Showing posts with label Efficiency & performance. Show all posts
Showing posts with label Efficiency & performance. Show all posts

Best practices to reduce the Auxiliary power consumption (APC) in Sugar based Cogeneration plants.


Auxiliary power consumption is directly related with power plant profit. Lesser the APC more will be the power export & hence more profit. So it becomes duty of every power plant professions to strive to reduce APC wherever possible.
Below table gives the area wise APC in Bagasse/coal based power plants
Sl No.
Area
APC in %
1
Boiler fans
35-38%
2
Boiler feed water pumps
35-36%
3
Turbo generator & its auxiliaries
10-12%
4
Bagasse feeding system
2-2.5%
5
Coal feeding system
1%
6
Bagasse handling system
4-4.5%
7
Coal handling system
1.5- 2%
8
Ventilation, AC & Air Compressors
4-5%
9
Water treatment plant
2-3%

Note: Bagasse based Cogeneration plant have incorporated coal handling system as supporting system & also run the power plant in non-season days. So APC for bagasse handling/feeding & coal handling/feeding has been considered separately.
Now a day there is huge scope for reduction of plant APC. Here scope of APC reduction at various areas of plant has been discussed.
A-Boiler:
1-Improve the combustion efficiency:
Combustion efficiency improvement will directly relate to the air consumption. Improved combustion will reduce load on FD, SA & ID fans, hence power consumption will reduce. In cogeneration plants or ion any power plants Boiler fans consume around 35-38% of total auxiliary power consumption.
In order to reduce the air requirement & to improve the combustion efficiency need to concentrate on bellow areas
  • Select good quality of fuel, if using bagasse the moisture should be 49 to 50%, as the moisture increases excess air required will also increases. This loads the FD, SA & ID fans more than requirement.
  • Arrest all leakages in air & flue gas paths
  • Modify combustion air ducts to reduce resistance to air flow

Opportunities for energy conservation in power plant...
2-Boiler fans:
As discussed above Boiler fans consume 35-38% of total APC, so need to concentrate on Boiler fans efficient operation.
  • Operate boiler fans in VFD mode at optimum speed
  • Incorporate inlet guide vanes to the system
  • For high speed fans, ensure the silence fitted at suction size has sufficient opening & at lesser height
  • Ensure all inspection & man way doors are sealed properly
  • Ensure clearance between inlet cone & impeller suction neck is minimum
  • Monitor draught losses in flue gas duct, air ducting, APH, Economiser & ESP regularly
  •  Follow lubrication schedule, replace damaged bearings to reduce vibrations & bearing temperature. High vibration bearings consume more power
3-Boiler feed water pumps (BFP)
Boiler feed water consume around 35% of total APC of the plant. Hence it is utmost important to reduce the BFP power consumption. Attention must be given on following points to reduce BFP power consumption.
  • Select optimum capacity BFPs, Under load running pumps have low efficiency
  • Better to install HT drives for BFP
  • Incorporate VFD to BFPs
  • Operate BFP in Auto mode based on discharge header pressure & drum pressure
  • Do not operate the pump with discharge valve throttled
  • Ensure BFP ARC valve has no leakage
  • Ensure BFP has sufficient suction pressure
  • Maintain Deaerator level on higher set point side.
  • Replace worn out balance & counter balance discs
  • Schedule pumps servicing as per OEM guidelines. And replace impeller wear rings or impellers if clearance found more. More clearance between wear ring & impeller will lead to higher power consumption
  • Follow lubrication schedule, replace damaged bearings to reduce vibrations & bearing temperature.
  • Do not uses BFP discharge water for de-super heating of LP process steam, instead use CEP discharge water
  • Clean suction strainers regularly
4-ESP
  • Implement hopper heater automation by thermostat
  • Optimize the charge ratio of Transformer
B-Fuel feeding system:
Fuel feeding system consumes around 2-4% of total APC. Hence it need to give attention to reduce APC in this area. Following are the some listed action points to reduce APC.
  • Incorporate VFDs to all fuel feeding systems, as fuel feeding system never run on 100% load.
  • Select planetary type gear boxes to fuel feeding system, as planetary gear boxes found of higher efficiency
  • Follow regular preventive maintenance to reduce wear, tear & friction of rotating parts, which ultimately lead to more power consumption
  • Replace all loose V belts. Loose V belts lead to increased power consumption
C-Turbo generator & Auxiliary:
Turbine auxiliary consume around 10-12% of total APC of the plant. Following are the areas where we can monitor the APC
  • Maintain lube & control oil filters clean
  • Maintain optimum lube oil temperature
  • Maintain cooling tower fills & drift eliminators clean to get required cooling water temperature
  • Incorporate VFDs to all cooling water pumps
  • Set CT blade angle at 11-14 degree.
  • Replace CT fan aluminium blades by FRP
  • Ensure cooling tower surrounding area is free of trees & structures for free flow of air
  • Incorporate VFDs to Condensate extraction pumps (CEP)
  • Ensure hot well make up is going on from gravity water from feed tank or surge tank
  • Schedule regular cleaning of heat exchangers like steam condenser, oil cooler, ejectors & Generator air cooler & gland steam condensers
  • Replace TG building exhaust fans by turbo ventilators
D-Fuel handling (Coal & Bagasse handling):
  • Ensure motors selected for all Bagasse belt conveyors are of optimum rating
  • Incorporate planetary gear boxes to belt & chain conveyors
  • Replace all damaged idlers regularly. Damaged idlers lead to more friction in the system
  • Ensure Vertical gravity take up height is optimum (1 to 1.5% of conveyor length)
  • Ensure belt scrapers (cleaners) & skirt boards are not over rubbing the belt to avoid friction & wear/tear
  • Follow regular preventive maintenance & lubrication schedule for conveyor pulleys bearings & idlers
  • Remove saturated bagasse/coal from deck plates of conveyors regularly to avoid friction

