WO2012027805A1

WO2012027805A1 - Combustor module for pelletized solid mass

Info

Publication number: WO2012027805A1
Application number: PCT/BR2010/000286
Authority: WO
Inventors: Thierry Constant Eddy François GAUTHIER
Original assignee: Gauthier Thierry Constant Eddy Francois
Priority date: 2009-09-01
Filing date: 2010-09-01
Publication date: 2012-03-08
Also published as: BRPI0903727A2; BRPI0903727B1; BRPI0903727E2

Abstract

The present invention refers to a burner module (1 ) comprising an air diffuser box (2), cylindrical combustion chamber (3), central flanged face (4), and tubular grid (5), which, in single and compact modular assembly, allow the maximizing of calorific power exploitation of several pelletized solid materials, including the organics and with ash contents greater than 1 %, through the optimization of inner flows formed by air, fuel material and burned material flow in a continuous movement of circulation and replacement of elements, allowing the efficient removal of all generated ash during the combustion by percolation between the gaps of new material and the grid (5), operating in minimally fluidized bed, forming a projected flame out of ash, sparks and unburned or partially burned fuel material, allowing intermittent burning cycles of greater yield and final power generated, greater stability of process and direct reduction of undesired effects on environment in terms of gases and combustion waste.

Description

COMBUSTOR MODULE FOR PELLETIZED SOLID MASS

The present invention refers to a burner module for pelletized solid fuel, comprising an open flame combustion chamber, endowed with a bed of cylindrical tubes longitudinally drilled and arranged in a inclined grid shape. The tubes are inflated with air from a tangential discharge turbine, it forming on the grid, via air flow through holes arranged in line along the tubes, an air mattress able to keep the burned fuel material upwards suspended on minimally fluidized bed, while new combustible material is restored on the grid vertically and downward, it forming, together with the action of a horizontal airstream coming from a division of the airflow from the turbine, a continuous circulation movement and replacement of combustion material. This allows the effective removal of all ash generated during percolation combustion between the gaps of the new material and the grid, forming a projected fire out of ash, sparks and unburned or partially burned fuel material, allowing intermittent burning cycles of greater yield and higher power generation, greater stability of the burning process. The combustor module according to the invention allows even the use of pellets of several renewable organic materials with an optimized exploitation of its calorific power, reducing the undesired effects on the environment in terms of gas and combustion waste.

Field of invention

The present invention relates to the fields of mechanical engineering and chemistry, especially in thermodynamic cycles and thermal exploitation of biomass.

Prior art

Open combustion systems for calorific energy generation are widely used around the world, since the earliest times and in several application situations, such as steam generation in boilers, heating of equipment for drying purposes, heating of shaping devices, of ovens, of environments and for general fluids heating.

The power demanded by the application, as well as issues relate to the generation cost per kW, the availability and , in more current terms, the environment, the renewability and economic, social, and environmental sustainability, determine the ideal type of burner equipment and the fuel nature to be used.

The most commonly employed fuels and still dominant in some sectors, are derivatives of hydrocarbons and, more recently, alternative sources have been object of study, experiences, and of growing interest due to the announced depletion of fossil materials, foreseen for the next decade.

Among the solid natural fuels in application and constant improvement, stand out the sugarcane bagasse and elephant grass, husks of grains, of fruits, of leguminous, of oleaginous, and of trees, corn husk and corn fiber, reforested wood, sawdust, among others, existing them available in various forms, one being the dry form, crushed and compacted, known as briquettes, or it granulated version, the pellets.

Once defined the energetic scope basically formed by the matrix which comprises pellets of biomass as a fuel, and burner of open flame as heat energy exploiter, it is necessary to evaluate it in more detail and discretion.

Although there are increasing studies and development to expand the spectrum of fuels, the combustor units today are, by technical limitations such as ash content, sized and designed for specific fuels, or rather to a particular original material or specific family of fuels, having its performance limited when subjected to different fuels, which underscores the relative lack of flexibility, very important for both the adequacy of the generation costs to the desired purpose as for the ecological matrix, for example, to cultures rotation or in times of scarcity or climate and economic crises.

The ash content originally present in each type of fuel becomes an obstacle with respect to the use of different and new alternative fuels, since current combustors of biomass pellets are limited to fuels with ash contents less than or equal to 1 % (one percent). Values greater than this, cause problems in the quality of burning, which unintended effects are frequently the fall in yield and generated power and the formation of soot and smoke, in addition to only partial combustion of part of the fuel material fed to the furnace.

These cited technical limitations are even more ample if we consider the exploit of the calorific power of each fuel type, still insufficient in terms of yield per burned kilogram or ton, remembering that the pellet material is subministered to the burner cyclically, according to the combustion chambers volume and burning capacity of the unit.

