Abstract:
An apparatus and method for treatment of medical waste materials, namely a reciprocating autoclave with internal cutters (RAIC), capable of simultaneous crushing and sterilizing of the waste within a waste-treating vessel under a desired temperature and pressure by passing the waste back and forth through the cutters at free falling of the waste materials during the reciprocating of the vessel. It enhances heat penetration onto the small pieces of the fully fractured waste for highly efficient sterilization.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention is concerning an apparatus and method for treatment of medical waste materials, and in particular, to a reciprocating autoclave with internal cutters (RAIC), capable of simultaneously crushing and sterilizing of the waste materials to avoid secondary contamination, characterized in that the entire treatment can be completed at reduced time, comparing with conventional autoclaving methods. The invention is particularly designed to eliminate aerosol pollution during the pre-vacuum operation by employing a separate gas buffering and cooling vessel for pressure regulation. The medical waste can be satisfactorily transformed (decoded) into regular wastes for final treatment and disposal.  
         [0003]     2. Description of the Prior Art  
         [0004]     Comparing with regular solid waste treatment, the treatment of medical wastes has been very costly and laborious, primarily due to the pathogenic hazards and public perception associated with the waste. The waste must be satisfactorily processed to comply with many strict regulations imposed for pollution control as well as for public perception. Accordingly, the treatment of medical wastes requires consideration of the following requirements:  
         [0005]     (1) The combustible medical waste is segregated and stored in red bag and non-combustible in yellow bag for easy identification and the followed-up treatment (color management).  
         [0006]     (2) The wastes should be completely sterilized to destroy pathogens.  
         [0007]     (3) A strain of thermophilic bacteria, such as  Bacillus stearothermophilus  spores, is normally used as the indicating organism. The concentrations of the spore before and after treatment (C 1  and C 2 ) are analyzed and a sterilization efficiency is computed as: 
 
Log (kill)=Log( C 1 /C 2) 
 
         [0008]     in which, C 1  and C 2  are expressed as colony forming unit per milliliter of test suspension (cfu/mL). Most countries require a value of Log (kill) not exceeding 5 for an acceptable degree of pathogen destruction. This is also called a “five-of-nine” treatment or a treatment efficiency of 99.999%.  
         [0009]     (4) The waste should not be recognized by visual inspection from appearance as the medical waste after satisfactory treatment (unrecognizability), such as for the body tissue, syringe, needle, glass bottle, and tubing, etc.  
         [0010]     (5) It must be well controlled during treatment of the wastes to avoid the possible pollution, such as odor, air, and wastewater. Otherwise, effective pollution control devices must be equipped.  
         [0011]     To our best knowledge, none of the existing technologies can completely achieve all the requirements stated above. The technology cited in U.S. Pat. No. 5,119,994 “Method and Apparatus for the Treatment of Medical Waste Materials” was evaluated against these requirements. The cited apparatus is basically an airtight vessel into which wastes are charged. Air is withdrawn out to a certain degree of vacuum and hot steam is injected into the vessel to a certain pressure and temperature for sterilization. A helically configured member and lifting paddles are installed along the interior perimeter of the vessel to assist on mixing of the waste during the treatment. After completion, the waste is discharged out of the vessel for crushing into small pieces by a cutting device installed outside the vessel (post crushing). The broken materials are then treated or disposed by landfill or incineration as for the regular domestic wastes. However the cited technique is bearing with the following shortages:  
         [0012]     1. The cited method requires the separation of metals and rubbers from the waste before treatment to prevent the post-shredder from malfunction.  
         [0013]     2. The cited method uses activated carbon to adsorb bioaerosols emitted from the vessel for pre-vacuum operation. The contaminated activated carbon requires further treatment and disposal.  
         [0014]     3. The vessel is installed along the interior perimeter with a helically configured member and attached lifting paddles. Although having advantageous mixing of waste materials, the helical member provides little crushing, which is critical to complete steam penetration to the waste materials for efficient sterilization.  
         [0015]     4. The period of time required for the cited technology should be as long as for the conventional methods (normally  80  minutes) for complete sterilization.  
         [0016]     5. After sterilization, the cited method does not offer a mean to cool off the waste. If not waiting for sufficient time before opening the vessel, steamy vapor will be emitted out of the vessel and cause possible damage or interference to the operators.  
