treatment of sour gas from sour water stripper 1

[ponderer]

In our refinery, the sour gas from the sour water stripper is sent to the sulfur recovery plant.

It make trouble to the sulfur recovery plant.
(plugging and corrosion)

Is there any new process that can treat this sour gas stream?

The composition os this stream is:

H2S: 40%
NH3: 30%
With balance N2, H2O,HC

 

[AUSLK]

As a former Sulfur Plant Optimization Engineer, I have visited many plants and conducted optimization testing on them. The issue you have is getting adequate destruction of the Ammonia in the sour gas stream. With a typical reaction furnace temperature of 1800-2000F the ammonia does not fully destruct and it then forms ammonium salts that crystallize and plug/corrode the plant. To fully destruct the ammonia you need ~2800F to accomplish this. If the HC's in your feed stream are not sufficient to do this, then the most common (&costly) cure is to switch to oxygen enriched air. Removing the nitrogen from the air stream allows the reaction furnace temperature to increase dramatically (less inert mass to heat up). This is usually done by pure oxygen injection into the reaction furnace and backing off on the air input. Make sure your reaction furnace and burner are capable of this, it may require some modifications.

The other alternative is to remove the ammonia source from the feed stream, but then of course, it must be treated elsewhere.

 

[JohnSames]

Plugging is a common problem often overcome by raising the temperature of all equipment in the train above 155C, however, this is only a band-aid solution.

The key is the RF temperature and the two patents on the process cite 1250C as the required temperature. Every burner and RF has its own characteristics and some manage at lower temps. It depends on the burner and mixing characteristics, and the relative load of SWS gas to AG.

Testing for NH3 breakthrough at the WHE outlet is the only way of determining your RF capability.

There is a detailed paper on this topic available on our website.



John A. Sames
President
Sulphur Experts Inc.

http://www.sulphurexperts.com

 

[Finfan]

We had the same problem on our refinery a number of years ago, the SWS offgas caused plugging, corrosion and PH problems, the eventual solution was to burn the offgas on a gas fired heater on another part of the plant.

 

[AUSLK]

Finfan,

Typically that stream is ~30% H2S also, so in most cases, burning it directly without further downstream treatment would violate environmental regulations/permits for SO2 emissions.

 

[JohnSames]

Burning the sour water stripper off-gas in an incinerator or heater may be a solution in some countries, but in most countries is now not an option because of the amount of H2S associated with this stream (typically 33%). This H2S has to be recovered as S in the SRU.

There are ways to handle SWS gas successfully in the SRU as is done in countless refineries around the world. The key is sufficent temperature and mixing in the reaction furnace.



John A. Sames
President
Sulphur Experts Inc.

http://www.sulphurexperts.com

 

[25362]

Refinery sour-water streams could be stripped in two pH-controlled columns operating in series. The first column fed with a pH=4, releasing H[sub]2[/sub]S-rich gas as overhead. The 2nd tower with a pH=11, eliminates the NH[sub]3[/sub] as overhead. Both towers are steam-stripped. pH values are controlled by suitable injections of H[sub]2[/sub]SO[sub]4[/sub] to the first tower feed, and of NaOH to the second tower, both using in-line mixing. In this manner one gets two gas streams that may be further processed. The pH of the spent water (2nd column) may have to be brought down for disposal; this water cannot be recycled because it contains sodium sulphate, which would accumulate with reuse.

A processing step as the one above should be economically and environmentally weighed against others such as incineration and SRUs as JohnSames advises.

 

[MAJOSA]

Check out

http://www.zeolife.co.uk

Natural Zeolite from them can remove Ammonia and H2S .
MARK Baty
Chairman Euremica Group
markbaty@euremica.com