plenum to the submerged combustion heat source water inlet plenum.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevation cross section of a cylindrical submerged combustion heater.
FIG. 2 is an elevation cross section of a cylindrical submerged combustion heater with an outlet water liquid seal arrangement.
FIG. 3 is an elevation cross section of a cylindrical submerged combustion water heater of this invention utilized as a heat source for a submerged combustion LNG vaporizer.
FIG. 4 is an elevation cross section detail showing an annular plate.
DETAILED DESCRIPTION OF THE INVENTION
The present invention discloses a submerged combustion water heating system which differs from conventional submerged combustion heaters. A unique products of combustion and water flow arrangement provides the heat and mass transfer contact between the water and the products of combustion. The submerged combustion system using this unique arrangement has high efficiency and many advantages.
FIG. 1 and FIG. 2 show two arrangements of the submerged combustion heating system. The water heating portion of both heaters is similar. The submerged combustion arrangement in FIG. 1 is used for heating water circulating in a loop and for heating a large quantity of water flowing through the submerged combustion apparatus. In the circulating loop application the quantity of water returning to the submerged combustion apparatus is essentially the same as that leaving. Heated water leaves the submerged combustion system and circulates through a heat exchanger or similar system where heat is extracted from the water. A pump is generally used to circulate the water. The cooler water returns to the submerged combustion system to be reheated. The water pH of the submerged combustion system operating in a closed loop can fall. The addition of chemicals to maintain the proper water quality may be required. The combustion reaction produces water. At cooler submerged combustion operating temperatures the produced water is retained in the submerged combustion apparatus. The quantity of water in the circulating loop will increase at a low rate. The submerged combustion system operating at warmer temperatures will have a net decrease in water quantity in the submerged combustion apparatus as a result of water leaving the submerged combustion apparatus via the flue stack. The addition or loss of water in the circulating loop results in level changes in the apparatus water level. Controls are provided to discharge or add water to maintain the operating water level. Heating water flowing through the submerged combustion FIG. 1 arrangement not in the circulating loop configuration requires control means to maintain the operating water level in the apparatus.
The submerged combustion arrangement in FIG. 2 is used in applications such as snow melting where the heated water is open to the atmosphere. The FIG. 2 submerged combustion arrangement can be used for concentrating water solutions by evaporation. The FIG. 2 submerged combustion arrangement can also be used for the same types of applications as those of the FIG. 1 arrangement. In addition to heating water, both arrangements can be used for heating sea water, water solutions and other fluids. Both arrangements can be used in applications where the heated water flows to a heated water user such as a vaporizer or heat exchanger.
Referring now to FIG. 1, the submerged combustion cylindrical shaped water heating apparatus 10 is shown in FIG. 1. The apparatus 10 includes the burner assembly 11 firing into the combustion chamber 12 producing products of combustion gases. The burner assembly 11 includes the combustion air blower and motor. The combustion chamber 12 is of sufficient diameter and length to obtain the required combustion efficiency and required emissions in combination with the burner assembly. An outer cooling jacket 13 provides an annular space surrounding the combustion chamber. Water is directed to the cooling jacket annular space for cooling the combustion chamber wall by pump 14. In some applications a portion of the inlet water can be directed to the annular space for cooling, thereby eliminating pump 14. A portion of the combustion chamber cooling flow can evaporate and produce steam as it exits the annular space. Means can be provided to increase the portion and quantity of combustion chamber cooling flow being evaporated. The resulting vaporized water will combine with the products of combustion. The composition of the term “products of combustion” as provided in this disclosure will include water vapor produced during the combustion process and can include additional water vapor from other sources. The products of combustion exit the combustion chamber 12 and flow through apertures in perforated plate 15 in a generally ascending manner contacting water flowing across perforated plate 15. The perforated plate 15 is installed with a slope as shown or can be installed horizontally, or at other positions. The length of the perforated plate is sized to provide sufficient contact area between the flowing water and the combustion products and sized for other considerations. The perforated