Patent Publication Number: US-2023151161-A1

Title: Method and system for odour abatement in rubber processing

Description:
CROSS-REFERENCE TO OTHER APPLICATIONS 
     This document claims priority from U.S. Provisional Application No. 63/007,567 filed Apr. 9, 2020, which is hereby incorporated herein by reference. 
    
    
     FIELD 
     The disclosure is generally directed at odour abatement in industrial applications, and more specifically, at a method and system for odour abatement in rubber processing. 
     BACKGROUND 
     It is well known that heating rubber, for example, in tire manufacturing, typically produces an odour. Available commercial solutions for addressing this issue include activated carbon filters, chemical adsorbent and oxidation. While these can treat fugitive process emission, they do not control odour from the product which continues to emit odour as it off-gases in storage and transport. 
     In non-chemical devulcanization of waste rubber, vulcanized rubber crumb is continuously fed into a twin-screw extruder for thermomechanical conversion to elastomeric devulcanized rubber. The extrudate, as it exits the extruder, is hot and emits a strong odour. The odorous gases can be contained and put through an activated carbon filter which to some extent reduces the intensity of the odour. However, residual odour accumulation, particularly in workplaces with limited venting for air exchange, renders this strategy ineffective. 
     Another cause of odour is from the slow and persistent off-gassing of the devulcanized rubber in storage and in transport. 
     Therefore, there is provided a method and system for odour abatement that overcomes at least some of the disadvantages of current systems. 
     SUMMARY 
     The present disclosure provides a novel method and system for odour abatement in industrial applications, such as, but not limited to, rubber processing. The disclosure assists to reduce the intensity of the odour in fugitive emission and/or to neutralize and reduce or prevent odour emission in storage and transport. 
     In one aspect of the disclosure, there is provided a method for odour abatement in industrial applications, the method including applying a fabric softener to rubber product. 
     In another aspect, the method further includes devulcanizing the rubber product. In yet another aspect, the method further includes providing a solution that includes between 2 and 10% fabric softener, wherein applying a fabric softener to the rubber product includes applying the solution to the rubber product. In a further aspect, applying a fabric softener to the rubber product includes applying a fabric softener to an extrudate. In yet a further aspect, applying a fabric softener to the rubber product includes passing the rubber product through a dip tank. In another aspect, the fabric softener includes an anti-tack agent. In an aspect, the fabric softener includes bleach. 
     In another aspect, devulcanizing the rubber product includes passing the rubber product through an extruder. In a further aspect, applying a fabric softener to the rubber product includes commingling the fabric softener and the rubber product within the extruder. In yet another aspect, applying a fabric softener to the rubber product includes dosing the rubber product with the fabric softener prior to passing the rubber product through the extruder. In another aspect, the method includes cooling the rubber product by coating with fabric softener and/or a fabric softener solution in water. In yet another aspect, cooling the rubber product occurs simultaneously with introducing the solution to the rubber product. In another aspect, the method further includes drying the rubber product. In another aspect, cooling the rubber product occurs simultaneously with drying the rubber product. 
     In another aspect of the disclosure, there is provided an apparatus for odour abatement, the apparatus including a dip tank to receive a rubber product and to hold a liquid including fabric softener; and a conveyor to convey the rubber product out of the dip tank. 
     In a further aspect, the apparatus further includes a dip tank liquid feeding apparatus. 
     In a further aspect of the disclosure there is provided an apparatus for odour abatement, the apparatus including an extruder having a feed inlet to receive a rubber product; and a liquid feeding apparatus coupled to the extruder to apply fabric softener to the rubber product. 
     In another aspect, the liquid feeding apparatus is coupled to the feed inlet to apply the fabric softener to the rubber product as the rubber product enters the extruder. In a further aspect, the liquid feeding apparatus is coupled to the extruder to commingle the fabric softener and the rubber product within the extruder. In yet another aspect, the apparatus includes a devolatilization outlet and a condenser, wherein the liquid feeding apparatus is coupled to the condenser to supply fabric softener to commingle with a condensate formed by the condenser. In yet another aspect, the apparatus further includes an activated carbon filter with a fabric softener wet pad. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages of the disclosure will be apparent from the following description of embodiments thereof as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the disclosure and to enable a person skilled in the pertinent art to make and use the invention. The drawings are not to scale. 
