Module 3. 6-9 Flashcards
Process done to control purity and pH of water by removing undesirable ions and exchanging them with acceptable ions.
Demineralization
Exchange of ion between a solid substance (called resin) and an aqueous solution (coolant or makeup water)
Ion exchange
Resin beads are insoluble in ___, ____ and ____
water, acids, bases
Two types of ion exchange resin:
1. Resins exchange in positive ions.
2. Resins exchange in negative ions.
Cation Resin
Anion Resin
Extremely large molecules that are formed by the combination of many molecules of one or two compounds in a repeating structure that produces long chains
Polymers
A device which exchanged undesirable ions with desirable ones.
Ion exchanger
An ion exchanger in which H+ (for cation resins) and OH- (for anion resins) are present on the sites of resin beads
Demineralizer
Two classification of Ion Exchanger:
1. Cation and anion resins are separated
2. Mixture of cation and anion resin
- Single Bed
- Mixed Bed
In GMEC, the volume ratio is _____ cation resin to ____ anion resin
one-part, two-part
The amount of impurity that a given amount of resin is capable of removing; it has units of moles/ml, equivs/ml or moles/gm
Exchange capacity
The strength of the ionic bond between the resin and an ion varies with the particular ion.
Affinity
3 Resin Bed Malfunctions:
- Overheating
- Breakthrough and exhaustion
- Channeling
The anion resins begins to decompose slowly at about 140F and the decomposition become rapid above 180F
The cation resin is stable up to about 250F
Ion exchanger is set to 120F Limit
Overheating
Impurity ions begin to appear in the solution after it has passed through the resin.
Breakthrough
When the concentration of impurities is the same before and after the solution passes through the resin
Exhaustion
Indicators of depleted exchange capability of resins
Breakthrough and exhaustion
It is a condition in which the resin allows a direct flow of water through the ion exchanger.
Channeling
It can mostly results from improper filling of the ion exchanger with resin
Channeling
If insufficient water is mixed with the resin when it is added ,the resin column may contain _____ or ______
pockets, voids
Classification of the cation resins at the bottom an anion resins on top of the resin column
Backwashing
Exchanging impurity in the exchange sites of the resin with H+ and OH- from acid and caustic
Regeneration
Cutting acid and caustic dosing, allowing only dilution water to flow.
Slow rinse
Draining of excess fluid
Vent and Partial Drain
Done to make sure that the resins are mixed again
Air mix
The resin is rinsed by running water through the vessel from top to bottom and out of the drain, until a low conductivity reading indicates that the ion exchanger is ready to return to service
Final Rinse
The degree to which an object conducts electricity, it is the reciprocal of resistance
Conductance
The measure of the ease at which an electric charge can passes through material, reciprocal of resistivity
Conductivity
High purity water that has been distilled and/or de-ionized so it will have a specific resistance of ______ ohms
500,000
Presence of oxygen can promote _____ at area on the metal surface
pitting
Oxygen in the solution inside the ____ will be depleted initially by the corrosion reaction:
pitting, 2Fe + O2 = 2FeO
The three condition for Chloride SCC to occur:
Presence of chloride ions,
dissolved oxygen,
metal is under tensite stress
How does Carbon Dioxide end up in boiler water?
- Dissolved carbon dioxide
- Presence of bicarbonates and carbonates in water
Dissolve oxygen together with carbon dioxide is how many percent more corrosive than if the two were acting alone.
40%
Solution to manage carbon dioxide and oxygen
- Manage pH level at an alkalinic level pH (9 and 11)
Deaeration Steps:
1. Reduce surface tension
2. Oxygen and carbon dioxide lose solubility
3. Mechanical agitation and scrubbing to liberate the gases
4. Oxygen and carbon dioxide in gaseous form
- Spraying or filming
- Heating
- Scrubbing
- Releasing
Solution to manage carbon dioxide and oxygen
- Chemical Addition
- Trisodium Phosphate (Na3PO4)
- Disodium Phosphate (Na2HPO4)
- Ammonia (NH3)
Solution to manage carbon dioxide and oxygen
- Chemical: Oxygen and Carbon Dioxide Scavenger
- Hydrogen gas
- Hydrazine
Solution to manage carbon dioxide and oxygen
- Mechanical: DE aeration
- used to strip feedwater from the non condensable gases oxygen and carbon dioxide to prevent damage of the components downstream.
