Concentration measuring apparatus for hydrogen sulfide in gas flow, and method for determining sulfide ion

A measuring apparatus that measures a concentration of gaseous hydrogen sulfide in a gas flow, the measuring apparatus comprising:

• an absorbing liquid that can absorb gaseous hydrogen sulfide as sulfide ion, the absorbing liquid being an alkaline solution;
• a hollow fiber membrane module comprising a plurality of hollow fiber membranes, an inlet and an outlet for the gas flow provided on the shell side of the hollow fiber membrane module, and a liquid introducing end and a liquid discharging end for the absorbing liquid provided on the tube side of the hollow fiber membrane module, the hollow fiber membrane module contacting the gas flow with a flow of the absorbing liquid through membranes of the plurality of hollow fiber membranes, so that the absorbing liquid absorbs at least part of gaseous hydrogen sulfide in the gas flow as sulfide ion;
• an absorbing liquid feeder that feeds the absorbing liquid to the liquid introducing end of the hollow fiber membrane module;
• an oxidizer that exothermically reacts with sulfide ion;
• an oxidizer feeder that feeds the oxidizer to the absorbing liquid;
• a first thermometer that measures a temperature of the absorbing liquid before the sulfide ion that the absorbing liquid has absorbed exothermically reacts with the oxidizer;
• a second thermometer that measures the temperature of the absorbing liquid after the sulfide ion that the absorbing liquid has absorbed exothermically reacts with the oxidizer;
• and
• an alkali trap connected to the outlet for the gas flow,
• wherein the oxidizer feeder feeds the oxidizer to the absorbing liquid after the absorbing liquid absorbs the at least part of the gaseous hydrogen sulfide.