Operation of a coal deashing process

In a coal deashing process for separating a feed mixture into a light phase and a heavy phase having fluid-like properties within a separation zone, said separation zone being maintained at an elevated temperature and at a pressure greater than 550 psig. to effect said separation, said feed mixture being formed by contacting, in a mixing zone, a feed comprising soluble coal products and insoluble coal products with a solvent maintained at an elevated temperature and pressure, said feed mixture being in a ratio by weight of solvent to feed greater than one, said solvent consisting essentially of at least one substance having a critical temperature below 800 degrees F. selected from the group consisting of aromatic hydrocarbons having a single benzene nucleus and normal boiling points below about 310 degrees F., cycloparaffin hydrocarbons having normal boiling points below about 310 degrees F., open chain mono-olefin hydrocarbons having normal boiling points below about 310 degrees F., open chain saturated hydrocarbons having normal boiling points below about 310 degrees F., mono-, di, and tri-open chain amines containing from about 2-8 carbon atoms, carbocyclic amines having a monocyclic structure containing from about 6-9 carbon atoms, hererocyclic amines containing from about 5-9 carbon atoms, and phenols containing from about 6-9 carbon atoms and their homologs, said feed mixture being introduced into said separation zone through an entry conduit and separated in said separation zone into said light phase and said heavy phase, and said light phase and said heavy phase are withdrawn through a light phase withdrawal conduit and a heavy phase withdrawal conduit, respectively, from said separation zone, the improvements which comprise, during periods in which flow of said feed to said mixing zone is interrupted:

• (a) providing an alternate solvent flow path by which the flow of said solvent maintained at elevated temperature and pressure is diverted from said mixing zone during said periods in which flow of said feed to said mixing zone is interrupted, and maintaining fluid communication through said light phase withdrawal conduit between said diverted solvent and said separated phases in said separation zone to maintain said elevated pressure level within said separation zone;
• (b) providing means for blocking said feed mixture entry conduit to said separation zone to assist in maintaining said elevated pressure within said separation zone;
• (c) providing means for blocking said heavy phase withdrawal conduit to assist in maintaining said elevated pressure within said separation zone;
• and
• (d) maintaining the temperature level of said separation zone at the elevated temperature level at which said separation is effected while also maintaining said elevated pressure level to maintain the fluid-like properties of said heavy phase.