Acid Phase Reactor Pressure Issue

[lavic2009]

Hello Everyone,

I am currently working on an US-based waste water related engineering project. This project involves the heating of sludge (6% solids) from about 37-55 degrees Fahrenheit to about 97 degrees Fahrenheit for a 2 phase biological digestive tank system.

In the setup, the sludge is continuously recirculated as new cool sludge is injected into the system. Overflow pipes carry the excess heated sludge of to either high rate digester tanks or egg shaped digesters.
The cool sludge gets pumped via four to six recirculation pumps at a rate of 500-1000 gallons per minute each to a height of 116 feet. At the top, the cool sludge will be mixed with hot steam via three steam injectors. The pressure should be low enough (below 10 Psi) for this to occur. After the incoming sludge has been heated it will enter the acid phase reaction vessel/tank via a pipe that runs almost the entire length of the tank. At the bottom of the tank is an opening where the process starts all over again. (See diagram). As mentioned above the excess heated sludge is carried off via overflow pipes.
Given this setup, I am not totally sure if the heat-injected sludge will have enough pressure to overcome the hydrostatic pressure of the sludge that is already in the tank. Is the setup , given my description and the diagram, viable and theoretically workable or is a redesign necessary?

I would appreciate any feedback on this project. Please let me know If you need additional information, Thanks in advance!

 

[bimr]

The static head in the tank should add onto the dynamic head put out by the pump. The resultant head should be adequate.

Has your project had a process hazard review? The condensing steam may collapse the tank.

 

[lavic2009]

Hello Bimr,

I do not toally understand what you mean by collapsing tank. The steam will be injected into the sludge at the top of the tank. This heated mixture will then be enter the tank via the large pipe. No condensation should take place at this part of the system.

What I missed to mention earlier, is that there is also a gas venting pipe at top of the tank. So our concern really is just about the pressure required for us to pump the sludge in the tank to atleast the overflow level continuously.

Thanks Again !

 

[lavic2009]

I attached an updated diagram to this post. This should clarify things a bit better. Thanks again !

 

[bimr]

When 5 psig steam condenses, the change in phase causes a reduction in volume of 1700:1. The result is a vacuum condition. Tanks are not usually designed for full vacuum.

This condition commonly occurs when maintenance workers steam clean tanks without vacuum relief.

http://www.sache.org/beacon/files/2002/02/en/read/2002-02-Beacon-s.pdf

http://www.railroad.net/forums/viewtopic.php?f=9&t=63568

 

[lavic2009]

Hello Bimr,

We do have release mechanisms in the design that would prevent any implosive event.
I just want to know if there is enough pressure to push the medium from the bottom of the tank to the overflow line.

Remember, that at the top of the tank the medium is basically lead to the bottom of the tank via a pipe (See new diagram). If the pressure is so low, how can the hydrostatic pressure of the medium that is already in the pipe and the tank be overcome?

I have attached a simplified diagram to show what I mean.

Thanks

 

[bimr]

You have 101.5 feet of water and you are pumping it to an elevation of 116 feet. You only need to add the energy to pump it 15.5 feet of elevation plus the pressure drop in the pipe.

Your incoming pump must also be capable of pumping to the 101.5 feet elevation.