Cooling Tower Water Chemistry Parameters 1

[TBDaniel]

What are the chemical limits being used for water chemistry monitoring for an induced draft, counter cooling tower for the following parameters:

pH
Conductivity
Total hardness
Calcium
Total Alkalinity
Chloride
Silica
Iron
Turbidity

What are considered the most important parameters to monitor?

 

[quark]

pH - 7.5 to 8.5 and if you chlorinate the system then upto 9

Conductivity - I would give TDS, rather, as 300 to 500 PPM depending on no. of COC you want to maintain. The figures I gave are maximum limits.

Total Hardness - Not more than 100 ppm.

Chlorides - Depends upon your TDS

Silica - (Suspended)less than 5 ppm. Dissolved silica should not matter in cooling water temperature range.

Iron - well, as low as possible

Turbidity - Mostly depends on suspended silica. However less than 10 NTU should be ok.

These are the values we follow, let's see what others say.

Regards,


Believe it or not : A Neutrino is so mass less(and electrically neutral) that, a conservative estimate states, it can pass through a 50 light year thick lead block.

 

[abcmex]

An specific answer is not possible with without some additional informations. The cooling water specification may depend on:

a)materials employed in the system. If you have are using cooling water with high resistant materials to reach high concentration cycles you will have a different specification as when you have austenitic steels (like AISI 304).

b)chemical treatment used. according to the treatment your operation ranges will be modified for example if you use dispersants the limits for some undesired particles like calcium can be higher.

c)make up water quality. If you know your water at the inlet, some characteristics (like temperatures ect.) and the materials you can establish you chemical conditioning program and this will also establish the cooling water parameters.

I recommend a conditioning program unless your water and enviroment as close to heaven. No, I do not work for a company that sell them ;-)

 

[bimr]

You are probably looking at numbers like these:

pH 8-8.5
Calcium Hardness 800-1000 mg/l
Total Alkalinity 200 mg/l
Chloride 1000 mg/l
Silica 150 mg/l
TDS 8,000 mg/l

These are typical parameters for large cooling systems with common construction materials. You may be able to exceed some of these parameters by using various condition chemicals and metallurgy. Also, your results may vary depending on relationships between the parameters in your actual water analysis.

 

[Longhouse]

It's very difficult, if not impossible, to give definitve figures for what you request. However, I used to work in the industrial water treatment industry supplying products and services for the control of corrosion, deposition & biofouling but it was some time ago! My advice may be a little out of date but here goes....

As general rule, problems of one sort or another will be encountered if no conditioning controls are employed.

1. Start as already advised by examining raw water quality and system operational characteristics (temperature range, max temperatures, local environment, materials of construction, any local discharge limits, current problems, etc)

2. A useful tool for determining the likely problems that you may encounter can be the Langelier Saturation Index or the Ryznar Index. This will indicate the likely scaling / corrosion potential of the system and allow a conditioning treatment progrqamme to be tailored

3. From the above, you can also then determine the max COC (Cycles of Concentration) allowable - remember, the prime function of a cooling system is generally not to cool water but to save water by recycling! If water were free we'd all be using "once through" systems.

4. The greater the COC the lower the water & chemical bill - treatment chemicals (except biocides unless applied continuously, viz possibly chlorine / bromine) concentrate in the process stream as do other dissolved / suspended materials.

5. Best to contact a number of suppliers regarding an inhibitor programme

6. TYPICAL (emphasised) ranges for the determinands you request:
pH - usually between 6.5 to 8.5. Lower potentially increases corrosion risk but reduces scaling, higher favours scaling. Higher ph reduces efficacy of chlorine (hypochlorous acid is the effective biocidal component. A high pH may also reduce the protection offered by certain forms of treatment (e.g. zinc products)

Cond - (or Total Dissolved Solids). Higher can increase risk of corrosion but ususlly just considered as indicator of system concentration. Figures of around 2000 to 2500 uS are probably a typical max.

T Hardness - Calcium generally more of a problem due to more ready ppt'n of calcium carbonate. Actual value of Ca hard used in Langelier calc. Actual permissable values would vary considerable depending upon nature of the system and other ions present (e.g. a CaCl2 brine system would be very high indeed due to the high solubility, CaSO4 predominant would lead to typical figures of around 2000 max applied, CaCO3 a lot less dependant mainly on system temp)

T ALk - indicator of temp hardness. Again no actual max usual, but used in Langelier calcs

Cl2 - very useful indicator of cycles of conc as usually unaffected by environment of the system. Only really an issue with suseptable materials present (e.g. stressed stainless)when levels of 200 max might be applicable.

Si - not normally an issue unless particulate thaen becomes part of sus solids / turbidity consideration w.r.t errosion & deposition potential. Silca based corrosion inhibitors can be used.

Fe - undesirable due to indicator of corrosion within ferrous systems and considered as an essential nutrient for some biofoulants. Consider that a potable water system would operate at 50 ppb target with MAC 200 ppb. probably means that a system value of 1 to 2 ppm would be OK

Trust this helps

 

[luissabate]

There is not only one answer to your question.
The limits are chemically related:

Total Hardness & Total Alkalinity
Mg & SiO2 (soluble)
pH & Alkalinity
Ca & SO4=
Cl- + SO4= & EC (or TDS)

From the analysis of feed water you can calculate teorical COC. Then recalculate the range for the other parameters.
(But there is always a choice, the design of the treatment program).

e.g.:
Repo
TH= 120
TA= 300
SiO2= 70

Tower
COC <1.9 (90%x150/70)
pH < 9.2
TH = 90%xCOCx120 - 110%xCOCx120
TA= K/TH