Patent Application
20080223315
The present invention relates generally to generation of steam. More particularly, the present invention relates to a system and method of generating steam using hydrogen as the fuel source. The present invention generates no air emissions in most cases, and no carbon pollution in all cases.
The use of a boiler to generate steam dates back centuries. In the 1st century A.D., Hero of Alexandria used a combination of a steam engine and boiler to turn boiling water into mechanical energy. His invention, called an aeolipile, used a kettle connected via tubes to a round copper sphere. The kettle or boiler was filled with water and as it was heated it vented steam through the copper tubes then out small tubes around the radius of the sphere to created jets to propel his engine.
Early steam generators used wood or lamp oil as a fuel. Later, natural gas and coal were introduced as fuels. The use of coal, natural gas and oil have been around for hundreds of years, and are the predominate fuels used in boilers today. All of these fuels contain carbon, and produce the undesirable green house gas called carbon dioxide when they are burned. Most recently, nuclear energy has been used to generate steam for steam turbine generators.
A steam boiler in its basic form resembles a kettle of water boiling on the stove. Early steam ships and locomotives placed the fire in the middle of the water. The boiler consisted of an inner tube open at one end and an outer tube sealed at both ends. The area between the inner and outer tubes was filled with water which boiled when heated. A fire tender would add fresh wood or coal to the fire as it burned down. Much of the heat was lost out the steam ship's or locomotive's stacks. Most people will remember seeing pictures with smoke pouring out the stack of a train or steam ship. This smoke was predominately wasted heat and practically unburned fuel. Early steam ships and locomotives were prone to disastrous explosions due to poor pressure controls.
Boiler efficiencies have improved over the recent years. Modern boilers use more precise controls which reduce the smoke produced out the stacks and improve efficiencies. Modern stationary boilers put the steam in high pressure tubes outside the fire which increases the boiler pressure rating and reduces the chance of explosions. They also place economizing heat exchangers on the smoke stacks which, reduces the heat lost out the stack. They also use motor driven fans to force air into the firebox to promote more complete combustion.
Even though the smoke stacks no longer produce smoke, they still pour out air pollution. The burning of carbon based fuels produces carbon monoxide and carbon dioxide. The hotter flames which result in better combustion also produce oxides of nitrogen. New low NOx burners which reduce the flame temperature have been able to reduce nitrogen pollution, but have not eliminated it.
There are two basic types of package boilers or steam generators. The first is the fire tube boiler. The fire tube boiler is used in the traditional steam locomotive and steam ships referenced earlier. The fire tender or engineer would place wood or coal into the firebox where it burned. The hot gases would flow through tubes and then out the stack. Water would be located in a chamber outside the tubes and would boil into steam. In the alternate water tube case, water would be in the tubes and would flow up from the mud drum on the bottom then up through the tubes and out the steam drum on top. The fire and combustion is be placed in the middle of the bundle of tubes, and is located above the mud drum and below the steam drum.
An objective of this invention is the generation of steam without generating air pollution. In the prior art, carbon based fuels are combusted in air and the resulting heat is used to generate steam. Hydrogen fuel contains no carbon atoms. Therefore, it cannot create carbon monoxide or carbon dioxide like previous fuels such as natural gas, methane (from Biomass and other sources), coal and coal based syngas, oil, wood, petroleum products and byproducts, cellulose based fuels and cellulose byproducts, slag, etc. Burning of these carbon based fuels is the number one method of generating steam. The second and third most popular methods are electric heating and nuclear reactors. This invention introduces a new, novel method of generating steam without generating pollution.
