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Molecular Sieve Dehydration Calculator

GPSA Section 20 · UOP · BASF · Zeochem

Molecular Sieve Dehydration Calculator
Professional-grade bed sizing for deep gas dehydration to <1 ppm water. Calculates sieve mass, vessel dimensions, MTZ, pressure drop, and regeneration requirements per GPSA Section 20 and UOP design guidelines.

Operating Conditions

MMscfd
psig
°F
Inlet conditions during adsorption cycle

Sieve Selection & Water Content

lb/MMscf
lb/MMscf
4A (Sodium Aluminosilicate)
Pore: 4Å · Capacity: 22% H₂O
Most common for NG; removes H₂O + CO₂ + H₂S in single step

Design Parameters

hours
ft/min
GPSA Recommended:
• Cycle: 8-24 hours typical
• Velocity: 40-80 ft/min
• H/D ratio: 2:1 to 4:1

About This Calculator

Professional molecular sieve dehydration bed sizing per GPSA Section 20. Calculates all critical design parameters for TSA systems.

Key Calculations:

  • Dynamic Capacity: Temperature and saturation corrections per GPSA Fig 20-37
  • MTZ Analysis: Mass transfer zone length and breakthrough margin
  • Ergun Equation: Pressure drop through packed bed
  • Z-Factor: Gas compressibility for actual flow
  • Regeneration: Heat duty and gas requirements

Design Basis:

  • 70% capacity utilization (conservative)
  • 15% upset factor for flow variations
  • Bed height ≥ 3× MTZ for reliability

Frequently Asked Questions

What does the molecular sieve design calculator do?

It designs molecular sieve dehydration beds per GPSA Section 20, calculating bed sizing, mass transfer zone (MTZ), pressure drop, and regeneration requirements.

What zeolite types are supported?

The calculator supports 3A, 4A, and 5A zeolite molecular sieves for gas dehydration applications.

What parameters does it calculate?

It calculates bed sizing, MTZ length, pressure drop, and regeneration requirements for molecular sieve dehydration systems.

What water dewpoint can molecular sieve dehydration achieve?

Molecular sieve dehydration achieves outlet water content of less than 1 ppm (less than 0.1 lb/MMSCF), making it suitable for cryogenic plant feed gas and LNG applications that require deep dehydration beyond the capability of glycol systems.

How is molecular sieve bed sizing calculated?

Bed sizing uses GPSA Section 20 methods including dynamic capacity with temperature and saturation corrections per GPSA Figure 20-37, mass transfer zone (MTZ) length for breakthrough analysis, and Ergun equation for pressure drop through the packed bed.

What are typical molecular sieve regeneration requirements?

Regeneration cycles are typically 8-24 hours on-stream. The regeneration step requires heated gas to desorb water from the sieve, followed by a cooling period. The calculator determines heat duty and gas requirements for complete bed regeneration.

What types of molecular sieve are available for gas dehydration?

Common types include 3A, 4A, and 5A zeolites, each with different pore sizes. Type 4A is most common for natural gas dehydration. The calculator accounts for sieve type, dynamic capacity, and performance corrections from GPSA and vendor guidelines.