Difference between Scrubber and separator 1

[assouma]

Hello,
Please can you tell me about the difference between a separator and a scrubber?
Regards

 

[BigInch]

a scrubber knocks out dropletts and/or dust/dirt particles in a gas flow.
a separator splits oil/gas/water combined flow into three "separate" streams.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[pennpiper]

Separator:

http://www.royalguardstrainers.com/steamairseparators.html

Scrubber:

http://www.engineeringtoolbox.com/scrubbers-air-washers-d_139.html

prognosis: Lead or Lag

 

[zdas04]

From my 1981 Vessels, Piping, Exchangers course. A "Separator" must have all of:
[ol 1]
[li] Primary separation of liquids and gases[/li]
[li] Sufficient liquid capacity to handle expected surges of liquid[/li]
[li] Sufficient height to allow droplets to settle out by gravity[/li]
[li] A means of reducing turbulence in the main body of the separator so that proper settling can happen[/li]
[li] A mist extractor to capture droplets too small to settle by gravity[/li]
[li] Proper liquid level controls[/li]
[/ol]

A "scrubber" is missing one or more of the above. It is common for a scrubber to lack #2, #5, and #6, but not always.


David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[pennpiper]

Go here and sign up for a free download of a Chemical Engineering Dictionary:

http://www.mhprofessional.com/getpa...onary_of_engineering_registration.php&cat=113

prognosis: Lead or Lag

 

[25362]

As explained above, both terms involve separation equipment.

To the list of methods used in separators, most of them implied in the list brought by zdas04, one may possibly add heat addition or removal, changes of flow velocity and flow direction, centrifugal force and, in some cases, magnetic and electrostatic effects.

Scrubbing mostly deals with "washing" gas streams as described above, but it may also include dry or semi-dry operations, e.g., adsorption, selective catalytic reactions and heat exchange.

I adhere to BigInch's definitions.
For more details I suggest to read the pertinent chapters of Perry's Chemical Engineers' Handbook, Ed VIII.

 

[zdas04]

Separators that just differentiate gas from liquid are still "separators". A device that does not further separate liquids into oil/water can still be a "separator".

Separators and scrubbers both can have incidental added heat, but if the heat added or removed is more than incidental then the vessel falls into the family of "Heater/Treaters" or "heat exchangers" not separators/scrubbers. Changes in flow direction and/or centripetal acceleration are used in most categories of treatment facilities and are not characteristic or defining. In my experience both separators and scrubbers are "mechanical" devices, and adding electrostatic or magnetic elements would put the device into a different category. Absorption, adsorption, and catalytic reactions would also put the device into a different category.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[25362]

No doubt a wide variety of separation devices have been devised and are in use.

In electrostatic separators the particles in the particle-laden gas stream are pre-charged to a certain charge in a pre-charging section and penetrate through the grounded electrode into a separating section, where the particles are separated from the particle-laden gas stream.

Mag separators are used mainly in solid-solid and liquid-solid separations in the ceramic, pharmaceutical and food industries. All of these devices are called "separators".

The web brings several sites concerning 'dry' scrubbing.
Dry scrubbers -considered a relatively new technology- use absorption and adsorption to remove SO₂, HCl, HF, and other acidic gaseous pollutants mainly from combustion flue gases (coal burning, incinerators). Some scrubbers also adsorb vaporous organic compounds and metallic compounds.
These systems use finely powdered, fluidized, high surface-area alkaline material such as Ca(OH)₂ or NaHCO₃ followed by a dry Venturi scrubber for better mixing and a fabric filter collector. It is claimed that they offer superior particle collection, higher absorption efficiencies with less energy usage than wet scrubbers.

Possibly 'dry' scrubbers and 'non-conventional' separators should be differently named...

 

[zdas04]

It is kind of like "roads". Any pre-established path with adequate width for a four-wheeled, self-propelled vehicle is called a "road". If the turn radius is greater than some pre-determined value, and it has multiple lanes designated for each direction, and the road base is adequate for high-speed traffic, and ingress/egress is limited then you can call it an "Interstate". If it doesn't meet those criteria (like the road through Glenwood Canyon in Colorado for example), someone might still call it an interstate even though it doesn't meet the definition. The language police don't come along and remove the I-70 signs on this magnificent stretch of road, the fact that the road does not meet the established definition mostly doesn't make any difference to anyone.

Same with process vessels. It makes communication easier if everyone has the same definition, but that simply isn't going to happen. I've used a lot of adsorption devices. Mostly they were called "dryers", "polishers" or "mole sieve units". I've never come across one that was called a pedestrian term like "separator" or "scrubber". Mostly I've seen electrostatic and magnetic units called "filters", but they are specialized enough that I'm not surprised that some vendors call them other terms (since "filter" seems to invoke pre-processor activities). What the Interwebz calls "dry scrubber" sounds like what I would have called a "polisher", but maybe not. I do know that if I want to put a "scrubber" on a natural gas gathering system in front of a compressor station it won't have adsorption media, electrostatic elements, magnetic elements, catalyst, or other than incidental heat.

"Separator" and "Scrubber" have historically invoked gross-level mechanical separation of fluid phases (and in many cases further separation of liquids with easy density differences) with phase changes limited to incidental quantities (a vessel primarily intended to cause a phase shift seems to want to be called a "flash tank").

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[25362]

In spanish (my mother tongue) separators are indeed called separadores, but scrubbers are called depuradores (!) as purifiers, probably because they were originally designed to clean up air for anti-pollution reasons.

Let's hope the day will come when new terms, or clever portmanteaux, will be universally accepted to describe separators and scrubbers according to their uses or processes.

Nil desperandum.

 

[BigInch]

Gracias 25362.
As we can see, only the most general definition applies to the question asked, being that it did not mention any specifics concerning particles, gas, liquid, water, soot, etc., or anything else.

A separator-scrubber might also be a pan for finding gold, if the nuggets come out of the pan ... clean.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek