Sustainable Burner Design

Motivation

(why energy?)

August 2003 Blackout

(You were 3.  I was in grad school.)

It started here in Ohio.

1-5 days. 55 million people. ~$6 billion.

×3

Hot day.

Sagging lines fault to ground, causing load shedding.

Bad luck. 3 places. Cascading failure.

August 2005 — Katrina

  • 95% of US oil production offline
  • 30 million barrels (4%) strategic oil reserve released to smooth price
  • Natural gas spot price doubles (we don't really have reserves)

$13.42 / MMBTU

(avg. house: 100 MMBTU/yr)

The need for workable energy options is perhaps the greatest single challenge facing our nation and the world in the 21st century.

- MIT Energy Research Council

   July 2006

I graduate 2006

  • About 250 people.
  • Formed after the oil crisis.
    (Was 3× bigger in the 70's-80's.)
  • Serves the natural gas industry at all points
    in the value chain.
  • Members + Govt. + Industry pay for our research.

+ join the Gas Technology Institute

Industrial Process Heat

burner design for industry

Engineering design PSA

  • Know the Principles.
  • Understand the Situation.
  • Apply the Principles to the Situation.

Principles + Situation, Applied.

PSA.   

Principles:  Combustion Triangle

The combustion triangle names the necessary things for combustion.

Oxidizer

Fuel

Heat
(ignition)

Fuel + Oxidizer → Heat + combustion products  

+ ignition

(feedback)

Fuel + Oxidizer → Heat + combustion products

Principles: Methane Combustion

Usually air
(~ 78% N2 + 21% O2 + other stuff)

Usually natural gas
( > 96% CH4 + other stuff)

Chemical formula:

CH4  +   2O2    →  Heat  +  CO2  +  2H2O  

Principles: Methane Combustion

Ideal gas law:   Pressure  Number of Moles if T constant

CH4  +  2 O2  →  Heat  +  CO2  +  2 H2O  

Natural Gas

+  9.7 Air →  Heat  +  CO2  +  2 H2O  + 7.6 N2 +

(~ 21% O2 )

( ~ 100% CH4)

other stuff

P V = N R T
PV=NRTP V = N R T

1 natural gas + 10 air → 11 exhaust + heat

Principles: Methane Combustion

  • Combustion triangle: air + fuel + heat = flame.
     
  • Ratio of air:fuel for natural gas is about 10:1.
     
  • The theoretical maximum flame temperature of methane + air is about 3500°F.

Things we can vary

  • Combustion triangle: air + fuel + heat = flame.
    • More air  ⇒  cooler

    • More heat  ⇒  hotter
       
  • The theoretical maximum flame temperature of methane + air is about 3500°F.

CH4  +  9.7 Air →  Heat  +  CO2  +  2 H2O  + 7.6 N2 + stuff

  • Why not ditch the N2?

=

2 O2 + 7.6 N2 + stuff

That's because the flame has to heat up all this.

Situation: Glass + Oxy-Fuel burners

  • Glass melts at ~ 2850°F. Expensive heat recovery systems were needed until the 1990's when oxy-fuel burners were invented.
     
  • See how small the oxidizer
    line is relative to the gas line.

CH4

2O2

(source: DOE)

prototype burner in a GTI test furnace

  • Also the oxygen lance.
    (enhances luminosity)

Principles: Heat Transfer

 blowdryer

waffle iron

the sun

Heat convected by moving fluid.

Heat conducted by something hot.

Heat radiated by glowing (extends beyond visible light).

 Convection

Conduction

Radiation

Only three ways to get heat to the load.

Ideas?

Principles: Heat Transfer

Eclipse thermal radiation burners.

(Possible use: industrial cooking.)

Eclipse high velocity nozzle mix burner.

(Possible use: steel reheat.)

Example burners

 Convection

Radiation

Things we can vary

  • Heat transfer: conduction / convection / radiation
    • Brighter flame  ⇒  more radiative transfer

    • Better circulation  ⇒  more convective transfer

    • Longer residence time  ⇒  more conductive transfer

source: John Wagner's report on oscillting combustion (PDF) for the Department of Energy

Principles for efficient design

  • Recapture heat from combustion:
    • Increase residence time of the hot gases.

    • Use exhaust to heat things as much as possible.
       

  • Direct flame impingement, where practical:
    • Nothing beats blowing the fire directly on something.
    • (Unless that something needs even heating.)
       
  • Designers can adjust furnace shape and burner position for the best convective and radiative heat transfer.
     
  • Flame temperature is often much higher than process temperature, meaning design+recapture can go a long way.

Types of burners

(that our team has worked on)

All shapes and sizes: for cooking, chemicals, melting, boiling...

Flame shooting out the sides!
Wasted heat...

Situation: Wok burners

  • Restaurant margins are razor thin (3-5%).
     
  • It's 2007. Gas prices are still very high.
     
  • Our commercial / food service burner expert is approached by a chain to reduce their energy cost.

Existing design: Deep brick-lined well to absorb and radiate heat. Nice.

Situation: Wok burners

Existing design:

Little nozzles are like tiny blowtorches that blast a ton of energy into the wok. You do not need this much energy to cook food, so it will be wasted.

Principles: Wok burners

  • We are cooking chicken, not
    melting steel:
    infrared heat

    is just fine.
     
  • Angled walls reflect
    more heat up to the wok.
     
  • Slower inlet velocity ⇒ longer residence time.
    The exhaust lingers instead of shooting out, adding more heat.

Wok burner performance

More than double the efficiency of existing burners:
​this should use about half the fuel.

Situation: Glass melter

  • Burners fire over a pool of molten glass
  • Lifespan is about 20 years, afterward left with a lake of solid glass.

Principles: Glass melter

  • Because the outlet is at the bottom, you can empty the whole thing.
     
