Abstract:
A device for wetting a bulk good, in particular for moistening power plant filter ashes, comprises a downpipe. An inlet, through which the bulk good enters the downpipe, is formed at the upper end of the downpipe. An outlet, through which the bulk good is discharged in the wetted state, is formed at the lower end of the downpipe. A water supply to the downpipe is provided. The downpipe has a flexible wall section. The water supply opens into the flexible wall section of the downpipe. Deposits of the bulk good are prevented in that the bulk good does not come in contact with water until the bulk good is in the flexible wall section.

Description:
BACKGROUND 
       [0001]    The invention relates to a device for humidifying a bulk material, in particular for humidifying power plant filter ash. The device includes a downpipe. An inlet, through which the bulk material enters into the downpipe, is realized at the top end of the downpipe. An outlet, through which the bulk material exits in the humidified state, is realized at the bottom end of the downpipe. A water supply is provided to the downpipe, and the downpipe has a flexible wall portion. 
         [0002]    There are bulk materials which tend to form dust in the dry state. Included here, for example, is ash, as is created during the operation of a power plant. If the bulk material has to be disposed of out of the power plant, the surrounding area can become impaired in a considerable manner by the dust that is created. It is known that the formation of dust in the case of said bulk materials can be reduced by means of humidification, see for example DE 41 27 447 and DE 197 42 334. It has been shown, however, that the bulk material, when it is mixed with water, tends to adhere to the inside wall of the downpipe and be deposited there. 
         [0003]    DE 41 27 447 proposes several measures to combat the depositing of the humidified bulk material. Thus, the bulk material is set in rotation before the water is supplied. In addition, a scraper is provided in the downpipe in order to remove deposits again which form in spite of the rotation of the bulk material. Finally, the wall in a bottom portion of the downpipe consists of a flexible material. The flexible material is kept in motion by the bulk material flow such that the bulk material is not able to be fixed there. A plurality of measures such as these is susceptible to errors and requires regular maintenance. 
       SUMMARY 
       [0004]    A device for humidifying bulk materials is provided. The device is simple in design and does not have any bulk material deposited in the downpipe. The supply opens out in the flexible wall portion of the downpipe. 
         [0005]    First of all, some terms are explained. The term flexible wall portion refers to a portion of the downpipe in which the wall of the downpipe comprises a flexible material. The flexible material can be set in elastic motion by the forces which arise during the operation of the device. 
         [0006]    The term water in conjunction with the humidifying of the bulk material is representative of all liquids which reduce the development of dust when they are supplied to the bulk material. Fresh water, waste water and non-filtered water are included. Liquids in which the main constituent is one other than water are also included. Solids, for example suspended matter, can be contained in the water. 
         [0007]    By the water supply opening out in the flexible wall portion of the downpipe, the operation of the humidifying takes place precisely where the wall of the downpipe is set into movement by the flow of bulk material. The bulk material, however, is able to collect to a small extent on the moving wall of the downpipe. 
         [0008]    The risk of deposits is not limited to the region of the downpipe in which the water is supplied. Rather, the bulk material can also be deposited further down in the downpipe where no more water is supplied. In order to prevent said deposits, it can be provided that the flexible wall portion extends from the water supply as far as up to the outlet of the downpipe. The bulk material then covers its entire path after humidification in a portion of the downpipe in which the wall is flexible. 
         [0009]    The water supply can open out in a single opening in the flexible wall portion of the downpipe. The water supply preferably opens out in a plurality of nozzles. The term nozzle refers generally to a mouth through which water can enter into the downpipe. Using a plurality of nozzles, in the case of a suitable arrangement it can be achieved that the water contacts the bulk material flow from several directions and as a result the bulk material is evenly humidified. The nozzles can be arranged on one plane of the downpipe. The nozzles can be located opposite each other in pairs or can be equally distributed over the circumference of the downpipe. Embodiments where the nozzles are arranged at different heights in the downpipe are also included. For example, the nozzles can be distributed on several planes in the wall of the downpipe. The nozzles can be aligned perpendicularly with respect to the wall of the downpipe or can open out into the downpipe at an angle. 
