Integral reactor experiments

In subsequent stages validation experiments were performed over monolith catalyst samples at two different scales (i) monolith core samples (up to 10 cm3) in a laboratory rig for integral reactor experiments and (ii) full-scale honeycomb monoliths (up to 43 L in size) in engine test bench runs. 

Reaction Rate Equations from Integral Reactor Experiments... 

In integral reactor experiments, the experimenter 1s limited in extending the range of his observations by the fact that there is a loss of precision when conversions are too high or too low. 

The differential reactor is the second from the left. To the right, various ways are shown to prepare feed for the differential reactor. These feeding methods finally lead to the recycle reactor concept. A basic misunderstanding about the differential reactor is widespread. This is the belief that a differential reactor is a short reactor fed with various large quantities of feed to generate various small conversions. In reality, such a system is a short integral reactor used to extrapolate to initial rates. This method is similar to that used in batch reactor experiments to estimate... 

From a few well chosen experiments in an integral reactor of technical dimensions with side-stream analysis both reaction schemes and the effective heat transfer and kinetic parameters of a reaction model for propylene oxidation could be deduced, from which valuable information for both catalyst development and optimization of the reaction conditions could be obtained. 

The effect of feed composition cycling on the time-average rate and temperature profile was explored in the region of integral conversion in a laboratory fixed bed ammonia synthesis reactor. Experiments were carried out at 400°C and 2.38 MPa over 40/50 US mesh catalyst particles. The effect of various cycling parameters, such as cycle-period, cycle-split, and the mean composition, on the improvement in time-average rate over the steady state were investigated. 

The total acidity deterioration and the acidity strength distribution of a catalyst prepared from a H-ZSM-5 zeolite has been studied in the MTG process carried out in catalytic chamber and in an isothermal fixed bed integral reactor. The acidity deterioration has been related to coke deposition. The evolution of the acidic structure and of coke deposition has been analysed in situ, by diffuse reflectance FTIR in a catalytic chamber. The effect of operating conditions (time on stream and temperature) on acidity deterioration, coke deposition and coke nature has been studied from experiments in a fixed integral reactor. The technique for studying acidity yields a reproducible measurement of total acidity and acidity strength distribution of the catalyst deactivated by coke. The NH3 adsorption-desorption is measured by combination of scanning differential calorimetry and the FTIR analysis of the products desorbed. 

Continuously operated, fixed bed reactors are frequently used for kinetic measurements. Here the reactor is usually a cylindrical tube filled with catalyst particles. Feed of a known composition passes though the catalyst bed at a measured, constant flow rate. The temperature of the reactor wall is usually kept constant to facilitate an isothermal reactor operation. The main advantage of this reactor type is the wealth of experience with their operation and description. If heat and mass transfer resistances cannot be eliminated, they can usually be evaluated more accurately for packed bed reactors than for other reactor types. The reactor may be operated either at very low conversions as a differential reactor or at higher conversions as an integral reactor. 

In the experiments presented in Fig. 4, the catalyst rnass was approximately six times larger than for those shown in Fig. 5- XF5 (x-ray fluoresence spectroscopy) artalysis of the used catalyst shows that this results in a distinct axial Mo-profile, as shown in Fig. 6 for similar experiments. In this case the degree of fcductioo does not have the major influence on the activity. Instead, the rate of the loss of catalyst mass becomes determining. The long term deactivation of the catalyst was found to occur concurrently with the loss of Mo from the catalyst (ref. 7,S). This has been determined using a modified integral reactor (multibasket reactor) where, after the deactivation experiments the baskets can be separated and analyzed separately. Fig. 6 shows the Mo/P profile measured at different times on stream. Depicted there is the molar Mo/P ratio of the deactivated catalyst from different axial positions in the multibasket reactor, normalized with the Mo/P ratio of the fresh catalyst It is dearly seen that Mo is lost mainly in the inlet section, while no Mo loss was found in the outlet section of the reactor. 

The data used for parameter estimation were from experiments wth very short gas residence times and generally low conversions. In order to check the validity of the derived expressions, we also carried out experiments at higher residence times. The proposed model reaction rate expressions eq.8, 9 and 10 were used to predict the integral reactor behavior under the following assumptions ... 

A proper fit of the time-courses of some batch reactor experiments at different starting concentrations represents an appropriate test of the rate equation. This implies that numerical integration of the rate equation (e. g. by the Runge Kutta method11121), yielding a simulated time-course, has to fit the data of the measured time-course over the whole range of conversion (compare to Fig. 7-17 B). Examples of these methods will be given after the presentation of the basic kinetic models. 

These equations also lead to a constant value for k, which confirms that the reaction has second-order kinetices. Peterson [2] has discussed further aspects of differential versus integral fitting of data from batch reactor experiments. 

Unlike the known designs of integral reactors being under development in many countries where either steam or steam-gas pressurizer is applied, the integral reactors developed by RDIPE use a gas pressurizer. Selection of such solution was motivated by several reasons, firstly, the intention to simplify and, consequently, enhance safety of the primary circuit pressure compensation system by elimination of heaters and sprinkler system. Secondly, this approach is based on our 40-year experience in designing and operation of ship-mounted NSSS with gas pressurizers in the primary circuit. It should be pointed out, however, that in the previous cases the pressurizes wee placed outside the reactor vessel. 

In the initial rate study three parameters temperature, space-time and total pressure have been varied systematically while the inlet composition was kept constant using an O2/CH4 ratio, lower than the stoichiometry. On the other hand in the integral reactor the space-time of methane, the inlet mol fractions ycH4, yo and the temperature were the variables of the experiments carried out under atmospheric pressure. 

The safety design concept of a power unit with the VBER-150 was selected via the application of a system approach integrating the experience and recent achievements in safety of nuclear power plants and shipboard reactors it meets the requirements for plant location near populated areas and incorporates an enhanced resistance to possible acts of sabotage. 

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