Method for calcining delayed coke

Claim 1

A process for calcining delayed petroleum coke in an internally-fired vertical shaft kiln comprising: (a) feeding particulate green delayed petroleum coke at a rate of from 0.5 to 2.5 tons per day per square foot of kiln cross section into the top of a vertical shaft kiln to form a downwardly-moving bed of material to be calcined; (b) introducing combustion air in an amount of from 20 to 60 mols per ton of dry green coke feed into an intermediate level of said kiln to provide a combustion zone and to generate heat by internal burning; (c) recovering an off gas stream comprised of internally-generated flue gas and volatile material released from said coke from the upper section of said kiln, the temperature of said off gas being from 300° to 1100° F.; (d) introducing recycle gas comprising a portion of said off gas stream in an amount of from 80 to 120 mols per ton of dry green coke feed into the lower section of said kiln for upward movement therethrough for recovering heat from coke below the combustion zone and for returning said heat to coke in and above the combustion zone; (e) controlling the rates of recycle gas introduction, combustion air introduction and green coke feed to provide a calcining temperature of at least 2000° F. for a period of at least one hour for the coke moving therethrough and to maintain the temperature of the off gas leaving said kiln above its hydrocarbon dew point; and (f) recovering partially cooled calcined coke from the bottom of said kiln.