E-Compressors/blowers & Ventilation/air conditioning system
For air compressors optimise discharge air pressure & set loading & unloading times as per requirement
  • Clean air filters regularly
  • Replace all globe valves by gate valves or ball valves
  • Ensure compressor discharge air line is of correct size to avoid pressure drop in the line
  • For pneumatic ash handling system operate ash handling plant in probe mode or else optimize cycle time & conveying time
  • Incorporate VFDs to ventilation system
  • Optimize the usage of Air conditioning system in offices, meeting halls etc
  • Avoid compressed air for cleaning applications
F-Water treatment plant

Thumb rules water treatment plant
  • Ensure enough capacity of tanks for DM water storage, so that the operation time of the plant can be reduced
  • Plan to get more quantity of return condensate from process
  • Optimize boiler & CT blow down to reduce pumping power
  • Incorporate drain condensate recovery system to reduce pumping power as well as to conserve thermal energy
  • Operate DM plant at its full capacity & carryout regeneration as per out put OBR given by OEM to reduce pumping power as well as water consumption
  • Use treated N-pit water as  service water
Other:
1-Motor
  • Provide proper ventilation to the motors. For every 10 °C increase in motor operating temperatures over recommended peak, the motor life is estimated to be halved.
  •  
  • Synchronous motors are more suitable to improve power factor.
  •  
  • Balance the three phase power supply, an unbalanced voltage can increase motor input power by 3–5%.
  •  
  • Ensure the motor proper rewinding, an improper rewinding could lead to efficiency reduction.
  • Ensure proper alignment between motor and load ends (fans, pump, gear box, blower etc.) to avoid more power consumption and failures.
2-Lighting
Incorporate timers for plant lighting systems like conveyors, street, bagasse & coal yards etc
Replace all CFL & incandescent bulbs by LED bulbs


Read POWER PLANT CALCULATIOS

Basics terms used in Thermodynamics & related calculations


                                Thermodynamics:

It is an axiomatic science which deals with the relations among heat, work and properties of equilibrium system.It is a science, which deals with interaction between energy and material system.

