Low emission dry gas seal system for compressors

Abstract

Systems and methods according to these exemplary embodiments provide sealing mechanisms for centrifugal compressors. A sealing mechanism includes first, second and third dry gas seals arranged in series. Each seal receives its own sealing gas and has its own venting mechanism. Sealing gas pressures remain low enough that a dedicated compressor for supplying the sealing gases is not needed. Additionally, the risk of process gas being released into the atmosphere in case of seal failure is limited.

What is claimed is: 
     
         1 . A turbo machine comprising:
 a rotor assembly including at least one impeller;   a bearing connected to, and for rotatably supporting, the rotor assembly;   a stator; and   a sealing mechanism disposed between the rotor assembly and the bearing, said sealing mechanism including:   a first dry gas seal, disposed proximate an inboard side of said sealing mechanism, and having a primary seal gas supplied thereto at a first pressure;   a second dry gas seal, disposed adjacent to said first dry gas seal and having a primary buffer gas supplied thereto at a second pressure; and   a third dry gas seal, disposed adjacent to said second dry gas seal and having a buffer gas supplied thereto at a third pressure.   
     
     
         2 . The turbo machine of  claim 1 , wherein said primary seal gas is a process gas which is being pressurized by said turbo machine, said primary buffer gas is fuel gas, and said buffer gas is nitrogen. 
     
     
         3 . The turbo machine of  claim 1 , further comprising:
 a first venting mechanism which is configured to vent primary seal gas which is recovered downstream of said first dry gas seal to a recovery system within said turbo machine;   a second venting mechanism which is configured to vent primary buffer gas and buffer gas which is recovered downstream of said second dry gas seal to a flare associated with said turbo machine; and   a third venting mechanism which is configured to vent buffer gas which is recovered downstream of said third dry gas seal into the atmosphere.   
     
     
         4 . The turbo machine of  claim 1 , wherein a first pressure zone associated with said process gas coming from said turbo machine has a pressure P 1 , a second pressure zone disposed between said first pressure zone and said first dry gas seal has a pressure P 2 , a third pressure zone disposed within said first dry gas seal has a pressure P 3 , a fourth pressure zone disposed between said third pressure zone and said second dry gas seal has a pressure P 4 , a fifth pressure zone disposed within said second dry gas seal has a pressure P 5 , a sixth pressure zone disposed between said fifth pressure zone and said third dry gas seal has a pressure P 6 , a seventh pressure zone disposed within said third dry gas seal has a pressure P 7 , and P 1 >P 2 >P 4 >P 3 >P 6 >P 5 >P 7 . 
     
     
         5 . A method for sealing a turbo machine having a rotor assembly including at least one impeller, a bearing connected to, and for rotatably supporting, the rotor assembly, and a stator, the method comprising:
 blocking a process gas, which is pressurized by said turbo machine, from reaching said bearing by using a combination of first, second and third dry gas seals in sequence;   supplying said first dry gas seal with a primary seal gas at a first pressure;   supplying said second dry gas seal, disposed adjacent to said first dry gas seal, with a primary buffer gas at a second pressure; and   supplying said third dry gas seal, disposed adjacent to said second dry gas seal, with a buffer gas at a third pressure.   
     
     
         6 . The method of  claim 5 , wherein said primary seal gas is a conditioned process gas, said primary buffer gas is fuel gas, and said buffer gas is nitrogen. 
     
     
         7 . A dry gas sealing control system comprising:
 a first sealing gas input control mechanism which is configured to provide a first sealing gas to a first dry gas seal at a first pressure;   a second sealing gas input control mechanism which is configured to provide a second sealing gas to a second dry gas seal at a second pressure; and   a third sealing gas input control mechanism which is configured to provide a third sealing gas to a third dry gas seal at a third pressure, wherein said first, second and third sealing gases are different from one another.   
     
     
         8 . The dry gas sealing control system of  claim 7 , wherein said first sealing gas is a process gas, said second sealing gas is fuel gas, and said third sealing gas is nitrogen. 
     
     
         9 . The dry gas sealing control system of  claim 7 , wherein each of said first, second and third pressures is less than 51 Bar. 
     
     
         10 . The dry gas sealing control system of  claim 7 , further comprising at least one gas conditioning element associated with said first sealing gas input control mechanism to perform at least one of heating, cooling and filtering of said first sealing gas.