Simplified
heat balance for reheating furnace
| DATA |
|
|
|
|
| discharge temp |
1,200 |
ºC |
2,192 |
ºF |
| soak zone temp |
1,240 |
ºC |
2,264 |
ºF |
| heat zone temp |
1,200 |
ºC |
2,192 |
ºF |
| charge temp |
20 |
ºC |
68 |
ºF |
| air combustion temp |
25 |
ºC |
77 |
ºF |
| fumes temp at charge end |
950 |
ºC |
1,742 |
ºF |
| fumes temp end of furnace |
737 |
ºC |
1,359 |
ºF |
| production rate |
52.7 |
metric t/h |
58.1 |
short ton/h |
gas consumption
|
44.0 |
Nm³/t |
1,341 |
MM Btu/ton |
| scale loss |
0.5 |
% |
0.5 |
% |
| fuel- net calorific value |
8,465 |
kcal/Nm³ |
900 |
Btu/SCF |
| CALCULATIONS |
|
|
|
|
|
|
|
| excess of air |
5 |
% |
|
|
5 |
% |
|
| combustion air flow |
10.7 |
Nm³/Nm³ of gas |
24,834 |
Nm³/h |
15,455 |
SCFM |
|
| fumes flow |
12.4 |
Nm³/kg gas |
28,650 |
Nm³/h |
17,829 |
SCFM |
|
| initial steel enthalpy |
2 |
kcal/kg |
105,400 |
kcal/h |
0.418 |
MM Btu/h |
|
| final steel enthalpy |
204.0 |
kcal/kg |
10,750,800 |
kcal/h |
42.663 |
MM Btu/h |
|
| energy to the steel |
202.0 |
kcal/kg |
10,645,400 |
kcal/h |
42.244 |
MM Btu/h |
53 % |
| fumes enthalpy after recuperator |
252.6 |
kcal/Nm³ |
7,235,609 |
kcal/h |
28.713 |
MM Btu/h |
36 % |
| losses total |
38.1 |
kcal/kg steel |
2,008,235 |
kcal/h |
7.969 |
MM Btu/h |
10 % |
| energy from gas burning |
372.5 |
kcal/kg steel |
19,628,642 |
kcal/h |
77.893 |
MM Btu/h |
98 % |
| energy from scale formation |
4.9 |
kcal/kg steel |
260,602 |
kcal/h |
1.034 |
MM Btu/h |
1 % |
| total energy |
377.4 |
kcal/kg steel |
19,889,244 |
kcal/h |
78.927 |
MM Btu/h |
100 % |
| REHEAT FURNACE |
DIMENSIONS in mm |
|
DIMENSIONS in feet |
| |
height |
length |
width |
|
height |
length |
width |
| hearth |
|
12,192 |
9,754 |
|
|
40.00 |
32.00 |
| soak zone |
1,600 |
5,182 |
9,754 |
|
5.25 |
17.00 |
32.00 |
| heat zone |
2,347 |
2,438 |
9,754 |
|
7.70 |
8.00 |
32.00 |
| convective zone |
1,707 |
5,182 |
9,754 |
|
5.60 |
17.00 |
32.00 |
| 2 discharge doors |
610 |
|
762 |
|
2.00 |
|
2.50 |
| billet |
102 |
9,144 |
102 |
|
0.33 |
30.00 |
|
| COOLING WATER |
30 |
m³/h |
132 |
GPM |
| 5 |
delta T (C) |
41 |
delta T (F) |
| LOSSES CALCULATIONS |
kcal/h |
kcal/kg steel |
% |
MMBtu/h |
MM Btu/ton |
% |
| hearth |
129,618 |
2.5 |
6 |
0.514 |
0.009 |
6 |
| soak zone |
264,946 |
5.0 |
13 |
1.051 |
0.018 |
13 |
| heat zone |
128,585 |
2.4 |
6 |
0.510 |
0.009 |
6 |
| convective zone |
139,867 |
2.7 |
6 |
0.555 |
0.010 |
6 |
| discharge doors - radiation |
373,305 |
7.1 |
18 |
1.481 |
0.026 |
18 |
| discharge doors - cold air |
122,355 |
2.3 |
6 |
0.486 |
0.008 |
6 |
| atomizing air |
0 |
0.0 |
0 |
0.000 |
0.000 |
0 |
| cooling water |
150,000 |
2.8 |
7 |
0.595 |
0.010 |
7 |
| other losses (should be 15%) |
699,557 |
13.3 |
34 |
2.776 |
0.048 |
34 |
| TOTAL LOSSES |
2,008,235 |
38.1 |
100 |
7.969 |
0.137 |
100 |
| steel enthalpy |
| temp C |
kcal/kg |
| 20 |
2 |
| 100 |
11.1 |
| 200 |
23.2 |
| 300 |
36.2 |
| 400 |
50.2 |
| 600 |
82.3 |
| 800 |
136 |
| 1000 |
171 |
| 1100 |
187.5 |
| 1200 |
204 |
| 1250 |
212 |
|
| steel enthalpy |
| temp F |
Btu/lb |
| 68 |
4 |
| 212 |
20 |
| 392 |
42 |
| 572 |
65 |
| 752 |
90 |
| 1112 |
148 |
| 1472 |
245 |
| 1832 |
308 |
| 2012 |
338 |
| 2192 |
367 |
| 2282 |
382 |
|
| hearth losses |
| temp C |
kcal/m².h |
| 800 |
800 |
| 1000 |
1000 |
| 1100 |
1100 |
| 1200 |
1200 |
| 1300 |
1300 |
| 1400 |
1400 |
|
| roof losses |
| temp |
kcal/m².h |
| 800 |
2050 |
| 1000 |
2800 |
| 1100 |
3225 |
| 1200 |
3650 |
| 1300 |
4125 |
| 1400 |
4600 |
|
| wall losses |
| temp |
kcal/m².h |
| 800 |
1500 |
| 1000 |
1950 |
| 1100 |
2225 |
| 1200 |
2500 |
| 1300 |
2800 |
| 1400 |
3100 |
|
| hearth losses |
| temp F |
Btu/sqft.h |
| 1472 |
295 |
| 1832 |
369 |
| 2012 |
406 |
| 2192 |
442 |
| 2372 |
479 |
| 2552 |
516 |
|
| roof losses |
| temp |
Btu/sqft.h |
| 1472 |
756 |
| 1832 |
1032 |
| 2012 |
1189 |
| 2192 |
1346 |
| 2372 |
1521 |
| 2552 |
1696 |
|
| wall losses |
| temp |
Btu/sqft.h |
| 1472 |
553 |
| 1832 |
719 |
| 2012 |
820 |
| 2192 |
922 |
| 2372 |
1032 |
| 2552 |
1143 |
|
|
