Condensate Management and Treatment for Campus Systems IDEA Campus Energy Conference Debbie Bloom, Principal Consultant Steve Spiwak, Market Development Mngr
Overview Why corrosion occurs Condensate best practices treatment strategies Chemical treatment Concerns with chemical treatment Mechanical treatment Monitoring and control
The Value of Condensate as Boiler Feedwater Heat Reduced fuel usage [typically $8-19 per 1000 gal] A 20,000 lb/hr boiler paying $10/MMBtu for natural gas could save over $14,000/yr by increasing condensate 5% Water Decreased make-up water demand Reduced water discharge Improved Boiler System Reliability Reduced Chemical Cost
The Risks of Returning Condensate Hydraulic oils, lubricants, greases Raw water /treated water intrusion Hardness, silica, oxygen Corrosion by-products Iron, Copper
Condensate Corrosion
Condensate treatment is. A fight against three dissolved gases: Carbon Dioxide Oxygen Ammonia
Carbon Dioxide Sources Breakdown of feedwater alkalinity - Heat 2 HCO 3 CO 3= + H 2 O + CO 2 Bicarbonate Carbonate Water Carbon Dioxide Heat CO 3 = + H 2 O 2OH - + CO 2 Carbonate Water Hydroxide Carbon Dioxide Air inleakage Organics breakdown
Carbon Dioxide CO 2 (gas) is not aggressive in dry steam Dissolves in the condensate forming carbonic acid CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - Carbon Water Carbonic Acid Bicarbonate Dioxide Acid
ph Value 7.5 7.0 6.5 6.0 104 0 F (40 o C) 140 0 F (60 o C) 176 0 F (80 o C) ph Values of Solutions of Carbon Dioxide in Pure Water 5.5 176 o F (80 o C) 140 o F (60 o C) 104 o F (40 o C) 0 0.2 0.4 0.6 0.8 1.0 1.2 Concentration of CO2 - ppm
Corrosion of Carbon Steel and Copper Depends on ph of Water Corrosion Rate Copper Alloys Carbon Steel 7 8 9 10 ph
Carbonic Acid Corrosion on Mild Steel Results in a thinning and grooving of the metal surface
Oxygen Sources Air in-leakage - pumps, traps, vacuum systems, vented receivers Inefficient deaeration operation Raw water intrusion - pump seals, heat exchanger leaks
Pitting type corrosion Rapid localized metal loss Combined corrosion rate for CO 2 and O 2 is 10 to 40% faster than the sum of either alone... Oxygen Corrosion
Condensate Best Practices Treatment Strategies
Total Cost of Treating Condensate Total Cost of Treating Condensate Cost of Chemical Component Cost of Mechanical Component Total Cost
Chemical Treatment Strategies
Chemical Condensate Treatment Neutralizing amines Filming amines Non-nitrogen based filmers
Simple Acid/Base Reaction Amine hydrolysis in water: R-NH 2 + H 2 O R-NH 3 + + OH - Neut amine water Neut amine hydroxide CO 2 hydrolysis in water: CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - carbon dioxide water carbonic acid bicarbonate Net reaction: R-NH 2 + H 2 CO 3 R-NH 3+ + HCO 3 - Neut Amine carbonic acid Neut amine bicarbonate
Neutralizing Amines have Special Characteristics: Vapor/liquid (V/L) distribution ratio Molecular weight Basicity Component blend ratio
Filming Amines Long chain amines that adsorb onto the metal surface Function at the lower ph range of 6.5 to 9.0 Metallic Wall O 2 O 2 O 2 CO 2 CO 2 O 2 O 2 O 2 O 2 CO 2 O 2 CO 2 O 2 CO 2 CONDENSATE CO 2 CO 2 O 2 O 2 O 2 CO 2 CO 2 Protective Filming Amine Layer
A Filmed Metal Surface Promotes Dropwise Condensation
Non-Nitrogen based Filmers Filming technology Dosage dependent on surface area and not contaminant concentration Not volatile must be fed to the steam Some films persist during outages
Important Differentiators Between Filming Types Regulatory FDA and CFIA approved, including dairies NSF approved (previously USDA) Kosher certified Economical Safety Technical (Compatible with system/process) Doesn t require co-feed with neutralizing amines
Comparison of Programs Effective for Feed point Dosage Control Handling Additional Precautions Neutralizing Amines CO 2 Feedwater or steam Based on CO 2 ph, typically 8.5 to 9.2 8.5 Mod. flammability; Exposure limits May exceed Can form limits in some deposits systems Filming Non-Nitrogen Amines Based Filmer CO 2, O 2, NH 3 Steam Based on size of system Iron and corrosion results Trace residual plus ph 6.5 to Non-toxic Feedpoint is critical
Comparison of Programs Effective for Feed point Dosage Control Neutralizing Amines CO 2 Feedwater or steam Based on CO 2 ph, typically 8.5 to 9.2 Filming Amines CO 2, O 2, NH 3 Steam Non-Nitrogen Based Filmer Based on size of system Trace residual Iron and plus ph 6.5 to corrosion 8.5 results
Comparison of Programs Regulatory Safety Additional Precautions Neutralizing Filming Non-Nitrogen Amines Amines Based Filmer FDA, NSF (USDA) w limits OSHA limits No OSHA limits Mod. flammability; Exposure limits Non-toxic May exceed Can form Feedpoint is limits in some deposits critical systems
Concerns about Chemical Treatment
Concerns about Chemical Treatment Steam must be safe for use in Food preparation Humidification Comfort and domestic heating Laundry Academic research Steam must comply with appropriate government reg s
FDA Approved Amines Amine Cyclohexylamine Diethylaminoethanol Morpholine Octadecylamine Sorbitol anhydride esters Max. Level In Steam ** 10 ppm 15 ppm 10 ppm 3 ppm 15 ppm ** Combined amine total must be less than 25 ppm.