         [0010]    For even humidification of the bulk material, the nozzles can be realized as fan jet nozzles such that the water jet is expanded in one dimension transversely with respect to its direction of movement. The fan jet can be aligned parallel, transversely or inclinedly with respect to the flow of bulk material. The alignment of all the fan jet nozzles can be the same. Different alignments are also possible such that, for example, part of the fan jet nozzles is aligned parallel and another part is aligned transversely with respect to the flow of bulk material. 
         [0011]    The nozzles can be arranged fixed in position or can be rigidly connected together. The freedom of movement of the flexible wall of the down pipe is then limited by the nozzles. Movement of the flexible wall is only possible in the region between the fixedly arranged nozzles. As an alternative to this, it can be provided that the nozzles are connected to the flexible wall portion independently of one another. Movements of the nozzles in relation to one another are then possible such that the flexible wall of the downpipe has a greater freedom of movement. The probability of deposits of bulk material is reduced further by this measure. 
         [0012]    Flexible lines can be provided in order to supply water to the nozzles. The freedom of movement of the nozzles is retained by using flexible lines. The flexible lines can be fed, for example, from a ring-shaped line which extends around the downpipe. 
         [0013]    As few holding points for deposits as possible are to be presented to the bulk material in the interior of the downpipe. The inside wall of the downpipe is preferably smooth for this reason. If a portion in which the wall of the downpipe is rigid connects to the flexible wall portion—which is not absolutely necessary—, the transition between the rigid and the flexible wall portion should be as flush as possible. In an advantageous embodiment, the nozzles by means of which the bulk material is humidified are developed such that they do not project into the interior of the downpipe. 
         [0014]    Apart from the mentioned nozzles by means of which the bulk material flow is humidified, cleaning nozzles can be arranged in the downpipe. Deposits and contaminants which become fixed in spite of the humidification carried out as claimed in the invention can be removed again by means of the cleaning nozzles. The cleaning nozzles are developed such that they project into the interior of the downpipe. The cleaning nozzles are preferably aligned such that the water contacts the inside wall of the downpipe at an acute angle of less than 45°. Contaminants and deposits are lifted off the inside wall of the downpipe as a result and are removed. 
         [0015]    The cleaning nozzles can be realized as sluice nozzles, in which the water is deflected such that it contacts the inside wall of the downpipe at a suitable angle. A deflecting surface can be provided for this purpose in the extension of the nozzle axis, the water jet contacting said deflecting surface and as a result obtaining another direction. 
         [0016]    As elements projecting into the downpipe always form holding points for deposits of the bulk material, the cleaning nozzles are preferably arranged in a portion of the downpipe in which the risk of deposits is low. This is the case wherever the bulk material flow is still dry, that is to say above the water nozzles by means of which the bulk material is humidified. The cleaning nozzles can be arranged in the flexible wall portion of the downpipe. It is also possible for the cleaning nozzles to be arranged in a rigid portion of the downpipe which connects to the flexible portion. 
         [0017]    The material of the flexible wall portion can be a rubber material. The material must not be so flexible that the bulk material flow is impeded by the movement of the material. In order to ensure sufficient stability, reinforcements can be provided for the rubber material. The reinforcement can, for example, be a wire that extends in a spiral-shaped manner through the rubber material. 
