Catalyst Feed Rate

Increasing catalyst feed rates will increase reactor production rates which will decrease catalyst residence time and consequently, catalyst productivity (lbs PE/lb catalyst). Generally a catalyst productivity of 1,500 lb PE/ lb catalyst is used as the minimum acceptable catalyst productivity in a commercial reactor. 

Reactor conditions are monitored by a gas chromatographic system that analyzes the vapor content at regular intervals and advanced computer control systems regulate the feed rate of all reagents. 

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Explore the effect of catalyst feed rate on conversion. 

What conversion would be achieved if the catalyst feed rate to reactor were increased by a factor of 5 ... 

What conversion can be achieved in a moving-hed reacior containing 50 kg of catalyst with a catalyst feed rate of 2 kg/h Toluene is fed at a pressure of 2 aim and a rate of 10 mol/min. 

Dye provided limited process conditions, but based on a catalyst feed rate of 1.33 Ib/hr and an average catalyst residence time of 1.5 hours, the production rate can be estimated from the volume of the reaction zone. Assuming a fluidized bulk density of about 12 Ibs/ft, the reaction zone would contain about 7,000 lbs of polyethylene. A production rate of approximately 4,700 Ib/hr would be needed to accoxmt for a 1.5 hr catalyst residence time. Polymerization temperature was 210°F and ethylene pressure was 450 psi. 

Polymerization conditions may vary over a wide range, where polymerization temperatiues vary from 60-110 C and total reactor pressure from 100-350 psig. Comonomers are usually limited to 1 -butene or 1-hexene to control polymer density, but 1-octene may be used if a particular catalyst exhibits a relatively high reactivity with 1-octene such as metallocene catalyst systems. Resin production rates are controlled by primarily two variables catalyst feed rate and ethylene partial pressure. In a modern gas-phase process, operating in what Univation designates as supercondens-ing mode, production rates for many grades of polyethylene of at least 125,000 Ibs/hr are reached. 

The following conditions are stipulated the catalyst decomposition rate constant must be one hour or greater the residence time of the continuous reactor must be sufficient to decompose the catalyst to at least 50% of the feed level the catalyst concentration must be greater than or equal to 0.002 x Q, where the residence time, is expressed in hours. An upper limit on the rate of radical formation was also noted that is, when the rate of radical formation is greater than the addition rate of the primary radicals to the monomers, initiation efficiency is reduced by the recombination of primary radicals. 

Another nickel cataly2ed process is described ia a Tolochimie patent (28). Reaction conditions claimed are 1—2.4 MPa (150—350 psi) at 100°C minimum. The combination continuous stirred reactor and gravity decanter uses density-driven circulation between the two vessels to recirculate the catalyst to the reaction 2one without the use of filters or pumps. Yield and catalyst usage can be controlled by varying the feed rates. 

Thus the ECCU always operates in complete heat balance at any desired hydrocarbon feed rate and reactor temperature this heat balance is achieved in units such as the one shown in Eigure 1 by varying the catalyst circulation rate. Catalyst flow is controlled by a sHde valve located in the catalyst transfer line from the regenerator to the reactor and in the catalyst return line from the reactor to the regenerator. In some older style units of the Exxon Model IV-type, where catalyst flow is controlled by pressure balance between the reactor and regenerator, the heat-balance control is more often achieved by changing the temperature of the hydrocarbon feed entering the riser. 

Coke on the catalyst is often referred to as delta coke (AC), the coke content of the spent catalyst minus the coke content of the regenerated catalyst. Delta coke directly influences the regenerator temperature and controls the catalyst circulation rate in the FCCU, thereby controlling the ratio of catalyst hydrocarbon feed (cat-to-od ratio, or C/O). The coke yield as a fraction of feed Cpis related to delta coke through the C/O ratio as ... 

The equivalent nickel content of the feed to the FCCU can vary from <0.05 ppm for a weU-hydrotreated VGO to >20 ppm for a feed containing a high resid content. The nickel and vanadium deposit essentially quantitatively on the cracking catalyst and, depending on catalyst addition rates to the FCCU, result in total metals concentrations on the equiUbrium catalyst from 100 to 10,000 ppm. 

Fig. 13. Flowsheet of medium pressure synthesis, fixed-bed reactor (Lurgi-Ruhrchemie-Sasol) having process conditions for SASOL I of an alkaline, precipitated-iron catalyst, reduction degree 20—25% having a catalyst charge of 32—36 t, at 220—255°C and 2.48 MPa (360 psig) at a fresh feed rate of...

The principal advance ia technology for SASOL I relative to the German Fischer-Tropsch plants was the development of a fluidized-bed reactor/regenerator system designed by M. W. Kellogg for the synthesis reaction. The reactor consists of an entrained-flow reactor ia series with a fluidized-bed regenerator (Fig. 14). Each fluidized-bed reactor processes 80,000 m /h of feed at a temperature of 320 to 330°C and 2.2 MPa (22 atm), and produces approximately 300 m (2000 barrels) per day of Hquid hydrocarbon product with a catalyst circulation rate of over 6000 t/h (49). 

For catalytic investigations, the rotating basket or fixed basket with internal recirciilation are the standard devices nowadays, usually more convenient and less expensive than equipment with external recirculation. In the fixed basket type, an internal recirculation rate of 10 to 15 or so times the feed rate effectively eliminates external diffusional resistance, and temperature gradients. A unit holding 50 cm (3.05 in ) of catalyst can operate up to 800 K (1440 R) and 50 bar (725 psi). 

NO analyzers at the preheater inlet and catalyst vessel outlet monitor NO concentrations and control the ammonia feed rate. The effluent gives up much of its heat to the incoming gas in the feed/effluent exchanger. The vent gas is discharged at about 350° F. 

Runaway Reactions Runaway temperature and pressure in process vessels can occur as a resiilt of many fac tors, including loss of cooling, feed or quench failure, excessive feed rates or temperatures, contaminants, catalyst problems, and agitation failure. Of major concern is the high rate of energy release and/or formation of gaseous produc ts, whiai may cause a rapid pressure rise in the equipment. In order to properly assess these effec ts, the reaction kinetics must either be known or obtained experimentally. 

The catalyst should be the copper-based United Catalyst T-2370 in 3/16 , reduced and stabilized, in extrudate form. Initially, 26.5 g of this should be charged to the catalyst basket. This catalyst is not for methanol synthesis but for the low temperature shift reaction of converting CO to CO2 with steam. At the given conditions it will make methanol at commercial production rates. Somewhat smaller quantity of catalyst can also be used with proportionally cut feed rates to save feed gas. 

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