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Design & Operation of Design & Operation of UU22AATMTM
Building on ExperienceBuilding on Experience
Jeffery E. FisherWahlco, Inc.
H. James Peters
Hamon Research-Cottrell/Wahlco Inc.
Electric Utilities Environmental ConferenceTucson, ArizonaJanuary 2002
Feb-02
2UU22AATMTM
UU22AATM TM BackgroundBackground
U2ATM (urea to ammonia) is a patented system to meet ammonia needs with reduced risks
Highest ammonia risks:• Shipping • transfer • storage
Urea is a benign material• Safely transported, transferred and stored• Readily available as bulk commodity chemical• Urea is 56% ammonia (equivalent) • Economical alternative to aqueous ammonia
Feb-02
3UU22AATMTM
UU22AATM TM BackgroundBackground
EC&C (Dr. Spencer, Dr. Cooper) licensors
Strong technical supportU.S. patents 6,077,491; 6,322,762
HRC/Wahlco AllianceOffices on both coastsFlexible execution
EC&C, Wahlco and Hamon Research-Cottrell
Feb-02
4UU22AATMTM
PROTOTYPESPROTOTYPES
Phase I and IIPrototype Reactors
Feb-02
5UU22AATMTM
UU22AATM TM BackgroundBackground
Process characteristicsOnce through processIndirect heat exchangeClosed water balance Reactor at equilibriumPredictable reaction dynamicsExperience shows no reactor fouling due to side reactions
Feb-02
6UU22AATMTM
Ammonia Generation from Urea:
NH2CONH2 + (x)H2O
NH2COONH4 + (x-1)H2O
2 NH3 + CO2 + (x-1)H2O•Urea hydrolyzes to carbamate•Carbamate dissociates to ammonia and carbon dioxide•Reaction is reverse of urea synthesis•Generates only ammonia, water, carbon dioxide
Thermal Hydrolysis of UreaThermal Hydrolysis of Urea
Feb-02
7UU22AATMTM
FormaldehydeFormaldehyde
AES/Alamitos Results from January 2000:No increase in reactor concentration ~1000 hours operation
• Feed 40% urea solution @ 0.2% formaldehyde = 1000 mg/l • Reactor liquor average from 5 samples = 1117 mg/l
HCHO is driven off in reactor• 0.4 ppm increase in HCHO upstream of catalyst over baseline• Increase agrees with material balance for ~0.2% HCHO in urea
SCR catalyst provides catalytic oxidation of HCHO• 0.02 ppm HCHO measured at stack after catalyst (>95%)
Feb-02
8UU22AATMTM
UU22AATMTM Process ControlProcess Control
Simple process control
Hydrolysis ReactorUrea Solution
PLC
NOxAnalyzer
Pressure and Flow control
Heat control
Level control
Ammonia Product Gas
Feb-02
9UU22AATMTM
UU22AATMTM Process ControlProcess Control
Simple process control
Hydrolysis ReactorUrea Solution
PLC
NOxAnalyzer
Pressure and Flow control
Heat control
Level control
Ammonia Product Gas
Urea solution is dissolved in DI water at 40 to 60 wt%
Feb-02
10UU22AATMTM
UU22AATMTM Process ControlProcess Control
Simple process control
Hydrolysis ReactorUrea Solution
PLC
NOxAnalyzer
Pressure and Flow control
Heat control
Level control
Ammonia Product Gas
Solution is pumped to reactor to maintain constant level
Feb-02
11UU22AATMTM
UU22AATMTM Process ControlProcess Control
Simple process control
Hydrolysis ReactorUrea Solution
PLC
NOxAnalyzer
Pressure and Flow control
Heat control
Level control
Ammonia Product Gas
Heat is added to initiate and control endothermic hydrolysis reaction
Reaction products go into reactor liquid which then releases:
CO2
NH3, H2O
Feb-02
12UU22AATMTM
UU22AATMTM Process ControlProcess Control
Simple process control
Hydrolysis ReactorUrea Solution
PLC
NOxAnalyzer
Pressure and Flow control
Heat control
Level control
Ammonia Product Gas
Reactor is maintained at constant pressure
by regulating heat input
Feb-02
13UU22AATMTM
UU22AATMTM Process ControlProcess Control
Simple process control
Hydrolysis ReactorUrea Solution
PLC
NOxAnalyzer
Pressure and Flow control
Heat control
Level control
Ammonia Product Gas
Product gas piping is maintained at temperature above carbamate formation and water condensation temperatures
Feb-02
14UU22AATMTM
UU22AATMTM Process ControlProcess Control
Simple process control
Hydrolysis ReactorUrea Solution
PLC
NOxAnalyzer
Pressure and Flow control
Heat control
Level control
Ammonia Product Gas
Controlled product gas stream can be used directly
or diluted with air at ammonia flow control unit
Feb-02
15UU22AATMTM
Start UpStart UpReactor contains equilbrium liquid from prior operation
