Superheated water spray

Replacing sterilizers that operate by one set of principles with sterilizers that operate by another principle (e.g., substituting a gravity displacement steam process with a process using superheated water spray). 

Accordingly, a dual control principle is provided that acts independently on both parameters. Two methods currently in use are superheated water spray and steam-air mixture. 

Fig. 5 Superheated water spray autoclave simplified P. I.D. (Adapted from Ref.. )...

With steam-air autoclaves, blushing of PVC bags is generally less intense than with superheated water spray autoclaves and essentially affects only the areas where the bags rest on the supporting racks. Among... 

Fig. 9 Two superheated water spray autoclaves with a chamber capacity of approximately 4m, with a rotating load and sliding double doors. The man-machine interface of the process controller is not shown. The automated loading/unloading systems, frequently used with large sterilizers to allow faster loading and unloading operations, are shown instead. (Adapted from Ref.t l.)...

Current pharmaceutical production practice uses substantially three moist-heat sterilization processes 1) pressurized saturated steam 2) superheated water and 3) steam-air mixture. Process 1 is the traditional multipurpose process, which obviously uses pure pressurized saturated steam as sterilizing medium. Processes 2 and 3 are so-called counterpressure processes they were introduced in pharmaceutical production practice approximately 20 years ago and, respectively, use a spray superheated water and a homogeneous... 

The flue gas is cooled to about 600°F. by passage through a waste-heat steam boiler, and further cooled to 400°F. or lower by injecting a spray of superheated water, before introduction into the Cottrell (234). A 20-25 vol. % concentration of water vapor is maintained in the gas in order to minimize arcing. Injection of a small amount of ammonia, about 0.005% by weight of the flue gas, has also been found beneficial. 

Steam can be contaminated with soHds even when carryover is not occurring. Contaminated spray attemperating water, used to control superheated steam temperature at the turbine inlet, can introduce soHds into steam. A heat exchanger coil may be placed in the boiler mud dmm to provide attemperation of the superheated steam. Because the mud dmm is at a higher pressure than superheated steam, contamination will occur if leaks develop in the cod. 

The control of superheated steam temperature is achieved by attem-peration, using either surface (heat exchange) or spray (direct contact) attemperators. The spray type, which requires the steam to be sprayed with water, is the most widely used, and a schematic is shown in Figure 3.1. 

In entrainer sublimation, an entrainer gas is blown into the vaporisation chamber of a sublimer in order to increase the vapour flowrate to the condensing equipment, thereby increasing the yield. Air is the most commonly used entrainer, though superheated steam can be employed for substances such as anthracene that are relatively insoluble in water. If steam is used, the vapour may be cooled and condensed by direct contact with a spray of cold water. Although the recovery of the sublimate is efficient, the product is wet. The use of an entrainer gas in a sublimation process also provides the heat needed for sublimation and an efficient means of temperature control. If necessary, it may also provide dilution for the fractional condensation at the desublimation stage. Entrainer sublimation, whether by gas flow over a static bed of solid particles or through a fluidised bed, is ideally suited to continuous operation. 

In a desuperheater, water at 2,900 kPa and 40°C is sprayed into a stream of superheated s at 2,800 kPa and 325°C in an amount such that a single stream of saturated-vapor steam at 2,7001 flows from the desuperheater at the rate of 10 kg s 1. Assuming adiabatic operation, what is the flow rate of the water What is AS,nlal for the process What is the irreversible feature of the pr... 

The mother-liquors from washing the salts, in which bromine exists in the form of bromides, is sprayed in the form of a fine rain from the top of a tower filled with fragments of a refractory material, while into the bottom of the tower is led a current of chlorine and water vapour. By this means bromine is displaced from the bromide. The liquid which collects at the bottom of the tower is rich in bromine and passes into another vessel where it is distilled by means of superheated steam. The bromine which is vaporised passes from the top of the tower into a lead vessel where it is purified from the chlorine it contains by heating. 

The de-superheater has specially designed nozzles for spraying a controlled amount of treated water in the superheated steam. An enquiry for steam de-superheater shall include the following ... 

Each section of the pasteuriser will have a water tank, a water pump and spraying system (spray nozzles or spray pans). A float valve and overflow maintain a constant water level in the tanks. Heaters bring the water to the required temperatures on start up and for adjustment, though during normal operation are only needed in the superheating and holding sections. 

The de-superheater can generate additional steam by spraying an optimum amount of water through specially designed nozzles in the superheated steam. Following points should be considered while procuring a steam de-supeiheater ... 

Example 19.4 shows that the reboiler operation requires that the pressure of the boil-up stream be increased. This is not the only possible alternative. All that is necessary is that the temperature difference be 21.7°C. This could be accomplished by reducing the temperature of the steam to 163.4°C. In most chemical plants, steam is available at discrete pressures, and the steam used here is typical of medium-pressure steam. Low-pressure steam would be at too low a tenperature to work in the scaled-down column. However, the pressure and temperature of medium-pressure steam could be reduced if there were a throtding valve in the steam feed line to reduce the steam pressure. The resulting steam would be superheated, so desuperheating would also be necessary. This could be acconplished by spraying water into the superheated steam. A change in a utility stream is almost always preferred to a change in a process stream. The condenser is now analyzed in Examle 19.5. 

When steam is superheated, its enthalpy becomes a function of temperature and is relatively independent of pressure. Steam-temperature control is often sought by redistributing the combustion gases in the furnace between the saturated and superheated tubes. But redistribution alone will not materially affect the energy content of the steam. So feed-water is sprayed into the steam line between the superheater and the temperature bulb. Control at this point is quite effective because the thermal process is one of mixing. 

In order to analyze the effect particles have on superheated atomization, suspensions consisting of deionized water and glass beads are sprayed. The polished glass beads are Silibeads Type S (Size 0-20 pm). The solids concentration is set to 5,15, and 25 wt%. The volume density and cumulative distribution of the beads are given in Fig. 16.9. The major part of the particles is smaller than 10 pm. The beads have a smooth surface as shown in the microscope image in Fig. 16.9. 

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