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Circulating cooling water

Save water resources

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Circulating cooling water refers to heat exchange through heat exchanger or direct contact Heat exchange method is used to exchange medium heat and recycle after cooling water in cooling tower to save water resources. Normally, circulating water Is neutral and Weak alkalinity The pH value should be controlled between 7-9.5; When the circulating cooling water in direct contact with the medium is acidic or alkaline (pH value is greater than 10.0), it is generally less.

Chinese name: Circulating cooling water
Characteristics: Neutral and weakly alkaline

P H: 7-9.5
Advantages: Save water resources

catalog

one origin
two Water quality standard table
three technical parameter
four processing method
five Technical background and significance

origin

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loop Water cooling It comes into contact with air through water Evaporative heat dissipation , contact heat dissipation and Radiant heat dissipation The result of the three processes.

1、 Evaporative heat dissipation : Water forms large and small water drops or extremely thin water film in the cooling equipment to expand its contact with air contact area And extension contact time Strengthen the evaporation of water, so that water vapor can take away the heat required for gasification from the water to cool the water;

2. Contact heat dissipation: water is in contact with the air at a lower temperature, and the heat in the hot water is transferred to the air due to the temperature difference, so the water temperature is reduced;

3. Radiative heat dissipation: not required Heat transfer medium The role of electromagnetic wave In the form of heat energy.

Water quality standard table

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project	Company	Requirements and service conditions	Allowable value
Suspended solids	Mg/L	Determined according to production process requirements	<20
Suspended solids	Mg/L	The heat exchange equipment is plate type, fin tube type and spiral plate type	<10
PH value	-	Determined according to the pharmaceutical formula	7-9.2
methyl orange alkalinity	Mg/L	Determined according to reagent formula and working conditions	<500
calcium ion	Mg/L	Determined according to reagent formula and working conditions	30-200
Ferrous ion	Mg/L	-	<0.5
Chloride ion	Mg/L	Carbon steel heat exchange equipment	<1000
Chloride ion	Mg/L	Stainless steel heat exchange equipment	<300
Sulfate ion	Mg/L	The requirements for concrete materials in the system shall be in accordance with the current Code for Investigation of Geotechnical Engineering GB50021 94	-
Sulfate ion	Mg/L	Sum of sulfate ion and chloride ion	<1500
Silicic acid	Mg/L	-	<175
Silicic acid	Mg/L	The product of magnesium ion and silicon dioxide	<15000
Free chlorine	Mg/L	At the return main	0.5-1.0
Petroleum	Mg/L	-	<5
Petroleum	Mg/L	Oil refining enterprises	<10

Note:

Methyl orange alkalinity with calcium carbonate Meter;

Silicic acid with silicon dioxide Meter;

Magnesium ion Calculated by calcium carbonate.

1. Closed system circulating cooling water Water quality standards Should be based on Production process Condition determination;

2. Design of circulating cooling water for open system Concentration multiple It should not be less than 3.0. The concentration multiple can be calculated as follows:

N=QM/QH+QW (3.1.9)

In the formula, N concentration multiple;

QM make-up water volume (M3/H);

QH sewage volume (M3/H);

QW Wind loss Water volume (M3/H)

3. Open system circulating cooling Aquatic Heterotrophic bacteria The number should be less than 5 × 105/mL, and the amount of clay should be less than 4ML/m3;

technical parameter

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one Flow range ：　40～2400 m3/h

two Filtering precision ：100～2000 μ m

three working pressure ：　0.1～1.6 MPa

four pressure loss ：　≤ 0.016 MPa

five Blowdown valve Caliber: DN 50 mm

6. Blowdown time: 10~60 s

7. Blowdown water consumption ：＜1%

8. Applicable temperature: ≤ 85 ℃

9. Power supply: AC three-phase 380V/50Hz

10. Control interface: digital display, knob, switch

eleven Strainer Type: 316 stainless steel

processing method

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The treatment of circulating cooling water can be summarized in the following four aspects:

1. Removal Suspended solids ：

Add side filter device, and the side filter flow is generally Circulating water volume 1% - 5%, filtered Suspended matter 。

2. Control Scaling ;

soften Demineralization Or dosing Scale inhibitor 。

3. Corrosion control;

Add scale inhibitor to form a film on the metal surface to cover the metal Corrosive medium Isolation Metal corrosion 。

4. Microbial control

Add biocide.

Technical background and significance

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Circulating cooling water is a major item of industrial water petrochemical industry , electricity, steel metallurgy In other industries, the consumption of circulating cooling water accounts for 50-90% of the total water consumption of enterprises. Due to the different salt content in the raw water, the circulating cooling water must be discharged when it is concentrated to a certain multiple Concentrated water And replenish new water. For a 300000 KW condensing unit, the circulating cooling water volume should reach about 33000 tons/hour. Assuming that the salt content in the raw water is 1000 mg/L and the concentration multiple is 3, the concentrated water discharge of the circulating cooling water is about 6-8 ‰, that is, 198-264m3/h, and the new water to be supplemented is equal to the drainage and Evaporation loss The make-up water volume is about 2-2.6% of the circulating water volume, which will be about 660-860m3/h, and the amount of water resource consumption and sewage discharge is very large.

Due to the restriction of concentration multiple of circulating cooling water, a certain amount of concentrated water must be discharged and a certain amount of new water must be added during operation. Make the salt content in cooling water PH value 、 organic compound The concentration and suspended solids content shall be controlled within a reasonable allowable range. It is of great significance to treat and reuse this part of concentrated water discharge. It can not only improve the water Reuse rate It can save water resources and greatly improve the overall condition of circulating cooling water.

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