Process and Apparatus for Decoking a Hydrocarbon Steam Cracking Furnace

Patent metadata

Field	Value
Publication number	US-2016168478-A1
Application number	US-201514821451-A
Country	US
Kind code	A1
Filing date	Aug 7, 2015
Priority date	Aug 28, 2014
Publication date	Jun 16, 2016
Grant date	—

Abstract

A process for the decoking of a hydrocarbon steam cracking furnace having a firebox, radiant coils, a transfer line exchanger, and an oil quench connection wherein liquid quench oil is injected to directly cool the steam-cracked effluent. Decoking feed comprising steam and air is supplied to the furnace under conditions sufficient to at least partially combust coke accumulated on the interior of the radiant coils, the transfer line exchanger, and the quench connection. Quench steam is supplied and injected into the decoking process effluent in an amount sufficient to cool the decoking process effluent below the metallurgical temperature limit of downstream piping. Also, a pyrolysis furnace for the production of ethylene is also provided.

First claim

What is claimed is:

1 . A decoking process for removing coke formed during steam cracking of a hydrocarbon feed in a furnace having a firebox, radiant coils, a transfer line exchanger, and an oil quench connection wherein liquid quench oil is injected to directly cool the steam-cracked hydrocarbon, the process comprising the steps of:
(a) stopping the flow of hydrocarbon feed to the furnace; (b) stopping the flow of quench oil to the oil quench connection; (c) supplying a decoking feed comprising steam and air to the furnace under conditions sufficient to at least partially combust coke accumulated on the interior of the radiant coils, the transfer line exchanger, and the quench connection; and (d) supplying quench steam injected into the decoking process effluent in an amount sufficient to cool the decoking process effluent below the metallurgical temperature limit of downstream piping.

2 . The process of claim 1 , wherein the decoking process effluent is substantially free of liquid water.

3 . The process of claim 1 , wherein at least a portion of the quench steam is injected at the oil quench connection.

4 . The process of claim 1 , wherein at least a portion of the quench steam is injected downstream of the quench connection.

5 . The process of claim 1 , further comprising the preliminary step of adding liquid water to the quench steam in an amount to substantially desuperheat the quench steam.

6 . The process of claim 1 , further comprising the preliminary step of adding liquid water to the quench steam in an amount sufficient to maintain the quench steam about 3.5° C. above the quench steam saturation temperature.

7 . The process of claim 1 , wherein sufficient quench steam is supplied to control the combined steam and partial combusted coke effluent temperature ≦30° C. below the metallurgical limits of downstream piping.

8 . The process of claim 1 , wherein the hydrocarbon feed in step (a) comprises a vapor stream from a vapor/liquid separator.

9 . The process of claim 1 , where the process does not include adding liquid water to the quench connection.

10 . The process of claim 1 , further comprising the step of conducting the combined steam and partial combusted coke effluent to the furnace firebox.

11 . The process of claim 1 , further comprising the step of conducting the combined steam and partial combusted coke effluent to a cyclonic decoking drum.

12 . The process of claim 1 , wherein the quench connection is a quench fitting.

13 . A pyrolysis furnace, comprising: a hydrocarbon feed conduit; a dilution steam conduit in fluid communication with the hydrocarbon feed conduit facilitating mixture of the dilution steam and the hydrocarbon feed; a radiant coil in fluid communication with the combined steam and hydrocarbon feed; a firebox for heating the exterior of the radiant coil and providing a cracked hydrocarbon effluent from the radiant coil; a transfer line exchanger in fluid communication with the radiant coil to provide indirect heat transfer for cooling the hydrocarbon effluent; an oil quench connection in fluid communication with the transfer line exchanger to provide direct heat transfer by injection of quench oil into the hydrocarbon effluent; and, a quench steam connection in fluid communication with the oil quench connection for injecting quench steam during decoking.

14 . The pyrolysis furnace of claim 13 , wherein the quench steam connection is located to inject quench steam into the oil quench connection.

15 . The pyrolysis furnace of claim 13 , wherein the quench steam connection is located to inject quench steam downstream of the oil quench connection.

16 . The pyrolysis furnace of claim 13 , further comprising a second quench steam connection in fluid communication with the oil quench connection wherein quench steam connections are located to inject steam into the oil quench connection and to inject steam downstream of the oil quench connection.

17 . The pyrolysis furnace of claim 13 , wherein the oil quench connection is an oil quench fitting.

18 . The pyrolysis furnace of claim 13 , further comprising a liquid water connection in fluid communication with the quench steam connection to desuperheat the quench steam.

Assignees

• Exxonmobil Chem Patents Inc

Inventors

• Spicer David B
• Annamalai Subramanian
• Aslaner William A

Classifications

• B08B3/00

  Cleaning by methods involving the use or presence of liquid or steam (B08B9/00 takes precedence) · CPC title

• C10G2300/807

  Steam · CPC title

• C10G2300/802

  Diluents · CPC title

• C10G9/36

  with heated gases or vapours · CPC title

• C10G9/20

  Tube furnaces · CPC title