Environmental Engineering Reference
In-Depth Information
70.0
60.0
50.0
40.0
30.0
20.0
10.0
Metals continuous heating furnace
Metals continuous heat treatment furnace
0.0
0
1
10
100
1000
Heating capacity in log. scale (ton/h)
FIGURE A.9
Heating capacity and heat efficiency of metals continuous heating furnaces.
batch heating furnaces, metals heat treatment furnaces (continuous, batch), and
aluminum-melting furnaces (batch) do not have recuperators.
As shown in
Figure A.9
,
in the case of the middle and large continuous metals
heating furnaces over a capacity of 10 ton/h, there exist some heating furnaces with
heat efficiencies over 60% owing to the heat recovery systems. However, in the case
of small-scale heating furnaces under 10 ton/h, several furnaces over 40 to 50% of
heat efficiency exist, even if the average value is comparatively low. And, further, for
batch heating furnaces, there are furnaces with heat efficiency over 40%, such as batch
metal heating furnaces, batch metal heat treatment furnaces, and aluminum-melting
furnaces.
The existing furnaces with recuperators have efficiencies of 40 to 60% in some
quantities in every type of furnace. By introducing the result of the high performance
industrial furnace development, the efficiency of heat recovery can be much
improved compared with existing recuperators. Consequently, improvement of heat
efficiency by about 50% in energy-saving ratio, that is, from the above-mentioned
heat efficiency of 35% to around 53% on average, would be possible. The target
value of the energy saving ratio by the development of high performance industrial
furnace is over 30%. However, the energy-saving ratio rises to 34% with improve-
ment of heat efficiency from 35 to 53%, as shown in
Table A.11
.
2. Cement kiln
In the above-mentioned 11 types of industrial furnaces, the NSP (new suspension
preheater), which shows very high heat efficiency of 98%, was introduced in the
1970s and installed in 1994 including the SP (kiln with suspension preheater).
Because greater improvement in heat efficiency is not expected, the cement-sintering
furnace is excluded in the group of ceramics baking furnaces. The number of cement-
sintering furnaces in 1994 was 81 furnaces and their energy consumption was 9.47
×
10
9
l (converted crude oil).
3. Petroleum heating furnace
The combustion amount and the heat efficiency of the petroleum heating furnaces
are shown in
Figure A.10
;
the heat efficiencies of large-scale petroleum heating
furnaces with the air preheaters (APHs) show a high value of 90%. The heat
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