System and Method for Waste Incineration

Abstract

Systems and methods for incinerating waste solids are disclosed. A fluidized bed of solid particles is provided at an elevated temperature in a reactor. The waste stream, comprising the waste solids and water, is passed onto the fluidized bed of solid particles. The fluidized bed of solid particles has a sufficiently elevated temperature to vaporize substantially all of the water into an offgas stream. The waste solids are mixed among the bed of solid particles. Sufficient heat and oxygen are provided to incinerate the waste solids.

Description

TECHNICAL FIELD

The systems and methods described herein relate generally to treatment of waste solids.

BACKGROUND

Waste streams, especially blackwater streams, require careful treatment. On a large scale, traditional bioreactors and sludge treatment is capable of disposing of this material. On a small scale, such as in recreational vehicles, blackwater is typically an annoyance at best and a significant hurdle at worst. Other small scale blackwater producers include remote work sites and cabins. Traditional treatment methods are typically too large in scale or too impractical to implement for a single recreational vehicle, remote work site, or cabin. Simplifying the disposal of waste solids, especially blackwater solids, is required.

SUMMARY

In a first aspect, the disclosure provides a method for incinerating waste solids. A fluidized bed of solid particles is provided at an elevated temperature in a reactor. The waste stream, comprising the waste solids and water, is passed onto the fluidized bed of solid particles. The fluidized bed of solid particles has a sufficiently elevated temperature to vaporize substantially all of the water into an offgas stream. The waste solids are mixed among the bed of solid particles. Heat and oxygen are provided to incinerate the waste solids.

In a second aspect, the disclosure provides a system for incinerating waste solids. A fluidized bed reactor is provided with a fluidized bed of solid particles at an elevated temperature. An inlet is configured to pass the waste stream, consisting of the waste solids and water, onto the bed of solid particles. The fluidized bed of solid particles has a sufficiently elevated temperature to vaporize substantially all of the water into an offgas stream. The fluidized bed reactor is further configured to mix the waste solids among the fluidized bed of solid particles and to provide heat and oxygen to incinerate the blackwater solids.

Further aspects and embodiments are provided in the foregoing drawings, detailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are provided to illustrate certain embodiments described herein. The drawings are merely illustrative and are not intended to limit the scope of claimed inventions and are not intended to show every potential feature or embodiment of the claimed inventions. The drawings are not necessarily drawn to scale; in some instances, certain elements of the drawing may be enlarged with respect to other elements of the drawing for purposes of illustration.

FIG. 1 is a cross-sectional elevation view of a fluidized bed reactor.

FIG. 2 is a cross-sectional elevation view of a fluidized bed reactor with heat exchangers.

FIG. 3 is a cross-sectional elevation view of a fluidized bed reactor with a sizing system.

FIG. 4 is a cross-sectional elevation view of a fluidized bed reactor with a preheater.

FIG. 5 is a transparent isometric top, side, front view of a recreational vehicle with a system for incinerating waste solids.

DETAILED DESCRIPTION

The following description recites various aspects and embodiments of the inventions disclosed herein. No particular embodiment is intended to define the scope of the invention. Rather, the embodiments provide non-limiting examples of various compositions, and methods that are included within the scope of the claimed inventions. The description is to be read from the perspective of one of ordinary skill in the art. Therefore, information that is well known to the ordinarily skilled artisan is not necessarily included.

DEFINITIONS

The following terms and phrases have the meanings indicated below, unless otherwise provided herein. This disclosure may employ other terms and phrases not expressly defined herein. Such other terms and phrases shall have the meanings that they would possess within the context of this disclosure to those of ordinary skill in the art. In some instances, a term or phrase may be defined in the singular or plural. In such instances, it is understood that any term in the singular may include its plural counterpart and vice versa, unless expressly indicated to the contrary.

As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. For example, reference to “a substituent” encompasses a single substituent as well as two or more substituents, and the like.

As used herein, “for example,” “for instance,” “such as,” or “including” are meant to introduce examples that further clarify more general subject matter. Unless otherwise expressly indicated, such examples are provided only as an aid for understanding embodiments illustrated in the present disclosure and are not meant to be limiting in any fashion. Nor do these phrases indicate any kind of preference for the disclosed embodiment.

