1070-4272/01/7409-1539$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 9, 2001, pp. 1539!1545. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 9,
2001, pp. 1494!1499.
Original Russian Text Copyright + 2001 by Aleksandrov, Belyakov, Varganov, Sarge.
PROCESSES AND EQUIPMENT
OF CHEMICAL INDUSTRY
Method for Measuring the Combustion Heat of Natural Gas
with Isothermal Calorimeter
Yu. I. Aleksandrov, V. I. Belyakov, V. P. Varganov, and S. Sarge
Mendeleev Russian Research Institute of Metrology, State Unitary Enterprise, St. Petersburg, Russia
Physicotechnical Institute, Braunschweig, Germany
Received April 28, 2000; in final form, June 2001
Abstract-Factors that are to be taken into account in developing a calorimetric technique are considered.
The possible deviations of temperatures at the inlet and outlet of gases in the calorimeter from the nominal
values are evaluated and an example of such estimate is given for the case of methane burning in batch and
continuous operation modes. The necessity for taking into account the humidity of gases fed into the calorim-
eter burner is demonstrated. The proposed method was used to perform absolute measurements of the combus-
tion heat of methane.
The proposed technique for measuring the combus-
tion heat of natural gas was developed for an isother-
mal calorimeter of original design, described in detail
previously [1, 2]. Our goal was to make introduction
of any corrections unnecessary. In this case, the gas
combustion heat can be calculated from the amount of
burnt gas and the measured heat power P
in its combustion.
From the existing wide variety of definitions of the
notion [combustion heat of a gas]  follows that,
to solve the problem in question, it is necessary (1) to
refine the temperature to which the combustion heat is
reduced and (2) to ensure, taking into account item 1,
that the temperatures of gases fed into the burner and
discharged combustion products are equal.
Further, the following standard combustion condi-
tions were used: T
= 101.325 kPa.
Another important factor to be taken into account
in developing a calorimetric technique is the content
of water vapor in the gas being burnt. The following
variants are distinguished : (1) gas to be burnt is
saturated with water vapor prior to being fed into
the calorimeter; in this case, combustion heat related
to 100% humid gas is measured; (2) gas to be burnt is
dried prior to being fed into the calorimeter; the ob-
tained combustion heat is related to dry gas ; and
(3) gas to be burnt is fed into the calorimeter with
the humidity it has; the measured value is the com-
bustion heat of real gas.
Thus, the above circumstance is to be taken into
account in comparing gas combustion heat values
obtained by different methods. The most logical and
promising method is direct measurement of the com-
bustion heat of a real gas.
The measured heat effect in gas burning may be
over- or underestimated for internal or external
reasons. To internal factors are related effects depend-
ing both on the difference of heat capacities of gases
fed into the calorimeter and combustion products and
on heat of vaporization (condensation) of water vapor
arriving at the calorimeter together with feed gases
and formed as a combustion product. Therefore, the
calorimetric procedure should reduce the effect of
internal factors to the maximum possible extent.
External effects are associated with heat exchange
between the calorimeter and the environment. Their
influence can be substantially reduced by heat insula-
tion, and attention was given to this fact in designing
Gases fed into the calorimeter were preliminarily
thermostated in a water thermostat at 25oC. The tem-
perature maintained in the KTT-7 calorimeter was
chosen in such a way that the temperature in the heat-
ing zone of the thermosiphon was close to 25oC. The
combustion products at the heat-exchanger outlet
acquired a temperature close to this value. Below, we
estimate possible deviations of the above temperature
from the nominal value on condition that the error
associated with such a deviation does not exceed
Let us calculate the correction for deviation of the
temperature of incoming gases and combustion gases