Co-funded by the Intelligent Energy Europe Programme of the European Union 1 Co-funded by the Intelligent Energy Europe Programme of the European Union Introduction - Theory - Exercises - Business Case - Summary
May 06, 2015
Co-funded by the Intelligent Energy Europe Programme of
the European Union 1
Co-funded by the Intelligent Energy EuropeProgramme of the European Union
Introduction - Theory - Exercises - Business Case - Summary
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the European Union 2
Overview
Introduction Theory
Approach (some remarks) Main components Compressed air flow rate Inappropriate air users Leakage Parameters that influence
consumption
Exercises Business Case Summary
Introduction - Theory - Exercises - Business Case - Summary
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AIR IS FREE….BUT COMPRESSED AIR ISN’T FREE
ENERGY EFFICIENCY OF MOST
OF COMPRESSED AIR PLANTS IS
QUITE LOW
COMPRESSED AIR CAUSES A COST THAT ISN’T
ALWAYS TAKEN IN ACCOUNT
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Electric energy costs
Leakage costs
Maintenance cost
Plant modification cost
The costs of electric energy reach the 73% of total cost
during the life of air compressed system.
REASONS FOR EXCESS
COST
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Reasons for exces consumption
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Optimizzation of air compressed system will deliver savings of up to 35 %.
Introduction - Theory - Exercises - Business Case - Summary
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Approach (some remarks)
1. Identify how much air flow and pressure each user machine needs
2. Find the right place for each user machine
3. Identify the right place for compressed air machines
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MAIN COMPONENTS
1. Air inlet filter
2. Air compressor, electric motor and panel
control
3. Air treatment (oil separator, dryer, filtration)
4. Storage tank
5. Distribution Network
Fonte: Improving air system performance DoE - Energy Efficiency and Renewable Energy
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Compressed air flow rate
- inappropriate air users
- leakage
The flow rate produced a direct bearing on consumption.
The compressed air flow rate depended on requirements.
Therefore must be avoided:
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Inappropriate air users
Transport of powders at low pressure
Ventilation
Agitation liquids
Cleaning in general
Removal of defective products from a line
Blowers
Mechanical arm
Electrobrushes
Mechanical agitators
Fans; Blowers
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LEAKAGE
• Accurate assessment with specific equipment
• Rough estimate
If more than 5% requires action!!
How to assess the losses?
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Parameters that influence consumption
• L is the work
• M is the mass flow rate of air
• R is the universal gas constant,
• T1 is the inlet air temperature (°K),
• β is the ratio between the compression end pressure and beginning of compression,
• m is the exponent of the transformation,
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Choose an appropriate level
The increase of a bar of produced air pressure causes an
increase of about 7% of the energy consumption
The increase of a bar of produced air pressure causes an
increase of about 7% of the energy consumption
If the process requires two pressure levels is good to evaluate the installation
of two compressors instead of one (with the need to achieve the lowest
pressure by reducing valves).
Parameters that influence consumptionMaximum pressureMaximum pressure
The operating pressure of a compressor directly affects the power consumption and
energy consumption.
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• Increase in operating costs
• Small diameters, lower installation costs, more losses and hence higher
operating costs
The pressure drop of the network (pipes) should never result in a pressure
drop greater than 0.1 bar
• The level of surface finish of the tubes affects the load losses
Parameters that influence consumptionPressure dropPressure drop
The pressure drop of the network (pipes) should never result in
a pressure drop greater than 0.1 bar
The pressure drop of the network (pipes) should never result in
a pressure drop greater than 0.1 bar
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• The minor work is assured in the case of an isothermal transformation m = 1
• The work is greater in the case of an adiabatic m = 1.4
Parameters that influence consumptionType of transformationType of transformation
To get closer to an isotherm must carry away heat during
compression
To get closer to an isotherm must carry away heat during
compression
The removed heat can be used
• Only 10% of the electricity consumed by a compressor is converted into
useful energy to compress the air
• 90% of the electrical energy is converted into heat to be eliminated, but that
can be recovered (heating environment, pre-heat combustion air, heating hot
water, pre-heat process water)
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The work made by the compressor for compressing the air increases with
increasing temperature of the inlet
• The temperature of the input should be as short as possible, consistent with
current environmental conditions
• Do not take air from the compressor room or another, it is always best to take
air from the outside
• The starting point must be taken possibly in the north and in the shaded area
Parameters that influence consumptionInlet air temperatureInlet air temperature
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The air quality depends on its content:
• Particulate.
• Water (expressed in temperature of the dew point of the air pressure)
• Oil (measure)
• Material of the network and its state
Parameters that influence consumptionAir qualityAir quality
Air quality must be adapted to the needs of the process
Air quality has a greater cost.
