US20120017591A1

US20120017591A1 - Simultaneous production of electrical power and potable water

Info

Publication number: US20120017591A1
Application number: US13/008,883
Authority: US
Inventors: Philip D. Leveson; John P. Gaus
Original assignee: Individual
Current assignee: ZeroPoint Clean Tech Inc
Priority date: 2010-01-19
Filing date: 2011-01-18
Publication date: 2012-01-26
Also published as: WO2011091072A2; WO2011091072A3

Abstract

Biomass or refuse-derived fuels (10) and seawater or other non-potable water are used as an input to a combustor/evaporator (15, 20). The resulting steam heats a working fluid in an Organic Rankine Cycle (30, 50, 60, 75) process which drives a turbine (50) to produce mechanical rotation. This rotation can be used to directly drive a process or to generate electricity. The heating of the working fluid cools the steam to produce purified water. The evaporator provides a water purification process for both the separation of dissolved components as well as providing for thermal pasteurization/sterilization. Suitable water inputs are seawater, brackish water and water with those waterborne diseases and pathogens which can be killed through pasteurization/sterilization.

Description

PRIORITY CLAIM

This application claims the priority of U.S. Provisional Patent Application Ser. No. 61/296,142, filed Jan. 19, 2010, entitled “Simultaneous Production Of Electrical Power And Potable Water”.

FIELD OF THE INVENTION

The present invention relates to a process to produce both potable water and electrical power.

BACKGROUND OF THE INVENTION

Nearly a billion people worldwide do not have access to clean water and one quarter of the earth's human population does not have access to electricity. The vast majority of the people that live without clean water and electricity are located in rural areas of the developing world. In addition, it is often impractical to build or reliably operate even a small oil-fired or coal-fired power plant or water purification plant because it may be difficult or even impossible to transport these oil or coal fuels to a power plant or a purification plant in such rural areas because of the distance or terrain involved. Often, the sole fuels available in these areas are locally available biomass fuels or wastes. Further, even in those countries that do normally have potable water and electricity, such necessities can be disrupted, briefly or for extended periods, by natural disasters such as hurricanes, earthquakes, flooding, landslides, and tidal waves.

SUMMARY OF THE INVENTION

An apparatus which both generates power and purifies water is disclosed. The apparatus includes a combustion chamber, a boiling tank, a preferred, but optional, plurality of heat exchange tubes, an exhaust conduit, an evaporator, a turbine, a condenser, and a pump. The combustion chamber burns fuel to provide heat via combustion products, and has a fuel input port. The boiling tank has a water input port and a steam output port. The preferred, but optional, heat exchange tubes are connected in parallel, and are functionally connected to the combustion chamber to receive the combustion products. The tubes are at least partially inside the boiling tank and transfer heat from the combustion products to the water in the boiling tank to produce steam. Alternatively, the heat from the combustion products can be used to directly heat the boiling tank. The exhaust conduit, such as a chimney, discharges combustion products which have flowed through the heat exchange tubes. The evaporator transfers heat from the steam to an Organic Rankine Cycle (ORC) working fluid to evaporate the ORC working fluid to produce a high pressure ORC vapor and to condense the steam to provide purified or potable water. The evaporator has a steam input port functionally connected to the steam output port of the boiling tank to receive the steam, a condensate port for discharging the purified or potable water, a working fluid input port to receive the working fluid, and a vapor output port for discharging the high pressure ORC vapor. The turbine produces mechanical power from the high pressure ORC vapor. The turbine has a high pressure vapor input port functionally connected to the evaporator to receive the high pressure ORC vapor, and a low pressure vapor output port to discharge a low pressure ORC vapor. The condenser transfers heat from the low pressure ORC vapor to a cooling fluid to condense the low pressure ORC vapor to produce an ORC working fluid. The condenser has a low pressure vapor input port functionally connected to the low pressure vapor output port of the turbine for receiving the low pressure ORC vapor, an ORC working fluid condensate output port for discharging the ORC working fluid, a cooling fluid input port to receive the cooling fluid, and a cooling fluid output port to discharge the cooling fluid. The pump provides the ORC working fluid to the evaporator. The pump has an ORC working fluid input port functionally connected to the ORC working fluid condensate output port, and an ORC working fluid output port functionally connected to the working fluid input port of the evaporator.
A method which both generates power and purifies water is disclosed. The method includes burning a fuel to provide a hot gas, transferring heat from the hot gas to convert water into steam, transferring heat from the steam to convert an Organic Rankine Cycle (ORC) working fluid into a high pressure ORC vapor and to provide condensate from the steam as purified or potable water, providing the high pressure ORC vapor to a turbine to generate power and to provide a low pressure ORC vapor, cooling the low pressure ORC vapor to provide an ORC working fluid condensate, and pumping the ORC working fluid condensate to be used as the ORC working fluid.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic block diagram of an exemplary embodiment of a water purification and sterilization and power generation system.

