Description

The present invention relates to an incineration plant for solid material such as waste or biomass, the incineration plant having a combustion material inlet through which the solid material is to be introduced, a combustion chamber into which the solid material is introduced and in which the solid material is combusted, whereby combustion gases are produced, a combustion grate with which the solid material and combusted solid material can be conveyed through the combustion chamber, a primary air supply below the top of the combustion grate, at least one nozzle arranged above the combustion grate with which a gaseous medium such as secondary air, tertiary air and/or an oxygen poor carrier gas or similar can be provided, the nozzle having a nozzle cross section.

The incineration plant usually comprises a combustion grate arranged within a lower section of the combustion chamber with which the solid material and combusted solid material can be conveyed through the combustion chamber from the combustion material inlet to a slag container. The solid material and combusted solid material on top of the combustion grate is also called solid material bed. Primary air is usually supplied from below the combustion grate to the solid material bed arranged on the combustion grate, so that the solid material arranged on the combustion grate is combusted with the primary air. The combustion grate is preferably embodied as reciprocating grate, but it is also possible that the combustion grate is embodied in a different way, for example as vibrating grate or roller grate.

Additionally, nozzles are provided above the combustion grate with which secondary air, tertiary air for afterburning, an oxygen poor carrier gas (such as recirculating gas) or any other suitable gas can be provided to the combustion gas.

At least one empty pass may be arranged downstream of the combustion chamber extending vertically or horizontally, wherein the flue gases flow from the combustion chamber through the at least one empty pass to a heat recovery steam generator. In particular, two, three or more parallel empty passes may be embodied.

The heat recovery steam generator downstream of the empty pass may be arranged (in sections) vertically and/or horizontally, wherein also an oblique orientation is possible.

The walls of the combustion chamber, the empty pass(es) and the heat generator are usually equipped with heat exchangers (i.e. tubes), wherein the heat exchange medium of the heat exchangers is in particular provided to one common boiler drum.

A flue gas purification device downstream of the heat recovery steam generator may comprise elements for dedusting, scrubbing and/or desulfurization (such as SCR or SNCR) of the flue gas. A chimney may by arranged downstream of the flue gas purification device.

Usually there are multiple nozzles arranged above the combustion grate for providing secondary air, tertiary air and/or an oxygen poor carrier gas or similar, wherein the nozzles of a specific gaseous medium are connected with its inlets to a common supply. The nozzles are also secured to a wall of the combustion chamber. The (flow) cross section of the nozzle predominantly defines the parameters of the resulting free jet of gaseous medium mixing with the the combustion gas. The cross section does not only define the shape of the free jet but predominantly its initial velocity and therefore its penetration depth into the combustion gas. With the penetration depth the mixing of the gaseous medium with the combustion gas and also the mixing of the combustion gas itself is influenced.

DE 196 48 639 A1 discloses in incineration plant for waste with the features of the preamble of claim 1 , wherein the cross section of the nozzle and/or the pressure applied to the nozzle is set in such a way, that a double vortex is impinged on the combustion gases. EP 1 612 484 A1 discloses a boiler for combusting coal.

When waste mass flow has to be adjusted due to changes in caloric value of the provided solid material, the amount of supplied combustion air, especially secondary air needs to be adapted. Therefore, it is known to disconnect single nozzles of a plurality of nozzles from a secondary air supply, while each of the other nozzles are operated with the previous conditions (in particular with the same initial velocity of the free jet of gaseous medium). Therefore, it is necessary to provide a high number of nozzles, i.e. arranged in planes above each other, to adapt the operation of the nozzle to the changing caloric value of the solid material to be combusted.

In view of this, it is an object of the present invention to provide an incineration plant, which can be more easily adapted to solid material with changing caloric value without the need to provide high numbers of nozzles which can be shut off independently of each other depending on the caloric value.

This object is achieved by an incineration plant with the features of the independent claim. Preferred embodiments of the incineration plant are described in the sub claims and in the whole description, wherein single features of the preferred embodiments can be combined with each other in a technically meaningful manner.

The object is achieved in particular in that the at least one nozzle comprises at least one moveable adjusting part, wherein the nozzle cross section of the nozzle is adjustable by the adjusting part.

The basic idea behind the invention is to alter the shape and/or preferably the area of the nozzle cross section so that also the respective parameters of the resulting free jet of gaseous medium mixing with the combustion gas can be altered. For example, if the amount of secondary air (and therefore its flow rate) needs to be decreased, the cross section area of the nozzle can be decreased, so that the initial velocity of the gaseous medium leaving the nozzle and therefore the penetration depth of the resulting free jet of gaseous medium can be kept constant. Therefore, there is no need to disconnect single nozzles from the secondary air supply, when the demand of secondary air decreases, which might lead to problems, when the respective nozzle is connected to the supply again.

