Water treatment chemicals affect pH

[JoeChem]

I am unfamilair with steam generation equipment and water treatment systems/chemicals. I am dealing with a steam distillation process that uses live steam to distill peppermint and spearmint oil from the respective green plants.

My question is can water treatment chemicals affect the pH of steam/condensate? I ask because we have reason to believe the oil has been in contact with acidic material (i.e., unwanted reactions resulting in out of spec product).

Any help and/or experience will be greatly appreciated.

JoeChem

 

[whoislee]

Water treatment chemicals will affect the pH depending on the nature (type) of chemicals used.

Normally for steam plants, anti-scalant, pH adjusters are used in pretreatment of the water but they are normally removed prior to steam generation.

Please advise your water treatment configuration.

There are 2 sides of a coin
One is to give, one is to take
Give until it hurts with a smile

 

[abcmex]

Most of the chemical treatments for steam side are designed to avoid exactly an acidic enviroment inside the pipes and equipments.

As Whoislee mentioned the chemical treatment can be divided in two sections first for the boiler (anti scalant, oxygen scavengers ect.) but they usually stay in the boiler.

The second section are designed to leave the boiler and goes with the steam through the system. The goal is mainly to avoid corrosion on the steam/condensate by neutralizing CO2 and Oxygen, a typical compound is NH3, others are amines.

If you do not have an adequate chemical program you could have problems. Check pH (around 9) and iron content (around 1 ppm) in the condensate near to your application. This will tell you more.

 

[pablo02]

boiler water pH is normally (I'm used to 9.6 to 10.2 range) to protect the steel -- makeup is normally around 6.8 to 7.2 which is not good for the boiler, so chemicals are added to raise the pH, usually PO4 (phosphates) -- other chemicals are added to address other issues as mentioned above...

These chemicals will concentrate at the steam water interface and are removed by blowdown (as mentioned above, they usually don't carryover with the steam except for some of the oxygen scavenging chemicals -- see below)-- this is why the chemistry is usually monitored continuously and fed accordingly (on power boilers) -- smaller boilers such as heating boilers may batch treated...

a couple of areas to watch -- if you have gotten oil in the boiler system, it will tend to foam at the steam water interface and will allow chemicals to carryover, not good for those chemicals that raise the pH such as phosphates... any oil will need to be cleaned out...

some of the chemicals such as the oxygen scavengers, etc. are made to breakdown in the SH sections and will produce ammonia (NH3) which will affect the pH of the condensate -- too much ammonia will also attack any copper or brass heat exhanger materials...

in all cases, though, the normal chemicals used for boiler chemistry tend to drive the pH up and not acidic -- if you have an acidic problem and you are treating your boiler, I'd look for a water contamination (check silica and cation conductivity) -- a small condenser leak (such as circulating water into the condensate -- don't know if this applies to your setup) will drive the pH down rapidly, consuming phosphates, etc... (bad news...) -- also, you should check your make-up stream for any problems...

 

[procedk]

Pablo02

You mention to check amount of silica. The amount of silica doesn't directly affect pH, but does it react with cycloheaxmine, Phosphat PO4 or hydrazine in deareator. It will obviously end up in BBD line, if no reactions-

 

[pablo02]

Silica would be an indication of contamination which could reduce the phosphates and run the pH down in a short period of time... if one is having chemistry problems in a boiler, there a number of issues to consider... I did not intend to imply that silica itself would cause problems with pH...