Page 38 - Glass Machinery Plants & Accessories no. 3-2019

ENERGY-SAVING
Energy-saving
sector and on optimizing and sta- mal nature, such as bottom tem- energy performance, and this can
bilizing conduction, with benefits perature, crown temperature or be based on the evaluation of
also on the quality of the glass throat glass temperature. furnace heat balance, in its input
produced. Most running furnaces are set and output voices.
For example, the correlation to collect the values of all param- This classification enables
between furnace consumption eters influencing production, thus to quantify the result of design
and other parameters such as providing the possibility of func- choices and operational settings
pull or cullet utilization is known, tional monitoring that compares in a more precise way. For exam-
but it is generally evaluated on the actual performance with the ple, the size of a furnace affects
a quality level and it makes the foreseen and budgeted one. This its thermal loss and, secondarily,
numerical comparison of furnac- comparison has to be extended its leakages and infiltrations.
es that operate in different situa- to the dimension of time, since It is obvious how thermal loss-
tions difficult. all thermal systems suffer from a es, both from plain structures
non-completely predictable aging and thermal bridges, increase
GLASS FURNACES, that affects the consumption sig- with the furnace surface, but
WORKING CONDITIONS nificantly. not in a proportional way, which
AND PERFORMANCE means that at the increase of the
It should be taken in account Specific consumption furnace size, the ratio between
that, generally speaking, glass Considering the most elemen- thermal loss and produced glass
furnaces do not work in constant tary measure of furnace energy decreases, thus decreasing spe-
and stable conditions; they are, in performance, specific consump- cific consumption. The more the
fact subject to pull changes, col- tion [MJ/ton], we can see how furnace size increases, the less
our, cullet and energy variations, this evolves depending on many evident the effect of thermal loss
not to mention the controlled parameters, not all under control. is, as shown in Figure 2, where
and uncontrolled variability con- For example, the specific con- the specific consumption of a
nected to the batch, in term of sumption of a 60-tpd furnace is same production is evaluated at
composition and humidity. not comparable to a 280-tpd fur- three different levels of specific
The furnace operator compen- nace. Other differing parameters pull for different furnace sizes.
sates these variations by acting such as cullet and boosting uti-
on control parameters such as lization or required quality level
fuel flow, boosting power and/ make different furnaces harder
or distribution, batch-charging to compare.
strategy, etc., aiming at ‘par- It is therefore necessary to use Figure 2 – The effect of the
tial goals’ typically of a ther- a modelling approach to furnace furnace surface on the MJ/ton (tpd)
for different specific pull

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