FIG. 2 is a schematic block diagram of an exemplary embodiment of a combustion chamber and evaporation system.

DETAILED DESCRIPTION OF THE INVENTION

Biomass, refuse-derived fuels, and construction debris-derived fuels are used as an input to a water desalination/purification and electrical generation process. The water purification process is suitable for both the separation of dissolved components as well as the thermal pasteurization/ sterilization of the water. Suitable water inputs are seawater, brackish water and even water containing those waterborne diseases and pathogens which can be killed through pasteurization/sterilization.
Biomass or carbon-containing feeds are combusted in a boiler. The heat of combustion is used to evaporate water from a saline, brackish, or contaminated water source. The resulting steam is used as a heat input into an Organic Rankine Cycle (ORC) and the condensed steam is then collected for use as potable water. The ORC can drive a turbine which, in turn, drives a generator which can produce electrical power. Also, the rotation of the turbine can be used directly as mechanical energy into a direct drive application such as, but not limited to, pumping water.
Turning now to FIGS. 1 and 2, a power generation and water purification and sterilization apparatus 5 preferably includes a combustion chamber 15, a boiling tank 20, a plurality of heat exchange tubes 23 (FIG. 2), an exhaust conduit 27, an evaporator 30, a turbine 50, a condenser 60, and a pump 75.
The combustion chamber 15 burns fuel to provide heat energy via combustion products, and has a fuel input port 14.
The boiling tank 20 has a water input port 21 and a steam output port 22.
The heat exchange tubes 23 are connected in parallel, and are connected to the combustion chamber to receive the combustion products. The tubes are at least partially inside the boiling tank, are at least partially submerged in the water in the tank, and transfer heat from the combustion products to the water in the boiling tank to produce steam.
The exhaust conduit 27, such as a chimney, discharges combustion products which have flowed through the heat exchange tubes.
The evaporator 30 transfers heat from the steam to an Organic Rankine Cycle (ORC) working fluid to evaporate the ORC working fluid to produce a high pressure ORC vapor and to condense the steam to provide potable water. The evaporator 30 has a steam input port 31 connected via a steam line 25 to the steam output port 22 of the boiling tank to receive the steam, a condensate output port 32 for discharging the potable water, a working fluid input port 33 to receive the working fluid, and a vapor output port 34 for discharging the high pressure ORC vapor.
The turbine 50 produces mechanical power from the high pressure ORC vapor. The turbine is preferably, but not necessarily, a centrifugal, rotary lobe, or rotary screw turbine. The turbine has a high pressure vapor input port 51 connected via an ORC vapor high pressure line 45 to the evaporator to receive the high pressure ORC vapor, and a low pressure vapor output port 52 to discharge the ORC vapor, which will be at a low pressure after transferring its energy to the turbine.
The condenser 60 receives the low pressure ORC vapor and transfers heat from the low pressure ORC vapor to a cooling fluid to condense the low pressure ORC vapor to produce an ORC working fluid. The condenser 60 has a low pressure vapor input port 61 connected to the low pressure vapor output port 52 of the turbine via an ORC vapor low pressure line 55 for receiving the low pressure ORC vapor, an ORC working fluid condensate output port 62 for discharging the ORC working fluid, a cooling fluid input port 63 to receive the cooling fluid, and a cooling fluid output port 64 to discharge the cooling fluid. If the cooling fluid is water then the condenser is preferably, but not necessarily, a shell and tube and plate heat exchanger. If the cooling fluid is air then the condenser is preferably, but not necessarily, a wet surface air cooler or an air fin cooler.
The pump 75 provides the ORC working fluid to the evaporator. The pump 75 has an ORC working fluid input port 76 connected to the ORC working fluid condensate output port 62, and an ORC working fluid output port 77 connected to the working fluid input port 33 of the evaporator.
