Technical Description of Reverse Osmosis (RO) Membrane System for Thermal Power Plants

I. System Overview

II. Process Design

1. Pre-treatment System (Key Protection Step)

• Multi-medium Filter: Removes suspended solids and colloids (controls SDI < 5);
• Activated Carbon Filter: Adsorbs residual chlorine and organic matter (protects RO membranes from oxidative damage);
• Scale Inhibitor Dosing System: Suppresses scaling of salts such as CaCO₃ and CaSO₄;
• Security Filter: 5μm precision filtration to intercept particulate matter (protects membrane elements).

2. RO Membrane System Core

• High-pressure Pump: Provides an operating pressure of 4-12 MPa (adjusted according to the salinity of the water source);
• Membrane Element Configuration: Uses spiral-wound polyamide composite membranes (PA), arranged in a two-stage structure with a ratio of 2:1 or 3:1;
• Recovery Rate Control: The recovery rate of the first-stage RO is designed to be 75-85% (40-50% for seawater desalination);
• Produced Water Quality: Desalination rate ≥ 98%, conductivity ≤ 10 μS/cm (first-stage RO), and second-stage RO can reduce it to ≤ 2 μS/cm.

3. Post-treatment System

• Decarbonator: Removes CO₂ and adjusts pH;
• Mixed Bed/EDI: Achieves ultrapure water (≤ 0.1 μS/cm) through deep desalination.

III. Key Equipment Selection Parameters

IV. Key Operational Management Points

Pollution Control

• Regularly monitor transmembrane pressure difference (ΔP); chemical cleaning is required if the pressure difference increases by 15%;
• Microbial pollution prevention: Monthly protective flushing with 1% sodium bisulfite;
• Organic pollution treatment: Cleaning with pH 10-12 NaOH + surfactant.

Energy Efficiency Optimization

• Energy Recovery Device (ERD): Applicable to seawater desalination, saves 30-40% energy;
• Inter-stage Booster Pump Configuration: Balances flow between the two stages and improves system recovery rate.

Handling of Abnormal Conditions

• Sudden increase in produced water conductivity: Check O-ring seal integrity and membrane element damage;
• Decrease in produced water volume: Investigate pre-treatment failure or membrane fouling.

V. Advantages in Thermal Power Plant Applications

• Economic Benefits: Compared to traditional ion exchange, operational costs are reduced by 30-50%, with reduced acid and alkali consumption;
• Environmental Benefits: No acid or alkali wastewater discharge, meeting the clean production requirements of the thermal power industry;
• Adaptability: Capable of treating various water sources, including surface water, groundwater, and reclaimed water;
• Automation: Integrated PLC/DCS control enables unattended operation.

VI. Typical Case Reference

• Water Source: Surface water (TDS 800 mg/L);
• System Configuration: Dual-series first-stage RO (single series production of 120 m³/h) + second-stage RO + EDI;
• Produced Water Specifications: SiO₂ ≤ 10 μg/L, meeting ASTM boiler feedwater standards.

VII. Technological Development Trends

• Membrane Material Innovation: High-flux graphene membranes, anti-biofouling modified membranes;
• Intelligent Operation and Maintenance: AI algorithms predict membrane fouling cycles and optimize cleaning strategies;
• Zero Discharge Integration: Coupling of RO concentrate with evaporation crystallization processes to achieve zero wastewater discharge across the plant.