Slurry solution

Cake Filters - These are filters that are used to remove large amounts of solids from a slurry solution. They would normally be seen in biotechnology in the primary clarification of fermentation batches and in a variety of solids removal steps seen in the production of drugs via organic synthesis. 

In the manufacturing of USY catalyst, the zeolite, clay, and binder are slurried together. If the binder is not active, an alumina component having catalytic properties may also be added. The well-mixed slurry solution is then fed to a spray dryer. The function of a spray dryer is to form microspheres by evaporating the slurry solution, through the use of atomizers, in the presence of hot air. The type of spray dr er and the drying conditions determine the size and distribution of catalyst particles. 

Spray dryers are shown in Figure 8.13d. Here, a liquid or slurry solution is sprayed as fine droplets into a hot gas stream. The feed to the dryer must be pumpable to obtain the high pressures required by the atomizer. The product tends to be light, porous particles. An important advantage of the spray dryer is that the product is exposed to the hot gas for a short period. Also, the evaporation of the liquid from the spray keeps the product temperature low, even in the presence of hot gases. Spray dryers are thus particularly suited to products that are sensitive to thermal decomposition, such as food products. 

The cross-flow filtration method is applied mainly to hyper- and ultrafiltration as well as to some microfiltration.8 In cross-flow filtration the slurry solution or suspension fed to the filter flows parallel to the filter medium or membrane. The filtration product (permeate or filtrate) leaves the filtration module at right angles to the filter medium (the membrane). The traditional perpendicular flow filtration (where the flow of the suspension is directed at right angles to the filter medium and the permeate leaves the filter medium in the same direction) entails filter cake buildup, whereas cross-flow filtration is intended to prevent such filter... 

Absorbent availability could have significant impact upon process costs. Most spent alkali streams could be used depending on the other impurities present. Corrosion or precipitation tests should be considered for these cases. Any other readily available alkali, like sodium carbonate or sodium hychloride, should be considered. Slurry solutions of lime or limestone should be avoided because of past operating problems. 

The heats of reaction/solution of some reagents as hydrolysis/dissolution takes place can cause substantial elevation in slurry/solution temperatures, particularly at a large scale where heat transfer and radiative cooUng are not nearly as efficient as it is in small laboratory vessels. Other reagents, such as certain sodium alumi-nates and particularly reagents that are not freshly prepared, may need elevated temperatures for full dissolution in water. These hot or very warm solutions can adversely affect early nucleation conditions in some zeoHte syntheses. Hot reagent solutions and mixtures are sometimes cooled prior to their addition to other reagents to better control the early reactions and speciation of aluminosilicate and silicate precursors. 

The forward reaction is favored by the alkaline slurry solutions which result in breakage of the Si—O bonds. In metal CMP, oxidizing slurries are often used, resulting in faster removal rates. Since the contributions of the chemical and mechanical components are not well known, modeling efforts have focused on empirical approaches guided by physical intuition of process mechanisms. 

The slurry solution plays a different role between oxide (as a hydrolizer) and metal (as an oxidizer) slurries. It is more complex in metal than in oxide, because traditionally, oxide slurry is used only for polishing oxide (for ILD, for example), whereas the metal slurry (for tungsten, for example) is used to polish tungsten, titanium nitride, titanium, and oxide. Accordingly, the choice of a metal slurry oxidizer must first satisfy the requirement of the selectivities between each different deposited film. Selection of solution for oxide slurry does not have such constraints. 

The lithiated polyethylene copolymer was then suspended in hexane or THF solvent. The graft-from reactions were carried out in slurry solution by reacting the lithiated polyethylene copolymer with anionic polymerizable monomers, such as styrene and p-methylstyrene. After certain reaction time, 10 ml of isopropanol was added to terminate the graft-from reaction. The precipitated polymer was filtered and then subjected to fractionation. Good solvents for backbone and side chain polymers were used during the fractionization, using a Soxhlet apparatus under N2 for 24 hours. The soluble fractions were isolated by vacuum-removal of solvent. Usually, the total soluble fractions were less than 5 % of the product. The major insoluble fraction was PE graft copolymer, which was completely soluble in xylene or trichlorobenzene at elevated temperatures. 

The low-pressure processes, such as slurry, solution, or gas phase, can produce types I, II, III, and IV polyethylenes. Catalysts used in... 