FIG. 1 is a schematic block diagram of an exemplary embodiment of water sterilization and power generation system 5. Seawater or other non-potable water is provided via a water line 17 to the water input port 21 of a boiling tank, such as a desalinization evaporator 20. A biomass fuel 10 is provided to the fuel input port 14 of a combustion chamber, such as firebox 15. The fuel input port may be, for example, a hinged door or even just an opening in the side of the combustion chamber. The hot gas from the combustion chamber drives the boiling tank 20 to produce steam. Although almost any available fuel can be utilized as long as it combusts in an exothermic manner, the preferred fuel input to the process is biomass fuel, such as, but not limited to, biomass, biomass-derived fuel, or refuse-derived fuel. Examples of such fuels are sticks, leaves, brush, husks, stems, plants, logs, lumber as used as a building material, combustible debris, construction debris, etc. For example, after harvesting crops, there is a substantial amount of plant stems and husks available for use as fuel. As another example, after a natural disaster, such as a tornado, there is a substantial quantity of wood debris and other combustible debris readily available. The open nature of the firebox allows fuels with a large range of characteristic lengths and sizes to be used. This minimizes front end processing such as, pelletizing, chipping, or cutting to a specified size. If refuse-derived fuels (including, but not limited to, papers, cardboards, plastics, food wrappers and vegetable matter) are used, it may be advantageous, although not necessary, to coarsely briquette or pelletize the material to improve handling and/or combustion characteristics. Fuel with a wide range of moisture content also can be used, as long as it combusts in a net exothermic manner, thus minimizing the need for external drying of the fuel. It should be noted, however, that external drying increases the combustion characteristic of the fuel, and can reduce or slow the buildup of incomplete combustion products, such as tar and creosote, in the firebox, heat exchange tubes, and chimney. Use of local biomass fuel is advantageous in that it is generally available, costs less than processed fuels such as oil, gas, and coal, and does not require an extensive or specialized transportation system, such as pipelines or rail lines. It is also advantageous in that it provides a facility for useful disposal of such biomass, that is, in creating potable water and power. Otherwise, the biomass would be disposed of in a landfill, burned simply to dispose of it, or simply left in a pile somewhere to rot or decay, none of which are environmentally-friendly approaches.
FIG. 2 is a schematic block diagram of an exemplary embodiment of a combustion chamber 15 and evaporation system 20. The biomass input 10 is combusted in a front end “firebox” or combustion chamber 15. The products of combustion, primarily hot gas and ash, then pass through a saline boiling tank 20 via a plurality of heat transfer (HX) tubes 23 which are submerged in the water to be purified. The tank 20 has an input port 21 for receiving the water via water line 17. After passing through the heat transfer tubes the at least partially cooled products of combustion are vented to the atmosphere through a conduit, such as a chimney 27.
In an alternative embodiment (not shown), the heat exchange tubes are not used but, instead, the heat of the combustion products is used to directly heat the boiling tank. This embodiment, however, provides for less efficient transfer of the heat of combustion to the water and, therefore, is not preferred. Other combustor-evaporator configurations are possible as long as the configuration provides for combusting the feedstock to produce heat and for passing some of the heat of combustion to boil water to produce steam.
The heat of combustion is primarily transferred via the combustion products and boils the water in the tank 20 to produce steam. The resulting steam is provided via a steam outlet port 22 to the subsequent power generation and steam condensation processes shown in FIG. 1. Although not shown, it will be appreciated that there should also be some means to replenish the feedstock 10 and the input water as they are consumed, preferably automatically, but at least manually. Replenishment of either may be on a batch basis, a continuous basis, or some combination thereof. The design of the combustion chamber is not critical but preferably includes a plurality of air inlets (not shown) situated in numerous locations to allow primary, secondary, and below-grate air injections or infiltration to allow for adequate air intake and combustion of the biomass. The combustion chamber is preferably, but not necessarily, insulated and preferably, but not necessarily, includes a grate, mechanical grate, moving grate, or other device (not shown) which promotes the flow of ash into a lower ash collection bin 18 for convenient removal and/or at least so that the ash or other unburned or partially-burned residue does not build up and encumber the combustion process.
