US20140150650A1

US20140150650A1 - Gas-To-Liquid Heat Exchanger and Gas Particulate Scrubber

Info

Publication number: US20140150650A1
Application number: US13/692,316
Authority: US
Inventors: Steven J. Walker
Original assignee: New England Wood Pellet LLC
Current assignee: New England Wood Pellet LLC
Priority date: 2012-12-03
Filing date: 2012-12-03
Publication date: 2014-06-05

Abstract

A gas-to-liquid heat exchanger is presented, where a gas is introduced directly to liquid. The liquid is exposed to the gas as a liquid film upon a series of rotating heat exchange surfaces partially submerged in a liquid reservoir. The liquid vaporizes and then re-condenses on subsequent heat exchange surfaces, such that heat is exchanged between the gas and the liquid. Particulates within the gas coalesce into the vaporized liquid and collect into the liquid reservoir as the vapor re-condenses.

Description

FIELD OF THE INVENTION

The present invention relates to heat exchangers, and more particularly, is related to a gas-to-liquid heat exchanger that also has the capacity to handle particulate-laden gas (dirty gas).

BACKGROUND

A heat exchanger transfers heat from one medium to another. Examples of heat exchangers include gas-to-gas, gas-to-liquid, and liquid-to-liquid. The media may be separated by a solid barrier of a heat conducting material, so that they never mix, or they may be in direct physical contact. Heat exchangers are used for space (or process) heating and/or cooling, for example, in power plants, or chemical plants.
Shell and tube heat exchangers consist of a series of tubes. The tubes contain a first fluid to be either heated or cooled. A second fluid runs over the tubes that are being heated or cooled so that the second fluid can either provide heat to the first fluid or absorb the heat from the first fluid as required.
FIG. 1 shows a shell and tube heat exchanger in the context of a prior art pressurized boiler 100. Fuel is burned by a burner 110, and hot exhaust gas from the burner 110 enters an ingress chamber 160 of a water vessel 120 through a burner exhaust vent 115. The water vessel 120 is substantially filled with water. The hot exhaust gas then passes through air-to-water heat exchanger tubes 130, where heat from the hot exhaust gas is transferred to water in the water vessel 120. The exhaust gas then enters an egress chamber 170, before being expelled from the boiler 100 through an exhaust vent 150. In some cases, the vented exhaust gas is still hot, so some energy from the combustion process is not utilized by the boiler 100. This results in a lower efficiency heating system.
In the pressurized boiler 100, the heated water is pumped directly from the water vessel 120 through a hot water outlet 190 and circulated through hot water pipes, where the heat from the hot water is conveyed to warm the environment, for example by water filled radiators or radiant floor heating tubes. The water circulates through the heating system, and then is returned to the water vessel in the boiler through a cold water inlet 180. In a pressurized boiler the temperature of the return water may impact factors such as the efficiency of the boiler 100.
The water used for space heating is typically heated to a temperature in excess of the temperature needed for domestic hot water. Therefore, a domestic hot water coil 140 may circulate water through the water vessel 120 of the boiler 100 for domestic hot water use. Note that the water circulating in the domestic hot water system is typically separate from the water within the boiler water vessel: the domestic hot water is heated by circulating the domestic water through the domestic hot water coil 140 within the boiler water vessel 120. Therefore, the domestic hot water system may generally operate at lower pressures than the boiler system.
Another type of heat exchanger is a plate heat exchanger, which may be composed of multiple, thin, slightly-separated plates that have very large surface areas and liquid flow passages for heat transfer. This stacked-plate arrangement can be more effective, in a given space, than a similarly sized shell and tube heat exchanger.
A liquid heat exchanger typically forces a gas upwards through a shower of liquid, for example, water, and the liquid is then conveyed elsewhere for cooling. This is commonly used for cooling gases whilst also removing certain impurities, thus solving two problems at once. For example, a liquid heat exchanger is used in espresso machines as an energy-saving method of cooling super-heated water to be used in the extraction of espresso. However, transporting cool water to hot gasses in general requires a considerable amount of energy. Also, in some circumstances, for example, a traditional boiler, the liquid heat exchanger is contained within a pressurized housing, to contain the expansion of vapor as the water boils. The pressurized housing adds significant cost, bulk and weight to the heat exchanger.
Pollutants may be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made. Particulates, alternatively referred to as particulate matter (PM) or fine particles, may be particles of solid or liquid suspended in a gas. Activities such as burning fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of particulates.
Several approaches are commonly used to capture particulates in pollution control devices by industry or transportation devices. Pollution control devices may either destroy contaminants or remove them from an exhaust stream before it is emitted into the atmosphere. Examples of particulate control devices include mechanical collectors, such as dust cyclones, electrostatic precipitators, baghouses and particulate scrubbers.
An electrostatic precipitator (ESP), or electrostatic air cleaner is a particulate collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are filtration devices that minimally impede the flow of gases through the device, and remove fine particulate matter such as dust and smoke from the air stream. Baghouses are designed to handle heavy dust loads, a dust collector consists of a blower, dust filter, a filter-cleaning system, and a dust receptacle or dust removal system (distinguished from air cleaners which utilize disposable filters to remove the dust).
Particulate scrubbers, or wet scrubbers, include a variety of devices that remove pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, typically by spraying the gas stream with the liquid, or by forcing the gas stream through a pool of liquid, so as to remove the pollutants. Examples of wet scrubbers include baffle spray scrubbers, cyclonic spray scrubbers, ejector venturi scrubbers, and mechanically aided scrubbers.
Spray towers or spray chambers generally consist of empty cylindrical vessels made of steel or plastic and nozzles that spray liquid into the vessels. The inlet gas stream usually enters the bottom of the tower and moves upward, while liquid is sprayed downward from one or more levels. This flow of inlet gas and liquid in the opposite direction is called countercurrent flow. Countercurrent flow exposes the outlet gas with the lowest pollutant concentration to the freshest scrubbing liquid. Many nozzles are placed across the tower at different heights to spray the gas as it moves up through the tower. Reasons for using many nozzles include maximizing the number of fine droplets impacting the pollutant particles and providing a large surface area for absorbing gas.
Baffle spray scrubbers are similar to spray towers in design and operation. However, in addition to using the energy provided by the spray nozzles, baffles are added to allow the gas stream to atomize some liquid as it passes over them. In a simple baffle scrubber system, liquid sprays capture pollutants and also remove collected particles from the baffles. Adding baffles slightly increases the pressure drop of the system.
An ejector or venturi scrubber is an industrial pollution control device, usually installed on the exhaust flue gas stacks of large furnaces, but may also be used on any number of other air exhaust systems. An ejector venturi scrubber uses a preformed spray, like a spray tower. The difference is that only a single nozzle is used instead of many nozzles in a spray tower. This nozzle operates at higher pressures and higher injection rates than those in most spray chambers. The high-pressure spray nozzle is aimed at the throat section of a venturi constriction. The ejector venturi is distinct among available scrubbing systems since it may move the process gas without the aid of a blower or fan.
In addition to using liquid sprays or the exhaust stream, mechanically aided scrubbing systems may use a motor to supply energy. The motor drives paddles which, in turn, generate and introduce water droplets into gas for particle collection. Mechanically aided scrubbers have the advantage of requiring less space than other scrubbers, but their overall power requirements tend to be higher than other scrubbers of equivalent efficiency. Significant power losses may occur in driving the paddles. Therefore, not all the power used is expended for gas-liquid contact. Examples of mechanically aided scrubbers include centrifugal fan scrubbers and mechanically induced spray scrubbers. Disadvantages of mechanically aided scrubbers include their generally high maintenance requirements, low absorption efficiency, and high operating costs.
However, many of the particulate control solutions are energy use intensive, and do not attempt to re-claim energy from the waste gasses. Similarly, heat exchangers may not remove particulates from exhaust gas. Therefore, there is a need in the industry to address the shortcomings described above.

