Functional description
5
gas-lab
Q1
Page 29
5 Functional description
5.1
Gas quality
module
The
gas-lab
Q1 measuring system is a device for measuring the gas quality of
natural gas. It measures the infrared absorption of hydrocarbons and carbon
dioxide (CO
2
) and also the thermal conductivity. The following variables are
directly determined based on these measurements:
Hs
– Heating value superior, equal to GCV – gross calorific value
standard density Rho
s
concentration xCO
2
as mole fraction
Further variables are derived from these direct variables, such as:
Wobbe index superior Ws
Methane number MN
Composition of the natural gas consisting of 10 components from C1 to
C8+ as well as N
2
and CO
2
.
Hi
– Heating value inferior, equal to NCV – net calorific value
saturated Hs/GCV and Hi/NCV (gas with H
2
O saturation)
When the device is started, the evaluation computer reads the calibration data
out of the non-volatile memory of the sensor system and starts to measure.
Therefore, make sure to switch on the sensor system either before or together
with the evaluation computer. The measuring operation may only start after the
Q1 has been successfully calibrated (see 5.1.2) and if the process gas is
injected to path 1 with sufficient pressure. The sensor system is furnished with a
pressure switch that detects whether gas is flowing or not.
The sensor system must have reached its operating temperature of about 55 to
60 °C before the device is ready to operate. It may take up to one hour to heat
up a cold device. The evaluation computer waits until the operating temperature
has been reached before indicating valid measurements. View the temperature
of the sensor system in the
Process values
display (see 5.1.1.2).