Patent ID: 8916030
Filing Date: 2014-12-23
Classification: C07C,C10G

Abstract:
1. An ethylene cracking furnace comprising a high pressure steam drum, a convection section, a radiant section, multiple groups of radiant coils arranged vertically in the firebox of the radiation section, burners and transfer line exchangers, each radiant coil comprising a first-pass tube, a second-pass tube and a connection member for connecting the first-pass tube and the second-pass tube; feedstocks being introduced into an inlet end of the first-pass tube and outflow from an outlet end of the second-pass tube; characterized in that: said first-pass tube and said second-pass tube are non-split radiant tubes, and the centerlines of the respective furnace tubes are within a common plane; said connection member is a tridimensional structural member comprising an inlet bending tube, a return bending tube and an outlet bending tube; each first-pass tube is connected to an end of an inlet bending tube at the bottom end of the first-pass tube distal to the inlet end thereof, another end of the inlet bending tube is connected to an end of a return bending tube, another end of the return bending tube is connected to an end of an outlet bending tube, and another end of the outlet bending tube is connected to the bottom end of a second-pass tube that is distal to the outlet end thereof; said inlet bending tubes and said outlet bending tubes are arranged at two sides of the plane containing the centerlines of said first-pass tubes and said second-pass tubes, respectively; a plane formed by the centerlines of a group of inlet bending tubes intersects with a plane formed by the centerlines of a group of outlet bending tubes, the intersecting line is within the plane containing the centerlines of said first-pass tubes and said second-pass tubes, and said two planes formed by the centerlines of the inlet bending tubes and the outlet bending tubes are symmetrical with respect to the plane containing the centerlines of said first-pass tubes and said second-pass tubes; the return bending tubes connecting the group of inlet bending tubes and the group of outlet bending tubes are parallel to each other, and their projections in a top view are straight lines with the same length; the projections of the respective connection members in a side view are the same curve line that is symmetrical, continuous and closed, and the inner diameters of said radiant coils are selected from a group consisting of: (1) the inner diameter of said first-pass tube equals to the inner diameter of said connection member, the inner diameter of said second-pass tube differs from the inner diameter of said first-pass tube and said connection member, the inner diameter of said second-pass tube is larger than inner diameter of said first-pass tube and said connection member; (2) the inner diameter of said first-pass tube equals to the inner diameter of said connection member, the inner diameter of the lower portion of said second-pass tube equals to the inner diameter of said first-pass tube and said connection member, the inner diameter of the upper portion of said second-pass tube is larger than the inner diameter of the lower portion thereof; (3) the inner diameter of said first-pass tube is even, the inner diameter of said connection member is larger than the inner diameter of said first-pass tube, the inner diameter of said second-pass tube equals to the inner diameter of said connection member; (4) the inner diameter of said first-pass tube is even, the inner diameter of said connection member is larger than the inner diameter of said first-pass tube, the inner diameter of the lower portion of said second-pass tube equals to the inner diameter of said connection member, the inner diameter of the upper portion of said second-pass tube is larger than the inner diameter of the lower portion thereof; (5) the inner diameter of said first-pass tube is even, the inner diameter of said connection member is larger than the inner diameter of said first-pass tube, the inner diameter of the lower portion of said second-pass tube is larger than the inner diameter of said connection member, the inner diameter of the upper portion of said second-pass tube is larger than the inner diameter of the lower portion thereof; and (6) the inner diameter of said first-pass tube is variational: the inner diameter of the lower portion of said first-pass tube is larger than the inner diameter of the upper portion thereof.