SUMMARY

Embodiments of the present invention provide a gas-to-liquid heat and gas particulate scrubber exchanger system and method. Generally described in architecture, a first aspect of the present invention is directed to a heat exchanger. The heat exchanger includes a reservoir chamber having a liquid reservoir and a gas channel in contact with the liquid reservoir. The gas channel has a gas ingress side and a gas egress end, with the gas egress end disposed substantially opposite the gas ingress end. The liquid reservoir is in communication with a liquid ingress port and a liquid egress port.
The heat exchanger includes a rotating shaft having a first heat exchange surface in rigid rotational accompaniment with the rotating shaft. The rotating shaft is disposed within the reservoir chamber such that the first heat exchange surface is partially submerged in the liquid reservoir and is partially within the gas channel. The rotating shaft is oriented to at least partially span the reservoir chamber gas channel from the gas ingress end to the gas egress end. Gas flows in a gas flow direction from the gas ingress end to the gas egress end, and the liquid flows in a liquid flow direction from the liquid ingress end to the liquid egress end.
Generally described in architecture, a second aspect of the present invention is directed to a device, including a housing, a reservoir chamber, a rotating shaft and a driver connected to the rotating shaft. The reservoir chamber is disposed within the housing, and includes a liquid reservoir and a gas channel in contact with the liquid reservoir. The gas channel includes a gas ingress end and a gas egress end, with the gas egress end disposed substantially opposite the gas ingress end.
The rotating shaft includes a heat exchange surface disposed to rotate around the rotating shaft in rigid accompaniment with the rotating shaft. The rotating shaft is disposed within the reservoir chamber such that the heat exchange surface is partially submerged in the liquid reservoir and partially within the gas channel. The rotating shaft is oriented to span at least a portion of the reservoir chamber gas channel from the gas ingress end to the gas egress end. The driver connected to the rotating shaft is configured to rotate the rotating shaft.
Generally described, a third aspect of the present invention is directed to a method for exchanging heat between a gas and a liquid. The method includes the steps of providing a reservoir chamber having a housing, a liquid reservoir and a gas channel in communication with the liquid reservoir and further in communication with the housing, the gas channel having a ingress end and an egress end, introducing a gas into the gas channel ingress end, providing a rotating shaft at least partially spanning the reservoir chamber, providing a first heat exchange surface disposed upon the rotating shaft, the first heat exchange surface configured to rotate in rigid conformity with the rotating shaft, partially submerging the first heat exchange surface in the liquid reservoir, rotating the rotating shaft, thereby partially coating the first heat exchange surface with a liquid film, and expelling the gas from the gas channel egress end.
Generally described, a fourth aspect of the present invention is directed to a method for removing particulates from a gas. The method includes the steps of drawing a gas having particulates through a reservoir chamber partially filled with a liquid, within the reservoir chamber, rotating a first heat exchange surface partially submerged in the liquid, wherein the first heat exchange surface has a rotation axis configured to rotate at least a portion of the heat exchange surface through the liquid, partially coating the first heat exchange surface in the liquid, introducing the gas to the first heat exchange surface in the reservoir chamber, and collecting particulates from the gas in the liquid.
The method under the fourth aspect may further include the steps of vaporizing the liquid partially coating the first heat exchange surface, thereby producing a vapor, and coalescing the particulates into the vapor. The method may also include the steps of, within the reservoir chamber, rotating a second heat exchange surface, wherein the second heat exchange surface is partially submerged in the liquid, drawing the vapor through the reservoir chamber toward from the first heat exchange surface toward the second heat exchange surface in a first direction, introducing the vapor to the second heat exchange surface, and condensing the vapor upon the second heat exchange surface.
Other systems, methods and features of the present invention will be or become apparent to one having ordinary skill in the art upon examining the following drawings and detailed description. It is intended that all such additional systems, methods, and features be included in this description, be within the scope of the present invention and protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principals of the invention.

