Abstract:
The residual material in a filter-dryer ( 1 ) is removed from the screen ( 15 ) by careful scraping with a lasso like belt ( 20 ). The scraped material will be removed through a side opening ( 16 ). To gain this remaining material adds to the yield of the process by reducing loss of product, and does not endanger personnel unnecessarily and therefore save process costs.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to the removal of residual product from a vessel and more specifically to the removal of residual product from a filter-dryer unit with a side opening for emptying, employing a so called “lasso-technique”. 
     2. Background of the Invention Art 
     Filter-Dryers are used in the production for filtration and drying at the first place. But also extractions, washing and other intermediate processes are processed in these apparatus. It often is the aim to process several steps in the same unit. If it is possible to proceed without discharging the product and thus without opening the containment, losses of valuable substances and danger for poisoning personnel or damaging the product can be minimized. 
     The variations of Materials to be treated that way go from simple chemical products which have to be dried to highly sensitive and even toxic products of the pharmaceutical Industry. Especially for the latter it is desirable not to expose the products to air and endanger personnel by handling it. To treat several production steps in one and the same unit therefore is highly desirable. 
     The basic material is typically fed to the filter-dryer unit as a slurry of a predefined mixture of crystals suspended in liquid. A batch of such a slurry is commonly loaded into the filter-dryer. This filter-dryer unit usually is in the form of a sealed, cylindrically shaped vessel having a filter in its base to allow the liquid to be drained from the vessel through the filter plate. A side or center discharge. opening is provided to allow the resulting dry product, often a powder, to be removed from the vessel to a receiving container or the like. Usually a mechanical agitator rotates in the vessel at a relatively slow rate. This mechanical agitator will be moved up and down during its rotation in order to generate new surfaces on the slurry and powder especially during the drying process. With this agitator one avoids the generation of wet clumps as a most homogeneous mass is required in the slurry-phase as well as in the powder-phase. This mechanical agitator also serves to remove the dried or treated product mechanically out of the vessel discharge opening. 
     In this apparatus the liquid particles will be separated from the solids by a first step with a filtration process. The bottom plate of such a apparatus is a filter plate and a following drying process under special temperature and vacuum conditions. For this processes the target always is to produce crystals and solids as product with the highest possible yield, e.g. the lowest possible moisture contained. 
     Treating cosmetics, pharmaceutical and other valuable goods the problem faced is always that a residue of the finished product tends to remain in various parts of the vessel. U.S. Pat. No. 5,564,350 introduces a so called “gasknife” for the removal of these residues by means of pressed air or pressed inert gases. For many products this device works very good. It might give some problems if the fine fluffy powder does not create e.g. explosion danger or the wet powder does stick too hard to the filter plate on the bottom of the apparatus. 
     The main part and in many cases the last remaining volume of residual material, called the heel, is left on the bottom plate of the vessel and is not readily removable for discharge. This bottom plate of the vessel is provided with relatively fragile and expensive filter screens which allow the liquid to pass from the vessel while preventing the loss of solids by holding it back. The mechanical agitator is a relatively coarse device which may be on the order of up to 4 meters in diameter. To ensure that the filter-screens are not damaged by the agitator, a minimal clearance is required between the agitator and the screens. This clearance may be on the order of up to several millimeters for big filter-dryers. The residue in that space and elsewhere in the vessel is typically washed away at the end of the batch processing and is therefore a loss which reduces the yield of the production. 
     In the processing of pharmaceutical substances different batches may not be mixed together and therefore the residue is essentially lost if it has to be washed out. The lost residue often makes up to 15% of the batch. For expensive material such as highly concentrated pharmaceuticals substances this is great loss. Very often the heel will be scratched out by hand which might be dangerous for the personnel due to poisonous or toxic volatiles or substances. 
     Due to this fact the use of a filter-dryer for several process steps might not be applicable even if the process itself offers very advantageous possibilities for the product with such procedures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       An embodiment of the invention is described below with reference to drawing in which: 
         FIG. 1  shows a cross section of the filter-dryer 
         FIG. 2  shows a detail of the cross section of the filter-dryer. 
         FIG. 3  shows a cross section view from the top on the filter plate. 
         FIG. 4  shows an automatic side opening device. 
         FIG. 5  shows a cross section view from the top on the filter plate. 
         FIG. 6  shows a cross section view from the top on the filter plate. 
