Cracking furnace for producing ethylene by cracking hydrocarbon steam

Abstract

The invention discloses a cracking furnace for producing ethylene by cracking hydrocarbon steam. The cracking furnace is characterized in that a radiant coil is a two-stage branched and diameter-altered radiant tube; a plurality of first-stage tubes are combined into one tube in an inverted Y-shaped tube form at the lower end of the second-stage tube; and the first-stage tubes are connected with the second-stage tube through a three-dimensional structural connector formed by symmetric curved tubes and S-shaped curved tubes. The invention has the following beneficial effects: the mechanical property defects of a 2-1 type branched tube, a 4-1 type branched tube and the like are overcome; and the technological properties can be improved, and the service life of the radiant coil and the operational cycle of the cracking furnace can be prolonged finally.

Description

technical field [0001] The invention belongs to the field of petrochemical industry, and in particular relates to a radiation furnace tube structure of an ethylene cracking furnace in petrochemical production. Background technique [0002] The ethylene cracking technologies used in petrochemical ethylene units are mainly American LUMMUS, Stone & Webster, Kellog & Braun Root, European German Linde, Technip (KTI) and domestically developed CBL cracking furnaces. Their techniques are as follows: [0003] LUMMUS company in the United States: use 4-1, 5-1, 6-1 and other two-pass furnace tubes, usually four small groups of furnace tubes are equipped with a quenching (waste heat) boiler; [0004] Stone&Webster Company of the United States: U-shaped furnace tubes are used, usually a small or two small groups of furnace tubes are equipped with a linear quenching (waste heat) boiler, and all bottom heating is provided; [0005] Kellog & Braun Root Company in the United States: U-sha...

AI Technical Summary

Problems solved by technology

[0011] The 1-1 type (U-shaped) furnace tube has a large specific surface area, can match with the linear quenching boiler, and has good mechanical properties, but the operation cycle is slightly worse than other two-pass furnace tubes

[0012] The 2-1 type furnace tube has a large specific surface area and can match the linear quenching boiler. However, compared with the 1-1 type (U-shaped) furnace tube, the first-pass tube needs to be combined into one by a Y-shaped piece. The root pipe, the two pipes will be deviated during manufacture and operation, the diameter of the merged furnace pipe is larger, and the flexibility of the large-diameter bend is worse than that of the small bend

With this kind of structure, since there are multiple first-pass tubes and one second-pass tube, when the furnace tube is heated and expanded, the second-pass tube expands downward first, and the first-pass tube is pulled downward by the second-pass tube. Downward movement, where the force farther away from the second-pass tube is smaller, and the force near the second-pass tube is larger. In addition, the lower collecting tube is rigidly connected, and the expansion difference between the second-pass tube and the first-pass tube It can only be adjusted by the balance system installed at the inlet of the first pass tube. As a result, when the first pass tube cannot move with the second pass tube, it will cause the furnace tube to bend

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