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Since 1875 CONNELLY-GPM INC. has been creating quality products used to protect the environment and serve the energy and construction industries


IRON SPONGE gas purification is a process originally developed for cleaning coke oven gas to remove hydrogen sulfide (H2S) resulting from the sulfur in the coal. This product called IRON SPONGE is hydrated iron oxide on a carrier of wood shavings and chips. IRON SPONGE is most frequently supplied with 15 pounds of iron oxide per bushel of product. IRON SPONGE, which has been used for many years to treat other gas streams, is a very simple way to remove the corrosive, bad smelling H2S. It works to effectively remove the sulfide from the gas stream by forming stable iron sulfide, a solid. This simple process is effective for high-pressure natural gas applications, low-pressure systems, and sewerage gas from anaerobic digestion of sewer sludge. A new use for this process is treating the gas produced by landfills. This landfill gas, or biogas, is similar in composition to sewerage gas. After purification, this can be used as fuel or flared without the problem of SO2 in the exhaust.

The purification process consists of down flow gas through a packed bed of IRON SPONGE, with the iron oxide reacting with H2S to produce iron sulfide and water. The water moves down through the bed with the gas and should be drained off to prevent accumulation. If mercaptans, the malodorous sulfur compounds in some gas streams, are present, they are also removed by IRON SPONGE.

For IRON SPONGE to effectively perform, it must be maintained within a range of moisture levels. This requirement is usually satisfied if the gas is saturated with water vapor, as is frequently the case. If not, a simple water spray will correct it. An excess of water is tolerated very well by IRON SPONGE as long as the excess is drained off, so as not to flood the bed. Also, the reaction of iron oxide with H2S produces water, contributing to proper hydration. Monitoring the drip water is an easy way to check the moisture level, pH, and reactivity. Since the iron oxide is impregnated into the wood surface, it will not wash off or migrate with the gas. If IRON SPONGE has dried in storage it can be re-wet and still be effective.

To minimize downstream corrosion problems caused by H2S, the process should be located as close to the source of gas as possible. The process should be after a gas/liquid separator and before the dehydration process. The maximum temperature should not exceed 120F. The minimum temperature is 50F, or whatever is necessary to avoid hydrate formation for the system pressure and composition of the gas.

The IRON SPONGE reaction is not pressure sensitive and is not affected by other gas constituents. Liquid hydrocarbons, however, should be effectively separated and removed before IRON SPONGE treatment.

The equipment needed for IRON SPONGE treatment consists of a vertical vessel (of at least 8 feet of straight side for high pressure service, or 5 feet for low pressure service), which is filled with IRON SPONGE. The gas is passed down flow with the H2S removed to meet pipeline requirements until the IRON SPONGE is exhausted. Then it is either revivified or replaced. Most installations can effectively operate on a single bed. If continuous operation is desired, then an alternate vessel and piping is needed to operate without interruption. Valves can be arranged so either bed can operate while the other is serviced.

Because IRON SPONGE produces a narrow fouling front, it is seldom necessary to operate two vessels in series.

The carrier used for IRON SPONGE is a carefully selected blend of wood shavings and chips having a range of particle sizes promoting intimate gas contact for efficient treatment.

Equipment can be set up to allow in-place revivification, either continuously by oxygen in the gas stream or by taking a unit off line and revivifying. Bed life in excess of theoretical anaerobic limits can be realized, thus lowering both product and labor costs.

Spent IRON SPONGE passed E.P.A. leachate tests, and O.S.H.A. definitions of a "not readily ignitable solid" and can be disposed of in landfills. Aerobically spent IRON SPONGE is not pyrophoric and is ready for landfill disposal. Anaerobically spent IRON SPONGE is only pyrophoric if not kept properly moist and exposed to air long enough to exothermically reverse the sulfur-iron reaction. Once that is complete it is ready for disposal.

IRON SPONGE has been successfully used since 1875 by major oil and gas companies, many independent gas and pipeline companies, and a variety of industries both in the U. S. and world-wide. IRON SPONGE customers are using the product to remove H2S to meet pipeline standards, sweeten fuel gas to minimize equipment deterioration, eliminate odors, or comply with air emission standards regarding sulfur dioxides in stack gas.

IRON SPONGE has passed federal E.P.A. leachate tests and is classed as E. & P. Wastes, Subtitile D as: Non-Hazardous Substances.

CONNELLY-GPM has been the industry leader in the IRON SPONGE business since 1875 and has the foremost product of its type available today. Our engineers are interested in helping you with your applications. Please call: (773) 247-7231, or fax: (773) 247-7239.