Feed nozzles

Sketch the vessel. For height above center line of feed nozzle to top seam, use 36" -f h feed nozzle OD or 48" minimum. For distance below center line of feed nozzle to maximum liquid level, use 12" + V feed nozzle OD or 18" minimum. 

The angle of repose is defined as the angle between a line of repose of loose material and a horizontal plane. Its value depends on the magnitude of friction and adhesion between particles and determines the mobility of loose solids, which is a critical parameter in designing conical discharge and feeding nozzles and in... 

The relation is solved for Sr/Sj. The results are not exact, because the feed tray composition is very seldom the same as the feed which is the assumption in this relation. Actually, the feed point or correct location for the feed may be off by two or three theoretical trays. This will vary with the system. It does mean, however, that when this approach is used for feed plate location, alternate feed nozzles should be installed on the column to allow for experimental location of the best feed point. These extra nozzles are usually placed on alternate trays (or more) both above and below the calculated location. A minimum of three alternate nozzles should be available. 

Feed nozzles should be located on trays Nos. 21, 23, and 25 counting up from the bottom tray as No. 1. 

Provide at least three, and perhaps four feed nozzles in addition to the one theoretically calculated to be the optimum location. Select these feed locations approximately two and four trays above and below the design basis or theoretical location. These extra nozzles must be oriented on the column so they have proper feed entry spargers or distributors (entry can be onto the tray or into the downcomer) and can be valved from a feed manifold to select the alternate desired location for testing purposes. 

The sources of steam in the reactor vapor are lift steam to the standpipe, atomization steam to the feed nozzles, dome steam, and stripping steam. Some units may have other streams and the feed may contain water. Depending on the reactor pressure, approximately 25% to 50% of the stripping steam is entrained with the spent catalyst flowing to the regenerator, which should be deducted. 

To maximize the benefits of feed nozzles, the regenerated catalyst must be distributed evenly throughout the cross-section of the ri . ... 

Process and Mechanical Design Criteria for FCC Feed Nozzles... 

Feed nozzle type Insert material Nozzle tip... 

This requires pre-accelerating the catalyst to the feed zone. Steam or fuel gas is often used to lift the catalyst to the feed injection. Figure 7-1 shows the design criteria of using steam as a lift media to deliver a dense supply of catalyst to the feed nozzles. 

The pressure drop in the Y or J-bend section could be from improper fluidization or a flaw in the mechanical design. There are often fluffing gas distributors in the bottom of the Y or along the J-bend that are designed to promote uniform delivery of the cataly.st into the feed nozzles. Mechanical damage to these distributors or too little or too much fluffing gas affect the catalyst density, causing pressure head downstream of the slide valve. 

A low reactor temperature may not fully vaporize the feed unvaporized feed droplets will aggregate to form coke around the feed nozzles on the reactor walls and/or the transfer line. A long residence time in the reactor and transfer line also accelerate coke buildup. 

Damaged or partially plugged feed nozzles can contribute to coke formation due to poor feed atomization. 

Damaged or partially plugged Feed Nozzles Loss of the Shed decks Feed leaking through Bottoms exchangers or Feed Diversion Valve... 

Install high efficiency feed nozzles Use 1 or larger tube diameter Keep C7 insoiubies in Slurry System less than 5% wt Use U-tube for Bottoms Exch. Draw more Bottoms Product Have a spare Bottoms Exchanger bundle... 

Maintain a mitrimum of 1 PSi pressure differential across the Slide Valves Install "Radial designed Feed Nozzles Install an automated shutdown System... 

Feedstock A higher fraction of 1,050°F+ (565°C+) in the feed. For many refiners, the regenerator temperature is the limit on addition of heavy ends to the feed. High-efficiency feed nozzles can be used. Naphtha quench can be added. 

Install high efficiency Feed Nozzles Lower Preheat Temperature Inject Naphtha Quench to Riser Increase Stripping and Dispersion Steam Switch to a Coke Selective Catalyst... 

Damaged or plugged feed nozzles Damaged Stripper Steam Distributor... 

Check pressure profile around Feed Nozzles Track in Coke Survey the Stripper... 

Damaged or plugged feed nozzle(s) and/or damaged stripping steam distributor(s) are the common causes of mechanical failures that affect true conversion. Note that the apparent conversion, as discussed in Chapter 5, is affected by the distillation cut point and main column operations. 

Perform a single-gauge pressure survey around the feed nozzles. Calculate the hydrogen content of the spent catalyst. Conduct a... 

Calibrate the reactor temperature controller. Conduct a pressure survey around the feed nozzle piping to verify its mechanical integrity. 

The main mechanical conditions that affect octane are the type and condition of the feed nozzles. Low-efficiency feed nozzles actually increase the gasoline octane due to promotion of thermal reactions in the mix zone. High-efficiency feed nozzles improve feed/catalyst mixing and increase the gasoline yield, but decrease gasoline octane. 

Check the conditions of the feed nozzles and amount of atomizing steam. 

Radial feed nozzles also minimize the possibility of a reversal. New valve actuators can operate more quickly and reliably, also increasing the safety factor. 

Adding a catalyst cooler may back a boiler down, or it may require more BFW and a home for the steam. New feed nozzles may require more steam. A cogeneration unit can be an attractive option. 

An efficient feed injection system produces extremely small droplets that vaporize quickly. Rapid vaporization minimizes the amount of non-vaporized hydrocarbons that block the active sites. An effective feed nozzle system must instantaneously vaporize and crack asphaltenes and polynuclear aromatics to lower boiling entities. 

Fig 1. Schematic diagram of the ICFB gasifier. 1. steam generator, 2. flowmeter, 3. orifice flowmeter, 4. air preheater, 5, gas plenum, 6. draft tube, 7. orifice, 8. gas separator, 9. freeboard, 10. screw feeder, 11. mono-pump, 12. sludge feed nozzle, 13. cyclone, 14. condenser, 15. collector, 16. filter, 17. ID fan. 

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