Boiler blowdown refers to the process of removing water from the system to maintain the desired water quality in the boiler. The primary goal of blowdown is to keep the concentration of dissolved solids in check, ensuring your boiler operates safely and efficiently. Depending on the quality of the feedwater, blowdown can vary – it might be as low as 1% with high-quality feedwater or exceed 20% in a system with poor-quality feedwater.

The right blowdown level is crucial: too much will lead to energy loss and excessive chemical treatment costs, while too little can cause dangerous buildups of impurities.

The Role of Blowdown in Boiler Water Treatment

Boiler blowdown is a vital part of maintaining your steam boiler system, as it helps manage the accumulation of suspended solids and control issues like scale formation, corrosion, and wet steam carryover. Proper blowdown can also improve steam quality, increase system reliability, lower maintenance costs, and optimise boiler efficiency.

In industrial steam boilers, blowdown consists of feedwater that has been treated and heated, but rather than being converted into steam, it’s flushed to drain. This process helps control the levels of suspended or dissolved solids in the boiler water. When these contaminants accumulate to dangerous levels, the system can suffer from operational problems.

The necessary blowdown rate varies based on factors like boiler design, operating conditions, and feedwater contaminant levels. This is why it’s important to work with water treatment experts to ensure blowdown is optimised for your specific needs.

Boiler Blowdown Methods: Manual vs. Continuous

There are two primary methods for performing boiler blowdown: manual blowdown and continuous blowdown.

Manual Blowdown
Also known as “bottom blowdown” or “intermittent blowdown,” this method involves manually opening a valve to remove water and accumulated sludge from the boiler. It’s the most common method used for blowdown.

Advantages:

1. • Removes sludge and sediment
   • Helps maintain cleaner boilers, improving efficiency
   • Improves overall boiler operation

Disadvantages:

1. • Wastes treated and preheated water, leading to potential energy loss
   • Occurs intermittently, meaning it doesn’t provide continuous impurity removal

Continuous Blowdown
In continuous blowdown, water is continually removed from the boiler, typically from the surface of the water. This is often controlled with a needle valve or an automated system.

Advantages:

1. • Removes suspended impurities and foam on the water surface
   • Provides ongoing impurity removal, even before settling occurs

Disadvantages:

1. • Requires constant monitoring and adjustment to maintain proper conductivity
   • Continuously removes preheated, treated water, which leads to heat and water loss

Optimising Blowdown for Maximum Boiler Efficiency

For efficient operation, it’s crucial to ensure that blowdown happens only when necessary. Too frequent blowdown can waste energy and reduce boiler efficiency, while insufficient blowdown may lead to poor steam quality and potential damage to the system.

If feedwater quality is low, or the condensate return is inadequate, blowdown rates may need to be significantly higher.

To determine the optimal blowdown rate for your system, you should consider factors such as:

• Boiler design
• Feedwater quality
• Operating conditions
• Control equipment
• Onsite monitoring processes
• Type of water treatment products used

Aquachem have comprehensive range of industrial boiler water treatment solutions. We can help you optimise costs and operational efficiencies, reduce downtime, achieve water and energy savings, maintain steam quality, and increase plant reliability and safety.

Contact us today to speak to one of one of our experts.