FIG. 1 is a diagram of a heat exchanger within a prior art boiler.

FIG. 2 is a diagram of the first embodiment of a heat exchanger deployed within an atmospheric boiler.

FIG. 3 is a diagram of a second embodiment of a heat exchanger deployed within an atmospheric furnace.

FIG. 4 is a cutaway diagram of a third embodiment of a heat exchanger and/or gas particulate scrubber.

FIG. 5 is a is a non-cutaway diagram of a third embodiment of a heat exchanger and/or gas particulate scrubber.

FIG. 6 is a diagram of rotating heat exchange surfaces in isolation.

FIG. 7A is a diagram of a fourth embodiment of a heat exchanger and/or gas particulate scrubber.

FIG. 7B is a cutaway diagram of a fourth embodiment of a heat exchanger and/or gas particulate scrubber.

FIG. 8 is a flowchart of an exemplary method for exchanging heat between a gas and a liquid.

FIG. 9 is a flowchart of an exemplary method for removing particulates from a gas.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
Exemplary embodiments of a low pressure heat exchanger are presented, where gasses are introduced directly to liquid. The liquid is exposed to the gasses as a film upon a series of rotating discs partially submerged in a reservoir. The liquid may vaporize and then re-condense on subsequent discs, exchanging heat between the gas and the reservoir liquid. The heat exchanger liquid may collect particulate matter from the gas, thereby scrubbing particulates from the gas.

