Acid gas disposal

Abstract

Acid gas is liquified by compression and cooling, mixed with water under pressure and flowed into a disposal well.

1. The method of disposing acid gas removed from hydrocarbon products comprising the steps of:
 a) compressing the acid gas to a pressure wherein the acid gas will form a dense fluid,    b) forming a dense fluid by cooling the compressed acid gas,    c) mixing the acid gas as a dense fluid with sufficient water to form a stable mixture at injection pressure, and    d) injecting said stable mixture at injection pressure into a disposal well.    
     
     
       2. The method as defined in  claim 1  wherein said compression pressure is at least 650 psi. 
     
     
       3. The method as defined in  claim 1  wherein said water is alkaline and has a pH of at least 7.5. 
     
     
       4. The method as defined in  claim 1  wherein a minimum pressure of step a) is P min =284+21.55×CO 2 % wherein P min  is said minimum pressure in psi and CO 2 % is the percentage of carbon dioxide in the acid gas. 
     
     
       5. The method as defined in  claim 4  wherein the compressed acid gas is cooled to a temperature of below 130° F. 
     
     
       6. The method as defined in  claim 1  wherein insufficient water is a minimum of
   R H     2     O =0.25+0.10345×CO 2 %    
       wherein R H     2     O  is the minimum ratio by volume of water having at least a pH of 7.5 to the dense fluid acid gas. 
     
     
       7. The method as defined in  claim 6  wherein the mixed acid gas and water has a temperature of below 110° F. 
     
     
       8. The method as defined in  claim 1  further comprising:
 e) mixing the acid gas and water in a confluent line, and    f) maintaining the pressure in the confluent line to the compression pressure by    g) limiting the flow from the confluent line by a pressure control valve.    
     
     
       9. The method as defined in  claim 8  wherein
 h) determining that the mixture found is stable by less than a significant amount of any component of the acid gas flashing into the gas phase down stream from the control valve.    
     
     
       10. The method as defined in  claim 9  wherein determining that the amount of any component of acid gas flashed is more than a significant amount by formation of hydrates adhering on surfaces of the disposal well. 
     
     
       11. The method as defined in  claim 9  wherein determining that the amount of any component of acid gas flashed is more than a significant amount by formation of gas pockets down stream of the control valve as determined by rapid increase of pressure down stream of the control valve. 
     
     
       12. The method as defined in  claim 9  wherein less than a significant amount of any component of acid gas is flashed is determined when less the 5 percent of said mixture is flashed. 
     
     
       13. The method as defined in  claim 9  wherein less than a significant amount of any component of acid gas is flashed is determined by process simulation. 
     
     
       14. The method as defined in  claim 9  wherein less than a significant amount of any component of acid gas is flashed is determined by manual process calculations. 
     
     
       15. A system for disposing of acid gas comprising:
   a source of acid gas;        a source of water;        a series of at least one compressor and one cooler to compress and cool the acid gas to form a dense fluid acid gas;        a gas line to convey the dense fluid acid gas from its source to a confluent line;        a water line to convey the water from its source to the confluent line;        a mixer connecting the gas and water lines to the confluent line, the mixture for mixing water and acid gas into a stable mixture; and        an injection tube for injecting the stable mixture of water and acid gas of the confluent line into a disposal well.     
     
     
       16. The disposal system of  claim 15  further comprising a pressure controller in the confluent line. 
     
     
       17. The disposal system of  claim 16  wherein the pressure controller maintains the pressure at a level sufficient to prevent substantial vaporization of the mixed water and acid gas. 
     
     
       18. The disposal system of  claim 15  wherein water is continuously pumped through the injection tube to the disposal well even when no dense fluid acid gas is being disposed. 
     
     
       19. A method of injecting a liquid containing acid gas into a disposal well comprising the steps of:
   forming the liquid by mixing water and dense fluid acid gas to form a stable mixture at a pressure; and        maintaining the pressure on the liquid prior to injection at a level sufficient to prevent substantial vaporization of the liquid.     
     
     
       20. The method according to  claim 19  wherein the pressure is maintained at about  650  psi or higher. 
     
     
       21. The system according to  claim 15 , wherein the mixer comprises:
   a tee connection fluidly connecting the water and gas lines to the confluent line; and        a check valve in each of the water and gas lines to prevent backflow of the stable mixture into the gas and water lines.