Simulator feed description

It can be seen from the previous description that the design of both a cold-feed stabilizer and a stabilizer with reflux is a rather complex and involved procedure. Distillation computer simulations are available that can be used to optimize the design of any stabilizer if the properties of the feed stream and desired vapor pressure of the bottoms product are known. Cases should be run of both a cold-feed stabilizer and one with reflux before a selection is made. Because of the large number of calculations required, it is not advisable to use hand calculation techniques to design a distillation process. There is too much opportunity for computational eiToi. 

Large diameter, melt-fed extruders are commonly used for the final devolatilization and pelletization of LDPE and PE copolymers in resin manufacturing plants. A full description of this type of extruder and process is provided in Section 15.3. Simulation of these processes is complicated by the multiple flights used in the design and the high H/W aspect ratios of the channels. The processes can be simulated from the feed hopper to discharge, however, since they are not required to convey solids and melt resin. This section will show the requirements and difficulties for simulating these processes. 

The next two major models were those by Fuller and Newman and Nguyen and White,who both examined flow effects along the channel. These models allowed for a more detailed description of water management and the effect of dry gas feeds and temperature gradients. Throughout the next few years, several more 0-D models and 1-D models were generated. Also, some simulations examined... 

The feed to the hydrocracker consists of the heavy naphtha cut from the base crude mix and light cycle oil from the base FCC operation. The hydrocracker simulator requires a description of each of these feeds in terms of the hydrocarbon components shown in Table I. Since these components are not directly measured in the crude assay nor are they predicted by the FCC simulator, special techniques were developed to estimate them from available data. 

The reformer simulator also requires a description of the feed in terms of hydrocarbon components. These are shown in Table II. Fortunately, most of these components are measured in the crude assay and are predicted by the hydrocracker simulator. 

Description The process simulates a moving bed of adsorbent with continuous counter-current flow of liquid feed over a solid bed of adsorbent. Feed and products enter and leave the adsorbent bed continuously, at nearly constant compositions. A rotary valve is used to periodically switch the positions of the feed-entry and product-withdrawal points as the composition profile moves down the adsorbent bed. 

Dohle et al. presented a one-dimensional model for the vapor-feed DMFC, including a description of the methanol crossover [158]. The effects of methanol concentration on the cell performance were studied. Scott et al. also developed several simplified single-phase models to study transport and electrochemical processes in liquid-feed DMFC and showed that the cell performance is limited by the slow diffusion of methanol in the liquid [13, 159-171]. Siebke et al. presented a ID mathematical model and a numerical simulation to explore the influence of different physical and electrochemical phenomena in the MEA of the liquid feed DMFC [162]. Dohle et al. presented a model to describe the heat and the power management of a DMFC system [163]. 

In 2002 I have invented a transient, multiscale and multiphysics single fuel cell model, called MEMEPhys. This model, that 1 have continuously developed since then, accounts for the coupling between self-consistent physical-based mechanistic descriptions of the PEM and the CL phenomena (e.g. reactants, water and charge transport and detailed electrochemistry) and different materials aging mechanisms [59, 205-215], The model is designed for simulating hydrogen-feed PEMFC, PEM Water Electrolyzers and Li Ion batteries, but could be easily extended to simulate DAFCs. 

The description in the literature of early gas desulphurization processes that utilize zeolites does not mention duly the formation of COS during the removal of H2S, if CO2 is present in the feed gas, except in a few cases, e.g., ref. [20,28,65]. Since modern desulphurization plants work in accordance with the same principles and utilize identical zeolite types, the COS formation reaction may have strong implications for the currently employed processes for desulphurization of gases by means of those sorbents. Therefore, it is necessary to investigate (i) the COS formation as dependence on the zeolite type, the type and content of cations in the sorbent, the concentration and contact time of reactants with the sorbent, the temperature and the conditions of co-adsorption (ii) the mechanism of that reaction on the sorbent with specific emphasis on its sorption and catalytic properties and (iii) to develop a mathematical model to simulate dynamic processes that proceed in adsorbers/reactors of technical dimension. This investigation should lead to novel formulations of modified zeolite sorbents and to alternatives with regard to operating conditions of sorption plants with the purpose of either minimization or maximization of the formation of COS. 

The mercury removal performance of pilot-scale ICDAC and of Norit s FGD carbon were determined in a 0.236 m% (0.25 MWe) pilot plant operated by CONSOL, Inc., Library, PA. The pilot plant can simulate flue gas conditions downstream of the air preheater in a coal fired utility power plant. The flue gas mercury concentration studied (10-15 pg/m ) is typical of utility flue gas concentration. Mercury removals were evaluated in the flue gas duct, which provided a gas residence time of approximately 2 seconds, and in the baghouse, where the solids retention times can be as long as 30 min. Common test conditions were flue gas flow, 0.165 m /s flue gas wet bulb temperature, 50-53°C flue gas composition, 1000 ppmv dry SO2, 10 vol% dry O2, and 10 vol% dry CO2. All tests were conducted with a fly ash obtained from a coal-fired utility boiler firing an eastern bituminous coal. The fly ash feed rate was 4.5 kg/hr (solids loading of 90.6-104.7 gm/dcm ). Mercury removal was determined from the mercury feed rate, the solids (carbon and fly ash) feed rate, and mercury analysis of the feed and recovered solids (by combustion followed by cold vapor atomic absorption spectroscopy). Except where noted, all mercury removal results discussed in this paper include mercury removal by the carbon sorbent and the fly ash. A more detailed description of the pilot test unit is given elsewhere (27]. 

As it is nearly impossible to make any general kinetic description of the gasification processes as a practical design basis, constrained equilibrium calculations offer a useful tool for comparative studies [51]. If gasification reaction rates are considered as a rate of approach to chemical equilibrium, increasing residence times lead to gasification products near equilibrium [52]. This is especially true for fluidized-bed and entrained-flow processes. Because the equilibrium state does not depend on the path used to achieve it, a process simulator such as Aspen Plus [49] can use a hypothetical reactor to decompose coal into its elements. The subsequent equilibrium calculation can be carried out, including other feed streams. 

This completes our description of the Aspen H YSYS Petroleum Refining model. In subsequent sections, we discuss issues of thermophysical properties, fractionation and feed lumping. These issues are not specific to a simulation program and apply generally to any model of a reforming process. 

The non-isothermal erosion rigs are easy to fabricate but they fail to simulate the erosion conditions. Hence, such rigs presently are not popular. In contrast, isothermal type erosion rigs can simulate erosion conditions but are difficult to fabricate. A schematic diagram of one such erosion rig fabricated by the author at DMRL is shown in Fig. 6.2a. The unique feature of this rig is its ability to alter the particle feed rate by over 100 times. Its particle feeding system is a miniaturized conveyer belt system and the particle feed rate is controlled by controlling the speed of the motor of the system. A further description of this rig is available elsewhere [14]. 

---