Heat Recovery From Warm Wastewater

News, Solutions In Manufacturing - 588 - GOMEC Vietnam

Contents/ Mục Lục

1. The Reality of Hot Wastewater Discharge in Industrial Sectors
2. Challenges in Heat Recovery from Industrial Wastewater
3. Heat Recovery Solution Using WideGap Technology
4. Practical Benefits of Wastewater Heat Recovery
5. Case Study: Wastewater Heat Recovery System at BAJ Textile Plant, Hung Yen
Reference:

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1. The Reality of Hot Wastewater Discharge in Industrial Sectors

In many manufacturing industries such as brewing, food processing, dairy production, chemicals, and paper processing, the practice of directly discharging hot wastewater into common wastewater drainage systems is widespread.

The textile dyeing industry, in particular, generates a large volume of hot wastewater. This wastewater contains a significant amount of thermal energy, and if recovered, it can reduce operational costs, conserve fuel, and lower emissions, delivering substantial economic and environmental benefits.

2. Challenges in Heat Recovery from Industrial Wastewater

Finding a suitable technology to recover heat from wastewater is complex. Industrial wastewater often contains fibers, chemicals, and various impurities, making conventional heat exchangers prone to clogging and fouling.

Shell-and-Tube Heat Exchangers: Due to their structural design, counterflow heat exchange is not achieved, resulting in low heat transfer efficiency. Approach temperature typically ranges from 15-20°C. Lower risk of clogging from fibers and impurities. Heavy weight and large installation space required, making maintenance difficult.

Standard Plate Heat Exchangers (PHE): High heat transfer efficiency, with approach temperatures as low as 1°C. Narrow channel design makes them unsuitable for wastewater with fibers and impurities, leading to frequent clogging.

Rotating Heat Exchangers (Rhex): Open-type heat exchanger, using a motor-driven rotating rotor for heat transfer. Easy maintenance and cleaning. Low heat transfer efficiency, with approach temperatures of ~15°C. High energy consumption due to motor operation. Significant heat loss through convection due to open design. Limited flow rate range (6-36 m³/h). Large footprint and only suitable for outdoor installation with no redundancy options.

These limitations necessitate an advanced, specialized solution to address the unique challenges of industrial wastewater, particularly in textile dyeing plants, where wastewater contains fibers, chemicals, and contaminants.

3. Heat Recovery Solution Using WideGap Technology

As a global leader in heat exchange technology, Alfa Laval provides an optimal solution through its WideGap heat exchanger series, specifically designed for handling wastewater with fibers and impurities.

Key Features of WideGap Technology:

WideGap Heat Transfer Channels: Rectangular channel design with a width of up to 11 mm, with no contact points between plates, enabling efficient handling of wastewater with fibers and particulates without requiring fine filtration (<5 mm).
Optimized Heat Transfer Channel Design: Fibrous wastewater flows through the wide channel (A), while clean water flows through the narrow channel (B), creating maximum turbulence, enhancing heat exchange efficiency.

Backflushing for Easy Cleaning: Integrated backflushing feature with appropriately sized connections allows for regular cleaning, which can be performed automatically or manually for quick and efficient maintenance.

Pre-Filter Protection: The inlet of the WideGap heat exchanger is equipped with a 5 mm mesh filter, allowing only fibers and particulates <5 mm to pass through, preventing large contaminants from entering.

Compact Size:Then 80% lighter than shell-and-tube heat exchangers. Requires only 20% of the installation space compared to traditional shell-and-tube models.

Thanks to WideGap technology, Alfa Laval heat exchangers can operate continuously for extended periods without requiring shutdowns for cleaning or maintenance, ensuring high reliability and efficiency.

4. Practical Benefits of Wastewater Heat Recovery

Recovering heat from wastewater delivers multiple benefits:

✔ Reduced Fuel Costs: Recovered heat reduces fuel consumption for steam boilers, lowering production costs.

✔ Shorter Production Cycles: Pre-heated water from heat recovery minimizes additional heating time, reducing the overall processing cycle duration.

✔ Lower Environmental Impact: Reduced fuel consumption leads to lower greenhouse gas emissions. Lower wastewater discharge temperature, minimizing thermal pollution to the environment.

✔ Versatile Applications: Recovered heat can be used for:

Supplying hot water for production processes
Pre-heating boiler feedwater
Providing hot water for industrial cleaning
Delivering hot water for office facilities or other needs

This heat recovery solution not only optimizes energy costs but also enhances production efficiency, meeting increasingly stringent environmental protection requirements.

5. Case Study: Wastewater Heat Recovery System at BAJ Textile Plant, Hung Yen

The BAJ plant in Hung Yen specializes in textile dyeing for multinational fashion brands.

Existing System: The plant operates a biomass-fired steam boiler with a capacity of 4,000 kg steam/hour. Steam at 6 bar pressure is supplied to production workshops. Dyeing machines heat process water to 95°C using steam. After each dyeing cycle, hot wastewater is discharged into the plant’s drainage system.

Solution: Implementing a wastewater heat recovery system using Alfa Laval’s WideGap heat exchanger technology.

Heat Recovery & ROI Calculation
Total wastewater discharged from dyeing workshop	595 m3/day
Wastewater flow rate recovered	7,1 l/s
Heat recovered	1184 kW
Investment payback period	9 months
Fuel savings for the boiler	1653 tons of biomass/year
Reduced boiler steam demand	2,0 tons of steam/hour
Operational cost savings	2,7 billion VND/year
Reduced greenhouse gas emissions	4132 tons/year
Carbon credit benefits	347 million VND/year

Reference:

Contact Information Gomec Vietnam Mechanical and Electrical Joint Stock Company – Authorized partner of Dunham-Bush and Alfa Laval in Vietnam, providing central Air conditioning systems, Heat exchanger equipment, and Energy-saving solutions. For consultation on solutions and equipment, please contact us for direct support.