Dorulphwulf phdvxuhphqwv – IKA C 2000 control User Manual

Page 21

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IKA

-WERKE C 2000 basic / control

Ver. 04 08.07

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Combustion processes take place in a calorimeter under defined conditions. For this

purpose, the decomposition vessel is coated with a weighed out quantity of fuel

sample, the fuel sample is ignited, and the increase in temperature of the calorime-

ter system is measured. The specific gross calorific value of the sample is calculated

from:

the weight of the fuel sample

the heat capacity (C value) of the calorimeter system

the increase in temperature of the water within the inner vessel of the measuring

cell

To optimize the combustion process, the decomposition vessel is filled with pure

oxygen (99.95%). The maximum level of pressure of the oxygen atmosphere in the

decomposition vessel is 30 bar.

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 assumptions:

Depending on the mode that is set, the temperature of the fuel before the com-

bustion is 25 °C or 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 and sulfur dioxide.

Solid substances may be formed (for example ash).

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 combustion 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 liber-

ated upon total combustion of a solid or liquid fuel and the weight of the fuel sample.

The compounds comprising the fuel that contain water must be present in liquid

state after the combustion.

The heat value Hu is equal to the gross calorific value less the energy of condensa-

tion 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.

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