3 replies to this topic

[freeman]

Dear All,

 

I wish to design a chemical mixing tank. Chemicals are injected from the tank to a process stream. In order to calculate volume of the tank it's needed to assume a residence time. The pump flow is known.

 

Is there any criteria for residence time?Any Reference?

 

Thank you in advance.

[ankur2061]

freeman,

 

There is no general criteria for residence time for chemical mixing equipment. There are many factors which influence the residence time for any mixing operation. Some of them are listed below:

 

1. What are you trying to mix - liquid-solid (liquid- powder, liquid-granules), liquid-liquid (thin liquid- viscosus liquid, thin liquid-emulsion)

 

2. What type of mixing are you trying to do - Blending / Dispersion / Dissolving / Suspension Preparation / Emulsification

 

3. What type of mixing device you want to use - Turbine, Propeller, Paddle etc.

 

4. Are there any other consideration such as degradation due to heat of mixing, caking of the chemicals to be mixed.

 

In most cases the residence time for chemical mixing to obtain a mix recipe is provided by the supplier of the chemical and this proves more than adequate.

 

Hope this provides some guidance.

 

Regards,

Ankur.

Edited by ankur2061, 27 June 2013 - 03:06 AM.

[freeman]

Dear Ankur2061,

 

Thank you so much for your recent reply.

 

The solution is Citric Acid solution which is prepared by mixing the powder and water.

 

Blending is uded to prepare the solution by the use of propeller.

 

There is no cake formation or degradation.

 

 

I'm trying to do a prelimiary design in order to calculate the dimensions of the chemical mixing tank.

 

Thank you again.

 

 

 

freeman,

 

There is no general criteria for residence time for chemical mixing equipment. There are many factors which influence the residence time for any mixing operation. Some of them are listed below:

 

1. What are you trying to mix - liquid-solid (liquid- powder, liquid-granules), liquid-liquid (thin liquid- viscosus liquid, thin liquid-emulsion)

 

2. What type of mixing are you trying to do - Blending / Dispersion / Dissolving / Suspension Preparation / Emulsification

 

3. What type of mixing device you want to use - Turbine, Propeller, Paddle etc.

 

4. Are there any other consideration such as degradation due to heat of mixing, caking of the chemicals to be mixed.

 

In most cases the residence time for chemical mixing to obtain a mix recipe is provided by the supplier of the chemical and this proves more than adequate.

 

Hope this provides some guidance.

 

Regards,

Ankur.

 

[breizh]

  As you can see in the table below the solubility of citric acid in water is quite high , it should not be difficult to prepare the solution at the  right concentration to avoid the crystallization . Knowing the usage (kg/h of solution) , you can define the capacity needed . Is you process continuous or batch ? if Continuous you might need a preparation tank and a buffer to feed continuously the  process. 

 

Hope this helps

Breizh

 

 

Temperature and Water Solubilities in Grams of Solute per 100 mL of Water

 

Temperature ºC

Solid citric acid

 

0

49

 

20

59

 

30

64

 

50

71

 

70

76

 

100

84

Edited by breizh, 27 June 2013 - 07:10 AM.