Enhanced heat recovery in paraxylene plant
Processes and apparatuses for enhanced heat recover}/in a paraxylene manufacturing plant use a side condenser to recover high quality heat. By placing the side condenser below the location of a feed stream comprising low molecular weight gases, the heat recovered is free of such non-condensable gases. Such gases are undesirable when using the condensed vapor in other applications.
1. A process for recovering heat in a paraxylene manufacturing plant, the process comprising:
providing a first feed stream to a fractionation tower, wherein the feed stream comprises C8 aromatics;
supplying heat to a reboiler of the fractionation tower to separate the feed stream into an overhead product comprising benzene, a bottoms product comprising C9+ aromatics, a liquid sidedraw product comprising xylene recovered through a liquid sidedraw outlet and a vapor sidedraw product comprising xylenes recovered though a vapor sidedraw outlet; and
recovering heat from the vapor sidedraw product with a side condenser, wherein the vapor sidedraw outlet is located below the first feed stream.
2. The process of claim 1 , further comprising providing a second feed stream and a third feed stream to the fractionation tower.
3. The process of claim 2 , wherein the vapor sidedraw outlet is located between the second feed stream and the third feed stream.
4. The process of claim 2 , wherein the vapor sidedraw outlet is located between one and ten trays below the second feed stream.
5. The process of claim 1 wherein the heat recovered with the side condenser is at a temperature of less than 200 degrees Celsius.
6. The process of claim 1 , wherein the heat recovered with the side condenser is at a temperature of between about 190 and 210 degrees Celsius.
7. The process of claim 1 , wherein the sidedraw product comprises about 90 to about 98 percent C8 aromatics.
8. The process of claim 1 , further comprising supplying the sidedraw product to a paraxylene recovery section.
9. The process of claim 8 , wherein the paraxylene recovery section comprises a crystallization unit.
10. The process of claim 1 , further comprising condensing the vaper sidedraw product in the condenser to form a condensate.
11. The process of claim 10 wherein the condensate and the liquid sidedraw product are combined to form a combined sidedraw product.