Patent Application
20130318968
1. Field of the Invention
This invention relates generally processes and systems for generating electrical power, and more particularly, a process and system that extracts heat energy from the output gas of a gassifier, provides the extracted heat energy the system for generating electrical power via its associated feedwater system or make up water system, and can be applied any heat transfer process, including simple steam generation.
2. Description of the Related Art
There is significant interest in renewable energy projects. Thermal plasma has consistently distinguished itself as a high efficiency, low emissions gasification process for just about any feedstock, and has been identified as one of the most desirable processes for use in producing energy from renewable fuels.
If an analysis of plasma waste (or other renewable fuels) relative other energy facilities is conducted, it becomes apparent that the lack of existing plasma projects is not exclusively the result of technological problems, but also results from the relatively poor economics associated with this technology. Plasma technology is not inexpensive when compared disposition of waste using landfill, incineration, or conventional gasification.
Many plasma projects fail at the onset, notwithstanding extensive initial marketing efforts, usually as a result of inadequate financing and low or nonexistent profitability. Recently some states have allocated bonuses for development and use of renewable energy, and such efforts have stimulated the use of plasma systems in the production of energy. Unfortunately, it is expected that this modest boon to plasma usage will be short lived, as it represents an artificial market that is a poor model on which build a business. This is particularly problematical when one considers that these facilities are expected produce power cost-effectively for at least fifty years.
Many plasma projects in the past have pinned false hopes on high tipping fees for hazardous waste without fully understanding the complications that are associated with such materials. The handling of these materials is not only complex and expensive, but also potentially dangerous if not properly engineered. The entire process and the facility itself thus become unduly expensive.
Most counties emphatically state that they do not desire that large quantities of hazardous waste be transported through their communities. However, large quantities of such waste must be generated if the facility is achieve profitability. The production and delivery of the hazardous waste have be carefully coordinated since it is dangerous store biological and other hazardous waste feedstock.
Some companies have invested unrealistic hopes in “high value plasma by-products” such as Rockwool. This product has merit, but the production, distribution, and sale of the product are all in their infancy. It is an unfortunate reality that in order that a production facility be economically viable, it must achieve profitability beginning very early in its operation. Energy companies cannot wait several years develop a product and a market.
The process and system of the present invention overcomes the economic hurdles noted above for a plasma system. It is be understood, however, that the invention herein described is not limited the use of a plasma gassifier. In some embodiments of the invention, conventional gassifiers can be employed. The use of a plasma gassifier in the practice of the present invention simply increases overall system effectiveness.
The system of the present invention is simple, flexible, and very energy efficient. In short, it produces a large amount of renewable power from a feedstock such as Municipal Solid Waste (“MSW”), for a very small capital investment. Any feedstock can be used, including, for example, biomass or algae. MSW is but a common example of a renewable feedstock.
It is, therefore, an object of this invention provide a simple and cost-effective renewable energy system.
It is another object of this invention provide a renewable energy system that can consume virtually any feedstock.
It is also an object of this invention provide a simple and cost-effective renewable energy system that can use a conventional gassifier.
It is a further object of this invention provide a simple and cost-effective renewable energy system that can use a plasma gassifier.
It is additionally an object of this invention provide a process and system for enhancing the thermal efficiency of a Rankine or other steam process, or any process that requires heat.
It is yet a further object of this invention provide a process and system for enhancing the thermal efficiency of a power plant.
It is also another object of this invention provide a process and system for extracting heat energy from a renewable energy system that can consume virtually any feedstock and providing the heat energy a Rankine or other steam process, or any process that requires heat.
It is yet an additional object of this invention provide a process and system for extracting heat energy from a plasma gassifier and providing the heat energy to any process that requires heat, including a power plant.
It is yet an additional object of this invention provide a process and system for extracting heat energy from a plasma gassifier and providing the heat energy to any heat transfer process, including simple steam generation.
The foregoing and other objects are achieved by this invention which provides a method of extracting heat energy from a gassifier and delivering the heat energy a power plant. In accordance with a first method aspect of the invention, there are provided the steps of extracting heat energy from a gas product issued by the gassifier, and delivering the extracted heat energy a selectable combination of a feedwater system and a make up water system of a power plant.
In one embodiment of the invention, the gassifier is a plasma gassifier, and is the gas product is syngas. In a further embodiment, prior performing the step of extracting heat energy, there is provided the further step of combusting the syngas in an afterburner.
