Sizes of Mass Exchangers


Types and sizes of mass exchangers  [c.21]

TVpes and sizes of mass exchangers  [c.23]

Types and sizes of mass exchangers  [c.25]

A corresponding problem occurs in the third tier of heat-exchange network design (Fig. 2). Limits on utihties and number of heat exchangers were set as a first-tier objective. Candidate networks were proposed with the help of synthesis algorithms in the second tier. Where network topology is fixed, the detailed design calculations for individual heat exchangers can proceed. Heat exchangers can be designed as single- or multiple-shell units. A low AT for a given exchanger may make it necessary to use several shells in series to improve the F factor. In some cases, large flow rates or area requirements may make it necessary to have several shells in parallel. In any case, the design of the various units in the network can be completed. Subsequently, individual equipment is specified, and a performance calculation is needed for the network. Variation in exchanger sizes and stream flows provides an opportunity for further optimization of the network.  [c.526]

The fundamental parameters for the ammonia—hydrogen exchange (Table 6) are much more favorable than the corresponding factors in the H2S/H2O system, but the exchange reaction must be catalyzed to achieve a usefiil rate of exchange. The discovery (65) that the amide ion, NH2, produced by addition of alkaH metal to Hquid ammonia, is an efficient catalyst for the NH2/H2 exchange stimulated intensive interest in this system (66,67). A dual-temperature system operating with a hot column at 70°C (single stage separation factor of 2.9) and a cold column at —40°C (single stage separation factor of 5.9) would have an effective separation factor of 2.0, which would permit extraction of 50% of the deuterium from the ammonia feed. Catalysis of the exchange by potassium amide is sufficiently effective even at —40° C to attain equHibrium in reasonably sized exchange columns. A single-temperature plant has been operated in France to produce about 20 t/yr D2O (68). The primary limitation on the use of this process has been the avaHabHity of sufficient quantities of ammonia for plant feed. Even an ammonia plant producing 1000 t/d would provide sufficient feed only to permit production of 60—70 t/yr D2O. A concept using an enrichment stripping system with a regeneration column has been developed (59,60) in which water is the deuterium feed via a hydrogen—water exchange step. This would, in principle, aHow H2/NH2 chemical exchange plants of unHmited production capacity.  [c.7]

Cost Charts Equipment cost may be related to one or more basic sizing criteria. Examples of these sizing criteria include diameter for mass exchange trays, diameter and height for packed columns, heat transfer area for heat exchangers, horse power for pumps and compressors, volumetric flow rate for fans and blowers and weight or volume for storage tanks. Extensive compilations of charts correlating equipment cost to sizing criteria have been published in books, journals, and vendor catalogues.  [c.304]

Once right sizing is addressed, new high-efficien-cy equipment, including furnaces, boilers, heat pumps, and air conditioners provide further energy savings and other quality improvement benefits. Geothermal heat pump equipment offers further efficiency gains by taking advantage of much more stable year-round ground temperatures (warmer than ambient air in the winter and cooler than ambient air in the summer) with buried heat exchanger loops.  [c.207]

This tube has a ratio of outside to inside surface of about 3.5 and is useful in exchangers when the outside coefficient is poorer than the inside tube coefficient. The fm efficiency factor, which is determined by fm shape and size, is important to final exchanger sizing. Likewise, the effect of the inside tube fouling factor is important to evaluate carefully. Economically, the outside coefficient should be about V5 or less than the inside coefficient to make the finned unit look attractive however, this break-even point varies with the market and designed-in features of the exchanger.  [c.218]

