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(11) | EP 2 944 875 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Torsional combustion chamber |
| (57) The present invention relates to a torsional combustion chamber (1) comprising a
cylindrical shell wall (2) with fluid conduction means (3) determining the inner face
(2a) of the wall, the chamber (1) comprising anti-wear means suitable for diverting
the course of the solids or droplets circulating through the inside of the chamber
(1) in the proximities of the inner face of said wall following a course with a component
transverse to the chamber (1) which, in a preferred embodiment, comprise a series
of fins (4) arranged axially with respect to the cylindrical shell wall (2), fixed
on the fluid.
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Technical Field of the Invention
[0001] The invention relates to a type of combustion chamber for gas, liquid or solid fuels, and specifically to a torsional chamber. In such chambers, secondary air introduced through a series of nozzles produces high turbulence of the gas mixture inside the chamber favoring particle retention in the chamber as long as a suitable degree of combustion is not achieved.
Background of the Invention
[0002] Known torsional chambers have a cylindrical shape with a horizontal axis and are provided with nozzles for the entry of oxidizing gas into the chamber. The chambers are closed at one end and provided with an opening at the opposite end for connection to the furnace of a steam generator, for example. Turbulences are intentionally produced in the chamber, keeping fuel particles in suspension and assuring their long residence time in the chamber as well as preventing them from being able to leave the chamber too soon and therefore favoring burning.
[0003] Such torsional chambers are an evolution of a combustion system developed in the 40s based on a small-sized coal cyclone burner, which used the concept of aerodynamic lift of fuel inside a chamber. In this system, ashes generated by combustion melted inside the chamber and were removed from the combustion area in liquid form.
[0004] Although the walls of torsional chambers that evolved from this cyclone burner were originally coated with refractory material, variants in which the cylindrical shell wall was formed by a cooled wall, for example by means of a succession of tubes suitable for the circulation of a fluid medium, such as water, were subsequently disclosed. The introduction of this cooled wall considerably improved the operation of the torsional chamber, maintenance needs being reduced as the use of refractory in the cylindrical shell wall is eliminated. Notwithstanding the foregoing, this variant makes it necessary to protect the cooled wall against wear caused by the impact of the fuel itself and its ashes which are in suspension inside the chamber on said wall. Problems of wear due to cooled wall abrasion accelerates equipment or installation breakdown.
[0005] Coating the cooled wall with hard metals, even if only in the most sensitive areas of the chamber, is not desirable as it significantly reduces the heat exchange between the fluid circulating through the cooled wall and the medium confined by the chamber. It just so happens that this heat exchange is desirable because it reduces the temperature of the ashes generated by combustion in the chamber and favors them being in solid state, which facilitates their extraction from inside the chamber.
[0006] An objective of the present invention is to disclose a torsional chamber particularly suitable for working with fuels with ashes having a low melting point that are particularly abrasive.
[0007] Specifically, an objective of the invention is a chamber solving the problems of abrasion of the cylindrical shell wall without negatively affecting the capacity for cooling the ashes gradually generated during combustion or their continuous extraction from the chamber, i.e., without needing to interrupt the operation of the installation.
Disclosure of the Invention
[0008] The combustion chamber of the invention is a torsional chamber comprising a cylindrical shell wall with fluid conduction means determining the inner face of the wall.
[0009] This chamber is essentially characterized in that it comprises anti-wear means suitable for diverting the course of the solids or droplets circulating through the inside of the chamber in the proximities of the inner face of said wall following a course with a component transverse to the chamber.
[0010] In one embodiment, the anti-wear means comprise a series of fins arranged axially with respect to the cylindrical shell wall, fixed on the fluid conduction means.
[0011] The height of the fins is preferably constant along the length thereof, the height being comprised between 10 and 25 mm.
[0012] In a variant of the invention, the fins project from the inner face of the wall following a radial orientation.
[0014] According to one variant, the fins are regularly spaced throughout the entire circumference of the wall, there being between 12 and 19 fins per quadrant.
[0015] According to another feature of an embodiment of the invention, the fluid conduction means comprises a succession of parallel rings of tubes suitable for conducting the fluid around the axis of the chamber, the tubes being attached or connected to one another to provide a seamless surface forming the inner face of the cylindrical shell wall of the chamber.
