Fluidized bed reactor with residence time control

WHAT IS CLAIMED IS: 1. A catalytic reactor for the catalytic conversion of a feed stream by contact with fluidized catalyst particles to produce a product stream, the reactor comprising : a reaction section defining a catalytic reaction zone and a feed inlet communicating with the reaction zone; a separation section for separating gaseous products from fluidized catalyst particles, the separation section defining a particle outlet for discharging fluidized catalyst particles and the separation section defining a gas recovery outlet for withdrawing the gaseous products from the separation section;STDC0591 a disengaging conduit extending from the reaction section to the separation section, in fluid communication with the reaction zone, for conducting the product stream and fluidized catalyst particles and defining a discharge opening for discharging the product stream and fluidized catalyst particles; at least one catalyst circulation pipe for conveying fluidized catalyst particles to the reaction section; means for controlling the rate at which catalyst particles are added to the reactor section; a first feed conduit for adding feed to the catalytic reaction zone at a first elevation;STDC0324 and means to achieve a desired reaction residence time by varying the effect of space velocity directly through adjustment of the catalyst circulation or the adjustment of the distance for catalyst and feed contact by use of at one additional feed conduit to add at least a portion of the feed above the first elevation.

2. The reactor of claim 1 wherein the first feed conduit and the at least one additional feed conduit provide at least part of a plurality of feed distributors at different elevations in the reactor section; and

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a plurality of feed control valves govern the flow of feed to each of the distributors and each of the feed control valves is dedicated to less than all of the plurality of feed distributors to separately govern the flow of feed to the plurality of feed distributors.

3. The catalytic reactor of claim 2 wherein each of the control valves is dedicated to only one of the feed distributors.

4. The catalytic reactor of any of claims 1 to 3 wherein the reaction section further comprises a catalyst mixing zone below the reaction zone in fluid communication with the circulation pipe.

5. The catalytic reactor of claim 4 including a catalyst control valve on the circulation pipe for controlling the rate at which catalyst particles are added to the reaction section and a pressure differential indicator with sensors at two elevations in the reaction section is linked to the catalyst control valve.

6. The catalytic reactor of claim 5 wherein the catalyst circulation pipe is in communication with the separation section and an additional catalyst circulation pipe with one end in communication with a catalyst regenerator has a control valve governed by the temperature in the reactor section.

7. The catalyst reactor of any of claims 1 to 3 wherein the reaction section comprises a plurality of discrete reactor sections with each defined at least in part by one of the distribution pipes and a reactant feed line is in communication with each reactor section through one of the feed control valves to separately regulate feed to each reactor section..

8. A process of catalytically reacting a reactant stream comprising a feed by contacting it with catalyst particles for a controlled residence time, the process comprising:

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delivering catalyst particles to a reaction section at a catalyst circulation rate to provide a catalyst flux sufficient to provide a catalyst density in the reaction section upon fluidization with the flux preferably between 15 and 1100 kg/m2 and the density preferably between 48 and 320 kg/m3 ; distributing a reactant stream to the reaction section at at least one location and at a rate sufficient to fluidize the catalyst particles and contact the reactant stream with catalyst particles preferably at a superficial velocity of 1 m/s to 9 m/s to;STDC0418 catalyzing the conversion of the reactants in a catalytic reaction zone to a product stream; adjusting the residence time at a selected space velocity by changing the effective volume of the catalytic reaction section or adjusting the catalyst circulation rate in response to a measured pressure drop in the the reaction section; and withdrawing catalyst particles and the product stream from the reaction section.

9. The process of claim 8 wherein the effective volume of a catalytic reaction zone in the reaction section is changed by introducing feed into the reaction zone at more than one elevation to form reactor subsections and the number of subsections receiving feed is increased or decreased.

10. The process of claim 8 wherein the volume of the catalytic reaction section is changed by changing the flow rate of a minimally reactive diluent into the catalytic reaction section.

11. The process of claim 8 wherein the volume of the catalytic reaction section is changed by changing a cross-sectional area of a catalytic reaction section in the reaction section.

12. The process of claim 8 wherein an additional catalyst circulation rate of regenerated catalyst particles to the reaction section is controlled in response to a temperature in the reaction section.