Regenerator velocity

Oxygen enrichment. In a cat cracker, which is either air blower or regenerator velocity limited, enrichment of the regenerator air can increase capacity or conversion provided there is good air/ catalyst distribution and that the extra oxygen does not just burn CO to CO2. 

Excessive regenerator velocity Poor spent catalyst initial distribution... 

Coke makes coke Damaged air grid Insufficient air Excessive regenerator velocity... 

In comparison, units that are designed with turbulent beds have a lower superficial velocity limit because of soflds entrainment and are unable to independently control the entrained soflds recycle. The soflds loading in the turbulent-bed regenerator configuration are equal to the reactor—regenerator circulation plus the entrained soflds via the cyclone diplegs. 

The cyclones are typically designed with diameters of 100—160 cm for ease of maintenance. Cyclone inlet velocities are usually restricted to 18—21 m /s in the first stage and to 20—26 m/s in the second stage to achieve satisfactory pressure drop and erosion characteristics (62). The number of sets of two-stage cyclones thus depends on the total gas flow. Finding room to house all the necessary cyclones within the regenerator frequently requires considerable ingenuity (62). 

The catalysts used in this CCR commercial service must meet several stringent physical property requirements. A spherical particle is required so that the catalyst flows in a moving bed down through the process reactors and regenerator vessel. These spheres must be able to withstand the physical abuse of being educated and transferred by gas flow at high velocity. The catalyst particles must also have the proper physical properties, such as particle size, porosity, and poresize distribution, to achieve adequate coke combustion kinetics. 

An initially clean activated carbon Led at 320 K is fed a vapor of benzene in nitrogen at a total pressure of 1 MPa. The concentration of benzene in the feed is 6 mol/m. After the Led is uniformly saturated with feed, it is regenerated using benzene-free nitrogen at 400 K and 1 MPa. Solve for Loth steps. For sim-phcity, neglect fluid-phase acciimiilation terms and assume constant mean heat capacities for stationary and fluid phases and a constant velocity. The system is described by... 

There are two regions in the regenerator the dense phase and the dilute phase. At the velocities common in the regenerator, 2-4 ft/sec, the bulk of catalyst particles are located in the dense bed immediately above the air distributor. The dilute phase is the region above... 

The lift pipe design was tapered to a larger diameter at the top. This minimized the effects of erosion and catalyst attrition, and also prevented the instantaneous total collapse of circulations when the saltation concentration, or velocity, of solids is experienced (i.e. the slump veloeity-that velocity helow which particles drop out of the flowing gas stream). In a typical operation, 2 % to 4 % eoke can he deposited on the catalyst in the reactor and burned in the regenerator. Catalyst circulation is generally not sufficient to remove all the heat of eombustion. This facilitated the need for steam or pressurized water coils to be located in the regeneration zone to remove exeess heat. 

As flue gas leaves the dense phase of the regenerator, it entrains catalyst particles. The amount of entrainment largely depends on the flue gas superficial velocity. The larger catalyst particles, 50p-90p, fall back into the dense bed. The smaller particles, O 0.-5O i, are suspended in the dilute phase and carried into the cyclones. 

In earlier Model II and Model III FCC units, spent catalyst was transported into the regenerator using 50% to 100% of combu.stion air. This spent cat riser was designed for a minimum air velocity of 30 ft/sec (9.1 m/sec). 

Trickle valves have fallen off due to inadequate bracing and/or high superficial gas velocity in the regenerator. 

One of the advanced concepts for capturing CO2 is an absorption process that utilizes dry regenerable sorbents. Pure sodium bicarbonate from Dongyang Chemical Company and spray-dried sorbents were used to examine the characteristics of CO2 reaction in a flue gas environment. The chemical characteristics were investigated in a fast fluidized reactor of 0.025 m i.d., and the effects of several variables on sorbent activity, including gas velocity (1.5 to 3.5 m/s), temperature (40 to 70 °C), and solid concentration (15 to 25 kg/m /s)], were examined in a fast fluidized-bed. Spray-dried Sorb NX30 showed fast kinetics in the fluidized reactor. 

The fluidized reactor can be a bubbling fluidized type or a fast fluidized type, depending on the gas velocity and the reactivity of the sorbents. We adopted a fast fluidized bed type reactor for carbonation and regeneration reactions in order to identify the chemical characteristics of sorbents in a fast fluidized reactor of 0.025 m i.d. 

The conditions for a complete separation of a binary mixture can be defined in terms of the Yj model parameters, which are directly related with the TMB (SMB) operating variables (fluid and solid velocities in the four sections of the TMB unit). From the constraints presented, those related to sections II and III play the crucial role on the separation performance of the TMB. It is in these central zones that the separation between the two species takes place. The role of the adjacent sections (I and IV) is to prevent cross-contamination and to allow the improvement of the continuous operation of the system by regenerating the solid and liquid phases. Taking into account these considerations, a region of complete separation in a Ym-Yn plane can be defined. Considering that the constraints concerning sections I and IV are fulfilled, the YnrYn plot is 311 important tool in the choice of best operating conditions. 

---