High-rate streams

If indirect heat transfer is used with a large temperature difference to promote high rates of cooling, then the cooling fluid (e.g., boiling water) is fixed by process requirements. In this case, the heat of reaction is not available at the temperature of the reactor effluent. Rather, the heat of reaction becomes available at the temperature of the quench fluid. Thus the feed stream to the reactor is a cold stream, the quench fluid is a hot stream, and the reactor effluent after the quench is also a hot stream. 

The UPI and MI retorts are processing 7000 t/d (7700 short tons/d) of Irati shale to produce 24,381 m /d (3870 bbl) of shale as well as 80 t (55 short tons) of LPG, 132 t (145 short tons) of clean fuel gas, and 98 t (108 short tons) of sulfur. The SIX plant has reached its design rate (Table 16) in an energy efficient manner with a high on-stream (operating) factor. 

In turbulent motion, the presence of circulating or eddy currents brings about a much-increased exchange of momentum in all three directions of the stream flow, and these eddies are responsible for the random fluctuations in velocity The high rate of transfer in turbulent flow is accompanied by a much higher shear stress for a given velocity gradient. 

In direct-contact heat exchange the hot and cold streams are brought into contact without any separating wall, and high rates of heat transfer are achieved. 

A jet ejector pump is shown in Fig. 5-P61. A high speed stream (2a) is injected at a rate of 50 gpm through a small tube 1 in. in diameter into a stream (2b) in a larger, 3 in. diameter, tube. The energy and momentum are transferred from the small stream to the larger stream, which increases the pressure in the pump. The... 

In the discussion of premixed turbulent flames, the case of infinitely fast mixing of reactants and products was introduced. Generally this concept is referred to as a stirred reactor. Many investigators have employed stirred reactor theory not only to describe turbulent flame phenomena, but also to determine overall reaction kinetic rates [23] and to understand stabilization in high-velocity streams [62], Stirred reactor theory is also important from a practical point of view because it predicts the maximum energy release rate possible in a fixed volume at a particular pressure. 

High rates of water influx remove SiO at low solution concentrations. Normal ground water and streams carry about 17 ppm SiO and less in high rainfall areas (Davis, 1964). In some weathering profiles silicification or deposition of silica has been observed. Most often the form of the phase deposited is crypto-crystalline, either opal or chalcedony. In these cases quartz grains do not show overgrowths (Elouard and Millot,... 

Several methods for separating cells have been devised. These include electrophoresisd or use of magnetic microspheres. b Micromanipulation can sometimes be used to select single cells for analysis. The most impressive technique is flow cytometry,ef which is used daily on human blood samples in clinical laboratories. A suspension of cells is passed at a high rate of flow through a narrow capillary of 0.2 mM diameter. The sample stream, which is surrounded by a larger "sheath" stream, has a... 

Estimates of denitrification rates range from 54 to 345 xmol/m2 per hour in streams with high rates of organic matter deposition, 12 to 56 xmol/m2 per hour in nutrient-poor oligotrophic lakes, and 42 to 171 xmol/m2 per hour in eutrophic lakes (62). Rudd et al. (64) reported an increase in the rate of denitrification from less than 0.1 to over 20 xmol/m2 per hour in an oligotrophic lake when nitric acid was added in a whole-lake experimental acidification. This result suggests that freshwater denitrification may be limited by N03" availability. In deep muds of slow-flowing streams, the process can effectively reduce N03" concentrations in... 

Anaerobic Environments. Because the initial attack of the LAS molecule is oxidative, LAS does not biodegrade under anaerobic conditions (19). Therefore concerns are sometimes expressed that LAS may accumulate in deep anaerobic sediment layers, where it will not biodegrade further. However, given the high rate of LAS removal during sewage treatment combined with in-stream degradation, it is unlikely that LAS sediment accumulation will occur unless there is rapid deposition into an anaerobic environment. 

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