Flue Gas System

The FCC catalyst s physical and chemical properties dictate how much feed can be processed. Chemical properties, such as rare earth 

Consider reformulating the catalyst—custom formulations are available. Increasing rare-earth content can reduce the wet gas rate. Catalyst is usually selected for properties other than its ability to flow. However, if it does not flow, it is not going to work well. Catalyst physical properties should be compared with those of catalysts that have circulated well. Evaluate the economics of using metal passivation additives and other catalyst enhancing additives. 

Debottlenecking usually results in more feed. Both the main fractionator and the gas plant must be able to recover the incremental product. 

The main fractionator can be limited by several factors including  

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W ste Hea.t Boilers. In a conventional FCCU flue gas system, the regenerator combustion gases pass through two stages of cyclonic separators, a sHde valve, orifice chamber, waste heat boiler, and electrostatic precipitator. The sHde valve and orifice chamber act in combination to reduce the flue gas to essentially atmospheric pressure. 

Checks to the air and flue gas system include visually inspecting the furnace and periodically monitoring all fans, levels of draft, furnace pressure, excess air demands, and combustion efficiency. 

Similarly, when burning low grade, high-ash fuels, the particulate fly ash is also carried through the flue gas system and into the atmosphere unless precautionary measures are taken. Dust control and desulfurization equipment employed today includes ... 

The pressure balance should be examined to determine the normal pressure readings in the reactor, regenerator, air system, flue gas system, and main fractionator and overhead system. These need to be followed on a time basis and plotted against variables such as feed rate, wet gas rate, and dry gas rate to see if and where problems may occur. Adjustments may be possible if the spent or regenerated catalyst slide valve delta P is at a minimum to provide more operating room. 

All kinds of interactions and combinations are possible. In cooling water, for instance, the deposits are likely to include micro-organisms, particles, scale, and corrosion products. In flue gas systems, the fouling may be because of particle deposition, chemical reaction, and corrosion. In crude oil processing, the deposits may be products of reaction, combined with particle deposition and corrosion. 

The ideal temperature may not exist in the flue gas system. A typical operating temperature range is 550-725°F. This temperature range may not exist in all facilities, and may require modification of the heat recovery train. 

This work shows that oxygen-free sulfite in lime/limestone slurries, exposed to sulfur dioxide, slowly decomposes under process conditions. In fact, auto-redox reactions of sulfur oxyacids can occur in all coal desulfurization systems, including coal-gasification systems and impurities present in commercial flue gas systems are capable of catalyzing the reaction under process conditions. Our experiments indicate that any large-scale coal utilization will depend on appropriate control of the autoredox reactions of sulfur species. 

Flue gas system (type C room-sealed, type B without a fan, type B with forced draught burner), by capacity class (up to 70 kW, 70-300 kW, 300-1000 kW)... 

The use of additives for deposit control in flue gas systems has a potentially excellent future but a great deal of fundamental research is required to provide a better understanding of the chemical and physical mechanisms involved. The problem is complicated by the complex composition of most fuels. 

In a pulverised fuel operation the fuel and residues remain in the high temperature region for only 1 to 2 seconds. The majority of the ash (at least 80%) passes through the flue gas system for removal in precipitators. The remainder of the ash goes out of the bottom of the pulverised fuel boiler. Evolution of organic volatile compounds into the gas stream is minimised due to the short residence time of the fuel and incombustibles. 

Jenkins [1994] has reviewed optical methods for the detection of deposits in flue gas systems as background to the development of the high temperature salt deposition probe described above. He concludes that the measurement techniques best suited to the test requirements are interferometry and ellipsometry. 

In-process measurements of dioxins in a hot blast cupola with dry dedusting have shown that high PCDD/F-levels (5 ngTEQ/Nm ) occur in the heat-exchanger. Other parts of the flue-gas system show much lower values. Reduction measures should therefore aim at minimising the... 

Flue gas from stage one passes into the bed of stage two thereby enabling one flue gas system... 

Steam may also be supplied to municipalities. However, the supply of this heat/steam cannot be guaranteed in all cases for instance during flue gas system or glass furnace maintenance. 

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