Process condition

The process conditions will influence the particle degradation by generating the stress on the individual particles on the one hand and by affecting the material properties and consequently the particle friability on the other. 

A lot of attempts have been made to describe the time dependence of the attrition rate in batch fluidized bed processes. Gwyn (1969) studied the degradation of catalysts in a small-scale test apparatus and defined the elutriated particles as the only attrition product. He described the increase of the elutriated mass, Wel, with time, t, based on the initial solid bed mass, Wbed 0, by the now widely known Gwyn equation  

For several batches of the same catalyst with quite different mass median diameters, Gwyn found the exponent b to be constant, whereas the attrition constant Ka was found to decrease with mean particle size. Equation (1) is, therefore, valid for a particular size distribution only. Other 

Temperature. There are three conceivable temperature effects that may influence the particle degradation in an either direct or indirect way, i.e., thermal shock, changes in particle properties and changes in the gas density. 

Pressure. The absolute pressure is unlikely to have a direct effect on attrition unless it affects the amount of adsorbed surface layers. But there is again an effect on the gas density that is similar to the effect of temperature mentioned above. Moreover, the rate of pressure change may have more influence. 

The parameters in the process are spinning voltage, distance between the tip of the capillary and the collector, solution flow rate (feed rate), needle diameter, and, finally. 

For fixed-bed hydroprocessing units, the process conditions - pressure, temperature, space velocity, and catalyst - are determined by feed quality and process objectives. Table 12 shows typical process conditions for the hydrotreating of different feeds in fixed-bed hydrotreating units. The values shown are approximate. 

The H2/Oil ratios are for units in which off-gas from the high-pressure separator is recycled. For once-through naphtha hydrotreaters associated with catalytic reformers, the H2/Oil ratio can be much higher than 350 scf bbl (60 m /w ). For units that treat olefinic cracked stocks from FCC or coking units, H2/Oil ratios are higher to control the extra heat released by olefin saturation. 

Commerical polymerizations of ethylene, propene, and other a-olefins are carried out as slurry (suspension) and gas-phase processes [Beach and Kissin, 1986 Diedrich, 1975 Lieberman and Barbe, 1988 Magovern, 1979 Vandenberg and Repka, 1977 Weissermel et al., 1975]. Solution polymerization has been used in the past for ethylene polymerization at 140-150°C, pressures of up to 8 MPa (1 MPa = 145 psi = 9.869 atm), using a solvent such as cyclohexane. The solution process with its higher temperatures was employed for polymerization with the relatively low efficiency early Phillips initiators. (Polyethylene, but not the initiator, is soluble in the reaction medium under the process conditions.) The development of a variety of high-efficiency initiators has allowed their use in lower-temperature suspension and gas-phase processes, which are more advantageous from many 

Both traditional Ziegler-Natta and metal oxide Phillips-type initiators are used in suspension polymerizations (Secs. 8-4a, 8-4j) [Kaminsky, 2001], Both types of initiators are used for ethylene, but only the traditional Ziegler-Natta initiators are used for propene since Phillips-type initiators do not yield stereoselective polymerizations. 

Metallocene initiators reached commercialization near the beginning of the twenty-first century. These initiators probably accounted for about 5% of the total production of HDPE, LLDPE, and PP in 2002. The relative importance of metallocene initiators compared to the traditional Ziegler-Natta and Phillips-type initiators will increase in the future. 

With the carboxylate layer on the membrane, the concentration of NaOH in the catholyte can be maintained at about 32%, which compares favorably with the 12% product from diaphragm cells. Consequently, considerably less thermal energy is needed for evaporation to the commercial 50% product. 

Voltage requirements vary inversely with temperature, so it is advantageous to operate at elevated temperatures. The perfluorinated membranes can tolerate sustained temperatures of 90 °C. 

Because the anolyte and catholyte are both quite concentrated, there are osmotic forces at work to dehydrate the membrane. To some extent dehydration is beneficial, because it increases the ratio of sulfonate to water in the membrane, which in turn improves permselectivity. But eventually the dehydration leads to an increase in membrane resistance. Therefore, raising the NaOH concentration to reduce evaporation costs would Hkely increase electrical power costs. 

Conversion 50% of total oxalic acid added to the system 

Chemical yield 100%, discounting the small percentages of glycolic apid and glyoxal formed 

Losses in current efficiency are attributed to hydrogen evolution. The companion reaction at the anode is the evolution of oxygen. For process conditions, see Table 6.1. 

The cost has been based on the production of 500, 1000, 1800, and 4000kg/annum of glyoxylic acid in the form of an aqueous 10% solution, by weight, saturated with oxalic acid. It does not, therefore, include the cost of oxalic acid recovery and product concentration. The costing of the process is in terms of added value it does not contain the costs of raw materials. All costs are in pounds sterling ( ). 

Using the nomenclature of Chapter 5, a unit cell or module is made up of an electrode pair. A number of modules form a cell stack. A notional flow sheet is shown in Fig. 6.1. 

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If refrigeration is required, consider higher pressure process conditions if this allows a less hazardous refrigerant to be used. 

In Chap. 10, modification of the process for reducing process waste was considered in detail. It also was concluded that to minimize utility waste, the single most effective measure would be improved heat recovery. The energy-targeting methods presented in Chaps. 6 and 7 maximize heat recovery for a given set of process conditions. However, the process conditions can be changed to improve the heat recovery further. 

