Coating to reduce coking and assist with decoking in transfer line heat exchanger

Abstract

Coke formation in pyrolysis furnaces is controlled by applying a coating of boron nitride to pyrolysis furnace process equipment surfaces, for instance, parts of the transfer line heat exchanger assembly.

What is claimed is: 
     
         1 . A method of controlling coke formation in pyrolysis furnace process equipment, comprising:
 coating a surface of the process equipment with a layer of boron nitride to form a coated surface.   
     
     
         2 . The method of  claim 1 , wherein the boron nitride is comprised of hexagonal crystals. 
     
     
         3 . The method of  claim 2 , wherein the boron nitride has an oxidation threshold of about 850° C. in an oxidizing atmosphere and about 2000° C. in a reducing atmosphere. 
     
     
         4 . The method of  claim 1  wherein the process equipment comprises a transfer line heat exchanger tube sheet. 
     
     
         5 . The method of  claim 4  wherein the process equipment further comprises an inlet cone refractory of the transfer line heat exchanger. 
     
     
         6 . The method of  claim 5 , wherein the thickness of the coated surface is between about 25 microns to about 100 microns. 
     
     
         7 . The method of  claim 6 , wherein the thickness of the coated surface is between about 40 and about 60 microns. 
     
     
         8 . A method of controlling coke formation in a transfer line heat exchanger, comprising:
 forming a boron nitride paint by combining dry boron nitride powder with distilled water, and;   applying the boron nitride paint to a surface of a transfer line heat exchanger tube sheet.   
     
     
         9 . The method of  claim 8  further comprising applying the boron nitride paint to a surface of a transfer line heat exchange inlet refractory cone. 
     
     
         10 . The method of  claim 8  further comprising prior to the step of applying the boron nitride paint:
 roughening the surface of the transfer line heat exchanger tube sheet. 
 
     
     
         11 . The method of  claim 8  further comprising prior to the step of applying the boron nitride paint:
 hydroblasting the surface of the tubesheet of the transfer line heat exchanger; and 
 drying the surface of the tubesheet of the transfer line heat exchanger. 
 
     
     
         12 . The method of  claim 8 , wherein the step of applying the boron nitride paint further comprises applying a first coat of boron nitride paint. 
     
     
         13 . The method of  claim 12 , wherein the step of applying the boron nitride paint further comprises applying a second coat of boron nitride paint. 
     
     
         14 . The method of  claim 13 , wherein the step of applying the boron nitride paint further comprises, prior to the step of applying a second coat of boron nitride paint, drying the boron nitride paint. 
     
     
         15 . The method of  claim 14 , wherein the step of applying the boron nitride paint further comprises, after the step of applying the second coat of boron nitride paint, curing the boron nitride paint. 
     
     
         16 . The method of  claim 15 , wherein the boron nitride paint is cured for between 60 and 120 minutes. 
     
     
         17 . A boron nitride paint for coating the surfaces of pyrolysis furnace process equipment comprising:
 providing a dry boron nitride powder, wherein the dry boron nitride powder comprises boron nitride with a hexagonal crystalline structure;   providing distilled water; and   mixing the boron nitride powder with the distilled water to form the boron nitride paint, wherein the boron nitride paint comprises between 20 and 40% boron nitride by weight.   
     
     
         18 . The boron nitride paint of  claim 17 , wherein the boron nitride paint comprises between 20 and 35% boron nitride by weight.