As used herein, “sizing,” or “sized,” are terms of comminution. Solids are “sized” or “comminuted” when they are crushed, ground, shredded, pulverized, macerated, or otherwise reduced in size to a desired particle size.

As used herein, “fines” is meant to refer to a size that is finer than a minimum size required to pass through an orifice. In the case of the blackwater solids, they are sized to fines when they can pass through a spray nozzle.

The small-scale waste stream producer is typically underserved in industry. Small-scale waste stream producers, including recreational vehicles, remote work sites, third-world villages, and remote cabins, typically cannot afford expensive waste treatment systems. Blackwater, consisting of components selected from the group consisting of water, urea, fecal matter, paper products, hygiene products, and combinations thereof, is the most typical waste stream envisioned, but other waste streams, such as food waste, may be treated by the methods and systems described herein. The disclosed invention, as related to recreational vehicles, can be used as part of a “Never Dump/Never Fill” philosophy for recreational vehicles. Recreational vehicle users typically dread the dumping part of recreational vehicle usage. As a part of the “Never Dump” philosophy, the inventions disclosed describe systems and methods for waste solids disposal accomplished without user involvement, eliminating dumping.

In a preferred embodiment, the waste streams are those of a small-scale waste stream producer. A fluidized bed of solid particles is provided at an elevated temperature in a reactor. The waste stream, with waste solids and water, are passed onto the fluidized bed. The fluidized bed is at a sufficiently elevated temperature to vaporize substantially all of the water into an offgas stream. The waste solids are then mixed among the fluidized bed and heat and oxygen are provided to incinerate the waste solids. In a preferred embodiment, “substantially all of the water” is more than 50 wt % of the water. In a more preferred embodiment, “substantially all of the water” is more than 70 wt % of the water. In a most preferred embodiment, “substantially all of the water” is more than 90 wt % of the water. In any event, a substantial portion of the water is vaporized.

FIG. 5 is a transparent isometric top, side, front view of a recreational vehicle with a system for incinerating waste solids at 500 that may be used in a preferred embodiment of the present invention. The recreational vehicle 11 contains a toilet 44 that passes blackwater to a holding tank 46. The blackwater is pumped by pump 48 to fluidized bed reactor 10 where the blackwater solids are incinerated. Fluidized bed reactor 10 is described in various embodiments in FIGS. 1 through 4.

Now referring to FIG. 1, FIG. 1 is a cross-sectional elevation view of a fluidized bed reactor at 100 that may be used in one embodiment of the present invention. The fluidized bed reactor 10 contains a fluidized bed of solid particles 14 above burners 18 as well as spray nozzles 12 and a particulates filter 16. The fluidized bed of solid particles 14 is heated to an elevated temperature by fuel 34 being combusted in fluidizing air 32. When the elevated temperature is reached, a waste stream 30, comprising waste solids and water, is sprayed through the spray nozzles 12 onto the fluidized bed of solid particles 14. The elevated temperature is sufficiently high to vaporize substantially all of the water into an offgas stream. The waste solids then mix with the fluidized bed of solid particles 14 and heat and oxygen are provided to incinerate the waste solids. The waste solids incinerate to form typical combustion products, including but not limited to carbon dioxide, water, and solid particulates. The offgas stream mixes with these combustion products and the vaporized water and passes through particulate filter 16, leaving particulates behind, with the balance of the offgas stream 36 leaving through a top portion of the reactor 10. In some embodiments, the particulate filter is cleaned by incinerating the particulates further. This embodiment described is a batch process. In some embodiments, sufficient heat is provided by fuel 34 that the fluidized bed is kept above the elevated temperature such that continual addition of blackwater can be maintained. In some embodiments, the fluidized bed of solid particles consists of sand. The particles of sand are preferably 0.1 to 1 mm in size for ease of fluidization. In other embodiments, the fluidized bed of solid particles consists of gravel or small pebbles. In other embodiments, the fluidized bed of solid particles consists of metal beads. In other embodiments, the fluidized bed of solid particles consists of ceramic beads. In some embodiments, the solid particles have pores sufficiently large for bulk flow of liquids into and gases out of the pores. In a preferred embodiment, the solid particles are made of a material with a heat capacity of at least 800 J/kg K.

