System for transporting particulate solids from high temperature to low temperature zone

In a process for the production of aluminum chloride wherein chlorine and fluidized coked alumina particulate feedstock are reacted at temperatures between about 450.degree. to 800.degree. C. to form gaseous aluminum chloride and carbon oxide and wherein said alumina feedstock has an average particulate alpha alumina content of between about 0.05 and 4.5% by weight and wherein substantial portions of said alpha alumina are unreacted thereby tending to deplete volume otherwise available for chlorination reaction, the improvement wherein said unreacted particulate alpha alumina is semi-continuously removed from said process to restore said depleted reaction volume by the improved system comprising the steps of:

• (a) introducing said particulate alpha alumina into the upper portion of a downwardly extending substantially vertical inlet leg by fluidized particle transport;
• (b) moving said alumina downwardly within said inlet leg into the lower region of a first chamber separated from a second chamber by an overflow weir;
• (c) fluidizing said alumina particles within said first chamber by the action of a fluidizing gas introduced into the bottom portions of said first chamber and moving upwardly therethrough to move said fluidized alumina particles upwardly within said first chamber and overflow said weir to enter said second chamber;
• (d) fluidizing said alumina particles in said second chamber by the action of a fluidizing gas introduced into the bottom portions of said second chamber and moving upwardly therethrough, said particulate alumina within said second chamber mixing with and transferring heat by direct contact heat exchange to particulate alumina which previously entered said second chamber;
• (e) cooling said second chamber by indirect heat transfer means;
• (f) said first and second chambers being maintained at a pressure higher than that of said second zone;
• (g) maintaining said fluidizing gas in said second chamber at a higher overall gas volume flow ratio of at least 5:1;
• (h) moving said particulate alumina from said second chamber to said second zone at said lower pressure and temperature, said alumina particles being moved substantially by said fluidizing gas from said second chamber through a flow restricting means, said movement being regulated substantially by said flow restriction means in cooperation with said fluidizing gas from said second chamber flowing through said restriction means;
• (i) interrupting the flow of said particulate alumina into said first chamber by interrupting the flow thereof through said flow restriction means and substantially reducing the fluidizing gas flow into said second chamber while maintaining the fluidizing gas flow within said first chamber and into said inlet leg, said fluidizing gas passing upwardly into said first zone.

In a process wherein a fluidizable particulate solids charge comprising reactive and nonreactive portions is semi-continuously fed to a reactor and the reactive portion thereof consumed by reaction with an active gas at temperatures of over 400.degree. C. and at a given reaction pressure to produce a gaseous effluent and wherein said unreacted portion of said particulate charge remains in the reactor to deplete the same of reaction volume, the improved system for removing said unreacted particulate charge from said reactor to restore the depleted reaction volume and deliver the same to a collector at a substantially reduced temperature and pressure comprising the steps:

• (a) moving said unreacted particulate solids within said reactor to the entrance of a downwardly extending right circular cylindrical columnar inlet leg by fluidized particle transport utilizing an inactive fluidizing gas and moving said particulate solids downwardly within said columnar inlet leg into the lower region of a first chamber separated from a second chamber by a right circular cylindrical overflow weir;
• (b) fluidizing said particulate solids within said first chamber and said columnar inlet leg by the action of an inactive fluidizing gas introduced into the bottom portions of said first chamber and moving upwardly therethrough and through said leg to move said fluidized particles downwardly within said columnar leg and upwardly within said first chamber to overflow said weir and enter said second chamber;
• (c) fluidizing said particulate solids in said second chamber by the action of an inactive fluidizing gas introduced into the bottom portions of said second chamber and moving upwardly therethrough, said particulate solids within said second chamber mixing with and transferring heat by direct contact heat exchange to particulate solids which previously entered said second chamber;
• (d) said second chamber occupying the annular space between said right circular cylinder defining said first chamber and a second right circular cylinder concentric with and larger than said first chamber cylinder, the annular cross-sectional area of said second chamber in a horizontal plane being at least twice that of the circular cross-sectional area of said first chamber in the same horizontal plane;
• (e) cooling said second chamber by indirect heat transfer means applied through said larger right circular cylindrical wall;
• (f) said first and second chambers being maintained at a pressure higher than that in said reactor;
• (g) maintaining said fluidizing gas in said second chamber at a higher specific flow rate per unit cross-sectional area transverse to the gas flow than in said first chamber by a ratio of at least 11/2 times that in the first chamber and at an overall gas volume flow of at least 10 times that in said first chamber;
• (h) moving said particulate solids from said second chamber to said collector at said lower pressure and temperature, said particles being moved substantially by said fluidizing gas from said second chamber through an elongate conduit flow restricting means, said movement being regulated substantially by said flow restriction means in cooperation with said fluidizing gas from said second chamber flowing through said restriction means;
• (i) controlling the rate of particulate solids movement through said flow restricting means by increasing flow of fluidizing gas to said second chamber to reduce particulate solids rate and decreasing said gas flow to increase said particulate solids rate;
• (j) interrupting the flow of said particulate matter into said first chamber by interrupting the flow thereof through said flow restriction means and substantially interrupting the fluidizing gas flow into said second chamber while maintaining the fluidizing gas flow within said first chamber and into said columnar inlet leg, said fluidizing gas from said first chamber passing upwardly through said inlet leg into said reactor;
• (k) thereafter resuming the flow of said particulate solids by resuming the flow of fluidizing gas into said second chamber and removing the interruption to the flow through said flow restriction means.