Hot Water Space Heating System

FIG. 2 shows a first embodiment of a heat exchanger deployed in an atmospheric space heater 200. Fuel combusts in a burner 210, and the hot exhaust gas is introduced to a reservoir chamber 225, the hot exhaust gas passing from the burner 210 to the reservoir chamber 225 through a burner exhaust vent 215. The burner 210 may burn several types of fuel, for example, but not limited to, oil, natural gas, wood, wood pellets, coal and propane. It should be noted that in general, within this document a pressurized vessel refers to a vessel intended to withstand the pressure of fluid expansion due to temperature/state changes, in addition to static pressure, where the vessel must merely withstand the pressure of a fluid due to gravity and atmosphere at a fixed temperature.
The liquid used in the first embodiment is water. The reservoir chamber 225 is partially filled to a water line 205 with water. Unlike prior art boilers 100 (FIG. 1), the reservoir chamber 225 is not sealed or under pressure, but instead is unpressurized, having a vent such as exhaust gas vent 250 open to the exterior of the heater 200. Similarly, the air in the reservoir chamber 225 may be open to the burner exhaust vent 215, so that gas can pass freely between the burner 210 and the reservoir chamber 225.
A rotating shaft 265 is connected to a motor 270, so that the motor 270 rotates the rotating shaft 265. A plurality of heat exchange surfaces, which are implemented as discs 260 in the first embodiment, are attached to the rotating shaft 265 so that the rotating shaft 265 passes substantially through the center of each disc 260. The discs 260 are affixed to the rotating shaft 265 so that the discs 260 rotate in rigid accompaniment with the rotating shaft 265. The rotating shaft 265 is disposed above the water line 205 so that the rotating shaft is substantially parallel to the water line 205, and the discs 260 are partially submerged.
The discs 260 in the first embodiment are substantially circular, but there is no objection to other shapes used as heat exchange surfaces, such as ovals, octagons or hexagons, for example. The heat exchange surfaces need not be flat and may have irregular shapes, as increased surface area may assist in transference of heat between the gas and the liquid. For example, there is no objection to a fibrous material such as steel wool used as a heat exchange surface.
As the rotating shaft 265 rotates, the discs 260 turn through the water, so that the portion of the disc 260 that is submerged emerges from the water with a thin film of water upon the surface of the disc 260. The surface of disc 260 may be textured or scored, so that the action of rotating the discs draws more water from the reservoir. For example, there may be dimples, cuts, or slits in the discs 260 so the rotating discs 260 pick up and disperse the water, and maintain a film of water on the discs 260. In addition, the rotating discs 260 may introduce droplets of water into the air above the water line 205. The discs may be rotating at a relatively slow speed to minimize energy usage, for example, at approximately 150 RPM. Faster or slower disc rotation speeds are also possible. The discs 260 may be formed of a heat resistant material such as plastics, stainless steel, or other metals.
While in preferred embodiments the discs 260 are coated with water by rotating them through a reservoir of water, there is no objection alternative embodiments where discs 260 are coated with water by other mechanisms, for example, by spraying water on discs 260 with a spray nozzle, dripping water on discs 260, splashing water on the discs 260, brushing or sponging water on the discs 260, or other mechanisms. These mechanisms may also serve to apply water to other surfaces in addition to the discs 260 themselves, for example, the interior surface of the reservoir chamber 225.
An exhaust fan (not shown) draws airflow from the burner 210, through the burner exhaust vent 215, through an air passage in the reservoir chamber 225 above the water line 205, and out through the exhaust gas vent 250. The hot burner exhaust gas is drawn from the burner 210 into the reservoir chamber 225, and introduced to the rotating discs 260. Note the motor 270 used to rotate the disc rotating shaft 265 may also be used to rotate the exhaust fan (not shown).
When the hot gas from the burner 210 encounters the film of water on the disc 260 closest to the burner exhaust vent 215, the water evaporates off of the disc 260, forming water vapor and cooling the gas. The fan draws the then cooler burner exhaust gas and the water vapor toward the second disc 260, where the water vapor encounters the cooler water film on the disc 260, causing at least a portion of the water vapor to re-condense, further cooling the vent exhaust gas while the re-condensed water enters the reservoir chamber 225 as hot water. This process may repeat as the exhaust gas is drawn toward the exhaust gas vent 250 and the exhaust gas is introduced to the water film on subsequent discs 260. In the first embodiment of the space heater, when the gas reaches the exhaust vent 250, the gas has generally been cooled to a temperature slightly above the temperature of the water in the reservoir chamber 225.
Since the water vapor is immediately re-condensed to hot water, it does not have to be maintained under pressure. By heating the water in an unpressurized, open boiler, the need for thick, heavy components compliant with industry standard codes and standards, such as ASME (American Society of Mechanical Engineers) BPVC (Boiler and Pressure Vessel Code), is reduced, as the water in the reservoir chamber 225 may be heated to a temperature sufficient for space heating purposes, but still significantly below boiling temperature. Therefore, the reservoir chamber may not need to withstand pressures of prior art boilers. As a result, the materials used to construct the reservoir chamber 225 may be much lighter weight and less expensive than the materials used for prior art boilers. For example, the walls of the reservoir chamber may be constructed of thin stainless steel, which may be structurally supported by insulation, as the primary force upon the reservoir walls is from the water in the reservoir chamber 225 under the force of gravity, rather than pressure generated by heating water into water vapor. In addition, the water in the reservoir chamber 225 may act to limit the temperature of the reservoir chamber walls, further allow use of lighter weight materials by reducing the need for thick insulating metal walls.
Under the first embodiment, most of the heat from the burner exhaust gas is transferred directly to the water in the reservoir chamber 225. The heated water in the reservoir chamber 225 may be used to heat external water sources for space heating and domestic hot water. For example, a domestic hot water coil 240 located in the reservoir chamber 225 below the water line 205 may be used to heat domestic hot water in a manner similar to prior art boilers 100 (FIG. 1).
Similarly, water may be introduced to a reservoir heat exchanger 230 to heat water for space heating purposes. Cold water may be introduced to the reservoir heat exchanger 230 through cold water inlet 280, and the water in the heat exchanger 230 may be heated by the water in the reservoir chamber 225 before exiting through a hot water outlet 290. Unlike traditional boiler heating systems, the return temperature of the water does not significantly impact the performance of the heater. For example, water returning to a pressurized boiler at a temperature below the condensing point of water, typically on the order of 140° F., could cause damage to the boiler. The reservoir heat exchanger 230 may be, for example, a water-to-water heat exchanger, thereby deriving its heat from the heated water in the reservoir chamber. Or, the reservoir heat exchanger 230 may be partially submerged below the water line 205, so that the water in the heat exchanger derives its heat in part from the water in the reservoir chamber 225, and in part from exposure to exhaust gas from the burner 210.
While the space heater 200 may not operate under pressures in excess of one standard atmosphere, the space water passing through the reservoir heat exchanger 230 may be under higher pressure than the water in the reservoir chamber 225. For example, the space water may be pressurized to force water through pipes upward to higher floors of the building from where the space heater 200 is located. Therefore, the system for pumping and circulating the space hot water may be pressurized and thus subject to ASME codes or other similar codes and standards for pressurized vessels. The circulation system may be constructed from heavier and more expensive materials to withstand the additional pressure. However, the pressurized part of the space heater 200 may represent a substantially smaller portion of the system than in prior art boilers, allowing the space heater to be constructed from less expensive materials, than materials used for a pressurized boiler.

