STEPPED GRILL INCLUDING AN IMPROVED JACK
The hydraulic cylinder with dual-stroke pistons addresses the reliability and maintenance challenges of combustion grates by ensuring controlled movement and easy disassembly, enhancing system stability and reducing downtime.
Patent Information
- Application Number
- FR2023010800
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-10-09
- Publication Date
- 2025-10-03
- Estimated Expiration
- 2043-10-09
AI Technical Summary
Existing combustion grate systems in solid matter incinerators face reliability issues due to variable stroke control, potential equipment breakage, and maintenance complexity from foreign bodies and metal melting, leading to non-uniform forces and increased downtime.
A hydraulic cylinder with two independent chambers and pistons, each with a distinct stroke length, is used to manage normal operation and disassembly positions independently, ensuring reliable and controlled movement of movable bars.
This solution enhances the reliability and safety of the combustion grate system by preventing equipment failure and simplifying maintenance, reducing downtime through controlled disassembly and assembly of movable bars.
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Abstract
Description
Title of the invention: STEPPED GRID COMPRISING AN IMPROVED JACK TECHNICAL FIELD OF THE INVENTION
[0001] The technical field of the invention is that of stepped grates used in combustion furnaces or incinerators of solid materials such as, for example, waste, biomass or solid recovered fuels.
[0002] The invention relates in particular to a stepped grid comprising movable grids actuated by an improved hydraulic cylinder and a method of dismantling said stepped grid. TECHNOLOGICAL BACKGROUND OF THE INVENTION
[0003] Solid matter incinerators comprise grates onto which this fuel is introduced from the top and descends as the combustion process progresses, to exit in the form of ash / clinker at the bottom of the grate, and as fumes in the boiler.
[0004] The combustion grate mechanism allows the fuel to be moved from the entry point to the exit point. Combustion air is injected under the grate, ensuring the fire is stoked and controlled.
[0005] The grate is made up of rows of bars arranged in steps, a fixed part alternating with a movable part. Each step is made up of bars placed on a beam on one side and resting on the bars of the lower step. The beam is preferably tubular to allow rotation of the bar if a foreign body is stuck or metal has melted on the surface of the lower bar. In the rest position (most of the time), the movable bars are under the fixed bars. They slide on these fixed bars, pushing the fuel to advance it. When they return to the rest position, the fuel falls into the free space created by the advancement of the bars. This operation allows the fuel to advance. The fixed bars and the movable bars are supported on each other to guarantee continuity of the stepped grate.
[0006] The rows of movable bars are grouped into modules connected to a drive carriage actuated by at least one hydraulic cylinder. This cylinder has an end-of-stroke sensor for a retracted position and an end-of-stroke sensor for an extended position, thus defining a stroke of the hydraulic cylinder and the bars which can be 300mm. During a stroke of the movable bars, these advance by the length of the stroke of the hydraulic cylinder, pushing the fuel onto the next row of bars.
[0007] When the end-of-travel sensor is triggered, the hydraulic cylinder returns to its retracted position. These end-of-travel sensors are connected to an automated management system, and inform the combustion control system of the proper operation of the grate, by carrying out corrective actions based on the feedback from these end-of-travel sensors.
[0008] Each grid module is independent, and defines a zone of the grid where the temperature is different from another zone, the height of the fuel layer can be adjusted per zone by modifying the back and forth frequency of the moving bars per zone.
[0009] But to carry out the cleaning of the grid in operation or the maintenance, assembly and / or disassembly operations, it is necessary to have the possibility of a longer stroke independently of that used for the combustion of the waste or other similar solid fuel. Indeed, access to each of the bars individually is crucial for the availability of the grid. One of the bars may leak or be a source of blockage, it is imperative to be able to intervene as quickly as possible in order to be able to replace it, if necessary.
[0010] The solution consists of modifying the cylinder actuating the movable bars by adding an overtravel to reach a disassembly position. This allows the movable bars to be completely released from under the fixed bars and removed from above. It then becomes possible to carry out an intervention to replace any bar of the grid via its simplest access, which reduces maintenance times and increases the availability rate of the grid in operation.
[0011] Hydraulically operated cylinders controlled by a control / command system have a certain inertia in response, which can lead to variable strokes that are not fully controlled.
