Automatic pH control in a process for removal of hydrogen sulfide from a gas

Patent · Mon Feb 16 23:00:00 EST 1987

OSTI ID:6723816

Chang, D; Bedell, S A

A continuous process is described for removing hydrogen sulfide from a sour gaseous stream comprising: (A) contacting the sour gaseous stream in a contact zone with a first aqueous alkaline solution at a temperature below the melting point of sulfur. The solution comprises at least one polyvalent metal chelate in a higher valence state in an effective amount suitable for oxidizing substantially all the hydrogen sulfide removed from the gaseous stream to produce a sweet gaseous stream, a second aqueous alkaline solution comprising sulfur, and at least one polyvalent metal chelate in a lower valence state; (B) separating in a separation zone the sulfur from the second aqueous alkaline solution; (C) passing the second aqueous alkaline solution as an electrolyte from the separation zone to a cathode compartment of an electrochemical cell. The cell comprises an anode in an anode compartment and a cathode in the cathode compartment, the compartments separated by a cell membrane and the anode and cathode connected through an external electrical circuit; (D) producing the first aqueous alkaline solution passing the second aqueous alkaline solution from the cathode compartment to the anode compartment and oxidizing at the anode the polyvalent metal chelate to a higher valence state while producing hydrogen at the cathode and hydroxide ions in the electrolyte; and (E) recycling the first aqueous alkaline solution from the electrochemical cell to the contact zone; whereby the pH of the first aqueous alkaline solution is maintained in the contact zone at about 7 to about 9.

• Assignee: Dow Chemical Co., Midland, MI
• Patent Number(s): US 4643886
• OSTI ID: 6723816
• Country of Publication: United States
• Language: English

Related Subjects

500200* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
AIR POLLUTION CONTROL
ANODES
AQUEOUS SOLUTIONS
CATHODES
CHALCOGENIDES
CHEMICAL REACTIONS
CONTROL
DESULFURIZATION
DISPERSIONS
ELECTROCHEMICAL CELLS
ELECTRODES
ELECTROLYTES
ELECTRONIC CIRCUITS
ELEMENTS
FLUID FLOW
GAS FLOW
GASEOUS WASTES
HYDROGEN COMPOUNDS
HYDROGEN SULFIDES
MELTING POINTS
METALS
MIXTURES
NONMETALS
OXIDATION
PH VALUE
PHYSICAL PROPERTIES
POLLUTION CONTROL
RECYCLING
REMOVAL
SOLUTIONS
SULFIDES
SULFUR
SULFUR COMPOUNDS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
WASTES