[0016] In a variant of this embodiment, the chamber is provided with equipment for stirring up ashes or particles that may be deposited on the inner face of the wall, comprising a pressure wave generator at a front end of the chamber for generating waves that are propagated by the gaseous medium confined by the chamber in a longitudinal direction; and a discharge device at a rear end of the chamber for discharging the ashes or particles that are entrained by the pressure waves towards the mentioned rear end of the chamber.
[0017] The invention envisages that the front end of the chamber is closed by means of a closure wall, perpendicular to the axis of the chamber, not provided with slabs or refractory material and formed by a second fluid conduction means.
[0018] This second fluid conduction means can comprise straight tubes suitable for conducting the fluid, the tubes being attached or connected to one another to provide a seamless surface forming the inner face of the closure wall.
[0019] In a variant of the invention, the chamber comprises an air box completely or partially surrounding the outside of the cylindrical shell wall, there being nozzles establishing communication between the box and the inside of the chamber intended for the entry of a gaseous oxidizer into the chamber.
[0020] The nozzles can be radially distributed along the wall, traversing the fluid conduction means, and can be oriented such that they are tangential to one and the same imaginary cylinder concentric to the wall and having a smaller radius.
Brief Description of the Drawings
[0022]
Figure 1 is a schematic view of a torsional chamber according to the invention, according to a transverse section plane;
Figure 2 is a schematic view of a portion of the cylindrical shell wall of the chamber of Figure 1, including detailed illustrations of those parts highlighted by means of circles;
Figure 3 schematically shows the arrangement of a fin on the tubes forming the fluid conduction means defining the inner face of the cylindrical shell wall of the chamber;
Figure 4 is a schematic view of the torsional chamber according to a longitudinal section plane; and
Figure 5 is a view of the torsional chamber from its front end, the closure wall thereof being depicted as partially transparent in order to show the main components that would be concealed by this closure wall.
Detailed Description of the Drawings
[0023] The torsional chamber 1 of the example comprises a cooled cylindrical shell wall 2. Specifically, this wall 2 comprises fluid conduction means 3 made of steel determining the inner face 2a of the wall 2 which is in contact with the medium confined by the chamber 1.
[0024] As will be described in more detail below, the fluid conduction means 3 is formed by a succession of tubes making up a water circuit.
[0025] As illustrated in Figure 1, in the inner face 2a of the wall 2, in the longitudinal direction and parallel to the generatrices of the wall 2, the chamber 1 is characteristically provided with a series of fins 4, preferably formed by metal plates or flat bars, welded to the inner face 2a of the wall 2, i.e., directly on the fluid conduction means 3.
[0026] In the example, the height of the fins 4 is constant along the length thereof and is 15 mm. In other embodiments, the height of the fins 4 can vary along the length thereof. Likewise, it is also envisaged that not all the fins 4 are identical, fins with a different profile being combined according to their location in the wall 2 of the chamber 1.
[0027] In the example of Figure 1, the fins 4 project from the inner face 2a of the wall 2 following a radial orientation. Nevertheless, the invention envisages that specific inclinations with respect to the radial direction can be selected.
[0028] Although the fins 4 in the example of Figure 1 are regularly spaced throughout the entire circumference of the wall 2 in a regular manner, i.e., they are equidistant from one another, there being between 15 and 16 fins per quadrant, the invention contemplates that the fins 4 are not equidistant from one another and that fins 4 may be concentrated in specific areas.
[0029] In any case, these fins 4 prevent the particles in suspension having a course defined by the system variables (nozzle inclination, air speed, particle density) from hitting the metal wall 2 and therefore prevent the wall from wearing. The fins 4 modify and/or alter the course of these particles such that they prevent these particles from hitting the metal wall 2.
[0030] It must be noted that the fins 4 do not act like a protective shield, i.e., they do not cover the inner face 2a of the wall 2. Therefore, they do not cover the fluid conduction means 3. Accordingly, they do not affect heat transfer. Advantageously, they do not prevent the extraction of ashes either since they will allow, by being parallel to the generatrices of the cylindrical shell wall 2, without being an obstacle, the ashes to move forward, sliding over the inner face 2a of the wall 2 in a longitudinal direction of the chamber 1.