In some embodiments, there is provided the further step of supplying an air flow the afterburner. The step of supplying the air flow the afterburner is performed in excess of stoichiometric cool the outlet charge of the afterburner. In one embodiment of the invention, the step of supplying air flow the afterburner is performed at a selectable one of an approximately stoichiometric level and a sub-stoichiometric level. In other embodiments, however, the step of supplying air flow the afterburner is performed at a selectable one of an approximately stoichiometric level and a sub-stoichiometric level.
In some embodiments, the step of supplying an air flow the afterburner is performed at a variable flow rate. The flow rate is varied in response an A/F ratio or an afterburner temperature characteristic. In a specific illustrative embodiment of the invention, there is further provided the step of preheating the air flow the afterburner reclaim energy from the system.
In another embodiment, there is provided the step of injecting recirculated exhaust gas (i.e., EGR) into the afterburner. In other embodiments, the step of injecting recirculated exhaust gas into the afterburner is performed at a flow rate that is varied in response an afterburner temperature characteristic. Exhaust Gas Recirculation (EGR) is used cool the charge and thereby reduce the emissions in the afterburner. This aspect of the invention can be combined with any of less than stoichiometric air injection, equal stoichiometric air injection, or greater than stoichiometric air injection.
In an advantageous embodiment of the invention, the gassifier is a plasma gassifier, and there is further provided the step of cooling the plasma torch of the plasma gassifier by using an incoming feedwater and/or make up water from the power plant. One or more of natural gas, syngas, and propane are used in some embodiments of the invention supplement the extracted heat energy. Additionally, a ceramic media filter is used reduce emissions.
In accordance with a further method aspect of the invention, there is provided a method of providing heat energy from a gassifier a power plant. The method includes the steps of:
issuing a gas product from the gassifier;
delivering the gas product a heat exchanger arrangement;
delivering feedwater and/or make up water from the power plant the heat exchanger arrangement;
extracting heat energy from the gas product in the heat exchanger arrangement;
delivering the extracted heat energy the feedwater and/or make up water from the power plant in the heat exchanger arrangement; and
returning the feedwater and/or make up water with the extracted heat energy the power plant.
In one embodiment of this further method aspect of the invention, the gassifier is a plasma gassifier, and the gas product is a syngas product. In a further embodiment, the plasma gassifier is provided with a plasma torch, and there is provided the further step of cooling the plasma torch with the feedwater and/or make up water of the power plant.
In a still further embodiment of the invention, prior performing the step of delivering the gas product the heat exchanger arrangement, there is provided the further step of combusting the syngas in an afterburner.
In other embodiments, there is further provided the step of supplying an air flow the afterburner. In an advantageous embodiment, the step of supplying the air flow the afterburner is performed at a variable flow rate that is responsive to an operating condition of the afterburner.
In other embodiments, recirculated exhaust gas (EGR) is injected into the afterburner. In some embodiments, the step of injecting recirculated exhaust gas (EGR) into the afterburner is performed at a variable flow rate responsive an operating condition of the afterburner.
The extracted heat energy is, in some embodiments, supplemented with a selectable one of liquid or gaseous fuels such as natural gas or propane.
Comprehension of the invention is facilitated by reading the following detailed description, in conjunction with the annexed drawing, in which:
The feed system, which includes shredder 2, compresses the incoming feedstock MSW 1 so as minimize the introduction of air. An in-line, high density flow meter 23 monitors feedstock velocity provide instantaneous feedstock flow rate data. Plasma chamber 6, or other conventional gassifier is, in this specific illustrative embodiment of the invention, advantageously operated in a pyrolysis mode, or in air and/or oxygen combustion boosted modes of operation. Additives such as lime 4 are added, in this embodiment, the gassifier control emissions and improve the quality of an output slag 7.
Methods of chemically boosting heat such as with the use of natural gas at natural gas injection port 3 can be used in the practice of the invention. Additionally, propane injection (not shown), or any other liquid or gaseous fuel and fuel oxidation (not shown) can be used supplement the heat input by plasma torch 5.
In this embodiment of the invention, plasma torch 5 has its cooling water flowing in series with feedwater inlet 10. It is be understood that although this description is directed the use of feedwater from a power plant, such use is merely illustrative, as the invention can be practiced using other sources of water, such as make up water (not shown) from a power plant or other source. The series connection plasma torch 5 and associated components are not shown in the figure. Such routing of the plasma torch cooling water obviates the need for a cooling tower and increases the overall efficiency of the plant.
