Continuous-process industries

In continuous-process industries such as petroleum refining, petrochemicals, industrial chemicals, and fertilizers, the siting and size of buildings have been influenced by factors such as the following (Ref. 21) ... 

Zhang J (2005) Transshipment and its Impact on Supply Chain Members Performance. Management Science 51 (10) 1534-1539 Zhou T, Cheng S, Hua B (2000) Supply Chain Optimization of Continuous Process Industries with Sustainability Considerations. Computers Chemical Engineering 24 1151-1158... 

Dunning, J. and Lathrop, E., The saccharification of agricultural residues A continuous process. Industrial Engineering Chemistry 1945, 37 (1), 24-29. 

Messina, W. S., Montgomery, D. C. and Keats, J. B., 1996, Strategies for Statistical Monitoring of Integral Control for the Continuous Process Industries, Statistical Applications in Process Control, New York, Marcel Dekker, 47, 193-214. 

Dangers in continuous process industries that handle flammable liquids with emphasis on loading tankers. 

Peters, M., et al.. Application of membrane residue curve maps to batch and continuous processes. Industrial Engineering Chemistry Research, 2008, 47(7) 2361 2376. 

Mo, Y. W., and Xiao, D. Y. (1999), A Model-Driven Approach to Information Integration in Continuous Process Industries, in Proceedings of the 14th World Congress of IFAC (Beijing), Vol. A, pp. 115-120. 

The quantity of work to be done must be defined by the appropriate time period, which could be by as little as a 15-minute interval for cashiers and as long as a day for paper mills. For continuous process industries, such as chemical plants and some mining processes, the definition of what is needed is relatively easy to determine. Even so, the work must be defined by the hour and day of the year to allow for maintenance and shutdowns for holidays. There are many other industries that also have a well-known stable demand for work profile—for example, prisons, long-term health care facilities, and many manufacturing systems, such as assembly lines. At the other end of the scale are situations such as retad outlets and telephone operators, that have a demand that varies constantly during the day, and from day to day, and from season to season. Many of the organizations with such a fluctuating demand pattern have a detailed data bank of historic data, usually by the 15-minute interval. These data can be used to predict the work requirements for future time periods. 

Cooke, D. and Rohleder, T. Inventory evaluation and product slate management in large-scale continuous process industries. Journal of Operations Management, 24(3) 235-249, 2006. 

The basic premise of behavior modification programs is that the primary cause of accidents is worker error. This blame-the-victim concept provides little opportunity for effective accident prevention. Behavior modification does not focus on the fundamental safety problems that we face in the continuous process industry, (p. 2)... 

Workplace safety is measured by only one statistic, the OSHA recordable rate. Based on this statistical yardstick, continuous process industries continue to be among the safest industries in the country and are getting safer. Many plants have celebrated working millions of hours without a lost work day accident. While all eyes are on the OSHA recordable rate, releases of hazardous materials, fires, mechanical breakdowns and near misses are not included in the safety statistics, (p. 7)... 

Chemical reactors are process vessels that are used in chemical industries for carrying out chemical reactions. Based on the mode of operation, reactors are broadly classified as batch reactors and continuous-flow reactors. In batch reactors, reactants are fed into the reaction vessel at the time of start-up and the products drawn out of the vessel after a specified period of time called reaction time (or batch time). Continuous-flow reactors are encountered more often in practice than batch reactors, as more than 80% of process industries are continuous processing industries. In the case of continuous-flow reactors, reactants are fed into, and products drawn out of, the reaction vessel continuously. 

The book is targeted primarily for use in the continuous process industry, but even predominantly batch plants have continuous controllers and often have sections of the process which are continuous. My experience is mainly in the oil and petrochemicals industries and, despite every effort being taken to make the process examples as generic as possible, it is inevitable that this will show through. However this should not be seen as a reason for not applying the techniques in other industries. Many started there and have been applied by others to a wide range of processes. 

There are many process control methods often leading to the use of control charts for the purposes of process monitoring. One basic assumption for the use of these control charts is that the process variables are independent and identically distributed (IID). Unfortunately, much of the data used in statistical process control is non-IID. As Alwan and Radson note, non-IID behavior such, as cyclical, seasonal and trend often exists in practice. Alwan and Radson also note that because of the efforts of G.E.P. Box, the chemical industry has recognized for many years that autocorrelation exists in their processes. Baxley, " Berthouex et al., Ermer et al., Harris and Ross, and Hunter " have noted that continuous process industries often have autocorrelated process data. 

Zhou, Z., Cheng, S., Hua, B. (2000). Supply chain optimization of continuous processes industries with sustainability considerations. Computers Chemical Engineering, 24, 1151-1158. 

Process industries frequently need to weigh and control the flow rate of bulk material for optimum performance of such devices as grinders or pulverizers, or for controlling additives, eg, to water suppHes. A scale can be installed in a belt conveyor, or a short belt feeder can be mounted on a platform scale. Either can be equipped with controls to maintain the feed rate within limits by controlling the operation of the device feeding the material to the conveyor. Direct mass measurement with a nuclear scale can also be used to measure and control such a continuous stream of material. 

Industrial production is often based on transformation of this laboratory method into a continuous process (10). Another route is acetonitrile [75-05-8] hydration ... 

