The Heat robbers ! 80% steam 3% distribution losses 77% Unburnt Stack Blowdown Process consumption 57% 100% fuel energy (Condensate & Flash) 20%
How does one measure Specific Energy Consumption ? -kg of fuel per kg of Paper -kg of steam per kg of Paper or kg of Steam/kg of water evaporated -Kw-h / Tonne of Paper -Kcal/ kg of water evaporated? -Total equivalent Energy/ Tonne of Paper ? Gj/Tonne of Paper? Energy Management Seminar for Vietnam Paper Mills , Ho Chi Minh City , May 2008
How does one Reduce Specific Energy Consumption ? -Obviously minimise the Losses ( Boiler losses, Distribution losses) - Enhance Condensate Return & Recover Flash Steam - Improve the Process heat Utilisation ( Heat Transfer rate) EPIC Educational program – Saving Energy Cost by increasing Boiler and Steam system Efficiencies
Specific Steam Consumption on Indian Machines • Which is more representative ? Kg of steam / kg of Finished production OR kg of steam /kg of water evaporated ? • Typical good values • • • Newsprint 1. 6 - 1. 7 Wr/Pr (NS) 1. 6 -1. 7 Wr/Pr (SS) 1. 9 -2. 0 Kraft 1. 5 - 1. 9 Paper Board 2. 1 -2. 3 Tissue 2. 5 -2. 6 • Kg of steam/ water = 1. 35
Basic Principles of reducing energy consumption • Reduce Temperature of any exhausts in Boiler House • Minimise Amount of water evaporated in drier section • Minimise Steam condensed outside driers • Maximise Condensate return and pressure • Minimise Electrical consumption of drives/pumps • Monitor and Manage Energy Consumption trends & costs.
The No. 1 Rule for energy conservation • You cannot control what you cannot measure
Factors affecting Specific Steam consumption. . 1 • Furnish Type • No. of Driers /Material • Stock Freeness • Design of steam and condensate system • Dryness off Press • Condensate evacuation efficiency • Stock Temperature • Extent of Flash steam recovery • Felt tensions • Type of Siphon/clearances • Paper breaks/idling • Presence of non condensibles/air
Factors affecting Specific Steam consumption…. 2 • Type of Hood and Controls • Hood doors open/closed • Sizing of Thermocompressors • Differential Pressures across Driers • Number of driers connected to Condenser • Finally the Degree of Automation
Need for Automation in Steam Systems Upgrade to Efficient Steam /Quality Control systems. • The Need to Produce High Quality Paper • The Need to run machines faster • The Need to minimise Cost of Manufacturing • The need to jump productivity and Energy efficiency All of these have forced mills to look at improving their systems and Automation is one of the strategies.
Steam Generation -Minimum Cost of Steam generation • Monitoring real time Efficiency of the Boiler • Tracking Losses in Boiler • Both Direct and Indirect Efficiency • Steam to Fuel Ratio for Different Loads • Online Excess Air control • Boiler House Management system with objective to minimise steam generation cost Specialist in process efficiency & energy conservation
Steam Distribution – Minimising Losses Delivering Steam at the Right Pressure and Temperature to Paper machine is essential Steam should be Dry Saturated at Drier Inlets This means that Steam conditioning is essential Minimising Pressure Drops in lines Correct Drain Trapping is essential to prevent steam wastage. Specialist in process efficiency & energy conservation
Steam Utilisation- Energy Efficiency of Paper Machine Drying Paper Uniformly at normal steam pressures Removing Condensate from Driers efficiently Returning Condensate to Boiler house Flash Steam Recovery Steam Response to Final Moisture Value Specialist in process efficiency & energy conservation
Heat Transfer in Cylinders Moisture Paper sheet Steam in Condensate out Condensate in Siphon Drier Cylinder Felt Paper Air gap Steam Condensate Air layer
Needs for Efficient Steam and Condensate system • • Steam at the Right Pressure , Saturated and Dry Correct syphon selection and clearance Adequate Differential Pressure Venting of Non- condensibles/Air 100 % Recovery of Flash Steam/ Blow thru Minimising leakages thru rotary joints Adequate Thermal insulation Adequate Steam Trapping on distribution lines
Hood & Pocket Ventilation. Automation for Efficient operation Felt PV Ventilation Cylinder Roll
Hood & Pocket Ventilation. Controls Hood provides Consistent Drying environment Hood also provides Energy efficiency 10 -12 % saving in Steam is possible using Closed Hoods Pocket Ventilators can increase production by 5 -8% Controls for : a) Pocket Ventilation Temperature Control b) Dew Point Control /Exhaust Humidity c) Zero Level Control for minimum leakage air. Specialist in process efficiency & energy conservation
The Link Between Steam and Quality Uniform Drying is possible only with a Stable steam and condensate system. Poor Moisture profiles can result due to Poor condensate evacuation or poor Hood /PV air circulation apart from others Popereel Moisture controlled by Steam Specialist in process efficiency & energy conservation Valves in Drier Section
Where do we begin ? First Start with installing accurate meters for Steam /condensate/electricity • The Small Things – – – – Check for leaking traps and replace immediately Check Syphon tips and clearances Check for Rotary Joint seal failures /leakages Check for excessve DP set points Check for obvious leakages Check Excessive Steam pressure Install Airvents and sightglasses • The Larger things Leading to Automation – – – Control Exit moisture from Presses Installing Thermocompressors Control Valve and DP automation Changeover to correct syphons Install Drier Diagnostic systems Hood controls
Mathematical Model & Simulation Software of Paper Drying process Reduces Production Loss Generates set points for process parameters in dryer section Dry. Max Improves Web Runnability and Paper Quality Optimises Paper Drying Efficiency Trouble Shooting & Supervisory tool for paper machine
Dry. Max Controller Comparison of Measured parameter value with Set. Point generated by Dry. Max Parameters Monitored & to be Controlled: Surface Temperature of dryer cylinders Temperature of paper sheet Moisture content of paper sheet Evaporation rate of water from the paper surface Steam Paper In Paper Out Condensate
Summary Automation pervades every aspect of Steam in a Paper Plant To operating Efficient Boilers To World Class Steam and Condensate systems of Paper machines To Energy Efficient Hoods and PV systems To Robust Quality Control systems integrated with Steam systems Specialist in process efficiency & energy conservation
Whatever be the Automation……. . The Ultimate Objective is to have the Lowest Specific Steam Consumption for your plant Is your Plant close to world class levels of Energy Efficiency ? Specialist in process efficiency & energy conservation
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