Reactor volume measurement

It is worth describing other operations where differences between the chemist s laboratory and the chemical engineer s pilot plant and plant create the need for different approaches. Pumping, flow measurement, and reactor volume measurement are a few of the more common operations deserving the chemist s attention. 

Two other specific areas must be mentioned in this introduction the emerging fields of microbial fuel cells and microfluidic fuel cells. In some ways these two new fields can be considered embodiments of low-temperature fuel cells operating at the extreme size scales - microbial fuel cells have their genesis in the exploration of wastewater treatment in electrochemical and bioelectrochemical systems. These proposed applications are by their nature enormous in size, with reactor volumes measured in the tens of cubic meters (many orders of magnitude larger than the conventional low-temperature fuel cells). 

Ca.ta.lysts, Catalyst performance is the most important factor in the economics of an oxidation process. It is measured by activity (conversion of reactant), selectivity (conversion of reactant to desked product), rate of production (production of desked product per unit of reactor volume per unit of time), and catalyst life (effective time on-stream before significant loss of activity or selectivity). 

One quantitative measure of reactor efficiency at a conversion level x is the ratio of the mean residence time or the reactor volume in a plug flow reactor to that of the reactor in question,... 

This matrix will contain information regarding loading characteristics such as flooding hmits, exchanger areas, pump curves, reactor volumes, and the like. While this matrix may be adjusted during the course of model development, it is a boundary on any possible interpretation of the measurements. For example, distillation-column performance markedly deteriorates as flood is approached. Flooding represents a boundary. These boundaries and nonlinearities in equipment performance must be accounted for. 

The previous volume measurement was done by methane because this does not react and does not even adsorb on the catalyst. If it did, the additional adsorbed quantity would make the volume look larger. This is the basis for measurement of chemisorption. In this experiment pure methane flow is replaced (at t = 0) with methane that contains C = Co hydrogen. The hydrogen content of the reactor volume—and with it the discharge hydrogen concentration— increases over time. At time t - t2 the hydrogen concentration is C = C2. The calculation used before will apply here, but the total calculated volume now includes the chemisorbed quantity. 

Space time, ST, is defined as the time required to process one reactor volume of feed measure at specified conditions. The relationship between space velocity SV and ST is as follows ... 

The design optimization of an electrolytic cell aims at a high throughput with a low energy consumption at the lowest feasible cost. The throughput of an electrochemical reactor is measured in terms of the space time yield, Yt, defined as the volumetric quantity of the metal produced per unit time per unit volume of the process reactor. This quantity is expressed as ... 

The reactor volume is taken as the volume of the reactor physically occupied by the reacting fluids. It does not include the volume occupied by agitation devices, heat exchange equipment, or head-room above liquids. One may arbitrarily select the temperature, pressure, and even the state of aggregation (gas or liquid) at which the volumetric flow rate to the reactor will be measured. For design calculations it is usually convenient to choose the reference conditions as those that prevail at the the inlet to the reactor. However, it is easy to convert to any other basis if the pressure-volume-temperature behavior of the system is known. Since the reference volumetric flow rate is arbitrary, care must be taken to specify precisely the reference conditions in order to allow for proper interpretation of the resultant space time. Unless an explicit statement is made to the contrary, we will choose our reference state as that prevailing at the reactor inlet and emphasize this choice by the use of the subscript zero. Henceforth,... 

Like the definition of the space time, the definition of the space velocity involves the volumetric flow rate of the reactant stream measured at some reference condition. A space velocity of 10 hr-1 implies that every hour, 10 reactor volumes of feed can be processed. 

The pilot-scale SBCR unit with cross-flow filtration module is schematically represented in Figure 15.5. The SBCR has a 5.08 cm diameter and 2 m height with an effective reactor volume of 3.7 L. The synthesis gas passes continuously through the reactor and is distributed by a sparger near the bottom of the reactor vessel. The product gas and slurry exit at the top of the reactor and pass through an overhead gas/liquid separator, where the slurry is disengaged from the gas phase. Vapor products and unreacted syngas exit the gas/liquid separator and enter a warm trap (373 K) followed by a cold trap (273 K). A dry flow meter downstream of the cold trap measures the exit gas flow rate. 