         FIG.  1    is a schematic view of an apparatus for odour abatement in industrial applications according to an embodiment herein; 
         FIG.  2    illustrates experimental results for an odour abatement test; 
         FIG.  3   a    is a flow diagram for a method for odour abatement in industrial applications according to an embodiment herein; 
         FIG.  3   b    is a flow diagram of another method for odour abatement in industrial applications according to an embodiment herein; 
         FIG.  3   c    is a flow diagram of yet another method for odour abatement in industrial applications according to an embodiment herein; 
         FIG.  4    is a schematic view of an apparatus for odour abatement in industrial applications according to another embodiment herein; 
         FIG.  5    is a schematic view of an apparatus for odour abatement in industrial applications according to another embodiment herein; and 
         FIG.  6    is a schematic view of an apparatus for odour abatement in industrial applications according to another embodiment herein. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to a method and system for odour abatement in industrial applications, such as, but not limited to, rubber process. In one embodiment, the disclosure includes a novel use of a fabric softener (typically designed for treatment of fabrics during washing and/or drying) for industrial odour abatement. One advantage of the disclosure is that the application of the fabric softener product in the devulcanization of waste rubber provides at least one of odour suppression, abatement and encapsulation. 
       FIG.  1    is a schematic diagram of an apparatus for odour abatement  100 . Apparatus  100  includes a dip tank  102 , and a cooling conveyor  104 . In operation, after a hot rubber product or a rubber extrudate  106  has been manufactured, for example by devulcanizing rubber, the rubber product  106  is passed through the dip tank  102  that includes a liquid  108  for cooling and treating the hot, devulcanized, rubber product  106 . The liquid  108  within the dip tank  102  may be a fabric softener, including a combination of a liquid fabric softener, or a liquid having similar chemical properties to a fabric softener, and water. In other words, the liquid  108  may be a solution. In another embodiment, the liquid  108  may be a combination of water and a solid or powdered fabric softener that is dissolved into the water. In yet a further embodiment, the liquid  108  may be a combination of a fabric softener (either solid or liquid) mixed with a liquid that is approximately pH neutral to react with the fabric softener which typically has a pH of approximately 6. In some embodiments, the liquid  108  may include an anti-tack solution. In some embodiments, the liquid  108  may include bleach. The apparatus may further include a dip tank liquid feeding apparatus  110  for continuously filling the dip tank to maintain the level of the liquid  108  and/or the amount of fabric softener within the liquid  108  at a predetermined level or percentage. In the current embodiment, the dip tank liquid feeding apparatus  110  includes a reservoir  111  where the liquid may be mixed and then delivered or transported to the dip tank  102  via a series of pipes and pumps and/or other equipment. Alternatively, the fabric softener may be manually added to the dip tank  102  with the dip tank liquid feeding apparatus  110  supplying water for the liquid  108 . In a specific embodiment, for a 150 L tank, the percentage of fabric softener within the liquid  108  may be between 3 and 10% by volume. Other percentages may be contemplated based on an intensity of the odor released by the rubber product or rubber extrudate. 
     In addition, depending on the industrial application or the level of odour abatement, the percentage level of fabric softener within the liquid  108  may be higher or lower than this range. Depending on the source fabric softener, whether it is commercial or industrial grade, based on the predetermined or desired percentage concentration of fabric softener in the liquid  108 , the amount of commercial or industrial grade fabric softener that is needed to be added may be calculated. After being dipped in the dip tank  102 , the rubber product  106  may then be passed to a packaging station via a conveyor belt, such as the cooling conveyor, or cooling conveyor belt  104 . 
     In  FIG.  1   , the hot rubber product  106  is shown as a continuous strip, however, other forms, such as, but not limited to, a continuous rope of rubber, rubber chunks, rubber pellets or rubber slabs/sheets may be treated in a similar or different manner via the application of the liquid  108  to the hot rubber product. In some embodiments, where the hot rubber product  106  are chunks or pellets of rubber, the rubber product  106  may be dipped into the dip tank  102  and dragged up by a mesh conveyor onto the cooling conveyor  104 . 
     In an alternative embodiment, fabric softener wet pads may be added to the odour abatement process, such as, after active carbon filters, that are currently used in odour abatement to improve odour abatement. 