Terms used in Thermodynamic science:

System:It is a finite quantity of matter or a prescribed region of space.

Boundary:It is the actual or hypothetical envelope enclosing the system.


Closed system: If the boundary of the system is impervious to the flow of matter is called  closed system.


Open system: there is  flow of matter into and out of the system


Isolated system:An isolated system doesnot exchange energy  & matter with any of the other system


Homogeneous system: A system which contains single phase is called homogeneous system


Hetergeneous system : Here system consists of more than two phases


Pure substance: A substance which is homogeneous in compossition &  chemical aggregation


State: It is the condition of the system at an instant of time as described or measured by its properties


Cycle:Any process or series of processes whose end states are identical is termed as a cycle


Process: It occurs when the system undergoes a change in state or n energy transfer at a steady state.


Reversible process: A process is one which can be stopped at any stage and reversed so that the system & surroundings are exactly restored to their initial states.


Example:Exapnsion & compression of springs, Electrolysis


Irrreversible process: In thisprocess heat is transferred through a finite temperature.


Example:Combustion, free expansion, heat transfer


Temperature: It is state of a body  which distinguishes a hot body from a cold body.It is measured in Fahrenheit, Degree centi gare, Kelvin etc


Pressure: It is a force per unit area.Pressure is exerted by gases, vapours & liquids.It is measured in Kg/cm2,Bar, Pascal, N/m2, N/mm2, mm of water column.



Thermal Equilibrium: Temperature of the system does not change with time and has same value at all the points of the system.

Mechanical Equilibrium: It is the condition where there are no unbalanced forces within the system, pressure in the system is same at all the points.

Chemical Equilibrium: Composition of chemicals does not change with time and no chemical reaction takes place in the system.

Enthalpy:It is the total heat content of the steam. Expressed in h…kcal/kg.

Entropy: is a function of a quantity of heat, which shows the possibility of conversion that heat into work. That is, if Entropy is more then there is minimum availability for conversion of heat into work and for minimum entropy there is maximum availability for conversion of heat into work. It is measured in kcal/kg.

Boyle’s law:At constant temperature, pressure of a perfect gas is inversely proportional to its volume.

P = 1/V or PV = Constant

Charles law:At constant pressure, volume of a given mass of a gas is directly varies as its temperature.

V = T
(V1/T1) = (V2/T2) = …… Constant

Gay-Lussac law:The pressure of a given mass of a perfect gas varies directly as its temperature, when the volume remains constant.
P = T
(P1/T1) = (P2/T2) = Constant

Relation among pressure, temperature, enthalpy and specific volume of steam

  • At constant temperature enthalpy decreases with increase in pressure
  • At constant pressure enthalpy increases with increase in temperature.
  • Specific volume increases with decrease in pressure and increase in temperature
  • Enthalpy of evaporation decreases with increase in pressure and temperatures.
Specific heat: Amount of heat required to raise the temperature of unit mass of substance by 1 degree centigrade.It is measured in constant pressure Cp & Constant volume Cv.Mesured in kcal/kg

Specific volume: It is the volume occupied by the unit mass of the system.It is measured in m3/kg.



Intensive property:It is the property of steam, whose value for the entire system is not equal to the sum of their values for the individual parts of the system.

Example: Temperature, pressure and density.


Extensive property:It is the property of steam, whose value for the entire system is equal to the sum of their values for the individual parts of the system.



Example: Volume and mass.


Zeroth law of thermodynamics:The law states that, when two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other.

First law of thermodynamics: Law states that when a system undergoes a thermodynamic cycle then the net heat supplied to the system from surroundings is equal to net work done by the system on its surroundings.

Second law of thermodynamics:It states that, it is impossible to construct an engine working on a cyclic process, to transfer heat from a body at a lower temperature to a body at a higher temperature without the aid of an external energy.

Different types of heat given to water to convert it into steam


Sensible heat : Amount of heat given to water to bring water from its normal temperature to Boiling temperature or saturation temperature. It is denoted by hf & measured in kcal/kg.


