5 replies to this topic

[André Neves]

Hello!

First of all hope that you had a great Christmas and the new year that is comming will certainly be better than this that is now ending..That's what I wish to all of you.


So I'm a chemical engineering student and I'm doing a project of a process of sodium hipochlorite production. I need to design some pumps and for that I need to calculate the pressure drops. For the pressure drop in line our professor gave us the typical value of 0,5 bar. He said that will never be above it. But for example if I have a pump that has to send the liquid to the top of a tank of 5 m I have one part of the flow that is on vertical and the typical value is not valid..So the total pressure drop will be the 0,5 bar plus the pressure drop on vertical flow. However since I don't needed to calculate the pressure drop on horizontal tubes I didn't design them so I don't know the diameter or the velocity on the tubes, only know the flow rate. Is there any way to know the pressure drop of this system if I only know the high of the tower? My colleagues told me about the manometric head wich I have to know to choose my pump. This manometric head is the adding of the two pressure drops?


My other doubt is about a filter. At the end of the process I need to filter my final solution to eliminate possible heavy metals. What is the common type of filter that is used to this elimination? Since I don't know the quantity of heavy metals that are in the final solution(once is generated by corrosion of the equipments over the process..this filter is only for get sure that the final product don't deteriorate rapidly. Is there any heuristic about the design of that filter for the maximum content of heavy metals that could hypothetically exist in sollution?

Best Regards and thanks!

André

Happy New Year=)

[Padmakar Katre]

Dear,

Do the backward calculations based on the opertaing pressure of the tank and the pressure drop based on the equivalent length from your pump discharge to the tank.

Here I have one confusion as you don't know what is the final quantity of the metals( or the iron rust I suppose in your case as you mentioned the corrosion problem).

As far as I remember, I visited on bulk drug manufacturing plant during my engineering course the MOC for the process tanks as well Sodium hypochlorite preparation tank and the entire pipeline was Polypropylene as the material handled is corrosive.
Let check with your lecturer about the selection of MOC.I hope it should be polypropylene. And your query regarding the filter selection just go through any of mechanical seperation (Chemical engg unit operations book).You will find the selction criteria for the filters. Based on your requirement and the studied material related to the Filters you will be able to choose the right filter.

Waiting for your comments.

[André Neves]

Dear,
Do the backward calculations based on the opertaing pressure of the tank and the pressure drop based on the equivalent length from your pump discharge to the tank.
Here I have one confusion as you don't know what is the final quantity of the metals( or the iron rust I suppose in your case as you mentioned the corrosion problem).
As far as I remember, I visited on bulk drug manufacturing plant during my engineering course the MOC for the process tanks as well Sodium hypochlorite preparation tank and the entire pipeline was Polypropylene as the material handled is corrosive.
Let check with your lecturer about the selection of MOC.I hope it should be polypropylene. And your query regarding the filter selection just go through any of mechanical seperation (Chemical engg unit operations book).You will find the selction criteria for the filters. Based on your requirement and the studied material related to the Filters you will be able to choose the right filter.
Waiting for your comments.

Hi there! thank you for answering...

About your confusion..the equipments will be in polypropylene coated with fiber glass but some equipments like heat exchanger would be in titanium and some metal could be transfer to the solution. If everything works perfectly the final solution don't have to be filter but for security I have to put the filtration at the end to be sure that the final product when goes to the client doesn't have any heavy metals. The problem is that as it is a security instalation is for something that goes wrong that I can't quantify. So my question is if there is some heuristic based on similar situations that give us a way to design this filter.. About the type of the filter I search some books and didn't find anyone specific to eliminate heavy metals in solutions. For example a bag type I know that eliminate dust from air or other gas. But for the elimintation I need I don't find the type of filter.

Best Regards and thanks!
André

[pleckner]

Google cartidge filters and see what comes up. You will want a duplex system so you can take one out of service for change-out whilie still operating your sytem.

If your professor wants to minimize perssure drop to 0.5 bar then you have a trial-and-error calculation to do. Choose a line size at your flow and operating condistions and calculate the line loss. The head the pump has to overcome is additional to the line loss you calculate.

[André Neves]

Google cartidge filters and see what comes up. You will want a duplex system so you can take one out of service for change-out whilie still operating your sytem.

If your professor wants to minimize perssure drop to 0.5 bar then you have a trial-and-error calculation to do. Choose a line size at your flow and operating condistions and calculate the line loss. The head the pump has to overcome is additional to the line loss you calculate.

Thanks for the tip "cartidge filter". I have found many companies and maybe they can tell me the charateristics and type of filter that I need.

About the pressure. My professor don't want to minimize the pressure drop to 0,5 bar. He tell me to consider the pressure drop in line and curves as a value of 0,5 bar and I only need to calculate the pressure drop on vertical flow to a high of a tank. I think is with the formula pressure drop=density of fluid*gravity acceleration*high of the tank but I'm not sure. Do you agree with this formula to the pressure drop on vertical? Then I would make 0,5 plus this value and that would be the pressure drop that the pump would have to beat. Am I right?

Best Regards, thanks for answering and a happy new year!

[pleckner]

Happy New Year to you.

What you are calculating is not a pressure drop but the change in dynamic head of the pump discharge. It has the same affect on the pump in that is adds to the total pressure the pump must over come. The 0,5 bar you mention includes all lines, both horizontal and vertcial.

Bottom line, yes, you add this head calculation to your pressure drop of 0,5 bar. Make sure you keep your units right.