         [0017]     6. The waste being treated in the vessel requires a separate crushing to make it unrecognizable.  
         [0018]     7. The post-shredding device requires more installation space and laborious handling work.  
         [0019]     In light of the numerous shortcomings stated above, a technology is invented by incorporating a multiple-shaft cutter device within a waste-treating vessel to achieve better steam penetration for sterilization of the medical wastes. In conjunction with the waste-treating vessel, a separate gas buffering and cooling vessel is facilitated for the purpose of complete sterilization of the contaminated air from the pre-vacuum operation. A novel operating procedure is also proposed to take the advantage of this novel apparatus to avoid laborious sorting and possible secondary pollution during the treatment of the medical wastes.  
       SUMMARY OF THE INVENTION  
       [0020]     This invention is to provide a multiple-shaft crushing device installed inside a reciprocating vessel for the treatment of medical wastes. This new design will allow for the entire bag of wastes to be fed into the vessel without unnecessary sorting (intact feeding), so that possible infection from personal contact to the wastes can be avoided.  
         [0021]     The main consideration of this invention is to facilitate an internal crushing device for simultaneous sterilization and crushing of the waste. The steam penetration to the wastes can be significantly improved for efficient sterilization under a desired pressure and temperature. The volume reduction of the wastes can also be efficiently improved.  
         [0022]     Another, this invention is to facilitate a novel operating procedure accompanying with the new device, so that the wastes can be processed with proper sequences of treatment cycles to avoid unnecessary secondary pollution.  
         [0023]     This invention first facilitates a waste-treating vessel having a volume adequate for the design capacity. The vessel is divided into a feed chamber, an output chamber and an inventory chamber. While allowing for a batch feed of the design capacity, the feed chamber must be sufficiently large to maintain a filling ratio less than 70˜80% of the total volume of the vessel. The volume of the storage chamber must be adequate for holding the waste materials during crushing, especially the initial stage of the treatment. The fractured waste is moving back and forth across the cutter device between the feed chamber and the storage chamber at free falling of the wastes by reciprocating the entire vessel.  
         [0024]     Instead of using a conventional air pollution control device, such as the activated carbon, this invention facilitates a separate gas buffering and cooling vessel, preferably installed as a jacket enveloping the waste-treating vessel for the convenience of piping arrangement. The air in the gas buffering and cooling vessel is first withdrawn to the atmosphere until a preset degree of vacuum is achieved. The waste-treating vessel is then loaded with the medical wastes. The air in the waste-treating vessel is then withdrawn from the loaded vessel to the pre-vacuum gas buffering and cooling vessel until a preset degree of vacuum in the waste-treating vessel is achieved. This is important to prevent the waste-treating vessel from cold spot when the steam is introduced into the vessel for sterilization.  
         [0025]     The valve between the gas buffering and cooling vessel and the waste-treating vessel is then closed and the steam is injected into the waste-treating vessel until a preset pressure is reached. The cutter device and the driving system are turned on to begin the crushing of the waste materials under a preset temperature and pressure for sterilization. After a period of time, the valve between the gas buffering and cooling vessel and the waste-treating vessel is turned on to allow for circulation of the hot steam between the two vessels, so that the contaminated air originally stored in the gas buffering and cooling vessel is sterilized.  
         [0026]     The cutter and transmission system comprises at least 2 sets of multiple-shaft cutter devices, each being configured on a plate base, one responsible for the shredding of wastes into larger pieces and another for grinding into smaller pieces. Each set of cutters is installed on a plate base. The two sets of cutter bases are positioned to each other at a vertical angle with respect to orientation of the cutter shafts to accomplish a highly efficient crushing of the wastes. The simultaneous crushing and sterilization is important for efficient steam penetration onto all the fractured pieces of the waste materials. The entire operation can be accomplished in a much shorter period of time (30 minutes) with a higher volume reduction (15˜20%), comparing with other conventional methods.  
