Opportunities to Improve Energy Efficiency on paper machine Dr. Vivek Kumar Department of Paper Tech - PowerPoint PPT Presentation

1 / 71
About This Presentation

Opportunities to Improve Energy Efficiency on paper machine Dr. Vivek Kumar Department of Paper Tech


The paper mill area is a major energy consumer in most ... to fabricate separate lines for two vacuum pumps and reduce the rpm 500 from present 550 rpm. ... – PowerPoint PPT presentation

Number of Views:1066
Avg rating:3.0/5.0
Slides: 72
Provided by: Piy


Transcript and Presenter's Notes

Title: Opportunities to Improve Energy Efficiency on paper machine Dr. Vivek Kumar Department of Paper Tech

Opportunities to Improve Energy Efficiency
on paper machineDr. Vivek KumarDepartment of
Paper TechnologyIIT Roorkee, Saharanpur Campus
  • The paper mill area is a major energy consumer in
    most integrated pulp and paper mills.
  • Energy consumption and cost per ton vary widely
    on paper machines.
  • Mills have different energy costs based on mill
    configuration, vintage of papermaking equipment,
    geographic location, and other parameters.
  • Each mill needs to develop an understanding of
    energy cost factors before preparing an effective
    energy reduction program.

  • Techniques for improving energy efficiency on
    paper machine i.e., Forming Section, Pressing
    section, Drying section.
  • Optimize performance of equipment.
  • Use steam, water, air, and vacuum pressures
    appropriate to processes.
  • Minimize energy losses.
  • Minimize water evaporated in the dryers.
  • Heat Recovery.

Forming section
Vacuum system
  • The vacuum system is among largest process in the
    paper mill with respect to space requirements,
    piping, and energy usage. Vacuum systems can have
    installed and required energy of 500 to 8,000 hp.
  • Several steps are required to guarantee the
    vacuum system is operating as efficiently as
  • Vacuum system audits or surveys.
  • Routine maintenance of vacuum pumps and auxiliary
    equipment, including belt and gear drives and
  • Replacement and calibration of gauges and process

How do we control or minimize wasted energy?
  • Vacuum system audits
  • Once identified, some vacuum system problems
    may cause higher energy usage, costs, and
    inefficiencies for the entire system.
  • Hot seal water.
  • High seal water flow due to unregulated or high
    seal water pressure.
  • Back pressure on the vacuum pumps due to system
    design or operational problems.
  • Synchronous vs. induction motors, which may
    affect the power factor.

Vacuum system........
  • Elevated seal water will reduce vacuum pump
    efficiency and will lower vacuum system capacity.
  • However, there are methods to reduce seal water
    consumption without sacrificing vacuum pump
    performance. This can involve a water recovery
    plan and/or cooling the water with a cooling
    tower. It is important to note that special,
    dirty-water cooling towers have been successful
    in this application.

Vacuum system........
  • We must have to maintain a vacuum system in such
    a way that it should not have more than 1 psig of
    back pressure measured at the pump discharge.
  • Also we have to maintain the system clean and the
    scale build up as minimum as possible.
  • In systems where a discharge sump is used, high
    water levels within the sump can cause back
    pressure as well as contribute to poor air/water
    separation within the sump.

Vacuum system........
  • Another issue involving motors is the selection
    of the motor size with respect to the vacuum pump
    horsepower. Many mills elect to install oversized
    motors on equipment to reduce spare parts and
    storeroom inventory. Many vacuum pumps are
    installed and driven with a motor from an old
    refiner that may have 50 more horsepower than
    the vacuum pump requires.
  • A frequent practice is to replace a correctly
    sized drive motor with a larger size to eliminate
    overloading and trip-out problems. This is an
    example of correcting the symptom rather than
    solving the problem.

Vacuum system........
  • Older, inefficient vacuum pumps versus new,
    modern designs
  • Scale build-up
  • Process carryover and high seal water flows
  • Piping losses or poor system design.

Vacuum system........
  • Newer larger pumps can reduce the quantity of
    pumps on a paper machine by one half.
  • Scale, or calcium carbonate buildup, will
    increase vacuum pump horsepower requirements by
    as much as 20 to 30 and often locks up the
    rotor within the vacuum pump.
  • Water treatment and descaling programs are useful
    in the prevention of scaling. Recirculated seal
    water systems with cooling towers, have
    experienced better control of the water quality
    for the vacuum pumps.