Forced Hot Air System

FIG. 3 shows a second embodiment of a heat exchanger deployed within an atmospheric space heater 300. The second embodiment 200 is similar to the first embodiment 300 in that both heaters have a burner 210 that vents heated exhaust gas through a burner vent 215 into a reservoir chamber 225. An egress fan (not shown) draws exhaust from the burner 210 through the reservoir chamber 225. The hot exhaust gas encounters water film on discs 260 partially submerged below a water line 205, the discs 260 rotating on a rotating shaft 265, driven by a motor 270. The hot gas vaporizes the film of water on the first disc 260 closest to the burner vent 215, cooling the exhaust gas and forming a mixture of exhaust gas and water vapor. Similarly, the hot gas may vaporize the film of water on the second disc 260 and/or subsequent discs in the reservoir chamber. As the mixture of exhaust gas and water vapor is drawn through the reservoir chamber 225, the mixture encounters subsequent discs 260, where some of the water vapor is cooled, causing some of the water vapor to re-condense and enter the reservoir 225 as hot water.
It should be noted that while water vapor is recondensed within the reservoir chamber 225 in second embodiment, in alternative embodiments, the water vapor may be drawn from the reservoir chamber 225 to an external chamber (not shown), for example, a vapor-to-air heat exchanger, where the water vapor is recondensed in the external chamber (not shown). The recondensed water may be returned to the reservoir chamber 225, or the water in the reservoir chamber 225 may be replenished by another water source.
In the second embodiment, a vent 250 provides a conduit for hot water vapor to a hot air heater 380. The hot water vapor passes through a vapor-to-air heat exchanger 390, before exiting from a heat exchanger vent 350. The air heated in the heat exchanger 390 may then be forced through hot air conduits, as with a conventional hot air furnace. As with the first embodiment, a domestic hot water coil 240 may be exposed to the heated water in the reservoir 225.
Note that fewer discs 260 may be used for the second embodiment than the first embodiment, as the exhaust entering the air-to-vapor heat exchanger 390 may typically be hotter than the desirable temperature of gas emitted from the exhaust gas vent 250 (FIG. 2) in the first embodiment. Fewer discs 160 may therefore result in less cooling of the exhaust gas, and less heating of the water in the reservoir 225.

Particulate Removal and Ash Storage

In addition to providing direct heating of water in the reservoir chamber instead of indirectly heating the water in the chamber through a heat exchanger (prior art), the first embodiment space heater 200 (FIG. 2) and the second embodiment space heater 300 (FIG. 3) may also remove particulates from the burner 210 exhaust gas, for example, in a pellet burning system. The burner exhaust gas may carry fly ash into the reservoir chamber 225. As the exhaust gas encounters the water film on the discs 260, as well as the water vapor produced as the exhaust gas evaporates the water film and the droplets of water introduced to the air by the rotating discs, the fly ash in the exhaust gas may combine with the water. As the water vapor re-condenses, as described above, the re-condensing water carries the fly ash into the water in the reservoir chamber. Over time, the ash may tend to settle to the bottom of the reservoir chamber 225, as a layer of ash 207. As the discs 260 rotate, any ash that may accumulate on the disc 260 surface above the water line 205 is carried into the water, thus cleaning the discs.
As mentioned previously, prior art systems have used water pumped through spray nozzles to remove particulates from burner exhaust gas. The pump systems require significantly more energy to operate than the amount of energy required to draw the air through the reservoir chamber 225 and to rotate the discs 260. In addition, spray nozzles may become clogged with particulate matter, requiring either filtering of the water or cleaning of the nozzles.
In addition to accumulating fly ash in the reservoir chamber, heavy ash from the burner 210 may also be deposited in the reservoir chamber, forming an ash-water slurry. The reservoir chamber 225 may accumulate a significant amount of ash into the ash-water slurry before maintenance is required. The reservoir may be maintained, for example, by annual replacement of the water in the reservoir chamber 225. The ash-water slurry may then be disposed of, or processed to harvest chemicals for use in byproducts, for example, fertilizer, or a soil de-acidifying agent.

