Method of operating a temperature-controlled thermokinetic mixer for regenerating vulcanized rubber

Abstract

A method of operating a temperature-controlled K-mixer for thermally and kinetically regenerating vulcanized crumb rubber is provided. The K-mixer includes a chamber and a shaft provided with a plurality of blades. The method includes the steps of inserting a mixture of vulcanized crumb rubber and a lubricant in the chamber of the K-mixer; heating the mixture by rotating the shaft of the K-mixer until the temperature of the mixture has reached a devulcanizing or regeneration temperature; cooling the mixture by reducing the rotational speed of the K-mixer and by circulating a cooling fluid in the shaft and in channels of the blades.

1 . A method of operating a temperature-controlled K-mixer for thermally and kinetically regenerating vulcanized crumb rubber, said K-mixer including a chamber and a shaft provided with a plurality of blades, the method comprising the steps of:
 inserting a mixture of vulcanized crumb rubber and a lubricant in the chamber of the K-mixer;   heating the mixture by rotating the shaft of the K-mixer until the temperature of the mixture has reached a devulcanizing temperature;   cooling the mixture by reducing the rotational speed of the K-mixer and by circulating a cooling fluid in the shaft and in channels of the blades; and   recovering regenerated crumb rubber from the chamber.   
     
     
         2 . The method of  claim 1 , wherein the shaft of the K-mixer includes inner and outer passages in fluid communication with the channels of the blades, and wherein circulating the cooling fluid comprises circulating fluid from one of the inner and outer passages, to the channels in the blades, to the other one of the inner and outer passages. 
     
     
         3 . The method of  claim 2 , wherein the blades of the shaft are respectively formed from at least one plate, the channels being formed at least partially within said at least one plate, and wherein the cooling fluid is circulated within said at least one plate forming the blade. 
     
     
         4 . The method of  claim 1 , wherein the flow of the cooling fluid in the channels of the blades is controlled individually within each blade. 
     
     
         5 . The method of  claim 2 , wherein the flow of the cooling fluid circulating in the inner and outer passages is controlled with a return flow adjustment mechanism. 
     
     
         6 . The method of  claim 1 , comprising measuring the temperature of the mixture inside the chamber, and wherein the circulation of a cooling fluid in the shaft and in the blades is regulated based on the measured temperature of the mixture. 
     
     
         7 . The method according to  claim 1 , wherein the step of cooling the mixture includes cooling the chamber by circulating water in a cooling jacket surrounding the mixing chamber. 
     
     
         8 . The method according to  claim 1 , wherein the step of cooling the mixture includes injecting a cooling agent in the mixing chamber. 
     
     
         9 . The method according to  claim 8 , wherein the cooling agent is injected using at least one spray nozzle in the form of a mist or of a stream. 
     
     
         10 . The method according to  claim 1 , wherein the step of heating the mixture is performed by increasing the rotational speed of the shaft to between 1700 and 2000 rpm. 
     
     
         11 . The method according to  claim 1 , wherein the step of heating the mixture is performed by increasing the rotational speed of the shaft to between 1750 and 1850 rpm. 
     
     
         12 . The method according to  claim 10 , wherein in the step of heating the mixture, the devulcanizing temperature is reached within a time period of 25 to 60 seconds. 
     
     
         13 . The method according to  claim 10 , wherein in the step of heating the mixture, the devulcanizing temperature is reached within a time period of 30 to 45 seconds. 
     
     
         14 . The method according to  claim 10 , wherein the step of cooling the mixture is performed until the temperature of the mixture has decreased to less than 125° C. 
     
     
         15 . The method according to  claim 10 , wherein the step of cooling the mixture is performed for less than 45 seconds. 
     
     
         16 . The method according to  claim 10 , wherein the step of cooling the mixture is performed for less than 35 seconds. 
     
     
         17 . The method according to  claim 1 , wherein the step of cooling the mixture is performed by reducing the rotational speed of the shaft to between 400 and 700 rpm. 
     
     
         18 . The method according to  claim 1 , wherein the step of cooling the mixture is performed by reducing the rotational speed of the shaft to about 600 rpm. 
     
     
         19 . The method according to  claim 1 , comprising a step of mixing the vulcanized crumb rubber and the lubricant prior to transferring the mixture to the chamber. 
     
     
         20 . The method according to  claim 1 , wherein the devulcanizing temperature is between 210° C. to 225° C. 
     
     
         21 . A method of operating a temperature-controlled K-mixer for thermally and kinetically treating vulcanized crumb rubber, said K-mixer including a chamber and a shaft provided with a plurality of blades, the method comprising the steps of:
 mixing vulcanized crumb rubber and oil to form a mixture;   transferring the mixture to the chamber of the K-mixer;   heating the mixture by rotating the shaft of the K-mixer between 1700 and 2000 rpm, for a heating time period of between 25 to 60 seconds, until the temperature of the mixture has reached a devulcanizing temperature;   cooling the mixture by reducing the rotational speed of the K-mixer to between 400 and 700 rpm, for cooling time period of less than 40 seconds, by circulating a cooling fluid in the shaft and in channels of the blades, the blades of the shaft being respectively formed from at least one plate, the channels being formed at least partially within said at least one plate, and wherein the cooling fluid is circulated within said at least one plate forming the blade; and by injecting a cooling agent in the mixing chamber; and   recovering regenerated crumb rubber from the chamber.   
     
     
         22 . The method according to  claim 21 , wherein in the step of cooling the mixture, the cooling fluid is oil and chamber is also cooled with cooling water jackets.