Principally it is sufficient, if there is only one nozzle above the combustion grate, which has at least (or exactly) one moveable adjusting part. Preferably, there are at least (or exactly) two, more preferably at least four or most preferably at least eight nozzles above the combustion grate, which each have at least one moveable adjusting part. In a further embodiment, all nozzle above the combustion grate for a specific gaseous medium (secondary air, tertiary air, recirculating gases, mixing gas or similar) are having at least one moveable adjusting part.

The respective nozzle cross section is in particular in that cross section plane of the nozzle, at which the flow cross section of the nozzle is the smallest. This cross section plane may be at the outlet plane of the nozzle but may also be in front of the outlet plane in the flow direction of the gaseous medium. The nozzle cross section is at least partly formed/delimited by a section of the moveable adjusting part. The respective section of the adjusting part may be actuated mechanically, hydraulically, pneumatically or in any other way in order to alter the nozzle cross section. Accordingly, it is suggested that in a first state the nozzle cross section has a first cross section area and a first cross section shape, wherein in a second state the nozzle has a second cross section area and a second cross section shape, wherein the second cross section area differs from the first cross section area and/or the second cross section shape differs from the first cross section shape. The nozzle can be brought from the first state to the second state by moving (i.e. linearly displacing, rotatably pivoting, rotatably turning, expanding) the at least one adjusting part. Preferably, the nozzle cross section is at least partly formed by an edge of a preferably plate shaped adjusting part, which can be displaced linearly and/or rotatable in order to alter the nozzle cross section.

When the at least one adjusting part is actuated, the shape of the nozzle cross section may be altered. For example, the cross section may be altered from a rectangular shape to a slit shape, thereby changing the ratio of the sides of the rectangle.

Preferably, when the at least one adjusting part is actuated/moved, at least the cross section area is altered. In this case, additionally the shape of the nozzle cross section may be altered, but in a preferred embodiment the shape (i.e. circular, elliptic, rectangular) is more or less kept the same, when the cross section area is altered.

While it is principally possible that the moveable adjusting parts can be actuated manually, it is preferred that the at least one moveable adjusting part is connected to a (i.e. electromechanically, pneumatically, hydraulically actuated) nozzle drive. There might be one nozzle drive for each nozzle or one nozzle drive for all nozzles having at least one moveable adjusting part.

A gear may be embodied between the drive and the moveable adjusting parts. While it is principally sufficient that only exactly one moveable adjusting part is embodied, which might form one side delimiting the nozzle cross section, it is preferred that the nozzle comprises multiple (at least two, preferably at least four or even at least eight) moveable adjusting parts. In this regard it is preferred, that the multiple adjusting parts are moveable synchronously. Accordingly, a respective drive may be connected i.e. via a gear to the adjusting parts, so that all adjusting parts of one nozzle are moved at the same time.

In one embodiment the at least one, preferably plate shaped adjusting part is mounted pivotable, so that preferably its free end can be pivoted inwards and outwards to the stream of the medium, which flows through the nozzle. In particular, the free end of the adjusting part can be pivoted towards and away from a longitudinal (center) axis of the nozzle, the longitudinal center axis being defined by the main flow direction of the gaseous medium within the nozzle. Mounting an adjusting part pivotable about a pivot axis can be easily realized, wherein a respective drive and/or gear may be embodied to move the adjusting part around the pivot axis.

In one embodiment, the pivot axis of the at least one adjusting part is extending transversely to the longitudinal axis of the respective nozzle. This way an edge of the adjusting part may be pivoted inwards and outwards of the stream of the gaseous medium, whereby the gaseous medium flows along the inner side of the respective adjusting part.

Alternatively, the pivot axis of the at least one adjusting part may extend parallel to the longitudinal axis of the nozzle. This way the preferably plate like adjusting part would extend with its plane orthogonal to the main flow direction of the gaseous medium within the nozzle. If pivot axes of the multiple adjusting parts extend parallel to the longitudinal axis of the nozzle a kind of iris blade is formed. For actuating these multiple adjusting parts synchronously one actuating ring might be connected to all adjusting parts. It is also suggested that the incineration plant may comprise a control unit, which control unit is connected to the nozzle(s) and in particular to a drive(s) for the nozzle(s), wherein the control unit is embodied such, that depending on the volume/amount of gaseous medium provided through the respective nozzle, the nozzle cross section is set such that the penetration depths of the gaseous medium into the combustion gases is independent of the volume/amount of gaseous medium. Accordingly, if the volume of the gaseous medium is reduced, the nozzle cross section area is reduced. On the other hand, if the volume of gaseous medium is increased, also the nozzle cross section area of the respective nozzle is increased.