Gas Particulate Scrubber

Under a third embodiment, the heat exchanger and particulate scrubber may similarly be used to remove particulates and reclaim energy from waste gasses, for example, when used as a smokestack scrubber. FIG. 4 shows a cutaway view of the third embodiment of a heat exchanger and/or particulate scrubber 400.
A liquid reservoir chamber, or housing 410 encloses a liquid reservoir and a gas channel. Gas in the gas channel is in direct physical contact with the liquid contained in the liquid reservoir. The housing 410 is shown as a cutaway view to partially display the interior of the housing 410. The interior of the housing 410 not otherwise containing liquid forms the gas channel. It should be noted that the gas-liquid interface within the housing 410 is not shown in FIG. 4 to more clearly show the other elements. Liquid may be added to the liquid reservoir through the liquid ingress port 420 (inlet), and liquid may be removed from the liquid reservoir through the liquid egress port 425 (outlet).
Liquid may flow through the housing 410, the liquid having a liquid flow direction from the liquid ingress port 420 to the liquid egress port 425. Similarly, gas may enter the gas channel of the housing 410 through the gas ingress port 430, and gas may exit the gas channel through the gas egress port 435. Gas may flow through the housing 410, the flow having a gas flow direction from the gas ingress port 430 to the gas egress port 435. It should be noted that while the gas flow direction is counter to the liquid flow direction in the third embodiment, there is no objection to alternative embodiments where the gas flow direction coincides with the liquid flow direction. Similarly, there is no objection to fluid having a first flow rate and gas having a second flow rate through the heat exchanger, where the first flow direction is different from the second flow direction.
A rotating shaft 440 may extend from the exterior of the housing 410, and pass through the interior of the housing 410. The rotating shaft 440 may pass entirely through the housing 410 in two locations, or may only pass through the housing 410 in one location. The rotating shaft 440 may pass through a bearing 450. In embodiments where the rotating shaft 440 passes through the housing 410 in two locations, there may be two bearings 450. While the bearing 450 in the third embodiment is external to the housing 410, there is no objection to the bearing 450 being internal to the housing 410 or for the bearing 450 to be integral with the housing 410. The rotating shaft 440 may further be connected to a driver (not shown), such as a motor, to drive the rotating shaft 440.
Within the housing 410 one or more heat exchange surfaces, in this embodiment shaped as discs 460, are attached to the rotating shaft 440 such that each disc 460 rotates in rigid accompaniment with the rotating shaft 450. A portion of each disc 460 is disposed within the liquid in the liquid reservoir, and the remainder of each disc 460 is in the gas channel. It may be desirable for up to half of each disc 460 be exposed to the gas channel. As the rotating shaft 440 rotates, each disc 460 also rotates, such that the submerged portion of each disc 460 rotates into the gas channel, thereby drawing liquid from the liquid reservoir to be exposed to the gas in the gas channel as a liquid coating of the disc 460. If the rotating shaft 440 is rotating quickly enough, the rotation of the discs 460 may fling droplets of liquid into the gas channel, some of which may spray against the interior of the housing 410, where the liquid spray drops may coalesce and drip back into the liquid reservoir, or flow along the interior of the housing 410 back into the liquid reservoir.
Each disc 460 may have one or more apertures 470, thereby facilitating flow of gas through the gas channel and/or liquid through the liquid channel. The apertures 470 may similarly facilitate the spraying action described above.
While discs 460 are generally flat and circular under the third embodiment, several variations in heat exchange surface shapes are also possible. For example, portions of each disc 460 may extend outward from the flat surface of the disc to facilitate the liquid spraying action described above. Similarly, the heat exchange surfaces may be shaped to assist in impelling gas through the gas channel and/or liquid through the liquid reservoir. In alternative embodiments, a drum (not pictured) may perform the heat exchange surface function of the disc 460. Further, there is no objection to having multiple heat exchange surfaces of different shapes and configuration within a single housing 410. For example, a first heat exchange surface 460 near the gas ingress port 430 may be shaped to better facilitate evaporation of liquid, while a second heat exchange surface 460 near the gas egress port 435 may be shaped to better facilitate coalescing of liquid.
FIG. 5 shows a non-cutaway view of the third embodiment of a heat exchanger and/or particulate scrubber 400, and FIG. 6 shows the rotating heat exchange surfaces 460 in isolation on the rotating shaft 440. Other embodiments within the scope of this disclosure include a housing 410 where stationary baffles (not shown) are positioned between adjacent discs 460, in the liquid reservoir and/or in the gas channel.
While the housing 410 in the third embodiment is depicted in FIG. 4 as substantially cylindrical in shape, having a circular cross section, there is no objection to configurations where the housing 410 is differently shaped, for example, having a rectangular cross section.
It may be desirable to monitor the level of liquid within the liquid reservoir, as condensation of additional liquid introduced to the housing 410 as liquid vapor in the gas may add to the overall volume of liquid in the system. Such additional liquid may then be purged from the system as needed.
Other variations may similarly be employed to remove particulates from gas within the gas channel. Under one variation, an electrostatic charge may be applied to one or more discs 460 to attract particulates in the gas that may be magnetically charged to the disc 460. Similarly, one or more discharge electrodes may be disposed between heat exchange surfaces, thereby imparting an electric charge to particulates in the gas and/or particulates collected within suspended liquid droplets. Such charged particles and/or droplets may then be attracted to collecting portions of the heat exchange surfaces in the gas channel, as per an electrostatic precipitator (ESP). The particulates may thereafter be introduced into the liquid reservoir as the collecting portions of the heat exchange surfaces rotate from the gas channel into the liquid reservoir.
In addition to advantages noted above, the third embodiment is advantageous in that it is self-cleaning Particulates collected upon discs 460 may be deposited from the disc 460 into the liquid reservoir. After the liquid is drawn from the liquid egress port 425, the liquid may be filtered to remove the particulates from the liquid. Coating rotating discs with fluid may consume less power than prior art mechanically aided scrubbers, as fluid generates less resistance to a disc rotating through fluid than, for example, a paddle pushing against fluid.
It should be noted that there is no objection to the function of the liquid ingress port 420 and the liquid egress port 425 being reversed, such that the port 420 serves as an egress port or drain, and the port 425 serves as an ingress port. It may be desirable for the ingress/egress port 425 and/or the ingress/egress port 420 be placed towards the bottom of the housing 410 in order to prevent buildup of non-liquid matter within the housing 410, for example, particulates.
In embodiments where water is used as the liquid, gas inlet temperatures may be in excess of 2000 degrees Fahrenheit. In such embodiments, hot gas will be converted to water vapor within a short distance from the gas ingress port 430. The rest of the distance between the gas ingress port 430 and the gas egress port 435 may generally function to condense the water vapor to extract the energy, while simultaneously removing significant quantities of particulates, such as fly ash in examples where combustion gasses are used.
FIGS. 7A and 7B show an exemplary fourth embodiment of a heat exchanger and/or particulate scrubber 700. The fourth embodiment is essentially similar to the third embodiment, with the addition of an indirect heat exchange coil 783 that may be disposed within the housing 410. The heat exchange coil may function similarly to a traditional boiler, where cool water enters an inlet 780 is heated by hot gasses and fluid as it passes through the housing 410, such that the water is warmer when it exits the heat exchanger 700 via an outlet 785. The heat exchange coil 783 may be positioned such that is mostly within the liquid reservoir. Alternatively, heat exchange coil 783 may be positioned such that is mostly above the liquid reservoir, such that the heat exchange occurs between the heated gas and the fluid within the heat exchange coil 783. As shown in FIG. 7B, the heat exchange coil 783 may be configured as a helix largely along the outer wall of the housing 410. Of course, other configurations of the indirect heat exchange coil 783 may also be considered within the scope of this disclosure. Note there is no objection to reversing the function of the inlet 780 and the outlet 785, such that the cooler fluid enters near the gas inlet 440 and exits near the gas outlet 435.

