Case Study of Reverse Osmosis System Design in a Gas Turbine Thermal Power Plant in Jiangsu, China

The reverse osmosis (RO) system in a gas turbine thermal power plant in Changzhou, Jiangsu Province, China, has maintained a desalination rate of 99.0% since its commissioning in December 2018 (at a water temperature of 13°C). As of June 2023, the desalination rate remains above 98.0%. This document provides detailed information on the design of the RO system and some operational data.

For detailed performance parameters of the DA-HSRO-4040 membrane, please refer to: https://www.amembrane.com/Products2/46.html

Process Flow Overview and Functions

1.River Water Intake: Raw river water enters the treatment process.

2.Coagulation and Sedimentation: PAC (polyaluminum chloride) and NaClO (sodium hypochlorite) are added to effectively

remove suspended solids, colloids, and other impurities from the water. The strong oxidizing property of sodium hypochlorite also helps control microbial growth.

3.V-Type Filter: Further filtration removes residual suspended solids and particulates. The residual chlorine concentration is maintained at 0.8-1.0 mg/L to enhance microbial control.

4.Activated Carbon Filtration: The strong adsorption capacity of activated carbon removes residual chlorine and organic compounds, ensuring the purity of the water entering subsequent processes.

Self-Cleaning Filter and Ultrafiltration (UF) System: The self-cleaning filter pre-treats the water to reduce the burden on the UF system. The UF system further removes micro-particles and bacteria, ensuring high-quality product water.

5.Chemical Treatment: After the UF water tank, antiscalants, reducing agents (NaHSO3, sodium bisulfite), and non-oxidizing biocides are added to prevent membrane fouling and ensure no residual chlorine.

Primary Reverse Osmosis (RO): After passing through a well-designed security filter, the water is pressurized by a high-pressure pump and passes through the primary RO membrane to achieve efficient desalination.

6.Subsequent Treatment: The product water from the RO system undergoes further ion exchange treatment through cation and anion exchange beds to enhance water quality and meet subsequent process requirements.

Design of the Primary Reverse Osmosis System

1.RO Membrane Model: DA-HSRO-4040

2.High Treatment Capacity: The system is designed with an output capacity of 3 × 124 t/h to meet large-scale production needs.

Optimized Membrane Configuration: A membrane ratio of 18:9 is used, with a 6-core design to ensure efficient operation and balanced load.

3.High Recovery Rate: The recovery rate reaches 75%, effectively reducing water waste.

Chlorine Residual Control Management

To ensure the long-term stable operation of the RO membrane system, the thermal power plant has implemented several effective measures for chlorine residual control:

1.Sodium hypochlorite is added to the river water in the coagulation and sedimentation tank, maintaining a chlorine residual level of 0.8-1.0 mg/L in the water entering the V-type filter (a higher level of chlorine residual is beneficial for microbial control).

2.When the water from the V-type filter reaches the activated carbon filter, most of the residual chlorine is adsorbed by the activated carbon. The chlorine residual level in the water leaving the activated carbon filter is stable at around 0.01-0.05 mg/L.

3.To prevent any residual chlorine leakage from the activated carbon filter, approximately 1.0-1.5 mg/L of sodium bisulfite is continuously added to the water before it enters the RO system. The chlorine residual level is consistently 0 mg/L after the reducing agent injection point.

4.The UF system is designed with an online automatic Cleaning-In-Place (CIP) system. During normal operation, only water backwashing is performed. A monthly online CIP process is conducted to effectively prevent any chlorine residual leakage into the product water tank.

In summary, through meticulous process design, efficient RO system configuration, and strict chlorine residual control measures, the gas turbine thermal power plant in Changzhou, Jiangsu Province, China, has achieved long-term stable operation with a high desalination rate.