Arsi-Guard™ is Newpoint's proprietary catalyst-based system for removing arsenic from natural gas. Arsi-Guard™ can reduce organic arsenic concentrations to below 1 ppb, eliminating environmental liability and improving primary catalyst performance in ammonia and LNG facilities.
The first arsenic removal system in the world was installed in 1988 at the Abo Field in New Mexico by principals at Newpoint Gas. After several trials, the resulting system has remained online removing arsenic for over 19 years and has treated a cumulative gas volume of 750 Bcf. Newpoint has experience removing arsenic from an inlet concentration of 1,200 µg/m3 (960 ppb w/w) down to a consistent, low residue concentration.
Accurately measuring arsenic concentrations in a gas stream has proven extremely difficult. Newpoint also offers arsenic measurement solutions using a validated process with a 17 year history. We have procedures and equipment that can measure arsenic levels to less than 0.1 µg/m3.
Arsenic has considerable economic impacts on industries that use natural gas. Methanol, ammonia and hydrogen plants all use catalysts that degrade over time due to catalyst poisons, including sulfur, mercury and arsenic, which reduce the capacity and efficiency of the plant. This has led to catalyst guard beds that remove sulfur and other catalyst poisons before the gas reaches the catalyst. In the case of arsenic, guard beds have been reasonably effective at removing inorganic arsenic from the inlet gas stream, but organic arsenic compounds are far less reactive and are not removed in the guard beds. The organic arsenic then reaches the catalyst and begins fouling it. The downtime associated with catalyst change-outs and reduced plant capacity represent a considerable loss of income and a costly maintenance issue that has long been treated as a cost of doing business. That is no longer the case: Newpoint's Arsi-Guard™ system gives the natural gas industry the tools to manage organic arsenic at low capital and operating cost. The treatment is efficient at ambient temperature and can reduce organic arsenic concentrations to below 1 ppb.
The most common form of arsenic in natural gas is not arsine (AsH3) but a group of compounds called trialkylarsines, which include trimethylarsine, dimethylethylarsine, methyldiethylarsine and triethylarsine (see table below). The trialkylarsines are considerably less reactive than arsine, which makes them more difficult to remove from natural gas. These considerations, among others, make the arsenic problem difficult to solve. The natural gas industry is becoming more aware of arsenic-contaminated natural gas and its potential legal and financial consequences.
| Compound | Percentage of Total Arsenic Compounds |
|---|---|
| Trimethylarsine (TMA) | 70% |
| Dimethylethylarsine (DMEA) | 20% |
| Methyldiethylarsine (MDEA) | 8% |
| Triethylarsine (TEA) | 2% |
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