     In a further embodiment, the liquid  108  containing fabric softener is sprayed onto the surface of the hot devulcanized rubber product  106  after it has been manufactured. The percentage concentration of the fabric softener within the liquid  108  is at a predetermined level based on the industrial application or level of odour abatement required. In this embodiment, the devulcanized rubber product  106  may be in the form of a continuous strip, rope, slabs/sheets, chunks, or pellets. The surface wetted devulcanized rubber product  106  is then dried and cooled for further processing or packaging. 
       FIG.  2    is directed at a chart outlining experimental results of odour suppression by the use of a fabric softener in a production environment. The experiment was performed during a test production run of 250 minutes where waste tire rubber crumb was devulcanized at the rate of 500 kg/h. In this experiment, or test, the production space had only limited venting to the outside. Odour intensity, as agreed among production personnel, is presented qualitatively between 0 and 10 (the vertical axis) where 10 was rated as “unbearable”. The horizontal axis represents the time, in minutes, from production start. As can be seen,  FIG.  2    shows that fabric softener is effective at odour suppression during rubber processing. Reduced odour intensity may allow for venting to the outside to further abate odour in the workplace. 
       FIG.  3   a    is a flow diagram for a first embodiment of a method  300  for odour abatement during rubber processing is shown. 
     At  302 , a rubber product, such as a rubber crumb, is devulcanized. Devulcanizing of the rubber crumb is a process where crosslinked chains/bonds are chemically broken, generating the odor that the current disclosure abates. Devulcanization of the rubber is thermomechanical process that also results in the rubber, being heated. 
     Devulcanization or heating the rubber crumb, or rubber product, may include passing the rubber crumb through an extruder, for example a twin-screw extruder. A non-exclusive example of rubber devulcanization is non-chemical devulcanization, which may include the use of supercritical carbon dioxide within an extruder. 
     At  304 , a fabric softener is applied to the rubber product. Applying the fabric softener to the rubber product may include dipping the rubber product into the fabric softener or a liquid including the fabric softener (e.g. passing the rubber product through a dip tank), spraying the fabric softener or a liquid including the fabric softener onto the rubber product, or commingling the fabric softener and the rubber product. Spraying the fabric softener (or a solution including the fabric softener) onto the rubber product may also occur prior to or during heating or devulcanizing the rubber product as discussed below. The method may further include providing a solution that includes between 1 and 10% by volume fabric softener, although other percentage concentrations are contemplated, in which case applying the fabric softener to the rubber product includes applying the solution to the rubber product. If a solution including the fabric softener is placed within a dip tank, the dip tank may be refilled at regular time intervals in order to somewhat regularly maintain the predetermined percentage concentration of fabric softener within the solution. Depending on the industrial application that the odour abatement is being used for, further components, such as, but not limited to, an anti-tack liquid or bleach, may be added to the solution. The rubber product may come in different forms, such as, but not limited to, rubber crumb, a rubber extrudate, a continuous strip, a rope, rubber slabs/sheets, rubber chunks, or rubber pellets. 
     At  306 , the method  300  may further include cooling the hot rubber product. In some embodiments, this cooling may occur when the hot rubber product is dipped into the dip tank. In other embodiments, the cooling may be done as the hot rubber product travels to a packaging station via a cooling conveyor belt, via fans, cooling tower with cyclone or via other known cooling processes after the fabric softener/solution is applied or sprayed onto the product. In some embodiments, the cooling may be done by applying more fabric softener/solution. 
     At  308 , the method  300  may further include drying the rubber product. In some embodiments, the rubber product may be dried and cooled at the same time (i.e., simultaneously). In some other embodiments, the rubber product may be dried as it is being passed to a packaging station. The rubber product may also be air dried or passed through a dryer. In some embodiments, the cooled rubber product may be dried via exposure to moving air, warm air, forced air or via evaporation. 
     The odour abated rubber product may be passed for further processing such as to a packaging station. 
     Further specific examples of the use of fabric softener in odour abatement for industrial applications, such as, rubber processing, are discussed below. 
