05

*For simplicity the assumption is made that this natural gas is pure methane. This assumption is often valid for high-Btu fuel gas. For more precision and with other fuel gases, the exact composition should be determined and used in the combustion equation.

-94,7000,000 Btu/hr

Surface heat loss

415,880,000 Btu/hr

Combustion air-100° F 5,250,000 cfh

6,300,000 Btu/hr

Product-100° F 50 tons/hr

500,000 Btu/hr

Stack gas-2200°F 5,700,000 cfh

265,800,000 Btu/hr

34,900,000 Btu/hr

36,000 gph 12,000,000 Btu/hr

Cooling H20-191°F

36,000 gph 39,300,000 Btu/hr

-94,400,000 Btu/hr Surface heat loss

611,521,000 Btu/hr

Combustion air—100°F 9,500,000 cfh

11,900,000 Btu/hr

Product-100° F 50 tons/hr

500,000 Btu/hr

466,300,000 Btu/hr

34,900,000 Btu/hr

36,000 gph 12,000,000 Btu/hr

Cooling H20-191°F

36,000 gph 39,300,000 Btu/hr

Figure 8.9 Heat-balance diagram for reheat furnace(a) Natural gas.(b) No.2 fuel oil.

A volume of air 22.65 + 85.4 ft3air

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