Continuous plate production

Single plates are usually cured in special devices (curing ovens or curing chambers, cf., e.g., [25] ) that control humidity as well as temperature. In continuous plate production, the drying of the pasted ribbon is correspondingly controlled. Furthermore, in continuous manufacture final curing can occur after the plates are separated and inserted into the containers. 

Fig. 13.21. Expanded-metal grid ribbon used for continuous plate production of automotive batteries.

Expanded metal grid strip used for continuous plate production in the automotive battery... 

Continuous plating of wire and strip is, unlike the preceding techniques, a prefabrication process. The production of tinplate is the largest scale continuous operation, but any electrodeposit may be applied this way. Subsequent fabrication processes arc likely to damage the coating, so that pre-coating is best reserved for ductile coatings which are anodic to the substrate in service, as is the case for tin. 

The Fujiwara Brewing Machinery Company of Japan has developed a piece of equipment for continuous koji production which is shaped like a rotating or circular plate. When the plate rotates in the horizontal plane, the solid substrate tumbles about, thus contacting the air which enters through the holes in the plate [52,73-74]. 

The procedure is continued, plate by plate, until a plate is reached at which a liquid of feed composition is being intro liced a total of four plates is required. The results just obtained can be applied to any size unit, as long as direct multiples of the feed and product rates and holdup volumes are used. 

General scheme of the most common methods for continuous grid and plate production. 

There is no doubt that the continuous grid/plate production technology is most convenient for the manufacture of standard plates for SLI batteries and will certainly compete with the existing casting methods. However, the latter will preserve positions in the battery industry, provided the process is sufficiently flexible with regard to grid size/geometry. 

With this brief description of the CSM grid technology we will complete the overview of the most common grid alloys and grid design principles, and will continue further with the plate production processes. 

The major plastics that are plated and their characteristics for plating are identified in Table P.6. Improvements are being made continuously, especially in ABS and polypropylene, which yield generally lower product costs. Aside from the commercial plastics described in Table P.6, excellent plated products can be obtained with other plastics. Notable is the plating of TFE fluorocarbon, where otherwise unachievable electrical products of high quality are reproducibly made. Examples of applications are printed circuit boards, corona-free capacitors, and low-loss, high frequency electronic components. 

Continuous processes for copolymer production were developed initially for the microporous resins. The system generally involves injecting the monomer mix into the aqueous phase through orifice plates. Droplet size is controUed by the diameter of the holes in the plate and the rate at which the monomer is injected into the aqueous phase. The continuous process produces copolymer beads which have greater uniformity in size than those produced in batches. 

Many methods for the conversion of acid copolymers to ionomers have been described by Du Pont (27,28). The chemistry involved is simple when cations such as sodium or potassium are involved, but conditions must be controlled to obtain uniform products. Solutions of sodium hydroxide or methoxide can be fed to the acid copolymer melt, using a high shear device such as a two-roU mill to achieve uniformity. AH volatile by-products are easily removed during the conversion, which is mn at about 150°C. A continuous process has been described, using two extmders, the first designed to plasticate the feed polymer and mix it rapidly with the metal compound, eg, zinc oxide, at 160°C (28). Acetic acid is pumped into the melt to function as an activator. Volatiles are removed in an extraction-extmder which follows the reactor-extmder, and the anhydrous melt emerges through a die-plate as strands which are cut into pellets. 

Containerized ice cream is hardened on a stationary or continuous refrigerated plate-contact hardener or by convection air blast as the product is carried on a conveyor or through a tunnel. Air temperatures for hardening are —40 to —50° C. The temperature at the center of the container as well as the storage temperature should be <—26°C. Approximately one-half of the heat is removed at the freezer and the remainder in the hardening process. 

The market for fused siUca started ia 1906 with the sale of siUca muffles and pipes. That same year resulted ia the iacorporatioa of the Thermal Syadicate Ltd. Siace that time, worldwide sale of vitreous siUca material and fabricated products has continued to grow. The sales of vitreous siUca iagots, tubes, rods, plates, fabricated products, photomask blanks, cmcibles, and optics was estimated to be between 800 million to 1 biUion ia 1995. These figures do aot, however, take iato accouat the optical waveguide market based oa fused siUca technology. 

Titanium disulfide can also be made by pyrolysis of titanium trisulfide at 550°C. A continuous process based on the reaction between titanium tetrachloride vapor and dry, oxygen-free hydrogen sulfide has been developed at pilot scale (173). The preheated reactants ate fed iato a tubular reactor at approximately 500°C. The product particles comprise orthogonally intersecting hexagonal plates or plate segments and have a relatively high surface area (>4 /g), quite different from the flat platelets produced from the reaction between titanium metal and sulfur vapor. The powder, reported to be stable to... 

Active Dry Yeast (ADY). The production of active dry yeast is very similar to the production of compressed yeast. However, a different strain of yeast is used and the nitrogen content is reduced to 7% of soHds compared with 8—9% for compressed yeast. The press cake made with the active dry yeast strain is extmded through a perforated plate in the form of thin strands with a diameter of 2—3 mm and a length of 3—10 mm. The strands are dried on endless belts of steel mesh in drying chambers (a continuous process) or in roto-louvre dryers (a batch process), with the temperature kept below 40°C. Drying time in drying chambers is 3—4 h and in roto-louvre dryers is 6 h or more. The final moisture level attained is 7.5—8%. 

Potassium cyanide [151 -50-8] KCN, a white crystalline, deUquescent soHd, was initially used as a flux, andlater for electroplating, which is the single greatest use in the 1990s. The demand for potassium cyanide was met by the ferrocyanide process until the latter part of the nineteenth century, when the extraordinary demands of the gold mining industry for alkah cyanide resulted in the development of direct synthesis processes. When cheaper sodium cyanide became available, potassium cyanide was displaced in many uses. With the decline in the use of alkah cyanides for plating the demand for potassium cyanide continues to decline. The total world production in 1990 was estimated at about 4500 t, down from 7300 t in 1976. 

The Separation Stage. A fundamental quantity, a, exists in all stochastic separation processes, and is an index of the steady-state separation that can be attained in an element of the process equipment. The numerical value of a is developed for each process under consideration in the subsequent sections. The separation stage, which in a continuous separation process is called the transfer unit or equivalent theoretical plate, may be considered as a device separating a feed stream, or streams, into two product streams, often called heads and tails, or product and waste, such that the concentrations of the components in the two effluent streams are related by the quantity, d. For the case of the separation of a binary mixture this relationship is... 

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