Latent heat: Amount of heat iven to saturated water to convert into saturated steam.It is denoted by hf g& measured in kcal/kg.


Total heat : It is the quantity of heat required to convert 1 kg of water into wet steam at constant pressure.It is the sum of total heat of water and the latent heat.It is also called as enthalpy.Denoted as h for wet steam and hg for dry steam


h = hf + x hfg


x is the dryness fraction of steam.


Dryness fraction of steam (x) : It is the ratio of the mass of actual dry steam to the mass of the steam containing it.


x = Ms/(Ms + Mw)



Superheated steam: when steam is heated after it has become dry and saturated.It is called superheated steam.


hsup = hf + hfg + Cps (Tsup-Ts)


Whwre, Cps = Specific heat of super heated steam = 0.5 kcl/kg

Tsup = Temperature of superheated steam
Ts = Saturated temperature at saturated pressure
(Tsup-Ts) is called as Degree of superheat.

Basic calculations:

1-Convert the pressure 80 cm of Hg to Kpa

Pressure at 760 mm of Hg = Density X g X h

                                           = 13.596 X 1000 X 9.81 X 760/1000
                                           = 101325 Pa =101.325 Kpa

2-Convert 2mm of water column pressure to Pascal

Pressure due to 2 mm of water column =1000 X 9.81 X 2 =19620 Pa

3-On a piston of 15 cm diameter of a force of 2000 N is applied uniformely caluclate the pressure on piston

Pressure = Force applied/Area of the piston

P = 2000 / ((3.142 X 0.152/4).....Area of piston =Pi X D2/4

P = 113636.363 N/M2

3-Atube contains an oil of specific gravity 0.88 to a depth of 1500 mm, find the gauge pressure at this depth

SG of oil =0.88
Depth of the oilin tube =1500 mm
We know that,
P = Density X g X h

P = 0.88 X1000 X  9.81 X 1.5...As SG =Density of oil / Density of water, Density of water is 1000 kg/m3

P = 12,949.2 N=/m2

1 N/M2 =1 X 10-5 kg/cm2

P =0.13 kg/cm2

4-Determine the dryness fraction of steam which has 2 kg of water in suspension with 60 kg of steam

Mass of dry steam Ms = 60 kg

Mass ofwater in suspension = 2 kg

Dryness fraction of steam x = 60/(60+2) =0.967

5-Determine the amount of heat given to 3 kg of water at 25 deg c to convert it into steam at 7 kg/cm2G and 0.9 dry.

Mass of water =Mw = 3 kg

Temperature of water = tw = 25 deg c

Pressure of steam = 7 kg/cm2

Fom the steam table at 7 kg/cm2 pressure (take absolute pressure i.e at 8 kg/cm2),

hf =172.73 kcal/kg

hfg = 488.22 kcal/kg

We have the formula for enthalpy of 1 kg of steam at 0 deg c is

h = hf + xhfg =172.73 + 0.9 X 488.22 =612.12 kcal/kg

Sensible heat of 1 kg of water at 25 deg c is = Mw X Cpw X (tw-t0)

=3 X 1 X (25-0) =75 kcal/kg

Net quantity of heat supplied per kg of water =612.12-75 =537.12 kcal/kg

Therefore total amount of heat to be supplied =3 X 537.12 =1611.38 kcal

6-Determine the mass of 0.2 m3 of wet steam at a pressure of 5 kg/cm2G and dryness fraction of 0.85. Also calculate heat of 1 m3 of steam.