  • Case Study

Vacuum system........
  • In one audit it is mentioned as, the total vacuum
    system power consumption was 3,040 hp. Allowing
    for performance tolerances and drive losses, the
    system should require only 2,775 hp. This
    excessive power consumption of 265 hp was due to
    several factors affecting. The problems included
    overloading due to high seal water flows and
    internal scaling.
  • Vacuum pump operated at 11.3 in. Hg,
  • Highest vacuum level of the was 7.0 Hg. The
    extra horsepower to operate the vacuum pump at
    11.3 in. Hg required an additional 34 hp

  • Another vacuum pump was requiring 36 hp more than
    necessary due to the incorrect model being
    installed. This was a high vacuum model, designed
    for more efficient operation at above 15 in. Hg.
    However, the pump was on the low vacuum press
    zone and operated at only 7 in. Hg. A low vacuum
    model needed to be installed to reduce
  • By making some changes in felt conditioning,
    there was an opportunity to save an additional
    108 hp.

Replacement of Existing Vacuum Pumps
  • Current Situation
  • In Paper machine No. 1 two vacuum pumps
    (capacity 1800 m3/hr rated vacuum 400 mm Hg
    each) are provided and having common header (i.e.
    for Flat Boxes uhle Boxes) and consuming 107
  • Suggestion Benefits
  • As the suction vacuum requirement is only 200
    mm Hg. It is recommended to install a new vacuum
    pump of higher capacity (rated suction vacuum 300
    mmHg, capacity 3500 m3/hr) in place of existing 2
    vacuum pumps, which will consume about 65 kWh.
    Saving potential is 107 65 42 kWh or Rs. 8.05
    lacs/annum against investment of Rs. 3.00 lacs.

  • Situation Current
  • In Paper machine No. 2 two vacuum pumps
    (capacity 1800 m3/hr rated vacuum 400 mmHg
    each) are provided and having common header (i.e.
    for Flat Boxes uhle Boxes) and consuming 77
  • Suggestion Benefits
  • As the vacuum requirement is only 200 mmHg.
    It is recommended to install a new vacuum pump of
    higher capacity (rated vacuum 300 mmHg, rated
    capacity 3200 m3/hr) in place of existing 2
    vacuum pumps, which will consume about 56 kWh.
    Saving potential is 77 56 21 kWh or Rs. 4.02
    lacs/annum against investment of Rs. 3.00 lacs.

  • Current Situation
  • In paper machine No.4 one vacuum pump (KVM
    900 capacity 3600 m3/hr, Rated vacuum 500 mmHg)
    has been installed for uhle Box, which is
    consuming 104 kWh.
  • Suggestion Benefits
  • As the requirement of suction vacuum in
    uhle Box is around 200 mmHg. It is suggested to
    convent it as per the specification i.e. Capacity
    4125 m3/hr, Rated vacuum 300 mmHg. At these
    specification the power consumption will be about
    70 kWh. Therefore saving potential is 104 70
    34 kWh resulting in saving of Rs. 6.5 lacs/annum
    against investment of Rs. 5.00 lacs.

  • Current Situation
  • In paper machine No.5 one vacuum pump (7LV
    Capacity 1410 m3/hr, Rated vacuum 660) has been
    installed for flat boxes, which is consuming 48.7
    kWh power.
  • Suggestion Benefits
  • As the requirement of suction vacuum is only
    200 mmHg in flat boxes, it is suggested to
    replace existing vacuum pump with KVM 300
    (Capacity 1500 m3/hr, Rated vacuum 300 mmHg),
    which will consume only 24.5 kWh power. Therefore
    saving potential is about 48.7-24.5 24 kWh
    resulting in saving of Rs. 4.6 lacs/annum against
    investment of Rs. 2.00 lacs.