         [0018]    It is possible for the bulk material to be stored in a container above the downpipe and to fall out of the container into the downpipe. In an alternative embodiment, the bulk material is supplied to the downpipe in a fluidized state. For this purpose, fluidizing elements can be arranged at the outlet of the container, by means of which fluidizing elements a fluidized gas is supplied to the bulk material. A bulk material supplied in a fluidized state can be humidified in a simpler manner. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention is described below by way of advantageous embodiments with reference to the attached drawings, in which: 
           [0020]      FIG. 1  shows a schematic representation of a device; 
           [0021]      FIGS. 2 and 3  show downpipes in the case of other embodiments; and 
           [0022]      FIGS. 4 to 6  show cutouts of the flexible wall portions in the case of different embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    A device shown in  FIG. 1  includes a hopper  10  which is filled with a bulk material  11 . The bulk material is ash which is created during the operation of a power plant. Fluidizing elements  12  are arranged at the bottom end of the hopper  10 . Air can be directed into the bulk material  11  by the fluidizing elements  12  such that the bulk material  11  is set into a fluidized state. 
         [0024]    The hopper  10  merges by way of its bottom end into a downpipe  14  which is arranged in a perpendicular manner. The outlet of the hopper  10  forms at the same time the inlet  13  of the downpipe  14 . A closure  15  which is represented in the closed state in  FIG. 1  is realized at the transition from the hopper  10  to the downpipe  14 . In the closed state, the closure  15  prevents the bulk material  11  from being able to escape from the hopper  10 . The the closure  15  therefore closes the hopper  10  off downward. If the closure  15  is open, the bulk material  11  can enter into the downpipe  14  in the fluidized state. From the region of the inlet  13 , the bulk material falls downward until it escapes through the outlet  16  out of the downpipe  14 . 
         [0025]    The downpipe  14  is divided into a top portion  33  and a bottom portion  34 . In the top portion  33  the wall of the downpipe  14  comprises steel, that is to say a non-flexible material. A closable opening (not shown), which enables access to the interior of the downpipe  14  for the purposes of inspection and cleaning, is realized in the top portion  33 . In order to prevent deposits of the bulk material, the inside wall of the downpipe  14  is smooth in the top portion  33  and provided with a non-stick coating. 
         [0026]    In the bottom portion, the flexible wall portion  34 , the wall of the downpipe  14  comprises rubber which is reinforced with a spiral-shaped wire insert. The reinforced rubber is a flexible material. At  35  the steel of the top portion  33  and the rubber of the flexible wall portion  34  are connected together in a suitable manner. In an advantageous embodiment, the steel and the rubber material are connected to each other in a flush manner such that the inside wall of the downpipe  14  is smooth in the transition region. As an alternative to this, the rubber material can be connected in a simple manner to the top portion  33  by being placed on the outside and being secured by way of a clamp. 
         [0027]    Eight nozzles  20 , which are only represented schematically in  FIG. 1  as openings in the wall of the downpipe  14 , are arranged in each case on a first plane  17  and a second plane  18  in the flexible wall portion  34  of the downpipe  14 . The nozzles  20  are fan jet nozzles which are aligned onto the center of the downpipe  14  in the radial direction and are inclined downward slightly in relation to the horizontal. The nozzles  20  are equally distributed over the circumference in each case on the planes  17  and  18 . 
         [0028]    An annular pipe  21  which surrounds the downpipe  14  is provided for each of the planes  17 ,  18 . Connecting lines  22  extend in each case from the water nozzles  20  to the associated annular pipe  21 . The connecting lines  22  comprise a flexible material. Therefore, they are not rigid. The annular pipes  21  are supplied with water by a supply line (not shown) which is pressurized. The water can be waste water, in a power plant, for example, the waste water of a flue gas desulphurization system. The water passes via the annular pipes  21  and the flexible connecting lines  22  to the water nozzles  20  and from there enters into the downpipe  14  where it contacts the bulk material flow falling through the downpipe  15 . The water penetrates into the bulk material flow and at the same time mixes with the bulk material flow. The water contacting the bulk material flow from different directions on the planes  17 ,  18  ensures that the bulk material is completely humidified before it exits through the outlet  16  of the downpipe  14 . 
