Technical Description
HDK-CNG_EN_03_2016
21
Adsorption
Humid natural gas is delivered to the dryer from a compressor. From here, the
natural gas flows upwards through the absorption vessel, which is pressurised. In
so doing, the drying agent dehumidifies the natural gas. The dry natural gas is
directed to the pipework network via the natural gas outlet on the dryer.
Regeneration (running in parallel to the adsorption)
At the same time the other vessel is prepared for a renewed take-up of humidity.
This process is called regeneration.
The regeneration is subdivided into the phases: expansion, dehumidification, and
pressure build-up.
With the
dewpoint-sensing control
option, the regeneration phase is followed by a
standby phase.
Expansion phase
Gas pressure in the adsorbing vessel is relieved by an f-stop from compressor
outlet pressure to compressor input pressure. This flow rate makes a sudden
audible sound.
Dehumidification phase
Before the outlet to the pipework network, dried natural gas is redirected. Via a
pressure reducing valve and an f-stop, a partial flow is generated. This partial
flow (regeneration gas) is heated by a heating unit. The heated, dried
regeneration gas flows through the regenerating vessel from top to bottom. This
causes the flow of regeneration gas to absorb the humidity stored in the drying
agent.
Then a water separator removes the humidity from the regeneration gas, now
cooled, and supplies it to the operator for further use.
Pressure build-up phase
After dehumidification, the pressure in the regenerated vessel is built up to
compressor inlet pressure, so that the switchover from regeneration to adsorption
can take place at operating pressure level.
Standby phase (only with the dewpoint-sensing control option)
When in standby phase, the fully regenerated vessel is ready for absorption
operation. The system is switched to this chamber, as soon as the measured
dewpoint at the natural gas outlet has reached the set dewpoint value for
switchover.
Switchover
When the drying agent in the adsorbing vessel has taken up a sufficient level of
humidity, then the switchover between the vessels will be effected between the
vessels. Following switchover, the above-described process is repeated, with the
adsorption and regeneration now taking place in the respective different vessel.
