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Method and equipment for decoking hydrocarbon steam cracking furnace

A steam and furnace technology, applied in the field of low molecular weight olefins such as ethylene, can solve the problems of increasing pipeline thermal fatigue, pipeline thermal fatigue failure flanges, leakage, etc., and achieve the effect of reducing demand

Active Publication Date: 2021-02-02
EXXONMOBIL CHEM PAT INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This results in a non-uniform and varying temperature gradient around the pipe which over time can lead to thermal fatigue failure of the line and flange leaks
Additionally, the large temperature difference between the vapor and liquid streams in the line makes it more difficult to control the rate at which quench water is added to maintain a steady temperature because the temperature sensor in the line is controlled by the hot vapor or relatively cool liquid stream touch
Rapid cycling of measured temperatures results in rapid cycling of quench water addition rates, which further increases thermal fatigue of lines

Method used

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  • Method and equipment for decoking hydrocarbon steam cracking furnace
  • Method and equipment for decoking hydrocarbon steam cracking furnace
  • Method and equipment for decoking hydrocarbon steam cracking furnace

Examples

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Embodiment 1

[0042] Embodiment 1 (comparison)

[0043] In this comparative example, using as figure 1system shown. Heavy gas oil may be fed via line 10 at a rate of 91 Mg / hr (200 klb / hr). Quench oil is supplied through line 70 at a rate of 182 Mg / hr (400 klb / hr) to cool the furnace effluent. When decoking, the temperature in effluent conduit 53 can reach 580°C (1075°F). Equipment (not shown) downstream of conduit 90 may be fabricated from carbon steel and designed to operate at temperatures below 449°C (840°F). Quench water may be injected through line 80 to cool the decoking effluent. Due to stratified flow and resulting variability in the previously discussed decoke effluent temperature measurement, the target effluent temperature was 315°C (600°F) obtained with a quench water flow rate of approximately 14 Mg / hr (31 klb / hr) .

[0044] Since the direct oil quenching device 60 in the present embodiment is designed to flow the quenching oil of 182Mg / hr (400klb / hr), when only the quenc...

Embodiment 2

[0046] The same 91 Mg / hr (200 klb / hr) heavy gas oil feed used in Example 1 can be fed to a feed such as figure 2 In a similar furnace of construction as shown. Again, the direct oil quench unit 60 is designed for a quench oil flow of 182 Mg / hr (400 klb / hr). During decoking, instead of water, quench steam may be supplied through line 80 or through line 110, or both, to cool the decoking process effluent. Since the addition of quench steam does not result in stratified flow, the target effluent temperature can be raised to 427°C (800°F) (closer to the carbon steel temperature limit of 449°C (840°F)) and approximately 40Mg / hr ( 88klb / hr) quenched steam at medium pressure 188°C (370°F). The use of quench steam avoids the problems of stratification, mechanical fatigue and variable temperature control by eliminating the use of quench water.

Embodiment 3

[0048] The same 91 Mg / hr (200 klb / hr) heavy gas oil feed used in Example 1 can be fed to a feed such as image 3 In a similar furnace of construction as shown. Again, the direct oil quench unit 60 is designed for a quench oil flow of 182 Mg / hr (400 klb / hr). During decoking, instead of water, quench steam may be supplied through line 110 to cool the decoking process effluent. In order to minimize the rate of quench steam required, and thus reduce the velocity in the pipes (so as to reduce the rate of attrition), quench steam close to its saturation temperature can be used. Since the operating pressure of line 90 can be at about 0.82 atm gauge (12 psig) or less, the quench steam can be cooled to 121°C (250°F) (about 3.5°C above the quench steam saturation temperature) without adding to the Risk of adding excess water to char effluent. Use a composition consisting of approximately 1.3Mg / hr (3klb / hr) of desuperheated water (supplied through line 120) and approximately 32.7Mg / hr...

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Abstract

A decoking process for a hydrocarbon steam cracking furnace having a combustor, radiant coils, transfer line exchanger and oil quench connections, wherein liquid quench oil is injected to directly cool the steam cracked effluent. A decoking charge comprising steam and air is supplied to the furnace under conditions sufficient to at least partially burn coke accumulated on the interior of the radiant coils, transfer line exchanger, and quench connection. Quench steam is supplied and injected into the decoke process effluent in an amount sufficient to cool the decoke process effluent below the downstream pipeline metallurgical temperature limit. In addition, the invention also provides a pyrolysis furnace for ethylene production.

Description

[0001] Cross References to Related Applications [0002] This application claims the benefit of US Prior Application Serial No. 62 / 042,920 filed August 28, 2014, EP 14191533.0 filed November 3, 2014, and US Prior Application Serial No. 62 filed December 16, 2014 Priority and benefit of / 092623, which is hereby incorporated by reference in its entirety. [0003] field of invention [0004] The present invention relates to the field of thermal cracking of hydrocarbons for the production of olefins, especially low molecular weight olefins such as ethylene. More particularly, the present invention relates to methods and apparatus for removing coke deposits formed during such thermal cracking processes. [0005] Background of the invention [0006] Steam cracking, also referred to as pyrolysis, is used to crack various hydrocarbon feedstocks into olefins, preferably light olefins such as ethylene, propylene and butenes. Conventional steam cracking uses a pyrolysis furnace which, ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C10G9/16C10G9/36
CPCC10G9/16C10G9/36C10G2300/4006C10G2300/802C10G2300/807
Inventor D·B·斯派瑟S·安纳马莱J·M·弗莱
Owner EXXONMOBIL CHEM PAT INC