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WaterThe water comes from atmospheric moisture in the airRemoving water from the air can be done:
- At central Referigeration- At the local level Steam Traps
The refrigeration is more efficient, but more expensive from the point of view of plant and exercise.The steam traps have a lower cost of installation, but require higher maintenance costs and leads to losses of air.
Parameters that influence consumptionAir qualityAir quality
Particulate matter can be removed by input filters
The oil can be removed by filters or at the source, using oil-free compressors.The two solutions should be evaluated as a function of the different costs.
The oil-free compressors increase the cost of installationThe filters increase the costs of operation and maintenance
The filters should be checked regularly
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1. Start - stop (power 5-10 kW)
2. Running load - idling - stop (power> 10 kW)
3. Speed control of Compressors
Regulation system are influenced by:
• Oversized Compressor
• Control of the compressor speed
• The presence of a storage tank
Parameters that influence consumptionRegulation systemRegulation system
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•Meets sudden demands for air
•Allows for greater stability in the level of pressure on the network
•Reduces Stop & Go of the compressor
•Provides sizing the compressor below the maximum values pressure
• The option of installing secondary tanks near the isolated users and / or highly
intermittent can be consider
Sizing of the storage tank
•The size of the tank depends on the extent of changes in the demand for air.
The size should be at least 10 times the volume of air produced by the
compressor (l/s)
•The size of the tank affects the sizing of the compressor
Parameters that influence consumptionSTORAGE TANKSTORAGE TANK
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• Do not oversize the compressor
• Storage Tank
• Control of the compressor speed
• Type of compressor
• High efficiency engine
Parameters that influence consumptionCompressor & controlCompressor & control
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Acquisition of data on consumption of electricity
• Can I make special measures? (High cost, more accurate)
• Can I use the data available? (low-cost, lower precision)
Parameters that influence consumptionHow to handle the compressed air systemHow to handle the compressed air system
Evaluate the cost of compressed air
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LEAKAGE REDUCTION
What is the effect of a hole of 10 mm in a compressed air network (@ 7 bar pressure)
Introduction - Theory - Exercises - Business Case - Summary
a.Up to 10 kW loose
b.Up to 40 kW loose
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HOLE (mm)
Flow rate @ 7bar (l/s)
Power loss (kW)
1 1,2 0,4
3 11,1 4
5 31 10,8
10 124 43
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LEAKAGE REDUCTION
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HIGH EFFICIENCY ENGINES
How much to save by replacing a standard engine with a high efficiency engine?
a. Up to 1%
b. Up to 5%
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Power [kW]
HIGH EFFICIENCY MOTOR
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REDUCTION OF AIR SUCTION TEMPERATURE
How much energy savings can be obtained with the cooling air inlet 5°C?
a. Up to 2%
b. Up to 10%
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Technical literature reports that a
reduction of 5 °C of compressor input
air temperature (with respect to usual
temperature) would allow saving of 2%
of yearly consumed kWh.
REDUCTION OF AIR SUCTION TEMPERATURE
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Practical examplePorsche industry
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Description:
In 1997, the system of compressed air production of "plant2 " of the German
automobile factory Dr. Ing hc F. Porsche AG near Stuttgart was constituted by a
screw compressor - cooled water (22,2 m3/min, FAD) plus four reciprocating
compressors water cooled from 15 m3/min each.
The maximum operating pressure was 8.7 bar.
An analysis on the compressed air system, carried out by specialists of a factory
compressors, noted compressed air demand varies between 15 and 65 m3/min.
By processing all relevant data has been defined a new compressed air system
with optimized use of energy.
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Action taken:
The new system was divided into two stages comprising only air-cooled screw
compressors.
Load peaks were satisfied with the use of three machines with a 5.62 m3/min
FAD each, while the base load was covered with four compressors with a FAD of
16.4 m3/min each.
All seven compressors are managed by a centralized control system.
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Results:
The optimization of the compressed air system allowed us to calculate the cost
of energy and make energy savings.
the operating pressure was lowered from 8.5 to 7.5 bar and the specific power
of the overall compression station has been reduced from 8.19 to 6.19 kW /
(m3/min).
The total savings amounted to 483000 kWh of electricity per year.
Furthermore have been spared approximately € 55,000 in savings for non-
consumption of cooling water.
The optimization of the compressed air system has been realized with a
reasonable payback time
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Excess energy consumption through compressed air is
caused by technichal as well as behavioural issues.
Through the optimization of the compressed air plant
savings of up to 35 % are possible.
The leakage reduction can effect up to 20 % energy
saving.
Adoption of high efficiency engines can effect up to 5 %
energy saving.
A reduction of 5 °C of compressor input air temperature
would allow saving of 2% of yearly consumed kWh.
Repetition
Introduction - Theory - Exercises - Business Case - Summary