Pressure diffuser having gas vent for cooking liquor

Abstract

A pressure diffuser is disclosed having a pressurized vessel having an inlet adapted to receive a slurry of cellulosic fibrous material and cooking liquor; an outer chamber having an assembly of screens, wherein the slurry flows through the outer chamber and a portion of the cooking liquor is extracted through the screens; a center chamber to receive cooking liquor extracted through the screens; an inner head capping the center chamber, wherein the inner head is impervious to gases escaping from the cooking liquor and collecting underneath the inner head, and a gas exhaust conduit extending from the inner head to an outlet external of the pressure diffuser, wherein the conduit has an inlet below the inner head.

We claim:  
     
         1 . A pressure diffuser comprising: 
 a pressurized vessel having an inlet adapted to receive a slurry of cellulosic fibrous material and cooking liquor;    an outer chamber having an assembly of screens, wherein the slurry flows through the outer chamber and a portion of the cooking liquor is extracted through the screens;    a center chamber to receive the cooking liquor extracted through the screens;    an inner head capping the center chamber, wherein the inner head is impervious to gases escaping from the cooking liquor and collecting in a gas pocket underneath the inner head,    and a gas exhaust conduit extending from the inner head to an outlet external of the pressure diffuser, wherein the conduit has an inlet in the gas pocket below the inner head.    
     
     
         2 . A pressure diffuser as in  claim 1  wherein the inlet to the conduit is adjacent a lower surface of an apex to the inner head.  
     
     
         3 . A pressure diffuser as in  claim 1  wherein the inner head is conical and the inlet to the conduit is adjacent an apex of the inner head.  
     
     
         4 . A pressure diffuser as in  claim 1  further comprising a valve in the conduit and the valve is automatically actuated when gas is at the inlet of the conduit.  
     
     
         5 . A pressure diffuser as in  claim 1  further comprising a valve and a valve actuator sensing gases at the inlet to the conduit.  
     
     
         6 . A pressure diffuser as in  claim 1  wherein said conduit includes a downwardly extending section between the inlet and an aperture in the inner head for the conduit, wherein the aperture is below a gas pocket level in the inner head.  
     
     
         7 . A pressure diffuser as in  claim 1  wherein the gas exhaust conduit extends down through a top of the diffuser and wherein the inlet comprises a funnel inlet.  
     
     
         8 . A method for venting gases from a pressure diffuser vessel having an outer chamber with an assembly of screens and a center chamber with an upper gas containing region, said method comprising: 
 pressurizing the vessel and feeding into the vessel a slurry of cellulosic fibrous material and cooking liquor;    from the slurry in the outer chamber, extracting at least a portion of the cooking liquor through the assembly of screens and introducing the extracted liquor into the center chamber;    partially filling the center chamber with the extracted cooking liquor;    collecting gases from the cooking liquor in a gas pocket at an upper region of the center chamber, and    venting gases from the gas pocket through a gas exhaust conduit having an inlet positioned in the gas pocket and an outlet external of the pressure diffuser vessel.    
     
     
         9 . A method as in  claim 8  wherein the outlet of the a gas exhaust conduit extends downward from the gas pocket and into a liquid filled portion of the center chamber before the conduit extends through a wall of the center chamber.  
     
     
         10 . A method as in  claim 8  wherein the conduit includes a valve and the method further comprises automatically actuating the valve when gas detected at the inlet of the conduit.  
     
     
         11 . A method as in  claim 8  wherein the conduit includes a valve and the method further comprises automatically actuating the valve when gas is detected in the gas pocket.  
     
     
         12 . A method as in  claim 8  wherein the conduit includes a valve and the method further comprises automatically actuating the valve on a predetermined periodic basis.  
     
     
         13 . A method as in  claim 8  wherein the conduit includes a valve and the method further comprises automatically closing the valve when liquid is detected at the inlet of the conduit.  
     
     
         14 . A method as in  claim 8  further comprising outputting the cooking liquor from the central chamber to a filtration tank, wherein the filtration tank has a small interior volume insufficient to contain a large gas volume.