puran-water/degasser-design-mcp

Degassing/Stripping Tower Design MCP Server

Air stripping tower design tool implementing Perry's Handbook correlations with PHREEQC geochemical speciation.

Implementation Status

Tier 1: Heuristic Sizing (Complete)

• Perry's Handbook correlations (Eckert GPDC, HTU/NTU methods)
• PHREEQC integration for pH-dependent speciation
• Robbins pressure drop correlation for packed beds
• Blower type selection and power calculations
• 9 standard packings from Perry's Table 14-13
• Execution time: <1 second

Tier 2: Staged Column Simulation (Complete ✅)

• PHREEQC equilibrium stage calculations
• Counter-current flow with single-phase Murphree efficiency (gas phase)
• Mass balance from conservation equations (liquid phase)
• Mass balance closure: <5% (VOC, CO2), <25% (H2S)
• Convergence stable for N<50 stages (200 iteration limit, 2% tolerance)
• pH-coupled speciation with water chemistry integration
• Execution time: 10-30 seconds

Tier 3: WaterTAP Economic Costing (Complete ✅)

• Validated cost correlations from upstream libraries
  • Blower: QSDsan (qsdsan.equipments._aeration.Blower)
  • Vessel: WaterTAP (watertap.costing.unit_models.cstr)
  • Packing & Internals: Industry standard values
• Economic metrics: NPV, LCOW, payback period
• CEPCI cost escalation to 2025
• Full provenance documentation
• Execution time: <5 seconds

Technical Overview

The server calculates packed tower dimensions for air stripping applications accounting for pH-dependent aqueous speciation. For weak acids (H₂S, CO₂), only the neutral molecular form is strippable while ionic species remain in solution.

pH-Dependent Speciation

H₂S System (pKa₁ = 7.0):

• pH 6.0: α₀ = 0.896 (89.6% H₂S, 10.4% HS⁻)
• pH 7.0: α₀ = 0.500 (50% H₂S, 50% HS⁻)
• pH 8.0: α₀ = 0.091 (9.1% H₂S, 90.9% HS⁻)

CO₂ System (pKa₁ = 6.35):

• pH 6.0: α₀ = 0.688 (68.8% CO₂, 31.2% HCO₃⁻)
• pH 7.0: α₀ = 0.184 (18.4% CO₂, 81.6% HCO₃⁻)
• pH 8.0: α₀ = 0.022 (2.2% CO₂, 97.8% HCO₃⁻)

The strippable fraction α₀ is calculated using PHREEQC equilibrium modeling and applied to the effective Henry's constant.

Applications

• H₂S Removal: Groundwater treatment, odor control. Requires pH < 6.5 for effective stripping.
• CO₂ Stripping: RO pretreatment, alkalinity reduction. Requires pH < 5.5 for >90% conversion.
• VOC Removal: Groundwater remediation (TCE, PCE). pH-independent for neutral compounds.

Quick Start

Installation

# Clone repository
cd /mnt/c/Users/hvksh/mcp-servers/degasser-design-mcp

# Activate virtual environment (Python 3.12)
source ../venv312/bin/activate  # Linux/WSL
# OR
..\venv312\Scripts\activate  # Windows

# Install dependencies
pip install -r requirements.txt

# Run tests
pytest tests/ -v

MCP Server Configuration

Add to your MCP settings (e.g., Claude Desktop config):

{
  "mcpServers": {
    "degasser-design-mcp": {
      "command": "/mnt/c/Users/hvksh/mcp-servers/venv312/Scripts/python.exe",
      "args": ["-m", "server"],
      "cwd": "/mnt/c/Users/hvksh/mcp-servers/degasser-design-mcp",
      "env": {}
    }
  }
}

Available MCP Tools

1. heuristic_sizing - Fast Tower Design (<1s)

Size a packed tower air stripper using Perry's Handbook correlations.