     EXAMPLE 1 
     Referring to  FIG.  1   , 3 L of a commercial fabric softener, such as, but not limited to, Ultra Downy® Protect and Refresh™ Liquid Fabric Softener—Active Fresh was added to the dip tank containing 150 L of water to generate a solution  108 . As the hot rubber product  106  passed through the solution  108 , it warmed up the solution  108 , applied coating to the rubber product  106  and dragged some of the solution  108  with it. In order to maintain the percentage concentration of fabric softener at the predetermined concertation within the solution  108 , 3 L of fabric softener and 60 L of water may be added every hour to the dip tank  102  or the dip tank liquid feeding apparatus  110  to make up for solution loss. 
     EXAMPLE 2 
     Again, referring to  FIG.  1   , 3 L of a commercial fabric softener, such as, but not limited to, Ultra Downy® Infusions™ Amber Blossom, was added to the dip tank  102  containing 150 L of water with 3% by weight Polycoat™ 323 HS (4), an industrial anti-tack agent that coats the rubber product  106  to prevent or reduce the likelihood of the rubber product  106  sticking to itself when piled up. In order to maintain the percentage concentration of fabric softener at the predetermined concertation within the solution  108 , 3 L of fabric softener and 60 L of water containing 3% by volume anti-tack may be added every hour to make up for solution loss. 
     EXAMPLE 3 
     Again, referring to  FIG.  1   , 3 L of a commercial fabric softener such as, but not limited to, Ultra Downy® Fabric Softener—Clean Breeze®, was added to the dip tank  102  containing 150 L of a solution  108  as in Example 2. To this solution  108  was added 2.4 L of a commercially available bleach. In order to maintain the percentage concentration of fabric softener at the predetermined concertation within the solution  108 , 3 L of fabric softener and 60 L of water containing anti-tack, and 1.2 L of bleach were added to the dip tank  102 , such as directly or via the dip tank liquid feeding apparatus  110  to make up for solution loss. 
     The addition of bleach further improved odour suppression as judged by the qualitative peer odour intensity assessment as shown in  FIG.  2   . 
     In all the examples above, the use of fabric softener significantly reduced the odour from continued off-gassing of the processed rubber product in storage. 
     In another embodiment, process vent gases may be treated with fabric softener for odour abatement, for example, in a scrubber application. In this application, the hot and odorous vent gas may be bubbled through a vessel containing a solution containing fabric softener. In another embodiment, for general workplace odour control or abatement, room air can be circulated through a filter pad continuously wetted with a solution including fabric softener at a predetermined percentage concentration. 
       FIG.  4    is a schematic view of an apparatus  400  for odour abatement in industrial applications. Apparatus  400  includes an extruder  402 , a feed inlet  404 , and a liquid feeding apparatus  406 . The liquid feeding apparatus  406  may be substantively similar to liquid feeding apparatus  110 . In operation, a rubber product, such as, but not limited to rubber crumb  408  (for example, vulcanized rubber crumb) may be fed into feed inlet  404 . The liquid feeding apparatus  406  applies fabric softener, for example a solution containing fabric softener, to the rubber crumb  408  as it enters the apparatus  400 . The rubber, product or crumb  408  and the fabric softener are commingled within the apparatus  400 , either within the feed inlet  404  or within the extruder  402 . The extruder then heats and processes the rubber crumb, for example via non-chemical devulcanization. The commingling of the fabric softener and the rubber crumb  408  abates odours during and/or after heating and processing the rubber crumb. 
     The fabric softener may be applied to the rubber crumb  408  by spraying the fabric softener delivered by the liquid feeding apparatus into the feed inlet  404  such as via a set of pressurized jets or sprinklers. The fabric softener may be part of a solution, for example a solution containing water and 1 to 6% by volume liquid commercial fabric softener. The fabric softener may be delivered at a volume equal to up to 5% by weight, preferably 1% by weight. 
     Turning to  FIG.  3   b   , another embodiment of a method  310  for odour abatement during rubber processing is shown. In this embodiment, fabric softener is applied to a rubber crumb  312 . For example, such as with the apparatus of  FIG.  4   , the fabric softener is applied to the rubber crumb before it enters the extruder to be devulcanized, such as in the feed inlet. 
