Energy Saving fan .ppt

LECTURE – 10.09.2014

By

P. Kanthasamy

Principal Technical Officer

Environmental Technology Division

CSIR- Central Leather Research Institute

Adyar, Chennai- 600 020

Email:[email protected] Mobile:9445587722

ENERGY AUDIT OF FANS

TERMS USED IN FAN

TERMScfm

Cfm-Cubic Feet Per Minute. A measure of airflow.

PsPs- Static Pressure. Resistance to airflow measured in inches of water gauge.

sone

Sone-A measure of loudness. One sone can be approximated as the loudness of a quiet refrigerator at a distance of 5 feet. Sones follow a linear scale, that is, 10 sones are twice as loud as 5 sones.

Bhp

BHP-Brake Horsepower. A measure of power consumption. Used to determine the proper motor horsepower and wiring.

hpHorsepower. Used to indicate a fan’s motor size.

rpm

RPM- Revolutions Per Minute. Measure of fan speed.

TSTS- Tip Speed. The speed of the tip of a fan wheel or prop measured in feet per minute.

AMCA

AMCA- Air Movement & Control Association. A nationally recognized association which establishes standards for fan testing and performance ratings. AMCA also license air volume and sound certified ratings.

BACKGROUND

Thermal power plant has several fans such as Induced draft (ID) fans, Forced draft (FD) Fans, Primary air fans (PA fans). These fans contribute to significant auxiliary power consumption. ID fans alone contribute to about 12% of total auxiliary power consumption

ID Fan System

Data collection

Observations and Analysis

Exploration for energy conservation measures

Report preparation

Steps Involved

DATA COLLECTION Collect detailed design specification & operating parameters

Fans Parameters ( FD, ID and PA Fan )

DATA COLLECTION Collect detailed design specification & operating parameters

Fans Parameters ( FD, ID and PA Fan )- contd…

DATA COLLECTION Details of the fans and ducting system: Collect the schematic diagram / network of the ducting system Collect Performance characteristics of all fans

Compile design, Performance Guarantee Test, previous best and last energy audit values with respect to fans and draft system which include excess air

If the fans are operated in parallel then it is advised to collect the performance curve for the parallel operation

Air quality and pressure equipments at the users as per the design requirements

INSTRUMENTS REQUIREDPower Analyzer: Used for measuring electrical parameters such as kW, kVA, pf, V, A and Hz

Temperature Indicator & Probe

Stroboscope: To measure the speed of the driven equipment and motor

Sling hygrometer or digital hygrometer

Anemometer

On line instruments – (calibrated)

Digital Manometer of suitable range and appropriate probes for measurement of pressure head and velocity head.

Pitot tubes

Additional pressure gauges with appropriate range of measurement and calibrated before audit.

MEASUREMENTS & OBSERVATIONS TO BE MADE

Energy consumption pattern of fans

Motor electrical parameters (kW, kVA, Pf, A, V, Hz, Total Harmonic Distortion(THD) of fans

Fan operating parameters to be measured/monitored for each Fans are:

1. Discharge / flow rates

2. Pressure (suction & discharge)

-Static pressure

-Dynamic pressure

-Total pressure


3. Damper position / guide vane position/ VSD Setting

4. Temperature of fluid handled

5. Load variation

6. Power parameters of fans

7. Fan operating hours and operating schedule

8. Pressure drop in the system (between discharge and user point)

9. Pressure drop and temperatures drop across the equipment

10. Fan /Motor speed


Oxygen content, flow, temperature and pressure measurement across in exhaust gas path

- Before and after air pre heater

- Before and after economizer

-Before and after ID fan

- Before and after ESP

- In case where flow measurement (for air pre heater and ESP) is not possible, it can be estimated based on mass balance principles, stoichiometric analysis,

ENERGY CONSUMPTION PATTERN

If the plant is monitoring the energy consumption, it is suggested to record the data and monitor the daily and monthly consumption pattern. (Collect data for 12 months)

