Cooling water towers are employed to extract heat from water generated from an industrial process. More information about the towers, cooling circuit parameters, and water quality examples are available in the attachments.
Treatment of a cooling system has two basic objectives: to protect and extend the life of the cooling system and to insure good heat transfer and removal. Any fouling of the heat exchanger surface by scale, debris, or growth of microorganisms decreases the heat transfer efficiency. Corrosion destroys heat exchanger surfaces and causes leaks that result in mixing of the cooling water and the process fluid.
Consequently there are three components to a cooling water treatment program:
- Microorganism control,
- Scale and deposit control, and
- Corrosion control.
Microorganism fouling in cooling systems is the result of abundant growth of microorganisms on surfaces. Once-through and open or closed recirculating water systems may support microorganism growth. The outcome of uncontrolled microbial growth on surfaces is "slime" formation. Slimes typically are aggregates of biological and non-biological materials. Slimes can form throughout once-through and recirculating systems and can be manifested by decreased heat transfer efficiency or reduced water flow. Microbial activity under deposits or within slimes can accelerate corrosion rates and even perforate heat exchanger surfaces.
Therefore, microbiological control is arguably the most important portion of a cooling tower treatment program. Microbial growth on wetted surfaces leads to the formation of biofilms. Failure of those control program causes fouling, which can adversely affect equipment performance, promote the corrosion of metal, and accelerate wood deterioration. The effect on the heat exchangers is negatively impacts performance, resulting in economic loss for the plant.
These problems can be controlled through the application of appropriate cooling water biological monitoring. Yet, there are several critical issues related to conventional disinfection processes:
- High costs of disinfection materials and substances (especially non-oxidizing)
- Blow down discharge
- By being conservative with the dosification of disinfection substances (to be compliant at the discharge), the risk of growth of microorganisms increases
- Low effectiveness in some range of pH
- Storage complications, degradation of products.
Enel is seeking a high performance technology for the disinfection of cooling water in evaporative towers without the use of chemicals, thus overcoming the conventional processes. The solution must be sustainable both environmentally and economically, with a favorable return on investment (ROI) within one to two years of implementation.
Submissions must have the following Solution Requirements:
- Compliance with regulations and in particular discharge limits (e.g. D.Lgs. 152/06 for Italy) for the blow down
- The system should assure no growth of microorganisms in the circuit, to be maintained below the limit of 1000 CFU /liter
- High proven efficiency of disinfection towards microfouling and prevention of macrofouling
- Easy installation as retrofit solution
- No reactive chemical processes used
- Safe to use while the cooling tower is operational
- Supports Enel’s commitment on SDGs (Sustainable Development Goals) with specific emphasis on 6 and 12
- The proposed technology should offer Enel “freedom to practice” or be available for potential licensing. There should be no third party patent art preventing the use of specific equipment and materials for their commercial application.
In addition, the following qualities are highly desired but not required:
- Remote operation
- Reduced footprint
- Low maintenance costs
- Reasonable investment costs
- Commercial solution (or minimally at a pilot/demonstration stage)
The submitted proposal should include the following:
- Detailed technical description of an approach that can meet the above Solution Requirements
- Rationale for the proposed technology, including monitoring and control methodology, while addressing any known limitations
- A bibliography of relevant literature (e.g. journal articles, patents, trade materials) that support the proposed solution
- If available, schematics for installation and rough estimations of costs (e.g. investment, operational, maintenance) and power consumption
The proposal should not include any personal identifying information (name, username, company, address, phone, email, personal website, resume, etc.) or any information the Solvers may consider as their Intellectual Property they do not want to share.