Creating and optimizing a reducible structure. In this approach, a structure known as a superstructure or hyperstructure is first created that has embedded within it all feasible process operations and all feasible interconnections that are candidates for an optimal design. Initially, redundant features are built into the structure. As an example, consider Fig. 1.7. This shows one possible structure of a process for the manufacture of benzene from the reaction between toluene and hydrogen. In Fig. 1.7, the hydrogen enters the process with a small amount of methane as an impurity. Thus in Fig. 1.7 the option is embedded of either purifying the hydrogen feed with a membrane or passing directly to the process. The hydrogen and toluene are mixed and preheated to reaction temperature. Only a furnace has been considered feasible in this case because of the high temperature required. Then two alternative reactor options, isothermal and adiabatic reactors, are embedded, and so on. Redundant features have been included in an effort to ensure that all features that could be part of an optimal solution haVe been included.  [c.9]

Figure 3.6 shows four examples of cake filtration in which the filter medium is a cloth of natural or artificial fibers or even metal. Figure 3.6a shows the filter cloth arranged between plates in an enclosure. Figure 3.66 shows the cloth arranged as a thimble. This arrangement is common for the separation of solid particles from vapor and is known as a bag filter. Figure 3.6c shows a rotating belt for the separation of a slurry of solid particles in a liquid, and Fig. 3.6d shows a rotating drum in which the drum rotates through the slurry. When filtering solids from liquids, if the purity of the filter cake is not important, filter aids, which are particles of porous solid, can be  [c.73]

Tunnel dryers are shown in Fig. 3.15a. Wet material on trays or a conveyor belt is passed through a tunnel, and drying takes place by hot air. The airflow can be countercurrent, cocurrent, or a mixture of both. This method is usually used when the product is not free flowing.  [c.89]

The grand composite curve is obtained by plotting the problem table cascade. A typical grand composite curve is shown in Fig. 6.24. It shows the heat flow through the process against temperature. It should be noted that the temperature plotted here is shifted temperature T and not actual temperature. Hot streams are represented ATn,in/2 colder and cold streams AT iJ2 hotter than they are in practice. Thus an allowance for ATj in is built into the construction.  [c.185]

It also should be noted in Fig. 4.4[c.240]

Here we shall restrict consideration to safety and health considerations that can be built in while the design is developing rather than the detailed hazard and operability studies that take place in the later stages of design. The three major hazards in process plants are fire, explosion, and toxic release.  [c.255]

Feed purification. Impurities that enter with the feed inevitably cause waste. If feed impurities undergo reaction, then this causes waste from the reactor, as already discussed. If the feed impurity does not undergo reaction, then it can be separated out from the process in a number of ways, as discussed in Sec. 4.1. The greatest source of waste occurs when we choose to use a purge. Impurity builds up in the recycle, and we would like it to build up to a high concentration to minimize waste of feed materials and product in the purge. However, two factors limit the extent to which the feed impurity can be allowed to build up  [c.282]

If the air is substituted by pure oxygen, then the problem of the large fiow of inert gas is eliminated (see F g. 10.4b). Unreacted gases can be recycled to the reactor. This allows oxygen-based processes to be operated with an excess of ethylene, thereby enhancing the HCl conversion without sacrificing ethylene yield. Unfortunately, this introduces a safety problem downstream of the reactor. Unconverted ethylene can create explosive mixtures with the oxygen. To avoid explosive mixtures, a small bleed of nitrogen is introduced.  [c.283]

There are many other sources of waste associated with process operations which can only be taken care of in the later stages of design or after the plant has been built and has become operational. For example, poor operating practice can mean that the process operates under conditions for which it was not designed, leading to waste. Such problems might be solved by an increased level of automation or better management of the process. These considerations are outside the scope of this text.  [c.290]

Waste from cooling systems. Cooling water systems also give rise to wastewater generation. Most cooling water systems recirculate water rather than using once through arrangements. Water is lost from recirculating systems in the cooling tower mainly through evaporation but also, to a much smaller extent, through drift (wind carrying away water droplets). This loss is made up by raw water which contains solids. The evaporative losses from the cooling tower cause these solids to build up. The buildup of solids is prevented by a purge of water from the system, i.e., cooling tower blowdown. Cooling tower blowdown is the source of the largest volume of wastewater on many sites.  [c.294]

C. It is secreted along with noradrenaline by the adrenal medulla, from which it may be obtained. It may be synthesized from catechol. It is used as the acid tartrate in the treatment of allergic reactions and circulatory collapse. It is included in some local anaesthetic injections in order to constrict blood vessels locally and slow the disappearance of anaesthetic from the site of injection. Ultimately it induces cellular activation of phosphorylase which promotes catabolism of glycogen to glucose.  [c.16]

A potent carcinogen, it is now little used for dyestuffs for cotton. Still used for blood detection.  [c.56]

Molecules. The electronic configurations of molecules can be built up by direct addition of atomic orbitals (LCAO method) or by considering molecular orbitals which occupy all of the space around the atoms of the molecule (molecular orbital method).  [c.152]

A base, formed by the bacterial degradation of histidine, and present in ergot and in many animal tissues, where it is liberated in response to injury and to antigen-antibody reactions. If injected it causes a condition of shock with dilatation of many blood vessels, loss of plasma from the capillaries to the tissues and a rapid fall in blood pressure. It is normally prepared from protein degradation products.  [c.204]

Insulin is built up of two polypeptide chains. A of 21 amino-acids and B of 30 amino-acids, linked by two disulphide bridges.  [c.217]

Acts to constrict small arteries, thereby increasing blood pressure and to contract smooth muscle. Used in cases of peripheral vasomotor collapse.  [c.282]

D-fructose, C HijOo. Crystallizes in large needles m.p. 102-104 C. The most eommon ketose sugar. Combined with glucose it occurs as sucrose and rafftnose mixed with glucose it is present in fruit juices, honey and other products inulin and levan are built of fructose residues only. In natural products it is always in the furanose form, but it crystallizes in the pyranose form. It is very soluble in  [c.182]

D-glucose, dextrose, C Hi20 . The most common hexose sugar. It is present in many plants, and is the sugar of the blood. It is a constituent of starch, cellulose, glycogen, sucrose and many glycosides, from all of which it can be obtained by hydrolysis with acids or enzymes.  [c.190]

CifiHjjOi. A fatly acid which is easily oxidized in air.-It occurs widely, in the form of glycerides, in vegetable oils and in mammalian lipids. Cholesieryl linoleale is an important constituent of blood. The add also occurs in lecithins. Together with arachidonic acid it is the most important essential fatty acid of human diet.  [c.240]

See pages that mention the term Balata : [c.195]    [c.28]    [c.38]    [c.40]    [c.40]    [c.50]    [c.59]    [c.61]    [c.66]    [c.70]    [c.81]    [c.95]    [c.130]    [c.131]    [c.155]    [c.161]    [c.161]    [c.175]    [c.183]    [c.191]    [c.193]    [c.196]    [c.198]    [c.198]    [c.201]    [c.204]    [c.206]    [c.227]    [c.233]    [c.236]    [c.283]    [c.283]   
Plastics materials (1999) -- [ c.866 ]