Process and apparatus for automated regulation of sulphur production units

Abstract

A process for automated regulation of a unit producing sulphur by oxidation of hydrogen sulphide, in which the flow of gas carrying oxygen into the unit is regulated so as to keep an operating parameter, based on measurement of the sulphurous compound of the residual gases, level with a reference value. It is characterized by the fact that the control signal, used to regulate the flow of gas containing oxygen at the unit inlet, is a combination of a signal based on measurements taken at the inlet, and representing the theoretical flow of this gas needed to keep the operating parameter at its reference level and another signal representing the correction needed in this flow to adjust the instantaneous value of the parameter to the reference level. This process allow better control of the sulphur unit, with increased efficiency and reduced atmospheric pollution. PROCESS FOR AUTOMATED REGULATION OF SULPHUR PRODUCTION UNITS

What is claimed is: 
     
       1. A device for the automatic regulation of a sulphur unit that produces sulphur by the oxidation of a hydrogen sulphide-containing gas by means of a free oxygen-containing gas, said gases being fed to the inlet of the sulphur unit through suitable inlet pipes and said sulphur unit liberating residual gases containing H 2  S and SO 2  through a residual gas pipe, said device comprising: a first analyzer for automatically analyzing the H 2  S-containing gas fed to the inlet of the sulphur unit for providing a signal representative of the H 2  S content of said gas,   a first calculator connected to receive the signal provided by said first analyzer for computing the theoretical flow of free oxygen-containing gas to be fed to the inlet of the sulphur unit to keep the H 2  S : SO 2  molar ratio in the residual gases to a set value and for providing an output signal representative of said theoretical flow,   sampling means for continuously taking samples of the residual gases,   a second analyzer for automatically analyzing said samples for providing signals representative of the H 2  S and SO 2  contents of the residual gases,   a second calculator connected to receive the signals from the second analyzer for computing the instantaneous H 2  S : SO 2  molar ratio in the residual gases and for computing a correction value representing the correction needed in the flow of free oxygen-containing gases to the inlet of the sulfur unit to adjust said instantaneous ratio to the set value, said second calculator providing a signal representative of said correction value,   means for electronically combining the signals provided by said first and second calculators to produce a resulting signal representing their sum, and means responsive to said resulting signal for automatically controlling the flow of free oxygen-containing gas to the inlet of the sulphur unit.   
     
     
       2. A device as recited in claim 1 wherein said controlling means comprises: a valve connected to the inlet pipe carrying said free oxygen-containing gas, and   a servomechanism responsive to said resulting signal for controlling said valve.   
     
     
       3. A device as recited in claim 2 wherein said free oxygen-containing gas is fed to said sulphur unit by a first main pipe and a second, smaller capacity pipe and wherein said valve is connected to said second pipe for controlling the flow of free oxygen-containing gas into said sulphur unit. 
     
     
       4. A device as recited in claim 1 further comprising sensing means connected to the inlet pipes of the H 2  S-containing gas and the free oxygen-containing gas to measure flow-rate, pressure, and temperature of the H 2  S-containing gas and flow-rate, pressure, temperature, and humidity of the free oxygen-containing gas, said sensing means providing signals representative of said measurements to said first calculator. 
     
     
       5. A device as recited in claim 1 in which said first analyzer comprises a chromatography apparatus. 
     
     
       6. A device as recited in claim 1 wherein said sampling means comprises a sampling tube having an aperture along one generatrix projecting into the residual gas pipe and leading into a circuit through which the sample flows, said device further comprising heating means for maintaining the temperature of said sampling tube and circuit above the solidifying temperature of sulphur. 
     
     
       7. A device as recited in claim 1 wherein the second analyzer comprises a chromatography apparatus having a chromatographic column and equipped with a sample input device separate from the chromatographic column, a storage system for storing the peaks detected, and a programmer. 
     
     
       8. A device as recited in claim 7 wherein the sample-input device comprises an adjustable inlet-tap placed in a heated, insulated enclosure, the temperature of said enclosure being maintained above the solidifying temperature of sulphur. 
     
     
       9. A device as recited in claim 1 in which said second calculator comprises: a device for calculating the instantaneous valve of the H 2  S : SO 2  molar ratio in the residual gases from the signals supplied by said second analyzer,   filtering means for providing signals representative of the average value of said molar ratio, and means for computing said correction signal from the average value signal and a signal representing the set value of said H 2  S : SO 2  molar ratio.   
     
     
       10. A device as recited in claim 1 further including a system to calculate the rate of conversion of the hydrogen sulphide into sulphur from the signals provided by said first and second analyzers and to provide a signal representing said rate of conversion.