Condensate Management and Treatment for Campus Systems

Transcription

1 Condensate Management and Treatment for Campus Systems IDEA Campus Energy Conference Debbie Bloom, Principal Consultant Steve Spiwak, Market Development Mngr

2 Overview Why corrosion occurs Condensate best practices treatment strategies Chemical treatment Concerns with chemical treatment Mechanical treatment Monitoring and control

3 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

4 The Risks of Returning Condensate Hydraulic oils, lubricants, greases Raw water /treated water intrusion Hardness, silica, oxygen Corrosion by-products Iron, Copper

5 Condensate Corrosion

6 Condensate treatment is. A fight against three dissolved gases: Carbon Dioxide Oxygen Ammonia

7 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

8 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

9 ph Value F (40 o C) F (60 o C) F (80 o C) ph Values of Solutions of Carbon Dioxide in Pure Water o F (80 o C) 140 o F (60 o C) 104 o F (40 o C) Concentration of CO2 - ppm

10 Corrosion of Carbon Steel and Copper Depends on ph of Water Corrosion Rate Copper Alloys Carbon Steel ph

11 Carbonic Acid Corrosion on Mild Steel Results in a thinning and grooving of the metal surface

12 Oxygen Sources Air in-leakage - pumps, traps, vacuum systems, vented receivers Inefficient deaeration operation Raw water intrusion - pump seals, heat exchanger leaks

13 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

14 Condensate Best Practices Treatment Strategies

15 Total Cost of Treating Condensate Total Cost of Treating Condensate Cost of Chemical Component Cost of Mechanical Component Total Cost

16 Chemical Treatment Strategies

17 Chemical Condensate Treatment Neutralizing amines Filming amines Non-nitrogen based filmers

18 Simple Acid/Base Reaction Amine hydrolysis in water: R-NH 2 + H 2 O R-NH 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

19 Neutralizing Amines have Special Characteristics: Vapor/liquid (V/L) distribution ratio Molecular weight Basicity Component blend ratio

20 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

21 A Filmed Metal Surface Promotes Dropwise Condensation

22 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

23 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

24 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 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

25 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

26 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

27 Concerns about Chemical Treatment

28 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

29 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.

30 Amine PEL and Odor Threshold Amine ACGIH TWA ppm OSHA PEL / TWA ppm Odor Threshold ppm in air Morpholine DEAE Cyclohexylamine ACGIH = American Conference of Governmental Industrial Hygienists OSHA = Occupational Safety and Health Administration

31 Amine Concentrations in Air ppm in air Morpholine DEAE Cyclohexylamine OSHA PEL / TWA Odor Actual ACGIH (American Conference of Governmental Industrial Hygienists) TWA for DEAE is 2 ppm.

32 Amine Concentrations in Air ppm in air Morpholine DEAE Cyclohexylamine OSHA PEL / TWA Odor Actual ACGIH (American Conference of Governmental Industrial Hygienists) TWA for DEAE is 2 ppm.

33 Mechanical Treatment Strategies

34 Mechanical Treatment Strategies Good system design Proper maintenance Reduction of system carbon dioxide Polish or sewer condensate as needed

35 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

36 Use Good Engineering Practices Establish trap maintenance program Avoid any elevation increase on return condensate lines Size return condensate lines for steam/water mix

37 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

38 Leaking Steam Trap Losses Trap Orifice Diameter (inches) 15 Steam Loss (lbs/hr) Steam Pressure (psig) / / / / ,303

39 Carbon Dioxide Reduction Demineralization Reverse osmosis Gas transfer membranes Dealkalization

40 Monitoring and Control

41 Condensate Monitoring and Control Testing provides: Treatment performance check Condensate system contamination - identification and prevention Compliance check

42 Performance - Primary Testing ph Corrosion by-products; e.g. iron, copper, etc. Conductivity

43 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

44 Schematic of Monitoring System

45 On-Line Detection of Amine CHA Concentration (ppm) 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

46 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 :00 0:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 Time (hours:minutes)

47 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

48 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

49 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

50 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

51 Steam BestPractices Resources Available Steam Web Site: Clearinghouse: EERE-INF ( )

52 "Insanity defined is the act of doing things the same way you have always done them... and expecting different results." Albert Einstein

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