Chemical engineering paper([Removed by Freelancer.com Administrators]IF YOU CAN DO THE ASSIGNMENT
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1. Brief
A 5m (L) 2m (W) [url removed, login to view] (H) industrial furnace is to be designed to melt 7.5 t/hr of copper. The furnace operates on a continuous basis under essentially steady-state conditions and the natural gas-fired (CV = 52 MJ/kg) burners which will be installed can operate with a turndown ratio of 5:1. Heat transfer by convection to the melt surface is relatively low with h-value of 18 W/m2/K. In order to reduce wall losses, the furnace is lined with ceramic fibre with thermal conductivity of 0.22 W/m/K. The h-value for the outer casing, due to natural convection, may be assumed to be 10 W/m2/K whilst its surface emissivity is 0.8. In order to comply with the health and safety standard the outer casing temperature should be no more than 80C.
The net rate of radiative heat transfer to the molten copper is given by:
+ s As (Tw4 – Ts4) (1 – g)
Where
s = emissivity of the copper
g = emissivity of the flame
As = surface area of the molten copper
Tg = temperature of the flame
Ts = temperature of the molten copper
Assume methane combustion and take:
Tw = refractory wall temperature = (Tg + Ts)/2
Tex = Tg – 150K
= Stefan-Boltzmann constant
= 5.67 x 108 W/m2K
The net rate of heat transfer to the refractories can be estimated by consideration of conduction through this lining. Other information not given should be appropriately researched and justified.
Assume the following properties for the copper
Emissivity = 0.60
Specific heat capacity solid = 385 J/kgK
Liquid = 494 J/kgK
Latent energy of fusion = 205 kJ/kg
Melting temperature = 1084C
The emissivity of the flame and combustion products can be calculated from appropriate charts or better using the WSGG model.
Following your initial design which will specify the amount of fuel which is required and the furnace efficiency you should investigate
(i) the effect of changes in the recuparator effectiveness
(ii) the effect of changes in the % excess air supplied
(iii) the part-load performance of the furnace.
项目ID: #6957286