Moreover, both the quality of the burn as the internal flow of waste are not ideal, existing a surplus of ash and unburned material not removed at each cycle and mixed with new material fed cyclically, which greatly reduces the generated power, causing partial and also cyclical disruption in combustion and demanding the constant ignition of the fuel, due to the increase of activation energy to be transposed into each new start of burning, having the need to sustain the burning by auxiliary and expensive means, such as gas pilot lights or even electric resistance.

There have been made several attempts to improve the caloric employment of burning biomass pellets starting in the improvement of air flow in the combustion chamber, as illustrated in, for example, the Brazilian publication number BRMU8702268 (U), filed on 07/12/2007, which suggests the air insufflation into the combustion chamber in turbulent and direct way on the material in combustion what, to one skilled in the art, improves but does not eliminate the hereinabove mentioned problems with respect to the quality of the internal flow of air, fuel and ashes.

Another proposal is suggested by application number PI0400436-1 , filed on 3/18/2004, which presents an additional water tubing driven into the interior of the combustion chamber to increase the exploitation of heat and also generate steam, causing, however, increase of costs and not solving in a effectively way the issues relating to the internal flow of air, fuel and ash.

Furthermore, there are solutions presenting mobile grills and others disposing fans or turbines vertically mounted, citing only a few alternatives that because of their technical limitations fall short on the internal flow of materials.

The presence of ash, sparks and unbumed or partially burned material, is extremely harmful for the yield of burning and much more for the subsequent systems connected to the open combustion chamber, such as serpentines (coils) and air and/or exhaustion ducts. Besides the risk of fires and smoke formation in descending column, very undesirable side effects are the occurrence of grime, the deterioration and clogging of ducts and gaps, resulting in maintenance intervals of higher frequency what, therefore, increases operating costs.

Another problem encountered concerns to the hygroscopic characteristics of many biomasses, resulting in the humidification or addition of water of the granulated and consequently in the reduction of thermal energy exploitation, because an important part of energy is consumed for evaporation of the moisture.

All the difficulties mentioned so far make evident why the biomass pellet burners are still used in small scale and why they still do not represent a viable and flexible enough alternative for the substitution of other models currently applied. Background of the invention

Combustor module for pelletized solid mass, object of the present invention, in order to solve the problems related to the current state of the art, presents an optimized solution to the increase of exploitation of heat power of compressed and granulated biomass, generating thermal energy by combustion at economically attractive cost per kWh (or kJ or kcal) produced, based on the following premises:

A) provide a compact combustor module with generating capacity superior to the similar available of equal dimension, amplifying the range of applications and enabling use in industrial systems for medium and large;

B) provide a compact combustor module with generating capacity using from various types of biological fuel;

C) provide a compact combustor module capable of operating even with fuel of ash contents greater than 1 %;

D) provide a compact combustor module provided with a furnace with optimized and constant internal flow of air, fuel material and ash;

E) provide a compact combustor module of a burn yield never less than 97%, or η = 0.97, where "η" represents the direct relationship between the amount of fuel oxidized and the originally provided of fuel; and

F) provide a compact combustor module provided with a furnace capable of carrying out the burning of dry or partially humidified pelletized material, without resulting in significant losses of yield.

Therefore, the subject of the present invention is based on several mechanical, thermodynamic and chemical principles, in addition to practical results of exhaustive testing of functional prototypes, housing the fundamental issue in the optimization of internal flows of the combustion chamber.

The creation of a mixed and optimized flow of air, fuel material and ash is only possible from the perfect combination and harmony of the supplying sources of each element.

In one preferred embodiment, the subministration of air for combustion and for flame projection is made through a tangential discharge turbine, and the air drive must have a driver circuit provided with bifurcations for perfect administration of the dosage required for each stage of burning. The presence of ash as well as unburned or badly burned material is a huge impediment to the process yield, and is avoided according to the invention by introducing into the grid a minimally fluidized bed, allowing to maintain part of the ash in suspension close to the surface of the grid and other part permeating through the gaps or sliding over the inclined grid, i. e., keeping the waste material in continuous motion and removing it from the chamber. The suspension of part of the ash is obtained through small diameter holes arranged along the tubular elements of the grid. Part of the air from the air turbine is diverted to the interior of the grid tubes, closed at the opposite end of the air supply, forcing the passage of air flow through the orifices of the holes, creating an air mattress.

Furthermore, the invention provides that the inclination of the grid is upward toward the flame discharge, forcing the sliding of the ash to the top of the grid and then to the accumulator box, located at the bottom of the chamber.

The intermittent loading of fresh fuel should occur in perfect synchrony with the completion of the burning of the previous load, being the new load dumped inside the combustion chamber, it mixing with some of the ash in suspension and forcing it down and between the gaps on the grid, configured to prevent passage of granules.

