Process for reduction of emissions in asphalt production

Abstract

A process and apparatus are disclosed that relate generally to a process for reducing harmful or unwanted emissions during the production of asphalt, such as blue smoke. The process includes the introduction of a pump around of the wax oil fraction for re-introduction into the vacuum tower. Additional desirable features include stripping trays below the wax oil collection tray and the feed zone. The result is to produce an asphalt product that creates less blue smoke in the hot mix plant. Another desirable feature is that a product can be created that meets Performance Grade specifications with the addition of polymers or other additives.

We claim:  
     
         1 . A process for separating a feed crude into fractional products comprising the steps of: 
 feeding the feed crude into a pre-flash vessel to produce therefrom an overhead light ends product and a liquid flashed crude feed;    introducing the flashed crude feed to a heater to produce a partially vaporized crude feed;    feeding the partially vaporized crude feed into a feed zone of a vacuum tower to produce from the vacuum tower an overhead vapor stream, a middle distillate oil fraction, a wax oil fraction, and a bottoms asphalt product; the feed zone being located below a wax oil collection tray that collect essentially all liquids on the wax oil collection tray into the wax oil fraction;    heating a portion of the wax oil fraction; and    feeding the portion of the heated wax oil fraction into the feed zone.    
     
     
         2 . The process of  claim 1  further comprising the step of feeding the portion of the wax oil fraction into the heater in combination with the liquid flashed crude feed.  
     
     
         3 . The process of  claim 1  further comprising the step of feeding the portion of the wax oil fraction into the pre-flash vessel in combination with the feed crude.  
     
     
         4 . The process of  claim 1  further comprising the step of introducing the portion of the heated wax oil fraction into a second flash vessel prior to introduction into the feed zone.  
     
     
         5 . The process of  claim 1  wherein the feed crude is Boscan Crude.  
     
     
         6 . The process of  claim 1  wherein the feed crude is Altimira Crude.  
     
     
         7 . The process of  claim 1  wherein the asphalt product meets the specification for Performance Grade 76-22, the asphalt product being neat.  
     
     
         8 . The process of  claim 1  further comprising introducing steam into a bottom stripping section of the vacuum tower.  
     
     
         9 . The process of  claim 1  further comprising pumping a portion of the middle distillate oil fraction to a location in the vacuum tower above a middle distillate oil collection tray, the middle distillate oil collection tray collecting essentially all liquids on the middle distillate oil collection tray into the middle distillate oil fraction.  
     
     
         10 . An apparatus for separating a feed crude into fractional products comprising: 
 a pre-flash vessel to receive and separate the feed crude into an overhead light ends product and a liquid flashed crude feed;    a heater to heat the liquid flashed crude feed to produce a partially vaporized crude feed;    a vacuum tower having a feed zone to receive the partially vaporized crude feed, the feed zone being located below a wax oil collection tray, the wax oil collection tray collecting essentially all liquids as a wax oil fraction, an asphalt product being removed from a bottom of the tower; and    a pump to receive the wax oil fraction and introduce at least a portion of the wax oil fraction into the feed zone.    
     
     
         11 . The apparatus of  claim 10  wherein the pump moves the portion of the wax oil fraction into the heater prior to the wax oil fraction portion being introduced in combination with the partially vaporized crude feed to the feed zone.  
     
     
         12 . The apparatus of  claim 10  wherein the pump moves the portion of the wax oil fraction into the pre-flash vessel in combination with the feed crude such that the wax oil fraction portion is flashed then heated prior to introduction into the feed zone.  
     
     
         13 . The apparatus of  claim 10  further comprising a second flash vessel for receiving the portion of the wax oil fraction prior to introduction of the portion of wax oil fraction into the feed zone.  
     
     
         14 . The apparatus of  claim 10  wherein the vacuum tower includes a bottom stripping section below the feed zone, further comprising means for introducing steam to the bottom stripping section.  
     
     
         15 . The apparatus of  claim 10  wherein the vacuum tower includes a middle distillate oil collection tray, further comprising a pump-around that pumps a portion of the middle distillate oil fraction to a location in the vacuum tower above the middle distillate oil collection tray, essentially all liquids on the middle distillate oil collection tray being collected into the middle distillate oil fraction.  
     
     
         16 . The apparatus of  claim 10  wherein the feed crude is Boscan Crude.  
     
     
         17 . The apparatus of  claim 10  wherein the feed crude is Altimira Crude.  
     
     
         18 . The apparatus of  claim 10  wherein the asphalt product from the vacuum tower meets the specification for Performance Grade 76-22, the asphalt product being neat.