FCC-air system

Figure 56 compares the computed results for the FCC/air system against those for the glass/water system, to illustrate the disparate behaviors of G/S and L/S fluidization. 

The lowest two insets of Fig. 56 compares the power for suspending and transporting the solid particles NST for the G/S and L/S systems. For the FCC/air system, NST is always less than the total energy TV, until it jumps to the latter value at the point of sudden change, while for glass/water, NST is always the same as TV in view of its homogeneous nature. 

Figure 9 Variation of Nst with c and f for the FCC-air system (Gs = 50 kg/(m2 s)). Two minimum points in blue correspond to the dilute and the dense flow, respectively, and their coexistence corresponds to the choking state of fluidization (Ge and Li, 2002).

Pattern—constitution of regime spectrum dependent on material properties bubbling/transport for coarse G/S systems particulate/bubbling/turbulent/ fast/transport for FCC catalyst/air systems particulate only for most L/S systems. 

For instance, if the solids flow rate is specified at Gs = 50 kg/(m2s), choking will take place at Ug = 3.21 m/s for system FCC/air as indicated in the figure. Throughout the entire regime spectrum, only at this unique point (l/pl, K ) can both dense-phase fluidization and dilute-phase transport coexist. At velocities higher than Upt, only dilute transport can exist, shown as Mode FD in Fig. 4 at velocities lower than l/pt, only dense-phase fluidization can take place, shown as Mode PFC in Fig. 4. The transition point at l/pt identifies the unique Mode PFC/FD on the curve of Fig. 5 for the coexistence of both modes, the relative proportion of which depends on other external conditions such as the imposed pressure APimp as reported by Weinstein et al. (1983). 

Figure 7 shows the dependence of axial voidage profiles on solids inventory, which was first recognized by Weinstein et al. (1983), for system FCC/air (pp = 1,450 kg/m3, dp = 59 /im). Two kinds of voidage profile curves are shown. The curves for / = 15, 20 kg in Fig. 7a and / = 15, 20, 22 kg in Fig. 7b are S-shaped, with the co-existence of two regions, and transition occurring inside the unit, while solids can be fed at the bottom of the bed at saturation flow rates. Variation of solids inventory / does not result in any change of... 

Fig. 7. Axial voidage profiles for system FCC/air. ( ) Data used in Fig. 5.

Figure 12 shows the computed results for the local hydrodynamic states of the system FCC/air to illustrate the change of the status parameters with gas flow rate Ug for two solids rates Gs = 50 and 75 kg/(m2s). 

Fig. 12. Computational results of changes of parameters with Ux (system FCC/air).

Figure 25 Generalized fluidization diagram with EMMS drag coefficient (air-FCC particle system, dp = 75(im, />p=1500 kg/m />g=1.3kg/m //g=1.8x 10 Pa s, Ut=0.2184 m/s) (Ullah et al, 2013b).

Step 1. Selection of normal operating conditions for the regenerator system. This sets normal air blower flow and head, and expander flow and head. If the proposed installation is being designed for an existing FCC unit, only a... 

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. 

FCC feed, sulfur compounds in, 11 716 FCC unit emissions, 11 714 controlling, 11 689-694 FCC unit regenerators, 11 713 air distribution systems in, 11 726 catalyst emissions from, 11 714—715 CO2 emissions from, 11 720—721 configuration and mechanical hardware in, 11 722-731 cyclones in, 11 726-728 design of, 11 722-723 flue gas handling in, 11 729 fluidization in, 11 723-725 nitrogen oxide emissions from,... 

Figure 13 The apparent flow regime diagram calculated with EMMS-based multiscale CFD and the intrinsic flow regime diagram for the air-FCC system (fluid catalytic cracking particle, dp = 54 m, pp = 930 kg/m3) calculated by using the EMMS model without CFD. The intrinsic flow regime diagram is independent of the riser height (Wang et al., 2008).

The fluidized reactor system is similar to that of a refineiy FCC unit and consists of riser reactor, regenerator vessel, air compression, catalyst handling, flue-gas handling and feed and effluent heat recovery. Using this reactor system with continuous catalyst regeneration allows higher operating temperatures than with fixed-bed reactors so that paraffins, as well as olefins, are converted. The conversion of paraffins allows substantial quantities of paraffins in the feedstream and recycle of unconverted feed without need to separate olefins and paraffins. 

Description The DCC process overcame the limitations of conventional fluid catalytic cracking (FCC) processes. The propylene yield of DCC is 3-5 times that of conventional FCC processes. The processing scheme of DCC is similar to that of a conventional FCC unit consisting of reaction-regeneration, fractionation and gas concentration sections. The feedstock, dispersed with steam, is fed to the system and contacted with the hot regenerated catalyst either in a riser-plus fluidized dense-bed reactor (for DCC-I) or in a riser reactor (for DCC-II). The feed is catalytically cracked. Reactor effluent proceeds to the fractionation and gas concentration sections for stream separation and further recovery. The coke-deposited catalyst is stripped with steam and transferred to a regenerator where air is introduced and coke on the catalyst is removed by combustion. The hot regenerated catalyst is returned to the reactor at a controlled circulation rate to achieve the heat balance for the system. 

What about integrating these two turbines The idea is to make better use of the steam turbine helper for start up in the PRT live-box train design in Figure 11.20. In other words, the steam turbine helper becomes a letdown turbine and the normal FCC process steam can be routed through this letdown turbine. Thus, the letdown turbine is integrated with the PRT as shown in Figure 11.22. The integrated power recovery system can produce electricity while the main air blower is run by motor. 

The difficulty in direct synthesis of mesoporous transition metal oxides by soft templating (surfactant micelles) arises from their air- and moisture-sensitive sol-gel chemistry [4,10,11]. On the other hand, mesoporous silica materials can be synthesized in nimierous different solvent systems (i.e., water or water-alcohol mixtures), various synthetic conditions (Le., acidic or basic, various concentration and temperature ranges), and in the presence of organic (Le., TMB) and inorganic additives (e.g., CT, SO, and NOs ) [12-15]. The flexibility in synthesis conditions allows one to synthesize mesoporous silica materials with tunable pore sizes (2-50 nm), mesostructures (Le., 2D Hexagonal, FCC, and BCC), bimodal porosity, and morphologies (Le., spheres, rods, ropes, and cubes) [12,14,16-19]. Such a control on the physicochemical parameters of mesoporous TM oxides is desired for enhanced catalytic, electronic, magnetic, and optical properties. Therefore, use... 

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