WO2012005768A1

WO2012005768A1 - Plasma feedwater and/or make up water energy transfer system

Info

Publication number: WO2012005768A1
Application number: PCT/US2011/001197
Authority: WO
Inventors: James Charles Juranitch; Alan C. Reynolds
Original assignee: James Charles Juranitch; Reynolds Alan C
Priority date: 2010-07-08
Filing date: 2011-07-08
Publication date: 2012-01-12
Also published as: CA2804605A1; US20130318968A1; EP2591286A1

Abstract

A method and system for converting a feedstock using thermal plasma or other gassifier, into a feedwater or make up water energy transfer system. Feedstock is any organic material or fossil fuel. The energy transferred in the feedwater or make up water is used in any Rankine or other steam process, or any process that requires heat. Heat is extracted from a gas product issued by a gassifier and is delivered to a power plant via its feedwater system or make up water system. Preferably, the gassifier is a plasma gassifier and the gas product is syngas that is combusted in an afterburner. A heated air flow and/or EGR flow is provided to the afterburner at a variable flow rate that is responsive to an operating characteristic of the afterburner.

Description

Plasma Feedwater and/or Make Up Water

Energy Transfer System

Relationship to Other Applications

This application claims the benefit of United States Provisional Patent Application Serial Number 61/399,294 filed July 8, 2010; and of United States Provisional Patent Application Serial Number 61/403,929, filed September 23, 2010. The disclosures of those provisional patent applications are incorporated herein by reference.

Background of the Invention

FIELD OF THE INVENTION

This invention relates generally to processes and systems for generating electrical power, and more particularly, to a process and system that extracts heat energy from the output gas of a gassifier, provides the extracted heat energy to the system for generating electrical power via its associated feedwater system or make up water system, and can be applied to any heat transfer process, including simple steam generation.

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 to 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 to 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 to build a business. This is particularly problematical when one considers that these facilities are expected to 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 to achieve profitability. The production and delivery of the hazardous waste have to be carefully coordinated since it is dangerous to store biological and other hazardous waste feedstock.

Some companies have invested unrealistic hopes in "high value plasma byproducts" 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 to be economically viable, it must achieve profitability beginning very early in its operation. Energy companies cannot wait several years to 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 to be understood, however, that the invention herein described is not limited to 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 to provide a simple and cost- effective renewable energy system.

It is another object of this invention to provide a renewable energy system that can consume virtually any feedstock.

It is also an object of this invention to provide a simple and cost-effective renewable energy system that can use a conventional gassifier.

It is a further object of this invention to provide a simple and cost-effective renewable energy system that can use a plasma gassifier.

It is additionally an object of this invention to 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 to provide a process and system for enhancing the thermal efficiency of a power plant.

It is also another object of this invention to 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 to a Rankine or other steam process, or any process that requires heat. It is yet an additional object of this invention to 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 to 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.

Summary of the Invention

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 to 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 to 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 the gas product is syngas. In a further embodiment, prior to 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 to the afterburner. The step of supplying the air flow to the afterburner is performed in excess of stoichiometric to cool the outlet charge of the afterburner. In one embodiment of the invention, the step of supplying air flow to 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 to 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 to the afterburner is performed at a variable flow rate. The flow rate is varied in response to 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 to the afterburner to 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 to an afterburner temperature characteristic. Exhaust Gas Recirculation (EGR) is used to 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 to 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 to supplement the extracted heat energy. Additionally, a ceramic media filter is used to reduce emissions.

In accordance with a further method aspect of the invention, there is provided a method of providing heat energy from a gassifier to a power plant. The method includes the steps of:

issuing a gas product from the gassifier;

delivering the gas product to a heat exchanger arrangement;

delivering feedwater and/or make up water from the power plant to the heat exchanger arrangement;

extracting heat energy from the gas product in the heat exchanger arrangement; delivering the extracted heat energy to 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 to 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 to performing the step of delivering the gas product to 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 to the afterburner. In an advantageous embodiment, the step of supplying the air flow to 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 (EG ) 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 to 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.

Brief Description of the Drawing

Comprehension of the invention is facilitated by reading the following detailed description, in conjunction with the annexed drawing, in which : Fig. 1 is a simplified schematic representation of a process and system for generating energy from a renewable energy source constructed in accordance with the principles of the invention;

Fig. 2 is a simplified schematic representation of a further embodiment of the invention; and

Fig. 3 is a simplified schematic representation of a further embodiment of the invention that includes injection of recirculated exhaust gas (EGR) used for any heat reclamation process such as steam or feedwater or make up water when combined with a gassifier and more specifically a plasma gassifier and afterburner system. Detailed Description

Fig. 1 is a simplified schematic representation of a process and system for generating energy from a renewable energy source constructed in accordance with the principles of the invention. As shown in this figure, municipal solid waste, designated as MSW 1, or other feedstock, is delivered, in this specific illustrative embodiment of the invention, to the system by a crane 20, which unloads same from a truck (not specifically designated). The feedstock can be any organic material, or fossil fuel. Crane 20 transfers MSW 1 to a shredder 2. The shredded feedstock (not shown) is then delivered to a plasma chamber 6. It is to be understood that any other form of gassifier can be employed in the practice of the invention.

