Effective Handling of Air, Water, and Oil in Ammonia Refrigeration Systems to Conserve Energy

Transcription

1 Sustainable Management of Refrigeration Technologies in Marine and Off-Shore Fisheries Sectors, 6-8 April 2017, Bangkok Effective Handling of Air, Water, and Oil in Ammonia Refrigeration Systems to Conserve Energy Laxmikant Dandawate ( Director Marketing ) Star Coolers & Condensers Pvt Ltd dandawate@starcooler.co.in Office No : Cell No :

2 Why bother at all? In our experience: Air, water and oil are the cause of most problems in refrigeration systems Symptoms include: Loosing capacity over the years Capacity problems during the summer Increased power consumption Higher service/maintenance costs Oil decomposing Unexplained behavior Often the symptoms are addressed not the root problem

3 Air What happens? Occupy condenser surface -> higher condensing pressure Blocking drainage of liquid Chemical reactions, oxidation of oil and metals Control problems due to air pockets (HP float valves) Water Oil Chemical reactions, breaking down of oil, Corrosion Shift in saturated vapor pressure Lubrication problems (especially ball and roller bearings) Heat exchanger and / or evaporator fouling Cost of oil, filling and draining by authorized personnel, disposal Risk of ammonia leaks during draining

4 Consequences on performance Rules of thumb 1 C increase mean approx.: 1% lower cooling capacity 3% lower COP 3.1% higher power consumption Discharge pressure Condenser Suction pressure Receiver Receiver ICE DRAW kch Evaporator Compressor 1 C decrease mean approx.: At +10 C 0 C -10 C -20 C -30 C -40 C -50 C Capacity -3.6% -4.0% -4.4% -5.1% -5.5% -6.5% -7.3% COP -5.0% -4.3% -3.8% -3.5% -3.9% -4.4% -5.0% Power +5.2% +4.5% +4.0% +3.6% +4.1% +4.6% +5.2% Numbers from average of Sabroe recip and screw Power is with unchanged cooling capacity

5 How do we get air and water in systems? I don t have air in my system Drawn into low pressure systems: Leaking shaft seals, gaskets, valve stems etc. draw in air including moisture Service and maintenance, all systems: Pure anhydrous R717 contain 0.3% water Inappropriate evacuation after opening (vacuum pumps used correctly?) Residual R717 absorb moisture from air Chemical reactions (non-condensibles), all systems: Ammonia and metals (especially aluminum and zinc) Alu gaskets, galvanization, zinc chromating on valves etc. Ammonia and oil in the presence of water/air reacts chemically Conclusion: ALL systems will be contaminated over time no matter the suction pressure is above atmospheric pressure

6 Symptoms of air in the system? LP float valve systems Discharge pipe Condenser Liquid drain: Max 1 to 1.5K subcooling. ALWAYS same temperature. Pressure equalization Hot top and cold bottom = problems Receiver To system Deviation from this mean air in system and/or wrong piping

7 Symptoms of air in the system? HP float valve systems Note: Air is heavier than ammonia gas Air cycles in the system: Condenser No alarming high condensing pressure! Compressor takes air and recompress it Decreased cooling capacity To system Decreasing COP Accelerating chemical reactions in compressor oil and LP side of system Corrosion, sludge and black oil HP floats always have a bleed hole because of air HP-float valve

8 Subcooling in condenser Desuperheating 80 C Works Condensing Correct function 22 C Subcooling 22 C Air Filled Doesn t work 18 C Subcooling 14 C Flooded Example: Condensing temp 22 C, Air wet bulb approx 8 C

9 Solving problems Words to live by

10 L How do we get air out? LP float valve system To wet suction Discharge pipe CONTROL BOX RT3 RT5A ON Purge OFF E V ICEDRAW.DK Collecting air above liquid surface Condenser 2 mm slit Receiver Liquid from pumps Air purger type CPA-10 Liquid to evaporators Correct piping and an effective air purger

11 E V L How do we get air out? HP float valve system To wet suction Discharge pipe CONTROL BOX RT3 RT5A ON Purge OFF Liquid From pumps Condenser HP-float valve Liquid to evaporator Air purger type CPA-10 Correct piping and an effective air purger

