Synthetic Natural Gas (SNG)

How SNG is made and Distributed

Since Hawaii has no naturally occurring source of natural gas like those found on the mainland, Hawaii Gas produces Synthetic Natural Gas (SNG) from a petroleum by-product called naphtha. While SNG is created artificially, its properties are similar to that of natural gas found and used on the mainland and throughout the world.

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    Remove sulfur

    To produce SNG, the sulfur contained in the naphtha feedstock must be removed. To accomplish this, naphtha is blended with hydrogen gas, heated to 700 degrees Fahrenheit and sent through a reactor vessel where a chemical reaction takes place to remove the sulfur.

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    Produce methane, hydrogen and carbon dioxide

    The purified feedstock is then sent to a series of reactors where it is blended with super-heated steam and passed through a catalyst of nickel pellets. The result of this process is gas composed of primarily methane, hydrogen and carbon dioxide. After the reactors, the gas flows in two separate directions.

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    Direction 1: carbon dioxide absorber

    One flow goes to a carbon dioxide absorber to remove the carbon dioxide. Then, an odorant is added so its presence can be detected if it leaks or if an appliance is turned on when it is not in use. Next, butane is added to give the SNG additional heating value so that it can properly burn in appliances. Finally, the SNG is channeled into the pipeline delivery system traveling through our transmission and distribution lines to homes and business along our Greater Honolulu Utility System.

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    Direction 2: hydrogen gas production plant

    The other flow of SNG is sent into the hydrogen gas production plant. The products of this plant are hydrogen and carbon dioxide gas. The hydrogen flows back into the desulfurization step that began the whole process. The left over carbon dioxide is captured and sent to a regenerator and prepared for sale to another company. The carbon dioxide eventually finds its way to Hawaii consumers in various forms including dry ice and the fizz in all carbonated drinks made in Hawaii.