The invention presented here takes advantage of several features of the hydrogen oxidation reaction. First, this reaction is one of the most energetic binary reactions of two basic elements. It produces tremendous energy yet it takes very little to get the reaction started and it occurs spontaneously at relatively low temperatures. In the presence of a catalyst, such as platinum, spontaneous oxidation will occur at an even lower temperature. Therefore, in one embodiment of this invention, a catalyst is used to lower the combustion temperature to the point where very little nitrous oxide is created, even when air is used to provide the oxygen. Unlike complex hydrocarbon oxidation reactions, the hydrogen-oxygen reaction easily goes to completion, so the hydrogen fuel is efficiently converted to heat which is used to boil the water. The result of the combustion reaction is essentially water, with virtually no nitrogen compounds, and absolutely no carbon compounds. The resulting exhaust can be condensed to recover the water which enables the process to use the high heating value (HHV) for the hydrogen fuel.
In another embodiment of the invention, the hydrogen-oxygen reaction occurs without a catalyst in a pure hydrogen/oxygen environment. It is easy to see that these two processes can be combined to result in other embodiments of the invention. However, in the pure oxygen environment, only water can be produced as a result of the reaction. Therefore, it produces no nitrogen or carbon pollution. In this process, the water is condensed and fed back into an outside process where the hydrogen and oxygen were originally split. This produces a closed loop system where water is the working fluid. The heat from the reaction is used to boil water to create steam. The resulting steam can be used just as any other steam boiler system. In most boiler systems, the steam is condensed back into condensate which is usually returned to the system. In this embodiment, energy is provided to the system by splitting water into hydrogen and oxygen. The energy is stored in the gasses until it is needed. Then the hydrogen and oxygen gasses are combined in the boiler to make steam, which is a very good media for moving heat energy throughout a plant or facility.
In yet another embodiment of this invention, water is injected with the hydrogen and oxygen. The result is lowering the temperature of the reaction chamber. This reduces the stresses on the mechanical components, and lengthens the life of the steam generator. The steam generated in the reaction chamber by the vaporizing of the injected water is recovered to maintain the overall efficiency of the generator.
In yet another embodiment of this invention, the tubes are coated with material to reduce the effects on them when operated in an environment of hydrogen, oxygen, high temperature and water vapor. Coatings like titanium dioxide form a barrier which prevents hydrogen atoms from migrating through a metal surface and resulting in hydrogen embrittlement. Similarly, chromium surface coatings have been used as a barrier for water and steam related erosion. Also, ceramic and carbon coatings have been used as barriers against the effects of very high temperatures.
In yet another embodiment of this invention, the process uses closed loop systems and condensate recovery to limit water consumption. This embodiment not only conserves the valuable water resources, but it also conserves energy by recovering the heat contained in water vapors. This embodiment also saves on water treatment chemicals as the closed loops with pure deionized water will require little or no treatment. The reaction chamber system in this embodiment consists of the chamber to which a multiplicity of tubes is connected at one end. At the other end of the tubes is connected a condenser. In operation, the hydrogen and oxygen are started to react in the chamber. As the gasses react and travel down the tubes, they transfer the heat outside the tubes and the gasses are cooled. At the same time, as the gasses travel down the tubes, the reacting gasses are forming water vapor (the result of hydrogen and oxygen reacting). By the specification of this invention, the tubes are designed sufficiently long for all of the gasses to be converted to water, and most of the heat generated to be transferred out through the side of the tubes. The remaining heat is removed by the condenser leaving liquid water. Any water that was added in with the fuel would also be condensed. The liquid water can then be split back into hydrogen and oxygen by some other process such as electrolysis. This would complete the cycle for the reaction loop.
In the steam loop, liquid water would be fed under pressure into the steam side of the tubes. Heat from the reaction process is transferred through the walls of the tubes to heat the water. Steam is generated and rises to the top, where it leaves the steam generator. The steam is used by another process and the heat energy is removed. When sufficient energy is removed, the steam condenses back into liquid water. For example, the steam from the steam generator could be used to power a simple cycle, condensing steam turbine generator (STG). In this case, the steam would power the turbine, and as it moves through the turbine the pressure and temperature would decrease. At the discharge of the turbine, a condenser would create a partial vacuum as it takes the last bit of heat out of the steam and condenses it back to liquid water. This liquid water would then be send back to the feed water pumps to complete the cycle.
