Co-Fired Syngas System

Abstract

A method of generating a blended syngas as a primary product from renewable feedstock, fossil fuels, or hazardous waste with the use of a gassifier arrangement. The generated syngas is blended with natural gas to form a blended fuel product that is delivered to a manufacturing facility or a natural gas power plant.

Description

RELATIONSHIP TO OTHER APPLICATIONS

This application is a continuation-in-part of International Application Number PCT/US2011/001611, filed internationally on 19 Sep. 2011 and published under the PCT as WO 2012/039749 A1 on 29 Mar. 2012, which claims priority to U.S. Provisional Patent Application Ser. No. 61/403,973, filed 19 Sep. 2010. Also, this application is a continuation-in-part of International Application Number PCT/US2011/001614, filed internationally on 19 Sep. 2011 and published under the PCT as WO 2012/039752 A2 on 29 Mar. 2012, which claims priority to U.S. Provisional Patent Application Ser. No. 61/403,991, filed 24 Sep. 2010. The disclosures in these patent applications are incorporated herein by reference to the fullest extent permitted by law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to systems for generating a blended fuel, and more particularly, to an inductive and plasma based system with a pregassifier that generates a blended fuel to be co-fired in a natural gas application. A preferred application is a combined cycle natural gas power plant.

2. Description of the Related Art

Syngas systems in general and more particularly high temperature syngas generating systems such as plasma based systems have been in existence for decades. They have not had significant commercial success due to many reasons. Some of the problems are evident from the following art references.

In US Patent Application US 2007/0012231 by Smith, et al. there is disclosed a plasma based syngas generating system that burns syngas in an afterburner or steam generator and then adds thermal energy into a boiler system for a coal power plant. The Smith, et al. reference describes some of the economic difficulties that plague plasma based systems and manner by which the system therein described proposes to overcome those problems. The Smith, et al. reference is focused only on coal plants and the burning of syngas in an afterburner or boiler to supplement steam production. All of these conditions limit overall system thermal efficiency. The steam Rankin cycle, although reliable, is well documented for its limited efficiency. Such inefficiency results in poor financial performance relative to the required capital investment, and thereby constitutes a limitation on commercial success.

In the system described in US Patent Application 2009/0133407 by Sawyer, syngas is supplied directly to a simple or combined cycle turbine. In operation, this system performs poorly. Syngas production is sporadic in most gassifiers, including plasma based gassifiers. This known arrangement is further challenged when a renewable non-homogeneous feedstock such as biomass or Municipal Solid Waste (MSW) is used. Such an inconsistent fuel is poorly received when, as specified in that disclosure, “syngas is fed directly to a gas turbine.”

The system disclosed in the Sawyer reference describes the “stabilizing [of] an integrated syngas-fired boiler (24) employing low NOx design syngas burners . . . used to combust the produced syngas. For flame safety concerns up to 10% of total heat input may need to be co-fired as a liquid fuel (oil or bio-diesel) pilot flame.” These liquid fuel pilot flame systems have existed for decades in numerous applications. Overlooking the drawbacks of the above application in using the syngas fuel to operate a boiler hampered by the low efficiency issues of a Rankin cycle the known system also requires the cost and complexity of a dual fuel system, specifically a syngas fuel delivery system and a liquid fuel delivery system.

It is an object of the present invention to improve the efficiency of the gassifier over that of a blended fuel system that employs either a generic gassifier or a simple plasma gassifier.

It is a further object of the present invention to overcome the above-noted inefficiency, complexity, and financial inadequacy of prior art arrangements.

SUMMARY OF THE INVENTION

The foregoing and other objects are achieved by this invention, which provides a method of producing a fuel, the method comprising the steps of:

• • delivering a feedstock to a gassifier to generate a product syngas; and
  • blending the product syngas with natural gas to form a blended syngas fuel.

In one embodiment of the invention, there is provided the further step of delivering the blended syngas fuel to a selectable combination of a manufacturing plant and a natural gas power plant.

In a further embodiment, prior to performing the step of blending there is provided the step of cleaning the product syngas.

In a still further embodiment, prior to performing the step of blending there is provided the step of accumulating the product syngas in a buffer. In this embodiment, the step of accumulating includes the steps of:

• • first compressing the product syngas; and
  • storing the compressed product syngas in the buffer.

In an advantageous embodiment, there are provided the further steps of:

• • releasing the compressed product syngas from the buffer; and
  • boosting the pressure of the compressed product syngas released from the buffer.

The feedstock, in one embodiment, is a selectable combination of an organic compound, a fossil fuel, and a hazardous material.

