5 replies to this topic

[bernath]

dear all,

I'm currently designing particulate matter(PM) and gas removal system for fluidized gasification plant. It's been decided that we will use wet scrubber such as, venturi scrubber or vertical spray tower as 1st stage PM removal system prior to wet ESP.

The problem is I don't have enough detail information(such as, how to calculate pressure drop, equipment sizing, collection efficiency, etc) of how to design this scrubber. Do you have any recommended books, journals or literature that can help me?

My only reference book is 'Air Pollution Control Technology Handbook' by Karl Schnelle and Charles Brown. I'm currently looking for 'Wet Scrubbers' by Howard Hesketh and Kenneth Schiffner and so far haven't found it yet. If anybody can help...

many thanks

regards,
bernath

[fra.telli]

dear all,

venturi scrubber or vertical spray tower as 1st stage PM removal system prior to wet ESP.

Hi Bernath!
That was just my work up to 2 yrs ago...

I can give you litterature reference, but before that, what are you looking for?
- rules for "do it by yuorself"?
- thumb rules for first dimensioning?
- shortcut for supplier comparison?

Anyway, let me know particle rough distribution (both diameter&weight distribution).
There are many way to design such a system...

For example:
variable throath venturi: dP=300-1200 mmH20 (up to 2000 mmH2O)
Scrubber tower (with valve trays and mesh/demister): dP=>300 mmH20
Wet ESP: dP=100 mmH20

Do you need to remove just particles, or need to adsorb gas fraction either?

bye

[bernath]

hi fra.telli,

Glad to know you!

I think I'm looking for " thumb rules for first dimensioning" and/or "rules for do it by yourself" since the company has opted not to purchase the equipment.

I haven't got the particle size distribution yet and still waiting for it from the reactor guy. Nonetheless, I've done some digging and pretty sure that I will use either venturi or spray tower as 1st stage of PM removal system prior to Wet ESP(WESP). WESP is selected due to the stickiness properties of our PM(i.e. tar).

Let say for now that for gas removal system, I think we will specifically use packed bed or any other gas removal device rather than remove it via venturi or spray tower scrubber along with PMs.

many thanks

regards,
bernath

[pjh33hae]

Dear kanankiri,

Hi.

Pls refer to belows.

1. GPSA Engineering Data Book
2. Perry Chemical Engineer's Handbook
3. Ludwig Applied Process Design for Chemical Plants

Otherwise you could search Amazon or Barns and Noble internet search book company with words of "scrubber design" or "gas removal system".

Bye..

[fra.telli]

hi fra.telli,

Glad to know you!

I think I'm looking for " thumb rules for first dimensioning" and/or "rules for do it by yourself" since the company has opted not to purchase the equipment.

I haven't got the particle size distribution yet and still waiting for it from the reactor guy. Nonetheless, I've done some digging and pretty sure that I will use either venturi or spray tower as 1st stage of PM removal system prior to Wet ESP(WESP). WESP is selected due to the stickiness properties of our PM(i.e. tar).

Let say for now that for gas removal system, I think we will specifically use packed bed or any other gas removal device rather than remove it via venturi or spray tower scrubber along with PMs.

many thanks

regards,
bernath

Let's go through some thumb rules:
1 - the smaller the particle size (and wider distribution), higher the dP in the venturi.
High dP means high fragmentation of water droplet in venturi's throat -> higher inpact effect

2 - Packed bed vs valve trays: the second ones are better in case of salt formations and powder presence (for example in case of assorption and chemical reaction in the liquid phase with possible particles presence- ex: HCl+particles(in gas) and NaOH in water). Just remember to put a chevron or a demister in top of the column: dimensioning the chevron you'll get the column diameter

3 - WESP: are your paticles enough "sticky" to resist wash cycle? in this case wesp could be the wrong answer to your problem...

p.s.
mentioned books are really good, and should be used as basic steps!
Moreover you can find equations and correlations that are close enough to reality for first dimensioning
http://www.koch-otto...ductCatalog.pdf

[bernath]

Dear fra.telli,


It's been quite some time since our last correspondent. My apologize for not quickly replying your email.

Meanwhile, I've successfully calculate the collection efficiency of a venturi scrubber. This venturi will not used to remove any gas.

Nevertheless, I still have some questions to ask:

I. Pressure Drop(dP)

As far as I know, there's 2 equations to calculate pressure drop for venturi scrubber
1. Calvert: 'dp = 5.4e-04 * (v^2) * rho_gas * (L/G)'
2a. Hesketh: '(v^2) * rho_gas * (Throat_Area^0.133) * (0.56 + 0.125*L/G + 0.0023*(L/G)^2) / 507'
2b. Simplified Hesketh: '(v^2) * rho_gas * (Throat_Area^0.133) * ((L/G)^0.78) / 1270'

I've found some difficulties in 'when and where' to use above equations. I've tested as well all the equations and would like to attach the results for you. (By the way, do you know how to attach files here in this forum?). All the books I have, merely gave me these equations without further details of which these equations can be applied into. Please kindly advice.


II. I have used Johnstone equation to calculate the scrubber efficiency. Some of the books introduce other equations(or models) such as 'Infinite Throat Model', 'Calvert Cut Diameter' and 'Contact Power Theory'. Do you think its necessary for me to perform collection efficiency calculation based on these 3 models too? Is it enough if I cling only to Johnstone equation for collection efficiency?

In Johnstone equation, Efficiency = 1 - exp(k * (L/G) * (Inertial Impaction Parameter)^0.5).
k = Johnstone Correlation Factor which typically ranges from 0.1 - 0.3(1,000acf/gal), but is often use as 0.25.
The impact of this 'k' is very insignificant if we deal with PM which size is quite big(such as 10um), but when we use it against quite small PM size(such as 1um), I've found that my scrubber's Collection Efficiency is greatly affected by 'k'. Do you have any idea of how to select the appropriate value for this k? Is there any empiric data I can use?


III. Up to this point, I've already finished the calculation of collection efficiency and currently proceed into equipment sizing. Unfortunately, I haven't found anything yet related to venturi scrubber sizing equation. Could you please kindly let me know the literature or books that contain those informations.



Thank you

Best Regards,
bjajadi