Amine PEL and Odor Threshold Amine ACGIH TWA ppm OSHA PEL / TWA ppm Odor Threshold ppm in air Morpholine 20 20 0.14 DEAE 2 10 0.04 Cyclohexylamine 10 10 0.90 ACGIH = American Conference of Governmental Industrial Hygienists OSHA = Occupational Safety and Health Administration
Amine Concentrations in Air ppm in air 100 10 1 0.1 0.01 Morpholine DEAE Cyclohexylamine 0.001 0.0001 OSHA PEL / TWA Odor Actual ACGIH (American Conference of Governmental Industrial Hygienists) TWA for DEAE is 2 ppm.
Amine Concentrations in Air ppm in air 100 10 1 0.1 0.01 0.001 20 10 10 0.14 0.04 0.90 Morpholine DEAE Cyclohexylamine 0.004 0.0016 0.0008 0.0001 OSHA PEL / TWA Odor Actual ACGIH (American Conference of Governmental Industrial Hygienists) TWA for DEAE is 2 ppm.
Mechanical Treatment Strategies
Mechanical Treatment Strategies Good system design Proper maintenance Reduction of system carbon dioxide Polish or sewer condensate as needed
Use Good Engineering Practices Insulate and trap lines Bottom of vertical rises Upstream of control valves At 100 to 300 foot intervals for horizontal runs Size lines and traps properly Slope lines correctly
Use Good Engineering Practices Establish trap maintenance program Avoid any elevation increase on return condensate lines Size return condensate lines for steam/water mix
Good Maintenance is Critical. 3-7% fuel savings from effective trap management program A trap with 1/8 orifice loses 13.7 lbs/hr at 15 psig and 52.8 lbs/hr at 100 psig 1.4% fuel savings from repairing steam leaks From US Dept of Energy,2002
Leaking Steam Trap Losses Trap Orifice Diameter (inches) 15 Steam Loss (lbs/hr) Steam Pressure (psig) 100 150 300 1/16 3.4 13.2 18.9 36.2 1/8 13.7 52.8 75.8 145 1/4 54.7 211 303 579 3/8 123 475 682 1,303
Carbon Dioxide Reduction Demineralization Reverse osmosis Gas transfer membranes Dealkalization
Monitoring and Control
Condensate Monitoring and Control Testing provides: Treatment performance check Condensate system contamination - identification and prevention Compliance check
Performance - Primary Testing ph Corrosion by-products; e.g. iron, copper, etc. Conductivity
Compliance Check - Amines Primary testing doesn t indicate amine concentration Commonly determined by gc on grab samples Fluorescence-based method allows accurate, in-line measurement Can assist operators in maintaining compliance to target dosages Minimizes concerns about exceeding limits
Schematic of Monitoring System
On-Line Detection of Amine CHA Concentration (ppm) 3.5 3 2.5 2 1.5 1 0.5 3.0 ppm 2.0 ppm 1.0 ppm 0.5 ppm 0 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 Time (minutes:seconds) 0 ppm
CHA Concentration During Upset Cogen Facility 3.5 CHA Concentration (ppm) 3 Amine Pump On Amine Monitor 2.5 Grab Sample 2 Amine Pump Off 1.5 1 0.5 0 0:00 0:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 Time (hours:minutes)
Sampling Requirements Cooled to less than 90 o F Sample flow throttled at outlet only Stainless steel sample lines Continuous flow or sufficient purge times - varies with expected level Adequate velocity; 5-6 ft/sec
Where Do You Sample? Steam Critical equipment or largest steam users Known problem areas Flash steam/cascade systems Composite streams, ideally prior to receivers or flash tanks Return condensate streams
Effective Condensate Management Combines chemical, operational, and mechanical components Is designed for the specific system Effectively monitors and controls condensate chemistry Treatment performance Condensate quality Compliance to gov t regs and campus limits
Effective Condensate Management Minimizes condensate corrosion Maintains condensate quality for reuse as boiler feedwater Reduces steam/condensate/energy losses from steam/condensate leaks Protects equipment, lines, and tanks Reduces maintenance costs
Steam BestPractices Resources Available Steam Web Site: www.oit.doe.gov/bestpractices/ Clearinghouse: 1-877-EERE-INF (877-337-3463)
"Insanity defined is the act of doing things the same way you have always done them... and expecting different results." Albert Einstein