Continuous paste mixer

Teck Inc. has developed a continuous paste mixer to produce lead-acid battery paste over a broad output and chemistry range. 

A continuous paste mixer provides the following benefits ... 

FIGURE 7.12 Continuous paste mixer. (From Battery Technology Solutions Inc. Available at http //www.batechsol.com.)... 

Pastes. For blending of viscous pastes, mixers are classified as batch or continuous. Most convection-type mixers for dry soHds are also used for thick pastes. 

Charge 40 parts of (1) to suitable paste mixer. Run mixer continuously while adding (2), with further small increments of (1) if necessary, to avoid overloading the mixer drive the object is to blend at heaviest practicable consistency to provide thorough dispersion. Continue mixing until fully dispersed and smooth. 

During paste preparation, exothermic reactions proceed which cause the temperature in the paste mixer to rise. In order to obtain reproducibly a paste with definite phase composition and crystal morphology, which would ensure high and stable battery performance, the temperature in the mixer should be monitored and controlled continuously throughout the process of paste preparation. 

Paste preparation starts with the introduction of fibres or (fibres + 4BS nucleants) in the paste mixer. Then water is added and the suspension is mixed for 1 min. The next step is to add the leady oxide (LO) and mix for another 3—4 min until a homogenous mass is obtained. Then the sulphuric acid solution is added slowly, for about 10—12 min. The temperature is monitored continuously and kept below 50 °C. If needed, the cooling system of the paste mixer is activated. After adding the whole amount of H2SO4 solution, the paste is mixed for 15 more minutes to allow the 3BS crystals to grow. Finally, samples are taken from the paste to measure its density and consistency. If these parameters meet the technological requirements, the paste... 

Figure 10.15. Some mixers and blenders for powders and pastes, (a) Ribbon blender for powders, (b) Flow pattern in a double cone blender rotating on a horizontal axis, (c) Twin shell (Vee-type) agglomerate breaking and liquid injection are shown on the broken line, (d) Twin rotor available with jacket and hollow screws for heat transfer, (e) Batch muller. (f) Twin mullers operated continuously, (g) Double-arm mixer and kneader (Baker-Perkins Inc.), (h) Some types of blades for the double-arm kneader (Baker—Perkins Irtc.).

Miscellaneous Continuous Mixers Because of the diversity of material properties and process applications involving viscous fluids, pastes, and doughs, the types of mixers are almost as diverse. 

Fig. 4.3. Here the group of solvent extraction stages used to extract the desired component from feed has been designated as the extracting section, and the group tised to wash this component back into the aqueous phase as the stripping section. In practice, each section may be either batteries of mixers and separators as shown in Fig. 4.2, in wdiich phases are alternatively mixed and separated, or countercurrent columns, in which the two phases flow past one another in continuous contact and continuously exchange material.

To precipitate the desired potassium sulfonate, the filtrate [collected in receivers (3 and 3A), together with strong wash liquor] is transferred to the 20,000-liter rubber-lined precipitation tank (4) and the concentrated KCl solution is added. The temperature is maintained at 85°C to keep the byproduct 1,5-disulfonate in solution. The precipitated potassium sulfonate is isolated by continuous filtration on a rubber-covered rotary filter (5 and 6), where it is washed with 5 per cent potassium chloride solution and discharged at approximately 45 per hent solids content into a horizontal trough mixer (7), from which it is pumped to one of two 13,000-liter brick-lined paste storage tanks (8). The paste content is adjusted to 35 per cent solids and brought to neutrality with a small amount of soda ash solution, after which it is pumped either to an autoclave for conversion to 1-amino-anthraquinone or to the chlorinators for conversion to 1-chloroanthra-quinone. 

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