Feed Injection System

The addition point of gaseous fuels requires careful consideration to avoid homogeneous reactions upstream of the reformer vith autothermal reforming and partial oxidation. Commercial flame arresters are normally not capable of operating under the elevated temperatures of the fuel processor. Microchannels are known to act as flame arresters (see Section 6.3.2) and may be inserted into the tubing system to avoid uncontrolled reaction of the fuel/air mixture. For liquid fuels, which are usually injected into the pre-heated steam feed or even into the air/steam feed mixture, either cooled injection nozzles [567] or the application of steam jackets may be used to ensure stable operation of the nozzle. 

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Feed injection. An improved feed injection system provides optimum atomization and distribution of the feed for rapid mixing and complete vaporization. The benefits of improved feed injection aie reduced coke deposition, reduced dry gas yield, and improved gasoline yield. 

Important features of a feed injection system include ... 

The choice of the feed injection system should be based on the vendor s experience in similar units with similar feeds and on his yield projection and/or performance guarantee. However, it may be difficult to substantiate the guarantee when other changes are being made in the unit. 

This chapter provided several cost recommendations that, once implemented, would provide cost-effective added value to the operation of the FCC. Examples of such items include tips on debottlenecking the air blower, wet gas compressor, and catalyst circulation. This chapter also discussed the latest technologies regarding the riser termination devices, as well as feed injection systems. Prior to implementing any new technologies, it is critical that the objectives and the limitations of the unit are clearly defined to ensure the expected benefits of the new technology are realized. 

The proper choice of a feed injection system, regenerator, and catalyst are some of the key aspects of successful RFCC operation. 

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. 

Consider the example in Fig. 26 of determining if there is a problem with the feed injection system of a fluidized catalytic cracking unit (Ramesh et al., 1992). In this example, there is a set of rules that relate combinations of process observations to establish or reject this possibility. 

The label of interest is Feed Injection System Problem. The if, and, and or statements relate specific process observations that can establish that there is a likelihood of an injection system problem. Injector header pressure is a process measurement and abnormal is an intermediate label of interest. The label abnormal can be determined by developing a numeric-symbolic interpreter that maps injector header pressure data as either normal or abnormal. 

Unit modifications that can improve the operation start with the riser and the feed injection system [6,7], The riser should be straight and have the desired velocities at both ends, which reduces excessive slip at the bottom and excessive erosion and turbulence at the outlet. A reduced diameter section is normally included at the lower end of the riser, just above the feed nozzles, to accelerate the feed/catalyst mixture. This improves contacting between the catalyst and hydrocarbons and minimizes back mixing of the catalyst. 

Feed nozzles can be upgraded or replaced with a modern system. An axial nozzle can be replaced with a radial feed injection system, additional nozzles can be added... 

The benefits of an improved feed injection system and riser can be lower delta coke, lower regenerator temperature, higher conversion, higher gasoline yield, and increased liquid yield. More feed can be processed and an air blower or wet gas compressor limitation can be relieved. 

The precursors for the formation of heavy polymer and coke deposits are initially formed as a result of an ineffective or damaged feed injection system. Loss of pressure drop across the injector nozzle(s) is an indication the flow has been lost an increase in pressure drop indicates a plugged nozzle. In either case, the catalyst to... 

Heating the feed to reactor temperature, usually greater than 500 C, causes an additional problem. Coke is formed by thermal reactions of the feed in the preheater and feed injection system. The coking tendency is more severe for heavy feedstocks which have higher concentrations of coke precursors. This can be avoided by limiting the feed temperature to 300 C or less. 

R FUJIDIZEI) UED REGENERATOR PI PRESSURE GAUGE FI FEED INJECTION SYSTEM R1.R2 RORTOMETERS D DISTRIBUTOR S CATALYST SAMPLING POINT H3 FEED PREHEAT TCI TO TC6 THERMOCOUPLES E FLUE GAS LINE III GAS PREHEAT VI THREE WAY VALVE... 

In the operation of a filtration system, the filter is first precoated by circulating a mixture of filter aid and clear or filtered liquid from the precoat tank through the filter and back to the precoat tank. This is continued until all the filter aid is deposited on the filter. The body feed injection system is then started and the filter is changed over, with minimum fluctuations in pressure, from precoating to filtering. 

Figure 14.3 Different feed injection systems (a) first generation [42], (Source Nilsson et al. [42], Reproduced with permission of Elsevier.) (b) improved injection system without redrculation zone [43].

The second component of the feed injection system is the design of the low riser transition prior to feed injection. There are two common configurations of the lower riser to prepare for feed injection one is bottom entry and the other is side entry configura-... 

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