Fis CO Boiler Brochure

Low Cost Value Added Solutions for CO Boilers

Furnace Improvement Services

Furnace Improvement Services (FIS) is a full service engineering and consulting company, having completed over 300 engineering studies and projects. FIS currently has a team of 40 skilled engineers on board with offices in Sugar Land, TX and in New Delhi, India. We have experience in design and revamp of all types of CO boilers

CO Boilers Most of the fluid catalytic cracking (FCC) units produce gases rich in carbon monoxide (CO). This gas is burnt in a CO boiler to recover heat and produce steam. The supply of CO gas is normally not sufficient to ensure destruction of CO. Supplementary fuel raises the temperature of the CO gases to the ignition point and assures the complete burn-ing of the combustibles in the CO gas stream . There are two types of CO boilers prevalent in the industry. One design has a separate combustion chamber for CO burning and is followed by a convection section for heat recovery. The other type is a water wall type boiler which is modi-fied to burn CO gas.

Our Expertise Furnace Improvements has worked on several CO Boilers in the past 15 years. Scope of Services include:

♦ Increasing Capacity

♦ Improving Boiler efficiency

♦ Eliminate flow distribution problems

♦ Tube Failure analysis

♦ CFD Modeling

♦ NOx Reduction

CO Boilers

Revamping - Training - Troubleshooting www.heatflux.com

CO Boilers

Case Study - CO Boiler Revamp

An Illinois refinery had a carbon monoxide (CO) boiler in their Fluid Catalytic Cracking (FCC) Unit. The CO boiler was more than 40 years old. The CO boiler’s convection section is used to preheat the FCC charge and also generate superheated steam at 600 psig/710°F.

The refinery approached FIS to provide thermal design for replacing the convection section of the CO boiler. Furnace Improvements carried out the engineering study for replacing the con-vection section. We conducted a detailed operation analysis of the existing CO boiler and built a model of the existing design. With the model built, we were able to simulate the current oper-ating conditions and predict the heater performance for the future operating conditions.

The convection section was redesigned to:

♦ Increase FCC feed flow rate

♦ Improve CO Boiler efficiency

♦ Prevent cold end corrosion of economizer

♦ Eliminate flow distribution problems

Savings The proposed revamp took care of all the operating issues with the existing CO boiler. It was estimated to save the client almost $550,000 per year. The boiler was commissioned in March 2003.

The new design was developed retaining the ex-isting soot blower locations, same platform eleva-tions, and without any additional firing require-ment. The detailed engineering drawings of the convection section vendor were also reviewed.

Item Units Before Revamp After Revamp

Heat Duty Total MMBtu/hr 182.45 220.83

Process Heat Duty MMBtu/hr 81.55 104.91

Process Flow BPD 41,995 48,000

Process ∆T °F 674 - 459 694 – 459 Steam Heat Duty MMBtu/hr 100.90 115.92

Steam Flow lb/hr 155,170 190,000

Steam Outlet Temp. °F 765 714

Economizer TMT °F 301 318

Stack Temp. °F 636 577

Efficiency % 68.0 72.6

Fuel Savings $ / annum 0.55 Million*

* Based on $3.0 / MM Btu


The boiler had three main problems:

♦ low economizer tube metal temperatures were reaching dew point levels

♦ high super heated steam temperature

♦ problems with tube supports in the hottest zones

CO Boilers

Case Study Results FIS conducted a study and provided the client with various options for NOx reduction. Conoco-Phillips selected the option of Ultra Low NOx Burners with flue gas recirculation for detail en-gineering. FIS’ scope of services was comprised of the following:

The project was completed and commissioned successfully in December 2007 by FIS

Case Study - NOx Reduction

A Texas refinery’s CO boiler was originally designed to generate 450,000 lb/hr steam @ 600 psig / 750°F by firing a combination of CO gas and refinery fuel gas.

Furnace Improvements (FIS) was approached to convert the CO boiler to a refinery fuel gas fired boiler only and reduce the NOx emissions to 0.02 lb/MMBtu (15 ppm).


♦ Ultra Low NOx Burners with steam injection ♦ Flue gas Recirculation ♦ New economizer to increase the efficiency by 3% ♦ Design of additional rows of super heater coil ♦ Remove CO burners from firebox and seal the CO ports with additional heat transfer

surface ♦ Computational fluid dynamics (CFD) modeling of the existing and new burners to pre-

dict the combustion scenario

CO Boilers

FIS proposed modifications to the combustion chamber and verified the modifications with the CFD. As shown in figure 2, CO is burned completely compared to the existing case. The flue gas temperature pattern inside the combustion chamber is uniform compared to the existing case.

Case Study - CO Slippage

ConocoPhillips Wood River Refinery has a CO heater (CCU-1) in their FCC unit. It is used to combust the FCC off gas (mainly CO gas) from the spent catalyst regenerator unit. The hot flue gases generated from combustion of FCC off gas are used to preheat the oil and generate super heated steam @ 600 psig / 700ºF. ConocoPhillips was installing a new SCR unit downstream of the CO Heater as a part of the consent decree agreement to reduce the NOx emissions. The new SCR requires a flue gas inlet temperature in the range of 680-700 °F, which required reconfiguring the heat transfer surface in the convection section. FIS modeled the convection section for 5 proposed cases and provided a revised design. FIS developed a CFD model of the existing combustion chamber and found out that mixing of FCC off gas and air was very poor in the combustion chamber leading to incomplete combustion in the firebox and post combustion in the convection section. FIS also found out that the burners were oversized and they were operating at a very low fuel gas pressure.