[0031] Contrary to expectations, the height of the fins can be selected such that it protects the inner face 2a of the wall 2 by sufficiently altering the course of the particles to prevent the abrasion of the mentioned inner face 2a of the wall 2, but also such that it does not have an adverse effect on the cyclonic flow that must be followed by the particles in the chamber 1 for the correct operation of the torsional chamber. Incorrect sizing of the fins 4 may alter this cyclonic or spiral flow of the particles.
[0032] In the exemplary chamber 1, the fluid conduction means 3 comprise a succession of parallel rings of tubes 33 suitable for conducting water around the axis (x) of the chamber 1. The tubes 33 are connected to one another by means of a metal membrane so that the surface forming the inner face 2a of the wall 2 is uninterrupted, providing leak-tightness for the medium confined in the chamber 1.
[0033] Figure 3 illustrates the way in which a fin 4 is arranged on the inner face 2a of the wall when the fluid conduction means 3 is formed by this succession of tubes 33 connected to one another by means of a metal membrane 13.
[0034] Returning to Figure 1, which shows that the exemplary chamber 1 comprises an air box 10 completely or partially surrounding the outside of the cylindrical shell wall 2, there being nozzles 11 establishing communication between the air box 10 and the inside of the chamber 1. These nozzles 11 will allow the entry of a gaseous oxidizer, i.e., an air and combustion gas mixture supplying the oxygen required for fuel combustion, into the chamber 1. The air box 10 is provided with a side opening 14 shown in Figure 1.
[0035] The nozzles 11 are distributed in the wall 2 following a specific pattern both in the longitudinal and circumferential distribution, and they will be responsible for the progressive entrance of the oxidizer in flame formation because the oxidizer enters in small suitably distributed portions to achieve staged combustion, which will result in a low NOx level.
[0036] In the example, the nozzles 11 are regularly distributed radially along the wall 2, traversing the fluid conduction means 3 between every two adjacent tubes 33, for which purpose openings are envisaged in the metal membrane 13 connecting the tubes 33. In the illustrated embodiment, the nozzles 11 have an oblong section (see Figure 2), they are taller than they are narrow, fitted into the space available between two adjacent tubes 33, without it affecting the inflow of oxidizing gas in the chamber 1.
[0037] As shown in Figure 1, the nozzles 11 are preferably oriented such that they are tangential to one and the same imaginary cylinder 12 concentric to the wall 2 and having a smaller radius.
[0038] Figure 4 shows that the front end 1 a of the chamber 1 is closed by means of a closure wall 8 perpendicular to the axis (x) of the chamber 1.
[0039] The closure wall 8 is not provided with slabs or refractory material and, like the cylindrical shell wall 2, its inner face is formed by a second fluid conduction means 9 comprising vertically oriented straight tubes 99 suitable for conducting a coolant, preferably water, all as shown in Figure 5.
[0040] Similarly to the wall 2, the tubes 99 are attached to one another by means of a metal membrane to provide a seamless, i.e., an uninterrupted, surface assuring the leak-tightness of the medium confined inside the chamber 1.
[0041] The chamber 1 of the example is provided with equipment for stirring up ashes or particles that may be deposited on the inner face 2a of the wall 2 comprising a pressure wave generator 6 in the closure wall 8 for generating waves that are propagated by the gaseous medium confined by the chamber 1 in a longitudinal direction, i.e., towards the opposite end 1 b; and a discharge device 7 right near the end 1 b of the chamber 1 for discharging the ashes or particles that are entrained by the pressure waves towards the mentioned rear end 1 b of the chamber 1.
[0042] The pressure wave generator 6 works with a compressed air storage tank that releases compressed air over a very short time pulse, generating a blast wave as a result of releasing a significant air mass over a very short time. This sudden depressurization generates a shock wave which transmits energy altering the state of the ash that was deposited on the inner face 2a of the chamber 1 as it moves rapidly inside the chamber 1, this ash in turn being entrained by the gas flow towards the rear end 1 b, enabling the extraction thereof from the chamber 1.
[0043] It must be noted that the rear end 1 b of the chamber 1 depicted in Figure 4 is an end with an opening 15 for connection with a furnace where the flame and/or the already burned gases exit the chamber 1. This opening 15 is provided with a diameter restriction in the form of a frustoconical pipe 16 extending from the opening 15 into the chamber 1. The invention also envisages that the pipe 16 has a cylindrical shape, for example. The purpose of this pipe 16 is to prevent the particles that still have not completed the combustion process from being able to exit the chamber 1 given the helical course of these particles.