The feed system, which includes shredder 2, compresses the incoming feedstock MSW 1 so as to minimize the introduction of air. An in-line, high density flow meter 23 monitors feedstock velocity to 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, to the gassifier to 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 to 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 to be understood that although this description is directed to 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 to 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 to an unlined or refractory lined afterburner 8 to 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 to 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 to the extremely high working temperatures of the plasma chamber exhaust, which becomes the input to 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.

Fig. 2 is a simplified schematic representation of a further embodiment of the invention. Elements of structure that have previously been discussed are similarly designated. As shown in this figure, a ceramic media filter 24 is used in place of bag house 12 (in Fig. 1). The use of this ceramic media filter reduces fouling in high temperature boiler 9, and achieves superior reduction in emissions of particulates.

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 Fig. 1.

Referring once again to Fig. 2, the heat-reduced syngas product is conducted to combustion air heat recovery system 14 where the recovered heat is provided as preheat to gas afterburner 8. The further heat-reduced syngas product then is conducted to an exhaust gas conditioning system 25, and then to a final particulate filter 26. The filtered particulate matter is then delivered to output slag 7, where it is removed, illustratively by a truck (not specifically designated). The vitrification of particulate matter renders the material essentially inert.

Fig. 3 is a simplified schematic representation of another embodiment of this invention. Elements of structure that have previously been discussed are similarly designated. As shown in this figure, exhaust gas is recirculated as EGR 27 and/or EGR 28 and is used with or without excess oxidation 22 in afterburner 8 to cool the charge (not specifically designated) and reduce harmful emissions. Commercially available sorbents are injected into respective ones of ports 29 and 30 to reduce emissions of S0₂, HCI, Hg, NO_x, etc. and are removed by final particulate filter 26.

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.

Claims

What is claimed is:

1. A method of extracting heat energy from a gassifier and delivering the heat energy to a power plant, the method comprising the steps of:

extracting heat energy from a gas product issued by the gassifier; and delivering the extracted heat energy to a selectable combination of a feedwater system and a make up water system of a power plant.

2. The method of claim 1, wherein the gassifier is a plasma gassifier.

3. The method of claim 1, wherein the gas product is syngas.

4. The method of claim 3, wherein prior to performing said step of extracting heat energy there is provided the further step of combusting the syngas in an afterburner.

5. The method of claim 4, wherein there is further provided the step of supplying an air flow to the afterburner.

6. The method of claim 5, wherein said step of supplying an air flow to the afterburner is performed in excess of stoichiometric to cool the outlet charge of the afterburner.

7. The method of claim 5, wherein said step of supplying air flow to the afterburner is performed at a selectable one of an approximately stoichiometric level and a sub-stoichiometric level .

8. The method of claim 4, wherein there is further provided the step of injecting recirculated exhaust gas into the afterburner.

9. The method of claim 8, wherein said step of injecting recirculated exhaust gas into the afterburner is performed at a flow rate that is varied in response to an afterburner temperature characteristic.

10. The method of claim 5, wherein said step of supplying an air flow to the afterburner is performed at a variable flow rate.

11. The method of claim 10, wherein the flow rate is varied in response to an A/F ratio.

12. The method of claim 10, wherein the flow rate is varied in response to an afterburner temperature characteristic.

13. The method of claim 5, wherein there is further provided the step of preheating the air flow to the afterburner to reclaim energy from the system.

14. The method of claim 1, wherein the gassifier is a plasma gassifier, and there is further provided the step of cooling a plasma torch by using a selectable combination of an incoming feedwater and a make up water from the power plant.

15. The method of claim 1, wherein there is provided the further step of supplementing the extracted heat energy with a selectable one of natural gas and propane.

16. The method of claim 1, wherein there is provided the further step of reducing emissions by subjecting the gas product to a ceramic media filter.

17. A method of providing heat energy from a gassifier to a power plant, the method comprising the steps of:

issuing a gas product from the gassifier;

delivering the gas product to a heat exchanger arrangement;

delivering a selectable combination of feedwater and make up water from the power plant to the heat exchanger arrangement;

extracting heat energy from the gas product in the heat exchanger arrangement;

delivering the extracted heat energy to the selectable combination of feedwater and make up water from the power plant in the heat exchanger arrangement; and

returning the selectable combination of feedwater and make up water with the extracted heat energy to the power plant.

18. The method of claim 17, wherein the gassifier is a plasma gassifier, and the gas product is a syngas product.

19. The method of claim 18, wherein the plasma gassifier is provided with a plasma torch, and there is provided the further step of cooling the plasma torch with the selectable combination of feedwater and make up water of the power plant.

20. The method of claim 18, wherein prior to performing said step of delivering the gas product to the heat exchanger arrangement, there is provided the further step of combusting the syngas in an afterburner.

21. The method of claim 20, wherein there is further provided the step of supplying an air flow to the afterburner.

22. The method of claim 21, wherein said step of supplying an air flow to the afterburner is performed at a variable flow rate responsive to an operating condition of the afterburner.

23. The method of claim 17, wherein there is provided the further step of supplementing the extracted heat energy with a selectable one of natural gas and propane.

24. The method of claim 17, wherein there is provided the further step of injecting recirculated exhaust gas (EGR) into the afterburner.

25. The method of claim 24, wherein said step of injecting recirculated exhaust gas (EGR) into the afterburner is performed at a variable flow rate responsive to an operating condition of the afterburner.