plate can also be plate or tray arrangements with apertures. Another set of perforated plates can be included stacked above the other to provide additional contact area. The stacked plates are arranged such that the products of combustion flow through each plate. A plate arrangement as shown in FIG. 4 and described later provides additional heat and mass transfer contact area between the water and the products of combustion. The combustion products exit the perforated plate 15 in FIG. 1 and are collected in the lower flue plenum 16 and pass through several flue vents 17 to the upper flue plenum 18. An optional water spray system 19 can be installed in upper flue plenum 18 to further cool the products of combustion and increase the efficiency. Some liquids subjected to submerged combustion can produce foaming. The spray system 19 can also be used to reduce foaming, if foam is present. The flue plenums 16 and 18 can be sized to help reduce the quantity of foam and water entering the flue stack. The flue stack 20 connects to the upper flue plenum 18. The flue stack 20 discharges the flue products to atmosphere. Alternately, the flue stack 20 can be connected directly to the flue vent 17. The upper flue plenum 18 would be eliminated in this alternate arrangement. Several flue stacks would be required. A flue stack would be required for each flue vent. The optional water spray system 19 would be located in the lower flue plenum 16 in this alternate arrangement.
The water side of the submerged combustion system is designed in a unique way to accommodate large water flows. These large water flows are heated with efficient contacting means. The required pressure of the products of combustion is low. The inlet water to be heated in FIG. 1 enters the inlet plenum 21. The inlet plenum 21 is vented to the atmosphere via vent 22. The inlet water is distributed to the inlet water down corner 23 and flows through orifice opening 24. Orifice opening 24 can be adjustable. Orifice opening 24 is the opening between down corner plate 25 and perforated plate 15. Additional orifice openings can be provided to accompany additional sets of stacked perforated plates. The water exiting orifice opening 24 flows as a high velocity stream generally across perforated plate 15 contacting products of combustion flowing through apertures in perforated plate 15 providing heat and mass transfer between the streams. A small portion of the water may flow through holes in perforated plate 15. The water flowing generally across perforated plate 15 discharges into outlet water plenum 26. Adjustable baffle plate 27 prevents products of combustion from bypassing perforated plate 15. Baffle plate 27 provides a liquid seal to contain the products of combustion. Means are provided to direct a stream of water toward or along baffle plate 27 for cooling of the plate (not shown). Baffle plate 27 can be positioned to provide a depth adjustment for water flowing over perforated plate 15. Control means are provided to maintain plenum 26 water level within operating limits (not shown). A baffle arrangement can be included in plenum 26 to help inhibit wave action. The heated water exits outlet water plenum 26. The patent configuration provides ample heat and mass transfer area between the products of combustion and water. The contact area includes the heated water plenum 26 surface, the perforated plate 15, the zone above perforated plate 15, optional spray systems and other areas where the water is being heated with products of combustion.
The combustion chamber annular space cooling flow discharge can be routed to join the down corner flow as an alternate to discharging directly into the combustion chamber. The combustion chamber cooling flow discharge could also be piped to another location.
Referring now to FIG. 2, the submerged combustion cylindrical shaped water heating apparatus 10A is shown in FIG. 2. The upper portion of the FIG. 2 water heating configuration is similar to the FIG. 1 water heating configuration. The lower part of the FIG. 2 arrangement includes the addition of an outlet water liquid seal and weir assembly not included in the FIG. 1 arrangement. The water flowing across perforated plate 15 discharges into upper outlet water plenum 28. A weir plate 29 maintains the upper outlet water plenum 28 liquid level and provides a vapor seal which prevents products of combustion from bypassing perforated plate 15. The outlet water flows from upper outlet water plenum 28 over weir 29 into center outlet water plenum 30. A liquid seal weir plate pan 31 maintains the center outlet water plenum 30 liquid level and provides a vapor seal. The outlet water flows from the center outlet water plenum 30 over the weir plate pan 31 into the lower outlet water plenum 32. The vapor space above lower outlet water plenum 32 is generally vented or open to atmosphere (not shown). The lower outlet water plenum 32 includes the heated water outlet which connects to heated water users. The lower outlet plenum 32 can be modified to accommodate a snow melting system. Other liquid level control means can be utilized to maintain the outlet water plenum 28 and 30 liquid levels.
