3 replies to this topic

[iplan]

Dear members,

We have a single stage Sour water stripper operating at 10 psig overhead pressure and with steam stripping ( 150 psig) steam. we have observed that for steam optimization, it is beneficial if 50 psig steam can be used in place of 150psig steam for our configuration.

current operating conditions
Tower overhead pressure - 10 psig
Bottom temperature - 258 Deg F.
Sour water concentration - H2S - 13000 PPM, Ammonia - 8000 PPM.
Stripping steam - Temp - 400 Deg F, 150 psig
50 psig steam conditions - temperature - 350 Deg F, pressure - 50 psig.
Stripper feed rate - varies from 110 USGPM to 300 USGPM.
Column trays - 35 sieve trays

Based on my estimations, from the bottom temperature and column pressure levels , the usage of 50# steam looks feasible. Also , the enthalpy difference between the two steam levels is minimum. Any restrictions on the column thruput are also acceptable.

I request the esteemed members to let me know the factors to check the feasibility of using 50 psig steam in place of 150 psig steam.

Thanks in advance,
Iplan

Edited by iplan, 12 February 2012 - 01:02 PM.

[S.AHMAD]

1. From mass and energy balances, there is no problem. More steam may be required for sensible heat since the steam temperature is lower. But you can do energy and mass balance to confurm the above,
2. If you are using the same control valve, the valve may not be adequately sized.

[iplan]

Mr Ahmad,

My apologies for this late reply.

I tried doing the enthalpy balance , but unfortuantely all the flows around the column are not available and hence the difficulty.

But taking cue from your post, the enthalpy of 150 psig steam is 1216 btu/lb ( @ 400 deg F) and the entahlpy of 50 psig steam is 1194 btu/lb (@325 deg F). Also, the latent heat is higher in 50 psig steam ( 912 btu/lb) than 150 psig steam ( 857 btu/lb).

Based on this, the differences in enthalpy would be minor in my opinion.

I welcome your thoughts on this.

Many thanks
iplan

[S.AHMAD]

iplan

1. My comments earlier was done without looking at the detail figures, it was based on "common sense".
2. However, after studying the figures, I am of the same opinion as you.
3. Most likely, the steam required by 50# is less than that of 150#.
4. Only energy/enthalpy balance can confirm that argument