Method for Reducing Quench Oil Fouling in Cracking Processes

Abstract

Quench oil aging and its propensity to cause fouling may be evaluated by determining the amount of a precipitant necessary to cause the flocculation of polymer species present in the quench oil. The propensity of quench oil to cause fouling may be used as a basis to mitigate fouling in cracking processes.

1 . A method for reducing fouling from quench oil comprising: treating a hydrocarbon feed using a cracking process having a quenching step wherein:
 quench oil used in the quenching step has a known tendency to cause fouling; and   the known tendency of the quench oil to cause fouling has been determined by measuring a tendency of the quench oil to precipitate polymeric species.   
     
     
         2 . The method of  claim 1  further comprising adjusting process conditions in the cracking process based upon the tendency of quenching oil in the quenching step to cause fouling. 
     
     
         3 . The method of  claim 1  wherein the quench oil is selected from the group consisting: of crude oil; the precursors of naphthalene, phenanthrene, pyrene, quinoline, and hydroquinone; alkyl derivatives of naphthalene, phenanthrene, pyrene, quinoline, and hydroquinone; and mixtures thereof. 
     
     
         4 . The method of  claim 1  wherein the quench oil is selected from the group consisting of: steam cracked quench oils; steam cracked tars; cat cracked tars; cat cracked cycle oils; cat cracked bottoms; coker gas oils; coal tar oils; aromatic extent oils; cuts of steam cracked quench oils, steam cracked tars, cat cracked tars, cat cracked cycle oils, cat cracked bottoms, coker gas oils, coal tar oils, and aromatic extract oils; and mixtures thereof. 
     
     
         5 . The method of  claim 1  wherein the hydrocarbon feed is selected from the group consisting of: crude oil, intermediate refinery products resulting from the refining of crude oil, and mixtures thereof. 
     
     
         6 . The method of  claim 1  wherein the hydrocarbon feed is used to produce ethylene, gasoline, diesel fuel, other fuel oils, or coke. 
     
     
         7 . The method of  claim 6  wherein the hydrocarbon feed is used to produce ethylene. 
     
     
         8 . The method of  claim 1  wherein the tendency of the quench oil to precipitate polymeric species is determined by measuring light scattering. 
     
     
         9 . A method for reducing fouling from quench oil comprising: treating a hydrocarbon feed using a cracking process having a quenching step, and introducing an additive to reduce fouling to the cracking process based upon a tendency of the quench oil in the quenching step to cause fouling which is determined by measuring a tendency of the quench oil to precipitate polymeric species. 
     
     
         10 . The method of  claim 9  wherein the tendency of the quench oil to precipitate polymeric species is determined by measuring light scattering. 
     
     
         11 . The method of  claim 10  wherein differences in solubility parameters of candidate quench oils for use in a cracking process and for polymeric species present therein is measured and this measurement used as a basis for evaluating the propensity of the quench oil to undergo a polymer phase separation which may cause the deposition of foulants during a cracking process. 
     
     
         12 . The method of  claim 11  wherein the quench oil candidate is placed in a container with a probe capable of measuring light scattering properties of the quench oil. 
     
     
         13 . The method of  claim 12  further comprising introducing aliquots of a precipitant to the quench oil and measuring the light scattering properties of the quench oil. 
     
     
         14 . The method of  claim 13  wherein a quench oil candidate requiring more precipitant to increase light scattering is considered less likely to foul than a quench oil candidate requiring less precipitant. 
     
     
         15 . The method of  claim 13  wherein the precipitant is selected from the group consisting of pentane, hexane, heptane, octane, isobutane, cyclohexane, and mixtures thereof. 
     
     
         16 . The method of  claim 12  wherein the probe is a fiber optic probe. 
     
     
         17 . The method of  claim 16  wherein the fiber optic probe is selected from the group consisting of transmission probes, reflectance probes, and attenuated total reflectance probes. 
     
     
         18 . The method of  claim 17  further comprising using an automatic titrator to measure the light scattering properties of the quench oil. 
     
     
         19 . The method of  claim 9  further comprising using solvent to dilute the quench oil prior to measuring the tendency of the quench oil to precipitate polymeric species. 
     
     
         20 . The method of  claim 19  wherein the solvent is selected from the group consisting of: benzene, toluene, xylene, ethyl benzene, and mixtures thereof.