Refer now to FIG. 3, which is an elevation view cross section of a spiral tube circuit LNG vaporizer utilizing the submerged combustion water heater heat source. The lower portion of FIG. 3 illustrates an embodiment teaching of Engdahl U.S. Provisional Patent 60/516,845 SPIRAL TUBE LNG VAPORIZER. In Provisional Patent 60/516,845 the submerged combustion heat source water plenums have been arranged to connect and communicate with the LNG vaporizer device plenums. The same water plenum arrangement is depicted in FIG. 3. In FIG. 3 the water to be heated enters the submerged combustion heat source via the submerged combustion water inlet plenum 21. The water flows upward within the heat source inlet plenum 21 to the horizontal inlet plenum 21 and into an annular down corner 23 surrounding the combustion chamber. The water exits the down corner through an orifice 24 and flows across a radial perforated plate 15 where it is heated by products of combustion passing through apertures in the perforated plate. A plate arrangement as shown in FIG. 4 and described later provides additional heat and mass transfer contact area between the water and the products of combustion. The water exits the down corner orifice at a high velocity and flows across the perforated plate as a high velocity stream. The heated water is collected in the submerged combustion heated water outlet plenum 26 and directed downward through the vaporizer annular space containing the spiral tube heat transfer circuits. The cooler water exiting the lower portion of the annular space is circulated via the water circulator to the submerged combustion heat source water inlet plenum 21 for heating. The water circulator can be a propeller or axial flow pump, a centrifugal pump, ejector pump, or another device to circulate the water. The water circulator can be provided with a variable speed driver.
The burner assembly 11 fires into the combustion chamber 12 and produces products of combustion gases. The products of combustion flow from the combustion chamber through apertures in the radial perforated plate 15. The products of combustion heat the water flowing over the perforated plate. The products of combustion exiting the perforated plate are collected in flue plenum 16 and flow through the flue stack 20 to the atmosphere.
The LNG vaporizer device shown in the lower portion of FIG. 3 includes the LNG inlet manifold, the LNG vapor outlet manifold, rows of spiral tube heat transfer circuits positioned within an annular space and the outlet plenum. The spiral tube circuits can also be installed with an interstage manifold. A portion of the spiral tube circuits would connect to an inlet manifold on one end and connect to an interstage manifold on the other end. Another portion of the spiral tube circuits would connect to the interstage manifold on one end and connect to an outlet manifold on the other end. The interstage manifold can be designed as a separator to collect and remove hydrocarbon liquids from the send out stream. The rows of spiral tube heat transfer circuits are supported by support bars. The spiral tube circuits are shown in the aligned position in FIG. 3. Each tube within the spiral tube circuit is placed generally vertically above each tube in the row below. The spiral tube circuits can also be placed in the staggered position. In the staggered position each tube within the spiral tube circuit is placed generally above the gap in the row below. The vertical spacing of the support rods is slightly larger than the sum of the outside diameter of a heat transfer tube plus the diameter of a support rod, providing vertical clearance such that movement of the tubes is not restricted by the above support rods. The rows of spiral tube circuits are not supported by tubes in the row below. Each row is supported by its system of support rods. The tube is not restricted from moving as it is cooled down or warmed up. Independent movement is provided for each spiral tube circuit row. Individual heat transfer tubes and circuits can cool down or warm up at different rates without high thermal stresses. The tube movement is generally in a radial direction. In some applications that portion of the spiral tube circuit nearest the cold inlet manifold will ice. The tube pitch of the tubes in a spiral tube circuit is adjusted in the design as required to accommodate the tube ice layer on the colder part of the spiral circuit. The tube pitch can be adjusted to allocate heating medium flow. The water circulator or pump is positioned in the outlet plenum. Several water circulators can be utilized. The pump circulates the cooler heating medium to the submerged combustion water inlet plenum 21.