Work out the total consumption of fans to arrive at percentage to the total consumption of the auxiliary consumption

If the energy meters are not installed to fans, instantaneous measurements can be carried out, based on the loading pattern the daily consumption can be worked out as per following table-

Energy consumption pattern

The parameters to be studied in detailed are:

Air /gas rates of fans / main ducts

Static pressure and dynamic pressure and total pressure

Power consumption of fan (for estimating the operating efficiency of the fans)

Monitor present flow control system and frequency of control valve operation if any (for application of variable speed drives)

Fill up the following data sheet for every fan

FAN OPERATING EFFICIENCY EVALUATION

Performance parameters for fans



FAN LAWS

Flow ? Speed Pressure ? (Speed)2 Power ? (Speed)3

1 1

2 2

Q N

Q N=

21 1

2 2

SP N

SP N =

3

1 1

2 2

kW N

kW N =

Varying the RPM by 10% decreases or increases air delivery by 10%.

Varying the RPM by 10% decreases or increases the static pressure by 19%.

Varying the RPM by 10% decreases or increases the

power requirement by 27%.

Where Q – flow, SP – Static Pressure, kW – Power and N – speed (RPM)

x x x

FANS PERFORMANCE ASSESSMENT

Static pressure• Potential energy put into the system by the fan

Velocity pressure• Pressure arising from air flowing through the duct. This is

used to calculate velocity

Total pressure • Static pressure + velocity pressure

• Total pressure remains constant unlike static and velocity pressure

TRAVERSE POINTS FOR VELOCITY MEASUREMENT

Fan total kW = Q in m3/ s x total pr. developed by fan in mmwc 102

Fan static kW = Q in m3/ s x static pr. developed by fan in mmwc 102

Fan static efficiency % Fan static kW x 100 Input kW to motor x ηm

=

Fan mechanical Efficiency = Fan total kW x 100 Input kW to motor x ηm

Parameter Details Unit

Q Air flow rate m3/ s

Static pressure Difference between discharge & suction pressure mmwc

Fan static/ total kW Static / total power consumption of the fan kW

Input kW to motor Measured power consumption of the motor kW

ηmEfficiency of the motor at operating load

Total pressure Difference between discharge & suction pressure mmwc



Corrected air density, γ = 273 X 1.293

273 + Air temperature in 0 C

Parameter Details Unit

Cp Pitot tube constant 0.85 or as given by manufacturer

γ Density of air or gas at test condition Kg / m3

Velocity in m / s =Cp x √2 x 9.81 x Diff. velocity pr. in mmwc x γ

γ

Volumetric flow (Q), m3/s = Velocity, m/s x Area, m2


In case of gas flow measurement of ID fans, where it is not possible to measure the gas flow, then the mass flow method can be adopted, provided the oxygen content and actual coal flow measurements are available. For flow estimation through this method, the following are required:

Stoichiometric air requirement (work out based on the coal composition)

Oxygen content at ID fan inlet (measured)

Excess air (estimate)

% Excess air = (%O2 in flue gas x 100) / (21 – O2 in flue gas)

Coal flow (based on actual measurement or on average basis)

Fly ash content (assumed based on past data)

While in case air flow measurement for FD and PA fans the following instruments (which ever are suitable) can be used

Thermal anemometer

Vane type anemometer

Pitot tube along with micro manometer can be used

Online measuring instrument

If the fans are operating in parallel, it is advised to measure all above parameter for every fan separately to evaluate the individual performance. However combined parameters of flow and head need to be verified with Performance curve for parallel operation

FAN PERFORMANCE ANALYSIS

FAN PERFORMANCE ANALYSISCompare the actual values with the design / performance test values if any deviation is found, list the factors with the details and suggestions to over come.

The investigations for abnormality are to be carried out for problems.

Enlist scope of improvement with extensive physical checks / observations.

Based on the actual operating parameters, enlist recommendations for action to be taken for improvement, if applicable such as- Replacement of fans, Impeller replacement, VFD application.

