Drying training Equipment Operation and control
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No manufactured product plays a more significant role in every area of human activity than paper and paper products. Its importance in everyday life is obvious from its use in recording, storage and dissemination of information. Virtually all writing and printing is done on paper. It is the most widely used wrapping and packaging material, and is important for structural applications. The uses and applications for pulp and paper products are virtually limitless. Apart from the products and services that it provides, the paper and pulp industry is one of the major manufacturing industries in the world providing employment for vast number of people and contribute to national economy. The paper making process is essentially a very large dewatering operation where a diluted solution of pulp suspension with less than 0.5% fibre solid is used. The major sections of a paper machine consist of: forming section, press section and dryer section. In the forming section, the fibres present in the diluted pulp and water slurry form paper web through drainage by gravity and applied suction below the forming fabric. In the press section additional water in removed by mechanical pressure applied through the nips of a series of presses or rotating rolls and the wet web is consolidated in this section. Most of the remaining water is evaporated and inter-fibre binding developed as the paper contacts a series of steam heated cylinder in the dryer section. Water removal from the wet web to the final moisture level between 6% and 7% is a critical step of papermaking. Majority of the functional properties of paper are developed in this section. In spite of its key role in papermaking, large equipment size, and large capital and operating costs, drying is arguably the least understood papermaking operation. Books on papermaking technology generally devote fewer pages to drying than other papermaking operations such as forming, pressing or calendaring. A similar situation is found in papermaking courses, in which drying occupies a shorter time than the proportion of space it takes in a paper machine. Furthermore, a large portion of that time is devoted to the description of the equipment by its suppliers rather than to its operation by the papermakers.
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Drying training Equipment Operation and control
- 1. Drying •Introduction •Background •Why is it Important? •Drying Theory •Equipment Operation and Control
- 2. RELATIVE COST OF WATER REMOVAL FORMER PRESS DRYER 0 5 10 15 20 (Drainage) (Evaporation)(Compression) WATER REMOVED (kg water/kg fiber) CONSISTENCY 1.3 95% 825 10-13% 5.3 40% RelativeCost
- 3. Exhaust Air Recirculated Air Supply Fan Combustion Air Condensate Hood Exhaust Fan Fresh Air Steam Burner Yankee Fuel Evaporated Water Air Tissue Machine Drying System YANKEE & HOOD SYSTEMS
- 4. Air Impingement Dryer Shell Steam Drying: Simultaneous Heat & Mass Transfer Sheet MassTr.(Evap.) HeatTr. HeatTr. YANKEE HOOD
- 5. Drying •Introduction •Yankee Dryer •Steam In •Condensate Out •Drying Theory •Equipment Operation and Control •Hot Air In •Evaporated Moisture Out •Yankee Hood
- 6. Backside (Drive Side) Frontside (Tending Side) Steam In KC Stayed Head Yankee Dryer Stay Bar Blowthrough Steam & Condensate Out Blowthrough Steam & Condensate Out Shell Journal Head Head Condensate Removal Pipe
- 7. Yankee Dryer Heat Transfer Coefficients Sheet RCoat = 1/hCoat RShell = 1/hShell =t/kShell RCond = 1/hCond RSheet =1/hSheet 1/UD Condensate Dryer Shell Coating Steam HeatTransfer Sheet/Coating Adhesion Dryer/Coating Adhesion
- 8. Motive Steam Warm Up Steam Atmosphere Condensate Dryer Hood Flash Tank Yankee Dryer Steam & Condensate System Sight Glass
- 9. Model of Condensate Behavior Ponding Cascading Rimming
- 10. 0 0.1 0.2 0.3 0.4 0.5 0 500 1000 1500 Condensate Rimming Thickness (in) Hong & Appel White & Higgins Condensate Rimming Velocity DryerSpeed(fpm)
- 11. 0 0.020 0.015 0.010 0.005 0.025 Dryer Speed (fpm) Heat Transfer Resistance of Condensate Rimming Speed 1000 2000 3000 4000 5000 CondensateResistance (HrFtF/BTU 2
- 12. Ways to Avoid the Rimming Effect Minimize the condensate layer Bypass the condensate layer Create Turbulence
- 13. Condensate Out Ribbed Dryer With Soda Straw Condensate System ShellRibs Grooves Soda Straws
- 18. Dryer Rotation Movement in Relation to Dryer Shell Condensate Movement in Relation to Dryer Shell Minimum Condensate Thickness Maximum Condensate Thickness GRAVITY
- 19. Top 12 39 6 Spilling Over Behind Bars Wave Advances Ahead of Bars Spilling Over Ahead of Bars Wave Advances Behind Bars Spoiler Bars Rotation
- 23. 100,000 cfm 100,000 cfm 25,000 cfm ? 25,000 cfm ? Infiltration / Exfiltration Suck / Spill
- 24. 100,000 cfm 100,000 cfm 25,000 cfm ? 0 cfm ? Infiltration / Exfiltration Suck / Spill
- 25. 100,000 cfm 100,000 cfm 0 cfm ? 25,000 cfm ? Infiltration / Exfiltration Suck / Spill
- 28. Identified Problems on B1 • Make-up air dampers closed • This condition results in the hood not being balanced (infiltration/exfiltration) • This condition make the system less energy efficient.
