US20200224869A1

US20200224869A1 - Rotary Cascading Bed Combustion System

Info

Publication number: US20200224869A1
Application number: US16/745,007
Authority: US
Inventors: Doug King
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-01-16
Filing date: 2020-01-16
Publication date: 2020-07-16

Abstract

A rotary cascading bed combustion system for converting waste product into energy includes a rotary cascading bed combustor boiler including a rotating cylinder surrounding a combustion chamber; the rotating cylinder being structured and disposed for cascading the fuel to facilitate the mixing of air and solids, wherein the rotational speed of the rotating cylinder is selectively varied based on the amount of fuel, airflow and combustion properties; wherein combusting waste is mixed with sorbents and cycled through a plurality of combustion zones to produce controlled heat for generating steam; wherein the steam is routed to a turbine; and wherein if carbon burnout is not complete it will be recycled back into the combustion chamber.

Description

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/793,033, filed on Jan. 16, 2019.

TECHNICAL FIELD

The presently disclosed subject matter relates generally to energy production and more particularly to a rotary cascading bed combustion system for generation of energy from the burning of waste.

BACKGROUND OF THE INVENTION

Conventional solid-fuel incinerators are large scale solid fuel systems using technology originally designed for burning high-density fuels (wood and coal) and have been in operation to burn waste for more than two decades. These mass-burn installations typically use vibratory-bed burners (although some stepped-hearth burners have been used). These systems have two major operational problems: (1) moving mechanical parts in the high-temperature burning zone requires frequent maintenance and (2) the relatively short burn time duration resulting in incomplete burn of materials then requires significant scrubbing and cleaning of the exhaust stream to reduce toxic pollutants. Moreover, the total system is too expensive to deploy and operate except in very large facilities burning in excess of 1,500 tons of fuel per day.
The markets for a rotary cascading bed combustion system are considerable—and stand waiting for realistic, practical, affordable, sustainable and environmentally sound solutions to the myriad of problems in waste management, problem fuels utilization, fossil fuels availability, landfill minimization and economical power requirements facing the world today. There remains a need for an environmentally safe and economically sound solution to problems of:
Waste Utilization: The safe, efficient and economical use of non-recyclable municipal, industrial, commercial and agricultural waste—all continually renewing and sustainable resources—in the generation of low-cost power, both steam and electrical, though geographically dispersed small unit power generation stations:

- Municipal Solid Waste
- Production Wastes & Sludges
- Agricultural Wastes
- Wood Wastes
- Used Tires
- Construction Wastes
- Sewer Sludges
- With the accompanying, and potentially substantial, reduction in landfill requirements.

Available Fuels Utilization: Throughout the world there are tremendous quantities of fuels—such as high sulfur coal, brown coal, lignite, shales, coal fines and other waste coal products—that have high heat values but can create environmental emissions problems when burned. RCBC Systems allow clean combustion of these readily available fuels for low cost generation of power, either using individual fuels or fuel combinations to add heat value to low heat value wastes such as sludges.
Small Unit Power Generation: In both advanced and developing economies, there is need for sustainable small unit power generation, using readily available and low-cost fuels, in local areas where grid access is non-existent or limited or transmission costs are high. Essentially power generation taken nearer to the user.

SUMMARY OF THE INVENTION

In accordance with one form of the present invention there is provided a rotary cascading bed combustion system for converting waste product into energy, the rotary cascading bed combustion system including a rotary cascading bed combustor boiler including a rotating cylinder surrounding a combustion chamber; the rotating cylinder being structured and disposed for cascading the fuel to facilitate the mixing of air and solids, wherein the rotational speed of the rotating cylinder is selectively varied based on the amount of fuel, airflow and combustion properties; wherein combusting waste is mixed with sorbents and cycled through a plurality of combustion zones to produce controlled heat for generating steam; wherein the steam is routed to a turbine; and wherein if carbon burnout is not complete it will be recycled back into the combustion chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of the rotary cascading bed combustor boiler;

FIG. 2 is a schematic of the rotary cascading bed combustion system including the rotary cascading bed combustor boiler;

FIG. 3 is a schematic illustrating the rotary cascading bed combustion system in accordance with one embodiment; and

FIG. 4 is a schematic illustrating the rotary cascading bed combustion system.

