Coking rate measurements

A new reactor concept for the study of catalyst deactivation is presented, it consists of the combination of an electrobalance and a recycle reactor. With the electrobalance, the coke content on the catalyst is measured continuously. The recycle reactor operates gradientlessly at high conversion, with on-line gas chromatographic analysis of the effluent. Thus, the catalyst activity and product selectivities may be coupled directly with the coke content and the coking rate on the catalyst. 

Since DBT does not affect the coking rate, it is possible to measure HDS activity while coking the catalyst with pyrene. Results are shown in Fig. 7 for three repeat tests of HDS activity as a function of run length. The three tests were operated for different periods of time 40 hours, 65 hours and 110 hours. The resultant levels of carbon for the samples aged 40 and 110 run hours fit (9.5% wt and 13.5% wt, respectively) the data in Fig. 6 perfectly. However, the carbon level found for the 65 run hour aged sample was somewhat larger than expected, 15.7% wt vs. the expected 12.5% wt. The reason for deposition of the additional coke is unresolved. The data in Fig. 7 (solid boxes) show an unexpected activity drop between run hour 40 and 50. This activity drop is most likely caused by coke deposition on the catalyst (coke is the only source of deactivation during these runs ). We... 

Example 9.12 A packed absorption tower is designed to removed SO2 from a coke oven stack. The stack gas flow rate measured at one atmosphere and 30°C is lOmVs, and the SO2 content is 3.0%. Using an initially pure water, 90% removal is desired. The equilibrium curve of SO2 in water may be approximated by y = 30ji . Determine the water requiranent if 150% of the minimum flow rate is deemed adequate. Calculate the height of the tower. Assume KyfU =0.024 kgmols/m s mol fraction. Assume the total cross-sectional area of tower equals 11.0 m. ... 

The Tapered Element Oscillating Microbalance (TEOM) reactor has recently been applied to study deactivation of zeolite catalysts [7,8]. The main advantage of the TEOM reactor is that all gases in the reaction mixture are forced to flow through the catalyst bed as in a conventional fixed-bed reactor. Coupled with on-line gas chromatography, the catalyst activity, selectivity and coking rate can be measured simultaneously as a fimction of the amount of coke on the catalyst. Hence, the TEOM represents a unique way of studying the effect of coke deposition in detail. 

The only unknown parameter left in Eq. (o) is the tortuosity factor, r. This factor was determined from a comparison between the experimental rate at zero coke content, measured in a differential reactor and the surface fluxes. The latter were calculated using Pick s law and for a given t from the concentration profiles obtained by numerical integration of the system (Eqs. (g), (h), (i), and (j)). A value of T = 5 led to the best fit of all six experiments. This is the generally accepted value for the tortuosity factor in a catalyst of the type used in this work. It was also possible to calculate an effectiveness factor from these results. A value of 0.20 was obtained for a particle radius of 2.3 mm at 550°C. The Bischoff general modulus approach, presented in Chapter 3, leads to a value ofO.28. Finally, the heat transfer coefficients were calculated from the correlation of Handley and Heggs, mentioned in Chapter 3. 

Z. L. Liu et al., Discussion on Measures and Potentials of Coke-Rate Reduction of Blast Furnace, Journal of Hunan University of Technology, 24(2010), 1-4. 

Free-swelling tests are commonly used to measure a coal s caking characteristics. A sample of coal is packed in a cmcible or tube, without compaction, and heated at a fixed rate to about 800°C. Infusible coals distill without changing appearance or state of agglomeration. The fusible coals soften, fuse, and usually sweU. The profile of the resultant coke is compared to a series of reference profiles so that a swelling index can be assigned. The profiles represent indexes between 0 and 9. The best cokes come from coals having indexes between 4 and 9. 

Using a "home made" aneroid calorimeter, we have measured rates of production of heat and thence rates of oxidation of Athabasca bitumen under nearly isothermal conditions in the temperature range 155-320°C. Results of these kinetic measurements, supported by chemical analyses, mass balances, and fuel-energy relationships, indicate that there are two principal classes of oxidation reactions in the specified temperature region. At temperatures much lc er than 285°C, the principal reactions of oxygen with Athabasca bitumen lead to deposition of "fuel" or coke. At temperatures much higher than 285°C, the principal oxidation reactions lead to formation of carbon oxides and water. We have fitted an overall mathematical model (related to the factorial design of the experiments) to the kinetic results, and have also developed a "two reaction chemical model". 

The best human studies on chemicals and cancer manage to avoid the problems Feinstein described and also measure differences in cancer rates of greater than 1 percent (Lave and Ennever 1990). The most famous of those studies examined the relationship between cigarette consumption and cancer in British physicians (Doll and Hill 1964 Doll and Peto 1978). Researchers also have calculated solid dose-response relationships for coke-oven emissions, aromatic amines, aflatoxin, vinyl chloride, radiation (including radon), and asbestos (Zeise, Wilson, and Crouch 1987, 275-89). ... 

Other related work in surface area was the phosporic acid-dichromate oxidation of coke by Riley. In an early paper (2), on the basis of reaction rates on different particles sizes, Riley suggested that coke smaller than 60 mesh had no available internal area. Later (1) Riley reversed himself and suggested that different cokes had different amounts of available internal area. In this paper both vapor absorptions and reactivity measurements were made on different cokes. However, no correlation was found between these two items. 

Kulai Kini Were any strength measurements made on cokes formed at high rates of heating ... 

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