Equipment drying chambers

VAC TRAX is different from other thermal desorption processes in that it is a vacuum dryer. By sealing the drying chamber and reducing the air pressure, a vacuum is created. The vacuum allows a much lower temperature to be used in the dryer, enabling the use of smaller, more transportable equipment. 

The drying chamber is rectangular in shape and is equipped with a door. It is vacuum- and pressure-resistant and designed for the freeze-drying process and sterilization with pure steam at an overpressure of (provide value) bar corresponding to (provide temperature in °C). 

This system is designed to clean the freeze-drying chamber and condenser with water for injection. Spraying with WFI at an inlet temperature of (provide value) °C effects cleaning of the chamber. There are jet rods installed in the drying chamber and the pathway to the condenser. The position of these rods as well as the distribution of the spray jets provides good coverage all over the interior surfaces of the chamber with WFI. The jet rods are equipped with full cone and flat jet nozzles. 

Other systems make use of the sticking tendency of acid whey. Partially dried whey powder coats the inner wall of the drying chamber, whence it falls when the crystalline lactose content of the powder becomes high. However, sticking of the product on the hot metal surfaces can be a problem unless sufficient moisture is present so that lactose crystallization proceeds to the point where the powder no longer adheres to the equipment (Pallansch 1973). 

Vacuum Pumps. The function of these pumps is to evacuate the drying chamber quickly without allowing the prefrozen material to melt—and thereafter to reduce the pressure progressively to the desired vacuum and maintain it at Ihis level by removing the noncondensablc gases. The vacuum equipment can be cither an oil-sealed rotary vacuum pump, or a multistage stream-ejector system. 

The double promoter process involves the successive application of liquid promoter solutions of vinyltrichlorosilane (VTS) and 3-chloropropyltrimethoxy-silane followed by successive cure cycles in dry N2 at 90°C after each application and before photoresist application. The double promoter process evolved because it was felt that the silane reaction with the SiOH surface groups of low temperature oxides was incomplete for a single promoter application, and because vapor silane equipment did not exist at that time. Interestingly, a double HMDS liquid promoter process failed to yield adequate adhesion as well. Later in time, the successful but somewhat complex double promoter process was replaced by the vapor phase HMDS process in the Star 1000 (or 2000) then superior resist image adhesion was obtained on all four oxide substrates with all the photoresists tested. Before the advent of the HMDS vapor priming in standalone or wafer track equipment module chambers, liquid priming solutions were widely used, especially in development areas. 

The freeze-drying chamber and the condenser are calculated to resist a required sterilization pressure (see technical specifications). For this purpose, the equipment is designed following ASME, CODAP, or equivalent requirements and submitted according to the regulation and control set by the Lloyd Register or an equivalent. 

Most freeze-dried pharmaceuticals—and, of course, all injectable products—need to be sterile. Until now, the usual rule to achieve that goal has been to start with a sterile solution and, from there on, to carry out an entirely sterile process. Indeed, the time is over when the manufacturers could add a 1/10,000 merthiolate to get rid of an accidental contamination. Today all freeze-dryers have their cabinets opening within a sterile room while the machinery is sitting behind the wall in the engine room. Moreover, the drying chambers are all equipped with clean-in-place (CIP) systems and can be sterilized by pressure steam before each operation. Finally, those products that are prepared in vials are sealed directly within the chamber thanks to moving pressure plates that drive the stoppers tight into the neck of the vials. 

The freeze-dryer is equipped with a mechanical pumping system that removes noncondensable gases. With oil sealed mechanical pumps, one should be careful to operate the dryer so that no hydrocarbon vapours from the pump can backstream into the drying chamber. 

Typical droplet lifetimes and hence particle formation rates can occur over a range of time.scales from milliseconds to minutes. Particle formation time is controlled by both the initial liquid droplet size and evaporation rate. The latter is dictated by the heat transfer to the droplet, mass transfer of the vapor away from the droplet into the process gas stream and the specific formulation components. The rate of particle formation is a key parameter which dictates the size of the drying chamber, and hence the scale of equipment required to produce a desired particle size at the target production rate. 

In two-point discharge, primary discharge of a coarse powder fraction is achieved by gravity from the base of the drying chamber. The fine fraction is recovered by secondary equipment downstream of the chamber air exit. 

The method of removing the liquid from the slurry is critical. Spray drying determines the distribution of the oxide in the dry particles of oxide and catalyst, catalyst precursor or catalyst support to provide the product of this invention. The spray drying may be carried using conventional spray drying techniques and equipment. The chamber product from the chamber of the spray dryer is typically made up of porous spheroidal particles with diameters of about 30 to about 300 [jum. The cyclone product collected from the cyclone of the spray dryer is made up of porous spheroidal particles with somewhat smaller diameters. These spray dried particles may be sieved to obtain a fraction of particles with a narrower size distribution. The spray dried spheroidal particles are referred to herein as microspheres. As is well-known in the spray drying art, many of the porous microspheres produced have a void in the center with one or two openings to the outside. Such particles are referred to in the art as Amphora I-type and Amphora Il-type particles, respectively. 

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