Thus, and with a grid of adequate geometric arrangement and proper slope, it will create a continuous cycle, efficient and effective of feeding, combustion, ash removal and renewal of combustible material.

Practical tests of easy reproduction and with usual market materials proved the considerations made above and resulted in compact models of burner, which obtained, burning, for example, grass pellets of a graminaceous plant of the genre Brachiaria, an average calorific power "a" of 4.000 kcal/kg (a = 4.000 kcal/kg), with an ash content greater than 1% and 8% of humidity, with the following results:

1 ) generated power greater than 3.000kW (or 3000 kJ/s),

2) burn volume close to 17 kg/min, and

3) burning yield of 97,5% (η = 0,975).

Additional tests were carried out using fuels with ash contents up to 6%, obtaining similar results to those presented above, demonstrating the flexibility of the object of the present invention.

The magnitude and importance of these results are evident when compared to the results obtained with units of the same dimensional size, manufactured and marketed by the world's most experts in the field, tested with the same fuel and same environmental conditions, which were:

1 ) generated power between 550 to 10OOkW (or 1.000 kJ/s)

2) burning volume between 3 and 5 kg min and 3) maximum burning yield of 96% (η = 0,96).

These promising results encouraged the inventor to start tests with compact units, based of course on the principle object of the present invention, at heating units of larger sizes, achieving great success.

That said, the present combustor module for pelletized solid mass, provides a compact burner unit for pelletized plant biomass fuel of high performance, flexible to the type of vegetable fuel used, with a structure of simple configuration, maintenance and assembly, confirming its novelty, inventive activity and industrial application.

Brief description of the drawings

For better understanding and visualization of the object of the present invention, the attached drawings depict the combustor module for pelletized solid mass, as follows:

Fig. 1: shows a schematic perspective rear view of the module, object of the present, evidencing its major component elements;

Fig. 2: shows a schematic perspective front view of the module, object of the present, evidencing the cylindrical combustion chamber and the tubular grid;

Fig. 3: shows a schematic rear view of the air diffuser box, evidencing the holes, the arrangement of the grid tubes and deflector plate of the fuel feed;

Fig. 4: shows a schematic perspective lower front view of the module object of the present, evidencing the combustion chamber and its internal components;

Fig. 5: shows schematic perspective lower rear view of the combustion chamber and the central flange face, without the tubular grid, showing a lower opening for ash disposal;

Fig. 6: shows a schematic perspective superior front view of the grid of the combustion chamber, evidencing the arrangement of holes of the grid tubes as well as the orientation of the centers of them toward the center of an imaginary semi-ellipsoid formed by the interconnection of the central lines of said sequential holes, also evidencing, in magnifying glass effect, the space between the tubes of the grid; and

Fig. 7: shows a schematic partial side view of an example of coupling and installation of the module object of the present invention in a pre-existing thermal unit, evidencing the flexibility of the proposed modularity.

Detailed description of the invention Combustor module for pelletized solid mass, object of the present invention, in accordance with the above listed figures, is constituted by a combustor module (1) provided of an air diffuser box (2) and a cylindrical combustion chamber (3), joined together and having a central flange face (4) which outer perimeter edge (4a) is provided with a geometric configuration that allows the fixation of the combustor module (1 ) by screws (PF) in heating units of thermodynamic systems, i.e., in thermal units (UT), pre-existing and already installed ones or belonging to new projects and units.

The air diffuser box (2) has a turbine (2a) of tangential discharge provided at its rear part, attached to an engine (2b) mounted on a support platform (2c), in that the turbine (2a) insufflates air captured from external environment to the inside of the diffuser box (2) through an intake duct (2d), being the volume of air directed into the cylindrical chamber (3) through several air intakes of the central flange face (4).

The cylindrical combustion chamber (3) is formed by an outer mantle

(3a) and an inner mantle (3b), concentric to each other, being the front edge of the inner mantle (3b) provided with passage holes (3c), which directs part of the air coming from diffuser box (4) into the cylindrical combustion chamber (3) and the remaining air to the flame exit (3d), causing additional turbulence near the base of the flame, improving the performance of the burn.

The central flange face (4) has in its upper inner part a crown of holes (4b) for the forming and directing of the flame, which central hole (4c) coincides with the central axis of the cylindrical chamber (3), in addition to side holes (4d) for the feeding of air from the annular space formed by outer mantle (3a) and inner mantle (3b) of the combustion chamber (3).

On the same central flanged face (4) is provided a deflector plate (4e) for the regulation of the fuel fed through the feeding pipe (2e), causing a turbulent insertion of the solid material to the inside of the combustion chamber (3).