  • Current Situation
  • In the paper machine No.7 four vacuum pumps
    (all KVM 600) are running continuously and
    having common header for Couch, suction press,
    flat boxes uhle box. Requirement of suction
    vacuum in Couch and suction press is high i.e.
    upto 400 mmHg and in Flat Box and uhle Box, it is
    less i.e. 200 mmHg. All the four pumps are
    consuming about 273 kWh power.
  • Suggestion Potential
  • As the requirement of suction vacuum is
    less in case of Flat Boxes and uhle box it is
    recommended to fabricate separate lines for two
    vacuum pumps and reduce the rpm 500 from present
    550 rpm. A saving potential of 14 kWh is
    estimated against reduction of rpm resulting in
    saving of Rs. 2.7 lacs with an investment of Rs.

  • Improvement Effect(A) Rs. 32.96 lacs/annum
  • Investment (B) Rs. 13.50 lacs
  • Simple Pay Back (B/A) 5 months

Energy Efficient Formers
  • Twin wire forming is new principle had the
    advantages of avoiding the free surface between
    mix and air, of increasing the dewatering
    capacity by allowing dewatering capacity through
    two wires.
  • The forming sections is very short and the
    formation takes place in a fraction of the time
    it takes for a Fourdrinier machine.

  • Produces a paper of equal and uniform quality at
    a higher rate of speed. Coupling the former with
    a press section rebuild or an improvement in the
    drying capacity increases production capacity by
    as much as 30.
  • Energy savings come from reduced electricity
    consumption . The technology also may improve
    quality and electricity savings of 41 kWh/t of

High consistancy forming
  • In high consistency forming, the furnish (process
    pulp) which enters at the forming stage has more
    than double the consistency (3) than normal
    furnish. This measure increases forming speed,
    and reduces dewatering and vacuum power
  • Electricity savings are estimated at 8 that is
    about 41 kWh/t of paper.

Pressing section
  • Drying the sheet of paper using steam heated
    dryers is a lot more expensive than using
    efficient presses. The primary function of the
    press section therefore is to remove as much
    water from the sheet as possible, consolidate the
    sheet and improve the surface smoothness.

Extended nip press (Shoe press)
  • The additional pressing area allows for greater
    water extraction, (about 5-7 more water removal)
    to a level of 35-50 dryness.
  • This technology reduces the load on the dryer, it
    allows plants to increase capacity up to 25 in
    cases where the plant was dryer limited.
  • Extended nip pressing also increases wet tensile

Hot pressing
  • Pre-heating the water in the paper sheet before
    pressing can reduce the evaporation load.
  • Use of steam showers has been estimated to reduce
    the steam requirement by 1 kg of steam per kg
    paper. We estimate steam energy savings of 0.61
    GJ/t paper through hot pressing.

  • Case Studies

  • Installation of Steam Boxes in the Press Sections
  • Current Situation
  • There are no steam boxes installed in the
    press section
  • Suggestion
  • With the Installation of steam boxes the
    following optimizations are possible
  • Increase of production capacity or reduction of
    steam consumption in the dryer section
  • Improve moisture profile

  • In general the design data of steam boxes are
  • Steam consumption approx. 80 - 120 kg steam /
    tonne paper (the value depends on the dryness
    of the paper)
  • Potential of warming up the paper web from 10 to
    15 K
  • 10 K increase of paper web temperature
    corresponds with an increase of dryness after the
    press section of about 1
  • 1 increase of dryness after press section leads
    to 5 higher production or 5 less steam demand
    in the drying section
  • With the installation of steam boxes in the press
    sections of PM 4 and PM 5 the following steam
    reduction is possible-

  • PM 4 (3.26 t paper / hour)
  •       Steam consumption 3.4 t/t 11 t/h
  •       Steam saving in drying section 6 0.66
  •       Steam demand steam box 0.3 t/h.
  • PM 5 (2,6 t paper / hour)
  •       Steam consumption 3.9 t/t 10 t/h
  •       Steam saving in drying section 6 0.6
  •       Steam demand steam box 0.23 t/h.
  • Furthermore after installation of a steam box
    less evaporation (0.1 to 0.2 m³/h) occurs in the
    drying section which can reduce condensation in
    the pre-drier section of PM 5.

