Process for converting tallow to diesel fuel

Abstract

A process for thermally cracking virgin or waste animal oils (tallow) into a diesel fuel product is provided. The thermal cracking process uses low cracking temperatures from 625 to 725° F. with ambient pressure and no catalyst to generate a column distilled fraction of diesel fuel mixed with light ends, the light ends being flashed off to produce a high quality #2 diesel fuel suitable for road use. The oils to be distilled are exposed to a heat exchanger with a skin temperature of 1750° F. generated by hot air produced by a thermal oxidizer. This results in the processed product going from a liquid to a liguid/gas during the pump around residence time of 3 to 5 seconds before moving up a distillation column as a gas to the desired finished product.

1 . A process for cracking tallow into diesel fuel comprising: 
 thermally cracking the tallow in a cracking vessel at a temperature that ranges from 500 to 700° F. at ambient pressure and in the absence of a catalyst to yield in part cracked hydrocarbons;    separating the cracked hydrocarbons in a distillation column from other products of cracking; and    collecting the cracked hydrocarbons as diesel fuel.    
   
   
       2 . The process of  claim 1 , in which cracking the tallow in the cracking vessel further yields a gas fraction that is consumed to fuel the process.  
   
   
       3 . The process of  claim 1 , which further comprises: 
 maintaining a cracking temperature in the cracking vessel by continuous introduction into the cracking vessl of additional preheated tallow; and    continuously withdrawing cracked hydrocarbons from the cracking vessel.    
   
   
       4 . The process of  claim 2  which further comprises using a thermal oxidizer fueled by the gas fraction to generate heat for the process.  
   
   
       5 . The process of  claim 4  which further comprises supplying a constant stream of preheated tallow to a heat recovery device which receives heat from the thermal oxidizer to further preheat the tallow creating a stream of additionally preheated tallow which is thus heated to at least the cracking temperature.  
   
   
       6 . The process of  claim 5  which further comprises continuously introducing the additionally preheated tallow into the cracking vessel in an amount to compensate for cracked hydrocarbons and other products of cracking removed from the cracking vessel to maintain a volume of tallow in the cracking vessel.  
   
   
       7 . The process of  claim 1  in which the products of cracking include a vaporized fraction that comprises cracked hydrocarbons and light ends, and which further comprises separating the light ends from the vaporized fraction to leave a remaining portion that constitutes a diesel fuel.  
   
   
       8 . The process of  claim 1 , wherein the diesel fuel comprises a No. 2 diesel fuel.  
   
   
       9 . The process of  claim 1 , wherein the tallow contains water preferably in a range of 2 to 7%.  
   
   
       10 . The process of  claim 5 , which further comprises, prior to further preheating of the tallow by the heat recovery device, initially heating the tallow to a first temperature by passing the tallow through at least one heat exchanger which is supplied with heat from at least one of collected diesel fuel and a portion of liquid fraction withdrawn from the cracking vessel.  
   
   
       11 . The process of  claim 10 , wherein the first temperature is preferably 500° F.  
   
   
       12 . The process of  claim 7 , wherein the vaporized fraction of hydrocarbons enters the distillation column directly from the cracking vessel.  
   
   
       13 . The process of  claim 1 , wherein the cracking temperature is preferably in a range of 625 to 700° F.  
   
   
       14 . The process of  claim 5 , wherein a first fuel oil is withdrawn at a rate within a range of 0% to 10% in relation to a rate at which additionally preheated tallow is introduced.  
   
   
       15 . A process for cracking tallow into a plurality of fuel oils comprising: 
 thermally cracking the tallow in a cracking vessel at a temperature that ranges from 625 to 700° F. at ambient pressure and in the absence of a catalyst to yield a vaporized fraction of cracked hydrocarbons and a liquid fraction of a fuel oil other than diesel;    collecting the fuel oil other than diesel;    separating the vaporized fraction of cracked hydrocarbons in a distillation column from other products of cracking; and    collecting the cracked hydrocarbons as diesel fuel.    
   
   
       16 . The process of  claim 15 , in which cracking the tallow in the cracking vessel further yields a gas fraction that is consumed to fuel the process.  
   
   
       17 . The process of  claim 15 , which further comprises: 
 maintaining a cracking temperature in the cracking vessel by continuous introduction into the cracking vessl of additional preheated tallow; and    continuously withdrawing cracked hydrocarbons from the cracking vessel.    
   
   
       18 . The process of  claim 16  which further comprises using a thermal oxidizer fueled by the gas fraction to generate heat for the process.  
   
   
       19 . The process of  claim 18  which further comprises supplying a constant stream of preheated tallow to a heat recovery device which receives heat from the thermal oxidizer to further preheat the tallow creating a stream of additionally preheated tallow which is thus heated to at least the cracking temperature.  
   
   
       20 . The process of  claim 19  which further comprises continuously introducing the additionally preheated tallow into the cracking vessel in an amount to compensate for cracked hydrocarbons and other products of cracking removed from the cracking vessel to maintain a volume of tallow in the cracking vessel.  
   
   
       21 . The process of  claim 15  in which the products of cracking include a vaporized fraction that comprises cracked hydrocarbons and light ends, and which further comprises separating the light ends from the vaporized fraction to leave a remaining portion that constitutes a diesel fuel.  
   
   
       22 . The process of  claim 19 , which further comprises, prior to further preheating of the tallow by the heat recovery device, initially heating the tallow to a first temperature by passing the tallow through at least one heat exchanger which is supplied with heat from at least one of collected diesel fuel and a portion of liquid fraction withdrawn from the cracking vessel.