Returning to FIG. 1, it can be seen that once the water begins to boil and produce steam then the produced steam is provided via an output port 21 and a steam line 25 to a steam input port 31 of the ORC evaporator/heat exchanger 30. The steam is condensed in the ORC evaporator and the condensate is provided via a condensate output port 32 and routed via a condensed water line 35 to be collected in the potable water storage tank 40 for later consumption or other use. The process of conversion of the input water to steam, and then the resulting condensation, removes and/or kills most pathogens which may be present in the input water. This process also removes many contaminants which may be present in the input water as they are left behind in the tank 20 when the water evaporates. If, however, a contaminant has a boiling point below the boiling point of water then that contaminant may still be present in the condensate and may have to be removed by other means.
The ORC cycle is similar to a steam Rankine cycle, which used in many electrical power generation facilities, except that, in this case, the working fluid has a lower boiling point than water and, preferably, has a much lower boiling point than water. The working fluid should also have acceptable boiling point versus pressure properties; that is, the change from a liquid to a gas should cause a substantial increase in the pressure. In addition, the working fluid is preferably non-corrosive and stable, that is, does not readily decompose under the expected operating conditions. Examples of acceptable working fluids are refrigerants, alphiphatic hydrocarbons such as, but not limited to, heptane and pentane, alcohols, such as but not limited to methanol. Utilizing a working fluid with a low boiling point allows adequate working pressure to be generated using much lower temperature heat and low pressure from the boiling tank than with a conventional steam Rankine cycle. This is advantageous from both mechanical and safety viewpoints. The use of lower temperature heat, such as steam at 212 ° F., is much safer to use and is easier on equipment than, for example, superheated steam. Also, the use of an atmospheric or low pressure in the boiling tank is much safer to use, and is much simpler to construct and maintain, than a high-pressure superheated steam system.
In the preferred embodiment, the temperature and pressure on the ORC high pressure vapor line are 5 to 70 bar and 50 to 150° C., and, more preferably, 5 to 30 bar and 50 to 130° C.
Normally, in a desalinization or water purification process, the energy released during condensation of the steam is either used to aid in the desalinization process, such as by pre-heating the incoming water, or is simply vented to the atmosphere as waste heat. However, in the preferred embodiment, the steam from the desalination process is condensed in the ORC evaporator, and the energy released thereby is used to boil the ORC working fluid and to generate a high pressure. The working fluid vapor is then provided to, via a high pressure vapor line 45, and used to, power a turbine 50 which transforms the pressure into a mechanical rotation. The preferred application of the rotation is to turn a drive shaft 53 to drive a generator 54 to produce electrical power, but the rotation can be used to power any direct drive application, such as, for example, to pump water for irrigation or to replenish the input water and/or cooling water, or to drive another mechanical process, such as a mill.
The working fluid then flows from the turbine 50 via a lower pressure vapor line 55 to a condenser 60 which returns the working fluid back to a liquid state prior to being pumped by a circulation pump 75 back into the ORC evaporator. It will be appreciated that it may be necessary to operate the circulation pump manually or by another power source, such as a battery, until the generator begins producing enough electrical power to operate the circulation pump. A cooling fluid, such as water, is provided via a cooling fluid input conduit or water line 65 to the ORC condenser 60. The warmed cooling fluid is then provided via a cooling fluid output conduit 70 to a discharge location or other process. The cooling fluid may be used to provide local district heating, may be discharged directly into the environment, or may be returned to its source, such as a river. Alternatively, some of the warmed cooling fluid may be used as an input liquid to the evaporator 20. In areas where fire is a hazard, this cooling fluid water may be sprayed into the chimney 27 to quench any sparks and reduce the likelihood of starting a fire. An air cooled condenser may also be used.
Returning to FIGS. 1 and 2, two different configurations of the firebox and boiling tank are shown. In FIG. 1 the combustion products flow from the firebox to and through the heat exchange tubes in the boiling tank, and then from the tubes via a return path (which may be more tubes) to a chimney at the top of the firebox. In FIG. 2 the combustion products flow from the firebox to and through the tubes in the boiling tank and then to a chimney which is not part of the firebox. Thus, in both configurations, the combustion products flow through the heat exchange tubes and thereby heat up the water in the boiling tank so that steam is produced.