A syngas product is supplied via a syngas line 21 an unlined or refractory lined afterburner 8 extract the chemical heat from the product gas. In this embodiment of the invention, the afterburner is a conventional thermal oxidizer or a chamber specifically designed combust the syngas. In other embodiments, the afterburner will further function as a cyclone separator. A large flow of preheated air is injected into the afterburner in a quantity that is typically, but not always, greater than stoichiometric. This lowers the outlet charge temperature of the afterburner, a function that in some embodiments is critical due the extremely high working temperatures of the plasma chamber exhaust, which becomes the input the afterburner.
The high air flow that is injected into afterburner 8 lowers its outlet temperature down to where a conventional heat exchanger, which in this embodiment takes the form of a high temperature boiler 9, extracts the heat energy. In the present embodiment, the heat energy is transferred into a feedwater loop 10 coming from a power plant (not shown) and is returned to the plant with additional heat added via feedwater outlet 11. In the practice of the invention, additional loops (not shown) and water outlets (not shown) can in some embodiments be provided for use of make up water.
In this specific illustrative embodiment of the invention, the feedwater from the power plant is received at inlet 10 at a pressure of approximately 280 psi and at a temperature of approximately 120° F. This corresponds to approximately 88 BTU/LB. After being heated in high temperature boiler 9, the thermally enhanced feedwater that is delivered to the power plant via feedwater outlet 11 has a pressure that remains at approximately 280 psi, but at a temperature of approximately 400° F. The thermally enhanced feedwater therefore has an energy characteristic corresponding to approximately 376 BTU/LB. The heat energy extracted from the MSW that is delivered to the feedwater is used in place of fossil fuel heat energy in the power plant, thereby increasing the thermal efficiency of the power plant and reducing its fossil fuel consumption. Any form of heat transfer, such as from make up water, heating, or steam generation in heat exchanger number 9, would qualify for generation of renewable energy.
The spent syngas continues through a bag house 12 to remove particulates. However, in some embodiments of the invention, other arrangements, such as precipitating filters can be used. A low temperature heat recovery system 14 is used to preheat the afterburner combustion air, which increases efficiency.
A sulfur removal system 15 and a mercury removal system 16 are conventional emission control devices. A blower 17 provides pressure for the afterburner combustion air system. Blower 17 can be variable speed or valved (not shown) to improve performance, and is controlled by a feedback signal (not shown) responsive to the afterburner air/fuel ratio, the afterburner outlet temperature, or other combustion related parameters.
An induction fan 18 pulls a slight vacuum on the complete system, and in some embodiments of the invention, is designed to utilize a variable speed driver (not shown) to improve system efficiency. A stack 19 is optionally employed in this embodiment as an emergency oxidizer or a simple exhaust stack depending on the redundancy desired in the system design.
It should be noted that no simple steam cycle generator or Rankine cycle components are required to be used in this feedwater or make up water system. This significantly reduces the capital investment needed for the facility.
In this specific illustrative embodiment of the invention, the filtered gas is conducted to high temperature boiler 9, where the heat energy is extracted and transferred to feedwater or make up water loop 10 coming from a power plant (not shown), and is returned to the plant with additional heat added via feedwater outlet 11, as described above in relation to
Referring once again to
It is to be understood that the invention is not limited in its application to enhancing feedwater and/or make up water for use in a power plant, as any Rankine or other steam process, or any process that requires heat can benefit from the energy transfer system of the present invention
Although the invention has been described in terms of specific embodiments and applications, persons skilled in the art can, in light of this teaching, generate additional embodiments without exceeding the scope or departing from the spirit of the invention described herein. Accordingly, it is to be understood that the drawing and description in this disclosure are proffered to facilitate comprehension of the invention, and should not be construed to limit the scope thereof.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/399,294 filed Jul. 8, 2010; and of U.S. Provisional Patent Application Ser. No. 61/403,929, filed Sep. 23, 2010. The disclosures of those provisional patent applications are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US11/01197 | 7/8/2011 | WO | 00 | 7/29/2013 |
| Number | Date | Country | |
|---|---|---|---|
| 61399294 | Jul 2010 | US | |
| 61403929 | Sep 2010 | US |