Steam pressure P = 5 kg/cm2

Dryness fraction x =0.85

Fro steam table at 5 kg/cm2G

hf = 160.64 kcal/kg

hfg =497.47 kcal/kg
 Vg = 0.312 m3/kg

Density = 1/(x X Vg) =1/(0.85 X 0.312) =3.77 kg/m3

Mass of 0.2 m3 of steam = 0.2 X 3.77 =0.754 kg

Total heat of 1m3 of steam which has 3.77 kg of mass
=3.77h
=3.77 X (hf + xhfg) = 3.77 X (160.64 + 0.85 X 497.47) = 2199.7 kcal

7-What amount of heat would be required to produce 100 MT of steam at pressure of 67 barA and temperature 490 deg c from 150 deg c? Consider Cp of super heated steam =0.5 kcal/kg

Mass of steam = 100 MT =100 X 1000 =100000 kg

Steam pressure P=67 kg/cm2 absolute

Temperature of steam tsup =490 deg C

Temperature of water t =150 deg C

Refer steam table at 67 kg/cm2A & 490 deg c 

hf =300 kcal/kg

hfg =362.91 kcal/kg

ts = 283.75 kcal/kg

hsup = hf + hfg + Cps X (tsup-ts) =300 + 362.91 + 0.5 X (490-283.75) =766.035 kcal

Amount of heat already associated with 1 kg of water = 1 X 1 X (150-25) =125 kcal..Specifc heat of water is 1 kcal/kg

So net heat required = 766.035-125 =641.035 kcal

Total amount of heat required =641.035 X 100000 =64,103,500‬ kcal







Calculation of power generation cost of Thermal power plants & Co-generation plants


Power generation cost: It is the amount of rupees spent on generation of 1 unit of power


Power export cost: It is the amount of rupees spent on export of 1 unit of power

Generally power generation actual cost is the sum of Fuel cost, man power cost, operation & maintenance costs administration cost, river water cost, plant gardening & vehicles cost  etc

Power generation & Export cost in Thermal power plants:

Part A:Fixed data
  • Total power generation in KWH = A1
  • Total power export KWH = A2
  • Total fuel consumed = A3
  • Rate of per ton of fuel in = A4
  • Raw water consumption per day in MT or M3 = A5
  • Rate of per ton or   of river water in  = A6
  • Rate of per unit power for lifting water from source to Reservoir Rs= A7

Part B:
Operation cost head wise
  • Cost of fuel in Rs B1= A3 X A4
  • Cost of raw water in Rs B2 = A5 X A6
  • Cost of chemicals consumed for water treatment = B3
  • Cost of fuel feeding in =B4
  • Cost of raw water lifting charges from river to reservoir= B5
Total operation cost C = B1 + B2 +B3 + B4 + B5


Part C:
Maintenance cost head wise
  • Cost of spares,consumables consumed  = C1
  • Cost of Lubricants = C2
  • Cost of store inventory= C3
  • Tools tackles testing cost = C4
  • Measuring instruments calibration cost = C5
Total maintenance cost C = C1 +C2 + C3 + C4 + C5

Part D :
Administration cost head wise
  • Cost of  O &M man power salary = D1

  • Cost of site expenditures =  D2

  • Cost of gardening labours salary =D3

  • Cost of Security guards salary = D4

  • Cost of transportation vehicles =D5
Total administration cost = D = D1 + D2 + D3 + D4 + D5
  • Total Cost of production, E = B + C + D
  •  
  • Power generation cost per unit =A1/E....Rupees/KWh or Dollars/Kwh

  • Power export cost per unit = A2/E.....Rupees/KWh or Dollars/Kwh

Note:

1-In calculation power generation cost, power consumed for plant auxiliary running should not be considered

2-In co-generation plants:
  • Cost of power given to process plants should be considered
  • Cost of process steam given should be considered for power generation cost calculation
Read

Understanding the specific terms for Power plants performance analysis





It is very must to understand the basic fundas of specific terms used in power plants.

The following terms very frequently used in power plant calculations

1-SFR:It is steam to fuel ratio, it is the amount of steam generated on burning or oxidation of 1 MT of fuel. 

SFR =Steam generated / Fuel consumed
Note:If steam generated is taken in MT, then take fuel conssumed also in MT  , so the SFR is unitless

SFR depends on 
  • Type of the fuel & its GCV
  • Type of the Boiler & its efficiency
If the fuel GCV & Boilr efficiency are high,then SFR value will be more and vice versa


2-SSC: Spcific steam consumption, it is the amount of steam required to generate 1 Kwh or 1Mwh of power.