The size of the heat exchange tubes is not critical but the tubes should be large enough to allow good heat transfer to the water and to allow the combustion products to flow through the tubes without pressure buildup in the firebox, but should not so large that a significant portion of the energy escapes though the chimney or that condensation of water vapor or other combustion products occurs in the tubes. For example, if the tubes are too short and/or too wide then the energy transfer will be less than desired and the exhaust gases going to the chimney 27 will be hotter than desired. Conversely, if the tubes are too long and/or too narrow then the pressure drop through the tubes will be excessive and the firebox may become hotter than desired or the exhaust gases may be forced out of the fuel and/or air input ports of the firebox. Also, the composition of the heat exchange tubes is not critical, but should be of a material which can withstand the heat of the combustion products and is not degraded, or is only slowly degraded, by the heat, the combustion products, the water being heated, or chemicals or contaminants which may be in the water. For example, in one embodiment, 44 exchange tubes were used, and each exchange tube was made stainless steel 304 tubing, and had a length of about 1.2 meters, an inner diameter of 22 mm, and a wall thickness of 1.7 mm.
Due to the nature of the particular biomass and the input water used, the inner and/or outer surfaces of the tubes 23 in the tank 20 may become coated with soot, scale, etc., and the efficiency of the heat transfer will thereby eventually be reduced or even severely hampered. Therefore, it is preferred that the tank 20 be constructed so that it can be disassembled to expose the tubes 23. The tubes 23 can then be steam-cleaned, brushed and/or scoured, chemically treated, etc., as necessary, to remove the buildup and restore them to good operating condition.
Electrical and/or mechanical power is produced and, simultaneously, water is desalinated/sterilized to produce potable water by combusting a carbon-containing feedstock to produce heat, using some of the heat of combustion to evaporate water to produce steam, using the steam as a heat source in a process, such as an ORC process, which converts low grade thermal energy into mechanical or electrical energy, producing a condensate from the steam, collecting the condensate and providing the condensate as potable water.
Thus, a single combustor/evaporator unit provides steam which is used both to transfer energy to another process, such as an ORC process, and to provide potable water. The heat of combustion is thus serially used twice: (1) to convert water into steam, thereby purifying it, and (2) to boil the ORC working fluid to create pressure to turn the turbine. Thus, potable water and electrical and/or mechanical power are simultaneously produced. In one test embodiment, sufficient steam was available to drive a 10 KW generator and produce 40 gallons/hour of potable water. The size of the system is configured depending upon the resources locally available and the needed results. Thus, a smaller unit would be preferable in a situation where fuel and/or water are locally limited, and a larger unit would be preferable where those resources are more locally available. Further, the size of the units can be made such that they are portable. Thus, in areas where the where electrical power and potable water are scarce or non-existent, either because of natural conditions or because of a natural disaster, electrical power and potable water can be quickly and readily provided by using locally available biomass and water.
The present invention enhances the quality of the environment by reducing the quantity of material going to landfills, reduces green house gas emission by using materials that might otherwise simply be burned, and conserves energy resources by providing useful products and services, such as potable water and mechanical and/or electrical power, from materials that might otherwise be simply burned or tossed into a landfill to dispose of them.
Conditional language, such as, among others, “can”, “could”, “might”, or “may”, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments optionally could include, while some other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language indicates, in general, that those features, elements and/or step are not required for every implementation or embodiment.
The above has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms, structures or embodiments disclosed. Obvious modifications or variations are possible in light of the above teachings. The implementations discussed above illustrate the principles of the invention and its practical application and thereby enable one of ordinary skill in the art to utilize the disclosure in various implementations and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the disclosure as determined by the appended claims when interpreted in accordance with the breadth and equivalents to which they are legally entitled.