  • Improvement Effect (A) Rs. 21.0 lacs/annum
    in PM 4
  • (Steam reduction 2880 t/a)
  • Rs.
    21.6 lacs/annum in PM 5

  • (Steam reduction 2960 t/a)
  • Investment (B) 100.00 lacs / steam
  • Simple Pay Back (B/A) 5 years

  • Drying Section

  • To optimize energy use in the drying process, it
    is essential to clearly identify the areas and
    actions that offer measurable opportunities for
    improvement. Reducing the evaporation load to the
    dryer section is a smart starting point. Pressing
    improvements are the best way to reduce dryer
    section steam use.

  • Improving machine efficiency is another obvious
  • Identifying losses from the dryer drainage system
    is essential.
  • The cost of high-pressure steam should be
    factored into dryer energy cost.
  • Minimizing the dryer air heating requirement.

Improper siphon size
  • Replacing rotary siphons with stationary siphons
    in dryers that discharge directly to the
    condenser offers potential for improvement.
    Stationary siphons are designed for a blowthrough
    steam flow of 10 versus 20 to 25 often
    required with rotary siphons.
  • Proper siphon design is a key to keeping the
    system "tight".

Maximize the Use of Low-Pressure Steam
  • This allows the most electricity to be generated
    at the boiler house, using the high-pressure
    steam to power an electricity-generating turbine.
  • Using dry low pressure steam is advantageous when
    considering energy efficiency due to high
    condensing heat rate.

Minimize Dryer Air Heating Requirement
  • Adjust the pocket ventilation air temperatures to
    match the drying requirements and hood design.
  • The hood must be well sealed and have good
    insulation properties to operate with low pocket
    ventilation air temperatures.
  • Air to air heat recovery systems on existing
    machines recover only about 15 of the energy
    contained in the hood exhaust air. This
    percentage could be increased to 60-70.

  • Paper machines with enclosed hoods require about
    one-half the amount of air per machine reduces
    thermal energy demands since a smaller volume of
    air is heated. Electricity requirements in the
    exhaust fan are also reduced. Steam savings of
    0.76 GJ/t paper and electricity savings of 6.3
    kWh/t paper by installing a closed hood and an
    optimized ventilation system is estimated.

  • Case Studies

  • Stopping of steam condensate leakages from the
    pocket ventilation system
  • The Pocket ventilation system for dryer group
    (II) (III) consists of steam heaters for heating
    the inlet air. There are two rows of steam
    battery which operates on the steam pressure of
    3.5 Kg/ cm2 .

  • The condensate of steam is collected through
    bottom line in separate tank. It was found, that
    there was lot of steam and condensate leakages
    and all area below Pocket ventilation system
    nearby is flooded with condensate.
  • It is recommended that steam condensate
    leakages should be stopped immediately.

ECONOMICS Cost of 1 m3 condensate Rs. 60
(including heat value) Improvement Effect
Saving by stopping condensate
draining (5m3 daily) Approx 60 5 Rs.
300 wastage Annual Saving 300330 Rs.
99,000/- Investment Negligible Pay
back Immediate
Closing of side panels doors of dryer hoods of
both machines
  • Background
  • It was observed that the lifting doors of both
    machines are always partially lifted and all
    basement area is open.
  • The closed hood is therefore working as semi
    closed hood and lot of air infiltration is takes
    place from machine house.
  • This reduces the drying efficiency of dryers and
    hence more steam is consumed for drying the same
    quantity of paper. It also reduces the
    efficiency of pocket ventilation system and also
    increases steam consumption in PV system.

  • Beside this the condition of side panels of hood
    was not proper resulting in heavy Infiltrations
    from sides .
  • The insulation of side panels were also in bad
    shape. All these reduce the efficiency of hood,
    resulting in more power consumption at exhaust
  • Recommendation
  • It is recommended that machine should run with
    lifting door in down position.
  • The doors should be lifted only at the time of
    paper break and should be brought down after
    rethreading of paper.
  • Also all infiltration should be stopped and
    insulation of side panels and roof should be
    repaired / replaced.

  • By proper insulation, repairing and stopping
    infiltration of air in hood efficiency in drying
    will be improved.
  • By assuming 1 improvement in hood efficiency,
    mill can save 0.24 t/hr steam resulting in saving
    of Rs. 15.20 lacs/annum as shown below.
  •   1 improvement in drying 0.24 t/hr after
    reducing in steam consumption.