12 L C O E N V T L E R O H B L R Purging air, not R717 AIR PURGER TYPE CPA-10 9 SCA EVM+CVH WET SUCTION 8 AIRVENT (ARMSTRONG) RT5A RT3 CONTROL BOX Air purger capacity R717 [m3/hr] Purge ON 12 OFF 0,33 10 ALARM LIQUID POWER 0,328 9 SVA 7 EVM +CVH 6 HBLC AIR OUT 13 2 ORIFICE 14 LIQUID FROM PUMPS Volume flow at Condensing pressure [m3/hr] 0,326 0,324 0,322 0,32 0,318 0,316 0,314 0, Volume flow at 1 atm, 20 C [m3/hr] Condensing temperature [ C] INLET HIGH PRESSURE FOULED GAS (Refrigerant and non-condensable gas) 5 OIL DRAIN Flow at Condensing pressure Flow at 1 atm, 20 C FIA 4 SVA SVA 3 ICEDRAW.DK Highest pressure at lowest temperature -> lowest possible R717 content

13 Consequences H 2 0 in R717 Increased power consumption 2% reduction in refrigeration capacity each 1% water Reduced refrigeration capacity Lower evap pressure at the same temperature Oil is broken down and creates nitro compounds Nitro compounds can dissolve in the NH3 and colour it Leaks due to embrittlement of O-rings and gaskets Leaks due to galvanic corrosion Wear and tear on valves and controls 1% more power consumption each 1% water Sludge in the system 0,5% 1% % Water Note: Water accumulate on the low pressure side Max 1%

14 Measuring H 2 0 in R717 Weight % water in ammonia Water weight % 10% 9% 8% 7% 6% 5% 4% 3% 2% 1% 0% 0 0,5 1 1,5 2 2,5 3 Water remaining in glass Always take sample from Low pressure side of system W%(50 ml glass) W%(100 ml glass) Sample from polluted System (H2O and nitro compounds)

15 H 2 0 content in Oil Effect on Ball and roller bearings: Less than 100ppm recommended 300ppm -> half service life

16 CPW-15 water purger Low load High load To wet suction To wet suction LP-liquid from pump Insulation LP - float valve Nozzle Ice Self regulating No regulation devices No maintenance No electrical connections Easy installation Energy neutral LP-liquid from pump Insulation LP - float valve Nozzle Ice Liquid to subcooled liquid line Liquid to subcooled liquid line Liquid from receiver Liquid from receiver Everything should be made as simple as possible, but not simpler Albert Einstein

17 Oil management 35ppm Motor valve 35ppm (Closed when defrosting) 120ppm HBSO1 HBSO1 Condenser ICE DRAW ICE DRAW kch Compressor Oilfree hot gas for defrosting CPO Pressure equalization Receiver 120ppm Note! High TC (heat pump) : De-gassing vessel necessary >1ppm oil Liquid to evaporators kch Compressor

18 CPO HP oil separation unit Oil separation in liquid R717 HP liquid containing oil Oil-free hot gas for defrosting CPO Proof of concept: 178 liters separated in 9 months. 17 liters found on LP side due to hotgas defrost Separation: Require knowledge about oil not commonly available HB- oil switches < 1 ppm oil Dry clean oil to compressors CPO variants/options: Stand alone Combined with receiver With oil cooler liquid priority Defrost hot gas supply Advantages: Oil stays on HP side, no pollution or breakdown Very simple oil return system Maintenance free oil management No oil consumption Disadvantage: Increased refrigerant charge

19 Tomorrows problem-free R717 system To open air HBLT-A1 HBLT-C1 To open air REG LL MVS 661 G Air cooler pump system REG Pump separator Control box Evaporative condenser Make-up water system REG NH3 pump Plate freezer- pump system NH3 pump Oil collector Oil-free hot gas line CPO Equalization line Purge line CONTROL BOX Purge ON O OFF HBLC EL O V HBLC L E kch System cleaner - CPW Receiver Receiver Air purger - CPA Liquid line (sub cooled) Liquid line Flake ice machine To open air Screw compressor HBLT-C1 HBLT-A1 To open air Reciprocating compressor CONTROL SYSTEM ICE-SCREW Mk 1 HBLC ICE-MATIC ICE-MATIC HBCP HBOC MVS 661 HBSO1 HBSO1 HBCP-X ICE DRAW ICE DRAW Shell and Tube Chiller ICEDRAW.DK Economizer kch HBSO1 MVS 661 ICEDRAW.DK ICEDRAW.DK ICE DRAW by Kurt C. Hilbrecht HBOC ICEDRAW.DK

20 THANK YOU/QUESTIONS? Laxmikant Dandawate