This website requires certain cookies to work and uses other cookies to help you have the best experience. By visiting this website, certain cookies have already been set, which you may delete and block. By closing this message or continuing to use our site, you agree to the use of cookies. Visit our updated privacy and cookie policy to learn more.
This Website Uses Cookies
By closing this message or continuing to use our site, you agree to our cookie policy. Learn More
This website requires certain cookies to work and uses other cookies to help you have the best experience. By visiting this website, certain cookies have already been set, which you may delete and block. By closing this message or continuing to use our site, you agree to the use of cookies. Visit our updated privacy and cookie policy to learn more.
Ceramic Industry logo
search
cart
  • Sign In
  • Create Account
  • Sign Out
  • My Account
Ceramic Industry logo
  • News
    • Ceramic Industry News
    • Market Trends
    • Events Calendar
  • Topics
    • Advanced Ceramics
    • Refractories
    • Glass
    • Whitewares
    • Brick and Structural Clay
    • Raw and Processed Materials
    • Firing and Drying
    • Batching and Materials Handling
    • Forming and Finishing
    • Instrumentation & Lab Equipment
    • Decorating
  • New Products
    • New Products
    • Virtual Supplier Brochures
  • Columns
    • IP in Depth
    • Glass Works
    • Ceramic Decorating
    • Taking Care of Business
  • CI Top 14
  • Multimedia
    • Videos
    • Podcasts
    • Photo Galleries
    • Mobile App
    • Webinars
  • Directories
    • Data Book & Buyers' Guide
    • Ceramic Components Directory
    • Materials Handbook
    • Equipment Digest
    • R&D Lab Equipment & Instrumentation
    • Services Directory
    • Take a Tour
  • Explore
    • CI Supplier of the Year Award
    • Blog
    • CI Store
    • Raw & Manufactured Materials Overview
    • Material Properties Charts
    • Market Research
  • Magazine
    • Current Issue
    • Digital Edition
    • Classifieds & Services Marketplace
    • Advertiser Index
  • Contact
    • Classifieds & Services Marketplace
    • Custom Content Marketing Services
Home » Kiln Connection: Burner Ratio Control
ColumnsKiln Connection

Kiln Connection: Burner Ratio Control

May 1, 2002
Ralph Ruark
Reprints
No Comments
Fuel fired kilns depend on a variety of means to control the burner air-to-fuel ratio. These systems vary considerably, but all of them require a good understanding of the concepts of flow and pressure. Over the next several columns, we’ll discuss the many systems that are commonly found on kilns for ceramic firing. This column will consider a basic ratio control system and examine the components that make it work.

The Fundamental of Flow

The flow of air and fuel gases follows standard flow laws, and the laws governing pressure and flow are straightforward. This makes the setup and control of burners simple and accurate, as long as certain rules and precautions are followed. For starters, the flow of gas and air are reflected in the formula:

Flow is proportional to (Pressure)1/2

Just knowing this simple relationship can be very helpful. For example, if you know the flow value at a given pressure, this formula allows you to readily calculate the flow at another pressure, or vice versa. As an example, if a system flow is 500 units at a pressure of 1 psig, and we increase the pressure to 4 psig, the new flow, as long as nothing else has changed, will be 1000 units, as seen below:

1000 = 500 (4/1)1/2

Normally, the units of flow are standard cubic feet per hour, which is a cubic foot of the gas volume at standard temperature (60?F) and pressure (14.7 psia). Keep this formula in mind whenever you are considering fluid flow, since it will be useful as long as the temperature of the flowing gases and the system pressures are relatively constant.

Figure 1. A proportional control system is designed to provide constant ratio control.