Industrial-scale adsorption processes can be classified as batch or continuous (53,54). In a batch process, the adsorbent bed is saturated and regenerated in a cychc operation. In a continuous process, a countercurrent staged contact between the adsorbent and the feed and desorbent is estabhshed by either a tme or a simulated recirculation of the adsorbent. 

A recent trend in particle analysis has been the introduction of personal computer-based automation (3). Sophisticated software packages can be used to automate and speed up the analysis. In some cases these computers can even carry out continuous process control (qv) (see Computer technology). The latest machines also allow the measurements of smaller particles and can detect a wider range of sizes. Machines based on light-scattering principles are being more widely accepted by the industry because of speed. An average analysis takes from 1—2 min, whereas those based on sedimentation principles require from 10—120 min. 

Nylon-6 is the polyamide formed by the ring-opening polymerization of S-caprolactam. The polymerization of S-caprolactam can be initiated by acids, bases, or water. Hydrolytic polymerization initiated by water is often used in industry. The polymerization is carried out commercially in both batch and continuous processes by heating the monomer in the presence of 5—10% water to temperatures of 250—280°C for periods of 12 to more than 24 h. The chemistry of the polymerization is shown by the following reaction sequence. 

Nylon-6 can be easily polymerized at atmospheric pressure. A continuous process was developed in 1940, called the VK process, which in German stands for vereinfacht kontinuierlich or simplified continuous (73). The VK process is widely used in industry in the 1990s, whereas batch processes, being less economical, are gradually phased out of use. Procedures are also available for making gram quantities of nylon-6 and nylon-6,6 in the laboratory (74). 

Low Flow Operation. The optimum operation of a pump is near the best efficiency point. Some manufacturers curves indicate the minimum allowable continuous stable flow (MCSF) limits for every pump (43). In the 1980s, the processing industry experienced a reduction in flow requirement as a result of business downturn and installation capacity downsizing. The pumping equipment, however, was generally not replaced by smaller pumps, but was forced to operate at reduced flow rates, often below allowable MCSF. This has resulted in increased failure rates and reduced pump component life. 

Batch reactors often are used to develop continuous processes because of their suitabiUty and convenient use in laboratory experimentation. Industrial practice generally favors processing continuously rather than in single batches, because overall investment and operating costs usually are less. Data obtained in batch reactors, except for very rapid reactions, can be well defined and used to predict performance of larger scale, continuous-flow reactors. Almost all batch reactors are well stirred thus, ideally, compositions are uniform throughout and residence times of all contained reactants are constant. 

The ratio of cycHc to linear oligomers, as well as the chain length of the linear sdoxanes, is controlled by the conditions of hydrolysis, such as the ratio of chlorosilane to water, temperature, contact time, and solvents (60,61). Commercially, hydrolysis of dim ethyl dichi oro sil a n e is performed by either batch or a continuous process (62). In the typical industrial operation, the dimethyl dichi orosilane is mixed with 22% a2eotropic aqueous hydrochloric acid in a continuous reactor. The mixture of hydrolysate and 32% concentrated acid is separated in a decanter. After separation, the anhydrous hydrogen chloride is converted to methyl chloride, which is then reused in the direct process. The hydrolysate is washed for removal of residual acid, neutralized, dried, and filtered (63). The typical yield of cycHc oligomers is between 35 and 50%. The mixture of cycHc oligomers consists mainly of tetramer and pentamer. Only a small amount of cycHc trimer is formed. 

Acid-Gatalyzed Synthesis. The acid-catalysed reaction of alkenes with hydrogen sulfide to prepare thiols can be accompHshed using a strong acid (sulfuric or phosphoric acid) catalyst. Thiols can also be prepared continuously over a variety of soHd acid catalysts, such as seoHtes, sulfonic acid-containing resin catalysts, or aluminas (22). The continuous process is utilised commercially to manufacture the more important thiols (23,24). The acid-catalysed reaction is commonly classed as a Markownikoff addition. Examples of two important industrial processes are 2-methyl-2-propanethiol and 2-propanethiol, given in equations 1 and 2, respectively. 

It is likely that there will always be a distinction between the way CAD/CAM is used in mechanical design and the way it is used in the chemical process industry. Most of the computations requited in mechanical design involve systems of linear or lineatizable equations, usually describing forces and positions. The calculations requited to model molecular motion or to describe the sequence of unit operations in a process flow sheet are often highly nonlinear and involve systems of mixed forms of equations. Since the natures of the computational problems are quite different, it is most likely that graphic techniques will continue to be used more to display results than to create them. 

Continuous Pressure Filter for the Process Industries, IngersoU-Rand, Nashua, N.H., 1992. 

The first successful appHcation of heterogeneous azeotropic distillation was in 1902 (87) and involved using benzene to produce absolute alcohol from a binary mixture of ethanol and water. This batch process was patented in 1903 (88) and later converted to a continuous process (89). Good reviews of the early development and widespread appHcation of continuous azeotropic distillation in the prewar chemical industry are available (90). 

Ethyl acetate is made industrially by both batch and continuous processes (361,362). Glacial acetic acid is commonly the starting material, and any water formed during the esterification has to be removed. Sulfuric acid may be added periodically to the reactor to replace the acid lost in side reactions. 

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