Methods

FIG. 8 is a flowchart of an exemplary method for exchanging heat between a gas and a liquid. It should be noted that any process descriptions or blocks in flow charts should be understood as representing modules, segments, portions of code, or steps that include one or more instructions for implementing specific logical functions in the process, and alternative implementations are included within the scope of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention.
The method includes the step of providing a reservoir chamber with a housing, a liquid reservoir and a gas channel, as shown by block 810. A rotating shaft spanning the reservoir chamber is provided with a heat exchange surface configured to rotate with the rotating shaft, as shown by block 820. The heat exchange surface is partially submerged in the liquid reservoir, as shown by block 830. The rotating shaft is rotated, thereby partially coating the heat exchange surface with a liquid film, as shown by block 840. Hot gas is introduced to the heat exchange surface, as shown by block 850. The hot gas transfers heat to the liquid and vaporizes the liquid. Cooled gas is expelled from the gas channel, as shown by 860.
FIG. 9 is a flowchart of an exemplary method for removing particulates from a gas. The method includes the step of drawing a gas comprising particulates through a reservoir chamber partially filled with a liquid, as shown by block 910. A heat exchange surface partially submerged in the liquid is rotated within the reservoir chamber, rotating a first heat exchange surface, as shown by block 920. The heat exchange surface is partially coated in the liquid, as shown by block 930. The gas is introduced to the heat exchange surface in the reservoir chamber, as shown by block 940. The liquid coating the heat exchange surface is evaporated by the hot gas, and liquid droplet surround and encompass particulates in the gas. Particulates from the gas are collected in the liquid, as shown by block 950.
In summary, an atmospheric, low maintenance heat exchange and particulate scrubbing method, system and apparatus are presented. Instead of bringing gas to liquid, the liquid is introduce to hot gas using partially submerged rotating heat exchange surfaces. Since the heat exchange occurs in an open, non-pressurized vessel, lighter and less expensive materials may be used compared with pressurized heat exchange systems.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.

