Corrosion control in a steam boiler
Company: Citro misr, Cairo Egypt
Description of the problem and its negative consequences
In the chemical industry big amounts of steam are needed to heat up different processes. The client uses several steam boilers, with a total capacity of more then 100m3 per hour. The feed water is treated chemically. The de-mineralized (DM)water gets aggressive and together with the high temperatures inside the boiler corrosion starts at all surface is contact with the water. The client added inhibitors to prevent corrosion, which is the normal procedure if running a steam boiler. The reality has shown, that even by using corrosion inhibitors, there is corrosion anyhow. This corrosion leads on the one hand to iron or rust in the steam, which might cause additional corrosion in the following pipe system and the corrosion leads to a stock removal on the surfaces, which is responsible for a shorter lifetime of the boilers. This can be easy checked by the blow down water of the boiler. In a steam boiler having corrosion problems the blow down water is not clear, but has a brown color, caused by the iron or Rust Fe2O3.
There was one Merus ring installed at the feeding pipe of the boiler. Due to safety reasons there was first no change in the adding of inhibitors against corrosion.
In which way the customer checked the results of the trial
The iron content in the steam and the Blow down pipe was regularly checked. The steam is essential for the production, without steam they have to stop working. Therefore no changes at the existing setup of adding chemicals where made. During the weeks, the iron in the steam has gotten less and less, and finally stabilized on a very low level. From outside it could be seen the corrosion was less than before.
To avoid any risk, the adding of the inhibitors was stopped not before 6 weeks ahead the regular production break where service is made on the boiler. This was done, to be able to assure visually the function of Merus, by checking the appearance of the inner surfaces of the boiler. It was seen, that most of the surface was now black, coated with saturated iron, only a few red spots have remained.
After seeing this result the client has decided to stop adding corrosion inhibitors. To ensure the results and for safety reasons, the steam is regularly checked for iron.
Today the client saves not only the chemicals, but as well the costs for service of the dosing systems.
Concerning the lifetime of the boiler no final data are available. But due to there is almost no iron found anymore in the steam, it is to assume that the lifetime has increased.
A lot of customers are reusing the condensate from the steam consumers. This condensate is coming back and reused to produced new steam. Merus is able to solve these problems in the condensate as well. See to this topic the case study corrosion in a condensate system.