- 30. Exhaust Tubes Supply Plenum Exhaust Plenum Exhaust Duct Supply Ducts Burners or Heat Exchangers Supply Fans Exhaust Air Exhaust Fans Fresh Air Fresh Air Tissue Machine Dryer Hood
- 31. FEATURES SUITABLE FOR: - New machines - Rebuilds / replacements - No limit for paper width VALUES - lower energy consumption at same (competitors’) performance = Less cost per ton TECHNICAL DATA - Impingement speed up to 37400 fpm - Impingement temp. up to 950 °F - Specific evaporation up to 41 lb/hft2 Metso Paper Basic SC- Yankee Hood
- 32. Drying •Introduction •Condensate Removal System •Steam and Blowthrough Control •Hood Air System •Drying Theory •Equipment Operation and Control
- 33. 29 Gravities Condensate Removal 7000 kg/hr Steam Input 7000 kg/hr Condensate Output
- 34. How do you get Condensate out of a Yankee Dryer ? • Differential Pressure • Blow Through Steam – Velocity Control
- 35. 0 Pressure Drop vs. Blowthrough Flow Blowthrough Flow (kg/hr) 0 600 500 1000 1500 2000 2500 3000 150 300 450 Density System Blowthrough Curve Density + Friction (1) (2) (3) PressureDrop(kPa) Friction
- 36. 0 PRESSURE DROP VS. BLOWTHROUGH EFFECT OF SPEED INCREASE Blowthrough Flow (kg/hr) 0 600 500 1000 1500 2000 2500 3000 150 300 450 1600 m/min 1500 m/min Friction Density DropPressure(kPa)
- 37. Two Phase Flow Regimes Bubbly Flow Slug Flow Churn Flow Annular Flow
- 38. Pressure Drop vs. Blowthrough Flow Effect Of Condensing Rate Increase Blowthrough Flow (kg/hr) 0 500 1500 2500 3000 0 150 300 450 600 700 kPa 800 kPa PressureDrop(kPa) 1000 2000
- 39. Controlling Blowthrough Flow •Stable condensate removal - Annular flow velocity > 21 m/sec. Reduces the density with more steam. Makes condensate removal easier •Pressure drop is not a reliable indicator of blowthrough flow. Blowthrough should be controlled by controlling flow. (Or in the case of B3 – Velocity)
- 40. Effect of Yankee Pressure On Density and Blow-Through •Steam density changes significantly with pressure 100 psig steam (7 bar) -- 0.24 m^3/kg 50 psig steam (3.5 bar) – 0.42 m^3/kg •The higher the density the more blow-through steam is required for good evacuation. For consistent condensate removal if we operate at various Yankee steam pressures we need to have various blow through (Velocity) set points.
- 41. Ribbed Yankee With Soda Straws
- 42. Kimberly-Clark Condensate Scoop Steam & Condensate In Condensate & Steam Out Dryer Shell Scoop Condensate Layer
- 43. Yankee Dryer Steam & Condensate System LIC DPI PIC TT PI Motive Steam Warm Up Steam PIC Vent Valve Blowthrough Valve Thermocompressor Warm-up Valve Steam Make-up Valve LIC Steam/Condensate Separation Blowthrough & Vent Valves Steam Supply Control F.T. Condensate Dryer Sight Glass FIC
- 44. Function: Allows blow through steam and condensate to separate. Condensate Separation System LIC Sight Glass TT PI LICF.T. Condensate Dryer DPI
- 45. Blowthrough and Vent Valves Vent Valve Blowthrough Valve F.T. Functions: > Control Blowthrough Flow > Vent Non-Condensible gases to Atmosphere Dryer FIC
- 46. Yankee Dryer Steam Supply System Motive Steam Warm Up Steam Warm-up ValveSteam Make-up Valve Functions: > Control dryer steam pressure > Recover blow through steam Thermo Compressor Blowthrough Steam Dryer PIC
- 47. Thermocompressor Discharge Nozzle Diffuser Body (Mixing Area) Suction Inlet Motive Steam Inlet Actuator Spindle
- 49. -100 55 60 65 75 70 80 85 90 95 100 50 -60-80 -40 -20 0 20 40 60 80 100 Effect of Thermocompressor Nozzle Opening on Suction Flow % Suction Flow Discharge Nozzle Diffuser Suction Inlet Motive Steam Inlet Actuator Spindle %MotiveNozzleOpen
- 50. Thermocompressor Sizing The thermocompressor spindle can regulate dryer steam pressure. Changes in spindle opening also change suction flow (blowthrough). This can result in blowthrough flow instability and problems with condensate removal. Thermocompressors should be sized so that they remain 100% open 100% of the time.
