Mercury contaminates aluminum cold box equipment by its precipitation from gaseous and liquid streams during liquefaction and separation processes. Its precise form upon precipitation is not known conclusively; however, it is hypothesized that it forms finely dispersed aggregates that deposit on the walls of aluminum piping. Upon warming of the cold box during shut down, a portion of the mercury coalesces and can form droplets and in extreme cases, pools.
The presence of mercury in natural gas and hydrocarbon streams and the resultant liquid metal embrittlement problems encountered in low temperature processing equipment stimulated various approaches to removing the mercury both from the process streams and the equipment. A recent patent.sup.[1] described the use of alkali polysulfides to remove trace amounts of mercury from liquid hydrocarbons at a pH range of 8-11. Another patent.sup.[2] used an ionexchange resin containing active thiol groups that removed more than 97 percent of the mercury from hydrocarbons. A method for treating mercury contaminated aluminum surfaces rendered the mercury and amalgam harmless with the use of hydrogen sulfide in a solvent..sup.[3] FNT 1. Yan Tsoung Y., U.S. Pat. No. 4,915,818; Mobil Oil Corporation (1990). FNT 2. Duisters. Henricus Antonius Maria and Van Geem, Paul Christiaan, Eur. Patent Appl. EP 319,615; Stamicarbon BV (1989). FNT 3. Craig, Howard L., U.S. Pat. No. 4,830,829; Mobil Oil Corporation (1987).
A process removed hydrogen sulfide and mercury from natural gas using an alkali metal peroxomonosulfate salt..sup.[4] A clean up procedure decontaminated equipment containing mercury by circulating a solvent containing sulfur, H.sub.2 S, sulfides or alkylthiol through the equipment to produce mercury sulfide..sup.[5] Mercury was removed from natural gas by utilizing an absorbing hydrocarbon which was subsequently separated out..sup.[6] Zeolite or alumina was treated with sulfur or sulfur compounds which removed mercury from natural gas or liquid hydrocarbon streams..sup.[7] Similarly, mercury was removed from a gas or liquid by passing it over alumina or silica containing a copper sulfide..sup.[8] FNT 4. Audeh, Costandi A., U.S. Pat. No. 4,786,483; Mobil Oil Corporation (1988). FNT 5. Yan, Tsoung Y., U.S. Pat. No. 4,764,219; Mobil Oil Corporation (1988). FNT 6. Taraked, Ramanathan R., Crawford, Duffer B., U.S. Pat. No. 4,693,731; MW Kellogg Company (1987). FNT 7. Chao, Chien C., U.S. Pat. No. 4,474,896; Union Carbide Corporation (1983). FNT 8. Sugier, Andre and laVilla, Florentino, U.S. Pat. No. 4,094,777; Institut Francais du Petrole (1978).