3 replies to this topic

[TS1979]

Dear all,

The attached file shows a high stripper design and mass balance table. The stripper is to remove ammonia from the condensate. The estimated max ammonia level in the condensate is about 470 PPMW and the targeted ammonia in the stripped condensate is 2 ppmW. My questions are:

1, The temperature and pressure differences are only 1°C and 1 psi between the column bottom and the top with the total column height of 72', what is the HETP (height equivalent to theoretical plate) for the random packing?

2, As the feed temperature is below the column top vapor outlet temperature, what will be the profiles of temperature, liquid/ vapor loads near the feed nozzle and feed distributor?

3, For the steam nozzle design: Is the "V" baffle enough to distribute the steam uniformly within the column or a distributer required?

Thanks in advance.  Condensate Ammonia Stripper.xls   84.5KB   253 downloads

[TS1979]

Does anyone have any thought regarding this design?

Thanks.

[Art Montemayor]

TS1979:

This is a very tall vessel, with a height to diameter ratio of 72/6.5 = 11. This is a very large L/D ratio. How do you intend to install this vessel? Your outline drawing does not show any skirt or lugs, so I have to assume you will weld anchor lugs on the top portion of the tower and hang it from a steel frame or inside a building.

Refer to the attached revised workbook.
You show that the feed condensate is at 226 ^oC and 516 psig. That is super cooled condensate by approximately 20 ^oC. However, your “mass balance” table is messed up. Your temperatures seem to be reversed. Your bottoms condensate is hotter than your overheads steam – and both are supposed to be approximately saturated. That can’t be; the overheads steam is supposed to be exactly that: STEAM VAPOR. Yet, the thermo properties table clearly show it to be a liquid. I think you got your properties reversed.

I can’t make any comments on the dimensions or the mass balance since these calculations are not included. Simulation program results are not calculations, so they can’t be checked or verified without running another simulation. Therefore, how the total overall height of 72 feet was arrived at seems to be a mystery and we can’t comment on it. Personally, I feel that 6.6 feet of tower diameter is small for the flow rate of 600 gpm – but that is my suspicion and can’t be verified.

I would certainly recommend that an efficient steam sparger distribution system be incorporated on such a large tower.


I hope this helps.

Attached Files

•  Condensate Ammonia Stripper Rev1.xls   95KB   218 downloads

[TS1979]

Art, I appreciate your comments and time.

1. The column will be setting on a 22 ft skirt (I don't know why they put the column on so high skirt. It seems to me that hydraulic for the stripped water to the destination shouldn't be a problem because the column operating pressure). Anyway, the installation is not my concern. It will be taken care by the construction specialist.

2. You are right. The temperature above the feed distributer is reversed. The feed reaches its temperature by recoverying heat from the stripped condensate. The overhead temperature was obtained by heat and mass balance. Since superheated steam is used for the stripping operation, the sensible heat of the superheated steam will be used to heat the subcooled feed and at same time create some extra steam (the overhead flowrate is larger than the stripping steam flowrate).

3. The overhead should be steam vapor at its dew point temperature. There may be some inaccurate estimation in the simulation software or the pressure and temperature presented are an rounded value.

4. I don't have the simulation file either. The reason I put this query is that the design seems to contradict to my believes:

a, a larger pressure and temperature differences between the top and the bottom should be or a shorter column is required

b, shouldn't have temperature reverse inside the column.

Thanks again for your comments