GRATE FOR HORIZONTAL SOLID FUEL BURNERS

Abstract

 The invention relates to a grate for horizontal solid fuel burners, comprising linear conveyors in the form of screws (3) for moving the fuel along the bed (2), from the fuel loading area (5), which screws are connected to a drive mechanism (4) located outside the shell (1).

Description

Field of the Invention

[0001] The present invention relates to a grate for horizontal solid fuel burners, particularly of solid fuels of the granulated type or the like.

[0002] More specifically, the grate of the invention is of the type comprising means for moving the solid fuel along the grate, from the fuel feed area.

Background of the Invention

[0003] Unlike vertical biomass burners, horizontal biomass burners allow direct use of liquid or gas fuel boilers, simply by replacing one burner with the other, substantial savings therefore being obtained in the budget for modifications in installations due to a change in fuel.

[0004] Unlike other solid fuel burners, since horizontal burners have part of the grate introduced in the shell of the boiler, they have the drawback that they can only be fed from an end thereof. This fact does not present any other type of drawback when the burners are small-sized, where the distribution of fuel along the grate can be done by inertia of the fuel when it drops from the feed device or with the slight mechanical pushing applied by same. As the size of the grate increases, the efficacy of the distribution of the solid along the grate drops and there is a general deterioration in the combustion process, which gives rise to an increase of unburned products, insufficiently cooled areas, etc. To solve this drawback and to allow the development of more powerful burners, with larger-sized grates, various designs are coming out today that allow performing an effective distribution of the solids along the grate: burners having linear moving grates, inclined grates, vibrating grates, distribution systems with linear thrusters, and even combinations of two or more of the preceding systems. Systems of this type have the drawback that the ash and unburned products gradually limit the amplitude of linear motions of said elements, with the subsequent loss in fuel transport yield, or even the jamming thereof occurring. There are also solutions of another type consisting of a rotating, washer drum-type grate, where the solid fuel is stirred, causing the distribution thereof along the grate. However, this solution is expensive.

Description of the Invention

[0005] The object of the present invention is a grate for horizontal solid fuel burners, including a system for distribution of the fuel that allows obtaining greater powers, performing a more efficient and controlled combustion, improving the use that is made of the fuel and reducing the amount of unburned products.

[0006] To that end, the grate is provided with means that move and shake the fuel along the grate, allowing a uniform distribution of the fuel.

[0007] The mentioned means are made up of one or more linear conveyors running on the grate, along same, from the fuel feed area. The linear conveyors are connected to drive means located outside the shell.

[0008] According to a preferred embodiment, the linear conveyors consist of screws or worm gears assembled on supports which withstand the high temperatures reached inside the shell, for example ceramic-type bearings or similar solutions. Furthermore, the core of the worm gears can have a coaxial passage through which a coolant fluid can be circulated.

[0009] The worm gear or worm gears project from the shell on the side in which the fuel loading is located, for the connection thereof to a drive mechanism, which is located outside the shell.

[0010] When the grate has a worm gear, the latter will rotate in the forward movement direction from the fuel loading area, such that it draws said fuel along the grate in a uniform manner.

[0011] When the grate has two or more worm gears, they will all be parallel and can rotate in the same direction, but they will preferably rotate in opposite directions, for example every two consecutive worm gears, such that while some worm gears draw the fuel from the loading area, others do the same in the opposite direction, thereby causing a flow or circuit of fuel on the grate, while at the same time mixing up same, maintaining on the entire grate a homogenous level of fuel, until complete combustion takes place.

[0012] With the described constitution, while some worm gears shift the solid fuel from the feed area along the entire grate of the burner towards the opposite end, others do so in the opposite direction, preventing the accumulation of fuel in any area, regardless of the rate of combustion and of the rotation of the worm gears, making the level of fuel especially on the grate homogenous in any circumstance and making all fuel elements burn in a more uniform manner at their optimal combustion point. This circumstance is furthermore favored by the shaking effect caused by the worm gears on the fuel.

[0013] As an advantage of the grate of the invention in which the linear conveyors are made up of screws or worm gears, it should also be pointed out that since the transport of fuel does not depend on a linear motion, the performance of the system does not vary as much, assuring better control of the heat provided to the boiler at all times. In turn, a mechanism of great mechanical simplicity and reliability results, considerably reducing manufacturing and maintenance costs thereof.

