methane presentation

7/29/2019 Methane Presentation

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BOILERS ANDBOILERS AND

COMBUSTION CONTROLCOMBUSTION CONTROL

Presented By:Presented By:

Ryan Thompson, P.E.Ryan Thompson, P.E.

Project ManagerProject ManagerDepartment of Utilities and Energy ManagementDepartment of Utilities and Energy Management



University of Texas at AustinUniversity of Texas at Austin¾Utility Plant supports

– 17 million square feet of facilities– 51,000 students

– 25,000 faculty and staff

¾Providing– 61 MW of power

– 30,000 Tons of chilled water – 200,000 lbs per hour steam



BackgroundBackground

¾Voluntary Emissions ReductionPermit (VERP) submitted in Augustof 2003

¾Proposed reducing NOx byapproximately 80%

¾Accepted by the TCEQ in December of 2003

¾Completion March 1, 2007



BackgroundBackground

¾Issued Request for Qualifications(RFQ) in May of 2004

¾Over 20 firms responded to RFQ

¾Four firms, including Benz Air Engineering, interviewed



RFQ SubmittalsRFQ Submittals

Technology Drawbacks

SCR Expensive, requires ammonia or other chemical, stackmodification

Low NOxBurners

Expensive, requires extensiveboiler modification resulting in

unknown characteristics.

Over-fired Air Requires boiler modification,

increases parasitic load



RFQ Submittals Cont.RFQ Submittals Cont.

Technology Drawbacks

Water / SteamInjection

Water costs, reduced boiler capacity.

Induced DraftFGR

Could not guarantee reductionswithout water injection

Compu-NOx ®

Unanimous Selection



CompuCompu--NOxNOx ® ®

¾Lowest first cost by more than 50%

¾Guaranteed lowest NOx emissionsrate

¾Improve turndown from 10:1 to 20:1

¾Lowest operating cost (boiler operating costs reduced)

¾Shortest down-time requirements



Problem DescriptionProblem Description

¾NOx emission mandates.

¾Higher Fuel Costs

¾Burner Replacement = Uncertainty

– Unstable operation

– Inefficient



SolutionSolution

Innovative boiler control system thatmatches combustion air, fuel, and

flue gas recirculation to provide:•NOx reduction to below mandated

levels throughout boiler operatingrange

•Higher Efficiency for ROI



Combustion and ThermalCombustion and Thermal NOxNOx

¾CH4 + 2O2 CO2 + 2H2O + Heat

¾O2 + N2 N- + O- +NO-

Heat



Natural Gas ConstituentsNatural Gas Constituents

¾ Component Typical Analysis(mole %)¾ Methane 94.9

¾ Ethane 2.5¾ Propane 0.2¾ iso – Butane 0.03¾ normal – Butane 0.03¾ iso – Pentane 0.01¾ normal – Pentane 0.01¾ Hexanes plus 0.01

¾ Nitrogen 1.6¾ Carbon Dioxide 0.7¾ Oxygen 0.02

¾ Hydrogen trace

http://www.uniongas.com/aboutus/aboutng/composition.asp



NOx versus Excess OxygenNOx versus Excess OxygenNOx versus Excess Stack O2

0

20

40

60

80

100

120

140

0 1 2 3 4 5 6 7

Excess O2

N O x c o r r e c t e d t o 3 % o 2



¾Fixed speed fan controlled by dampers

¾ Inaccurate control means high excess air delivered to combustion section of boiler

(typically 14-16%).¾High temperatures and abundant oxygenradicals in flame promote NOx formation.

¾Flame instabilities at lower loads due toinability to control air flow from fixedspeed fans.

Standard Boiler OperationStandard Boiler Operation



¾Near Stoichiometric Combustion.

¾Little FGR needed for high NOxreduction.

¾Air, fuel, and flue gas recirculationflows are metered throughout the

boiler’s operating range – from hotstandby to full load conditions.

CompuCompu--NOxNOx DesignDesign



Combustion EquationCombustion Equation

StoichiometricCH4 + 2(O2) +7.52(N2) = CO2 + 2(H2O) +7.52(N2)

15% Excess O2

CH4 + 2.3(O2) +8.648(N2) = CO2 + 2(H2O) +8.648(N2) + 0.3(O2)



CompuCompu--NOxNOx AdvantagesAdvantages

¾Utilizes existing boiler burners and fans¾Can be integrated into existing plant

operating networks

¾>100 to one boiler turn-down.

¾VFD Combined with Proper PLC Control =

Control of Air and Flue gas¾Cubic Reduction of Horsepower

– 600hp fan will consume 75hp at 50% load---

0.6hp at 10% load!



Positive slope characteristic at loadsless than 50%. Impossible to control!

Stable Operating Point throughout theload. Repeatable Control throughout

the load with Unlimited Turndown.

Cubic Reduction in Power

Damper Control VFD Control



Boiler #3Boiler #3 – – University of TexasUniversity of Texas

¾ 1950’s vintage Babcock & Wilcox Boiler ¾ 500F Combustion Air Temperature.

– Competing proposals required eliminating air preheat.¾ 4 ring burners (original) and rated for 150,000

lbm/hr

¾ Compu-NOx installed 2005.¾ NOx reduced from 220ppm to 18ppm - Natural

Gas

¾ NOx reduced from 320ppm to 28ppm - #2 Oil¾ Boiler efficiency increased from 76% to 85%¾ Ability to bank boiler results in $6000.00/day

savings

¾ Simple payback in 2.2 months



Unexpected ResultsUnexpected Results

¾After control modifications boilerswere much more responsive

¾Although 20 to 1 turndown possible,water treatment issues surfaced

¾Discovered it was possible to “Bank”either boiler

¾This allowed a new operating

condition



Original PlanOriginal Plan



New PlanNew Plan



Actual ResultsActual Results

¾Savings from reduction in HP slightly

higher ~$110,000 per year ¾Savings from “Banking” boiler

– Over $2 million annually



Project SummaryProject Summary¾Both boilers surpassed the VERP

required reductions both on naturalgas and fuel oil

– Boiler 3 - 184 ppm to 22.2 ppm– Boiler 7 – 296 ppm to 27.5 ppm

¾Efficiency improvements of between5 and 10% depending on load

¾Turndown better than 20 to 1



Project Summary (Cont.)Project Summary (Cont.)

¾Savings from reduction in HP

– ~$100,000 annually

¾Savings from increased boiler efficiency (lower excess air)

– ~$850,000 annually

¾Less than a 2 year payback



ConclusionsConclusions

¾Both Emissions reduction andefficiency gains can be achievedthrough proper boiler control.

¾Existing equipment can be utilized to

achieve significant value to operatingplants.



For More InformationFor More Information

¾Robert Benz

¾Benz Air Engineering Co. Inc.

¾4061 Silvestri St. Las Vegas, NV89119

¾[email protected]



Contact InformationContact Information

¾Ryan Thompson

¾University of Texas at Austin

¾215 E. 24th Street, Austin, 78712

¾[email protected]

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