FIG. 2 is a cross-sectional elevation view of a fluidized bed reactor with heat exchangers at 200 that may be used in one embodiment of the present invention. The fluidized bed reactor 10 contains a fluidized bed of solid particles 14 above burners 18 as well as a spray nozzles 12 and a particulates filter 16. A first heat exchanger 20 and a second heat exchanger 22 are provided. The fluidized bed of solid particles 14 is heated to an elevated temperature by fuel 34 being combusted in fluidizing air 32. In a preferred embodiment, the elevated temperature is at least 400° C. When the elevated temperature is reached, a hot blackwater stream 40, consisting of waste solids, water, and urea, is sprayed through the spray nozzles 12 onto the fluidized bed of solid particles 14. The waste solids include fecal matter, paper products, and hygiene products sized by comminution sufficient to pass through the nozzles 12. This is preferably smaller than ⅛″ diameter. The elevated temperature is sufficiently high to vaporize substantially all of the water into an offgas stream. The waste solids then mix with the fluidized bed of solid particles 14 and heat and oxygen are provided to incinerate the waste solids. The waste solids incinerate to form typical combustion products, including but not limited to carbon dioxide, water, and solid particulates. The offgas stream mixes with these combustion products and the vaporized water and passes through particulate filter 16, leaving particulates behind, with the balance of the offgas stream 36 leaving through a top portion of the reactor 10. The offgas stream 36 is passed against a feed blackwater stream 30 in the first heat exchanger 20 to form a warmed blackwater stream 38, which is heated in a second heat exchanger 22 to form a hot blackwater stream. In some embodiments, the hot blackwater stream is near the boiling point of water at the pressure in the system. In a preferred embodiment, “near” is within 5° C. below the boiling point of water. In a more preferred embodiment, “near” is within 3° C. below the boiling point of water. In a most preferred embodiment, “near” is within 1° C. below the boiling point of water.

FIG. 3 is a cross-sectional elevation view of a fluidized bed reactor with a sizing system at 300 that may be used in one embodiment of the present invention. The fluidized bed reactor 10 contains a fluidized bed of solid particles 14 above burners 18 as well as a spray nozzles 12 and a particulates filter 16. A comminution system consisting of a vessel 24 with a shredder 26 and a recirculating pump 28 is provided. The comminution system receives a blackwater stream 30, consisting of waste solids, water, and urea. The waste solids include fecal matter, paper products, and hygiene products. The comminution system shreds the waste solids in the blackwater stream until the average particle size of the blackwater solids is sufficiently small to pass through the nozzles 12. The fluidized bed of solid particles 14 is heated to an elevated temperature by fuel 34 being combusted in fluidizing air 32. When the elevated temperature is reached, the sized blackwater stream 40 is combined with a fuel stream 42, such as diesel, and is sprayed through the spray nozzles 12 onto the fluidized bed of solid particles 14. The elevated temperature is sufficiently high to vaporize substantially all of the water into an offgas stream. The waste solids then mix with the fluidized bed of solid particles 14 and heat and oxygen are provided to incinerate the waste solids. The added fuel stream 42 assists in complete incineration. The waste solids incinerate to form typical combustion products, including but not limited to carbon dioxide, water, and solid particulates. The offgas stream mixes with these combustion products and the vaporized water and passes through particulate filter 16, leaving particulates behind, with the balance of the offgas stream 36 leaving through a top portion of the reactor 10.

FIG. 4 is a cross-sectional elevation view of a fluidized bed reactor with a preheater at 400 that may be used in one embodiment of the present invention. The fluidized bed reactor 10 contains a fluidized bed of sand 14 above spargers 18 as well as spray nozzles 12 and a particulates filter 16. Fluidizing air 32 is heated to a temperature T1 in heat exchanger 22. The fluidized bed of solid particles 14 is heated to an elevated temperature T2 by the fluidizing air. T2 is below T1. When the elevated temperature T2 is reached, a waste stream 30, comprising waste solids and water, is sprayed through the spray nozzles 12 onto the fluidized bed of solid particles 14. The elevated temperature is sufficiently high to vaporize substantially all of the water into an offgas stream. The waste solids then mix with the fluidized bed of solid particles 14 and heat and oxygen are provided from the incoming fluidizing air 32 to incinerate the waste solids. Temperature T1 is sufficiently high that the waste solids combust in the fluidizing air. The waste solids incinerate to form typical combustion products, including but not limited to carbon dioxide, water, and solid particulates. The offgas stream mixes with these combustion products and the vaporized water and passes through particulate filter 16, leaving particulates behind, with the balance of the offgas stream 36 leaving through a top portion of the reactor 10. In some embodiments, the particulate filter is cleaned by incinerating the particulates further.