Input Parameters:

{
  "application": "H2S",              # "H2S", "CO2", "VOC", or "general"
  "water_flow_rate_m3_h": 60.0,     # m³/h
  "inlet_concentration_mg_L": 32.0, # mg/L
  "outlet_concentration_mg_L": 0.05,# mg/L
  "air_water_ratio": 34.0,          # Volumetric ratio
  "temperature_c": 25.0,            # °C
  "water_ph": 6.0,                  # Required for H2S/CO2
  "packing_id": "Plastic_Pall_Rings_25mm"  # Optional
}

Output (without blower sizing):

{
  "tower_diameter_m": 2.12,
  "tower_height_m": 4.94,
  "packing_height_m": 4.44,
  "packing_name": "Plastic Pall Rings",
  "packing_size_mm": 25.0,
  "design_velocity_m_s": 0.161,
  "flooding_velocity_m_s": 0.230,
  "ntu": 7.96,
  "htu_m": 0.465,
  "lambda_factor": 13.94,
  "removal_efficiency_percent": 99.97,
  "air_flow_rate_m3_h": 2040.0
}

Output (with blower sizing - include_blower_sizing=True):

{
  "tower_diameter_m": 2.12,
  "tower_height_m": 4.94,
  "packing_height_m": 4.44,
  "packing_name": "Plastic Pall Rings",
  "packing_size_mm": 25.0,
  "design_velocity_m_s": 0.161,
  "flooding_velocity_m_s": 0.230,
  "ntu": 7.96,
  "htu_m": 0.465,
  "lambda_factor": 13.94,
  "removal_efficiency_percent": 99.97,
  "air_flow_rate_m3_h": 2040.0,

  "blower_specs": {
    // Pressure Drop Breakdown
    "packed_bed_pressure_drop_pa": 1823.4,
    "inlet_distributor_pressure_drop_pa": 249.1,
    "outlet_distributor_pressure_drop_pa": 249.1,
    "demister_pressure_drop_pa": 373.6,
    "momentum_losses_pa": 87.3,
    "ductwork_silencer_pressure_drop_pa": 182.3,
    "elevation_head_pa": 58.2,
    "safety_factor_pa": 362.2,
    "total_system_pressure_drop_pa": 3385.2,
    "total_system_pressure_drop_inches_h2o": 13.59,
    "total_system_pressure_drop_psig": 0.49,

    // Blower Selection
    "blower_type": "Multistage Centrifugal",
    "thermodynamic_model": "Isothermal",
    "compression_ratio": 1.033,
    "discharge_pressure_pa": 104710.2,
    "discharge_pressure_psig": 0.49,

    // Temperatures
    "inlet_temperature_c": 25.0,
    "discharge_temperature_c": 25.0,

    // Power Requirements
    "shaft_power_kw": 10.2,
    "motor_power_kw": 11.1,
    "motor_power_hp": 14.9,

    // Efficiencies
    "blower_efficiency": 0.70,
    "motor_efficiency": 0.92
  }
}

Example Usage:

# Via MCP tool call
result = await mcp__degasser_design_mcp__heuristic_sizing(
    application="H2S",
    water_flow_rate_m3_h=60.0,
    inlet_concentration_mg_L=32.0,
    outlet_concentration_mg_L=0.05,
    air_water_ratio=34.0,
    water_ph=6.0,
    packing_id="Plastic_Pall_Rings_25mm"
)

2. combined_simulation_mcp - Tier 1 + Optional Tier 2 + Optional Tier 3

Run fast heuristic sizing (Tier 1), optionally continue with rigorous PHREEQC simulation (Tier 2), and optionally calculate economic costing (Tier 3).

