Single streams

The eadiest use of heat-exchange network synthesis was in the analysis of cmde distillation (qv) units (1). The cmde stream entering a distillation unit is a convenient single stream to heat while the various side draws from the column are candidate streams to be cooled in a network. So-called pumparounds present additional opportunities for heating the cmde. The successful synthesis of cmde distillation units was accompHshed long before the development of modem network-synthesis techniques. However, the techniques now available ensure rapid and accurate development of good cmde unit heat-exchange networks. 

For the special case of a single stream flowing through the system, Eq. (4-360) becomes... 

For a single stream, division bym provides an equation based on a unit amount of fluid flowing through the control volume ... 

For flow of a single stream on the basis of a unit amount of fluid, this becomes... 

Instead of using conventional refrigeration and condensers to convert incoming gas into LNG, the system was designed to feed 2,340 Nm / day (86,800 scfd) into each of two expanders. Both are connected in parallel, with compressors attached at the back end. The compressors are connected in series to boost a single stream of returning gas. 

Single stream Multistream with many crossovers... 

There are two primary sources for aqueous pollution in this process—the condensate streams R] (1,000 kg/hr) and R2 (69,300 kg/hr). Both streams have the same supply composition, which corresponds to the solubility of benzene in water which is 1770 ppm (1.77 X10 kg bcnzcne/kg water). Consequently, they may be combined as a single stream. The target composition is 57 ppb as dictated by the VOC environmental regulations called NPDES (National Pollutant Discharge Elimination System). 

When separating volatile components such as a single stream from low-volatility bottoms, use a molecular or unobstructed path process, either thin film or batch. 

The carbon dioxide volume content was varied from 0.8 to 100 vol.-% the gas velocity changes from 0.1 to 42.9 mm s [5]. The residence time varied from 0.1 to 9.7 min 64 single streams of a liquid film thickness of 65 pm were used at a total volume flow of 50 ml h . The ratio of carbon dioxide to sodium hydroxide was fixed at 0.4. 

Holroyd, R. Ultra Large Single Stream Chemical Plants Their Advantages, Disadvantages, Chemistry and Industry, Aug 5, 1967, p. 1310. 

A single-stream plant was required (minimum installed spares/duplicated machines) but with greater than 95% uptime. 

Figure 1.2 Schematic of a compact combustor using countercurrent shear layer (a) and comparison of measured strain rate fields in a single-stream (6) and countercurrent (c) shear layers [9]...

The Lewis ENVIRO-CLEAN process removes and recovers metals such as chromium, copper, nickel, mercury, lead, zinc, iron, and cadmium and has effectively demonstrated that it can treat a matrix of multiple metals in a single stream with positive results. The process treats wastes from wood preserving, metal finishing, mining, surface and groundwaters. The two-step process uses granular-activated carbon and electrolytic metal recovery to yield a salable metallic by-product. 

Of course, we need not use speech to communicate. If we could transmit just a single stream of bits (e.g., ones and zeros) into the fourth dimension, communication would be possible. In fact, the rapid appearance and disappearance of a 4-D object in our world could be used to communicate a binary message. 

Radial Mixing Radial dispersion can be viewed as a result of stream slitting and sidestepping. A stream of fluid at a particular radial position strikes a solid particle in its axial journey and is split into two by the collision. On average, half the stream moves laterally to the right and the other to the left. This is happens repeatedly and the result is that the original single stream is laterally dispersed toward the wall. 

Factors that affect the safety of a production system include (1) the scale of production (2) the quantity of hazardous chemicals involved (3) the hazardousness of the chemicals involved (4) batch versus continuous processing (5) the presence of pressure or temperature extremes (6) storage of intermediates versus closed loop processing and (7) multi-stream versus single-stream plants. These factors are discussed briefly below. 

Multi-Stream Versus Single-Stream Plants... 

In addition to a large catalytically active surface and good capacity for adsorption, an efficient catalyst requires selectivity, that is, preferential affinity for the appropriate reactants. Nonselectivity is a source of significant problems in catalysis, particularly in the petrochemical industry, which has to deal with hydrocarbons of various types and isomers in a single stream. This situation has provided a strong incentive for the development of artificial (man-made) catalysts that offer the type of selectivity unthinkable on metal surfaces discussed in the last section of Chapter 9 (see, for example, Ball 1994) and illustrates another example of molecular design (or molecular engineering ) of advanced materials for use in science and industry. 

Wastes produced at a particular facility will be similar to those listed, but their precise composition will depend on the specific process. Some or all of the waste types listed may be combined into a single stream before treatment and disposal. It is common to combine concentrated cyanide wastes from plating and cleaning solutions, for instance, with filter sludges. These are frequently kept separate, however, from acidic wastes and from dilute cyanide solutions. 

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