Claims

What is claimed is:

1. A heat exchanger, comprising;

a reservoir chamber configured to contain a liquid reservoir and a gas channel in contact with said liquid reservoir, said reservoir chamber further comprising a gas ingress end and a gas egress end, a liquid ingress port and a liquid egress port; and

a rotating shaft comprising a first heat exchange surface in rigid rotational accompaniment with said rotating shaft, said rotating shaft disposed within said reservoir chamber such that said first heat exchange surface is configured to be partially submerged in said liquid reservoir and partially within said gas channel, said rotating shaft oriented to at least partially span said reservoir chamber gas channel.

2. The heat exchanger of claim 1, further comprising a driver configured to rotate said rotating shaft.

3. The heat exchanger of claim 1, further comprising a gas impeller in communication with said reservoir chamber gas channel.

4. The heat exchanger of claim 1, further comprising a liquid impeller in communication with said liquid reservoir.

5. The heat exchanger of claim 1, further comprising:

a driver connected to said rotating shaft such that said driver rotates said rotating shaft; and

a gas impeller in communication with said reservoir chamber gas channel,

wherein said driver connected to said rotating shaft is further configured to drive said gas impeller.

6. The heat exchanger of claim 1, wherein said first heat exchange surface further comprises an aperture.

7. The heat exchanger of claim 1, wherein said first heat exchange surface further comprises an impeller.

8. The heat exchanger of claim 1, further comprising a second heat exchange surface in rigid rotational accompaniment with said rotating shaft, said second heat exchange surface disposed substantially parallel to said first heat exchange surface.

9. The heat exchanger of claim 8, further comprising a stationary baffle disposed substantially between said first heat exchange surface and said second heat exchange surface

10. The heat exchanger of claim 1, wherein the first heat exchanger comprises a substantially flat first disc.

11. The heat exchanger of claim 1, further comprising an indirect heat exchange coil disposed within said reservoir chamber, wherein said reservoir chamber further comprises a heat exchange coil inlet and a heat exchange coil outlet.

12. A device, comprising;

a housing;

a reservoir chamber disposed within said housing configured to contain a liquid reservoir and a gas channel in contact with said liquid reservoir, said reservoir chamber further comprising a gas ingress end and a gas egress end;

a rotating shaft comprising a heat exchange surface disposed to rotate around said rotating shaft in rigid accompaniment with said rotating shaft, said rotating shaft disposed within said reservoir chamber, said rotating shaft oriented to span at least a portion of said reservoir chamber gas channel; and

a driver connected to said rotating shaft, said driver configured to rotate said rotating shaft.

13. The device of claim 12, further comprising a reservoir chamber gas channel impeller configured to impel gas into said gas channel gas ingress end and expel gas from said gas channel gas egress end.

14. The device of claim 12, further comprising a baffle disposed within said reservoir chamber gas channel.

15. The device of claim 12, wherein said driver rotating shaft additionally configured to drive said gas channel egress impeller.

16. The device of claim 12, further comprising an electrode configured to form an electric field within said gas channel.

17. The device of claim 12, further comprising an indirect heat exchange coil disposed within said reservoir chamber, wherein said reservoir chamber further comprises a heat exchange coil inlet and a heat exchange coil outlet.

18. A method for exchanging heat between a gas and a liquid, comprising the steps of:

providing a reservoir chamber comprising a housing, a liquid reservoir and a gas channel in communication with said liquid reservoir and further in communication with said housing, said gas channel having a ingress end and an egress end;

providing a rotating shaft at least partially spanning said reservoir chamber;

providing a first heat exchange surface disposed upon said rotating shaft, said first heat exchange surface configured to rotate in rigid conformity with said rotating shaft;

partially submerging said first heat exchange surface in said liquid reservoir;

rotating said rotating shaft, thereby partially coating said first heat exchange surface with a liquid film; and

introducing a gas through said gas channel ingress end to said first heat exchange surface;

expelling said gas from said gas channel egress end.

19. The method of claim 18, further comprising the step of flinging said liquid from said first heat exchange surface onto said housing.

20. A method for removing particulates from a gas, comprising the steps of:

drawing a gas comprising particulates through a reservoir chamber partially filled with a liquid;

within said reservoir chamber, rotating a first heat exchange surface partially submerged in said liquid;

partially coating said first heat exchange surface in said liquid;

introducing said gas to said first heat exchange surface in said reservoir chamber; and

collecting particulates from said gas in said liquid.

21. The method of claim 20, further comprising the steps of:

vaporizing said liquid partially coating said first heat exchange surface, thereby producing a vapor; and

coalescing said particulates into said vapor.

22. The method of claim 21, further comprising the steps of:

within said reservoir chamber, rotating a second heat exchange surface, wherein said second heat exchange surface is partially submerged in said liquid;

drawing said vapor through said reservoir chamber toward from said first heat exchange surface toward said second heat exchange surface in a first direction;

introducing said vapor to said second heat exchange surface; and

condensing said vapor upon said second heat exchange surface.

23. The method of claim 20, further comprising the step of imparting an electrostatic charging of a first polarity to said particulates within the gas.

24. The method of claim 23, further comprising the step of electrostatically charging said first heat exchange surface with a second polarity.