         [0027]     After completing the treatment, the cutter and transmission system are tuned off. The valve of steam supply is turned off and the heat exchange system installed in the gas buffering and cooling vessel is turned on to cool off the steam and lower down the pressure in the waste-treating vessel. The waste-treating vessel is then rotated to a position and the inlet closure member is opened to discharge the fully processed waste materials. The waste is now ready for further treatment or disposal as for the regular domestic waste (refuse). 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     The drawings disclose the illustrative embodiments of the present invention which serves to exemplify the various advantages and objects hereof, and are as follows:  
         [0029]      FIG. 1  is a side elevation view of the novel apparatus, used for simultaneous sterilization and crushing of medical waste, showing the waste-treating vessel and the reciprocating wheel, such vessel containing an internal cutter and transmission system and an external buffering jacket, also showing the cutter and transmission system;  
         [0030]      FIG. 1   a  is a cross sectional view taken along line in  FIG. 1 , showing two sets of cutter and transmission systems positioned at a 90-degree angle to the orientation to the shafts of the cutter base;  
         [0031]      FIG. 2  is a side view of the novel apparatus, showing the waste-treating vessel  1 , the buffering jacket and, all the related piping system  4  for pressure regulation, this view revealing the heat exchange system with the heat exchange pipeline configured inside the buffering jacket;  
         [0032]      FIG. 2   a  is a cross sectional view taken along line  2   a  in  FIG. 2 ;  
         [0033]      FIG. 3  is a cross sectional view illustrating two sets of the cutter and transmission systems  2 ;  
         [0034]      FIG. 3   a  is a top view of one set of the cutter and transmission system  2   a,  illustrating the cutter base, cutter, and cutter shaft;  
         [0035]      FIG. 3   b  is a top view of another set of the cutter and transmission system, illustrating the cutter base, cutter, and cutter shaft;  
         [0036]      FIG. 4  is a side view of the supporting base  75  for the novel apparatus, showing the driving motor and driving gear;  
         [0037]      FIG. 4   a  is a side view of  FIG. 4 , showing the driving motor and driving gear;  
         [0038]      FIG. 5  is a side view of the reciprocating wheel;  
         [0039]      FIG. 5   a  is a side view of  FIG. 5 , illustrating the reciprocating wheel;  
         [0040]      FIG. 5   b  is another side view of  FIG. 5 , illustrating the enlarged wheel chain/gear; and  
         [0041]      FIG. 6  is a flow chart of the operation procedure of this invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0042]     As shown in  FIG. 1  to  2   a,  this invention facilitates a novel internal multiple-shaft crushing apparatus for the treatment of medical wastes. The major parts include: one set of waste-treating vessel  1 , two sets of cutter devices  2 , one set of gas buffering and cooling vessel  3 , one set of vacuum system  4 , one set of steam supply system  5 , one set of heat exchange system  6 , and one set of driving system for the vessel  7 . The use of this apparatus also involves a novel method.  
         [0043]     This invention includes a waste-treating vessel  1  for the containing and treatment of medical wastes (not shown in the diagram). The wall of the waste-treating vessel  1  is manufactured with a vacuum layer for better insulation. Located at the front end of the vessel is a feed inlet and outlet  12  for waste feeding and removal, and a closure member  11  is provided covering the feed inlet and outlet  12 , by which the waste-treating vessel  1  can be closely sealed during the treatment of wastes. Inside the waste-treating vessel  1  and extended from the feed inlet and outlet  12  is a space of feed charging and discharging chamber  13 , while extended from the feed charging and discharging chamber  13  to the rear end of the vessel is the space of a storage chamber  14 . The volume of the feed charging and discharging chamber  13  is designed to accommodate the batch treatment capacity and normally takes up 70˜75% of the entire volume of the waste-treating vessel  1  to comply with the regulation on the feed charging ratio not more than 75-80%.  
         [0044]     With reference of  FIG. 3 ˜ 3   b,  a cutter and transmission system  2  is located between the feed charging and discharging chamber  13  and the storage chamber  14  inside the vessel  1  for reciprocating cutting of the medical waste. The cutter and transmission system comprises a set of cutters  23  which are mounted on a set of cutter shafts  22 . The cutter shafts  22  are mounted apart from each other with an equal spacing on a base plate  21 . On each pair of shafts  22 , each cutter  23  is positioned with an equal spacing along the shaft so that each cutter  23  on one shaft  22  is alternatively docked into the spacing between two cutters on the neighboring shafts. The spacing between two shafts  22  is properly arranged to avoid possible clogging during treatment. All the cutters  23  and shafts  22  are powered by a motor  24  and transmission systems  2 ,  2   a,  and  2   b  in a manner that cutters  23  on adjacent shafts  22  engage with one another to give a function of crushing the medical waste. Furthermore, in order to achieve better crushing effect, two or more sets of cutters can be installed in the cutter and transmission system  2 , one for coarse crushing (shredding) with a larger shaft spacing and another for fine crushing (grinding) with a smaller shaft spacing. The shredding cutter is normally placed near the feed charging and discharging chamber  13  and the grinding cutter near the storage chamber  14 . In addition, the two cutter plates are positioned so that the orientation of their shafts is arranged at an angle of 90 degrees to avoid possible dead zone of crushing. By this novel arrangement of cutter and transmission system  2 ,  2   a,  and  2   b,  medical waste materials are effectively fractured into small pieces and completely processed into regular wastes.  