Cost analysis with savings potential for taking improvement measures.

Recirculation

Damper

IGV

VFD

Ideal

Power

Flow25 7550 100

100

75

50

25

FAN PERFORMANCE ANALYSISFlow controlFlow control


System characteristics and Fan curves

Impact of speed reduction


Visual survey of insulation & the ducting system:

Insulation status (measure the surface temperature with the aid of surface thermocouple / infrared pyrometer or by using thermal imaging cameras)

Bends and ducting status

Physical condition of insulation Identification of locations where action is required to improve the insulation (provide with detailed techno-economics)

Improvement options for ducting systems if any

Sources of air ingress

FAN PERFORMANCE ANALYSISStudy of air ingress in to the system:

Before and after air preheater Before and after ESP Before and after ID fanThe difference in the oxygen gives the extent of air ingress in to the system. Measurements of oxygen content across all units in flue gas path, indicates the locations where ingress is occurring

EXPLORATION OF ENERGY CONSERVATION POSSIBILITIESImprovement of systems and drives:

Use of energy efficient fans

Change of impeller with energy efficient impeller

Correcting inaccuracies of the fan sizing

Use of high efficiency motors

Fan speed reduction by pulley diameter modifications for optimisation

Option of two speed motors or variable speed drives for variable duty conditions

High Performance Lubricants: The low temperature fluidity and high temperature stability of high performance lubricants can increase energy efficiency by reducing frictional losses

Use of energy efficient transmission systems (Use of latest energy efficient transmission belts)

EXPLORATION OF ENERGY CONSERVATION POSSIBILITIES

Improvement in operations:

Minimising excess air level in combustion systems to reduce FD fan and ID fan load.

Minimising air in-leaks in hot flue gas path to reduce ID fan load and cold air in-leaks

Minimising system resistance and pressure drops by

improvements in duct system / Insulation aspects

Deviations in air flow rates

Measures to up keep the performance

After the identification of energy conservation measures, detailed techno-economic evaluation has to be carried out

PROBLEM

• A particular coal has the following ultimate analysis on a dry basis percent by mass:

Component Percent by Mass

• Sulfur 0.6

• Hydrogen 5.7

• Carbon 79.2

• Oxygen 10.0

• Nitrogen 1.5

• Ash 3.0

This coal is to be burned with 30% Excess Air. Calculate the Air-fuel ratio on a mass basis.

SOLUTION

• One approach to this problem is to write the combustion equations for each of the combustible elements per 100 kg of fuel. The molar compostion per 100 kg of fuel is found first

• Kmol S/ 100kg fuel = 0.6/32 = 0.02• Kmol H2/ 100kg fuel = 5.7/2 = 2.85• Kmol C/ 100kg fuel = 79.2/12 = 6.60• Kmol O2/ 100kg fuel = 10.0/32 = 0.3• Kmol N2/ 100kg fuel = 1.5/28 = 0.05

The combustion equations for the combustible elements are now written which enables us to find the theoretical oxygen required.

S+ O2 SO2

0.02S + 0.02 O2 0.02 SO2

H2 + 1/2O2 H2O2.85H+2.85/2 O2 2.85 H2OC+O2 CO2

6.60C+ 6.60O2 6.60CO2

Total Oxygen required For S = 0.02 H2 = 1.42 C = 6.60

Total Oxygen Required =0.02+1.42+6.60=8.048.04 kmol O2 required /100kg of fuel 0.31 kmol O2 is available in fuel /100 kg8.04-.31= 7.73 kmol

SOLUTION • Air-Fuel Theo = [7.73 +7.73 (3.76)] x 28.97/100

= [36.7948x 28.97]/ 100

= 10.659 kg air/kg fuel

For 30% excess air the air fuel ratio is

AF = 1.3 x 10.659= 13.856 kg air/kg of fuel

Engineering

Energy Saving fan .ppt