[0044] In the lower part of the chamber 1, in the vertical projection of this pipe 16, the wall 2 is provided with a discharge opening 17 giving access to the discharge device 7 for discharging the ashes. This discharge device 7 operates without interrupting combustion in the chamber 1 and can be based on a spring cooled by water in the axis thereof or by a redler submerged in water. The purpose of this element is the possibility of performing a continuous extraction of ashes, maintaining a hydraulic seal inside the chamber 1.
[0045] To contribute to this purpose, the discharge opening 17 has two tilting gates with the capacity to move between two positions: in a first position the gates adopt a coplanar position and they close the passage of the opening; and in a second position the gates adopt a lowered position that does not hinder the passage of ashes which may build up on the gates and are discharged by gravity as said gates adopt the lowered position.
[0046] Figures 4 and 5 also show that the cylindrical wall 2 is provided with tangential openings connected to a side inlet 18, located close to the front end 1 a of the chamber 1 in the example, to allow the entry of combustible gases and/or of small-size solid material which is injected into the chamber 1 preferably by means of pneumatic conveyance.
1. A torsional combustion chamber (1) comprising a cylindrical shell wall (2) with fluid
conduction means (3) determining the inner face (2a) of the wall, the chamber being
characterized in that it comprises anti-wear means suitable for diverting the course of the solids or droplets
circulating through the inside of the chamber in the proximities of the inner face
of said wall following a course with a component transverse to the chamber.
2. The chamber (1) according to the preceding claim, characterized in that the anti-wear means comprise a series of fins (4) arranged axially with respect to
the cylindrical shell wall (2), fixed on the fluid conduction means (3).
3. The chamber (1) according to the preceding claim, characterized in that the height of the fins (4) is constant along the length thereof, the height being
comprised between 10 and 25 mm.
4. The chamber (1) according to claims 2 or 3, characterized in that the fins (4) project from the inner face (2a) of the wall (2) following a radial
orientation.
5. The chamber (1) according to any one of claims 2 to 4, characterized in that the fins (4) are formed by metal plates.
6. The chamber (1) according to any one of claims 2 to 5, characterized in that the fins (4) are regularly spaced throughout the entire circumference of the wall
(2), there being between 12 and 19 fins per quadrant.
7. The chamber (1) according to any one of claims 2 to 6, characterized in that the fluid conduction means (3) comprises a succession of parallel rings of tubes
(33) suitable for conducting the fluid around the axis (x) of the chamber, the tubes
(33) being attached or connected to one another to provide a seamless surface forming
the inner face (2a) of the cylindrical shell wall (2) of the chamber.
8. The chamber (1) according to any one of the preceding claims, characterized in that it is provided with equipment for stirring up ashes or particles that may be deposited
on the inner face (2a) of the wall (2), comprising
- a pressure wave generator (6) at a front end (1 a) of the chamber for generating waves that are propagated by the gaseous medium confined by the chamber in a longitudinal direction; and
- a discharge device (7) at a rear end (1 b) of the chamber for discharging ashes or particles that are entrained by the pressure waves towards the mentioned rear end of the chamber.
9. The chamber (1) according to any one of the preceding claims, characterized in that its front end (1 a) is closed by means of a closure wall (8), perpendicular to the
axis (x) of the chamber, not provided with slabs or refractory material and formed
by a second fluid conduction means (9).
10. The chamber (1) according to the preceding claim, characterized in that the second fluid conduction means (9) comprises straight tubes (99) suitable for
conducting the fluid, the tubes being attached or connected to one another to provide
a seamless surface forming the inner face (8a) of the closure wall (8).
11. The chamber (1) according to any one of the preceding claims, characterized in that it comprises an air box (10) completely or partially surrounding the outside of the
cylindrical shell wall (2), there being nozzles (11) establishing communication between
the box and the inside of the chamber intended for the entry of a gaseous oxidizer
into the chamber.
12. The chamber (1) according to the preceding claim, characterized in that the nozzles (11) are radially distributed along the wall (2), traversing the fluid
conduction means (3), and are oriented such that they are tangential to one and the
same imaginary cylinder (12) concentric to the wall (2) and having a smaller radius.
13. The chamber (1) according to the preceding claim, characterized in that the nozzles (11) have an oblong section.