         [0045]     As shown in  FIG. 2 , the gas buffering and cooling vessel  3  is installed outside the waste-treating vessel  1  to cool down the internal temperature of the waste-treating vessel  1  and to envelop the entire feed charging and discharging chamber  13  for the convenience of piping arrangement and better insulation.  
         [0046]     The air circulation system  4  comprises a set of vacuum pump  41 , two set of pipeline  42 , and four sets of in-line electromagnetic valves  43 . The feed charging and discharging chamber  13  is connected by one pipeline of the circulation system  4  with an inlet  45  and an outlet  47 . The gas buffering and cooling vessel  3  is also connected by another pipeline of the circulation system  4  with an inlet  44  and an outlet  46 . As shown in  FIG. 2 , the two types of pipeline are also interchangeably connected for the convenience of air pressure regulation and circulation.  
         [0047]     To begin with the operation for the gas buffering and cooling vessel  3 , close the inlet  44  while keeping the outlet  46  open. Turn on the vacuum pump  41  to withdraw air from the gas buffering and cooling vessel  3  to the atmosphere until a preset vacuum is achieved. After closing the outlet  46  of the gas buffering and cooling vessel, turn on the inlet  44  of the gas buffering and cooling vessel and the outlet  47  of the waste-treating vessel. Turn on the vacuum pump  41  to withdraw air from the waste-treating vessel  1  to the gas buffering and cooling vessel  3  until a preset vacuum is achieved. Turn off the outlet  47  of the waste-treating vessel  1  and the inlet  44  of the gas buffering and cooling vessel  3 .  
         [0048]     The steam supply system  5  consists of a steam generator  51 , a steam pipeline  52 , and an in-line steam electromagnetic valve  53 . The steam pipeline  52  is connected into the waste-treating vessel  1  with a steam inlet  54 . Turn on the steam inlet  54  and the steam generator  51  to supply steam into the waste-treating vessel  1  until a preset pressure and temperature is achieved.  
         [0049]     The heat exchange system  6  consists of a cooling water circulation pump  61 , a cooling device  62 , a heat exchanger  63 , a cooling water pipeline  64  and a cooling water electromagnetic valve  65  at the cooling water pipeline  64 , in which the heat exchanger  63  is installed within the gas buffering and cooling vessel  3  and on the outside surface of the waste-treating vessel  1 . After completion of the sterilization, turn on the cooling water pump so that the cooling water is circulated through the cooling water pipeline  64  into the heat exchanger  63  to cool the hot steam in the waste-treating vessel  1 . The water condensed from the cooling in the gas buffering and cooling vessel can be discharged from a condensed water valve  66  installed at the bottom of the gas buffering and cooling vessel  3 .  
         [0050]     With reference to  FIG. 1   a,  the driving system  7  consists of two supporting beams  71  for the waste-treating vessel  1 . The two ends of each supporting beam  71  are connected to a reciprocating wheel  72 , as shown in  FIGS. 4 and 5 . As shown in  FIG. 5B , the wheel  72  is driven by a chain or gear  73 , which is in turn driven by a driving gear  74  ( FIG. 4A ). The driving gear  74  is installed on the top of a supporting base  75  and driven by a motor  76  ( FIG. 4 ). Further, the waste-treating vessel  1  in the apparatus according to the invention can be moved reciprocatingly using a rotary mode or other approaches to cut the medical waste reciprocatingly.  