In accordance with a further method aspect of the invention, there are provided the steps of:

• • operating a pregassifier on a selectable combination of waste heat, syngas, a fossil fuel, and a supplemental fuel;
  • operating a gassifier to generate a product syngas, by delivering a feedstock to the gassifier; and
  • blending the product syngas with natural gas to form a blended syngas fuel.

In one embodiment of this further method aspect, there is provided the step of delivering the blended syngas fuel to a selectable combination of a manufacturing plant and a natural gas power plant.

Prior to performing the step of blending there is provided in some embodiments the step of cleaning the product syngas. In an advantageous embodiment, prior to performing the step of blending there is provided the step of accumulating the product syngas in a buffer. As previously noted, the feedstock is, in some embodiments, a selectable combination of an organic compound, fossil fuel, and a hazardous material.

In accordance with still another method aspect of the invention, there is provided a method of producing a fuel, the method including the steps of:

• • operating a pregassifier on a selectable combination of a waste heat, a syngas, a fossil fuel, and a supplemental fuel;
  • operating a gassifier to generate a product syngas, the gassifier having a metal bath, an inductive heat source, and at least one plasma torch to reflect energy off the metal bath;
  • delivering a feedstock to the gassifier; and
  • blending a product syngas with natural gas to form a blended syngas fuel.

In one embodiment of this further aspect of the invention, there is provided the step of delivering the blended syngas to a selectable combination of a manufacturing plant and a natural gas power plant.

However, in some embodiments, prior to performing the step of blending there is provided the step of cleaning the product syngas.

In yet another embodiment of the invention, prior to performing the step of blending there is provided the step of accumulating the product syngas in a buffer.

The feedstock in an advantageous embodiment is a selectable combination of an organic compound, a fossil fuel, and a hazardous material. Also as previously noted, the syngas in some embodiments is cleaned and buffered and compressed before blending with the natural gas.

In various embodiments, the plasma torch operates in any combination of direct acting, indirect acting, AC driven, and DC driven.

It is appreciated by persons of skill in the art that the invention herein disclosed provides a method of producing a commercially viable blended gaseous syngas fuel that can be utilized in a manufacturing process that burns or oxidizes the resultant blended syngas. Contrary to known arrangements that deliver syngas directly into a turbine, the presently disclosed newly formed blended gaseous fuel results in a reliable energy source that can be employed in simple cycle or combined cycle power plants or other manufacturing processes that require heat.

A preferred syngas generator is a plasma based, or an inductive furnace/plasma based, gassifier system. This style of gassifier with efficiency-improving features such as pregassifiers and high turbulence plasma torch energy systems distributed on a metal pool to reflect energy, cause turbulence, and improve efficiency and financial viability. The syngas buffer compressor of the novel design stabilizes syngas production. The high blend ratio of natural gas or other fossil based gaseous fuels with the product syngas from the gassifier allows low NOx turbine combustors to operate successfully, contrary to the poor and unreliable operation that results from the direct use of pure syngas, or liquid fueled flame pilot systems.

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 specific illustrative embodiment of a blended syngas co-fired system constructed in accordance with the principles of the invention.

DETAILED DESCRIPTION

FIG. 1 is a simplified schematic representation of a blended syngas co-fired arrangement 100 constructed in accordance with the principles of the invention. As shown in this figure, blended syngas co-fired arrangement 100 is provided with a gassifier 101 that has an inlet 113 for introducing a feedstock (not shown). In some embodiments of the invention, the feedstock is a renewable feedstock, such as MSW, a fossil fuel, or a hazardous waste (not shown). Any combination of the three forms of feedstock can be used in the practice of the invention. There is additionally provided an outlet port 102 via which the generated syngas (not shown) is removed. In embodiments in which the gassifier incorporates an inductive heat source, there is not provided an outlet for product as would be the case in a conventional inductive furnace (not shown) that would have a large outlet (not shown) for metal or alloy production. Instead, in the present embodiment of the invention, there is provided a small drain 117 for eliminating inorganic slag.

FIG. 1 further shows gassifier arrangement 101 to have a plasma torch 115. In respective embodiments of the invention, plasma torch 115 can be configured to function directly or indirectly. In other embodiments, plasma torch 115 is in the form of a carbon or graphite rod that transmits AC or DC electrical energy into a metal bath 118. The return path for the electrical energy has been omitted from this figure for sake of clarity.

There is provided in this specific illustrative embodiment of the invention a cathode 120 that is coupled electrically to an inductive element 114. Additionally, inductive element 114 has associated therewith an anode 119.

