Chapter 17 And 18 Book 3 water treatment. Flashcards
Anions versus cations
An ion are the negative ions in a chemical mixture. Cations are the positive ions of a chemical mixture. Sodium is a cation and chlorine is an anion.
Deaerator
Mainly in high pressure plants the feed water is pumped to this unit and mixed with steam to release any dissolved oxygen which is then vented to atmosphere
Internal versus external feed, water treatment
Usually used in conjunction with each other. There are times when the internal method is only used, but never only external external treatment is achieved through filtration and softening of the water where internal is chemically treated after it enters the boiler.
Four sources of impurities
Dissolved solids, end, dissolved gases – suspended solids – organics are used for impurities can be counteracted by mechanical thermal and chemical means
Mechanical involves strainers filters and chemicals can be used as well
Thermal pertains, mostly to dissolved gas impurities, which are driven off as the water temp rises. Chemicals can also be used to counter at the dissolved gases.
Chemical – this treatment method pertains mostly to dissolved solids, but to others as well, and both chemical concepts are used in the reaction and the exchange types
Filter in boiler water
This usually involves strainers initially followed by various types of filters when filter in large volumes, the filter consist of a sand bed that the water flows through by gravity an alternate method would employ a settling basin for less volumes. Pressure filters are used, and if the volume is even less cartridge, type filters are used.
Coagulants
These are chemicals that cause define particles to gather together into a large mass, which will settle out more readily in filters or settling tanks
Settling tanks and filters working together
When used in conjunction with acetylene tank, the water is moved into acetylene tank. Impurities are allowed to settle out in the settling tank. The water is then passed through the filter to remove any remaining impurities.
Sodium zeolite water softener
Things to remember are there two radicals that are bicarbonate and sulfate and elemental impurities that are calcium and magnesium. The radicals are slightly attracted to the element impurities, but are strongly attracted to sodium the zeolite is charged with sodium so when the radical an element, all impurity flows through the zeal light, the elemental impurity is strongly attracted to zeal light, and the radical is strongly attracted to the sodium. The sodium causes the radical to be very soluble so that it does not precipitate out of the solution when the water is heated, it remains in the solution, once all the sodium has left, the zeal light, the regeneration needs to occur. This brings in sodium chloride into the region tank chlorine has the strongest attraction to element impurities saw the zeal light can be charged with sodium again, and the chlorine will attach to the magnesium or calcium and be washed out the drain biggest thing to remember is that the radical can be either sulfite or bicarbonate and elemental. Impurities can be calcium or magnesium, and therefore possible combinations of those elemental impurity has the weakest attraction to radicals and the strongest to chlorine will the sodium has the weakest attraction to chlorine and the strongest two radicals
Two types of chemical pump
Plunger pump and the electric impulse pump plunger pump are useful at all pressures but especially when injecting chemical directly into a boiler this is due to it being a positive displacement pump the electric impulse pump has to discharge chemical into the D aerator her into low pressure, steam and condensate pipe in
Suspended solids
These are in the form of sand and silt and cause sludge or mud to settle in low areas, which interfere with proper heat, transfer in circulation
Dissolved gases
Remember, cold water has the ability to hold more substance in solution than hot water the gases we are concerned with her oxygen and carbon dioxide, which will cause corrosion in the boiler once metal loss occurs it cannot be replaced and will shorten the life of the boiler considerably
Dissolved solids
These are minerals in solution, and when the water is heated, these impurities precipitate out of the solution and become a suspended solid, therefore scale which will interfere with heat transfer and water circulation two main types of dissolved solids are those which cause temporary hardness in those which cause permanent hardness
Organics
This is plant or animal origin such as decayed leaves or oils if not removed, they will cause forming in the boiler a Forman occurs. There will be water in the steam due to carry over.
The main methods of testing
Titration, comparison, meter
Titration involves adding a measured amount of a specific chemical to a sample consisting of a specific amount of water, so the color change is produced
Comparison
Basically, you add chemicals to water to produce a color change, which is compared to a color standard chart of known concentrations of a substance in the water