  • 0.24t/hr

  • 5.76T/day or 1900 T/annum

  • 1900 400
  •   Savings Rs. 15,20,320/-
  • Investment Rs. 5,00,000
  • Pay back 3 months

Insulation of Hot Surfaces in Paper Machine
  • During the audit at mill, it was observed
  • that various pipelines and Paper machine
  • dryers having higher temperature are not
  • insulated resulting in high heat losses
  • through these uninsulated insulated
  • surfaces in the form of radiations.

  • It is suggested to put proper insulation on all
    bare surfaces to reduce the heat loss through
    radiation and save the energy wastage.
  • Detail of Uninsulated lines

  • Benefits
  • By putting the insulation on the uninsulated
    surfaces enormous calories of heat energy can be
    saved, which is equivalent to a saving of 2127
    ton of steam per annum resulting in saving of
    Rs.8.51 lacs per annum with a payback period of
    2-8 months for putting the insulation.
  •  Economics
  • Improvement effect (B) Rs.
  • Investment Amount (A) Rs. 4.28 Lacs
  • Simple pay Back (B/A) 2-8 months

Replacing of the missing air filter panels and
cleaning of air filters .
  • It is recommended that air filter panel of PV
    system should be repaired and maintained in
    proper condition regularly. All missing filter
    panels should be placed in position and should
    be cleaned from dust.

  • By adopting this proposal, clean air will be
    purged in pocket ducts of dryer, reducing chance
    of dirty air to bleached paper.
  • This would improve the paper surface quality.
    Also the energy consumed by PV fan would reduces

Use of flash steam of main condensate tank in
pocket ventilation system
  • The condensate of last group dryers are
    collected in the main condensate tank from where
    it is pumped to boiler house.
  • It was observed that the flash steam from main
    condensate tank is vented to atmosphere.
  • Without recovering its heat value. About 80 kg/hr
    flash steam is vented.

  • It is recommended that this flash steam should be
    used in the steam battery of PV system. Since the
    flash steam is not sufficient for PV system, the
    live steam will also be used but the use of flash
    steam would reduce the use of live steam in PV
  • Assuming 2 tonne flash steam per day utilized in
    the PV system, mill can save Rs. 3.96 lacs/annum
    by using it in PV system.

  • Installation of Heat Recovery System in Paper
    Machine 5
  • Current Situation
  • The pre-dryer section of PM 5 is equipped with a
    closed hood
  • The current situation is as follows
  •    Daily production of PM 4 60 t/d
  •    Evaporation rate 4 m³/h (pre-drier
  •    Exhaust pre-dryer section 1 17530 kg/h
    68.3C / 51.2
  •    Exhaust pre-dryer section 2 14250 kg/h
    71.4C / 43.5
  •    Exhaust air mass flow 31780
  •    Supply air mass flow 21000
    kg/h(66 )
  •    Leak air mass flow
    10780 kg/h

Current Situation
17.530 kg/h 68,3C/51,2
14.250 kg/h 71,4C/43,5
29C / 33,3
Supply air for the hood coming from the hall
18.200 kg/h
Filter by-passed
Leak air from the hall into the hood
external air polluted
Exhaust air from the hood in the hall
Exhaust air from the vacuum system into the hall
50C/ 99/ 85,3 g/kg
  • There is no heat recovery system installed in the
    exhaust air system. The supply air (120C) is
    heated by live steam.
  • The supply / exhaust air proportion (66 ) is
    within the range of recommended values.
  • The filter in the external supply air system is
  • Furthermore wet exhaust air from the vacuum
    system is led into the basement. There is
    condensation in the hood when the hood is closed.

25C /49
70C 32,000 kg/h
44C 21,000 kg/h
  • To make hood closing possible and thus increasing
    the quality of paper it is suggested to increase
    the supply and exhaust air mass flows step by
    step (target values supply air mass flow 28,000
    kg/h / exhaust air mass flow 42,000 kg/h the
    target values might not be reached because of
    design of the existing air system).
  • This leads to an increase of electricity
    consumption but also to a reduction of steam
    consumption. It is estimated that these changes
    in energy consumption are not affecting the
    operational costs.
  • Furthermore it is recommended to lead the exhaust
    air from the vacuum system out of the hall and to
    lead the external supply air through the filters.

