Suspension process steps

The advantage of suspension processes over mass processes is the excellent temperature control that can be obtained through the suspending medium, water. This allows for rapid heat removal and shorter polymerization times. It reduces or eliminates hot spots or heat-kicks characteristic of mass reactors. It also allows the polymerization to be driven very close to completion so that no devolatilization step is normally required. 

Chemical engineers could also work to devise processes to improve the flow characteristics of powders after they are formed. Such research would help control agglomeration of particles in subsequent processing steps as well as facilitate the production of compacted ceramic preforms. For example, gas-solid chemical reactions might be used to tailor the chemical composition of powders. As another example, better methods of componnding powders with binders might be achieved by processes that mix powders with suitable binders in a liquid and then spray dry the resulting suspension. 

The initial processing steps are determined to a large extent by the location of the product species, and they generally consist of cell/broth separation and/or cell debris removal. For products retained within the biomass during production, it is first necessary to concentrate the cell suspension before homogenization or chemical treatment to release the product. Clarification to remove the suspended solids is the process goal at this stage. 

After this, the obtained suspension was processed in a homoge-nizer (Emulsiflex-C5, Avestin Inc., Ottawa) operated at a pressure at the homogenization valve of 300 kPa. The particle size was 230 nm after a homogenization period of 30 minutes. The final process step was extrusion using polycarbonate membrane Alters with a pore size of 100 nm installed in the... 

Process flowcharts. A flow diagram should indicate the process steps and addition of raw materials. If possible, major equipment and special environmental conditions may be included in the flowchart. In-process tests may also be included. A second flowchart for activities, raw material suppliers, shipments, and testing would also assist in the overall picture of the aerosol manufacturing scheme, especially for multiple site or third-party activities. An example of a process flowchart for a fictitious suspension product (2160.4-kg batch size for 100,000 units) is shown in Figure 6. 

The suspension process is practiced by only a few companies because it offers a higher degree of production control and product engineering during polymerization step. This process suspends the water-based reactant in a hydrocarbon-based solvent. The net result is that the suspension polymerization creates the primary polymer particle in the reactor rather than mechanically in postreactions stages. Performance enhancements can also be during or just after the reaction stage. 

Integrative protein recovery operations are supposed to tolerate particle-containing biological suspensions as initial feedstock and to deliver a clarified product concentrate which can be transferred to further purification steps. Ideally, a first fractionation of the protein matrix contained in the feed is performed as well, thus combining clarification, concentration, and capture in a single process step. 

ABB Lummus Global/BP Amoco Polystyrene, expandable Styrene One-step batch suspension process with high reactor productivity 1 1997... 

After elution from the immunosorbent, the purified protein must usually be isolated from the elution buffer either as a dry powder, concentrated solution or a suspension. This step may be required for stability, packaging, or to make it suitable for administration to humans or animals. Here the selection of an antibody which will allow the dissociation of the antibody-antigen complex under appropriate conditions for the final processing step is important. If the final step is freeze-drying, a volatile elution buffer such as acetic acid or ammonium hydroxide would be appropriate. 

In the relentless quest for ever faster computer circuitry, the dielectric constant of the insulating layers between conductors on the chip is becoming a major issue. This constant should be as small as possible while the mechanical properties of the dielectric material must withstand the subsequent processing steps and ensure the integrity of the computer microprocessor. Nanoscale zeolite crystals, particularly pure silica zeolites, have been proposed as candidates for thin films with low dielectric constant (low k). As an example, suspensions of nanoscale crystals of the pure zeolite silicalite-1 (MFI-typc) were used for spin-on deposition of thin dielectric layers.[101] The as-deposited films were subsequently calcined at 450 °C in order to remove organic molecules and to consolidate the films. The authors report low dielectric constants (although the adsorption of humidity must be controlled) and satisfactory mechanical properties of their films. 

---