Process for controlling temperature of a Claus sulfur unit thermal reactor

A process for converting hydrogen sulfide into water and elemental sulfur comprising the steps of:

• measuring the amount of hydrogen sulfide in a first hydrogen sulfide-containing stream;
• measuring the amount of molecular oxygen in a molecular oxygen-containing stream;
• introducing said first hydrogen sulfide-containing stream and said molecular oxygen-containing stream into a first reaction zone;
• maintaining said first reaction zone at conditions sufficient to oxidize said hydrogen sulfide to form a first reaction product stream containing sulfur dioxide;
• removing said first reaction product stream from said first reaction zone;
• introducing said first reaction product stream and a second hydrogen sulfide-containing stream into a second reaction zone;
• maintaining said second reaction zone at conditions sufficient to form a second reaction product stream containing water and elemental sulfur made from at least a portion of said second hydrogen sulfide-containing stream and said first reaction product stream;
• comparing said first hydrogen sulfide measurement and said first molecular oxygen measurement;
• determining the temperature within said first reaction zone;
• and
• varying the relative amount of hydrogen sulfide to molecular oxygen entering said first reaction zone in response to said temperature determination and said hydrogen sulfide-to-molecular oxygen comparison;
• whereby a temperature control strategy can be followed to maintain the temperature in said first reaction zone at a desired value.