The present invention relates to a process to produce both potable water and electrical power.
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.
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.
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
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.
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
Returning to
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
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.
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”.
Number | Date | Country | |
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61296142 | Jan 2010 | US |