In this embodiment, the two closed loops can operate at the same, or at different pressures. For example, again using the STG scenario, the steam loop would operate at super critical conditions to supply the STG, while the reaction loop would operate at a much lower pressure in the range of 100 to 200 PSI. Water condensed in the reaction could be used as feed water for the steam loop, provided a high pressure pump was employed to inject the water into the boiler tubes.
In yet another embodiment of this invention, a closed loop steam loop would be used with an open loop reaction system. This arrangement is similar to most package boilers produced today. Whether it is a fire tube or a water tube boiler, the reaction side is open with the flue gas venting to the atmosphere and the steam loop is a closed loop with condensate returned to the system elsewhere in the process. The difference between the prior art and this invention is the hydrogen fuel, the resulting lack of air pollution, and the addressing of the extremely harsh environment resulting from the fuel/oxidizer combination.
This difference is the result of many subtle, but important differences from modern steam boilers. Even at normal hydrocarbon boiler conditions and combustion temperatures, hydrogen embrittlement is a significant problem resulting in boiler tube failures. The boiler of this invention uses a hydrogen rich atmosphere at elevated temperature, compounding the problem. An oxygen rich atmosphere has a similar problem, but a different failure mode. A high temperature oxygen rich atmosphere results in oxidation or burning of the boiler metal much like an oxy-acetylene torch. Still another problem addressed is the fact that high temperatures alone present a problem. This problem is similar to the tube failures which result from a lack of sufficient water in a boiler super heater. On top of all of these, the presence of vaporizing water is very erosive to the components. This invention addresses each of these problems.
The drawings depict various arrangements of the invention, not to limit, but rather to illustrate some of the possible arrangements which include:
In operation, water 10 enters the shell through the nozzle at the bottom of the shell. The controller maintains a fixed water level within the shell 20. Hydrogen 12 and oxygen 13 enter through conduits penetrating the left head 24. The hydrogen 12 and oxygen 13 react together in the reaction chamber 16. As these reaction gasses 14 combine together they move down the path shown by the arrows. The heat generated by the reaction, passes through the tube walls causing the water 10 to boil and generate steam. The steam 11 which is lighter than the water 10 rises to the top of the steam chamber 17 and exits out the nozzle at the top of the shell.
As the hydrogen 12 and oxygen 13 react in the reaction chamber 16, they form water vapor. The zig-zag path through the tubes 23 is sufficiently long enough for all of the hydrogen 12 and oxygen 13 to fully react. The resulting water vapor continues down the zig-zag path cooling while it transfers the generated heat through the boiler tubes 23. The cooler water vapor exits the steam generator through the upper nozzle in the right hand head 25. The exhaust vapor 15 does not contain any contain any carbon or nitrogen compounds.
In
The steam generator operates within a shell 20, with one head 24 fixed on the left end and the other head 25 fixed on the right end. Likewise, the superheater 32 has heads 34 fixed to each end. The heads 24, 25 and 34 are shown separated from the shells 20 and 32 for illustration purposes so the path of the gasses and the divider plate within the heads can be more clearly understood. In operation, the heads are affixed to the shell. The boiler tubes 23 are fixed at each end to the tube sheets 22. In a similar manner, the tubes of the superheater are fixed to tube sheets at either end.
In the embodiment of
The hot reaction gasses leaving the left hand superheater head 34 enter the top nozzle on the left hand head 24 of the steam generator. The hot gasses 14 are now below 1000 deg. F. and all of the hydrogen and oxygen have combined to form water. The hot gasses continue to loose their heat through the sides of the tubes heating the water in the steam side of the tubes while the water begins to condense on the reaction side of the tubes. The exact pressure, temperature and quality of the steam are dependent on the operating conditions and the application the steam generators is being used in. The reaction vapors make one final turn at head 25, then the cooled vapors 35 exit out of the steam generator head 24. The final bit of heat is removed in condenser 36 turning the vapors back to hot liquid water, which goes into tank 37.
Refer to