Attached to the flanged face (4) are the tubes (5a) of the grid (5), provided with holes (5b), aligned and strung along the tubes (5a), being radially arranged and provided with its central line pointing towards the origin center (5c) of the imaginary semi-ellipsoid (5d) formed by the interconnection of the sequential central lines (5e) of the holes (5b) in the tubes (5a) of the grid (5).

Said grid (5) has its tubes (5a) aligned towards the flame exit (3d), being its central axes parallel to each other or forming small angles between each other, as the grid (5) is inclined upwardly towards the flame exit (3d), forming an inclined and rounded burning bed.

According to a preferred embodiment of the present invention, the gaps (5f) between the tubes (5a) of the grid (5) must always be smaller than the minimum diameter of the pellet material, standardized and previously notified by the pellets manufacturer to allow the passage of the ashes and their fall, by gravity, to the interior of an ashes compartment to be disposed under the lower opening (3e) of the cylindrical chamber (3), and this lower opening (3e) may be provided with a service cover (3f).

For a better understanding of the proposed optimized operation of the object of the present invention, it will be given a sequence description of the burning operation of the present combustor module for pelletized solid mass, starting from a combustion chamber (3) full of pellet material already inflamed, for example, through pilot flame or electrical resistance, conventionally used in burners and perfectly known to those skilled in the art.

The fresh fuel material is introduced into the chamber (3) through the feeding pipe (2e), passing through the deflector plate (4e) and being blown on the minimal fluidization bed, said bed formed on the curved surface of the grid (5) due to the air stream from the holes (5b) of the tubes (5a) in upstream and moved toward the origin center (5c) of the holes (5b).

Over said fluidized bed, ashes of the consumed material are already suspended at the beginning of the operation, which is pressed down by the fresh material beginning to combust and through the gaps (5f) of the grid (5).

The air streams coming from the crown of holes (4b) and the central hole (4c) of the flanged face (4), cause the projection of the flame in the horizontal direction towards the exit direction of the flame exit (3d), the necessary turbulence being obtained through air and fuel projected through the deflector plate (4e) in a perpendicular way to the central axis of the combustion chamber (3).

The air from the side holes (4d), otherwise, is guided by the annular space formed between the outer mantle (3a) and internal mantle (3b) of the combustion chamber (3), discharging in the flame exit (3d) and causing new air and flame turbulence by both the combined action of the passage holes (3c) and the finding of this flow with the flow generated from the crown of holes (4b) and central hole (4c).

Once the fuel material load is consumed, the combustion chamber (3) is reloaded, replacing pelletized material that will fall over the region of the grid (5) and over the suspended ashes on the air stream of the holes (5b) of the tubes (5a) of the grid (5), while the air streams described above are responsible for maintaining active air flow and steady flame.

A combined flow of air, fresh material and ashes is formed, allowing both uniform burning of subministered fresh material as constant discarding of integrally burned material, as well as maintaining uninterrupted the flame directed to the outer of the chamber (3) and into the inside of the thermal unit to be heated.

Claims

1. Combustor module for pelletized solid mass, for modular coupling in pre-existing and installed or new thermal units (UT), characterized in that said combustor module (1 ) is provided in one compact piece, comprising an air diffuser box (2), cylindrical combustion chamber (3), central flanged face (4), and tubular grid (5).

2. Module, according to claim 1 , characterized in that said air diffuser box (2) is equipped with tangential discharge turbine (2a), engine of activation (2b), support platform (2c), inlet duct (2d) and feeding pipe (2e), where the air diffuser box is (2) directly coupled to the cylindrical combustion chamber (3) by a central flanged face (4).

3. Module, according to claim 1 , characterized in that said cylindrical combustion chamber (3) is provided with flame exit (3d) and lower opening (3e) and is provided with concentric mantles called outer mantle (3a) and inner mantle (3b), being the inner mantle (3b) provided with passage holes (3c), radially arranged in its front end near the flame exit (3d).

4. Module, according to claim 1, characterized in that the central flanged face (4) is provided with outer perimeter edge (4a), crown of holes (4b), central hole (4c), side holes (4d) and deflector plate (4e).

5. Module, according to claims 1 or 4, characterized in that said deflector plate (4e) is provided to direct the fuel flow coming from the feeding pipe (2e) in perpendicular axis to the horizontal plane and downwards.

6. Module, according to claim 1 , characterized in that said tubular grid (5) is inclined upwardly towards the flame exit (3d) and consists of a burn cradle or bed formed by tubes (5a) provided with holes (5b) inflated by air from the air diffuser box (2), apart from each other by gap (5f).

7. Module, according to claims 1 or 6, characterized in that said holes (5b) of the tubular grid (5) are radially arranged along the tubes (5a) and provided with central lines (5e) pointing towards the origin center (5c) of a semi- ellipsoid (5d) formed by the interconnection of sequential central lines (5e) of the holes (5b) in the tubes (5a) of the grid (5).