Coke and tar removal from a furnace effluent

A process for removing coke, tar, or a mixture thereof from a furnace effluent comprising:

• contacting a furnace effluent comprising coke and/or tar, with a first quench liquid to produce a partially-quenched mixture, wherein the first quench liquid comprises one or more of a first steam cracker naphtha, a first steam cracker gas oil, and a first steam cracker quench oil;
• introducing the partially-quenched mixture into a first inlet of a centrifugal separator;
• combining the partially quenched mixture in the centrifugal separator and a second quench liquid to produce a quenched mixture, the second quench liquid being introduced into a second inlet of the centrifugal separator at a second quench liquid mass flow rate, wherein the second quench liquid comprises one or more of a second steam cracker naphtha, a second steam cracker gas oil, and a second steam cracker quench oil;
• separating a vapor product and a centrifugal separator bottoms from the quenched mixture, wherein the centrifugal separator bottoms comprises at least a portion of the coke and/or at least a portion of the tar;
• recovering the centrifugal separator bottoms from a first outlet of the centrifugal separator;
• recycling at least a portion of the centrifugal separator bottoms tangentially onto a frustoconical inner wall of the centrifugal separator through a recycle inlet of the centrifugal separator;
• measuring a centrifugal separator bottoms mass flow rate at a location between the first outlet and the recycle inlet;
• and
• increasing the flow rate of the second quench liquid when the centrifugal separator bottoms mass flow rate is ≤90% of a maximum recycle rate of the centrifugal separator bottoms.

A process for upgrading a furnace effluent from a steam cracker operating in on-stream decoking mode, the process comprising:

• contacting the furnace effluent with a first quench liquid to produce a quenched mixture, wherein the first quench liquid comprises a first steam cracker naphtha, a first steam cracker gas oil, a first steam cracker quench oil, or a mixture thereof, wherein the furnace effluent is at a temperature of about 425° C. to about 850° C. and the first quench liquid is at a temperature of about 30° C. to 200° C. when the furnace effluent is contacted with the first quench liquid, and wherein the furnace effluent comprises coke, tar, or a mixture thereof;
• introducing the quenched mixture into a first inlet of a centrifugal separator drum;
• introducing a second quench liquid comprising a second steam cracker naphtha, a second steam cracker gas oil, a second steam cracker quench oil, or a mixture thereof into a second inlet of the centrifugal separator drum at a second quench liquid flow rate, wherein the centrifugal separator drum contains the quenched mixture;
• separating a vapor product and a centrifugal drum bottoms from the quenched mixture and the second quenched liquid, wherein the centrifugal drum bottoms comprises at least a portion of the coke, tar, or the mixture thereof;
• recovering the centrifugal drum bottoms from a first outlet of the centrifugal separator drum;
• introducing a recycle fluid tangentially onto a frustoconical inner wall of the centrifugal separator drum through a recycle fluid inlet of the centrifugal separator drum, wherein the recycle fluid comprises at least a portion of the centrifugal separator drum bottoms;
• measuring a centrifugal separator drum bottoms flow rate between the first outlet and the recycle fluid inlet;
• and
• increasing the flow rate of the second quench liquid when the centrifugal separator drum bottoms flow rate is ≤90% of a maximum recycle rate of the centrifugal separator drum bottoms.