Co-Generation: Exploring Beyond Power Production – Salination and Disillination

In this article, we will explore the applications of co-generation beyond power and heat production, focusing on salination and disillination processes. These technologies are crucial in coastal regions where freshwater demand continues to grow. Here's what you need to know about these processes.

Why Co-Generation for Salination?

Co-generation plants for electricity production and salination are often used in coastal regions, as they are more efficient than standalone plants. They help address the issue of freshwater scarcity by using seawater desalination.

Salination Processes

There are two common processes associated with salination: membrane separation and thermal evaporation. Let's start with membrane separation.

Membrane Separation

This process uses a semi-permeable membrane to selectively permit or restrict the flow of certain ions. The fundamental driving forces for this process are reverse osmosis, nanofiltration, and electrodiolysis.

Reverse Osmosis

Reverse osmosis is based on overcoming the osmotic pressure by applying an external hydraulic force greater than the osmotic flow. The membrane for a reverse osmosis system filters out salt and solutes while water passes through.

Nanofiltration

Nanofiltration is another membrane process similar to reverse osmosis that uses pressure for water flow. This process has a high percentage efficiency in removing divalent ions.

Thermal Evaporation

This process works by evaporating water from a saline solution, condensing the steam produced to create distilled water. There are three common thermal technologies for this process: multi-stage flash, multiple effect distillation, and vapor compression.

Multi-Stage Flash Distillation

This is the most common installation in the world. Water is heated in a series of stages between 15 to 25, where it will be progressively subject to lower temperature and pressure. Within each stage, a portion of the water is flashed, causing some of the water to boil and become vapors.

Multiple Effect Distillation

This type uses multiple containers in series for multi-stage distillation with each having lower pressure. It's more efficient than the multi-stage flash distillation because the vapor produced is condensed in a way that it heats the remaining saline solution in the next stage.

Vapor Compression

This method compresses water vapor in the distillation process so that it will be at a higher temperature and pressure. This compressed vapor is then returned to evaporate so that it can be used as a heat source.

Water Quality Concerns

After desalination, the water must be further conditioned and treated to achieve acceptable quality for use in drinking or irrigation purposes. Here are some concerns:

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  Health: The presence of unregulated toxic compounds, such as boron, can affect health. High levels of chloride in water can also cause issues for agricultural crops and industrial use.
  
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  Agriculture Use: High levels of boron and sodium in water can affect agricultural crops' growth and produce tattered leaves.
  
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  Industrial Use: Chloride concentration in water is a concern due to its corrosive properties.
  
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  Physical Properties: Depending on the process of salination, there may be specific odors and tastes in the water, which may not have any health concerns but could lead to complaints if used as drinking water.