Discharging powder from highpressure vessels

Claim 1

A HIGH-PRESSURE LETDOWN METHOD OF DISCHARGING PULVERULENT SOLIDS FROM A HIGH-PRESSURE ZONE WHICH CONTAINS SAID SOLIDS AND GAS INTO A LOW-PRESSURE ZONE, SAID METHOD COMPRISING: (A) FLOWING SAID PULVERULENT SOLIDS AND GAS FROM SAID HIGH-PRESSURE ZONE INTO SAID LOW-PRESSURE ZONE THROUGH A SLIT HAVING A LENGTH LONGER THAN SEVERAL TIMES ITS WIDTH, (B) DISCHARGING GAS FROM SAID HIGH-PRESSURE ZONE SEPARATELY FROM SAID FLOW THROUGH THE SLIT, (C) MONITORING THE GAS DISCHARGED IN (B) TO DETECT THE PRESENCE OF SOLIDS THEREIN AND EMITTING AN OVERRIDING SIGNAL WHEN SOLIDS ARE DETECTED THEREIN, AND (D) CONTROLLING THE WIDTH OF SAID SLIT BETWEEN SAID ZONES BY (1) MEASURING A THERMODYNAMIC PROPERTY IN SAID STREAM, SAID PROPERTY BEING RELATED TO A PRESSURE OR TEMPERATURE CHANGE IN SAID STREAM TRANSMITTING A SIGNAL RELATIVE THERETO, (2) ADJUSTING THE WIDTH OF THE SLIT RESPONSIVELY TO SAID SIGNAL, AND (3) INCREASING THE WIDTH OF SAID SLIT INDEPENDENT OF SAID FIRST SIGNAL IN RESPONSE TO SAID OVERRIDING SIGNAL.