Switching Off The Device; The Standard Calorimetric Procedure; Calorific Value Determination - IKA C 3000 isoperibol Operating Instructions Manual

Switching off the device

The standard calorimetric procedure

Determining the calorific value
Test condition
Combustion is carried out in a calorimeter under specific condi-
tions. The IKA C 3000 isoperibol is filled with a weighed fuel
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sample, the fuel sample is ignited and the temperature increase in
the calorimeter system measured.
The specific calorific value of the sample is calculated as follows:
• Weight of fuel sample
• Heat capacity (C-value) of calorimeter system
• Calculated temperature increase of water in the calorimeter
system
For complete combustion the decomposition vessel is
filled with pure oxygen (quality 3.5). Adjust the pressure
of the oxygen atmosphere in the decomposition vessel at
3 MPa (possible max. 4 MPa). The exact determination of
the gross calorific value of a substance requires that the
combustion proceed under precisely defined conditions.
The applicable standards are based on the following as-
sumptions:
• Depending on the start temperatur that is set, the tempera-
ture of the fuel before the combustion is 20 °C upto 30 °C.
• The water contained in the fuel before the combustion and
the water that is formed when compounds comprising the
fuel containing hydrogen undergo combustion is present in
a liquid state .
• No oxidation of the atmospheric nitrogen has taken place.
• The gaseous products after combustion consist of oxygen,
nitrogen, carbon dioxide, sulfur dioxide and the oxidation
products of the sample.
• Solid substances may be formed (for example ash).
The following are the default modes that are set:
- Isoperibol 22 (IKA C 3000 isoperibol)
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If the system is changed to a different function it must be recali-
brated.
First commissioning
At first commissioning you must register a decomposition vessel:
• To do this, press "Menu on" button.
• Select the "Function..." menu item.
• Select the "New vessel" tab and follow the instructions.
"End": This saves the measurements taken during the day; the
cover of the calorimeter is closed and the software shut down.
After this, switch off the calorimeter and all the accessories.
Never switch the device off without previously having run
"End", otherwise data may be lost!
Often, however, the combustion products that form the basis of
the standards are not the only products that are formed. In such
cases, an analysis of the fuel sample and the products of combus-
tion are necessary to provide data for a correction cal-culation.
The standard gross calorific value is then determined from the
measured gross calorific value and the analysis data.
The gross calorific value Ho is formed as the quotient of the
amount of heat liberated upon total combustion of a solid or liq-
uid fuel and the weight of the fuel sample. The compounds com-
prising the fuel that contain water must be present in liquid state
after the combustion.
The formula for the calorific value is
Ho = (CV * DT – Qext) / m
where
Ho Calorific value
m Mass of the sample
DT Measured and corrected increase in temperature
Qext All external energy originating from the ignition wire, the
ignition aids, the combustion aids and the formation of acids
CV C value (thermal capacity) of the calorimeter
The heat value Hu is equal to the gross calorific value less the
energy of condensation of the water that was contained in the fuel
and was formed by the combustion. The heat value is the more
important quantity for technical purposes, since in all important
technical applications, the heat value is the only quantity that can
be evaluated in terms of energy.
For information on the fundamental principles of calcula-
tion for gross calorific value and heat value, please refer
to the applicable standards (for example: ISO 1928, ASTM
240, ASTM 5865 and ASTM 4809, GB T213).
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