IKA C 6000 global standards, Руководство по эксплуатации

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23
Fuse
sample
Burning
aid
Igniter
Formation
of
sulphuric acid
Formation
of
nitric acid
Heat quantity from:
External energy
Corrections
As determined by the
system, during a combustion
experiment, not only is
heat generated from the
combustion of the sample,
but heat also occurs in the
form of external energy.
This may fluctuate considerably
in proportion to the heat
energy of the fuel sample.
The combustion heat of the cotton threat that ig-
nites the sample and the electrical ignition energy
would result in distorted values of the measure-
ment. This effect is taken into consideration in the
calculation with a correction value.
Substances with low flammability or substances
that burn poorly undergo combustion in combina-
tion with
combustion aids . The combustion aid is
first weighed and then added to the crucible with
the sample. From the weight of the combustion
aid and its known specific gross calorific value, it
is then possible to determine the quantity of heat
that is introduced thereby. The result of the experi-
ment must be corrected by this amount of heat.
The C 14 disposable crucible is a combustible
crucible that can be used instead of a traditional
crucible. The disposable crucible undergoes total
combustion with no residue. If a disposable cru-
cible is used, there is then no need for a cotton
thread. The crucible is in direct contact and is ig-
nited by the fixed ignition wire of the decomposi-
tion vessel.
The sample is weighed directly into the disposable
crucible. In most cases, no additional combustion
aid is necessary because the disposable crucible
itself acts as the combustion aid.
Acid correction
Almost all substances to be analyzed contain sul-
fur and nitrogen. Under the conditions that pre-
vail during calorimetric measurements, sulfur and
nitrogen undergo combustion and form SO
2
, SO
3
and NO
X
. Sulfuric and nitric acid arise in combi-
nation with the water resulting from combustion
and humidity. Heat of solution is also generated.
To obtain the standard gross calorific value, the
effect of the heat of solution on the gross calorific
value is corrected.
To obtain a defined final status and to record all
acids quantitatively, distilled water or another
suitable absorption solution is placed in the de-
composition vessel before the trial
according to
the relevant standards . With this absorption fluid
and the combustion water, the combustion gases
form acids.
After the combustion, the decomposition vessel
is thoroughly washed with distilled water so as
to collect the condensate that has settled on the
inner wall of the vessel as well. The solution ob-
tained in this manner can now be examined with
a suitable peripheral detection device for aqueous
decomposition into the respective acid content.
For more information on this subject, please con-
tact
IKA
®
‚ or your nearest authorized dealer.