IKA C 1 Package 1/10 - Manual (Page 15)

15
Fuel
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 extraneous energy.
This may fl uctuate considerably in proportion to the heat energy
of the fuel sample.
The combustion heat of the cotton threat that ignites the sample
and the electrical ignition energy would result in distorted values
of the measurement. 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 combination 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 specifi c gross calorific value, it is then possible to
determine the quantity of heat that is introduced thereby. The
result of the experiment 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
crucible is used, there is then no need for a cotton thread. The
crucible is in direct contact and is ignited by the fixed ignition
wire of the inner vessel.
Inner vessel in which the combustible crucible is to be used, must
be fitted with an additional overlay (see accessories). 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 sulfur and nitrogen.
Under the conditions that pre-vail during calorimetric measure-
ments, sulfur and nitrogen undergo combustion and form SO2,
SO3 and NOX. Sulfuric and nitric acid arise in combination with
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 quantitati-
vely, approx 5ml distilled water or another suitable absorption
solution is placed in the inner vessel. 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
obtained 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 contact IKA ® ‚ or your
nearest authorized dealer.
When calculating the energy value in C1 external energies are
taken into account from kiln furniture, however, there is no
correction of acid. The calorific value is not calculated.
To do this, use the calorimeter software IKA ® CalWin.
The calorimeter system IKA ® C 1 is a precision measuring instru-
ment for the routine determination of calorific values of solid and
liquid substances. Exact measurements can however be achieved
only if the individual steps of the trial are performed with care.
The procedure as described in the „For your safety“ section 1 and
in the following sections must therefore be adhered to exactly.
If you are burning unknown samp-
les, leave the room or keep well
away from the calorimeter !
A few points should be noted in respect of the substances to be
combusted:
• Normally, solid substances can be burned directly in powder
form. Rapidly burning substances (for example benzoic acid)
must not undergo combustion in loose form.
Benzoic acid must only be burned in the form of pellets! Com-
bustible dust and powder must be compressed into pellets
before combustion. Oven-dry dust and powder such as wood
chips, hay, straw etc. burn in an explosive manner! They must
be moistened first! Readily combustible liquids with a low va-
por pressure must not be come in direct contact with the
cotton thread (e.g. tetramethyl dihydrogen disiloxan).
Notes on the sample
DANGER
Rapidly burning substances tend to squirt. Such substances
must be pressed into tablets before combustion. Suitable
for this is e.g. the IKA ® pelleting press C 21.
• Most liquid substances can be weighed directly into the cru-
cible. Liquid substances exhibiting turbidity or containing water
that will settle out must be dried or homogenized before they
are weighed in. The water content of these samples must be
determined.
• Highly volatile substances are placed in combustion capsules
(gelatin capsules or acetobutyrate capsules, see „Accessories“)
and undergo combustion together with the capsules.
• For substances with low flammability or low calorific substances
use combustion aids (see „Accessories“). Before the capsules or
the combustion bag is fi lled with the substance to be deter-
mined, it must be weighed in order to determine the additional
extraneous energy introduced into the system from the weight
and the gross calorific value. This is taken into consideration
with QExtern2. The amount of combustion aid should be as little
as possible.
The external energy must be determined externally.
C1 092014