ABB Oy, KPM Sakeusmittaukset paperikoneen massanvalmistuksessa
KPM Kajaani Process Measurements Ltd. KPM was established 2001 KPM was acquired by ABB on 2011, now
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Comparison of Consistency Measurement Technologies
Technologies Shear force consistency transmitters Rotary type Blade type Static Active Optical Reflection, scattering Attenuation Direct light Polarized light Microwave Velocity of microwaves all technologies are indirect measurements not measuring dry weight of material in g/l or Cs% as done in laboratory CCD-camera image,ultrasonic, Nuclear...very rarely used
Operating range of consistency transmitters Transmitter Type: Rotating 1,5-16 (SW > 0,8%, HW > 1,2%) Limitations: -sensitive for grade changes Blade Optical 2-8 0-2 0-5 (TMP, GW) 6-16 -needs laminar flow, sensitive for grade changes -sensitive for grade changes -air Microwave 0-50 -conductivity -air 0 2 4 6 8 10 12 14 16 Consistency-%
Cost of consistency transmitters Transmitter Type: Rotating Blade Optical Microwave 0 2 4 6 8 10 12 14 16 1000 Euro
Shear Force transmitters Existing pipe line Rotary type Blade type 90% of all transmitters in use are shear force type Measure fiber consistency, does not measure fillers Different grades require different calibration receipt DN 150 mm
Modern design of Rotary Consistency Transmitter Smaller size Low weight Direct Drive Servo Motor Less Maintenance / repair No drive belt No wearing parts in motor Only 1-phase power supply No 3-phase power to sensor Removability from process available with Gate Valve Installation No waiting for shutdown No draining of process pipe
Selection Criteria for Rotary Transmitter Large pipe (>DN400, 16 ) Low flow rate ( blade type transmitter requires min 0,5m/s) Consistency 2-3% (blade measures but signal is noisy, rotary still gives accurate measurement ) Production measurement ( = Flow rate * Consistency) High sensitivity and accuracy applications, such as after the mixing chest and machine chest Not enough straight pipe section after the pump to install blade transmitter High amount of air in the process with low pressure, microwave technology cannot be used
Blade consistency transmitter Basic design of measurement blade 50 years old 2 wire technology and smart electronics KC/3 Static Blade
Blade Consistency Transmitter Shear force principle Requires laminar flow conditions, turbulence disturbs measurement Operates well on specified flow range 0,5-5m/s Sensitive to grade variations Gap measurement probe Probe protection Measuring arm Diaphragm (2mm thick) Flow Sensor blade
One piece sensor body and diaphragm Diaphragm works as a spring No maintenance (no O-ring, no seals no leaks) Gap measurement probe Probe protection Measuring arm Diaphragm (2mm thick) Flow Sensor blade
Selection Criteria for Blade Transmitter Cheapest solution wanted Not required high precision, early in process After MC-pump where Cs>10%, as good as rotary Flow rate relatively steady Consistency more than 3% up to 16%% and same fiber mix
Comparison of shear force transmitters Blade type + Price + Reliable measurement if conditions are suitable (process, installation) + No wearing parts, no preventive maintenance + 2-wire transmitter - Require laminar plug flow - Long straight pipes before and after installation point - Limited acceptable flow range Rotary type + Performance + Turbulent flow acceptable + Freedom of installation location + Wide flow range + Wide measurement range 1,5-16% - Price - Wearing parts; seals, bearings, needs preventive maintenance
Optical Consistency transmitters Inline type Mainly for clean not refined mechanical pulps Installed to process pipeline with saddle and clamps By-pass type Low consistencies below 2%, Head box and white water Save-all Sensor is installed in by pass-line normally over pump
Optical consistency transmitters Best choice for very low consistency applications, below 2%Cs Works best with clean pure pulps, like TMP, GW, Kraft pulp. Lignin, black liquor disturb measurement Grade sensitive (fiber lenght, fines content, freeness) Air content in pulp affects the measurement
Selection Criteria for Optical Transmitter Low consistency 0-2%Cs (0-20g/l) Paper machine Retention Measurement ( Head box, White water) Save-all filters, filtrate and superfiltrate Very low consistencies: 0-0,02%Cs ( 0-200mg/l ) Effluent plant
Microwave consistency transmitters KC/7 Latest Microwave technology
Microwave technology Total consistency measurement Measures fibers and fillers Unaffected of wood species change like pulp grade, fiber length, freeness, brightness, colour, shives Unaffected of process conditions change like flow rate, pressure, temperature, turbulence One calibration line for all kind of pulps No moving parts No preventive maintenance needed
Measurement principle Microwave is transmitted to pulp through ceramic antenna Microwave speed depends on material between antennas Measures any organic or inorganic material mixed with liquid Response is naturally linear Transmitter Receiver Microwaves travel faster in pulp than in water.
Selection Criteria for Microwave Transmitter Superior accuracy compared to shear force transmitters - Needed minimum 150 kpa pressure ( 22 psi, 15mH 2 O) - High conductivity >20mS/cm prevents measurement (pulp mill bleaching applications) Measures total consistency, fibers & fillers Variation in fiber mix, short fiber/long fiber, freeness etc. Mixing Chest and Machine Chest applications Recycled pulps, excellent for unscreened applications like after pulper Before de-inking Effluent plant before thickener
Transmitter selection
Contact your supplier, fill questionnaire We help you to select correct measurement technology
General Recommendations for good consistency measurement and control Select Cs transmitter by application, not by price Design Cs loop to work well - tune loop Proper tank agitation is critical Constant dilution water pressure Dilution water injection point and correct dilution water velocity Dilution valve dimensioning
Retention Measurement and Control KRA Retention Measuremenent
First Pass Retention calculation in DCS KRA Retention Measurement Retention is the Yield of Paper Machine wire section Pulp Headbox Paper Wire White Water Total Retention % = Tot Cs HB Tot cs WW Tot Cs HB *100 % Ash Retention % = Ash Cs HB Ash cs WW Ash Cs HB *100 % September 20, 2018 Slide 27
KRA Retention system and control Headbox Cs % and Ash Cs % 4-20mA Head Box DCS Calculation: DCS Fan Pump White Water Retention% = CS HB CS WW X 100% CS HB SP White Water Total Cs 4-20mA 4-20mA White Water Retention Consistency Chemical Control Flow Control White Water Cs % and Ash Cs % Retention chemical September 20, 2018 Slide 28
Typical Advantages of Retention monitoring and Control Understanding what happens in the Wet End Improved wet-end stability Variability reduction of paper quality Reduced downtime due to sheet breaks Smoother transitions and faster grade changes No maintenance required so far with first installations. September 20, 2018 Slide 29
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