[0012] Furthermore, the limit switch sensors are subjected to an industrial environment which may be hot as well as to possible vibrations which cause them to move slightly, which may modify the end of travel of the cylinder. Furthermore, the inertia of movement of the module is variable in the short and long term, whether due to progressive wear or the structural quality of the waste or fuel.
[0013] Finally, the friction surfaces between two bars are not uniform and constant, and the forces change over time due to the presence of foreign bodies becoming stuck between the fixed bar and the movable bar, or by metals melting on this surface, altering its flatness. All of this can cause jolts and / or non-uniform forces across the width.
[0014] These multiple constraints lead to: • failure to respect the travel of the step over time, which leads to a more complex problem in the event of variable travel of the bars, • risks of failure (loss of end-of-travel information by example) and, • depending on the design of the grids, in extreme cases, there is a risk of equipment breakage, particularly if the mobile bars exceed the maximum permissible length and catch the edge of the previous bar by their rear support or create a risk of product accumulation at the rear of the bar, preventing the mobile bar from resuming its travel and even blocking the mobility of the entire trolley concerned. Summary of the invention
[0015] The invention offers a solution to the problems mentioned above, by making it possible to make the operation of the installation more reliable while limiting the risk of breakage linked to the inertia of the system or to a failure.
[0016] A first object of the invention relates to a stepped grid comprising a frame and movable bars connected to a drive carriage actuated by at least one hydraulic cylinder, it is characterized in that the hydraulic cylinder comprises two independent chambers each having a piston and arranged on either side of the cylinder, a first piston being connected to the drive carriage and a second piston being connected to the frame of the stepped grid and that each chamber is supplied independently of one another.
[0017] In this way, the hydraulic cylinder has a fixed stroke for the movement of the movable bar in waste combustion operations, which makes it possible to overcome reliability problems linked to the response times of the control-command systems (elimination of hazards linked to variable strokes).
[0018] The pistons being mounted in series and powered independently, there is no longer any risk of the bars coming out in the disassembly position during combustion. One of the pistons performs the useful stroke in normal operation during combustion, this stroke is secured over a defined and restricted length, and the other piston pushes the previous one in order to increase the stroke of the drive carriage, in maintenance mode exclusively.
[0019] Advantageously, the first piston has a stroke length different from that of the second piston. The movement of the bar during normal operation has a length different from that required for disassembly.
[0020] Advantageously, the piston with the longest stroke moves the movable bar between a retracted position and an extended position. The longest piston stroke corresponds to the movement of the movable bar during combustion in normal operation.
[0021] Advantageously, the piston with the shortest stroke moves the movable bar between an extended position and a disassembly position. The shortest stroke cor responding to the dismantling of the bar, it is added to the movement of the mobile bar during combustion in normal operation.
[0022] Advantageously, the pistons have a total stroke length greater than the length of a movable bar. In this way the movable bars come completely out from under the fixed bars and are more easily removable.
[0023] Advantageously, the movable bars are shorter than the fixed bars. They come out more easily from under the fixed bars with a shorter stroke.
[0024] The invention also relates to a method for dismantling a movable bar of a stepped grid with at least one of the preceding characteristics, it is characterized in that it comprises the following successive steps: actuation of the two pistons of the hydraulic cylinder to move the drive carriage to a disassembly position, loosening of the movable bar from below the stepped grid frame, extraction of the movable bar.
[0025] Thanks to the accumulation of the strokes of the two pistons, the movable bars of a drive carriage move to the disassembly position where they are completely free of the fixed bars and can be extracted from above the grid. Once the drive carriage is placed in overstroke, the disassembly of the movable bars is done manually and easily from above the grid. The fixed bars do not fall because they are still held by the beam of the drive carriage.
[0026] The invention also relates to a method for dismantling a fixed bar of a stepped grid with at least one of the preceding characteristics, it is characterized in that the stepped grid comprises fixed bars and that it comprises the following successive steps: actuation of the two pistons of the hydraulic cylinder to move the drive carriage to a disassembly position, loosening of the movable bar from below the stepped grid frame, extraction of the movable bar, installation of a temporary support in place of the movable bar, retraction of one of the two pistons of the hydraulic cylinder to retract the drive carriage, loosening of the fixed bar from below the stepped grid frame, extraction of a fixed bar.