Space time (r) is usually applied only to flow situations, and is the time required to process one reactor volume of inlet material (feed) measured at inlet conditions. That is, t is the time required for a volume of feed equal to the volume of the vessel (V) to flow through the vessel. The volume V is the volume of the vessel accessible to the fluid, t can be used as a scaling quantity for reactor performance, but the reaction conditions must be the same, point-by-point, in the scaling. 

Space velocity (Sv) is the reciprocal of space time, and as such is a frequency (time-1) the number of reactor volumes of feed, measured at inlet conditions, processed per unit time. 

An exothermic reaction involving two reactants is run in a semi-continuous reactor. The heat evolution can be controlled by varying the feed rate of one component This is done via feedback control with reactor temperature measurement used to manipulate the feed rate. The reactor is cooled by a water jacket, for which the heat transfer area varies with volume. Additional control could involve the manipulation of the cooling-water flow rate. 

To determine PCT cnrve by volnmetric method at first we have to know mass of analyzed powder (hydride or pnre metal). The typical mass of powder used in volumetric method is in a range 50-500 mg and depends on (reactor volume with volume of connecting pipes, valves, and transdncer). After the mass measurement, the powder is loaded into specimen holder and then it is placed in the Sieverts apparatus reactor. To prevent any oxidation and for safety reason the system must be purged a few times by argon and then evacnated. However, one must be careful how much powder is appropriate for the absorption/desorption volume of a Sieverts-type apparatus. 

RTD studies were carried out by Jagadeesh and Satyanarayana (lEC/PDD 11 520, 1972) in a tubular reactor (L = 1.21 m, 35 mm ID). A squirt of NaCl solution (5 N) was rapidly injected at the reactor entrance, and mixing cup measurements were taken at the exit. From the following results calculate the vessel dispersion number also the fraction of reactor volume taken up by the baffles. 

For the activity tests an 8-fold batch reactor system (reactor volume 20 ml) with magnetic stirring which allows the measurement of hydrogen uptake at constant hydrogen pressure was used. Analysis of substrates and products was performed offline by GC for determining selectivity values. Activity values were derived from hydrogen up-take within a defined time interval. Hydrogenation of both cinnamic acid and dibenzylether were carried out at 10 bars and 25°C. 

The principal difference between homogeneous and heterogeneous reaction rates is that the latter is based on mass, volume, or more rarely, on the area of the solid and not on the fluid-phase volume or reactor volume. The reactor volume or liquid-phase volume is of secondary significance in heterogeneous reactions since the reaction takes place on the solid rather than throughout the reactor volume. Moreover, the mass of the solid is usually used instead of the solid volume or surface, because it is the most easily measured property. 

The behavior of a chemical is investigated in a well-mixed reactor (volume V, flow rate Q) by measuring the outflow concentration Cout at steady-state for different input concentrations Cin. The results are given in the table below, (a) Determine the order of the elimination process and formulate the differential equation which describes the chemical in the reactor, (b) How long does it take for the outflow concentration to drop from 40 mmol-L-1 to 2 mmol-L, if at time tu Cin drops to zero instantaneously ... 

Since in industrial photochemistry mostly polychromatic light sources are used, photon quantities are relatively difficult to calculate and require knowledge of the spectral distribution of the radiometric quantity measured. Assuming on the other hand that the radiometric measurements do not need to be corrected for the spectral response of the probe, the photon irradiance at a given point within the reactor volume would then be given by Eqs. (39) and (40), respectively. 

When the residence time, r, is known from the reactor volume and the volumetric throughput, v, and the temperature inside the reactor is measured, the reaction rate can be determined from the concentration, c, of a component in the reactor, and c in the feed. 

Preventive measures provide conditions where the incident is unlikely to happen, but its occurrence cannot be totally avoided. In this category, we find measures such as inventory reduction for critical substances, the choice of a continuous rather than a batch process leading to smaller reactor volumes, and a semi-batch rather than a full batch process providing additional means of reaction control. Process automation, safety maintenance plans, etc. are also preventative measures. The aim of these measures is to avoid triggering the incident and thus reducing its consequences. In the frame of mnaway risks, a mnaway remains theoretically possible, but due to process control, its severity is limited and the probability of occurrence reduced, such that it can be controlled before it leads to a critical situation. 

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