Claims

1. A power generation and water purification apparatus, comprising:

a combustion chamber to burn a fuel to provide combustion products, and having a fuel input port to receive said fuel;

a boiling tank having a water input port to receive water and a steam output port to discharge steam;

a plurality of heat exchange tubes, connected in parallel, and functionally connected to said combustion chamber to receive said combustion products, said tubes being at least partially inside said boiling tank and to transfer heat from said combustion products to said water in said boiling tank to produce said steam;

an exhaust conduit, functionally connected to the plurality of heat exchange tubes, to receive and discharge combustion products which have flowed through the plurality of heat exchange tubes;

an evaporator to transfer heat from said steam to an Organic Rankine Cycle (ORC) working fluid to evaporate said ORC working fluid to produce a high pressure ORC vapor and to condense said steam to provide purified water, said evaporator having a steam input port functionally connected to said steam output port of said boiling tank to receive said steam, a condensate port for discharging said purified water, a working fluid input port to receive said working fluid, and a vapor output port for discharging said high pressure ORC vapor;

a turbine to produce mechanical power from said high pressure ORC vapor, said turbine having a high pressure vapor input port functionally connected to said evaporator to receive said high pressure ORC vapor, and a low pressure vapor output port to discharge a low pressure ORC vapor;

a condenser to transfer heat from said low pressure ORC vapor to a cooling fluid to condense said low pressure ORC vapor to produce an ORC working fluid, said condenser having a low pressure vapor input port functionally connected to said low pressure vapor output port of said turbine for receiving said low pressure ORC vapor, an ORC working fluid condensate output port for discharging said ORC working fluid, a cooling fluid input port to receive said cooling fluid, and a cooling fluid output port to discharge said cooling fluid; and

a pump to provide said ORC working fluid to said evaporator, said pump having an ORC working fluid input port functionally connected to said ORC working fluid condensate output port, and an ORC working fluid output port functionally connected to said working fluid input port of said evaporator.

2. The apparatus of claim 1 wherein said ORC working fluid has a boiling point below the boiling point of water.

3. The apparatus of claim 1 wherein said ORC working fluid is either heptane or pentane.

4. The apparatus of claim 1 and further comprising an electrical generator, functionally connected to said turbine, to generate electricity.

5. The apparatus of claim 1 and further comprising a collection tank to collect said purified water.

6. A power generation and water purification apparatus, comprising:

a boiling tank, heated by said combustion products, and having a water input port to receive water and a steam output port to discharge steam;

7. The apparatus of claim 6 wherein said ORC working fluid has a boiling point below the boiling point of water.

8. The apparatus of claim 6 wherein said ORC working fluid is either heptane or pentane.

9. The apparatus of claim 6 and further comprising an electrical generator, functionally connected to said turbine, to generate electricity.

10. The apparatus of claim 6 and further comprising a collection tank to collect said purified water.

11. A method to generate power and purify water, comprising:

(a) burning a fuel to provide a hot gas;

(b) transferring heat from said hot gas to convert water into steam;

(c) transferring heat from said steam to convert an Organic Rankine Cycle (ORC) working fluid into a high pressure ORC vapor and to provide condensate from said steam as purified water;

(d) providing said high pressure ORC vapor to a turbine to generate power and to provide a low pressure ORC vapor;

(e) cooling said low pressure ORC vapor to provide an ORC working fluid condensate; and

(f) pumping said ORC working fluid condensate to be used as said ORC working fluid in (c).

12. The method of claim 11 wherein said ORC working fluid has a boiling point below the boiling point of water.

13. The method of claim 11 wherein said ORC working fluid is either heptane or pentane.

14. The method of claim 11 and further comprising automatically providing said water to be converted into steam.

15. The method of claim 11 wherein a cooling fluid is used to cool said low pressure ORC vapor.

16. The method of claim 11 wherein water is used to cool said low pressure ORC vapor.

17. The method of claim 11 and further comprising collecting said purified water.

18. The method of claim 11 wherein waste biomass is burned as said fuel to provide said hot gas.

19. The method of claim 11 wherein said power is used to generate electricity.