Like reference numerals refer to like parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the several views of the drawings, the rotary cascading bed combustion system is described and generally indicated as 10. The system 10 is made up of six distinct table modules.
The rotary cascading bed combustion system 10, in part, combines a unique combination of well-known, simple and time-tested physical principals. The technology was developed to create, within a rotation cylindrical combustion chamber, a system for the clean combustion of diverse fuels and wastes, either individually or in one of several combinations.
In order to achieve optimum conditions for clean and complete combustion, provisions must be made to allow maximum exposure of each particle of fuel to combustion air and fully foster sorbent absorption contact with undesirable gases. The rotary cascading bed combustion system's mechanical fluidization coupled with maximized recycling and milling systems achieves those goals.
Referring to FIGS. 1 and 2, the rotary cascading bed combustor boiler 12 is shown. Waste is fed into the rotary cascading bed combustor boiler 12 where it is mechanically fluidized, milled and mixed with emission controlling sorbents. Combusting waste mixed with sorbents is cycled and recycled through numerous combustion zones producing controlled heat, which generates steam. The steam is routed to turbine or other use.
Fluidization of fuels and sorbents is achieved mechanically. A rotating drum structure moves the in-feed and recycling fuels through a three-dimensional pattern—mixing, lifting, dropping, milling, and recirculating fuel and sorbent materials as they are moved laterally, in both directions, along the length of the fluidization drum while being concurrently combusted.
Fuels are burned in multi-dimensional cascading re-circulating contact with sorbents forming harmless combustion by-products and preventing harmful gaseous emissions. The highly stirred atmosphere provides excellent conditions for both combusting and accompanying reactions to control gaseous emissions. For example, a sorbent, such as limestone, continuously reacts throughout the process with sulfur and HCl to for calcium sulfates and chlorides which then are removed as non-hazardous ash. Sorbent chemical reactions take place at combustion temperatures low enough to greatly retard the formation of oxides of nitrogen. Unique internal and external fuels recycling systems foster high sorbent contact with combustion gases and extend fuel dwell times assuring the highest levels of clean and complete combustion.
The unique characteristics of the combustor 12 greatly diminish both fuel size and fuel feed sensitivity. “On the Fly” fuel changing capability fosters multi-fuel and gross-fuel applications of the rotary cascading bed combustion system 10.
The following characteristics are in accordance with one embodiment of the combustor 12:

- Length=45 feet
- Internal Diameter=12 feet
- Nominal Capacity=60,000 pounds of steam/hr
- Steam Temperature=825 degrees Fahrenheit
- Steam Pressure=865 psia or Saturated Steam=250 psia
- Feedwater Temperature=240 degrees Fahrenheit
- Maximum Combustion Gas Temp.=1,650 degrees Fahrenheit
- Combustor 12 Discharge Temperature=1,400 degrees Fahrenheit
- Discharge Temperature to Baghouse=300 degrees Fahrenheit
- Combustion Gas Flow Range=70,000-95,000 lbs/hr
- Fuels (Typical)=High Sulfur Coal, coal wastes, refuse derived fuels—municipal wastes—semi-densified refuse derived fuels—municipal wastes—fluff, carpet and carpet scrap, wood wastes, tires and rubber wastes, oils, solvents and industrial sludges, and mixtures thereof.

Other modulized system elements include:

- Collection Systems
- Recycling and Waste to Energy Processing Systems
- Fuel Storage and Fuel Feed Modules
- Electrical Generation Systems
- Ash Utilization Systems
- Advantages of the present subject matter include:
- The rotary cascading bed combustion system 10 can burn a wide variety of fuels in environmentally acceptable manner.
- Fuels can be changed “on the fly” without shutting down or losing the desired steam conditions.
- Fly ash has the potential for beneficial uses as a soil conditioner, fertilizer ingredient or construction material additive.

In operation, combustion occurs in a rotating cylinder 14. The rotating cylinder 14 cascades the fuel to facilitate the mixing of air and solids for better burn out. Fuel and sorbents are recycled internally to help obtain greater carbon utilization and acid gas capture. If carbon burnout is not complete it will be recycled back into the combustion chamber. The rotational speed of the cylinder is varied based on the amount of fuel, airflow and combustion properties. Limestone can be added to control acid gases. The temperature of combustor is monitored and controlled with fuel and air rates.
There are three sections of system 10, including (1) municipal waste management; (2) boiler and exhaust; and (3) electricity generation.
(1) Municipal Waste Management

- Fuel discharge and storage.
  - Truck scale to weigh incoming material
  - Concrete floor, tractor-loader, concrete block bunkers
- Material recovery facility (MRF).
  - Conveyers, specialized equipment and sorting line to capture recyclable and non-combustible materials (metal, plastics and electronics)
- Recycle storage and shipment.
  - Compressing and bailing of recyclables
  - Shipping docks