The LNG vaporizer can be configured with several heat source arrangements and several LNG heat transfer surface area arrangements. The submerged combustion heat source can be located above the heat transfer area or adjacent to the LNG heat transfer surface area. The heat transfer surface area arrangements can include a spiral tube arrangement, a helix arrangement, a serpentine arrangement, or a shell and tube exchanger. The configuration of Engdahl patent application Ser. No. 10/869,086 for a RELIABLE LNG VAPORIZER can provide the LNG heat transfer area. Piping may be required as extensions of the water plenums to connect the various LNG heat transfer surface area arrangements to the submerged combustion heat sources.
In the FIG. 3 arrangement, the submerged combustion heat source is above the LNG heat transfer surface area. The products of combustion do not impinge or contact the surface area. The pump provides circulation of the heating medium rather than the products of combustion used in traditional submerged combustion LNG vaporizers for circulation.
FIG. 4 details an annular plate 33 connected to down corner plate 25. Annular plate 33 is located to provide a flow passage space between plate 33 and perforated plate 15. Annular plate 33 can also be provided as a plate with holes. The flow passage space between plates 15 and 33 provides area for heat and mass transfer contact between the products of combustion and the water to be heated as the water flows outward in a generally radial direction. The annular plate 33 can be installed in the submerged combustion system FIG. 1, FIG. 2 and FIG. 3 arrangements.
The submerged combustion system FIG. 1, FIG. 2 and FIG. 3 arrangements can include one or more of the following control functions (not shown in the figures):
- Control means for varying the heated water outlet flow. Control means for varying the flow can include valves, weirs and variable flow pumps.
- Control means for varying the inlet water flow. Control means for varying the flow can include valves, weirs and variable flow pumps.
- In circulating loop and other applications, control means are employed to maintain the loop water volume or change to a new operating level. If the water volume is increasing or a lower operating level is required, water is discharge water from the loop to obtain the desired water level. If the level is decreasing, make-up water is added to obtain the desired level. Water can also be utilized for cooling when operating in the turndown mode.
- Control means to maintain the water levels within operating limits.
- Burner control system including temperature control.
Additional operational, safety and shutdown functions are included in the submerged combustion control systems.
The submerged combustion water heater can include several arrangements and variations. Variations and arrangements can include one of more of the following:
- Water can be sprayed or injected into the products of combustion resulting in the production of steam and cooling of the products of combustion.
- Baffles can be positioned in the heated water plenum to assist in the removal of bubbles and entrainment in the heated water.
- Providing refractory insulation on the combustion chamber.
- Providing means to reduce the quantity of liquid droplets leaving via the stack.
- Providing means to control and maintain the pH of the water and solutions within the heater.
- Providing means to improve the air quality emissions from the heater.
- Contacting the products of combustion with a water spray before the products of combustion are vented to atmosphere to increase the heater efficiency.
- Where the fluids to be heated include particulate matter.
The FIG. 1, FIG. 2 and FIG. 3 arrangements can accommodate water flows which vary in an operating range above and below the design water flow. At higher water flows, the pressure in the down corner 23 increases, resulting in an increased water orifice opening 24 exit velocity and increased velocity of water flowing across the perforated plate 15. At lower flows the water orifice opening 24 exit velocity would decrease and decrease the velocity of water flowing across perforated plate 15. The burner would turn down to maintain the required water outlet temperature.
