Natural gas - Black powder 1

[dkf]

Could anyone help in clarifying following situation
Natural Gas system operators complain of what we literally call as BLACK-POWDER. This undesirable highly abrasive powder is removed in the entrance of city-gates via Cyclone filter plus cartridge filters.The natural gas is previously processed in a refinery where its heavy fractions are removed and its sulfur contents substantially reduced(it is not sour gas).
Is this arrangement the best technology available/in use today? Are there any special specs for natural gas pipes in order to avoid the corrosion and powder formation?
TIA

 

[ghaz]

filters are typically a good response to your problem.
Make sure to blow down regularly.
it is unusual to see the black powder you describe in high pressure lines steel lines, usually seen in low pressure and copper gas lines.
May want to check if company wants to start to use wire brush pigs for cleaning.
Typical specs for the steel line are API5L grade B or better (ususally X42 or better)

 

[dcasto]

What you have is Iron Sulphide (iron pyrite, fools gold, FeS). It is formed by the H2S in the gas reacting with the steel line. It is very common material in pipelines. Filtration is about the only way to get it out. From experience, I've seen the FeS particles pass through compressors, water wash systems, separators taht slow gas velocities down to under 3 ft/sec. You are doing the right thing. Change the filters based of volumed passed, not just time.

 

[erwo]

Hi.

A customer has problems with this powder in their gas terminal receiving 500 mmscfd of gas at 2000 psi. It fills up their mol-sieve and other equipment. The particle size is 90 micron average, with 90% above 10 micron. The rate is 1 ppm on a weight basis. It spontaneously combusts in air, so they are keen to stop it getting in. They are installing PALL 10 micron filters in a pig-trap as a temporary thing, but are considering cyclones for a permanent solution. Cyclones generally do poorly at low loadings, can anyone suggest a better filtration system design?
Regards,
Erik.Wolff@no.abb.com

 

[Liamohalmhain]

Black dust formation (Copper Suphide) is a common whenever the Hydrogen Sulpide levels in natural gas exceed 1.5 mg/cubic metre (about 1 ppmv) Natural Gas specification usually allow up to 7 mg /cubic foot (even the ISO standard for Natual Gas) What I am looking for is a way to protect the inside of copper pipes to minimise the need for cleaning fiters and blocked valves and orifices. The UK HSE have published a research paper which concludes that while no significant increase in safety hazards arise, issues of concern to domestic gas consumers arise (loss of heat output, and the need for more frequent servicing) see

http://www.hse.gov.uk/research/crr_pdf/1998/CRR98184.pdf

Any solutions?