Input Parameters:

{
  "application": "H2S",
  "water_flow_rate_m3_h": 50.0,
  "inlet_concentration_mg_L": 30.0,
  "outlet_concentration_mg_L": 0.5,
  "air_water_ratio": 40.0,
  "temperature_c": 25.0,
  "water_ph": 6.0,
  "run_tier2": true,                    # Set to true for Tier 2 simulation
  "num_stages_initial": 20,             # Fixed stage count (or None for auto-find)
  "find_optimal_stages": false,         # If true, uses bisection to find optimal N
  "run_tier3": true,                    # Set to true for economic costing
  "packing_type": "plastic_pall"        # Packing material: plastic_pall, ceramic_raschig, etc.
}

Output (with Tier 2 and Tier 3):

{
  "request": {...},                      # Echo of input parameters
  "result": {...},                       # Tier 1 results (tower dimensions, blower)
  "tier2": {
    "tower_height_m": 22.6,
    "theoretical_stages": 20,
    "HETP_m": 1.13,
    "stage_profiles": {
      "liquid_conc_mg_L": [...],        # Concentration profile (N+1 points)
      "gas_conc_ppm": [...],
      "pH": [...],                       # pH profile showing drift
      "alpha_0": [...]                   # Strippable fraction at each stage
    },
    "convergence_info": {
      "inner_iterations": 98,
      "converged": true,
      "mass_balance": {
        "mass_in_mg_h": 1500000.0,
        "mass_out_water_mg_h": 461985.2,
        "mass_stripped_mg_h": 1148197.9,
        "error_fraction": 0.073,         # 7.3% error
        "passed": "True"
      }
    }
  },
  "tier3": {
    "capital_costs": {
      "air_blower_system": 150000,
      "packed_tower_shell": 13909,
      "packing_media": 934,
      "tower_internals": 1396
    },
    "operating_costs": {
      "blower_electricity": 261,         # USD/year
      "packing_replacement": 47          # USD/year
    },
    "total_capex": 166238,               # Total capital expenditure
    "total_annual_opex": 307,            # Total annual operating cost
    "economic_metrics": {
      "npv_usd": -169313,                # Net present value (30 years)
      "lcow_usd_per_m3": 0.086,          # Levelized cost of water
      "lcow_usd_per_1000gal": 0.325,     # Levelized cost per 1000 gallons
      "payback_years": 541,              # Simple payback period
      "annualized_total_cost_usd_per_year": 16920,
      "capital_recovery_factor": 0.0999,
      "annual_water_production_m3": 197100
    },
    "cost_breakdown_pct": {
      "air_blower_system": 90.2,         # Blower dominates CAPEX
      "packed_tower_shell": 8.4,
      "packing_media": 0.6,
      "tower_internals": 0.8
    }
  }
}

3. list_available_packings - Query Packing Catalog

List all available packings with specifications.

Output:

{
  "packings": [
    {
      "packing_id": "Plastic_Pall_Rings_25mm",
      "name": "Plastic Pall Rings",
      "material": "Plastic",
      "nominal_size_mm": 25.0,
      "packing_factor_m_inv": 180.0,
      "surface_area_m2_m3": 206.0,
      "void_fraction": 0.90
    },
    ...
  ],
  "count": 9
}

Design Methodology

1. Speciation Calculation

PHREEQC calculates equilibrium speciation for pH-dependent systems:

# PHREEQC solution definition
solution = pp.add_solution({'pH': 6.0, 'temp': 25.0, 'S(-2)': 32.0})

# Calculate strippable fraction
α₀ = solution.species_molalities['H2S'] / solution.total_element('S', units='mol')

Note: total_element() requires units='mol' to avoid unit mismatch with species_molalities (mol/kgw).

2. Tower Height Calculation

Stripping Factor (Perry's Eq. 14-16):

λ = H_eff × (G/L)    where H_eff = H × α₀

Number of Transfer Units (Perry's Eq. 14-19, Colburn):

NOG = ln[(Cin/Cout - 1/λ) / (1 - 1/λ)] / ln(λ)

Packing Height (Perry's Eq. 14-15):

Z = NOG × HOG × 1.2    (20% safety factor)

HTU values from empirical correlations or vendor data (typical: 0.3-1.0 m)

3. Tower Diameter (Eckert GPDC)

Flooding Velocity (Perry's Eq. 14-142):

uflood = Csf × √[(ρL - ρG)/ρG] × √(ε/Fp)

Where Csf from Eckert chart (Fig. 14-55) based on flow parameter FLG = (L/G)√(ρG/ρL)

Design Conditions:

• Operating velocity: 70% of flooding
• Tower diameter: D = √(4QG/(π × udesign))

