Vertical Raw Mill Heat Balance Excel Sheet

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Vertical Raw Mill Heat Balance Excel Sheet

 

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PROCESS FILES
VRM HEAT AND MASS BALANCE
FLOW MEASUREMENTS BEFORE MILL IDF BEFORE MILL AFTER MILL
Temperature, oC 83 200 86
Static pressure, mm H2O -1026 -95 -866
Barometric pressure, mm H2O 10186 10186 10186
Dynamic pressure, Pd, mm H2O 26.00 52.00 50.00
Gas density at std. cond., kg/Nm3 1.37 1.39 1.38
Gas density at actual cond., kg/Am3 0.945 0.795 0.960
Average ( Pd ) 1/2 5.10 7.21 7.07
Flow area, m2 6.80 7.40 6.80
Pitot coefficient 0.734 0.734 0.734
Gas velocity, m/s 23.22 35.81 23.45
Vol. flow rate, Am3/h 568543 953983 574038
Vol. flow rate, Nm3/h 392074 545472 399412
HEAT AND MASS BALANCE of VRM (mill to cyclone)
Date:
Raw feed condition:  Rate 265 mt/h
Temperature 35 °C
Moisture 5.0%
Raw meal collected at cyclone:  Rate                          176.56 mt/h
Temperature (after cyclone) 83 °C
Moisture of mill product 0.8%
Weight of H2O vapor from raw matls.                          11,220 kg/h
Dust going to bag house at cyclone efficiency of 70% 77218.90 kg/h                    196.9 g/nm3
Hot gas condition before mill
Temperature 200 °C
Pressure -95 mmH2O
Oxygen content 9.6%
Volume at actual condition 953,983 Am3/h
Volume at standard condition 545,472 Nm3/h
Gas condition after the mill
Temperature 86 °C
Pressure -866 mmH2O
Oxygen content 11.5%
Volume at actual condition 574,038 Am3/h
Volume at standard condition 399,412 Nm3/h
Volume of H2O vapor from  raw mat’l                            9,048 Nm3/h
Gas condition at the mill fan inlet
Temperature 83 °C
Pressure -1026 mmH2O
Oxygen content 12.3%
Volume at actual condition 568,543 Am3/h
Volume at standard condition 392,074 Nm3/h
HEAT AND MASS BALANCE  of VRM
Reference temp. 20 deg C
Temp Cp
Input Nm3/h Mass, kg/h Heat, kcal/h °C kcal/kg
Raw material ( dry)             251,750.00               1,691,760.00 35 0.192
Raw material moisture               13,250.00                  463,750.00 35 1.000
Dust suspended at gas from CT                 5,646.33                  216,819.23 200 0.192
Hot gas  from CT 545,472.11             758,206.23            36,546,631.22 200 0.241
False air at mill 120,047.50             154,861.27               1,306,716.99 35 0.241
False air after mill to fan inlet 62,029.22               80,017.70                  675,188.09 35 0.241
Grinding heat               2,067,526.03
727,548.83         1,263,731.53            42,968,391.56
Output
New raw meal + kiln dust collected at cyclone, dry             180,177.43               2,990,945.40 83 0.200
New raw meal + kiln dust going to baghouse,dry               77,218.90               1,281,833.74 83 0.200
Raw meal moisture                 1,453.04                  120,602.64 83 1.000
Exit gases:  gas from preheater         545,472.11             758,206.23            14,985,755.22 83 0.238
false air from raw mill         182,076.72             234,878.97               4,707,502.52 83 0.241
H2O vapor from raw mat’l              9,513.67               11,796.96               7,491,631.08 83 0.288
Heat loss by radiation & convection               1,024,813.39
        737,062.50         1,263,731.53            32,603,083.99
-24.12%
Grinding heat computation Radiation & convection losses
mill motor 2496.83 kw Water evaporated            11,796.96 kg/h
classifier motor 86.96 kw R/C factor                    11.95 kcal/kg H2O
mill fan* 0 kw Heat loss at the mill         140,977.01 kcal/h
total 2583.79 kw Heat loss at the cyclone 883,836.38
assumed % efficiency 0.93 Total heat loss      1,024,813.39 kcal/h
Heat Balance at Cyclone
Temp Cp
Input Nm3/h Mass, kg/h Heat, kcal/h °C kcal/kg
Gases: hot gas from preheater 545,472.11 758,206.23            15,527,409.02 86 0.238
water vapor from raw matl 9,513.67 11,796.96               7,507,533.29 86 0.288
false from at mill 120,047.50 154,861.27               3,215,952.37 86 0.241
false air at cyclone 62,029.22 80,017.70               1,659,033.59 86 0.241
R.meal raw meal, dry 251,750.00               4,330,100.00 86 0.200
dust suspended at gas from CT 5,646.33                    97,116.95 86 0.200
raw meal  moisture 1,453.04                  124,961.77 86 1.000
1,263,731.53            32,462,106.98
Output
Gases: hot gas from preheater 758,206.23            14,985,755.22 83 0.238
water vapor from raw matl 11,796.96               7,491,631.08 83 0.288
false air fr. mill to dust col. 234,878.97               4,707,502.52 83 0.241
R.meal new raw meal + dust collected at  cyclone, dry 180,177.43               2,990,945.40 83 0.200
new raw meal + kiln dust going to baghouse,dry 77,218.90               1,281,833.74 83 0.200
raw meal moisture after cyclone 1,453.04                  120,602.64 83 1.000
1,263,731.53            31,578,270.60
Radiation & convection loss (by bal.)                  883,836.38
Stoichiometric calculation fot verifying measured data:
Volume of hot gas before the mill                        545,472 Nm3/h
Volume of H2O vaporized from raw materials                            9,048 Nm3/h
Volume of false air entering the mill (by O2 bal)                        120,047 Nm3/h 16.3%
Volume of gas leaving the mill                        674,568 Nm3/h
Volume of false air after mill to mill fan inlet (by O2 bal.)                          62,029 Nm3/h 8.4%
Volume of gas at the mill fan inlet (calculated)                        736,597 Nm3/h
Volume of gas at mill fan inlet (measured)                        392,074 Nm3/h
Difference of computed and measured volume -87.9% ok
Note: Minimal difference validates computed and measured  values
Estimate of kiln dust:
O2 at Ph exit 6.00%
O2 at rm3 inlet kg/h 9.60%
Water vapor at cond. Tower 9963.6 8035.16 nm3/h
False air 24.96% 134127.37 nm3/h
Preheater gas volume 403309.58 nm3/h
Kiln dust at assumed 30.00% collection at CT 5646.33 kg/h suspended in gas
20 g/nm3 1882.11 kg/h collected
Specific volumes used
Air 1.24 kg/nm3
Combustion gas 1.29 kg/nm3
Water vapor 1.39 kg/nm3

 

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