ToolFusion
📋 Case Study

Hellisheiði Geothermal Complex ORC Retrofit – Iceland

Low temperature differential limiting efficiency; silica scaling in plate heat exchangers; strict Icelandic environmental discharge limits

🏗️ Project Overview

Integration of 5 MW subcritical ORC unit to recover waste heat from 130°C geothermal brine after primary steam extraction

🎯 Challenge

Low temperature differential limiting efficiency; silica scaling in plate heat exchangers; strict Icelandic environmental discharge limits

🔧 Design Approach

Toluene-based ORC with double-pass brazed plate HX, active pH control loop, and real-time scaling index monitoring (LSI/S&BS)

📐 Design Diagram

Brine In Double-Pass
Brazed Plate HX ΔT_min = 4.2°C ORC
Toluene Turbine pH Control S&BS = −0.8 Real-time LSI/S&BS 1 Low ΔT 2 Silica Scaling 3 Strict Discharge

AI-generated project design illustration

📐 Key Calculations

Pinch Point Minimization

ΔT_min = T_brine_out − T_wf_in
Result: 4.2°C
Enabled 12.7% net cycle efficiency while avoiding crystallization

Scaling Index Margin

S&BS = log₁₀([Ca²⁺][HCO₃⁻]² / K_sp)
Result: −0.8
Ensured non-scaling operation at all load points

📊 Results

11.9% net electrical efficiency achieved (vs. 9.3% baseline), zero scaling incidents over 24 months, 100% brine reinjection compliance

💡 Lessons Learned

  • •pH stabilization is more effective than chemical dosing for silica control
  • •Double-pass HX configuration improved fouling resistance by 40%
  • •Real-time scaling index integration reduced manual sampling frequency by 85%

✅ Key Takeaways

  • 1pH stabilization is more effective than chemical dosing for silica control
  • 2Double-pass HX configuration improved fouling resistance by 40%
  • 3Real-time scaling index integration reduced manual sampling frequency by 85%