Proportional Control

The combustion schematic in Figure 1 is a simple arrangement that shows a proportional control system. It is designed, in its most basic form, to provide constant ratio control, i.e., a set ratio of air-to-gas regardless of firing rate. And it only works due to the flow law that we defined above. This combustion system consists of the following bits of hardware:
  • Combustion air fan. This fan delivers combustion air to the burner system at a reasonably constant pressure.
  • Motor operated air control valve. The valve modulates the flow of air to the burner.
  • Gas proportioning regulator/ratio regulator. This device is the “heart” of the system. Developed decades ago, it is still an accurate and economical means of controlling the proportion of gas to air.
  • Limiting orifice. This device introduces a pressure drop in a flow line to allow for balancing or adjusting flow rate. In laymen’s terms, it is a needle valve.
Of these components, the gas proportioning regulator bears further discussion. The regulator has an impulse line that is connected from the combustion air line to the regulator port. As the combustion air flow varies in accordance with burner input, the pressure applied to the regulator port also varies. This pushes down on the diaphragm, which opens the valve, causing more gas to flow. The increased gas flow creates a pressure rise at the outlet of the regulator, and through internal port, this pressure pushes up on the underside of the diaphragm until the gas pressure at the regulator output is just equal to the impulse pressure from the combustion air. A spring is in place to balance the weight of the diaphragm and the valve, so that the pressure of the air impulse and gas pressure are the only factors affecting the operation of the regulator.

At this point, the regulator has achieved its purpose: to create the same level of gas pressure at the regulator outlet as the impulse pressure that is applied to the regulator impulse. This remarkable device continues to be the most widely used device in fuel-to-air ratio control.

Troubleshooting this regulator is simple. Since the gas outlet pressure at the regulator should be equal to the impulse pressure, one need only connect a suitable pressure monitor at both locations and compare pressures; they should be equal.

This is just a start—there are many different regulator types, including bias, multiplication, fixed output, differential and combination sets. Next time we’ll look at the exact way that the ratio regulator proportions air-to-fuel ratio in a variety of systems.

Recent Articles by Ralph Ruark

What You Need to Know About NFPA 86-2015

Investing in Ceramics: Conrad Dressler - Artist, Inventor, Founder

Carbon - Something Old, Something New

Ahead of the Curve

Kiln Connection: A Farewell

Ralph-ruark-107px

Ralph Ruark is president of Swindell Dressler International. He was formerly president of Ruark Engineering, Inc., a company that provided analysis, recommendations and training for clients worldwide that manufacture industrial ceramics. He can be reached at (412) 788-7100 or rruark@swindelldressler.com.

Related Articles

Kiln Connection: Burner Control Systems, Part 2

Kiln Connection: Burner Control Systems, Part 3

KILN CONNECTION: Elegant Burner Concept

KILN CONNECTION: Elegant Burner Concept

Related Products

CI R&D Lab Equipment Directory

Ceramic Industry Equipment Digest

Ceramic Industry Materials Handbook

Ceramic Industry December 2018 Issue

Related Directories

L&L Kiln Mfg. Inc.

L & L Special Furnace Co. Inc.

Swindell Dressler Intl. Co.

You must login or register in order to post a comment.

Report Abusive Comment

Subscribe For Free!
  • Print & Digital Edition Subscriptions
  • eNewsletters
  • Online Registration
  • Customer Service

More Videos

Events

January 1, 2030

Webinar Sponsorship Information

For webinar sponsorship information, visit www.bnpevents.com/webinars or email webinars@bnpmedia.com.

View All Submit An Event

Products

Handbook of Advanced Ceramics Machining

Handbook of Advanced Ceramics Machining

Ceramics, with their unique properties and diverse applications, hold the potential to revolutionize many industries, including automotive and semiconductors.

See More Products

Ceramic Industry Magazine

01_CI0519Cover-144px

May 2019

What can Ceramics UK attendees expect to see? Find out in our May issue, and learn about brazing, zirconia structural ceramics, waste heat transfer, and more!

View More Create Account
  • Resources
    • Advertiser Index
    • List Rental
    • Classifieds & Services Marketplace
    • Manufacturing Group
    • Partners
    • Want More?
    • Connect
    • Privacy Policy
    • Survey And Sample

Copyright ©2019. All Rights Reserved BNP Media.

Design, CMS, Hosting & Web Development :: ePublishing