Date post: | 17-Dec-2015 |
Category: |
Documents |
Upload: | blaze-wilkins |
View: | 222 times |
Download: | 2 times |
The Heat robbers !
100% fuel energy
80
% s
tea
m3% distribution losses
77%
Process consumption 57%
20%
UnburntStackBlowdown
(Condensate & Flash)
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 = 1.3-1.35
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.
Factors affecting Specific Steam consumption..1
• Furnish Type
• Stock Freeness
• Dryness off Press
• Stock Temperature
• Felt tensions
• Paper breaks/idling
• No. of Driers /Material
• Design of steam and condensate system
• Condensate evacuation efficiency
• Extent of Flash steam recovery
• Type of Siphon/clearances
• 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.
Specialist in process efficiency & energy conservation
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
Heat Transfer in CylindersHeat Transfer in CylindersHeat Transfer in CylindersHeat Transfer in Cylinders
SteamAir gapPaper
Felt
Cylinder
Condensate Air layer
Moisture Paper sheet
Steam in
Condensate out
Condensate in Siphon Drier
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
RollCylinder
PV Ventilation
Felt
Hood & Pocket Ventilation-Hood & Pocket Ventilation-Automation for Efficient operation Automation for Efficient operation
Hood & Pocket Ventilation-Hood & Pocket Ventilation-Automation for Efficient operation Automation for Efficient operation
Specialist in process efficiency & energy conservation
Hood & Pocket Ventilation-Hood & Pocket Ventilation-Controls Controls
Hood & Pocket Ventilation-Hood & Pocket Ventilation-Controls 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.
The Link Between Steam and Quality
Specialist in process efficiency & energy conservation
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
Valves in Drier Section
Where do we begin ?
• 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
First Start with installing accurate meters for Steam /condensate/electricity
Reduces Production
Loss
Improves Web
Runnability and
Paper Quality
Trouble Shooting & Supervisory
tool for paper
machine
Optimises Paper Drying
Efficiency
Generates set points for
process parameters in dryer section
Mathematical Model &
Simulation Software of Paper Drying
process
DryMax
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
Comparison of Measured parameter value with Set-
Point generated by DryMax
Paper In
Controller
Paper Out
Steam
Condensate
DryMax
Summary
Specialist in process efficiency & energy conservation
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