  • advances in drying

Impulse Drying
  • Impulse drying works by lowering the moisture
    content of the paper web entering the drying
    section by up to 38 percent. In a conventional
    papermaking operation, the web has a moisture
    content of 50 to 60 percent as it enters the
    drying phase.
  • It is estimated that the operation of 65 impulse
    drying units in the year 2020 could save 13
    trillion Btus of energy annually for the

Infrared drying
  • Along with improved energy efficiency, it
    increases the drying power output. Infrared
    dryers are powered by electricity, and require
    about 4.08 GJ of electricity/t paper versus 8.16
    GJ of steam/t paper for conventional steam dryers
    (Jaccard, Willis.). We therefore estimate primary
    energy savings of 3.3 GJ/t paper.
  • Investment costs for infrared dryer installation
    are Rs.5203/t paper including OM costs

Condebelt drying
  • This drying technique has the potential to
    completely replace the drying section of a
    conventional paper machine, with a drying rate
    5-15 times higher than conventional steam drying.
  • For large machines savings of 10-20 steam are
    possible (1.6 GJ/t of paper) and a slight
    reduction in electricity consumption (20 kWh/t of
    paper). Capital costs are considered to be high,
    although the size of the drying area can be
  • This provides opportunities to enhance energy
    economy. Energy for the Condebelt has three
    components primary steam used per kg of
    evaporated water, recovery of the latent heat
    from the steam evaporated from the web, and
    electrical energy.

  • Typical steam consumption is about1.31.5 kg per
    kg of evaporated water.
  • In the Condebelt process, about 85 of the heat
    can be recovered. Thus the temperature of the
    pulp entering the headbox can be increased by
    10C using the excess heat from the Condebelt.
  • The total electrical energy consumption in a
    Condebelt dryer is comparable to that found in
    conventional cylinder drying.

Air impingement drying
  • This technology can be combined with existing
    technologies. Heat input requirements have been
    modelled at 3 MJ/kg evaporated water, or a 10-40
    savings in steam requirements. Electricity
    requirements are expected to increase by 0-5.
  • This involves optimization of the geometry of the
    nozzle pattern, nozzle type ,nozzle
    velocitydiameter, nozzle to sheer distance.

Steam impingement drying
  • Steam requirements are estimated at 4.5 GJ/t
    paper with additional savings available if the
    latent heat from the purge steam is captured. De
    Beer, estimates a savings of 10-15, with a
    slightly lower reduction in electricity
    requirements (5-10).

  • Thank you

Avoid Idle running of motor of hood blower in
paper machine
  • Background
  • During the visit it was observed that motor of
    hood blower of paper machine was running idle
    without fan.
  • The shaft or connection between motor fan has
    been broken and motor runs continuously without
    fan for 24 hours.

  • It is recommended that proper maintenance
    should be taken care and all such system should
    be checked at least once a shift.
  • Assuming the motor running goes unnoticed for
    a day, Loss in electrical energy 30kW X24
  • Assuming 30 load 216 kWh/ day
  • Annual saving 216 1.61 330
  • 1.14

  • Investment Negligible
  • Savings Rs. 1.14 Lacs/annum
  • Pay back period with in one month

Motor considerations
  • Vacuum pumps are driven by induction and
    synchronous motors using v-belt drives and gear
    reducers, as required.
  • The use of synchronous motors is based on
    reliability, space considerations, and
    elimination of the need for power transmission
    equipment (v-belt drives and gear reducers).
  • Also it is observed that some mills elect to use
    higher speed synchronous motors (1,200 or 1,800
    rpm) and gear reducers that may offer cost
    savings over the larger, slow speed synchronous

  • Current Situation
  • In Paper Machine No.3 one vacuum pump
    (KVM-600) has been installed for S. Couch and
    drawing 90 kWh.
  • Suggestion Benefits
  • As per the manufacturer performance table,
    motor should draw only 53 kWh against present 90
    kWh. Therefore it is suggested to contact the
    supplier for the root cause analysis of higher
    Energy Consumption. Saving potential is 90 69
    37 kWh resulting in saving of Rs.7.10 lacs /annum
    by maintenance of existing pump.

(No Transcript)
Write a Comment
User Comments (0)
About PowerShow.com