Systems and Processes for Improving Distillate Yield and Quality

Abstract

Systems and processes for improving quality and yield of one or more distillate products generated in a distillation column are disclosed. The system comprises a feed inlet distributor that reduces the amount of liquid entrained in vapor rising from the feed zone of the distillation column, a wash zone collection apparatus having an improved design for collecting slop wax falling from a liquid/vapor contacting structure provided in the wash zone, a recirculation subsystem for recirculating at least a portion of the collected slop wax to the top of the wash zone for distribution as wash oil, and a control subsystem. The feed inlet distributor ensures a horizontal fluid flow path free of transverse surfaces thereby minimizing atomization of liquid droplets entrained in vapor in the feed stream.

1 . A process for improving quality and yield of one or more distillate products drawn from a distillation column whose feed stream is a mixture of vapor and a liquid containing one or more components that are substantially non-volatile at column conditions, the distillation column comprising a feed zone, a wash zone located above the feed zone having disposed therein a liquid/vapor contacting structure and a wash oil distributor for distributing wash oil to the upper surface of the contacting structure, and means above the wash zone to remove the vapor product or liquid condensed therefrom, the process comprising:
 collecting a liquid (“slop wax”) falling from the wash zone contacting structure by means of a collection apparatus disposed below the wash zone and above the feed zone;   withdrawing the slop wax from the collection apparatus to a slop wax pump;   conducting at least a portion of a slop wax pump discharge liquid to the wash oil distributor at a rate sufficient to assure thorough wetting of the wash oil liquid/vapor contacting structure and to substantially eliminate entrained liquid or solid particles from vapor rising from the wash zone; and   adding to the slop wax stream conducted to the wash oil distributor only enough of a heaviest distillate product as makeup to maintain a liquid level on the slop wax collection apparatus.   
     
     
         2 . The process of  claim 1 , wherein the wash zone irrigated only by the slop wax and the makeup distillate, if any, comprises the sole means of removing entrained liquid or solids from the vapor rising from the feed zone, thereby minimizing the amount of distillate product downgraded by use as wash oil, and the vapor rising from the wash zone is substantially free of entrained non-volatile material. 
     
     
         3 . The process of  claim 1 , wherein enough heat is removed from the wash oil stream to condense in the wash zone enough of the feed vapor to maintain the level on the slop wax collection apparatus without using any distillate as makeup to the wash zone. 
     
     
         4 . The process of  claim 1 , wherein a liquid collection apparatus is provided above the wash zone to collect downflowing liquid and an insulating material is applied to the liquid collection apparatus above the wash zone to reduce condensation on the lower surface of the collection apparatus of feed vapor rising from the wash zone, thereby increasing the fraction of feed vapor that passes through the collection apparatus to be condensed and yielded as distillate product. 
     
     
         5 . The process of  claim 4 , wherein the insulating material is applied to an upper surface of a floor of the liquid collection apparatus. 
     
     
         6 . A process for improving quality and yield of one or more distillate products drawn from a distillation column whose feed stream is a mixture of vapor and a liquid containing one or more components that are substantially non-volatile at column conditions, the distillation column comprising a feed zone, a wash zone located above the feed zone having disposed therein a liquid/vapor contacting structure and above it a wash oil distributor for distributing wash oil to the upper surface of the contacting structure, and means above the wash zone to remove vapor product or liquid condensed therefrom, the process comprising:
 collecting liquid slop wax falling from the wash zone contacting structure by means of a collection apparatus disposed below the wash zone and above the feed zone;   withdrawing the collected slop wax from the collection apparatus to a slop wax pump;   conducting at least a portion of the withdrawn slop wax to the wash oil distributor at a rate sufficient to assure thorough wetting of the wash oil zone liquid/vapor contacting structure and to substantially eliminate entrained liquid or solid particles from the vapor rising from the wash zone; and   removing enough heat from the recirculated slop wax to condense in the wash zone enough of the feed vapor to maintain a liquid level on the slop wax collection apparatus.   
     
     
         7 . The process of  claim 6 , wherein the vapor product rising from the wash zone is substantially free of entrained non-volatile material and the wash zone irrigated by wash oil comprising only recirculated slop wax plus the liquid condensed in the wash zone from the feed vapor comprises the sole means of removing entrained liquid or solids from the vapor rising from the feed zone. 
     
     
         8 . The process of  claim 6 , wherein a liquid collection apparatus is provided above the wash zone to collect downflowing liquid and an insulating material is applied to the collection apparatus to reduce condensation on the lower surface of the collection apparatus of the vapor product rising from the wash zone, thereby increasing the fraction of feed vapor that passes through said collection apparatus to be yielded as distillate product essentially free of entrained contaminants. 
     
     
         9 . The process of  claim 8 , wherein the insulating material is applied to an upper surface of a floor of the collection apparatus. 
     
     
         10 . A process for reducing the amount of clean wash liquid required to effectively eliminate from a vapor stream entrained liquid or solid material and the amount of contaminated wash liquid produced from a columnar liquid/vapor contacting device whose feed stream is a mixture of vapor and a liquid or solid containing one or more components that are substantially non-volatile at column conditions and which would be deleterious to the vapor product or liquid condensed therefrom, where at least one of the objectives of the column is to remove the entrained phase from the vapor rising from the feed zone, the column comprising a feed zone, a wash zone located above the feed zone having disposed therein a liquid/vapor contacting structure and above it a wash liquid distributor for distributing wash liquid to the upper surface of the contacting structure, and above the wash liquid distributor, a means for removing the vapor or liquid condensed from same, the process comprising:
 collecting liquid falling from the wash zone contacting structure, containing material previously entrained in the rising vapor, by means of a liquid collection apparatus disposed below the wash zone and above the feed zone;   withdrawing the wash zone liquid from said collection apparatus to a wash liquid pump;   conducting at least a portion of the wash liquid pump discharge liquid to the wash liquid distributor at a rate sufficient to substantially eliminate entrained liquid or solid particles from the vapor rising from the wash zone,
 wherein substantially all entrained non-volatile material is effectively eliminated from the rising vapor and concentrated in the wash zone withdrawn liquid, and 
 wherein the wash zone irrigated by wash liquid comprising recirculated wash zone outlet liquid comprises the sole means of removing entrained liquid or solids from the vapor rising from the feed zone. 
   
     
     
         11 . The process of  claim 10 , wherein a portion of the withdrawn wash zone liquid is removed from the columnar liquid/vapor contacting device to carry the captured entrained material to an external destination. 
     
     
         12 . The process of  claim 10 , wherein at least a portion of the recirculated wash zone outlet liquid is filtered to remove solids and the filtrate is passed to the wash liquid distributor.