         FIG. 7  shows a principal view of a hand operated device. 
         FIG. 8  shows a principal view of an hand operated device with a human protection cab for the operator. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the proposed and presented arrangement is merely illustrative of the application of the principles of the invention and that other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention. 
       FIG. 1  is a cross sectional side view of the vessel  1  which most typically is used as a filter dryer. The vessel  1 , preferably of cylindrical shape with a domed top  11 , a vertical side wall  12  extending around the circumference of the cylindrical vessel  1  and a domed bottom  13 . A separation plate  15  which will at least partly contains a filter plate which allows for the passage of liquid from the vessel while filtering out solid particles of the material to be recovered. These solid particles form during the filtration process a compact filter cake  2  on the separation plate  15 . The liquid filtrate  4  is collected at the bottom  13  an drained over the discharge tube  17 . A side discharge opening  16  is provided for the removal of the filter cake  2  in form of solid product  3  as powder or clumps. Another type of this kind of filter dryers called “Rosenmund-Filter” (see EP 0 138 188) provide additionally a discharge opening for the solid product in the center of the bottom but this variation of a filter-dryer need not be described and is not shown in the figures. 
     In order to increase efficiency of such an equipment a mechanical agitator  14  is provided turning around the shaft  144  in the center of the cylindrical vessel  1 . Such rotating mechanical agitator  14  has one or more arms  141 . This agitator  14  is used to press the filter cake  2  in order to accelerate the filtration process. After finishing the filtration process and especially during the drying process this agitator  14  very often is used to mix and shift the solid product  3  in order to loosen the compact filter cake  2  preferably to powder or at least clumps. 
     Along the circumference of the vessel  1  on top of the filter plate  15  a belt  20  can be positioned either from the beginning or at the last step of the emptying process. This belt  20  called “lasso” has at least the length identical to the circumference of the inner diameter of the containment. It is of a thickness of 3-5 mm and a width of 50-100 mm and it&#39;s position is between the side wall  12 , the tip of the agitator arm  141  and it is in contact with the separation plate  15  ( FIG. 2 ). Its ends  201 ′ and  201 ″ reach through the side opening  16  outside the Vessel  1 . 
     One end  201 ′ of the belt  20  usually will connected with one side of the side opening  16  e.g. at fixation  23  ( FIG. 3 ), whereas the other end  201 ″ will e.g. be connected to a special wind up device  22  with which this end  201 ″ of the belt  20  can be pulled in to a box  21  outside the side opening  16  and the vessel  1  ( FIG. 3 ). 
     During the process the containment of vessel  1  naturally must be closed. In order to offer a smooth surface over the whole circumference of the side wall  12  the lid  18  will have the shape to continue the line of side wall  12  ( FIG. 7 ). This lid  18  can be securely closed by a simple bolt system used for such apparatus or it can be equipped with a sophisticated hydraulically operated opening device  19  as shown in  FIG. 4 . For the method according to the inventive idea with the belt  20  this does not change in the effective cleaning and removing process of the heel  100 . This process works as it is shown in  FIG. 3  to  FIG. 6 . The loop of the belt  20  will be narrowed by pulling one or both ends  201 ′,  201 ″ outside the vessel  1  through the side opening  16 . During this the rather stiff belt  20  will scratch the heel  100  from the surface of the separation plate  15  which works at least partly as the filtration plate. The heel  100  will be moved towards the side opening  16  and drops down through discharge opening  25  ( FIG. 1  and  FIG. 3 ) where it can be collected safely. 
     The inventive idea is to use a belt  20  in order to remove all the rest of the solid particles  3  of the filter cake  2  from the separation plate  15 . This invention will avoid expensive losses of valuable products in particular production of active pharmaceutical substances. There are two ways and methods for the application of this inventive device to remove the heel  100  providing a belt  20 : An automatic or semi automatic method for which the equipment is shown in  FIG. 2  to  FIG. 4  and a manually operated way shown in  FIG. 7  and  FIG. 8 . For the basic idea of this invention this does not make any difference. In case a mechanical device is used the human protection against toxic substances can be offered rather well. For the production of active pharmaceutical substances very often only very small equipment is used as the bulk of one production are small but these substances are very expensive. The manual process in these cases has the preference. In the manual process the operator must be protected from toxic substances. In such cases this inventive method can be executed in by using a human protection box  26  to safeguard the operator as shown in  FIG. 8 .