[0027] The process of dismantling a fixed bar is successive to the dismantling of a movable bar. Temporary supports are put in place to hold the fixed bar and the drive carriage is moved back.
[0028] Other advantages may still become apparent to those skilled in the art upon reading the examples below, illustrated by the appended figures, given for illustrative purposes. BRIEF DESCRIPTION OF THE FIGURES
[0029] The figures are presented for information purposes only and in no way limit the invention.
[0030] [Fig. 1] represents a diagram of a combustion furnace for high calorific fuels;
[0031] [Fig.2] is a top view of a rack of the oven of [Fig.l];
[0032] [Fig.3] is a sectional view of the hydraulic cylinder of the stepped grid according to the invention;
[0033] [Fig.4] is a side view of the stepped grid according to the invention;
[0034] [Fig.5] is a sectional view of the steps in the method of dismantling a bar mobile of the stepped grid according to the invention;
[0035] [Fig.6] is a sectional view of a fourth step of the method of dismantling a fixed bar of the stepped grid according to the invention;
[0036] [Fig.7] is a sectional view of a fifth step of the method of dismantling a fixed bar of the stepped grid according to the invention;
[0037] [Fig.8] is a sectional view of a sixth step of the method of dismantling a fixed bar of the stepped grid according to the invention. DETAILED DESCRIPTION
[0038] Unless otherwise specified, the same element appearing in different figures has a single reference.
[0039] Throughout the description, the upper part of figures 5 to 8 will be called "top", "above", "upper", and the lower part of said figures will be called "bottom", "below", "lower".
[0040] [Fig.l] shows a combustion furnace 1 for high calorific fuels which comprises: • a fuel supply system 10 consisting of solid materials with high calorific value 14, • a hearth with walls made of refractory materials 12 and a stepped grate 11, • a boiler 13 • an exit 15 for ashes • a convective part 16.
[0041] The solid materials 14 (fuel) arrive at the top via the feed system 10 to the stepped grate 11 which is inclined so as to allow the fuel to spread in the hearth 12, this inclination is slight, for example between 0° and 20°. The fuel emits smoke which passes through the boiler 13 then into the smoke treatment system (not shown). The rest of the burnt fuel is in the form of ash which is discharged to an outlet 15.
[0042] The stepped grid 11 comprises stepped bars with an alternation of rows 110 of fixed bars 2 and rows 111 of mobile bars 3 offset vertically.
[0043] The fixed rungs of a step are placed side by side on a beam 40 and the movable rungs are placed side by side on a beam 41 and fixed together by a system of screws / nuts or clamping rods.
[0044] The beams 41 of the movable bars 3 are connected to a drive carriage 5, here three beams 4L. The drive carriage 5 is actuated by at least one hydraulic cylinder 6 connected on one side to the drive carriage 5 and on the other to the frame 112 of the stepped grate 11, a frame which integrates the beams of the fixed bars, the rough ash evacuation hoppers and the rolling track of the drive carriage.
[0045] The hydraulic cylinder 6 of the stepped grid 11 according to the invention is illustrated [Fig. 3]. The cylinder 6 comprises two independent chambers 60 and 61 aligned along an axis X, each comprising a piston 600 and 610. Each chamber 60 and 61 is connected to a hydraulic fluid such as oil by two conduits 601 and 602, and 611 and 612 respectively. The chamber 60 and the piston 600 are longer than the chamber 61 and the piston 610.
[0046] The piston 600 of the jack 6 is actuated individually by a control system, to move the movable bars 3 from the retracted position to the extended position by supplying a first part 60a of the chamber 60 via the conduit 602. The piston 610 is actuated individually by the same control system, to move the movable bars 3 from the extended position to the disassembly position by supplying a first part 61a of the chamber 6 via the conduit 611. The term “actuate” means the act of making the piston exit the chamber.
[0047] To retract the movable bars 3 from the extended position to the retracted position, the control system supplies a second part 60b of the chamber 60 via the conduit 601 which causes the piston 600 to return to the chamber 60. To exit the disassembly position, the control system supplies a second part 61b of the chamber 61 via the conduit 612 which causes the piston 610 to return to the chamber 61.