Brief Description of the Drawings

[0014] The attached drawings show a non-limiting embodiment that will allow better understanding the features and advantages of the grate of the invention. In the drawings:

Figure 1 shows a schematic side elevational view of a burner that is provided with the grate of the invention.

Figure 2 shows a schematic plan view of a burner including a possible embodiment of the grate of the invention.

Figures 3 to 5 each shows an embodiment of the grate of the invention.

Detailed Description of an Embodiment

[0015] Figure 1 schematically depicts the shell (1) of a burner, including a grate (2) and a fuel feed device (5). There are arranged on the grate (2) one or more screws or worm gears (3) that are connected to a drive mechanism (4) located outside the shell (1). This drive mechanism can include a motor, transmission and a system for controlling the rotating speed of the worm gear (3).

[0016] The drive mechanism (4) will cause rotation of the worm gear (3) such that the forward movement direction thereof occurs from the fuel loading area (5). The fuel will thereby be drawn along the grate (2) from the loading area. As shown in Figure 2, there can be arranged on the grate (2) several parallel worm gears (3), each of which is connected to its corresponding drive motor (4). With this arrangement and by making the consecutive worm gears rotate in opposite directions, or by manufacturing them with left-handed or right-handed helices, certain worm gears can be made to draw the fuel in the forward movement direction, from the loading area, and other can be made to drive the fuel in the opposite direction, thereby achieving a uniform distribution of the fuel on the grate (2) and a constant mixing thereof.

[0017] With the mentioned arrangement, when the feed system (5) of the burner is activated, depositing the fuel at one end of the grate (2), some actuators move the fuel forward, allowing the transfer from the loading area towards areas farthest away from the grate. The entire grate of the burner is thereby occupied with fuel. When the fuel starts to accumulate in the part opposite the load, the worm gears working in the direction opposite to the normal forward movement direction of the fuel start to be loaded, returning fuel towards the part where feeding takes place. The flow of fuel is therefore closed, circulating inside the burner until the complete combustion thereof takes place, furthermore being able to maintain a homogenous level of fuel on the entire grate, regardless of the rate of rotation of the worm gears or of the fuel feed.

[0018] Since the temperatures reached by the different components will be high, the core of the worm gears (3) can have a coaxial passage, not depicted, through which a cooling cylinder is circulated. Furthermore, the worm gears (3) can be assembled on temperature-resistant supports (5), Figure 1, for example by means of ceramic bearings or bearings of similar type.

[0019] As shown in Figure 3, the grate (2) can be flat, the worm gears (3) running in positions parallel to one another and to the grate (2). The grate (2) could also be grooved, with trapezoidal grooves (6), along each of which a worm gear (3) will run, or else have grooves (7) with an arched bottom, V-shaped bottom, etc. With these arrangements the solid fuel elements located on the lower part of the grate will ascend up to the upper area and those located on the upper part will descend, mixing and ventilating all the fuel uniformly to thus improve the combustion process along the grate.

[0020] The grate of the invention is particularly indicated for being integrated in high-power horizontal biomass burners, because due to its design it can only be fed from one of the ends and, therefore, poor distribution of fuel along the grate occurs. By means of homogenizing the amount of fuel, efficiency is improved and the power of granulated solid fuel systems is increased, in response to the growing needs for power of these systems.

Claims

1. A grate for horizontal solid fuel burners, comprising means for moving the fuel along the grate (2), from the feed area (5), characterized in that the mentioned means consist of at least one linear conveyor running on the grate (2), along same, from the fuel feed area (5), and it is connected to a drive mechanism (4) located outside the shell (1) causing its activation in the forward movement direction from said fuel feed area (5).

2. The grate according to claim 1, characterized in that the drawing means consist of at least two parallel linear conveyors.

3. The grate according to claim 2, characterized in that the consecutive linear conveyors move in opposite directions.

4. The grate according to any one of the preceding claims, characterized in that the linear conveyors run on a flat bed (2).

5. The grate according to any one of the claims 1 to 3, characterized in that the linear conveyors run along a grooved bed (6-7).

6. The grate according to any one of the preceding claims, characterized in that each linear conveyor consists of a worm gear (3).

7. The grate according to claim 6, characterized in that the core of each worm gear (3) has a coaxial passage, through which a coolant fluid is circulated.

Drawing