Approximately 15%-20% urea or carbamateApproximately 3% ammonia
Heating mode in stages to achieve 250ºF and 40 psig under temperature controlMode changes to injection under pressure control at 80 psig set pointAbout 30-45 minutes from cold condition, 0-15 minutes from idles condition
Vapor Phase NH3 Inventory
Pressure
Level
NH3
Feb-02
16UU22AATMTM
Normal Operation and RampingNormal Operation and RampingInjection mode
Constant pressure and levelTemperature and steam varyVapor inventory (~1 minute) instantly availableChange in heat input adjusts reaction rate to maintain reactor pressure (1 ºF change yields ~5% change in rate) Level control maintains urea solution (~3 hours inventory)
Vapor Phase NH3 Inventory
Pressure
Level
NH3
Feb-02
17UU22AATMTM
Normal ShutdownNormal Shutdown
Normal shutdown NH3 continues to processSteam and feed pump shutoffReactor cools (due to endothermic reaction) and enters standby mode
Vapor Phase NH3 Inventory
Pressure
Level
NH3
Feb-02
18UU22AATMTM
UU22AATMTM ProjectsProjects
Allegheny Energy/Harrison Station 3,700 lb/hrAllegheny Energy/Pleasants Station 1,800 lb/hrAES/Alamitos Station 260 lb/hrAES/Huntington Beach Station 340 lb/hrDTE Energy/Monroe 10,000 lb/hrConstellation Energy/Wagner Station 460 lb/hrIST/Dominion Energy/Kauai 30 lb/hr
Feb-02
19UU22AATMTM
Experience ReviewExperience Review
AES/Alamitos400:1 scale-up from pilotBoiler load following and NOx ComplianceComparison to 29% aqueousFormaldehyde analysisReactor liquid and residual materials analysis
• Predictable based on urea trace materials
• No side reactions• Confirmed materials of construction
AES Huntington BeachSmooth start-up One day to automatic operation Carbamate formation and heat tracing4000 operating hours to date
Feb-02
20UU22AATMTM
Load FollowingLoad Following
Process easily follows boiler load variations AES Alamitos hourly averaged dataApproximately 10:1 turndown over typical daily cycling operation
Feb-02
21UU22AATMTM
Comparison of Prototype Operation Comparison of Prototype Operation to 400 lb/hr systemto 400 lb/hr system
Temperature from Reaction rate
200
220
240
260
280
300
320
340
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0
Specific reaction rate
Tem
pera
ture
- de
g F
Feb-02
22UU22AATMTM
Allegheny Energy SupplyAllegheny Energy Supply
Harrison and PleasantsHarrison and Pleasants
The Harrison project was the first U2A commercial award and represents “new technology” risk for Allegheny.Phase I operations were planned to identify any issues with process design or procedures well in advance of May 2002 SCR start up.Phase I deemed successful by mid September 2001.Allegheny Energy/Harrison operation builds on U2A experience at AES/Alamitos and AES/Huntington Beach.
Feb-02
23UU22AATMTM
UU22AATMTM –– Allegheny HarrisonAllegheny HarrisonAllegheny Energy Supply Harrison Station
3700 lb/hr ammonia from ureaSupply to 6 SCRs on 3 x 600MWThree 50% reactors
ScopeUrea dry storage, handlingUrea solution preparationHydrolysis reactorsAmmonia flow control units
ScheduleFirst 1850 lb/hr reactor
• operational in September 2001Unit #1 start up May 2002
Test ResultsExceeded rating by >20%Met load-following and safety goals
Feb-02
24UU22AATMTM
Harrison Phase IHarrison Phase IProduction of Ammonia (lb/hr) vs. Temperature (F)
Data taken at/near equilibrium during manual operationFull production temperature within a few degrees of predictionReactor capable well in excess of nominal rating
Feb-02
25UU22AATMTM
Instantaneous Ramp UpInstantaneous Ramp Up
Feb-02
26UU22AATMTM
Normal ShutdownNormal Shutdown
Feb-02
27UU22AATMTM
Experience ReviewExperience Review
Allegheny Energy SupplyHarrison Phase I
Confirmation of process scale up• 2000:1 from pilot• 5:1 from AES
Confirmation of start up/shutdownHeating characteristics for tube bundle
• Instantaneous ramping
Feb-02
28UU22AATMTM
What’s Next?What’s Next?
Allegheny Energy SupplyHarrison Phase IIPreparation for May 2002
Start Up – Unit #1 SCRBalance of delivery/constructionUrea supply and logistics
• Urea supplier selection Urea dry storageAutomated batch dissolvingTwo reactor operation
• One operating, one standby
Other U2A start ups – May 2002DTE/Monroe – one unitConstellation/Wagner
WAHLCO, INC.