     In select embodiments where heating or devulcanizing the rubber crumb includes passing the rubber crumb through an extruder, applying the fabric softener to the rubber crumb may include applying (e.g. dosing) the fabric softener to rubber crumb prior to feeding the rubber crumb into the extruder or while feeding the rubber crumb into the extruder. In one embodiment, the fabric softener may be applied as a solution containing fabric softener at a volume of at least approximately 1 L of fabric softener/solution per 100 kg rubber crumb, i.e., 1% by weight. In alternative embodiments, the fabric softener may be applied and/or injected at a volume of up to 5% by weight. 
     The rubber crumb is then devulcanized  314 . Again, with the apparatus of  FIG.  4   , the rubber crumb is devulcanized and/or heated as it passes through the extruder. After being devulcanized, the rubber product is then cooled  316  and/or dried  318 . The cooling and drying may be performed as discussed above with  306  and  308 . 
       FIG.  5    is a schematic view of an apparatus  500  for odour abatement in industrial applications. Apparatus  500  is similar in some ways to apparatus  400 , therefore the differences between apparatus  400  and apparatus  500  will be discussed in detail only. Apparatus  500  includes an extruder  402 , a feed inlet  404 , and a liquid feeding apparatus  412 . The liquid feeding apparatus  412  is similar to the liquid feeding apparatus  406 , however while the liquid feeding apparatus  406  applies fabric softener to the rubber product, or crumb  408  as the rubber crumb  408  enters the feed inlet  404 , the liquid feeding apparatus  412  injects the fabric softener into the rubber crumb  408  while the rubber crumb  408  is within the extruder  402 . 
     Turning to  FIG.  3   c   , another embodiment of a method  320  for odour abatement during rubber processing is shown. In this embodiment, fabric softener is applied to a rubber crumb as the rubber crumb is being devulcanized  322 . For example, such as with the apparatus of  FIG.  5   , the fabric softener is applied to the rubber crumb as it passes through the extruder. The fabric softener may be seen as being commingled with the rubber crumb. In this embodiment, the fabric softener can be seen as being injected into the extruder to apply the fabric softener to the rubber crumb. 
     In one embodiment, the fabric softener may be applied as a solution containing fabric softener at a volume of at least approximately 1 L of fabric softener/solution per 100 kg rubber crumb, i.e., 1% by weight. In alternative embodiments, the fabric softener may be applied and/or injected at a volume of up to 5% by weight. 
     After being devulcanized, the rubber product is then cooled  324  and/or dried  326 . The cooling and drying may be performed as discussed above with  306  and  308 . 
       FIG.  6    is a schematic view of an apparatus  600  for odour abatement in industrial applications. Apparatus  600  is similar in some ways to apparatus  400  and apparatus  500 . Apparatus  600  includes an extruder  402 , a feed inlet  404 , a liquid feeding apparatus  414 , a devolatilization outlet  416 , and a condenser  418 . Devolatilization outlet  416  allows for devolatilization of the rubber crumb  408  by allowing volatile gases within the extruder  402  to exit the extruder and travel to condenser  418 . Condenser  418  condenses the volatile gases to form a condensate. The liquid feeding apparatus  414  is similar to the liquid feeding apparatus  406  and  412 , however instead of supplying fabric softener for commingling with the rubber crumb  408 , the liquid feeding apparatus  414  supplies fabric softener for commingling with the condensate. The condensate, after commingling with the fabric softener, has an abated odour. The condenser  418  may have an outlet port to feed the volatile gases that did not condense in the condenser  418 , to the activated carbon filter for further odor abatement. This activated carbon filter may include fabric softener as a wet pad to further assist in the odour abatement. Another addition to the condenser  418  might be addition of an oxidizer/combustion chamber in series to the condenser  418 , which will burn off volatiles that burn at high temperatures. 
     A skilled person, having the benefit of the present disclosure, will appreciate that the above embodiments may be combined to provide enhanced odour abatement. For example, fabric softener may be commingled with the rubber product within an extruder that forms an extrudate. The extrudate may then be passed through a dip tank containing a solution of fabric softener, and additional solution may be sprayed onto the extrudate after the rubber product exits the dip tank. 
     Although the present disclosure has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present disclosure. 
     In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that these specific details may not be required. In other instances, well-known structures may be shown in block diagram form in order not to obscure the understanding. 
     The above-described embodiments of the disclosure are intended to be examples of the present disclosure and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the disclosure.