(2) Boiler and Exhaust

- Feed conveyers and primary fuel supply to boiler.
- Sorbent supply to boiler.
- Rotating cylindrical combustion zone with internal flow control, internal tube bundle and internal solids recycle system.
- Mechanical dust collector connected to external ash collection system that can recycle ash to the burner or discharge.
- External heat exchanger containing a super-heater to transfer additional heat to produce steam and to reduce temperature of exhaust gas.
- Bag house to remove particulate matter from the combustion gas stream before discharge to the stack.
- Control and monitoring system that monitors the stack gases and both controls the system and provides pollution monitoring reporting.
- Feed water system and steam controls.
- Exhaust stack to meet local requirements.

(3) Electricity Generation

- Steam powered turbine to convert steam energy to electricity.
- Steam piping from RCBC to turbine.
- Electricity control system.
- Electric transmission from turbine.

The general benefits of the rotary cascading bed combustion system 10 include (1) Designed to be fuel flexible—from coal, solid waste, biomass with no more than 25% moisture content; (2) Fuel stays in the burn zone for an extended period of time to facilitate elimination of water and to produce a total burn off; (3) Combustion is accomplished at lower temperatures to control NOx; and (4) No moving parts are in the high-temperature burn zone. The total-burnout results in proven EPA approved low emissions and non-toxic x-soil used in land reclamation and green construction.
More specifically, benefits include:

- Significantly lower capital cost
  - Simple design
  - Low temperature process
  - No need for complex and costly chemical scrubbing equipment for exhaust gases to meet air quality requirements.
- Significantly lower operational cost
  - Feed fuel can vary “on the fly” with no shut-down or batch changes
  - No costly chemical scrubbing agents, electrodes or specialized parts
  - No moving parts in the burner
- The most complete burn of any process
  - 99.99+% proven carbon destruction is possible because of the cascading and recycling of fuel during the combustion. This leaves less than a small fraction of the fuel material, x-soil, that can be used in land reclamation and green construction.

Following long-standing patent law convention, the terms “a,” “an,” and “the” refer to “one or more” when used in this application, including the claims. Thus, for example, reference to “a subject” includes a plurality of subjects, unless the context clearly is to the contrary (e.g., a plurality of subjects), and so forth.
Throughout this specification and the claims, the terms “comprise,” “comprises,” and “comprising” are used in a non-exclusive sense, except where the context requires otherwise. Likewise, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.
For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing amounts, sizes, dimensions, proportions, shapes, formulations, parameters, percentages, quantities, characteristics, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about” even though the term “about” may not expressly appear with the value, amount or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are not and need not be exact, but may be approximate and/or larger or smaller as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art depending on the desired properties sought to be obtained by the presently disclosed subject matter. For example, the term “about,” when referring to a value can be meant to encompass variations of, in some embodiments, ±100% in some embodiments ±50%, in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments±0.5%, and in some embodiments±0.1% from the specified amount, as such variations are appropriate to perform the disclosed methods or employ the disclosed compositions.
Further, the term “about” when used in connection with one or more numbers or numerical ranges, should be understood to refer to all such numbers, including all numbers in a range and modifies that range by extending the boundaries above and below the numerical values set forth. The recitation of numerical ranges by endpoints includes all numbers, e.g., whole integers, including fractions thereof, subsumed within that range (for example, the recitation of 1 to 5 includes 1, 2, 3, 4, and 5, as well as fractions thereof, e.g., 1.5, 2.25, 3.75, 4.1, and the like) and any range within that range.
Although the foregoing subject matter has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be understood by those skilled in the art that certain changes and modifications can be practiced within the scope of the subject matter.

Claims

What is claimed is:

1. A rotary cascading bed combustion system for converting waste product into energy, the rotary cascading bed combustion system comprising:

a rotary cascading bed combustor boiler including a rotating cylinder surrounding a combustion chamber;

the rotating cylinder being structured and disposed for cascading the fuel to facilitate the mixing of air and solids, wherein the rotational speed of the rotating cylinder is selectively varied based on the amount of fuel, airflow and combustion properties;

wherein combusting waste is mixed with sorbents and cycled through a plurality of combustion zones to produce controlled heat for generating steam;

wherein the steam is routed to a turbine; and

wherein if carbon burnout is not complete it will be recycled back into the combustion chamber.