- 51. Hood Yankee Remove Evaporated Water Supply Hot Air Control Creping Moisture Functions of a Dryer Hood
- 52. Three Main Control Parameters • Air Temperature – Temperature of the impingement air reaching the sheet • Impingement Velocity – Nozzle Velocity of the air reaching the sheet • Return Humidity – Humidity of the air at the entrance to the burner
- 53. Effect of these Parameters on Heat Transfer Rate Hood Drying Rate Impact 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 2 4 6 8 10 12 14 16 18 20 Hood Rw (# / hr-sq ft) Normalizedvalueof IdependentVariables Effect of Humidity Effect of Temperature Effect of Nozzle Velocity
- 54. Effect of These Parameters on Fuel Cost Natural Gas Consumption Rate 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Normalized Gas Consumption Normalizedvalueof IndependentVariables Effect of Humidity Effect of Temperature Effect of Nozzle Velocity
- 55. Exhaust Tubes Supply Plenum Exhaust Plenum Exhaust Duct Supply Ducts Burners or Heat Exchangers Supply Fans Exhaust Air Exhaust Fans Fresh Air Fresh Air Tissue Machine Dryer Hood
- 56. Main Gas Combustion Air Main Gas Combustion Air TTTT TC TCTV TV Tissue Machine Hood System Temperature Control PT PT
- 57. TC TCTV TV Tissue Machine Hood System SC SC Air Velocity (h ) Control Dampers a
- 58. Hood - Yankee Clearance The hood must supply air in a way to: •Penetrate the air boundary layer. •Promote effective mass transfer. Initial jet diameter depends on nozzle diameters and the shapes of their edges. As the jets travel farther from the nozzle exits, they begin to break up. Optimum heat transfer occurs when the nozzle to sheet spacing is 4-7 nozzle diameters.
- 59. Hood Yankee Exhaust Air Out Energy In Cold Air In Effect of Exhaust Air on Hood Energy Air Humidity 0.2 0.4 Drying Rate 4% Drying Cost 25%
- 60. Drying •Introduction •Yankee Dryer •Yankee Hood •Drying Theory •Equipment Operation and Control •Operating Centerlines
- 61. Drying •Introduction •Drying Theory •Equipment and Control •Best Practice Development • The Best Practices
- 62. Current Best Practices Hood System Performance KPI-01 Hood Performance Fuel consumption is less than 3.0 MMBTU/MT KPI-02 Hood Performance Pressure distribution difference between crescent headers in the same hood half, with profiling dampers open, is maintained at less than plus or minus 5%. Safety HD-01 Safety Lockout and confined space entry procedures are in place and practiced. HD-02 Safety No water streams or sprays are used to contact high temperature or insulated surfaces of the hood. HD-03 Safety Mechanical stops are checked annually to make sure the hood cannot contact the Yankee. HD-04 Safety Personal protective equipment is provided and used when working around hoods. HD-05 Safety Air Nozzle Best Practices are in use when cleaning around hoods HD-06 Safety Burner management interlocks are checked annually. (Fuel High/Low Pressure Switch) (Proof of Combustion Air Flow) (High Burner Temperature Shutdown)
- 63. Rate of Rise 1.) Put LIC in Manual 2.) Lower level in FV 3.) Close isolation valves (manually) 4.) Measure time for condensate to rise a given height Measurement Locations LIC Sight Glass TT PI LICF.T. Condensate Dryer DPI 5.) Restore system to normal
- 64. Measurement Locations Wet End Exhaust Humidity Operating Temperature Operating Temperature Dry End Exhaust Humidity
- 65. Measurement Locations Hood Pressure Measurements Combustion Fuel And Air Pressure Measurements Supply Fan Speed