Feed Preparation. The burden charged to a phosphoms furnace must be kept porous enough to allow the gases generated in the reaction zone near the bottom of the furnace to escape while losing heat to the feed and being cleaned of entrained dust. To allow sufficient porosity, the diameter of the phosphate ore, quartzite, and coke particles are sized in the range of 0.5—5 cm and must not contain excessive fines that will block the gas flow. The coke is received from suppHers already in the appropriate sizes or is cmshed and screened on-site. The quartzite is generally mined locally and is cmshed and screened to obtain the desired size distribution. The phosphate ore usually consists of fine particles that must be agglomerated and sintered by some process into a hardened mass that will resist deterioration during subsequent handling. The sintering or calcination step also serves to remove organics and other impurities that contaminate the product and cause bridging of the burden above the reaction zone in the furnace, which again restricts the gas flow and inhibits the heat exchange and dust removal from the off-gas. A number of technologies are therefore utilized in the phosphoms industry to prepare the phosphate ore.  [c.349]

A tower operated at atmospheric pressure for dissolving glass has been described (21). The dissolution rate is independent of Hquor concentration and circulation rate. The principal factors are temperature, glass composition, and particle surface area. The glass must be sized to avoid a phenomenon referred to as sticker, which occurs when a dissolving glass mass solidifies. Studies of the dissolution rate of a 2.0 ratio sodium sdicate glass into concentrated solutions indicate that the rate of dissolution, expressed as kg dissolved per hour per kg of glass, is independent of the initial particle size (22). In addition, ordy linear increases in the solution concentration as a function of time were observed under conditions in which Na+ ion exchange was suppressed by an increase of Na+ activity of the dissolving Hquor. The rate of increase in solution concentration appears to be related inversely to the sodium ion activity. It is also expected that the dissolution process would be sensitive to the amount of ion either in the glass owing to incomplete  [c.5]

The flow along the membranes also improves the mass transport there, and the separators between the membranes are constmcted to provide good flow distribution and mixing on the membrane surfaces. Membrane sizes are often about 0.5 x 1 m, spaced about 1 mm apart. Many types of polymers are used to manufacture these ion-exchange-selective membranes, which are often reiaforced by strong fabrics made of other polymers or glass fibers.  [c.251]

If cooling water is not available, air-cooled exchangers can be furnished, even in relatively small sizes. The cost is higher than a shell and tube-water-cooled exchanger. Also the outlet oil temperature will be higher than that from the water-cooled exchanger. This is no particular problem if the compressor designer is aware of the higher temperature. More oil will have to be circulated to make up for the loss of the temperature differential.  [c.315]

Conservation is a general concept widely used in chemical engineering systems analysis. Normally it relates to accounting for flows of heat, mass or momentum (mainly fluid flow) through control volumes within vessels and pipes. This leads to the formation of conservation equations, which, when coupled with the appropriate rate process (for heat, mass or momentum flux respectively), enables equipment (such as heat exchangers, absorbers and pipes etc.) to be sized and its performance in operation predicted. In analysing crystallization and other particulate systems, however, a further conservation equation is  [c.45]

In order to find the micromixing times in the feed zones and the meso-mixing time characteristic of blending of the feed solutions with the bulk in the SFM, it is essential to determine the local distribution of the specific energy dissipation in the reactor. It is possible to obtain this local distribution using CFD, and find the diffusive and convective exchange parameters. Because the local energy dissipation is different on different scales of operation with the same mean specific power input, the micromixing (diffusion) and mesomixing (convection) times on different scales differ. Consequently, different diffusive and convective mass transfer between the feed zones and the bulk zone leads to different levels of supersaturation on different scales and therefore to different precipitation kinetic rates and mean crystal sizes with scale-up.  [c.220]

Heat and mass transfer from the gas to the surface of the sohds is extremely efficient hence the eqmpment size required for a given duty is frequently less than required when an ordinaiy direct-heat rotary vessel with hfting flights is used. Purchase-price savings are partially balanced, however, by the more complex construction oi the Roto-Louvre unit. A Roto-Louvre dryer will have a capacity roughly 1.5 times that of a single-shell rotary dryer of the same size under equivalent operating conditions. Because of the cross-flow method of heat exchange, the average At is not a simple function of inlet and outlet At s. There are currently no published data which permit the sizing of equipment without pilot tests as recommended by the manufacturer. Tnree applications of Roto-Louvre diyers are outlined in Table 12-25. InstaUation, operating, power, and maintenance costs will be similar to those experiencea with ordinaiy direct-heat rotaiy diyers. Thermal efficiency will range from 30 to 70 percent.  [c.1212]