  • Direct flame impingement tons of conductive + convective heat transfer.
    (Enough to allow air
    feed instead of O2.)

     
  • Bonus: the temperature
    drop in the glass is sharp and
    swift enough to prevent NOx
    formation when using air.

Glass melter performance

  • 5-7% fuel savings when using oxy-fired combustion.
  • Up to 23% fuel savings when using air-fired combustion.

Situation: Boiler heat recovery

DOE challenge for efficiency led to a 2008 Chicago Innovation Award for the boiler team and Cleaver-Brooks.

Low pressure exhaust

Transport membrane condenser

Humidifying air heater

High pressure exhaust

GTI's new invention

Situation: The boiler design

In a fire tube boiler you combust in the big hole and the exhaust travels through the little tubes to give it time to boil the water.

Extruded aluminum inserts in the fire tubes - for heat transfer like in a car radiator.

Boiler cross section.

Principles: Boiler design

  • We are boiling water, not melting steel. So like with the wok, even under pressure, we don't need super high temperatures.
     
  • Recirculation ⇒ more
    residence time
    *.
    (more heat transfer)



     
  • Staged combustion
    lower
    maximum temperature.
    (less NOx)

*Dimensions for a design like this must be calculated using CFD.

Situation: Heat recovery (prior art)

All drawings from U.S. patent 7066396 (2004)

  • There is one water loop.
     
  • The steam loop (orange) circulates hot steam to the downstream process.
     
  • The air is piped through the exhaust to recover some of the leftover combustion heat.
     
  • The air + fuel (clear) pass through the system and out the flue.

Situation: Heat recovery (prior art)

All drawings from U.S. patent 7066396 (2004)

  • There are two water loops.
     
  • The steam loop (orange) circulates hot steam to the downstream process.
     
  • The condensate loop (purple) condenses out steam from the combustion exhaust, using it to humidify the incoming air.
     
  • The air + fuel (clear) pass through the system and out the flue.

Principles: Heat recovery (new idea)

All drawings from U.S. patent 7066396 (2004)

  • There are two water loops.
     
  • The steam loop (orange) circulates hot steam to the downstream process.
     
  • The condensate loop (purple) collects steam from the exhaust via the membrane.  It contributes make-up steam* and humidifies the air.
     
  • The air + fuel (clear) pass through the system and out the flue.

*condensate could not be used in make-up steam until now because it was not pure H2O and would gunk up the process.

Photos of the membrane bundle

First generation

Second generation

A membrane is a surface with micropores. Exhaust flows through these bundles, and the water molecules pass through the micropores in the walls to enter the condensate loop.

Superboiler performance

Data from Rick Knight's talk at the University of Texas

Principles for mid-90% efficiency

  • Heat transfer:
    • Recirculation  more residence time.
    • Humid  better heat transfer.
    • Heat recapture  more efficient.
    • New technologies (membranes)
      can squeeze more performance
      out of existing ideas
      .
    • Fins in the fire tubes
       huge surface area
      for heat transfer.
  • Combustion:
    • Staged combustion  lower peak temperatures less NOx.
    • Humidification also lowers peak flame temperatures.

+

+

=

Solar supplemented water heating

Solar heating control panel

Equinox solar-assisted tankless water heater

California Energy Commission report on solar-assisted industrial heating

California Energy Commission report on solar heating for food processors

The boiler team won a contract from California to combine the best tech for water heating. This is from a report in 2013. It was field-tested in a small winery.

Solar supplemented water heating

This is the one from the report

This one is for a boiler.

This is the test installation at GTI's facility near Chicago.
The tubes are slanted so that the water will drain out of them when not in use (to prevent burst from freezing).

Solar supplemented water heating

About 40-50°F gain in July; about 10-20°F in December.

Inlet

Outlet

Principles + situation: solar preheat

Principles

  • Using heat from the sun saves gas.
  • Combining efficient technologies (+tankless) can yield extra efficiency that's worth the cost.

Situation

  • Water heaters don't require a huge temperature gain. In your house the recommended water heater temperature is 120°F.
  • The cost of the solar installation may not be enough for a residence, but a small commercial application can benefit.

Recent developments

  • A current photo on GTI's webpage shows a more efficient solar collector that's being tested for use in natural gas power generation.
     
  • The principle,
    preheating the water,
    is the same.
     
  • The solar collector is
    different so it can
    capture more solar
    radiation.

Photo from GTI press release.

Context matters

(Things that are unrealistic in one situation could be fantastic in another.)

People use what they've got

Portable natural gas liquefaction

  • Impractical maybe for a natural gas vehicle network across the U.S.
     
  • Awesome for stranded supply (petroleum; waste plants; remote locations in South Africa / Canada / US)

Hydrogen fuel cells

  • Also likely impractical for road vehicles.
     
  • Awesome for warehouses and indoor use:
    • The exhaust is just steam.
    • Refuel time << battery charging time ⇒ they don't waste floor space charging trucks.

Why power companies efficiency

Hours spent at or below this generation level

Gigawatts

Power companies must maintain generation capacity to meet this tiny peak of demand for the few hours per year that it's needed. Shaving this peak down is financially beneficial to them.

Questions?

Try these great resources too.

  • The US Department of Energy and the Energy Information Administration. (Google for "anything site:doe.gov")
    • Planned generation
    • Existing generation
    • Monthly (sometimes daily) energy flows
    • All the newest US-funded tech
    • Historical pricing as far back as they have data
      (Henry Hub, West Texas Intermediate, average consumer prices...everything)

       
  • BP's :

Sustainable Burner Design

By Tanya Schlusser

Sustainable Burner Design

Review of engineering principles related to energy efficiency in natural gas burner design.

  • 373
Loading comments...

More from Tanya Schlusser