Perhitungan Bahan Bakar Boiler

Fuel balance for CALCULATION

Boiler Capacity : 45 MT/hr

Mill Throughput : 60 MT/hr

Data from year 2004 :

a)   Fibre  =  13.86%

     FFB

     Nut   x     Fibre         x    1                    `    

     FFB         Presscake        Nut   /  Presscake

    12.5   x     52.58        x    (1 / 47.72 )

b)  Shell   = 7.26% @ 10% moistture  [  Nut   x   Shell    =   12.5  x  58.11   ]

     FFB                                                 FFB      Nut                 100

c)   Ltds   =   85.45 %

    Total

Enthalpy for saturated water at temperature 30°C (h_f) = 126  kJ/kg  (Room Temp)

Enthalpy for saturated water at 100°C ( h_{f 100})  = 419.1 kJ/kg  ( Deaerator Temp)

Latent heat at 30°C = 2430 kJ /kg

Enthalpy steam at 320 psi , 217° C  =  2797.60

Calorific value of fibre  =  11346 kJ/kg  @ 50 % moisture.

Calorific value of shell  = 18840 kJ / kg @ 10% moisture.

Available fibre energy (E_fw) =  Fibre    x   Throughput   x    Calorific value

                                              FFB

                                         = 13.86     x   60 MT/hr     x   11346 kJ/kg   x  1000

                                              100

                                         =  94353336  kJ/hr

Available shell energy (E_sw) = Shell   x    Throughput   x   calorific value

                                             FFB

                                          = 7.26   x    85.45   x   60 MT/hr  x   1000  x   18840

                                              100         100    

                                          =  70126285.68 kJ/hr

W_fw =  13.86   x  60  x  1000

            100

       =  8316  kg/hr

W_ef  =  7.26  x  60  x  1000  x  85.45

           100                               100

       =  3722.2 kg/hr

Total energy available, E_tw =  E_fW  +  E_sw

                                        =  94353336  +  70126285.68

                                        =  164479621.7  kJ/hr

Moisture in fibre, W_t    =  50% of fibre

                                   =  0.5  x  8316 kg/hr

                                   =  4158  kg/hr

Energy required to dry the moisture in fibre  =  E_wf

                           E_wf   =  W_t  +  calorific value

                                   = 4158  kg/hr  x  (h_f  -  h_f30)

                                   =  4158  kg/hr x  (2430  - 126) kJ/kg

                                   =  9580032  kJ/hr

Moisture in shell, W_t   = 10%  of shell

                                  =  0.1 x  3722.2  kg/hr

                                  =  372.22  kg/hr

Energy required to dry the moisture in shell  =  E_sw

                         E_sw    =  372.22  x  (2430 -  126)

                                 =  857594.88  kJ/hr

Total energy required to remove moisture   =  E_wf   +  E_sw

                                                                 =  9580032  +  857594

                                                                 =  10437626  kJ/hr

Surplus Energy   =  

 [Total energy from fibre and shell - total energy required for operation]

                         =  164479621   -  109540207  kJ /hr

                         =  54939414  kJ/hr

Balance of fibre and shell :

Fibre  =  8316 kg/hr at 69%

Shell   =  3722.2 kg/hr at 31%

W_t   =  12038

Calorific value for fuel  =  [ %fibre x calorific value ]  +  [ % shell  x  calorific value ]

                                   =  [ 0.69 x 11346 ]  + [ 0.31 x  18840]       

                                   =  7828.74 kJ/kg  +  5840.4 kJ/kg

                                   =  13669.14  kJ/kg

Balance of fuel  =  surplus energy

                             calorific value of fuel

                        =   54939414

                             13669.14

                        =   4019 kJ/kg

Mill power required  = 1300 kW

Turbine consumption  =  25kg/kW

Efficiency of boiler  =  90%

Make up steam  =  5000kg/hr

Equivalent steam generation by boiler

                         = power required  x  steam consumption

                         = [ ( 1300 kg/hr x 25 kg/kW)  + 5000 kg/hr] x 100 / 90

                         = 41666.67 kg/hr

Energy needed to generate steam:

Deaerator                          Boiler

100°C                                217 °C

1 atm                                 321psi

h_f100 = 4198.1kJ/kg              h_f217 = 2797.6 kJ/kg

Energy needed to generate steam  =  (h_f217  - h_f100) x 41666 kg/hr

                                                   =  99102581 kJ/hr

Total energy required for operation

               =  energy required to generate steam  +  energy required to remove moisture

               = 99102581 kJ/hr  +  10437626  kJ/hr

               = 109540207 kJ/hr

Based on 16 hrs per day of operation;

Surplus fuel  =  16hrs/day  x  4019 kg/hr

                    =  64.304 MT/day

Minimum throughput required to run the boiler:

Total energy for operation  =  109540207 kJ/hr

Weight of fuel (60 MT/hr)  =  12038 kg/hr

                                         =  13669.14 kJ/kg

Minimum fuel needed for 45MT/hr boiler

                                        =  total energy required

                                             calorific value

                                        =  109540207 kJ/hr

                                                 13669    kJ/kg

                                        =   8013.76  kg/hr

Minimum throughput required;

For 60 MT/hr FFB produces 12038 kg/hr  of fuel

8013.76 fuel kJ/hr produced from X throughput;

X throughput  =  8013.76  x  60

                           12038

                      =  39.94  MT/hr

Minimum throughput to run boiler without running diesel engine  =  40 MT/hr

 

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