Characterization of zeolites is primarily carried out to assess tire quality of materials obtained from syntliesis and postsyntlietic modifications. Secondly, it facilitates tire understanding of tire relation between physical and chemical properties of zeolites and tlieir behaviour in certain applications. For tliis task, especially, in situ characterization metliods have become increasingly more important, tliat is, techniques which probe tire zeolite under actual process conditions. 

Eactors that could potentiaHy affect microbial retention include filter type, eg, stmcture, base polymer, surface modification chemistry, pore size distribution, and thickness fluid components, eg, formulation, surfactants, and additives sterilization conditions, eg, temperature, pressure, and time fluid properties, eg, pH, viscosity, osmolarity, and ionic strength and process conditions, eg, temperature, pressure differential, flow rate, and time. 

Verification of the microbial retention efficiency of the membrane filters may be undertaken using either Hquid or aerosol challenge tests. A Hquid challenge test is more stringent. Furthermore, this test can provide retention information for process conditions such as extreme moisture after sterilization or air entrained with water drops. A Hquid challenge is performed using a protocol similar to that described for Hquid filtration. 

Smaller pore size microfilters in single-pass systems which have pore sizes small enough to remove some vimses by size exclusion have been examined (26,37,38). Minimum levels of vims removal can be estabhshed for these systems if fluid and process conditions are employed which minimize removal of viral particles by mechanisms other than size selection. 

Process conditions for methyl acrylate are similar to those employed for ethyl acrylate. However, in the preparation of butyl acrylate the excess butanol is removed as the butanol—butyl acrylate a2eotrope in the a2eotrope column. 

Stabilizers and pigments are normally slurried with macroglycol and added to the polymeric glycol charge, prior to diisocyanate addition. Therefore, care must be taken to avoid additives that react significantly with diisocyanates or diamines under processing conditions. Also, stabilizers should be chosen that have no adverse catalytic effect on the prepolymer or chain-extension reactions. 

Process conditions that favor chemical crimp formation are similar to those used for improved tenacity staple (2inc/modifier route). However, spin bath temperature should be as high as possible (ca 60°C) and the spin-bath acid as low as possible (ca 7%). Attempts have been made to overcome some of the leanness of high strength rayons by increasing the crimp levels. ITT Rayonier developed the Prim a crimped HWM fiber (36) and made the process available to their customers. Avtex developed Avdl 111. Neither remain in production. 

The processes used commercially for the manufacture of film and sheeting materials are generaUy similar in basic concept, but variations in equipment or process conditions are used to optimize output for each type of film or sheeting material. The nature of the polymer to be used, its formulation with plasticizers (qv), fillers (qv), flow modifiers, stabilizers, and other modifiers, as weU as its molecular weight and distribution are aU critical to the... 

Economic Market. The spice trade is controlled by many direct elements and responds slowly to supply and demand fluctuations. Resupply depends on growth to plant maturity, which for certain items, such as black pepper or nutmeg, can be several years. The raw material is directly affected by climate, adverse weather conditions, and control of plant diseases and insect and animal pests. Limited agricultural scientific advances are appHed to the cultivation of the botanicals, and there are many grades of product and degrees of quahty caused by different growing or processing conditions, sometimes by unknown factors as well. 

Certain CFCs are used as raw materials to manufacture key fluorinated olefins to support polymer apphcations. Thermolysis of HCFC-22 affords tetrafluoroethylene and hexafluoropropylene [116-15 ] under separate processing conditions. Dechlorination of CFC-113 forms chlorotrifluoroethylene [79-38-9]. Vinyhdene fluoride [75-38-7] is produced by the thermal cracking of HCFC-142b. 

Gases and vapors permeate FEP resin at a rate that is considerably lower than that of most plastics. Because FEP resins are melt processed, they are void-free and permeation occurs only by molecular diffusion. Variation in crystallinity and density is limited, except in unusual melt-processing conditions. 

Under normal processing conditions at 300—350°C, Tefzel resins are not subject to autocatalytic degradation. However, extended overheating can result in "blow-backs" through extmder feed hopper or barrel front. 

PVDE is not hazardous under typical processing conditions. If the polymer is accidentaky exposed to temperatures exceeding 350°C, thermal decomposition occurs with evolution of toxic hydrogen fluoride (HE). 

Food process optimi2ation measurements may link a single chemical such as a vitamin, or a physical change such as viscosity, to process conditions and to consumer acceptance. Retention levels of ascorbic acid [50-81-7] C HgO, or thiamine can often be used as an indicator of process conditions (see... 

Leaf materials also contain Hpoxidases and highly unsaturated Hpids. LPC process conditions should inactivate Hpoxidases to obtain a stable product... 

Plasteins ate stiU in the experimental stage of development. Eurther work is needed on the scale-up of processing conditions for plastein synthesis which would lead to commercially usefiil products and on the functional utiUty of plasteins as ingredients in foods. 

Natural style juices that contain the cloud are increasing in popularity, especiaHy apple juices, because these retain more fresh flavor if processed carefuUy. Optimum processing conditions chill the fmit to 4°C before milling, add 500 ppm ascorbic acid to retard browning, press under nitrogen, and flash pasteurize the juice as quickly as possible (4). 

Properties. Shell s two-step SMDS technology allows for process dexibiUty and varied product slates. The Hquid product obtained consists of naphtha, kerosene, and gas oil in ratios from 15 25 60 to 25 50 25, depending on process conditions. Of particular note are the high quaHty gas oil and kerosene. Table 2 gives SMDS product quaHties for these fractions. 

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