Residence time of materials

These relationships show that the F curve is related in a simple way to the age distribution of material in the vessel, while the C curve gives directly the distribution of residence times of material in the vessel. In addition, the C and E curves represent the slopes of the corresponding... 

The residence time of materials in either the continuous or dispersed phase in the active region is very short, about I s only and... 

To solve the problem that the residence time of material in a simple impinging stream device is very short so that drying cannot be carried out individually, in addition to the improvements described above, some technological schemes have been proposed which combine the method of impinging streams with other method some of these are introduced below. 

The residence time of material in the rotary kiln is determined based on the kiln slope, the speed of rotation, kiln diameter, and by the presence of any internal restrictions either by design or due to ring formation in operation. The residence time, x expressed in minutes, can be calculated from the formula first given by the U.S. Bureau of Mine ... 

Rapid response is required because the residence time of material in the process equipment varies from a few seconds to a few minutes average residence time in the plant is typically less than ten minutes. Furthermore, significant variations in the composition of the run-of-the-mine coal fed to the plant can occur in a step functional manner. The heterogenous nature of coal and the quantity of material processed through a typical circuit within a preparation plant requires a simple means of obtaining information representative of the process stream. Non-invasive sampling methods are preferred because material handling problems are minimized. 

One of the greatest contrasts between the processes is the residence time within the reactor. It has already been noted that the poly(vinyl alcohol) in the batch process is usually present from the start. The residence time is therefore several hours. In contrast, the mean residence time of materials in the Loop process is around 2 to 10 min. This has obvious advantages in terms of minimizing degradation of colloids but will also restrict grafting between colloid and monomer. 

A continuous CFBD was further designed (Figure 29.4) with a dryer surface of approximately 21 ft in the form of a rotating perforated stainless steel cylinder (10 in. diameter and 100 in. long) with an open area of 45% and Teflon-coated inside [30]. The cylinder could be rotated at speeds up to 350 rpm (F = 17.4 x G) through a belt drive and tilted between 0° and 6° from the horizontal to help control the residence time of material that is dried. Centrifugal fans with steam heaters enabled air temperatures up to 140°C. 

The slope is generally 3°-5° and the speed of rotation is adjusted by VFD so that the residence time of material is adjustable by varying the speed of rotation. It is generally 2—12 h. 

Thermal rating of refractory lining in burning zone 20 to 25GJ/m h Residence time of material in kiln 3 to 5 hours. 

Screw speed influences the residence time of the powder inside the barrel and torque produced during processing. Residence time of material inside the barrel is reduced by the increase of screw speed. Decrease in residence time is due to conveying capacity of rapidly moving screws. Residence time increases with low material feed and torque decrease, due to restricted packing of material. It leads to porous products or the material degrades inside the barrel. 

Design a process to continuously produce prebaked pizza dough for a major grocery chain. Your flowsheet should have labels on all units and qualitative compositions of all streams. For each unit list key quantities such as temperature and residence time of material through the unit. 

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