4. Pressure Drop and Blower Sizing

Packed Bed (Robbins correlation, Perry's Eq. 14-145):

ΔP_packed = Robbins(L, G, rhol, rhog, mul, H, Fpd)  # fluids library

System Components:

• Packed bed (50-60% of total)
• Distributors: 1.0" H₂O each (inlet/outlet)
• Demister: 1.5" H₂O
• Momentum losses, ductwork, elevation head
• Total system ΔP × 1.12 safety factor

Blower Selection:

Power Calculations:

• Isothermal (β ≤ 1.2): W = P₁Q·ln(P₂/P₁)/η
• Polytropic (1.2 < β ≤ 1.5): Uses polytropic exponent n from efficiency
• Adiabatic (β > 1.5): Standard adiabatic compression with γ=1.4

Motor sizing includes 92% motor efficiency. Vendor data should be used for final design.

Design Tool Selection

Tier 1: Heuristic Sizing

Use for: Preliminary design, screening alternatives Limitations:

• Assumes constant pH throughout tower
• May underestimate height by 50-200% for pH > 7.0 with H₂S/CO₂
• Not suitable for bid preparation

Warnings issued when:

• pH ≥ 7.0 for H₂S or CO₂ applications
• Air/water ratio < 15 (weak driving force)
• Alkalinity > 500 mg/L CaCO₃

Tier 2: Staged Simulation (Complete ✅)

Use for: Final design when pH effects are significant Features:

• Stage-by-stage pH and concentration profiles
• Counter-current flow with adaptive Murphree efficiency
• PHREEQC equilibrium at each stage
• Water chemistry integration (RO MCP compatible)

Performance:

• VOC: <10% mass balance error (production-ready)
• CO2: <5% mass balance error (pH 4-8 supported)
• H2S: <25% mass balance error (acceptable for engineering design)
• Convergence stable up to 50 stages with 200 iteration limit
• Correct stripping direction verified for all applications

Tier 3: Economic Costing (Complete ✅)

Use for: Cost estimation, packing comparison, economic optimization Features:

• Equipment CAPEX: Blower system, tower shell, packing, internals
• Annual OPEX: Electricity, packing replacement
• Economic metrics: NPV, LCOW, payback period
• Validated cost correlations with full provenance
• CEPCI cost escalation to 2025 USD

Cost Correlations:

• Blower: QSDsan (qsdsan.equipments._aeration.Blower) - three-tier sizing
• Vessel: WaterTAP (watertap.costing.unit_models.cstr.cost_cstr)
• Packing: Industry standard values with CEPCI escalation
• Internals: Distributors, demisters, support grids

Packing Catalog

9 standard packings from Perry's Handbook Table 14-13:

Selection Guidelines:

• H₂S/CO₂: Use plastic or ceramic (corrosion-resistant)
• VOC: Plastic packing typically preferred
• Smaller packing (25mm): Lower HTU (better efficiency), larger diameter, higher cost
• Larger packing (50mm): Higher HTU, smaller diameter, lower cost

Validation

Test Coverage: 58 tests passing

• Perry's TCE benchmark (38 → 0.00151 mg/L): Within 5% of handbook
• PHREEQC speciation for H₂S and CO₂: Validated across pH 5-9
• Robbins pressure drop: <1% error vs fluids library
• Blower power calculations: Validated against thermodynamic models
• Tier 2 mass balance and physics validation for all applications
• Blower costing validation across three tiers (small/medium/large)

Architecture

Three-Tier Design:

1. Tier 1: Perry's correlations with PHREEQC speciation (Complete ✅)
2. Tier 2: Equilibrium stage simulation (Complete ✅)
3. Tier 3: WaterTAP economic costing (Complete ✅)

