Separation trains

Xylene Isomeri tion. The objective of C-8-aromatics processing is the conversion of the usual four-component feedstream (ethylbenzene and the three xylenes) into an isomerically pure xylene. Although the bulk of current demand is for xylene isomer for polyester fiber manufacture, significant markets for the other isomers exist. The primary problem is separation of the 8—40% ethylbenzene that is present in the usual feedstocks, a task that is compHcated by the closeness of the boiling points of ethylbenzene and -xylene. In addition, the equiUbrium concentrations of the xylenes present in the isomer separation train raffinate have to be reestabUshed to maximize the yield of the desired isomer. 

The separation train of the plant is designed to recover important constituents present in the furnace effluent. The modem olefin plant must be designed to accommodate various feedstocks, ie, it usually is designed for feedstock flexibiUty in both the pyrolysis furnaces and the separation system (52). For example, a plant may crack feedstocks ranging from ethane to naphtha or naphtha to gas oils. 

The final purification steps are responsible for the removal of the last traces of impurities. The volume reduction in the earlier stages of the separation train are necessarv to ensure that these high-resolution operations are not overloaded. Generally, chromatograjmy is used in these final stages. Electrophoresis can also be used, but since it is rarely found in process-scale operations, it is not addressed here. The final product preparation may require removal of solvent and drying, or lyophihzation, of the product. 

Motivation Unit tests require a substantial investment in time and resources to complete successfully. This is the case whether the test is a straightforward analysis of pump performance or a complex analysis of an integrated reactor and separation train. The uncertainties in the measurements, the likelihood that different underlying problems lead to the same symptoms, and the multiple interpretations of unit performance are barriers against accurate understanding of the unit operation. The goal of any unit test should be to maximize the success (i.e., to describe accurately unit performance) while minimizing the resources necessary to arrive at the description and the subsequent recommendations. The number of measurements and the number of trials should be selected so that they are minimized. 

When assessing the robustness of a process, several factors that can adversely affect it include non-selective or side reactions that might produce adverse effects and impurities physical and chemical stability of the materials involved and complexity of the separation train of the processes. 

Before the hold tanks can be specified it must be determined whether one, two, or three products are to be made simultaneously. If only one product is made at a time, a large single-train centrifuging and drying system can be constructed. However, when two or three products are produced in separate trains at different rates, it would appear that the desire to have both similar equipment and optimally sized equipment for each train cannot be met. Therefore, for this plant only one product will be made at a time. Further, two full trains will be constructed. This is to prevent the plant from fully shutting down because of the failure of a piece of equipment. When the proposed expansion occurs another full train will be added. 

The most common type of commercial pyrolysis equipment is the direct fired tubular heater in which the reacting material flows through several tubes connected in series. The tubes receive thermal energy by being immersed in an oil or gas furnace. The pyrolysis products are cooled rapidly after leaving the furnace and enter the separation train. Constraints on materials of construction limit the maximum temperature of the tubes to 1500 °F. Thus the effluent from the tubes should be restricted to temperatures of 1475 °F or less. You may presume that all reactor tubes and return bends are exposed to a thermal flux of 10,000 BTU/... 

Olefins plant separation train, 20 776 Olefins reduction, in gasoline, 11 689 a-Olefin sulfonate (AOS), 17 725-726 ... 

Low water level in the reaction medium which simplifies the separation train especially for the HI-H2O-ACOH mixture... 

A possibility for saving weight, space, and capital offshore is in the oil-gas-water separation train. 

Separation trains. With a nominal peak production rate determined and a GOR known, a large latitude then exists in selecting the oil-gas separation train configuration. 

All of these factors affect the number of separation trains per stage. Mechanical separation characteristics, such as foaming tendency with a large GOR drop should also be considered. The reservoir pressure maintenance program should be considered. 

Optimization of the main process relative to oil and gas separation trains, gas compression, and condensate disposal were also discussed. 

The object of well testing is to determine oil, qas, and water production rates and to establish correlations for production control and allocation. Unfortunately, well flow rates cannot be measured directly because of three phase flow. Consequently, a well rate must be measured by flowing the well individually to a test separator. The well testing process is completely automated and controlled from the HOC, requiring no action on the part of the GC operators during normal operation. Figure 3 shows a test separation train, typical of each of the three... 

Figure 8.18 Flow schemes ofthe separation train of a 50-million gallon/y bioethanol plant. Current technology is illustrated in (a). Pervaporation membranes can be used to replace the molecular-sieve drier of the plant (b) or vapor-permeation membranes can be used to replace the rectifier column and molecular-sieve units (c).

In the second step, the dioxanes are vaporized, superheated, and then cracked on a solid catalyst (supported phosphoric acid) in the presence of steam. The endothermic reaction takes place a about 200 to 2S0°C and 0.1 to OJ. 10 Pa absolute. The heat required is supplied by the introduction of superheated steam, or by heating the support of the catalyst, which operates in a moving, fluidized or fixed bed, and, in this case, implies cyclic operation to remove the coke deposits formed. Isoprene selectivity is about SO to 90 mole per cent with once-through conversion of 50 to 60 per cent The 4-4 DMD produces the isoprene. The other dioxanes present are decomposed into isomers of isoprene (piperylene etc.), while the r-butyl alcohol, also present in small amounts, yields isobutene. A separation train, consisting of scrubbers, extractors and distillation columns, serves to recycle the unconverted DMD, isobutene and fonnol, and to produce isoprene to commercial specifications. 

The gases are then compressed further and passed through a drier to the separation train. The cracked gases now contain only hydrocarbons and hydrogen. 

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