The invention and the technical background will now be explained with regard to the figures, which show exemplary embodiments of the invention. The figures show schematically

Figure 1 : a side view of a part of an incineration plant, Figure 2: a nozzle of the incineration plant in a first state, Figure 3 : the nozzle of Fig. 2 in a second state, Figure 4: a further embodiment of a nozzle of the incineration plant in a first state,

Figure 5: the nozzle of Fig. 4 plant in a second state, Figure 6: an even further embodiment of a nozzle in longitudinal cross sectional view indicating a first and a second state and

Figure 7: a front view on the cross section of the nozzle of Fig. 6 in the first and the second state. The incineration plant comprises a combustion chamber 2 with a combustion material inlet 1 , through which solid combustion material such as waste can be introduced in the combustion chamber 2. At the bottom of the combustion chamber 2 a combustion grate 3 is embodied, with which the solid material and combusted material (i.e. ashes) as solid material bed can be transported towards a slag outlet 4.

Primary air for the combustion of the solid material is provided from below the combustion grate 3. The combustion gases produced in the combustion chamber 2 are supplied into vertically extending empty passes 5. Downstream of the empty passes 5 a horizontally extending heat recovery steam generator 6 is arranged.

In the heat recovery steam generator 6 a superheater heat exchanger 7, an evaporator heat exchanger 8 and an economizer heat exchanger 9 are arranged, which are all connected to one common boiler drum 10.

In figures 2 to 5 two embodiments of nozzles 11 for providing a gaseous medium, such as secondary air, tertiary air and/or an oxygen pure carrier gas (i.e. recirculating gas) into the combustion chamber 2 above the combustion grate 3 are depicted in a front view from inside of the combustion chamber 2.

Each of the nozzles 11 comprises a plurality of plate like adjusting parts 13, which commonly define a nozzle cross section 12, which can be flown through by a gaseous medium, which enters the combustion chamber 2 through the nozzle 11. The adjusting parts 13 are connected commonly to a nozzle drive 15, which may comprise a gear 16.

The adjusting parts 13 of the embodiment depicted in figures 2 and 3 are mounted moveable to pivot around respective pivot axes 14, which extend parallel to a longitudinal axis 17 of the nozzle 11. Accordingly, the adjusting parts 13 of the embodiment of figures 2 and 3 embody a kind of iris blade. As can be seen from a comparison of the first state depicted in figure 2 and the second state depicted in figure 3 the nozzle cross section 12 delimited by the adjusting parts 13 can be altered by commonly pivoting the adjusting parts 13 around their respective pivot axis 14.

The adjusting parts 13 of the embodiment of the nozzle 11 depicted in figures 4 and 5 are shaped trapezoidal, wherein each adjusting part 13 is pivotable around a pivot axis 14, which extends transversely to the longitudinal axis 17 of the nozzle 11. As can be seen by a comparison of figures 4 and 5, by pivoting the adjusting parts 13 around their respective pivot axis 14 the nozzle cross section 12 can be altered.

The nozzle depicted in figures 6 and 7 comprises exactly two plate like adjusting parts 13, which are pivotable around respective pivot axes 14, which extend transversely to the longitudinal axis 17 of the nozzle 11. In the first state (indicated by the through lines in fig. 7) the cross section of the nozzle 11 is square like. The adjusting parts 13 can be pivoted around their pivot axis 14 towards the longitudinal axis 17. In the second state (indicated by the dashed line) the plate like adjusting parts 13 delimit a rectangular cross section 12 (indicated by the dashed lines in fig. 7) at the bottom and top. As can be seen in figure 7 the cross section area 12 in the second state is only one third of the cross section area in the first state.

In use, when the caloric value of the solid material varies and therefore the demand for secondary air provided through the nozzles 11 above the combustion grate 3 needs to be adapted, the nozzle cross section 12 can be altered in such a way, that the initial speed of the secondary air leaving the nozzle 11 is adjusted in such a manner to maintain a constant penetration of the initialized free jet, although the flow rate due to the changed secondary air demand has changed. Reference List material inlet combustion chamber combustion grate slag outlet empty pass heat recovery steam generator superheater heat exchanger evaporator heat exchanger economizer heat exchanger boiler drum nozzle nozzle cross section adjusting part pivot axis nozzle drive gear longitudinal axis