Power plants – Motive fluid energized by externally applied heat – Having condition responsive control
Reexamination Certificate
1998-12-21
2001-09-11
Nguyen, Hoang (Department: 3747)
Power plants
Motive fluid energized by externally applied heat
Having condition responsive control
C060S659000, C060S670000
Reexamination Certificate
active
06286316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to vapor recovery apparatus and, in particular, to using recovered vapor for power generation.
2. Description of Related Art
Since the passage of the Clean Air Act, the Congress of the United States has required all persons or organizations handling hydrocarbons or chemicals whose vapors may pollute the air to install means to recover and prevent the contamination of the air by such vapors. Such contaminants can include vapors of gasoline, methylene chloride and other organic compounds.
Such vapors are generated and displaced into the atmosphere when all types of tanks are filled with liquid hydrocarbons or liquid chemicals. Such tanks may be large storage tanks, railroad car tanks, truck tanks, underground storage tanks for gasoline stations and fuel tanks on trucks, buses and automobiles. When these various types of tanks are filled with liquid hydrocarbons or liquid chemicals, vapors escape into the atmosphere and, as is well known, such vapors become a source of smog, which under certain ambient conditions produce dangerous fog conditions and so pollute the atmosphere that they produce dangerous environmental health hazards for human beings.
Known vapor recovery systems have used closed refrigeration cycles to cool a medium that is then used to condense vapors. Condensate can be drained to a decanter to separate heavy and light constituents, such as gasoline and water. The condensing coils for such units are periodically warmed or defrosted to prevent a build up of ice and frost that may block the passage of vapors through the condensing unit. See for example, U.S. Pat. Nos. 4,027,495; 4,068,710; 4,077,789; and 5,291,738.
Such recovery units are typically designed to handle the peak flow of vapors that may be experienced during a course of a work day. To accommodate the peak load, the recovery units are engineered with a relatively high capacity, which still may not be sufficient condense highly volatile vapors.
A disadvantage with vapor recovery systems is the energy required to run these recovery systems. Moreover, certain highly volatile vapors can only be condensed after a high expenditure of energy. Accordingly, the environmental benefits of performing vapor recovery is partially offset by the additional energy consumed to run the recovery systems.
Many industries are economically dependent on inexpensive and abundant electrical power. Many utilities will charge a rate that depends upon the peak usage or the time when the peak usage occurs. For this reason, some industries have invested in cogeneration, wherein a modest private plant for generating electricity will supplement the power from a utility to reduce the peak demand and thereby reduce the rate charged for power. Depending upon the size of the plant, some cogeneration systems can actually return power to the utility lines to earn a credit.
While in principal, a cogeneration plant can be powered by the uncondensed vapor from a vapor recovery unit, the supply of vapor tends to be sporadic and will lack a constancy that will allow cogeneration to occur in a practical way.
Such a cogeneration system may employ a generator driven by an engine that is designed to be powered by a fossil fuel. When the engine is an internal combustion engine, regulating the air/fuel ratio can be difficult when the fuel source is the uncondensed vapor from a vapor recovery unit. The uncondensed vapor can include a variety of vapors whose constituent components cannot be known in advance. Therefore, regulating the speed and power of the engine can be difficult, when the nature of the fuel, and the fuel to air ratio may vary significantly.
Furthermore, one cannot be certain in advance that the combination of a vapor recovery unit and cogeneration system will succeed in providing a net environmental benefit. In particular, the engine exhaust may introduce significant pollutants that should not be exhausted to the atmosphere.
Accordingly, there is a need to recover vapors using a combination of effective techniques such as condensing vapors, as well as using those vapors that were not condensed, in a power generation system.
SUMMARY OF THE INVENTION
In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a system for recovering and utilizing vapor from a source of vapor. The system has a vapor holder for storing a quantity of vapor from the source of vapor. Also included is a condensing means coupled to the vapor holder for receiving and condensing at least partially, vapor from the vapor holder. The system also has an engine, and a generator driven by the engine for generating electrical power. The engine has an engine intake coupled to the condensing means and an exhaust outlet. This engine is powered at least partially, by output from the condensing means.
In accordance with another aspect of the invention, a system for recovering and utilizing vapor from a source of vapor includes a condensing means for receiving and condensing at least partially, vapor from the source of vapor. Also included is an engine having an engine intake coupled to the condensing means, as well as a generator driven by the engine for generating electrical power. The engine is powered at least partially, by output from the condensing means. The system also has a fuel adjustment means and a fuel sensor means. The fuel adjustment means has a control input and is coupled between the engine and the condensing means for adjusting fuel concentration into the engine intake in response to a signal on the control input. The fuel sensor means is coupled to the engine intake (a) for sensing concentration of at least some constituents of vapor at the engine intake, and (b) for applying a signal to the control input of the fuel adjustment means corresponding thereto.
In accordance with still another aspect of the invention, a system for recovering and utilizing vapor from a source of vapor, has a condensing means for receiving and condensing at least partially, vapor from the source of vapor. Also included is an engine coupled to the condensing means and having an exhaust outlet for conducting exhaust from the engine. The engine is powered at least partially by output from the condensing means and drives a generator for generating electrical power. The system also includes an exhaust sensor means coupled to the exhaust outlet for providing an exhaust signal signifying concentration of at least some constituents of the exhaust at the exhaust outlet.
By employing systems of the foregoing type, vapor can be effectively recovered and utilized. In a preferred embodiment, vapor can be stored in a vapor holder, which is a vessel fitted with a flexible membrane or bag that can accommodate the varying volume of vapor to be stored. Consequently, the vapor can then be delivered at a relatively constant rate. Preferably, any engine driven by the vapor can be started or stopped should the supply in the vapor holder become relatively high or low.
In any event, the vapor can be preferably passed through a pre-cooler and a finishing condenser, both containing coils that conduct a refrigerant. Vapors condensed in these two units can be delivered to a decanter that can separate water from other more volatile liquids.
Vapors that were not condensed either because of their high volatility or because of an inadequate capacity to condense, may in the preferred embodiment, be re-heated and passed through a flame arrester to an electrical power generation system. These incoming vapors can be blended with air by means of a preferred modulating valve that is controlled by a fuel sensor, to establish a proper air/fuel ratio. The preferred fuel sensor employs an infrared detector tuned to sense concentration of a particular hydrocarbon, such as butane. The engine can drive a preferred induction generator to return power to utility lines.
Preferably, the engine exhaust can be sampled, cooled by a radiator, and delivered to a continuous emissions
Harlan Gerald R.
Ponzo Joseph C.
Waldrop Richard
Edwards Engineering Corp.
Nguyen Hoang
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