Contour of Temperature Distribution Contour of CO Mass Fraction

FIG. 1 FIG. 2

CFD Models


Case Study Cont.

CO Boilers

FIS proposed modifications to the CO plenum, the misdistribution is calculated via CFD model. As shown in figure 3, the proposed modification ensured uniform distribution of FCC off gas to all the burners. This coupled with the modifications made to the combustion chamber ensured complete combustion of CO gas and reduced the CO emissions.

After FIS developed a CFD model of the proposed design and the model suggested a marked improvement in the combustion of CO. Some of the modifications FIS suggested are as fol-lows:

The CFD model predicted the following: ♦ Mixing of the FCC off gas and air in the combustion chamber is very poor. The CO enter-

ing the chamber sweeps along the floor and exit, which results in incomplete combustion of CO. The flue gas temperature distribution is not uniform.

♦ FIS observed misdistribution of FCC off gas to the nine burners.

FIG.3


♦ Install correct size burners

♦ Install a baffle wall in the combustion chamber

♦ Inject FCC off gas in the flame zone.

♦ Increase the air velocity through over fire air port

All modifications to CO Heater (CCU-1) have been completed and it has been in operation since February 2008.

CO Boilers

Project Reference List

Mobil - (FIS 152)

Location: Beaumont, TX

Scope of Work: Rating of a CO Boiler

ConocoPhillips - (FIS 188)

Location: Roxana, IL

Scope of Work: Performance improvement study on CO Heater Convection Section

Citgo - (FIS 207)

Location: Corpus Christi, TX

Scope Of Work: Performance Improvement Study for CO Boiler

Citgo - (FIS 214)


Scope Of Work: CO Boiler Burner Inspection



Scope Of Work: CFD Modeling of BFW Dis-tribution in CO Boiler Economizer Coils


Location: Borger,TX

Scope Of Work: Design, Engineering and supply and erection services for conversion of

Unit No. 40 CO Boiler to Fuel Gas Fired Boiler.

Citgo - (FIS 267)


Scope Of Work: CO Boiler Re-rating report as a Flue gas cooler



Scope Of Work: CO Boiler Engineering Study, Tuning and CFD modeling



Scope Of Work: CCU -2 CO Boiler H -2 Modification Re-rating study

Citgo - (FIS 349)

Location: Lemont, IL

Scope Of Work: Engineering Study for in-creasing steam production in CO Boiler


Our Clients We have an Agent near You.

Furnace Improvements Services Inc. 1600 Highway 6 South, Suite 480 Sugar Land, Texas 77478 USA

Tel: (281) 980-0325 Fax: (1877) 395-0760

A.G. Furnace Improvements Pvt. Ltd. K-33, Ground Floor

Opp. Balaji Estate, Kalkaji New Delhi, India 110019

Tel: 91-11-405-8-8696 Email: [email protected]

www.heatflux.com

Low Cost Value Added Solutions for Fired Heaters

AUSTRALIA, SINGAPORE, NEWZEALAND, INDONESIA & MALAYSIA Kate Gimblett Tel: +61 (0) 7 5435 2205 Mobile: +61 (0) 417 087 129 [email protected]

TAIWAN Douglas Chang Tel: +8862-2706-1544 Mobile: +8869-2106-9827 [email protected]

BRAZIL Jose Fleischmann Tel: (+55) 11-5641-4361 Fax: (+55) 11-5641-4361 [email protected]

CALIFORNIA, USA David P. Diggins Tel: +94-9497-6551 Mobile:+94-9463-8591 [email protected]

CANADA Paul Henry Tel: +450-676-3222 Fax: +450-676-5997 [email protected]

VENEZUELA, COLUMBIA, ARGENTINA & ARUBA Carlos Alarcon Tel: +58-441-6609-3444 Fax: +58-441-4366-8406 [email protected]

INDIA Vijay Thiruvady Tel: 080-25530671 Tel: 080-25521125 [email protected]

INDIA R. Rajamani Tel: + 91 94483 79108 Tel: +91 80 65971113 [email protected]

INDIA Ajai Agarwal Tel: +9111-4214-3751 Mobile:+9198-1015-9901 [email protected]

LOUISIANA, USA Charles H. Thatcher Tel: 985-892-4224 Mobile: 985-966-5513 [email protected]

MEXICO Jorge Ruiz Silva Cel: 1+52 55 54 62 04 09 [email protected]

SOUTHEAST, USA David Gangle Tel: +20-5437-1702 Mobile:+20-5542-7006 [email protected]

KUWAIT Alex Ambi Tel: +965-2482-9160 ext.126 Mobile: +965-3384-1712 [email protected]

TEXAS, USA Stan McHugh Tel: +713-839-8788 Mobile:+713-703-8907 [email protected]

UTAH, MONTANA, NEVADA, IDAHO, WYOMING; Allan Woodbury Tel: +801-274-3333 Mobile: +801 918-4826 [email protected]

Fis CO Boiler Brochure

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