subject: The Safety Of The Firing Grate [print this page] The object underlying the invention is achieved by a water-cooled fire grate , which consists of a plurality of blocks of grate bars extending over the width of the grate, each block consisting of multiple grate bars, wherein each grate bar has a meander-shaped channel in addition to several cut-in grate slots inside. The grate bars are furthermore connected with each other by screwable connecting pieces such that a grate slot is formed between two grate bars. In the interior of the connecting pieces a connecting passage extends, which connects the meander-shaped channels of two grate bars. The grate bars positioned on the boundaries of the grate have screwable inlet and outlet pieces, through which the liquid coolant water is supplied and discharged.
Because of the cooling of the grate with the liquid coolant water, the temperature at the surface of the grate bar is 90 to 110 C. The result is a reduction of the wear of the grate and the grate has a high thermal load-bearing capacity of 0.9 to 1.1 MW/m 2 grate area. This leads to the fact that the inventive grate can be built smaller by about 30% as compared to the known air-cooled grates with the same thermal efficiency. The meander-shaped design of the channels arranged in the interior of the grate bars, through which flows the coolant, and the connecting, inlet and outlet pieces to be used in accordance with the invention advantageously cooperate such that the supply and discharge of the coolant is only effected from the boundaries of the grate. The individual blocks of grate bars or several blocks of grate bars can thus be provided with the coolant at the boundaries of the grate, so that the operational safety is increased. The connecting pieces ensure that between the individual grate bars, of which a block of grate bars consists, grate slots are formed, which do not change their width during the operation. This high dimensional accuracy of the inventive travelling grateensures both a minor passage of ash through the grate and an optimum supply with combustion air and a substantial burn-out of the fuel on the grate, so that finally a high thermal load is achieved.
In accordance with the invention it is furthermore provided the connecting, inlet and outlet pieces enclose a grate bar carrier and are screwed to the carrier. The meander-shaped channels of the grate bars are connected with each other via the connecting passages of the connecting pieces. The dimensional accuracy of the blocks of grate bars and the operational safety of the firing grate are thus increased.
In accordance with the invention it is particularly advantageous that the individual grate bar blocks can be moved by means of the grate bar carriers, and/or that the firing grate has an angle of inclination of 8 to 11. The movability of the grate bar blocks does not reduce the operational safety of the firing grate designed in accordance with the invention. The inventive firing grate may be designed for instance as an inclined counterflow grate or as an inclined feed grate or as a horizontally arranged feed grate.
In a further aspect of the invention the grate slots have a width of 1 to 1.5 mm. This width of the grate slots ensures that the fuel disposed on the grate does not drop through the slots, and that enough combustion air gets into the fuel layer. In particular the chain grate slots provided between two grate bars do not change their width during the operation, as the connecting pieces fix the individual grate bars such that a grate slot-width of 1 to 1.5 mm is reliably maintained.
In accordance with the invention it is furthermore provided that the connections between the grate bars and the connecting pieces or the inlet and outlet pieces are sealed by a flush cut of the contact surfaces of the workpieces and by graphite seals. Due to the cooperation of the flush cut contact surfaces of the workpieces with the graphite seals and with the inventive screw connections of the individual workpieces an absolutely reliable sealing of the cooling system is achieved, so that the operational safety of the firing grate is also ensured over an extended operation.
In accordance with the invention the grate bars lie on the connecting, inlet and outlet pieces and screwed to the connecting, inlet and outlet pieces by means of vertically extending screws. The large contact area and the screw connection lead to a good fixation of all workpieces and a safe sealing of the cooling system.
In some cases it turned out to be expedient when a horizontal, air-cooled firing grate known per se is provided downstream of the inventive fire grate china . In this way, a high burn-out of the fuel is advantageously achieved, although the thermal load-bearing capacity of the air-cooled firing grate is only 0.5 to 0.8 MW/m 2 grate area. Alternatively, a second inventive, horizontal, water-cooled firing grate can be provided downstream of the inventive firing grate, so that a high fuel burn-out is achieved with a high load-bearing capacity of the grate.
The postcombustion can be improved in accordance with the invention in that at the upstream side of the second air-cooled or water-cooled firing grate nozzles are provided, through which pulsed combustion air is introduced into the combustion space, where the pulsed air may also be preheated.
In accordance with the invention the horizontal, air-cooled firing grate provided subsequent of the inventive firing grate has connecting and end pieces, which have no connecting passages, but are otherwise designed corresponding to the connecting, inlet and outlet pieces.