         [0051]     With reference to  FIG. 6 , the apparatus described above is operated by the following procedure: 
        a. Turn off all the valves of the gas buffering and cooling vessel  3 , except for the outlet  46 . Turn on the vacuum pump  41  to withdraw air from gas buffering and cooling vessel  3  to the atmosphere until a preset vacuum of the gas buffering and cooling vessel  3  is achieved;     b. Turn on the driving motor  76  of the driving system  7  to rotate the waste-treating vessel  1  at a preset angle convenient for waste loading. Open the closure member  11  and load the wastes (normally 50˜250 kg/batch) to the waste-treating vessel  1 ;     c. Close the closure member  11  and all the ports of the waste-treating vessel  1 , except for the air inlet  44  of the gas buffering and cooling vessel  3  and the air outlet of the treatment vessel  1 . Turn on the vacuum pump  41  to withdraw the air from the waste-treating vessel  1  into the gas buffering and cooling vessel  3  until a present vacuum of the waste-treating vessel  1  is achieved;     d. Open the steam inlet  54  and turn on the steam generator  51  to facilitate steam into waste-treating vessel  1  to increase the temperature and pressure within the feed charging and discharging chamber  13  (such as 135° C. and 3.4 atm);     e. Turn on the cutter and transmission system  2  and the driving system  7  so that the waste materials can be fractured into small pieces by moving back and forth between the feed charging and discharging chamber  13  and storage chamber  14 .     f. After a period of time of treatment, open the air inlet  44  of the gas buffering and cooling vessel, the air outlet  47  of the waste-treating vessel, and the vacuum pump  41  to allow air being circulating between the gas buffering and cooling vessel  3  and the waste-treating vessel  1  for sterilization of the contaminated air withdrawn from the waste-treating vessel  1  for pre-vacuum. The steam valve  53  is remained open during the entire treatment of the waste.     g. After a preset period of time, turn off the cutter and transmission system  2  and the driving system  7 . Turn on the cooling water circulation pump  61  and cooling device  62  to allow the steam in the waste-treating vessel  1  to be cooled off until a preset temperature and pressure.     h. Open the condensed water valve  8  to discharge the water condensed in the gas buffering and cooling vessel  3  as a result of the cooling process.     i. Turn on the driving system  7  so that the feed inlet and outlet  12  of the waste-treating vessel  1  is rotated to a position convenient for unloading of the waste being completely processed. The processed waste materials can now be further treated or disposed as the regular wastes. 
 
 [Features and Effects]
       
 
         [0061]     The apparatus having a reciprocating autoclave with internal cutters (RAIC) for treatment of medical wastes provided according to the invention has following advantages over the recited patents and other conventional techniques: 
        1. With the inventive apparatus, medical wastes such as, for example, needles, surgical knife, syringes, rubber hose or tissue sections, and the like, could be placed directly in the treating vessel of the inventive apparatus without being sorted and screened, such that the labor and time can be saved and undue secondary contamination can be avoided.     2. The inventive apparatus can accomplish the treatment of medical wastes by crushing, sterilizing and cooling waste materials simultaneously in the treating vessel during a continuous treating process such that the steam penetratability can be increased and that the entire treatment can be completed at reduced time, comparing with conventional autoclaving methods with greatly increased efficiency.     3. The inventive apparatus is particularly designed to have a gas buffering and cooling vessel, whereby a pre-vacuum operation of the waste-treating vessel can be carried out to eliminate the formation of dead spaces among cold regions during steam sterilization and hence the treating efficiency could not be influenced.     4. With the inventive apparatus, gas drawn in the gas-buffering vessel during the pre-vacuum operation can be transferred continuously into the waste-treating vessel for sterilizing so that the subsequent treatment and disposal in the conventional technique can be eliminated.     5. After sterilization of the waste in the inventive apparatus, the high temperature steam in the waste-treating vessel can be transferred and cooled in the gas buffering and cooling vessel so as to avoid the emission of the mist and aerosols upon opening the cover of the vessel associated with the prior art technique and hence eliminate the problem relative to the view of odor.     6. The complete computerized operating process provided on the inventive apparatus can let the user accomplish the treatment of the medical waste material followed with a proper manner and simplified operating procedure without risk of operation accident.     7. The inventive apparatus is designed to be a compact profile and structure without the necessity of providing external track and crushing device so that necessary space for installing the apparatus can be greatly reduced and at the same time, both of the sterilization and crushing requirements can be achieved in a short time period and hence the sterilizing efficiency can be greatly increased and the cost of treating medical wastes can be lowered.        
 
         [0069]     Many changes and modifications in the above described embodiments of the invention can, of course be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.