Flow Instrumentation Solution for the Pulp and Paper Industry
Application Description
Pulping covers raw material preparation, cooking, washing and screening, bleaching and thickening; papermaking covers refining and blending, sizing, filling and the paper machine. Electromagnetic flowmeters serve every stage of both processes and are the primary instruments for liquid flow measurement in pulp and paper mills.
Mills are highly sensitive to flow measurement: stock ratio governs basis weight, steam accounts for a large share of energy per tonne of paper, and instrument failure can slow or stop an entire line. Pulping media add four core challenges - alkaline cooking liquor corrosion, impact wear from fibres and grit, scaling deposits and high-consistency abrasion. No single model covers all duties.
Application Focus
Pulp and paper media are mainly stock, alkali, black liquor and lime mud, which combine corrosion, solids, scaling and abrasion - the core difficulty in instrument selection.
1. Corrosion: cooking liquor is an alkaline system (Ca(OH)2/NaOH), calling for high-temperature PFA liners and corrosion-resistant electrodes, preferably remote mounted.
2. Solids: fibres and grit abrading the electrodes introduce measurement noise, causing signal fluctuation and disturbing stable control loop operation.
3. Scaling (deposition): at low velocity or in long campaigns, media settle on the tube and electrodes, reducing the bore and attenuating the signal.
4. Abrasion: mechanical pulp reaches up to 10% consistency, while black liquor and lime mud are abrasive; high velocity wears measuring parts and adds flow noise.
5. Metering accuracy: repulping, refining and blending require ratio fluctuations within ±2% to hold basis weight; refining runs under PID closed-loop control.
Solution Overview
The four duties above are met through liner and electrode material selection supported by signal processing and sealing design - one system covering material resistance, noise immunity, scaling protection and high-temperature protection.
1.Wear Protection
Accept stock uses PFA liners; medium-consistency coarse stock and rejects use the more abrasion-resistant ETFE. For high-velocity black liquor and lime mud, a replaceable metal guard ring at the liner inlet takes the wear first and extends service life. Electrodes use a tungsten carbide coating on a stainless steel substrate to reduce noise from particle impact.
2.Signal Noise Suppression
Multi-frequency excitation with DSP digital filtering removes stock-induced interference, while functional magnetic field technology suppresses the effects of eddy currents and partially filled pipes.
3.Scaling Protection
A proven flat plus cone double seal is combined with polished and chemically modified electrodes to slow scaling. Low-friction PFA liners limit deposit adhesion, and the MFD series high-impedance circuit reaches 10¹² Ω, reducing scaling-induced interference to roughly 1/100 and measuring media down to 1.7 μS/cm.
4.High-Temperature Protection
Cooking reaches about 180 °C. High-temperature PFA liners rated -80 to 260 °C, with remote mounting, keep the converter below 65 °C. MFD coils are driven up to 200 Ω and remain stable at 105 Ω coil impedance at 180 °C, while an internal steel mesh resists deformation from vacuum and thermal cycling.
5.Steam Metering
The VFE series vortex flowmeter integrates temperature and pressure compensation. Dual sensors reject plant vibration, and FFT power spectrum analysis extends rangeability, giving mass flow accuracy to 1%.
6.Breakdown by Process Stage
(1)Raw material preparation and repulping: clean water and stock at ambient temperature - MFC / MFE-S electromagnetic flowmeters, with the RFC metal tube rotameter for low flows.
(2)Cooking: alkaline cooking liquor up to about 180 °C and highly corrosive - MFD high-impedance electromagnetic flowmeter with a high-temperature PFA liner, remote mounted.
(3)Washing and screening: fibre-laden stock and black liquor, moderately abrasive - MFD electromagnetic flowmeter with an ETFE liner and tungsten carbide coated electrodes.
(4)Bleaching and thickening: bleach effluent and thickened stock, highly corrosive - MFE-S electromagnetic flowmeter with a PTFE/PFA liner and corrosion-resistant electrodes.
(5)Refining and blending: medium-consistency stock with ratio fluctuations within ±2% under PID control - MFE-S multifunction electromagnetic flowmeter for consistent multi-loop measurement and fast response.
(6)Paper machine (wire, press, dryer, calender, reel): clean water and white water circuits carrying fibres and fillers - electromagnetic flowmeters, with the SFC ultrasonic flowmeter on large lines where cutting the pipe is impractical.
(7)Steam and heat: steam metering over a wide range with temperature and pressure compensation - VFT vortex flowmeter with integrated compensation.
Customer Value
A single-source flow instrumentation portfolio delivers stable liquid and steam measurement across all process stages under the duties typical of pulp and paper: alkali corrosion, fibre abrasion, scaling and signal interference.
Less wear, clogging and scaling reduce maintenance workload and unplanned shutdown risk, while stable stock ratios hold basis weight and cut reject losses.
Dependable flow data supports plant-wide material balance, energy accounting and granular cost control, underpins closed-loop automation, and improves both product quality and operating efficiency.
Related Products
1. MF Series Electromagnetic Flowmeter
Cooking, washing and screening, bleaching and thickening, refining and blending, and white water circuits.
2. VF Series Vortex Flowmeter
Steam metering, compressed air and process gases.
3. RFC Series Metal Tube Rotameter
Low-flow dosing of chemicals and stock additives, and low-flow white water measurement.
4.DF Series Differential Pressure Flowmeters
Including standard orifice, multi-hole balanced orifice, nozzle, wedge, V-cone and Venturi tube, for steam mains, large-bore water and dilute stock, and recovered white water.
