Methanol Synthesis

In this tutorial you will model the industrial synthesis of methanol from synthesis gas (CO + 2 H2 → CH3OH) in DWSIM's Classic UI. This is the capstone tutorial: it combines compression, equilibrium reaction, separation, and (optionally) a recycle loop.

What you will learn

• How to design a complete synthesis loop with multiple unit operations
• How to model methanol synthesis at high pressure
• How to balance per-pass conversion with overall conversion via recycle

Prerequisites

• Completed Ammonia Synthesis and Recycle Loops

Process Overview

Methanol from syngas (CO + CO2 + H2):

CO + 2 H2 → CH3OH (exothermic, equilibrium-limited)

Industrial conditions: 50-100 bar, 200-300 °C, copper-zinc-alumina catalyst. Per-pass conversion is only 15-25%, so unconverted syngas must be recycled.

We start with single-pass model; recycle is an exercise.

Process Flow Diagram

graph LR
    F["Syngas<br/>2:1 H2:CO<br/>30 bar"] --> C["C-1<br/>Compressor<br/>80 bar"]
    C --> H["H-1<br/>Heater<br/>525 K"]
    H --> R["R-1<br/>Eq. Reactor"]
    R --> CL["CL-1<br/>Cooler<br/>308 K"]
    CL --> SEP["SEP-1<br/>Separator"]
    SEP -->|Gas| PG["Recycle Gas"]
    SEP -->|Liquid| MeOH["Crude Methanol"]

Key Design Parameters

Parameter	Value
Compounds	Hydrogen, Carbon monoxide, Methanol
Property Package	Peng-Robinson
Feed	3 mol/s (2 H2 + 1 CO), 300 K, 30 bar
Compressor outlet	80 bar, 75% efficiency
Reactor T	525 K (252 °C), isothermal
Cooler outlet	308 K
ln(Keq)	9143/T - 29.07

Step-by-Step in the Classic UI

1. Set up

File > New Chemical Process Model:

• Compounds: Hydrogen, Carbon monoxide, Methanol
• Property Package: Peng-Robinson

Why Peng-Robinson for syngas?

PR handles high-pressure light gases and the supercritical-like behavior of H2 well. Methanol's hydrogen-bonding contribution is weaker at the elevated reactor temperature, so PR's accuracy is acceptable for this synthesis loop.

2. Define the methanol synthesis reaction

Edit > Simulation Settings > Reactions → Add Equilibrium:

• Name: MeOH_Synth
• Stoichiometry: Carbon monoxide = -1, Hydrogen = -2, Methanol = +1
• Base compound: Methanol, Phase: Vapor, Basis: Activity
• ln(Keq): 9143/T - 29.07

Create Reaction Set MeOHSet containing it.

Why an Equilibrium Reactor?

Like ammonia synthesis, MeOH synthesis is equilibrium-limited at industrial T,P. The Equilibrium Reactor gives the thermodynamic ceiling on yield; real reactors approach but do not reach it, and recycling unreacted syngas is what drives overall conversion above 95%.

Why high pressure (80 bar)?

CO + 2 H2 → CH3OH reduces 3 mol of gas to 1 mol; high P shifts the equilibrium toward MeOH per Le Chatelier. Industrial low-pressure methanol plants run at 50-100 bar, balancing yield improvement against compression cost.

3. Build the train

Drag and configure (mirroring the ammonia synthesis tutorial pattern):

1. Material Stream Syngas: T=300 K, P=30 bar, total molar flow=3 mol/s, mole fractions: H2=0.667, CO=0.333, MeOH=0
2. Compressor C-1: Adiabatic, outlet=80 bar, η=75%
3. Material Stream Comp-Out (empty)
4. Heater H-1: outlet T=525 K
5. Material Stream Hot (empty)
6. Equilibrium Reactor R-1: Isothermal, Reaction Set=MeOHSet
7. Material Stream Reactor-Out (vapor outlet, empty)
8. Material Stream Reactor-Liq (liquid outlet, empty)
9. Cooler CL-1: outlet T=308 K
10. Material Stream Cooled (empty)
11. Separator Vessel SEP-1
12. Material Stream Recycle-Gas (empty)
13. Material Stream Crude-Methanol (empty)

Wire all connections with appropriate energy streams (W_comp, Q_rx, Q_cool).

4. Solve

F6 ON → Solve.