SSC = Steam consumption / Power generated

Note: If steam consumption taken is in MT,then power generation should be in MW.And if steam consumption taken is in Kg,then power generation should be in Kw.

SSC depends on the type of steam Turbine & its operating parameters.

  • If the turbine has lesser number or no any extractions or bleeding steam, then the SSC value of that particular turbine will be less

  • If the steam pressure and temperature at the Turbine inlet are more than the SSC value is less


3-SFC:It is the amount of fuel consumed to generate one Kwh of power

SFC = Fuel consumed in MT or Kg / Power generated in Mwh or Kwh

SFC is also give as,

SFC = SSC / SFR

SFC is less for power plants which have,

  • Higher Boiler efficiency
  • Higher fuel GCV
  • Higher steam pressure & tempeatures
  • Condensing turbines 

4-PLF: Plant Load Factor, it is the ratio of average power generation to the plant capacity during that period. It is expressed in %.

PLF = (Average power generation X 100) / Plant capacity during particular period.

5-PCF: Plant Capacity Factor is the ratio of average power generation to the plant installed capacity. It is expressed in %.

PCF = (Average power generation X 100)/Plant installed capacity.

6-PAF:Plant Availability Factor ,it is the ratio of total time in hours utilized for power generation to the total available hours for power generation. It is expressed in %.

PAF = (Total hours utilized for power generation X100)/Total available hours

Basics of Thermodynamics

7-Demand Factor:It is the ratio of maximum demand to the total connected load. It is always less than unity. Lower the demand factor, the less system capacity required to serve the connected load.

8-Diversity Factor: It is  the ratio of total connected load to the maximum demand. It is always greater than unity.

Let us solve follwoing examples to be more clear on above specific terms.

Example-1:A Coal fired Boiler of capacity 75 TPH, generates 1680 MT of steam in a day at SFR 2.2, calculate the fuel consumed

SFR = Steam generation / Fuel consumed
Fuel consumed = 1680/2.2
Fuel consumed = 763.63 MT

Example-2:A cogneration based 25 MW steam Turbine has specific steam consumption (SSC) 5.5 MT, calculate the steam flow per hour

SSC = Steam consumed / Power generation
Steam consumed = 5.5 X 25 =137.5 MT/hour =137.5 TPH

Example-3: A Therml power plant generates 2000 MW power in a consumes 1230 MT coal and generates 8000 MT of steam, calculate SFR, SSC & SFC of the thermal power plant

SFR =Steam generated / Fuel consumed
SFR = 8000 / 1230 = 6.5

SSC = Steam consumed / Power generation
SSC = 8000 / 2000 =4.0 MT of steam / MW of power

SFC = Fuel consumed in MT or Kg / Power generated in Mwh or Kwh
SFC = 1230 / 2000 = 0.615 kg of coal / kwh of power generated
or 
SFC = SSC / SFR = 4.0 / 6.5 =0.615 kg of coal / kwh of power generated

Example-4:Power generation of 70 MW power plant is restricted to 45 MW due to fuel constraint, calculate the PLF and PCF if average generation of the plant in day is 42.5 MWH.

Plant load factor (PLF) = (Average power generation in a day) X 100/(Plant capacity on particular period)
                                      =(42.5 X 100/45) = 94.4%
Plant capacity factor (PCF) = (Average power generation in a day) X100/(Plant installed capacity)
                                             = (42.5 X 100/70) =60.7%

Example-5:A power station has a connected load of 50 MW, the maximum demand at the station is 25 MW. Find the demand factor.
Demand factor (DF) = Maximum demand/Connected load
                                  = 25/50 =0.5

Example-6: A power plant runs 365 days in a year, but due to major breakdown in Turbine, plant taken sshutdown for 2days, calculate the plant availability factor

PAF = (Total hours utilized for power generation X100)/Total available hours

PAF = (365-2) X 24 X 100 / (365 X 24)
PAF = 99.45%

PAF can also be calculated by considering the days

        Opportunities for energy conservation in power plant                         

15-Emergencies in power plant operation

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