NaHS production with H2S 1

[ccl82chew]

"NaOH can be used in a packed tower to scrub the H2S. If your plant is near a paper mill, they use lots of NaHS, and may be able to purchase your scrubber effluent"

The above statement is true. However, i have excess NaOH if i use the above process. Is there any other process for the production of NaHS? using NaOH and H2S? where is it done and how is it done?

 

[mbeychok]

ccl82chew:

Caustic scrubbers are widely used in petroleum refineries to remove hydrogen sulfide, mercaptans, phenols and other acidic compounds from various streams. When caustic is used to scrub liquid propane to remove H₂S, the intermediate reactions are:

2NaOH + H₂S ==> Na₂S + 2H₂O
Na₂S + H₂S ==> 2NaSH

Summing the above two reactions, the overall reaction is:

NaOH + H₂S ==> NaSH + H₂O

The spent caustic from such scrubbers has indeed been sold to paper mills by some refineries.

If the spent caustic from scrubbing liquid propane contains any sodium mercaptide, that makes the spent caustic difficult to sell.

The spent caustic, from scrubbing naphtha (or jet fuel or light kerosene) in refineries, will very probably contain some sodium phenolate, sodium cresolate and/or some sodium naphthenate in addition to NaSH. Such spent caustic is very difficult to sell or dispose of.

Milton Beychok
(Contact me at www.air-dispersion.com)
.

 

[ccl82chew]

thanks for the reply..
is there any economical way of removing H2S gas, of which we can do something with it (eg. producing sellable NaSH with caustic and H2S). we have a plant which is producing lots of H2S gas, but it would be costly to use NaOH for removal of H2S. Any other options or ways?

 

[mbeychok]

ccl82chew:

You need to provide more information. What do you mean by "lots of H2S gas"? Please provide:

(1) How much gas per day at what temperature and pressure
(2) A complete compositon of the gas (i.e., what else it contains other than H2S)
(3) What does your plant produce and how large is it?

Petroleum refineries use aqueous solutions of monoethanol amine (MEA) or diethanol amine (DEA) to remove and recover H2S from their by-product offgas. The recovered H2S is then catalytically converted to elemental sulfur for which there is a very large market. But in refineries, we are talking about 50 to 600 tons per day of H2S. In other words, it takes a very large amount of H2S to economically justify an amine unit and a sulfur conversion unit.

I would also point out, if your plant is in the USA, Canada, Western Europe, Australia or many other countries, environmental regulations will not allow you to vent the gas to the atmosphere or to incinerate your H2S-rich gas. You must remove the H2S and convert it into some non-gaseous byproduct.

Milton Beychok
(Contact me at www.air-dispersion.com)
.

 

[kenvlach]

If your gas stream is fairly small, don't waste effort trying to get a sellable product. Scrub the H₂ out by bubbling the gas through an aqueous solution of ferrous iron (Fe⁺²). Gives small, dense precipitates that readily settle. The reaction is quick & you don't have the problem of NaOH absorbing CO₂ (if present).

 

[kenvlach]

"Scrub the H₂ out" should of course read
"Scrub the H₂S out"