5. Inspect results

• Crude-Methanol stream Results: methanol mole fraction > 0.95 (because of MeOH's much higher BP than H2/CO)
• Recycle-Gas Results: H2-rich (because each mol CO converted consumes 2 mol H2), still contains unreacted CO
• R-1 Results: per-pass CO conversion (15-30%)
• W_comp Energy: compression power

Results and Validation

Variable	Expected
Per-pass CO conversion	15-30%
Crude methanol purity	> 0.95 mole frac
Recycle gas H2/CO ratio	> 2.0 (H2-rich)

Expected results

Equilibrium-limited per-pass conversion at 525 K and 80 bar. Cooled liquid is high-purity methanol due to BP differences.

Understanding the Results

Methanol synthesis is a textbook equilibrium-limited reactor design:

• Le Chatelier: 3 mol gas → 1 mol product, so high P shifts equilibrium toward products
• Temperature: low T favors equilibrium, but catalyst needs ~250 °C
• Recycle: per-pass conversion is low; recycling unreacted syngas pushes overall conversion above 95%

In a real plant: recycle compressor + small purge to remove inerts, then distillation to remove water and light ends from the crude methanol.

Automating This Tutorial

Files in this repository

• Python script: examples/advanced/07_methanol_synthesis.py
• Pre-built flowsheet: examples/saved/methanol_synthesis.dwxmz

FluentAPI (Python)MCP Server (JSON-RPC)LLM Prompt

See examples/advanced/07_methanol_synthesis.py in the DWSIM.Tutorials repository.

dwsim.reaction.define_equilibrium, then dwsim.unitop.add for each operation in sequence.

Output may vary

Results depend on the LLM's reasoning quality and tool-use accuracy. Always verify the simulation matches your intent before relying on the numbers.

Use DWSIM (via the MCP server) to build the following simulation:

- Create a flowsheet called "MethanolSynthesis"
- Add Hydrogen, Carbon monoxide and Methanol as compounds; set the
  property package to "Peng-Robinson"
- Define an equilibrium reaction "MeOH_Synth" with stoichiometry
  CO = -1, H2 = -2, Methanol = +1; base compound = Methanol,
  phase = Vapor, basis = Activity, ln(Keq) = 9143/T - 29.07; add it
  to a new reaction set "MeOHSet"
- Add a material stream "Syngas" at 300 K and 30 bar with total molar
  flow = 3 mol/s and mole fractions H2 = 0.667, CO = 0.333, MeOH = 0
- Add a Compressor "C-1" (adiabatic, outlet P = 80 bar, efficiency
  = 75%) with energy stream W_comp
- Add a Heater "H-1" with outlet T = 525 K
- Add an Equilibrium Reactor "R-1" in isothermal mode using reaction
  set MeOHSet, with energy stream Q_rx
- Add a Cooler "CL-1" with outlet T = 308 K, energy stream Q_cool
- Add a Separator Vessel "SEP-1" with vapor outlet "Recycle-Gas" and
  liquid outlet "Crude-Methanol"
- Connect: Syngas → C-1 → H-1 → R-1 → CL-1 → SEP-1
- Solve the flowsheet
- Report the per-pass CO conversion in R-1, the methanol mole
  fraction in Crude-Methanol, the H2/CO ratio in Recycle-Gas, and
  the energy flows W_comp, Q_rx and Q_cool

Exercises

1. Lower reactor T to 475 K. How does per-pass conversion change?
2. Increase pressure to 120 bar. Is the additional compression cost justified?
3. Add a Recycle logical operation: connect Recycle-Gas back to a Mixer at the Compressor inlet (with a small purge stream via a Splitter for inerts).
4. Add CO2 (10 mol%) to the feed and a second equilibrium reaction (CO2 + 3 H2 → CH3OH + H2O) for a more realistic syngas.

Further Reading

Selected references from the DWSIM technical bibliography. Click the DOI link to access each paper.

• Kai Hou & Ronald Hughes. (2001). The Kinetics of Methane Steam Reforming over a Ni/α-Al₂O₃ Catalyst. Chemical Engineering Journal. doi:10.1016/S1385-8947(00)00367-3
• Ding-Yu Peng & Donald B. Robinson. (1976). A New Two-Constant Equation of State. Industrial & Engineering Chemistry Fundamentals. doi:10.1021/i160057a011
• James H. Gary, Glenn E. Handwerk & Mark J. Kaiser. (2007). Petroleum Refining: Technology and Economics. CRC Press
• A. K. Myers & A. L. Myers. (1986). Numerical Solution of Chemical Equilibria with Simultaneous Reactions. J. Chem. Phys.

Next Steps

Congratulations! You have completed the advanced tutorial track in the Classic UI. You have built complete simulations of:

• Vapor-compression refrigeration
• Ammonia synthesis (Haber-Bosch)
• Aromatic distillation
• Natural gas processing
• Bioethanol fermentation
• Reverse osmosis desalination
• Methanol synthesis

Continue with the Features Track to explore TEA, LCA, and the AI Assistant.