Calculations for internal natural gas adsorption dehydration process

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Calculation and implementation standard for natural gas adsorption dehydration process: SY/T0076-2003

Known values and units:
Parameters related to natural gas:
- Natural gas processing capacity (V): Nm3/h, value = 3000
- Water content in natural gas (%): ppm, value = 750
- Operating pressure (P): MPa, value = 25
- Operating temperature (T): °C, value = 45
- Density of natural gas under standard conditions (ρ0): kg/m3, value = 0.77
- Density of water vapor in natural gas under operating conditions (ρ_water): kg/m3, value = 0.75

Parameters related to molecular sieves:
- Adsorbent model
- Average diameter of adsorbent (Dp): m, value = 0.004
- Equilibrium water capacity (%): 28
- Bulk density (ρB): kg/m3, value = 7000

Purification requirements:
- Dew point after purification: °C
- Adsorption time (τ): h, value = 8
- Regeneration time: h, value = 7
- Regeneration temperature: °C, value = 235
- Pressure difference (ΔP): MPa, value = 0.1

Calculation procedures:
- Density of natural gas under operating conditions (ρg, kg/m3): 163.1386
- Dynamic water capacity of adsorbent (Xs): 0.168
- Calculation of adsorbent quantity required:
- Water content after 1 hour of adsorption (G_water, kg/h): 1.6875
- Amount of water removed by the adsorbent per day (G1, kg/d): 40.5
- Volume of adsorbent required (Vw, m3): 0.149235
- Mass of adsorbent required (Gw, kg): 104.4643

Calculation of empty tower flow rate (using Radoux’s formula):
- Constant C: (0.25–0.32), value = 0.28
- Mass flow rate of empty tower (Gg, kg/(m2·s)): 11.30932
- Flow rate of empty tower (v2, m/s): 0.069323
- Flow rate of empty tower (v2, m/min): 4.159402

Initial selection of tower diameter:
- Flow rate of natural gas under operating conditions (v1, m3/h): 14.15974
- D1, m: 0.268845
- D2, m: 0.423591
- Dm, m: 0.346218
- Rounded tower diameter, m: 0.35

Calculation of mass transfer zone length:
- Cross-sectional area of the bed: Water load (q), kg/(h·m2): 17.53898
- Relative humidity (Rs), %: 1
- Length of mass transfer zone **, m: 6.173367 (this is the length for silica gel-based mass transfer zones)
- Length of mass transfer zone **, m: 3.70402

Calculation of bed height:
- Cross-sectional area of the bed (F), m2: 0.096163
- Bed height (Ht), m: 1.551901