Pastes mixing

The oxide exiting either the Barton or ball mill reactor is conveyed by an air stream to separating equipment, ie, settling tank, cyclone, and baghouse, after which it is stored in large hoppers or dmmmed for use in paste mixing. Purity of the lead feed stock is extremely critical because minute quantities of some impurities can either accelerate or slow the oxidation reaction markedly. Detailed discussions of the oxide-making process and product are contained in references 55—57. 

Paste Mixing. The active materials for both positive and negative plates are made from the identical base materials. Lead oxide, fibers, water, and a dilute solution of sulfuric acid are combined in an agitated batch mixer or reactor to form a pastelike mixture of lead sulfates, the normal, tribasic, and tetrabasic sulfates, plus PbO, water, and free lead. The positive and negative pastes differ only in additives to the base mixture. Organic expanders, barium sulfate [7727-43-7] BaSO carbon, and occasionally mineral oil are added to the negative paste. Red lead [1314-41 -6] or minium, Pb O, is sometimes added to the positive mix. The paste for both electrodes is characterized by cube weight or density, penetration, and raw plate density. 

Since paste mixing is not within the scope of this section, such widely used paste mixers as the sigma blade and banbury types will not be covered here but instead are discussed in Sec. IS. 

Releases fo Land. Wastewater from the grid paste mixing scrubber is discharged to a surface impoundment and evaporated. Aithough your facility historically has removed lead sludge Irom the surface Impoundment each year, this has not been done for the past two years, as process changes have caused the sludge to accumulate more slowly than In previous years. Therefore, the impoundment must be considered an on-site land disposal unit, and releases to the impoundment must be reported in Part III, Section 5.5.1, of the form, and not in Part III, Section 5.3. 

Paste mixing means the addition of sulfuric acid and water. The result is a fairly stiff paste with a density between 1.1 and 1.4gcm 3 containing 8-12wt% of lead sulfate. The water content of thus mix determines the porosity of the active material achievable later (cf. "curing" below). In the paste, a mixture of lead sulfate and basic lead sulfate is formed (cf. Table 1). In the usual mixing process between room temperature and 50 °C, tribasic lead sulfate is formed. The generation of the tetrabasic... 

Test results ( , ) for several candidate materiaIs (Table III) are reported which span the range of energetic capacity. Those values which exceed the threshold are highly susoect and have been known to result in serious fires in the past. Mix No. 1, (M49A1, Trip Flare Mixture) is a "safe" mixture that is insensitive to electrical spark, impact, and friction. It does not have a fast bum rate on the Vee Block tester and it has a low pressure-rate-of-rise. 

The catalysts were prepared using 50 wt.% of ZSM-5 with varying level of ion exchange. The zeolite was subjected to two- or one-step treatment with ammonium chloride solution. Zeolite was incorporated by.a method in which zeolite and aluminium hydroxide were pasted, mixed and extruded. The catalysts contained 8 or 12 wt % of NiO 4 wt.% were introduced in the course of the carrier forming process, the remaining portion of nickel being loaded by impregnation. 

Electrodes made with carbon or graphite paste mixed with a hydro-phobic diluent such as Nujol, paraffin, silicone rubber, epoxy resin, Teflon, or Kel-F, have also been used. Comparative studies between the various types of carbon paste electrode have been carried out11. 

Separate meats from shells, grind twice at least 250 g in a food chopper equipped with 3 mm plate openings or other suitable devices that give a smooth homogeneous paste without loss of oil. Mix well and store in an airtight container. For butters and pastes, mix, warming semi-solid products. 

Mix the solid substance (or, preferably, silicic acid isolated by treatment of the silicate with ammonium chloride solution) with one-third of its weight of calcium fluoride in a small lead (or platinum) capsule, and add sufficient concentrated sulphuric acid to form a thin paste mix the contents of the capsule with a stout platinum wire. Warm gently (FUME CUPBOARD) and hold close above the mixture a loop of platinum wire supporting a drop of water. The drop of water will become turbid, due to the hydrolysis of the silicon tetrafluoride absorbed. 

Halse and Pratt (H57) reported SEM observations on pastes hydrated at various temperatures. In those hydrated at 8°C or 23 C, the main feature was fibrous material that was considered to be hydrous alumina, but which could also have been partly dehydrated CAH,q. The hydrating grains of cement were surrounded by shells of hydration products, from w hich they tended to become separated in a manner similar to that observed with Portland cement pastes (Section 7.4.2) though the authors recognized that this could have been partly due to dehydration. Two-day-old pastes hydrated at 40"C showed spheroidal particles of CjAH and thin, flaky plates of gibbsite. In pastes mixed with sea water, hydration took place more slowly, but no other effects on microstructural development were observed. 

Paste Mix of clay and other materials used to make pottery. 

BS crystals are obtained during paste preparation at temperatures higher than 80°C [51]. This technology yields long, well-shaped, 4BS crystals with a thickness that varies depending on the time of paste mixing and the temperature of paste preparation. When the paste is mixed for 10-20 min, the crystals are 2-4 pm thick and require 20-30 h for formation. The PAM... 

Particles of lead dioxide in lead monoxide, such as those formed in a ball-mill, can be formed by treating the oxide with ozone before paste mixing [49]. The use of persulfate [50-53] and peroxides [54] to effect the partial conversion of lead oxide in the paste to lead dioxide has also been proposed. A proprietary process for treating the surfaces of unformed plates with ozone gas produced a thin coating of lead dioxide, which enhanced formation [55,56]. Much lower quantities of lead dioxide are needed with this approach than when red lead is added to the plate, and the normal battery paste mix can be used. Dipping or spraying the plate with a persulfate solution has also been adopted to oxidize the surface PbO to conductive Pb02 [57]. 

Sulfate salts have been introduced into the positive paste of VRLA cells during the paste-mixing process. In a recent study [65], sodium sulfate was added to positive pastes at 0, 0.01, 0.05, 1, and 2M levels (note, the authors did not explain how the molarity levels were calculated). The plates were cured at 85°C to form tetrabasic lead sulfate and a-PbO. The tetrabasic lead sulfate crystals had sizes of... 

In the industrial process, the pH range for desulfurization is 8-8.5, and the temperature is usually 35-40°C. As the reaction progresses and lead carbonate is produced, the paste mix becomes increasingly viscous and difficult to stir. It is... 

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