The submerged combustion system has design flexibility and scalability to adapt to the requirements of the application. The submerged combustion heater can be used for many commercial and industrial applications. Some applications require modification of the outlet plenum system. The submerged combustion system used for snow melting would have a pan located to accept and melt snow. Other shapes can also be utilized to configure the submerged combustion system. They may not be as scaleable as the cylindrical arrangement or provide the uniform distribution obtainable with the cylindrical arrangement.
The heater has installation flexibility. It can be installed below grade, above grade or partly below grade. It can be located onshore and on offshore platforms.
Aqueous and other solutions can be concentrated in the apparatus. The submerged combustion temperature is adjusted to vaporize water or other fluids. The vaporized product leaves via the stack. Provisions can be included to recover vaporized product from the stack gases. The solution remaining in the apparatus is concentrated.
The burner assembly is located in a dry area firing into a large combustion chamber. The large combustion chamber can accommodate a single high capacity, high efficiency, low horsepower, low pressure burner assembly. The low pressure and low submergence in the contact zone and other features of the submerged combustion system reduce the potential for apparatus vibration. The combustion chamber can also accommodate multiple burners. The unique water and products of combustion flow and contact arrangement permits the use of conventional low backpressure type burner assemblies. The burner assembly backpressure would generally be less than one pound per square inch.
The conventional burner assembly used in the invention can more readily meet air quality regulations than the high back pressure submerged combustion burner system. Several means are available to reduce the products of combustion emissions from the submerged combustion burner system. A high performance burner can provide reduced emissions. A further reduction can be obtained by recirculating products of combustion to the burner assembly to reduce the SCV emissions. A products of combustion stream from the flue plenum or flue stack can be recirculated to the burner. The high efficiency submerged combustion heat source produces cool products of combustion in the flue plenum and the flue stack. The cool products of combustion can be recirculated to the burner system. Some applications may require that the cool products of combustion be heated before being recirculated to the burner. The cool flue gas can be heated by indirect heat exchange with the hot products of combustion. In another system the cool flue gas can be heated by blending a portion of the hot products of combustion with the cool flue gas to produce the required gas temperature for recirculation. Another system would use cool products of combustion or flue gas from an external source to lower the SCV emissions. The external source of flue gas could be a gas turbine or another type of fired facility. The arrangement using an external flue gas source could increase the overall energy efficiency of the combined system.
At start-up, the submerged combustion system water flow is established before the burner is started. It is not necessary for the air blower to displace water from a portion of the apparatus before the burner is fired as required by many submerged combustion systems. The time required for burner start-up is low. The total start-up is low. The water flow configuration of the submerged combustion system provides water heating with low pressure drop in the water to be heated circuit.
Features
Several features of this invention Follow:
- The unique gas and water flow arrangement provides an effective means for heat and mass transfer surface area contact between water and the products of combustion.
- The burner start-up sequence can proceed without the air blower displacing water. The submerged combustion system can be quickly and easily started and shutdown.
- The combustion gas system is configured to operate with low back pressure. The combustion chamber and burner operate at low pressure. The combustion air blower has low installed horsepower.
- The submerged combustion apparatus can provide the heat for a complete system for vaporizing LNG and heating and vaporizing other fluids.
- The submerged combustion system facilitates the installation of high efficiency, high capacity, single burners.
- The low backpressure, low submergence heating system has less potential for apparatus vibration.
- The low pressure burner/combustion chamber arrangement can more readily meet air quality regulations.
- The submerged combustion system can be configured for circulating loop applications and configured for once through heating applications.
- The submerged combustion system can concentrate solutions.
- The submerged combustion heater can be used for many commercial and industrial applications.
- The heater has installation flexibility. It can be installed below grade, above grade or partly below grade. It can be located onshore and on offshore platforms.
- The heater provides fluid heating with low pressure drop in the fluid to be heated circuit.
Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the apparatus may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which come within the scope of the appended claims is reserved.
Patent Application
20050103323