         [0029]    Through the water emerging from the nozzles  20  and the bulk material flow which moves through the downpipe  14 , a force acts on the rubber material of the flexible wall portion  34 . The rubber material is selected such that it is set in motion by said forces. The movement is strong enough to prevent the bulk material being deposited, but not so strong that the movement of the bulk material is impaired. As the nozzles  20  are connected to the annular pipes  21  by means of flexible connecting lines  22 , the nozzles  20  can move together with the flexible wall of the downpipe  14 . The mobility of the flexible wall portion  34  is only restricted by the nozzles  20  in an insignificant manner. 
         [0030]    In the device, the bulk material flow can move through the entire downpipe  14  without any deposits occurring. In the top portion  33 , in which the wall of the downpipe  14  is of steel, the bulk material is still dry and as a result is not deposited. The bulk material first comes into contact with water in the flexible wall portion  34 , there is no depositing here on account of the movement of the wall. 
         [0031]    In  FIG. 2 , only the nozzles  20  of the bottom plane  18  are used for humidifying the bulk material. So much water exits the nozzles  20  of the plane  18  that the bulk material is completely and evenly humidified. The nozzles of the top plane  17  are realized as cleaning nozzles  36  by way of which deposits, which have formed in spite of the movement in the flexible wall portion  34 , are able to be removed again. The cleaning nozzles  36  project into the interior of the downpipe  14  and are realized as so-called sluice nozzles, where a deflecting surface is arranged in the extension of the nozzle axis. The water jet contacts the deflecting surface and is deflected downward in the form of a fan jet. 
         [0032]    If deposits have formed in the flexible wall portion  34 , the bulk material flow and the water supply to the nozzles  20  are interrupted. The cleaning nozzles  36  are then set in operation in order to remove the deposits again. The water jet emerging from the cleaning jets  36  contacts the wall of the downpipe  14  at an angle of approximately 30° and lifts the deposits off. Once the deposits have been removed, the device can be put back into operation properly again and be used for humidifying the bulk material. 
         [0033]    In the embodiment in  FIG. 3 , once again only the nozzles  20  of the bottom plane  18  are used for humidifying the bulk material, whilst the nozzles of the top plane  17  are realized as cleaning nozzles  36 . Contrary to the embodiment in  FIG. 2 , both planes  17 ,  18  are not arranged in the flexible wall portion  34 , just the nozzles of the bottom plane  18 . The cleaning nozzles  36  are arranged in the top portion  33  of the downpipe  14  in which the wall consists of a rigid material. As movement of the cleaning nozzles  36  is not desired, the connecting lines  22  between the cleaning nozzles  36  and the annular pipe  21  can also be rigid. 
         [0034]    In the case of many bulk materials, it is sufficient for a complete and even humidifying of the bulk material when a plurality of nozzles  20  is arranged on one plane  18 . Neither additional nozzles on another plane nor cleaning nozzles are urgently necessary to the invention. 
         [0035]      FIGS. 4 to 6  show cutouts from the flexible wall portion  34  in the case of different embodiments. In  FIG. 4  a hose-shaped attachment  37  is realized directly in the rubber material of the flexile wall portion  34 . A nozzle  20  is inserted into the hose-shaped attachment  37  and is fixed in the suitable position using a hose clip (not shown). 
         [0036]    In  FIG. 5  just one bore is provided in the rubber material of the flexible wall portion  34  for the reception of the nozzle  20 . The nozzle  20 , the outside surface of which is provided with a thread, is inserted into the bore and fixed in the correct position using two nuts  38 . The nozzle  20  projects into the downpipe  14  and is aligned at a right angle with respect to the wall of the downpipe  14 . 
         [0037]    In  FIG. 6 , the nozzle  20  is also fixed using two nuts  38 . The water nozzle  20  obtains an inclined alignment in relation to the wall of the downpipe  14  by means of wedge-shaped intermediate parts  39 . The contour of the intermediate parts  39  is adapted to the flexible wall portion  34 .