Variation, process

Sasol produces synthetic fuels and chemicals from coal-derived synthesis gas. Two significant variations of this technology have been commercialized, and new process variations are continually under development. Sasol One used both the fixed-bed (Arge) process, operated at about 240°C, as weU as a circulating fluidized-bed (Synthol) system operating at 340°C. Each ET reactor type has a characteristic product distribution that includes coproducts isolated for use in the chemical industry. Paraffin wax is one of the principal coproducts of the low temperature Arge process. Alcohols, ketones, and lower paraffins are among the valuable coproducts obtained from the Synthol process. 

Because an excess of ammonia is fed to the reactor, and because the reactions ate reversible, ammonia and carbon dioxide exit the reactor along with the carbamate and urea. Several process variations have been developed to deal with the efficiency of the conversion and with serious corrosion problems. The three main types of ammonia handling ate once through, partial recycle, and total recycle. Urea plants having capacity up to 1800 t/d ate available. Most advances have dealt with reduction of energy requirements in the total recycle process. The economics of urea production ate most strongly influenced by the cost of the taw material ammonia. When the ammonia cost is representative of production cost in a new plant it can amount to more than 50% of urea cost. 

Hydrazine [302-01-2] (diamide), N2H4, a colorless liquid having an ammoniacal odor, is the simplest diamine and unique in its class because of the N—N bond. It was first prepared in 1887 by Curtius as the sulfate salt from diazoacetic ester. Thiele (1893) suggested that the oxidation of ammonia (qv) with hypochlorite should yield hydrazine and in 1906 Raschig demonstrated this process, variations of which constitute the chief commercial methods of manufacture in the 1990s. 

A process variation of the extraction of 2-isopropylnaphthalene hydroperoxide from the cmde oxidation product with an alkylene glycol has been patented (71). The 2-naphthalenol plant of American Cyanamid, which was using the hydroperoxidation process and had a 14 x 10 t /yr capacity (72), ceased production in 1982, leaving the United States without a domestic producer of 2-naphthol. The 2-naphthol capacity in the Western world is approximately 50 x 10 t/yr, with ACNA, Italy and Hoechst AG, Germany operating the largest plants. China produces about 7 x 10 t/yr. Other important producing countries are Poland, Romania, the former Czechoslovakia, and India (35,52). 

Process flow sheets and process descriptions given herein are estimates of the various commercial processes. There are also several potential commercial processes, including variations on the chlorohydrin process, variations on the hydroperoxide process, and direct oxidation of propylene. 

Variations found in CTO composition result primarily from the species of wood pulped and the location and climate where the trees are grown. Pulping process variations further affect CTO composition. The best CTO is produced from pine wood. However, many U.S. mills mix hardwood with pine to reduce fiber costs, or mix hardwood black Hquor with pine black Hquor. This lowers the rosin content. The composition of CTO produced in the southeastern United States and of typical Canadian and Scandinavian CTOs are shown in Table 2. 

In the past the successful operation of batch processes depended mainly on the skill and accumulated experience of the operator. This operating experience was difficult to codify in a form that enabled full use to be made of it in developing new designs. The gradual evolution of better instmmentation, followed by the installation of sequence control systems, has enabled much more process data to be recorded, permitting maintenance of process variations within the minimum possible limits. 

Historical DataBase Subsystem We have discussed the use of on-hne databases. An historical database is built similar to an on-line database. Unlike their on-line counterparts, the information stored in a historical database is not normally accessed directly by other subsystems for process control and monitoring. Periodic reports and longterm trends are generated based on the archived data. The reports are often used for long-term planning and system performance evaluations such as statistical process (quality) control. The trends may be used to detect process drifts or to compare process variations at different times. 

Operation When operated correctly, thickeners require a minimum of attention and, if the feed characteristics do not change radically, can be expected to maintain design performance consistently. In this regard, it is usually desirable to monitor feed and underflow rates and sonds concentrations, flocculant dosage rate, and pulp interface level, preferably with dependable instrumentation systems. Process variations are then easily handled by changing the principal operating controls—underflow rate and floccirlant dose—to maintain stability. 

Design control strategy for acceptable systems in order to handle different situations (seasonal, process variations). 

