CNG Gas Dryer
Function:
The compressed natural gas drying unit is designed to remove moisture from compressed natural gas, which is used to fuel motor vehicles at Automotive Gas Filling Compressor Stations (AGFCS). The drying unit works with one or more compressor stations simultaneously.
Moisture droplets are removed by absorbing the moisture vapors from natural gas compressed to 18 ÷ 24.5 mPa (184 ÷ 250 kgf / cm2) passing through the adsorber.
The adsorber is a high pressure vessel filled with adsorbent and can be implemented in two ways:
– a special high pressure tank on flanged joints;
– a high-pressure cylinder with a volume of 80 liters.
The adsorber is filled with silica gel (KSMG 4 ÷ 6 mm), a type of adsorbent which absorbs moisture from the gas passing through it. In the process, the moisture-saturated adsorbent loses its properties and needs to be recovered (regenerated). Recovery is carried out by extracted and heated to the required temperature natural gas. The natural gas drying unit includes two or more adsorbers to ensure a continuous process of natural gas drying and recovery of the adsorbent properties.
Specifications:
Processing medium
Natural gas, noncorrosive, explosive, airborne concentrations from 5 to 15 % in volume in accordance to the State Standard GOST 5542-87
Work pressure, mPa (kgf / cm2)
18 ÷ 24,5 (184 ÷ 250)
Discharge capacity, nm3 / h
1500
The temperature of the gas supplied for the adsorbent recovery, К (°С)
333 ÷ 423 (60 ÷ 150)*
The temperature of the gas supplied for drying, К (°С)
274 ÷ 333 (1 ÷ 60)
Relative humidity of natural gas supplied for drying
moisture saturation state up to 100%, under the conditions of entry to the highest level of compression by the compressor
The moisture content in the compressed natural gas, g/m3
0,009 ± 0,003**
The drying time of compressed natural gas, machine hours
≥ 2, but ≤ 30
The cycle of the technological process of the adsorbent recovery:
– heating time of the adsorber, hours
– adsorbent recovery time, machine hours
≤ 0,3*
≥ 2, but ≤ 8*
The cycle of the technological process of the adsorbent cooling:
– time of the unforced cooling of the adsorber, hours
– time of the forced cooling of the adsorbent, hours
≤ 3
≤ 0,3***
The pressure of gas supplied for the recovery of the adsorber, MPa (kgf / cm2)
13 (132)
Gas supplied for the adsorber recovery
heated, extracted gas after the last level of compression in the compressor
Type of adsorbent
silica gel KSMG (Ø 4 ÷ 6 mm)****
* The parameter depends on the specifications of the pipeline and shut-off valves and is limited by the maximum operating temperature of the adsorbent.
** The moisture content in the compressed natural gas is regulated by settings adjustment in the control unit of the drying unit. Upon completion of the technological process, the drying unit allows to obtain the final product (compressed natural gas) of the required and specified quality.
*** Forced technological process of adsorbent cooling is used if necessary and in the summer production period.
**** Another type of adsorbent can be used but its characteristics should not impair the technological process of the compressed natural gas drying unit.
The technological process of the compressed natural gas drying unit operation can work in both automatic and semi-automatic modes.
Basic equipment:
– a section of adsorbers with the adsorbent;
– a heater of compressed natural gas *****;
– a set of pipeline and shut-off valves;
– an automatic control unit of technological process of drying and recovery of the adsorbent.
***** A heater can be used separately to heat other liquids and gases in local technological processes.