Batch Determination

For forming, batches of the ceramic powder and processing additives are used. Processing additives are added to produce the particle dispersion and flow behavior required for forming. The various additives belong to the following classes  

Except the solvent, all other additives get eliminated during the processing, especially during the firing stage. Liquids are used to wet ceramic particles, to provide a viscous medium, and to dissolve salts, compounds, and polymeric substances. Water is the principal liquid used. For materials that react with water, nonaqueous liquids are used. Examples for such liquids are trichloroethylene, alcohols, ketones, and refined petroleum oil or liquid wax. 

Deflocculants are additives that prevent the close approach of particles. They adsorb on the particles and increase the repulsive forces. Coagulants do the opposite function. They reduce the repulsive forces or steric hindrance and promote particle agglomeration. When the agglomeration is produced by bridging action, the substances used are called flocculants, known 

Octyl phenoxy polyethoxy ethanol nonionic surfactant 

Different types of particle size distributions are used for forming ceramics. Batch composition gives the proportions of the constituents. Many parameters determine the consistency of a batch. They are  

---

Example 14.3 The initial portion of a reactor startup is usually fed-batch. Determine the fed-batch startup transient for an isothermal, constant-density... 

As has been mentioned previously, the approach to equilibrium can often be slow for macrocyclic complex formation indeed, equilibrium may take days, weeks or even months to be established. This may give rise to experimental difficulties in conventional titration procedures. Under such circumstances, it is usually necessary to carry out batch determinations in which a number of solutions, corresponding to successive titrations points, are prepared and equilibrated in sealed flasks. The approach to equilibrium of each solution can then be monitored at will. 

If the reactor is shut down for a period of 900 s (15 min) between batches, determine the optimum reaction time for the maximum rate of production of alkylate, and calculate this maximum rate in terms of mass P toluene consumed per unit time. 

Figure 5.8 — Probe-type sensor based on continuous circulation of a stream containing an acid-base indicator for the batch determination of COj in sea water, (a) Reagent delivery capillary, (d) Reagent exit capillary, (c) Optical fibre from source, (d) Optical fibre to detector, (e) White silicone rubber membrane. (/) White silicone sealant, (g) Epoxy resin, (/i) 0-ring. (/) Sensor housing. (/) Optical cable. (Reproduced from [12] with permission of the American Chemical Society).

Phase I and phase II investigations utilize the same basic principles and strategies to arrive at a final batch determination. 

The batch management of production simplifies the process and makes it easier to control the status of transformation between raw and final products [2], Some of the data used to follow the material performance around and out of the product manufacturing process are batch-where-used-list, initial status, batch determinations, master data, and expiration date check [15]. 

Process qualification (prevalidation batches) determine process capability, challenge in-process control limits... 

R.S. Flonorato, J.M.T. Carneiro, E.A.G. Zagatto, Spectrophotometric flow-batch determination of aluminum in plant tissues exploiting a feedback mechanism, Anal. Chim. Acta 441 (2001) 309. 

Data from batch experiments (11) were used to calculate the Freundlich constants for sorption from ground water that was uncontaminated by the sewage plume (Figure 1). Data from the replicate column experiments (closed square) plot almost on the line, which indicates that the batch-determined sorption constants can be used to describe Mo(VI) sorption in these two columns. 

The initial portion of a reactor startup is usually fed batch. Determine the fed-batch startup transient for an isothermal, constant-density stirred tank reactor. Suppose the tank is initially empty and is filled at a constant rate go with fluid having concentration Oin. A first-order reaction begins immediately. Find the concentration within the tank, a, as a function of time f < ifuu-... 

Titanium dioxide precipitation. Hydrated titanium dioxide is produced by hydrolysing the clarified liquor with steam. Precipitation of the hydrated Ti02 is achieved by boiling the liquor for several hours followed by cooling. The addition of a correct amount of titanium-containing seed nuclei to the batch determines the final size and form of the titanium dioxide crystal. 

Today the much higher spatial and temporal resolution of measurements is a powerful incentive for in situ determinations rather than time-consuming sampling, sample transfer and batch determinations in the laboratory. 