Directory Structure

degasser-design-mcp/
├── .mcp.json                    # MCP server configuration
├── README.md                    # This file
├── REMAINING_IMPLEMENTATION_PLAN.md  # Detailed roadmap for Phases 2-3
├── server.py                    # FastMCP server implementation ✓
├── requirements.txt             # Python dependencies ✓
├── .env.example                 # Environment variable template ✓
├── .gitignore                   # Git ignore rules ✓
├── tools/                       # MCP tool implementations
│   ├── __init__.py              # ✓
│   ├── heuristic_sizing.py      # Tier 1 heuristic sizing ✓
│   ├── simulation_sizing.py     # Tier 2 PHREEQC staged simulation ✓
│   ├── watertap_costing.py      # Tier 3 WaterTAP economic costing ✓
│   └── schemas.py               # Pydantic validation models ✓
├── utils/                       # Utility modules
│   ├── __init__.py              # ✓
│   ├── tower_design.py          # Perry's correlations (diameter, height) ✓
│   ├── packing_properties.py    # Packing catalog interface ✓
│   ├── speciation.py            # PHREEQC pH-dependent speciation ✓
│   ├── henry_constants.py       # Henry's law database ✓
│   ├── helpers.py               # Eckert GPDC, HTU/NTU methods ✓
│   ├── pressure_drop.py         # Robbins correlation & accessory ΔP ✓
│   ├── blower_sizing.py         # Power calculations (fluids.compressible) ✓
│   ├── water_chemistry.py       # RO MCP-compatible water chemistry ✓
│   ├── economic_defaults.py     # CEPCI escalation, QSDsan imports ✓
│   ├── costing_parameters.py    # WaterTAP parameter blocks ✓
│   ├── degasser_costing_methods.py  # Equipment costing methods ✓
│   ├── import_helpers.py        # Dependency detection ✓
│   ├── job_manager.py           # Background job management for Tier 2/3 ✓
│   ├── tier2_cli.py             # CLI runner for Tier 2 PHREEQC simulation ✓
│   └── tier3_cli.py             # CLI runner for Tier 3 WaterTAP costing ✓
├── databases/                   # Design databases
│   ├── pack.json                # Packing specifications ✓
│   ├── henrys_law.db            # VOC Henry's constants ✓
│   ├── voc_phases.dat           # PHREEQC custom phases ✓
│   └── voc_properties.json      # VOC properties ✓
└── tests/                       # Unit and integration tests
    ├── test_tower_design.py     # Perry's benchmark validation ✓
    ├── test_voc_phases.py       # PHREEQC integration tests ✓
    ├── test_simulation_sizing.py # Tier 2 simulation tests ✓
    ├── test_blower_sizing.py    # Blower sizing and pressure drop tests ✓
    └── test_blower_costing_validation.py # Blower costing validation ✓

Example Usage

# H₂S stripping at pH 6.0
result = await heuristic_sizing(
    application="H2S",
    water_flow_rate_m3_h=60.0,
    inlet_concentration_mg_L=32.0,
    outlet_concentration_mg_L=0.05,
    air_water_ratio=34.0,
    water_ph=6.0
)

# Results
# Tower: 2.12 m dia × 4.94 m height
# Packing: 4.44 m depth
# Air flow: 2,040 m³/h
# Strippable fraction at pH 6.0: 89.6%

Note: At pH 6.0, 10.4% of sulfide remains as non-strippable HS⁻. Lower pH to 5.5 for >95% removal.

References

Design Correlations

1. Perry's Chemical Engineers' Handbook, 8th Edition, Section 14
2. PHREEQC Version 3 (Parkhurst & Appelo, 2013), USGS
3. fluids library (CalebBell/fluids) for thermodynamics and pressure drop
4. Robbins, L.A. (1991), Chemical Engineering Progress, 87(5), 87-91

Economic Costing

5. QSDsan v1.4.2+ - Blower equipment costing - https://github.com/QSD-Group/QSDsan
6. WaterTAP v0.15.0+ - Vessel costing framework - https://github.com/watertap-org/watertap
7. BioSTEAM v2.x - CEPCI cost escalation indices - https://github.com/BioSTEAMDevelopmentGroup/biosteam

For complete cost provenance documentation, see COSTING_REFERENCES.md

License

MIT License

Contact

GitHub: https://github.com/puran-water/degasser-design-mcp