Vaporizer/cracker

Figure 1. Thermal cracking apparatus a, carbonizer/vaporizer/cracker b, small vaporizer/cracker...

Hard baked goods such as cookies and crackers have a relatively low water and high fat content. Water can be absorbed, and the product loses its desirable texture and becomes subject to Hpid rancidity. Packagiag for cookies and crackers includes polyolefin-coextmsion film pouches within paperboard carton sheUs, and polystyrene trays overwrapped with polyethylene or oriented polypropylene film. Soft cookies are packaged in high water-vapor-barrier laminations containing aluminum foil. 

Most refineries produce sufficient gas oil to meet the cat crackers demand. However, in those refineries in which the gas oil produced does not meet the cat cracker capacity, it may be economical to supplement feed by purchasing FCC feedstocks or blending some residue. The refinery-produced gas oil and any supplemental FCC feedstocks are generally combined and sent to a surge drum, which provides a steady flow of feed to the charge pumps. This drum can also separate any water or vapor that may be in the feedstocks. 

In most units, the increase in hydrogen make does not increase coke yield the coke yield in a cat cracker is constant (Chapter 5). The coke yield does not go up because other unit constraints, such as the regenerator temperature and/or wet gas compressor, force the operator to reduce charge or severity. High hydrogen yield also affects the recovery of Cj-H components in the gas plant. Hydrogen works as an inert and changes the liquid-vapor ratio in the absorbers. 

Nearly every cat cracker experiences some degree of coking/fouling. Coke has been found on the reactor walls, dome, cyclones, overhead vapor line, and the slurry bottoms pumparound circuit. Coking and fouling always occur, but they become a problem when they impact throughput or efficiency. 

Cat. cracker (fluid) Cost based on fresh 35,000 14,000,000 400 Includes vapor recovery and... 

The evaporating pans of M, Derosse differ from those of Rotii in the shape of the condensing vessel, which in the former s consists of a tube bent like a cracker, the folds of which lie in vertical plane. Instead of effecting the condensation by water, Derossb employs sirup which, being allowed to flow upon the tipper fold of the tubes, trickles down from one fold to another. In condensing the steam in the inside of the tube, the sirup which flows down the outside of the tubes becomes itself heated, and parts with a portion of its water while the heat of the tube and its vertical position determine an ascending current of air, which removes the vapor of water as it is formed. 

In the aforementioned process, the heat for the reboiler is usually available as waste heat from the steam cracker, for example, and is essentially cost-free. If this heat is not available, a heat pump can be used. The heat pump can upgrade the heat, at an exergetic cost, to the desired temperature level. If the separation is viewed in isolation, this means that the heat rejected by the condenser at relatively low temperature, can be upgraded to be the higher temperature heat input for the reboiler. A schematic of the heat pump process is given in Figure 10.2. The overhead vapors are heated slightly in the reflux subcooler, which enables these vapors to be compressed and cooled in the condenser-reboiler. 

Another opportunity for advancement in ethylbenzene synthesis is in the development of liquid phase processes that can handle low cost feedstocks, including dilute ethylene such as ethane/ethylene mixtures. The use of dilute ethylene has become increasingly attractive since it has the potential to debottleneck ethylene crackers. Currently higher temperature, vapor phase technologies can tolerate contaminants that enter with the dilute ethylene feed from FCC units. However, these same contaminants can accelerate catalyst aging in lower temperature, liquid phase operations because they are more strongly adsorbed at the lower temperatures. Acid catalysts that tolerate elevated levels of contaminants would facilitate the development of dilute ethylene-based processes. These same catalysts could be useful in applications where lower cost or lower quality benzene feeds are all that are available. 

Downstream of the reaction zone, the lower static pressure permits the reactor content to boil and applies the thermosyphon effect for circulation. EDC vapor leaves the horizontal vessel and either enters the reboiler of a column (e.g., reboiler of high-boil-heads and/or vacuum column) or a heat exchanger, which condenses the EDC vapor. The reaction heat is transferred to the column indirectly. A fraction of the condensed EDC is fed back to the reactor and the rest is directly sent to the EDC cracker without further distillation. 

Mass Spectrometric Analysis Combusted sample tubes were attached to a purification vacuum line connected to the inlet system of the mass spectrometer. Sample tubes were opened under vacuum using a tube-cracker (35), and the gases were passed through a dry ice trap to remove water vapor and a liquid nitrogen trap to collect CO 2. Noncondensible gases were pumped away. The purified CO2 was thawed and admitted into the inlet system of the mass spectrometer for determination of isotopic composition ... 

Hundreds of fluidized bed crackers are in operation. The vessels are large, as much as 10 m or so in diameter and perhaps twice as high. Such high linear velocities of vapors are maintained that the entire catalyst content of the vessels circulates through the cyclone collectors in an hour or so. Electrical precipitators after the cyclone collectors have been found unnecessary. 

Chemical stability is an extremely important characteristic of HDV s, but one that has received relatively limited mention in the literature. Most reported studies have dealt with just two sorts of environments The first are those encountered in chemical dealumination processes—strong acids, chelating agents (e.g., EDTA, or soluble silicon sources (e.g., amnionium f luorosilicate). [9,10,11] The second deals with catalytic process environaients—ammonia vapor in hydrocrackers [12,13] or vanadic acid in fluid crackers [14]. Essentially no studies directed towards the specific needs of the catalyst manufacturer are available. 

Catalysts used in this process are of two types. Special acid-washed clays of particle diameters in the 200-400- xm range are used in fluidized bed versions of cracking [19]. In these units the catalyst is kept suspended or fluffed up on an upward moving stream of hot gas oil vapors, which ensures continuous exposure of all catalyst faces to the raw material and provides continuous turnover of catalyst. Synthetic catalysts are prepared from a mixture of 85-90% silica and 10-15% alumina, or from synthetic crystalline zeolites (molecular sieves) [19]. They are either used in a small particle size suitable for use in a fluidized bed, or can be formed into 3- to 4-mm diameter pellets appropriate for crackers, which use a moving bed for catalyst cycling. 

These acid-catalyzed changes are brought about by passing hot gas oil vapors either through a mechanically circulated bed of the larger pellets or upward through a fluidized bed of more finely divided catalyst particles. The upflow of vapors provides the fluidizing action of the catalyst, hence the units are referred to as fluidized cat crackers or FCC units. To avoid loss of... 

Fluid catalytic cracker unit Vapor phase catalytic Convert vacuum gas oil to catalytic naphtha... 

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