Process and apparatus for reducing thermal shock in a hydrocarbon steam cracking furnace

Patent metadata

Field	Value
Publication number	US-10669487-B2
Application number	US-201816194086-A
Country	US
Kind code	B2
Filing date	Nov 16, 2018
Priority date	Sep 21, 2015
Publication date	Jun 2, 2020
Grant date	Jun 2, 2020

Abstract

A method and apparatus of reducing thermal shock in one or more radiant tubes of a pyrolysis furnace is provided. The apparatus is a furnace comprising a blower and blower bypass conduit providing separate fluid communication paths for flue gas from the convection section to a natural draft flue gas stack. The method comprises the steps of: redirecting at least a portion of the flue gas through the blower bypass conduit when a blower shut-off event is indicated as well as reducing the firing rate of the furnace.

First claim

What is claimed is:

1. A furnace, comprising:
(a) a plurality of hydrocarbon feed conduits;
(b) a plurality of dilution steam conduits in fluid communication with their corresponding hydrocarbon feed conduits;
(c) a plurality of radiant tubes in fluid communication with the corresponding combined steam and hydrocarbon feed conduits;
(d) a firebox comprising a plurality of burners generating flue gas for heating the exterior of the radiant tubes to provide a cracked hydrocarbon effluent from the radiant tubes;
(e) a convection section comprising the plurality of radiant tubes and is in fluid communication with the firebox for heating the hydrocarbon feed and steam conduits with flue gas;
(f) a flue gas stack, a blower, and a blower bypass conduit, wherein the blower and the blower bypass conduit provide separate fluid communication paths for flue gas to flow from the convection section to the flue gas stack;
(g) a first damper adapted to control flow of flue gas through the blower and a second damper adapted to control flow of flue gas through the blower bypass conduit;
(h) a partial trip valve configured to reduce flue gas generation in one or more of the plurality of burners;
(i) at least one sensor configured to detect a parameter indicative of a blower shut-off event; and
(j) a controller in communication with the sensor configured to perform the following steps when the sensor indicates a blower shut-off event,
a. close the first damper to reduce flow of flue gas through the blower,
b. open the second damper to direct at least a portion of the flue gas through the blower bypass conduit, and
c. close the partial trip valve to reduce flue gas generation.

2. The furnace of claim 1 , wherein the flue gas stack is from 5 to 65 m tall measured from the end of the convection section to the top of the flue gas stack.

3. The furnace of claim 1 , wherein the flue gas stack ≥30 m tall measured from the end of the convection section to the top of the flue gas stack.

4. The furnace of claim 1 , wherein the blower bypass conduit is a portion of the flue gas stack.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Spicer David
• Le Roy Philippe J
• Stephens George

Classifications

• F23N5/245

  using electrical or electromechanical means · CPC title

• F23J2213/70

  Safety arrangements · CPC title

• C10G2300/1044

  Heavy gasoline or naphtha having a boiling range of about 100 - 180 °C · CPC title

• C10G2400/20

  C2-C4 olefins · CPC title

• C10G2300/1081

  Alkanes · CPC title