In a preferred embodiment, mixing the waste solids among the fluidized bed of solid particles provides sufficient fluidizing pressure to prevent downflow of any liquid content remaining entrained with the waste solids.

In some embodiments, the fluidized bed of solid particles is selected from the group consisting of ceramic balls, steel balls, stainless-steel balls, rocks, and combinations thereof. In some embodiments, the solid particles are all the same size. In other embodiments, the solid particles are of various sizes.

The invention has been described with reference to various specific and preferred embodiments and techniques. Nevertheless, it is understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.

Claims

1. A method for incinerating waste solids comprising:

providing a fluidized bed of solid particles at an elevated temperature in a reactor;

passing the waste stream, comprising the waste solids and water, onto the fluidized bed of solid particles, wherein the fluidized bed of solid particles has a sufficiently elevated temperature to vaporize substantially all of the water into an offgas stream;

mixing the waste solids among the fluidized bed of solid particles; and

providing sufficient heat and oxygen to incinerate the waste solids.

2. The invention of claim 1, wherein more than 50 wt % of the water in the waste stream is vaporized.

3. The invention of claim 1, wherein fuel is added to the waste stream to assist in incineration of the waste solids.

4. The invention of claim 1, wherein mixing the waste solids among the fluidized bed of solid particles provides sufficient fluidizing pressure to prevent downflow of any liquid content remaining entrained with the waste solids.

5. The invention of claim 1, wherein incinerating the waste solids produces particulates that entrain in the offgas stream.

6. The invention of claim 5, wherein the offgas stream and the particulates are passed through a particulate filter, the particulate filter trapping the entrained particulates.

7. The invention of claim 6, further comprising incinerating the particulates on the particulate filter.

8. The invention of claim 1, wherein the fluidized bed of solid particles are selected from the group consisting of ceramic balls, steel balls, stainless-steel balls, rocks, and combinations thereof.

9. The invention of claim 1, further comprising preheating the waste stream before the waste stream is passed onto the fluidized bed of solid particles such that the waste stream is at a boiling point of the water.

10. The invention of claim 1, further comprising sizing the waste solids to fines before the waste stream is passed onto the fluidized bed such that the waste stream is passed onto the bed of solid particles through a spray nozzle.

11. The invention of claim 1, wherein the waste stream further comprises urea.

12. The invention of claim 1, wherein the waste solids are selected from the group consisting of fecal matter, paper products, hygiene products, and combinations thereof.

13. A system for incinerating waste solids comprising:

a fluidized bed reactor comprising a fluidized bed of solid particles at an elevated temperature;

an inlet configured to pass the waste stream, comprising the waste solids and water, onto the bed of solid particles, wherein the fluidized bed of solid particles has a sufficiently elevated temperature to vaporize substantially all of the water into an offgas stream;

the fluidized bed reactor further configured to mix the waste solids among the fluidized bed of solid particles and to provide heat and oxygen to incinerate the blackwater solids.

14. The invention of claim 13, wherein more than 50 wt % of the water in the waste stream is vaporized.

15. The invention of claim 13, wherein the fluidized bed reactor is further configured to mix the waste solids and the fluidized bed of solid particles with sufficient fluidizing pressure to prevent downflow of any liquid content remaining entrained with the waste solids.

16. The invention of claim 13, wherein incinerating the waste solids produces particulates that entrain in the offgas stream.

17. The invention of claim 16, further comprising a particulate filter configured to have the offgas stream and the particulates pass through and trap the entrained particulates.

18. The invention of claim 13, further comprising a preheater configured to preheat the waste stream before the waste stream is passed onto the fluidized bed such that the waste stream is at a boiling point of the water.

19. The invention of claim 18, wherein the preheater is further configured to receive heat from the offgas stream for part of preheating the waste stream.

20. A waste treatment system for a recreational vehicle, comprising the system of claim 13.