Model development reforming

This section examines some experimental evidence for the transient behavior of individual cells evaluated on single-cell test stands and stacks contained within full systems. Results from models developed to help understand some of the detailed physical effects that influence cell performance are also examined. The goal is to introduce, albeit in brief, some of the principle dynamic characteristics of single cell and full stack performances. Single cell studies are important since they isolate the cell in a well understood and controlled environment thereby removing the effects of other external processes (e g., reforming) which may have their own transient behavior that affects cell operation (e g., controlling cell input fuel composition). Such... 

Finally, the question rises whether an accurate simulation of the reformer tubes does not have to include consideration of radial gradients. The two dimensional model developed for this purpose in this work neglects interfacial gradients, for reasons explained already above, but maintains the mass transfer limitations inside the catalyst, of course. 

Model development for steam reformers Modelling of side fired furnaces Modelling of top fired furnaces Modelling of methanators Modelling of the catalyst pellets for steam reformers and methanators using the dusty gas model Computational algorithm... 

The models developed for steam reformers have been checked against a number of industrial units in Egypt and Saudi Arabia. The comparison of the models with industrial reactors is supplemented with the comparison of the different models for a case which is far from thermodynamic equilibrium. A sample of the results for the two industrial steam reformers (1, II) are presented. 

The next task was to model the reformer itself to understand design issues and be able to predict performance of various reactor/catalyst types and transient behavior. However, upon trying to obtain kinetic rate expressions for the reforming reactions, it was found that very little information existed in the public domain. This led to the decision/need to develop reaction kinetics for catalytic partial oxidation and steam reforming at National Energy Technology Laboratory s (NETL s) onsite research facility. 

Kinetic Measurements Preliminary studies have been conducted for the kinetic model development for the autothermal reforming of diesel fuel. Three... 

Developed a 3-D single-phase model for reformate feed in the anode. 

Precise comparisons between packed beds and ceramic foam structures are complex since many factors - activity, effectiveness factors, mass and heat transfer, and pressure drop - are all interdependent. We have simulated the performance of a conventional steam reformer and compared it to one containing a ceramic foam cartridge loaded to achieve equivalent intrinsic activity per gram of catalyst. A 1-D model developed and tested previously for heat-pipe reformers with isothermal walls was used [57]. Pressure drop, mass transfer and heat transfer correlations for the packed bed were known to be accurate for commercial catalysts those used for the foam were determined in the studies described above. Process conditions and results are given in Table 7. 

Catalytic reforming models developed by Kmak and Ramage et al. give a fairly detailed description of the process. In Powell s hydrocracking modeP, the chemical composition parameters are continuous functions of carbon numbers. Quann and Krambeck developed a kinetic model for olefin oligomerization over the ZSM-5 catalyst. 

Based on the experimental data of the C02-selective facUitated transport membranes described earlier in this chapter, we proposed the concept of C02-selective WGS membrane reactor and developed a one-dimensional nonisothermal model to simulate the reaction and transport process (Huang et al., 2005a). The modeling results have shown that H2 enhancement and CO reduction to 10 ppm or lower are achievable for autothermal reforming synthesis gas via CO2 removal. With this model, we have elucidated the effects of system parameters on the membrane reactor performance. Using the membrane synthesized and the commercial WGS catalyst, we have obtained a CO concentration of less than 10 ppm in the H2 product in WGS membrane reactor experiments and verified the model developed (Huang et al., 2005b Zou et al., 2007). 

A secondary issue relates to the cahbrahon and predichons from the rigorous reformer model. It is crihcal to ensure that the hydrogen balance is satisfactorily closed before beginning model development We define the hydrogen balance as follows ... 

A well-calibrated model produces significant and repeatable predictions over a wide range of operating conditions. Table 5.13 to Table 5.16 summarize the predictions from model developed and calibrated according the previous sections. Each validation case represents roughly one month intervals of the reformer. 

Many reformers are now part of integrated petrochemical complexes and produce aromatics (benzene, toluene and xylenes or BTX) to feed into chemical processes for polystyrene, polyesters and other commodity chemicals. As such, it is important to consider how models can help in optimizing the BTX operation. Model developers and users must also be aware that complete BTX operation may not be the most profitable reformer operation scenario. Economic analyses are required to justify changes from a gasoline-producing to a BTX-producing scenario. 

In the following workshops, we demonstrate how to organize data, build and calibrate a model for a catalytic reformer using Aspen HYSYS Petroleum Refining. We discuss some key issues in model development and how to estimate missing data required by Aspen HYSYS Petroleum Refining. We divide this task into four workshops ... 

Nature as model for micro-reactor development general advantages of micro flow onset of industrial interest micro heat exchanger vision of mefhanol-fuel reforming costs stiU too prohibitive [231],... 

Ghezell-Ayagh et al. (1999) Development of a stack simulatioin model for control study on direct reforming molten carbonate fuel cell power plant, IEEE Trans. Energy Conversion, Vol. 14, No. 4. 

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