Method and apparatus for retorting oil shale at subatmospheric pressure

摘要

In a process for retorting oil shale in an situ oil shale retort having a tunnel adjacent the retort, off gas is produced. Leakage of the off gas into the tunnel is prevented by withdrawing off gas from the retort at a rate sufficient to reduce the pressure in the retort adjacent the tunnel to a pressure below the ambient pressure within the tunnel.