- November 22, 2017
- Posted by: akvante258
- Category: blog
The operation and the chemical water treatment of a boiler or steam generator are well regulated by national and international standards as well as guidelines by the equipment manufacturers.
It is therefore usually clear for the customer that he/she has to apply chemical treatment.
Our task, as water treatment specialists, is to clarify what are the consequences if the correct treatment is not selected, applied and monitored properly and to explain what is the value of treating the water in a steam generation system.
We should keep in mind that when we refer to the steam generation system, the system includes:
- the deaerator and/or feedwater tank
- the boiler
- the steam piping and steam traps,
- the process equipment (i.e. heat exchangers and other equipment related to the production process)
- the condensate piping
What are the problems we try to prevent? Below are 3 categories of usual problems.
Reduced heat transfer efficiency, due to:
- Scaling or corrosion products (iron oxides) on boiler tubes
- Carryover of water droplets in the produced steam (reducing the heat capacity of the produced steam)
- Low temperature of boiler feedwater (if condensate is lost and not returned to be used as boiler feedwater, due to condensate water quality issues)
Reduced equipment life and high maintenance costs, due to:
- Scale (tube rupture due to overheating, caused by scaling)
- Corrosion (oxygen pitting corrosion in the boiler tubes, condensate system corrosion due to low pH)
Loss of production and frequent shutdowns for repairs and cleaning, due to:
- Scale (boiler tube overheating leading to deformation and rupture)
- Corrosion (boiler tube rupture due to oxygen pitting corrosion, condensate line leakages due to carbonic acid corrosion)
The main causes of the above problems are:
- Corrosion in the boiler, due to oxygen attack
- Corrosion in the condensate system, due to carbonic acid attack
- Scaling due to hardness (calcium and magnesium) entering the boiler and creating carbonate or other deposits
An effective treatment program will have to address all above issues and should include:
- An oxygen scavenger for scavenging any oxygen remaining in the feedwater after the deaeration
- A scale inhibitor for preventing the residual hardness to react with the alkalinity ions or other scale forming ions volatile neutralizer to travel with the steam and neutralize the carbonic acid formed in the steam condensate
Points to remember
- Check with the customer about the standard he/she is following for the operation of the boiler (international standards such as ASME or the boiler manufacturer guidelines). State the applicable standard in your proposal and/or your service reports, in order to prevent any misunderstandings about the source of the guidelines in water quality and/or chemical residuals
- Review the standard and confirm that your treatment approach and your recommendations for water quality and active chemical residuals conform with the standard
- Explain the consequences of corrosion and scaling (which can lead to loss of heat transfer efficiency, high maintenance costs and unexpected shutdowns) if the recommendations are not followed (chemical dosages and water chemistry control limits)
- Remind the customer of the risks in your service reports when you identify deviations in the water quality limits and/or the chemical residuals.