To guarantee shipment on time, you either need to maintain an adequate inventory of finished goods for shipment on demand or utilize only predictable processes and obtain sufficient advanced order information from your customer. When you examine some of the requirements in ISO/TS 16949, you may be tempted to question how you can continually improve performance, reduce costs, and minimize space, material travel, equipment downtime, process variation, etc. and meet 100% on-time shipments. You can t, unless you have a partnership with your customer in which there is mutual assistance to meet common objectives. Without sufficient lead time on orders you will be unlikely to meet the target. However, the standard does acknowledge that you may not always be successful. There will be matters outside your control and matters over which you need complete control. It is the latter that you can do something about and take corrective action should the target not be achieved. 

Methods developed for on-line technological control have to be tested for the variation of the product composition due to process variations. However, if rugged analytical procedures are developed these multidimensional methods may only require minimal attention during on-line operation. Multidimensional chromatography for the analysis of complex polymer and industrial samples offers chromatogra-phers high productivity and efficiency and is an excellent alternative to off-line methods. 

Each process parameter directly affects both the machinery dynamics and the vibration profiles. For example, the line tension, strip width, and hardness of the incoming strip radically affect the vibration profile generated by a continuous process line in a steel mill. With few exceptions, process variations such as these must be considered in the vibration analysis. 

There are three phases in the evolution of most QC systems (1) defect detection where an army of inspectors tries to identify defects (2) defect prevention where the process is monitored, and statistical methods are used to control process variation, enabling adjust-... 

The dependence of the C,E curves for a solid metal on the method of electrode surface preparation was reported long ago.10 20 67 70 219-225 in addition to the influence of impurities and faradaic processes, variation in the surface roughness was pointed out as a possible reason for the effect.10 67,70 74 219 For the determination of R it was first proposed to compare the values of C of the solid metal (M) with that of Hg, i.e., R = C-M/c-Hg 10,74.219-221 data at ff=0 for the most dilute solution (usually... 

EC) No. 1085/2003 outline the procedures for processing variations to marketing authorisations granted via National and Community procedures, respectively. The Annexes to the regulations provide criteria for categorisation of changes. 

CVDequipmentdoesnotnormallyrequireultrahighvacuum and generally canbe adapted to many process variations. 

It is remarkable that the falling film micro reactor achieved complete conversion for all process variations applied [5]. This is unlike conventional reactor operation reported for this reaction, displaying pronounced mass transfer resistance. 

Gagnon, P., Grund, E., and Lindback, T., Large-scale process development for hydrophobic interaction chromatography, part II controlling process variation, BioPharm, 8, 36, 1995. 

It is easy to improperly design a steam trap. The design must work for two circumstances and often a designer will check only one of these. The circumstance often overlooked is as follows On startup or upset, the steam control valve can open wide so that the steam chest pressure (assume for this discussion that we are speaking of a reboiler) rises to full steam line pressure. At a time like this, the steam trap downstream pressure can be atmospheric due to process variations or the operators opening the trap discharge to atmosphere in an attempt to get it working. 

We will illustrate the wide range of injection molding products and process variations by discussing a few key examples. 

To estimate costs for the liquid-liquid biphasic hydroformylation using ionic liquids, a process was designed for the production of 100,000 tons per year of nonanal. The use of ionic liquids in hydroformylation catalysis is a fairly new technology and exact kinetic data are scarce, thus the TOFs reported for the Rh-sulfoxantphos system [80] have been used to determine catalyst inventory and reactor dimensions. In a similar way the plant design for the SILP process for a production capacity of 100,000 tons per year of butanal has been derived based on preliminary literature results [68]. The process flow sheets for both process variations are shown in Figures 7.12 and 7.13. 

Lanxide A process for making composites of metals with oxides. A molten metal reacts with an adjacent oxidant and is progressively drawn through its own oxidation product so as to yield a ceramic/metal composite. Fibres or other reinforcing materials can be placed in the path of the oxidation reaction and so incorporated in the final product. The Lanxide Corporation was founded in 1983 in Newark, DE, to exploit this invention. In 1990 it formed a joint venture with Du Pont to make electronic components by this process. Variations are Dimox (directed metal oxidation), for making ceramic metal composites, and Primex (pressureless infiltration by metal), for making metal matrix composites. 

The three overlay plots shown in Fig. 4.11 illustrate another example of how process variations can lead to unexpected changes in material behavior. Consider the instance of a spray congealing process where a mixture of one or more waxes with a melting point below that of the... 

Statistical Mechanics and Thermodynamics of Irreversible Processes, Variational Principles in (Ono). ... 

On the other hand, the nitrile function may be a good precursor for the keto-6- functionalized group CO Cl R nevertheless this process variation is restricted to copolymers bearing isolated methacrylonitrile units to avoid degradation (no tertiary enolizable H atom) and cyclization of the CN bonds ... 

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