The technologies that have been developed for the production of polyolefins, olefin homopolymers and copolymers are slurry, solution and gas-phase polymerisation bulk polymerisation of propylene in the liquid monomer as a special case of the slurry process has also emerged. The fundamental differences in the various olefin polymerisation processes reflect the different approaches that have been devised to remove the substantial heat of polymerisation. In addition, processes can be operated in a batch or a continuous mode. In the batch process the reagents are loaded into a polymerisation vessel, the polymer forms and the vessel is emptied before a new charge of reagents is introduced. In the continuous process, the catalyst precursor, activator and other necessary... 

The adhesion forces of silica and alumina particles in the DI water and slurry solution were measured by AFM and are shown in Fig. 16.27 [66]. The smallest adhesion force, 0.38 nN, was observed between the copper surface and alumina particles in a citric acid solution at pH 6. The largest adhesion force of alumina particles, 5.83 nN, was measured in DI water. 

FIGURE 16.29 The removal rate of copper in various slurry solutions. 

TABLE 16.3 The Roughness and Depth of Scratches on the Copper Surface After Polishing with Alnminahased and Silicahased Slurry Solutions. 

H2O2, and NH4OH. This suggests that a high copper removal rate requires not only the mechanical reaction but also the chemical reaction. Abrasives and chemicals in the slurry solutions continuously accelerate oxidation, etching, and abrasion of copper surface by chemical and mechanical effects. Although the lowest friction force was observed in the alumina based slurry with the addition of citric acid, the highest removal rate of copper was observed in this slurry due to the chemical reaction with copper surface. The smallest adhesion force resulted in the lowest friction force in the alumina-based slurry with the addition of citric acid. 

Sample preparation is a critical step of method development that the analyst must investigate. For example, the analyst should investigate if centrifugation (determining the optimal rpm and time) shaking and/or filtration of the sample is needed, especially if there are insoluble components in the sample. This is usually more prevalent with excipient/DS mixtures and with slurry solutions obtained during the synthesis steps of the API. Syringe filters... 

Chemical Durability and Reactivity of the Pad The pad must be chemically stable in the slurry solution and must not react with the slurry, cleaning solutions, or the film being polished. 

Figure 4.43 Titanium polish rate in I vol% NH4 OH sluiry as a function of Cu(NOj)2 concentration. The increase in polish rate is due to an electrochemical interaction of the titanium metal with copper ions in the slurry solution. (12S mm wafers polished on Strasbaugh 6CU polisher with 2.S wt% alumina hbrasive, 15 kPA, and 130 cm/sec.)...

In order for the copper ion to deposit onto the copper metal, an electron current must flow from the site of the titanium oxidation to the site of copper reduction. This electron transfer process is shown in Figure 4.50. The titanium metal acts as a local anode, while the copper metal acts as a local cathode. We observe this interaction to occur within a distance of approximately 20-40 pm of a copper structure and believe that this distance is limited by the conductivity of the slurry solution. The conductivity of a 1 vol% NH4OH solution is approximately 800 Q cm. 

Kaufinan et al. describe a successful tungsten CMP process as a competition between the formation and removal of a surface layer of WO3 that forms naturally in the slurry solution. A bare tungsten surface is not thermodynamically stable in the low pH slurry described by Kaufman et al., and the chemicals quickly oxidize the tungsten surface to WO3 according to the reduction-oxidation reaction ... 

Manual venting of digester vessels to maximize the residence time of a slurry solution was automated using a dual-conductivity-probe relay system. 

A slurry solution is fed into the top and out of the bottom of each digester vessel in a train. As the slurry flows through the vessels, the resultant pressure drop causes some flashing of the liquid and in-gassing of the digester vessels, which displaces some of the liquid in the... 

Physical state (homo- — Type of metal — Type (slurry, solution. — Temperature — Catalytic activity... 

Slurry solutions can be nebulised and introduced as an aerosol to the plasma source similar to that for clear solutions and the solvent containing the particles also assists in transporting them for elemental analysis. Care must be taken in avoiding the tendency to form agglomerates and samples must be kept stirred or shaken using an ultrasonic bath prior to nebulisation. Samples of products containing very small particles, e.g. fillers in... 

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