Davison, W. and C. Woof. 1978. Comparison of different forms of cadmium as reducing agents for the batch determination of nitrate. Analyst 103 403-406. 

Control experiment. This is not necessary if the sodium peroxide is known to be chlorine-free. If there is any doubt on this point, the whole operation should be repeated precisely as before, but omitting the organic halogen compound. A small thiocyanate titration value may be found, and this should be deducted from all determinations in which the above quantity of the particular batch of sodium peroxide is used. 

Before polyacrylamides are sold, the amount of residual acrylamide is determined. In one method, the monomer is extracted from the polymer and the acrylamide content is determined by hplc (153). A second method is based on analysis by cationic exchange chromatography (154). For dry products the particle si2e distribution can be quickly determined by use of a shaker and a series of test sieves. Batches with small particles can present a dust ha2ard. The percentage of insoluble material is determined in both dry and emulsion products. 

Interfacial Mass-Transfer Coefficients. Whereas equiHbrium relationships are important in determining the ultimate degree of extraction attainable, in practice the rate of extraction is of equal importance. EquiHbrium is approached asymptotically with increasing contact time in a batch extraction. In continuous extractors the approach to equiHbrium is determined primarily by the residence time, defined as the volume of the phase contact region divided by the volume flow rate of the phases. 

The determination of the need for either a batch or continuous furnace is dependent on production rate and the physical size and weight of the work to be processed. 

Hydrothermal Synthesis Systems. Of the unit operations depicted in Figure 1, the pressurized sections from reactor inlet to pressure letdown ate key to hydrothermal process design. In consideration of scale-up of a hydrothermal process for high performance materials, several criteria must be considered. First, the mode of operation, which can be either continuous, semicontinuous, or batch, must be determined. Factors to consider ate the operating conditions, the manufacturing demand, the composition of the product mix (single or multiple products), the amount of waste that can be tolerated, and the materials of constmction requirements. Criteria for the selection of hydrothermal reactor design maybe summarized as... 

Manufacture. Phosphoms sulfides are manufactured commercially by direct reaction of the elements. Elemental phosphoms and sulfur are measured into a reaction vessel containing a heel of molten phosphoms sulfide. The reaction can be batch or continuous. The ratio of phosphoms to sulfur in the feed determines which phosphoms sulfur compound (Table 5) is formed. The reaction temperature can be the boiling point or lower. For the boiling reactor (27,28), the phosphoms sulfide product is first purified by distillation and then condensed to a Hquid. Alternatively, the Hquid product can be formed directly in a nondistiUed process (29—31), which may involve a subsequent distillation step (30), and in which the phosphoms is often cleaned up prior to use (30—32). For either process, the Hquid phosphoms sulfide product is soHdified, and usually sized to form a commercial material. 

As the polymer molecular weight increases, so does the melt viscosity, and the power to the stirrer drive is monitored so that an end point can be determined for each batch. When the desired melt viscosity is reached, the molten polymer is discharged through a bottom valve, often under positive pressure of the blanketing gas, and extmded as a ribbon or as thick strands which are water-quenched and chopped continuously by a set of mechanical knives. Large amounts of PET are also made by continuous polymerization processes. PBT is made both by batch and continuous polymerization processes (79—81). 

The reaction is exothermic reaction rates decrease with increased carbon number of the oxide (ethylene oxide > propylene oxide > butylene oxide). The ammonia—oxide ratio determines the product spht among the mono-, di-, and trialkanolamines. A high ammonia to oxide ratio favors monoproduction a low ammonia to oxide ratio favors trialkanolamine production. Mono- and dialkanolamines can also be recycled to the reactor to increase di-or trialkanolamine production. Mono- and dialkanolamines can also be converted to trialkanolamines by reaction of the mono- and di- with oxide in batch reactors. In all cases, the reaction is mn with excess ammonia to prevent unreacted oxide from leaving the reactor. 

The intrinsic rejection and maximum obtainable water flux of different membranes can be easily evaluated in a stirred batch system. A typical batch unit (42) is shown in Figure 5. A continuous system is needed for full-scale system design and to determine the effects of hydrodynamic variables and fouling in different module configurations. A typical laboratory/pilot-scale continuous unit using computer control and on-line data acquisition is shown in Figure 6. 

---