Replacement of catalyst

A fluidi2ed-bed catalytic reactor system developed by C. E. Lummus (323) offers several advantages over fixed-bed systems ia temperature control, heat and mass transfer, and continuity of operation. Higher catalyst activity levels and higher ethylene yields (99% compared to 94—96% with fixed-bed systems) are accompHshed by continuous circulation of catalyst between reactor and regenerator for carbon bum-off and continuous replacement of catalyst through attrition. 

Heat exchangers need to be sited so that the tube bundles can be easily withdrawn for cleaning and tube replacement. Vessels that require frequent replacement of catalyst or packing should be located on the outside of buildings. Equipment that requires dismantling for maintenance, such as compressors and large pumps, should be placed under cover. 

The replacement of catalysts might be on a continuous basis if homogeneous catalysts are used (see Chapters 5 and 7). Heterogeneous catalysts might also be replaced... 

The fluid bed operation allows the continuous removal of a portion of deactivated catalyst and continuous replacement of catalyst during operation. This results in a steady state performance. In addition, a fluid bed reactor is nearly isothermal by design, which minimizes catalyst deactivation due to exposure to excessive heat. 

Solid inorganic foulants may also accumulate on the catalyst. Little can be done to remove such foulants except by mechanical means. This is usually inefficient, and replacement of catalyst is often necessary. 

Coordination polymerizations are becoming an inspiration source for further methodical development in addition polymerizations. The nearest aim could possibly be the insertion of polar monomers (as indicated by group transfer polymerization) and a deepening of our understanding of catalysis. Research in this field should lead to partial or even total replacement of catalysts by other means. I shall try to indicate one of the possibilities. 

Implement process control programme at every step of production (analysis of raw material, reactor operation, calibration of instruments, replacement of catalyst, filtration of raw material/product streams, purification steps for final product, etc.). 

It is inevitable that Cu based catalysts are poisoned. Self-protection is usually adopted to assure CO conversion. The choice of catalysts and their replacement periods are directly based on the efficiency and economy of an ammonia plant. A little increase in CO conversion will compensate the fee of replacement of catalysts in short term. 

If the sum in the feedstock of the parts-per-million of iron and vana dium, plus ten times the ppm of nickel and copper, is above 6 to 10, rapid replacement of catalyst (in the Fluid process) will be necessary. Thus, a gas oil that contains 0.5 ppm V, 1.0 ppm Fe, 0.3 ppm Ni, and 0.1 ppm Cu results in a sum of 5.5, and rapid contamination of the catalyst will occur. Another authority has mentioned the following limits for a satisfactory feed Fe, 1.0 V, 0.4 Ni, 0.15 and Cu, 0.1 ppm. Although this is a fairly good feed according to the formulation given just above (total = 3.9, which is under 5), it would be classified as bad by the... 

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