contaminated boiler feedwater 1

[pbrod]

Dear all,

recently our boiler feedwater was contaminated with a large quantity of bio diesel and vegetable oil.
The pH dropped from 9,5 to 4,5 and the purge water was a milk like substance. We do not have a good idea on the quantity of bio diesel and vegetable oil that came in the feedwater.
We now purge the system as much as possible and add good quality make up water (aprox 50m³/h).
We also add a larger quantity of water treatment products for pH correction.
Now we see some foam formation on the water and the purge water has also a black color (the magnetite that comes off).

Does anyone has experience with such kind of incident?
can we add special products increase the speed of removal of vegetable oil? all tips are welcome!!

 

[davefitz]

Well, one could inject vinegar and spice and market the purge as a new style salad dressing.

We have had a case where the fuel gas pre-heater tube sheet had leaked ( at the rolled tubes) natural gas into the heater's drain cooler, which drained directly to the ACC condensate holding tank and onto the dearator. We had a low pH excursion around the same time, and hydrogen damage to the HRSG. After replacing the fuel gas preheater and modifying startup ops to avoid thermal shocks to the tubesheet, we are also planning to add a methane detector to the ACC vacuum pump vent.

There are available detecton devices to allow fast detection of inleakage of hydrocarbons, liquod or gasous forms.

 

[Champion09]

I have an experience where lubricating oil from turbine bearing drain header overflowed from its venting System into Condenser causing oil carryover into Boiler thru recycling Feed water.

The corrective action taken was to take the Boiler off line. Force cool the boiler, purge the water from Boiler and rinse the condenser with detergents. The method worked to decontaminate the System.

 

[pbrod]

Thanks for the info!
We kept the different steam boilers online because we could not loose production. The problem is that through the steam boiler purge line a very sticky grease/glue like material is purged. It is also black from the magnetite that came of the tubes.
we will contact the water treatment guys to look for solvent cleaning.

thanks again,

 

[HEC]

Fats, oils and a high pH is a typical saponification reaction. I have had traces of milk in a high pressure boiler that generated similar results. The black may simply be from burnt protiens. Nothing nasty was precipitated out and the foaming settled down with minor change to treatment ratios.

Mark Hutton

 

[jim1953]

Wouldn't oil type contaminants coat the tubes?

 

[macmet]

We had a customer a long time ago who had their boiler feedwater contaminated with a dairy product. We were told that it led to a significant number of cracks and they have since had problems.

Whether the cracks were really caused by the product or the fact that the plant was being run so carelessly that this cross contamination could even happen and the likelihood of other poor operation patterns is another matter....But I would shut the boiler down and get the water treatment group in asap.