Trickle valve

There are many processes in the petroleum refinery and other chemical process areas which utilize equipment for separating fine solid particles from a fluidizing or other gas and for separating fine solid particles from larger particles. One example of such a process is the fluid catalytic cracking (FCC) process, for producing primarily liquid petroleum fuel products from heavy gas oils. The desire reaction takes place when preheated gas oil feed is brought into contact with a hot cracking catalyst which is in the form of a fine powder, typically having a particle size of from about 10-200 microns, usually a mean particle size of about 70-100 microns. The catalyst particles are typically contacted with the hydrocarbon feedstock in a dilute phase fluidized bed as the reaction zone. The effluent of the reaction zone is a mixture of a cracked vapor product and coked catalyst particles. The coked catalyst particles are separated from cracked vapor product by means of two or more cyclone separators in series. The first cyclone separator is generally referred to as the primary cyclone. The gaseous effluent of the primary cyclone is typically fed to a so-called secondary cyclone in which the cracked vapor is further separated from the coked catalyst. The catalyst may be separated from the effluent of a reactor zone by means of more than one combination of primary and secondary cyclones operating in parallel. The separated coked catalyst particles are fed into a stripping zone via diplegs protruding down from the primary and secondary cyclones. The stripping zone is typically a dense fluidized bed to which a stripping medium is supplied to as fluidizing means. The stripped catalyst particles are then sent to a regenerating zone in which the coke is burned off with an oxygen-containing gas, typically air, to form regenerated catalyst particles. The regenerated catalyst is returned to the reactor zone where they contact fresh feed. An apparatus comprising a trickle valve positioned at the lower end of a vertical dipleg of a gas-solids separator comprising a pair of co-operable clamshell doors arranged in such a manner that mutual opposite swinging movement between a closed position wherein the doors adjoin along a midline, and an open position wherein the doors swing outwardly around a horizontal axis of rotation, is possible, and wherein either clamshell door is provided with means to press the doors together towards a closed position and at least one clamshell doo