Air, oxygen-enriched air, or oxygen are injected into gassifier arrangement 101 via an inlet 121 to assist in the generation of heat using chemical energy and steam that is delivered via a further inlet 122. The chemical energy and steam assist in the generation of syngas. The process of the present invention can, in some embodiments, be performed in a pyrolysis, or air starved, mode of operation.

The product syngas in this embodiment is forced to exit from outlet port 102, via which it is delivered to a gas cleaning system 103. Pregassifier 116 is operated in some embodiments with the use of waste heat from the syngas that communicates with gas cleaning system 103 (heat path not shown). In some embodiments, additional heat is generated by the oxidation of a slip stream of syngas (not shown) in the pregassifier, or supplemental heat is obtained from a fossil fuel (not shown) such as natural gas.

The syngas that exits gas cleaning system 103 is delivered to a buffer and compressor 104. Buffer and compressor 104 is shown to have a low pressure compressor 105 that fills an accumulator 106. The low to medium pressure syngas from accumulator then is boosted to a pressure slightly higher than the existing 123 working natural gas pressure by operation of compressor 107. The boosted pressure, however, is lower than the pressure of a natural gas main 124, the pressure of which is reduced by a regulator 125.

Natural gas 109 and high pressure syngas from compressor 107 are then blended in a blending system 108 to produce a blended fuel that is issued at port 123. The blended fuel can be of any ratio of syngas and natural gas that is acceptable to a manufacturing facility 110. In an advantageous embodiment, manufacturing facility 110 is a natural gas power plant having single or multiple gas fired turbines 111 (represented schematically). In some embodiments, the turbines are either simple cycle or combined cycle turbines. Persons of skill in the art will recognize that manufacturing facility 110 is not limited to be a power plant, and can be any facility that requires a constant flow of a gaseous fuel.

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 and claimed 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

1. A method of producing a fuel, the method comprising the steps of:

delivering a feedstock to a gassifier to generate a product syngas; and

blending the product syngas with natural gas to form a blended syngas fuel.

2. The method of claim 1, wherein there is provided the step of delivering the blended syngas fuel to a selectable combination of a manufacturing plant and a natural gas power plant.

3. The method of claim 1, wherein prior to performing said step of blending there is provided the step of cleaning the product syngas.

4. The method of claim 1, wherein prior to performing said step of blending there is provided the step of accumulating the product syngas in a buffer.

5. The method of claim 4, wherein said step of accumulating comprises the steps of:

first compressing the product syngas; and

storing the compressed product syngas in the buffer.

6. The method of claim 5, wherein there are provided the further steps of:

releasing the compressed product syngas from the buffer; and

boosting the pressure of the compressed product syngas released from the buffer.

7. The method of claim 1, wherein the feedstock is a selectable combination of an organic compound, a fossil fuel, and a hazardous material.

8. A method of producing a fuel, the method comprising the steps of:

operating a pregassifier on a selectable combination of waste heat, syngas, a fossil fuel, and a supplemental fuel;

operating a gassifier to generate a product syngas, by delivering a feedstock to the gassifier; and

blending the product syngas with natural gas to form a blended syngas fuel.

9. The method of claim 8, wherein there is provided the step of delivering the blended syngas fuel to a selectable combination of a manufacturing plant and a natural gas power plant.

10. The method of claim 8, wherein prior to performing said step of blending there is provided the step of cleaning the product syngas.

11. The method of claim 8, wherein prior to performing said step of blending there is provided the step of accumulating the product syngas in a buffer.

12. The method of claim 8, wherein the feedstock is a selectable combination of an organic compound, fossil fuel, and a hazardous material.

13. A method of producing a fuel, the method comprising the steps of:

operating a pregassifier on a selectable combination of waste heat, syngas, a fossil fuel, and a supplemental fuel;

operating a gassifier to generate a product syngas, the gassifier having a metal bath, an inductive heat source, and at least one plasma torch to reflect energy off the metal bath;

delivering a feedstock to the gassifier; and

blending a product syngas with natural gas to form a blended syngas fuel.

14. The method of claim 13, wherein there is provided the step of delivering the blended syngas to a selectable combination of a manufacturing plant and a natural gas power plant.

15. The method of claim 13, wherein prior to performing said step of blending there is provided the step of cleaning the product syngas.

16. The method of claim 13, prior to performing said step of blending there is provided the step of accumulating the product syngas in a buffer.

17. The method of claim 13, wherein the feedstock is a selectable combination of an organic compound, a fossil fuel, and a hazardous material.

18. The method of claim 13, where the syngas is cleaned and buffered and compressed before blending with natural gas.

19. The method of claim 13, where the plasma torch operates in any combination of direct acting, indirect acting, AC driven, and DC driven.