[0048] The longest piston 600 can be connected indifferently to the frame 112 or to the drive carriage 5.
[0049] We can see [Fig.4] the three positions of the movable bars 3, the retracted position R where the movable bars 3 are practically covered by the fixed bars 2, the extended position S where the movable bars 3 come out uncovered while keeping their rear part under the fixed bars 2 in order to maintain continuity of the stepped grid 11 and the disassembly position D where the movable bars 3 come out completely from under the fixed bars 2.
[0050] We will now describe the method of dismantling a movable bar 3 as illustrated [Fig.5].
[0051] The movable bars 3 are moved to the disassembly position D by actuating the two pistons 60 and 61 of the hydraulic cylinder 6, which allows them to be completely released from under the fixed bars 2 and to be able to remove one or more movable bars 3n from above after having been loosened from each other from under the frame 112. The fixed bars 2 are still held by the beam 41 of the drive carriage 5.
[0052] For the disassembly of the fixed bars 2, the first three steps are the same as for the disassembly of the movable bar 3n. A temporary support 50 is placed on the beam 41 of the movable bar 3n which has been removed as can be seen [Fig.6]. The drive carriage 5 is moved back by controlling the withdrawal of the hydraulic piston to completely disengage the fixed bar 2n from the beam 41 of the movable bar 3n which has been removed (see [Fig.7]). The temporary support 50 allows the upper fixed bar 2n-1 to be held. The fixed bar(s) 2n that it is desired to remove are loosened from each other from below the frame. If the fixed bars are water-cooled, the supply pipes 7 must also be separated, depending on their fixing system this is done from below or above. In the example illustrated [Fig.8], these supply pipes are fixed from above using screws 70.
[0053] For reassembly, simply proceed in reverse.
Claims
Claims
1. Stepped grid (11) comprising a frame (112) and movable bars (3) connected to a drive carriage (5) actuated by at least one hydraulic cylinder (6), characterized in that the hydraulic cylinder (6) comprises two independent chambers (60, 61) each having a piston (600, 610) and arranged on either side of the hydraulic cylinder (6), a first piston (600, 610) being connected to the drive carriage and a second piston (610, 600) being connected to the frame (112) of the stepped grid (11) and that each chamber (60, 61) is supplied independently of one another.
2. A stepped grate (11) according to claim 1, characterized in that the first piston (600, 610) has a stroke length different from that of the second piston (600, 610).
3. Stepped grate (11) according to one of the preceding claims, characterized in that the piston (600) with the longest stroke moves the movable bar (3) between a retracted position (R) and an extended position (S).
4. Stepped grate (11) according to one of the preceding claims, characterized in that the piston (610) with the shortest stroke moves the movable bar (3) between an extended position (S) and a disassembly position (D).
5. Stepped grate (11) according to one of the preceding claims, characterized in that the pistons (6) have a total stroke length greater than a length of a movable bar (3).
6. Stepped grid (11) comprising fixed bars (2) according to one of the preceding claims, characterized in that the movable bars (3) are shorter than the fixed bars (2).
7. Method for dismantling a movable bar (3n) from a stepped grid (11) according to one of the preceding claims, characterized in that it comprises the following successive steps: - actuation of the two pistons (600, 610) of the hydraulic cylinder (6) to move the drive carriage (5) to a dismantling position (D), - loosening of the movable bar (3n) from below the frame (112) of the stepped grid (11), - extraction of the movable bar (3n).
8. Method for dismantling a fixed bar (2n) from a stepped grid (11) according to one of claims 1 to 6, characterized in that the stepped grid (11) comprises fixed bars (2) and that it comprises the following successive steps: - actuation of the two pistons (600, 610) of the hydraulic cylinder (6) to move the drive carriage (5) to a disassembly position (D), - loosening of the movable bar (3n) from below the frame (112) of the stepped grid (11), - extraction of the mobile bar (3n), - installation of a temporary support (50) in place of the movable bar (3n), - retraction of one of the two pistons (600, 610) of the hydraulic cylinder (6) to retract the drive carriage (5), - loosening of the fixed bar (2n) from below the frame (112) of the stepped grid, - extraction of a fixed bar (2n).