Manufacture. MTBE is easily made by the selective reaction of isobutylene and methanol over an acidic ion-exchange resin catalyst, in the Hquid phase and at temperatures below 100°C. To be economically competitive, MTBE s use as an octane enhancer in gasoline has been dependent on low cost isobutylene. There are a number of possible isobutylene sources for making MTBE (see Butylenes). During the 1980s, much of the MTBE was made with isobutylene contained in mixed butanes /butylenes process streams that was produced from petrochemical olefin plants or refinery fluid catalytic crackers. MTBE plant sizes from these feedstock sources are limited by the amount of by-product isobutylene produced in these operations, and are usually in the range of one to six thousand barrels per day (40 to 250 t/yr). Larger amounts of isobutylene for MTBE can be made from butanes by first isomerizing the normal butanes to isobutane, and then dehydrogenating to isobutylene. This is a much more capital intensive process, and therefore the plant sizes in the United States are usually at least 500,000 t/yr to be economically competitive. Even at this size, it is stiU a relatively higher cost source of MTBE than that made from by-product isobutylene in ethylene plants or refineries. However, because of the growing need to meet the gasoline oxygen requirements for the U.S. Clean Air Act, many of these world-scale MTBE plants will need to be built (24).  [c.428]

Pressure Another approach to parametric pumping is accomplished by pressure cycling of an adsorbent. An adsorbent bed is alternately pressurized with forward flow and depressurized with backward flowthrough the column from resei voirs at each end. Like TSA parametric pumping, one component concentrates in one reservoir and one in the other. The pressure mode of parametric pumping has been called pressure-swing parametric pumping (PSPP) and rapid pressure swing adsorption (RPSA). It was developed to minimize process complexity and investment at the expense of product recov-eiy. RPSA is practiced in single-bed [Keller and Jones in Flank, Adsorption and Ion Exchange with Synthetic Zeolites, 135 (1980), pp. 275-286] and multiple-bed [Earls and Long, U.S. Patent number 4,194,892, 1980] implementations. Adsorbers are short (about 0.3 to 1.3 m), and particle sizes are very small (about 150 to 400 mm). The total cycle time including adsor ption, dead time, countercurrent purge, and sometimes a second dead time, ranges from a few to about 30 seconds. The feature of RPSA that differentiates it from traditional PSA is the existence of axial pressure profiles throughout the cycle much as temperature gradients are present in TSA parametricpumping. Whereas PSA processes have essentially constant pressure through the bed at any given time, the flow resistance of the veiy small adsorbent particles produce substantial pressure drops in the bed. These pressure dynamics are key to the attainment of separation performance. RPSA has been commerciaHzed for the production of oxygen and for the recovery of ethylene and chlorocarbons (the selectively adsorbed species) in an ethylene-chlorination process while purging nitrogen (the less selectively adsorbed specie).  [c.1547]

Despite the relative low resolution power, many protein purification protocols contain at least one sizing step. SEC is generally performed late in the procedure when the number of proteins is small. The term polishing describes the final step of a protein purification where the objective is to remove possible impurities, such as structurally very similar or closely related forms of the product (aggregates, deamidated or oxidized product, isoforms, etc.), host proteins, reagents and buffer substances, leachables from chromatographic supports, endotoxins, nucleic acids (DNA, RNA), or viruses. This is usually the step where SEC is used. It can separate high and low molecular mass impurities from the target product in one step while simultaneously exchanging the buffer. However, if a target protein is extremely large or small, SEC can be utilized earlier in the purification procedure.  [c.241]


See pages that mention the term Sizes of Mass Exchangers : [c.20]    [c.519]    [c.244]    [c.260]   
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Pollution prevention through process integration  -> Sizes of Mass Exchangers