Stirred tank reactors lines

Figure 5.3-4. Semibatch stirred-tank reactor with alternative feed lines homogeneous reaction.

Homogeneous gas phase reactors will always be operated continuously whereas liquid phase reactors may be batch or continuous. Tubular (pipe-line) reactors are normally used for homogeneous gas-phase reactions for example, in the thermal cracking of petroleum crude oil fractions to ethylene, and the thermal decomposition of dichloroethane to vinyl chloride. Both tubular and stirred tank reactors are used for homogeneous liquid-phase reactions. 

Fig. 22. Heat generation and heat loss lines for an irreversible exothermic reaction in a continuous stirred tank reactor.

If the points lie close to a straight line, this is taken as confirmation that a second-order equation satisfactorily describes the kinetics, and the value of the rate constant k2 is found by fitting the best straight line to the points by linear regression. Experiments using tubular and continuous stirred-tank reactors to determine kinetic constants are discussed in the sections describing these reactors (Sections 1.7.4 and 1.8.S). 

Figure 14. Enhancement of absorption of hydrogen into aqueous hydroxylamine phosphate solutions by catalyst loading of the bulk Tor a stirred-tank reactor. Drawn lines are model calculations with best-fit parameters (from Wimmers and Fortuin [122]).

Catalytic tests in sc CO2 were run continuously in an oil heated flow reactor (200°C, 20 MPa) with supported precious metal fixed bed catalysts on activated carbon and polysiloxane (DELOXAN ). We also investigated immobilized metal complex fixed bed catalysts supported on DELOXAN . DELOXAN is used because of its unique chemical and physical properties (e. g. high pore volume and specific surface area in combination with a meso- and macro-pore-size distribution, which is especially attractive for catalytic reactions). The effects of reaction conditions (temperature, pressure, H2 flow, CO2 flow, LHSV) and catalyst design on reaction rates and selectivites were determined. Comparative studies were performed either continuously with precious metal fixed bed catalysts in a trickle bed reactor, or discontinuously in stirred tank reactors with powdered nickel on kieselguhr or precious metal on activated carbon catalysts. Reaction products were analyzed off-line with capillary gas chromatography. 

In a continuous stirred-tank reactor, eqn 3.20 and the corresponding straight-line plot in Table 3.1 remain valid, and eqn 3.21 for the products becomes... 

Example 2—Unstable CSTR with bounded output. Consider the reaction R P occurring in a nonisothermal jacket-cooled continuous stirred tank reactor (CSTR) with three steady states. A, B, C, corresponding to the intersection points of the two lines shown in Fig. 3 (Stephanopoulos,... 

Graphical methods can be used to obtain the conversion from a series of reactors and have the advantage of displaying the concentration in each reactor. Moreover, no additional complications are introduced when the rate equation is not first order. As an illustration of the procedure consider three stirred-tank reactors in series, each with a different volume, operating as shown in Fig. 4-13<7. The density is constant, so that at steady state the volumetric flow rate to each reactor is the same. The flow rate and reactant concentration of the feed Q and Cq) are known, as are the volumes of each reactor. We construct a graph of the rate of reaction r vs reactant composition. The curved line in Fig. 4- 3b shows how the rate varies with C according to the rate equation, which may be of any order. 

For a stirred-tank reactor, and will represent a point B on the rate line in Fig. 4-136. If Q is located on the abscissa of this figure (point A), a straight line from that point to 5 will have, a slope, of ri/CCj — Cq) = — ri/(Co — Cl). From the equation above, this slope is equal to —QIV, which is known. Flence the conditions in the effluent stream from the first reactor can be found by constructing a straight line from point A with a slope of —QjV and noting the point at which it intersects the rate curve. ... 

A similar analysis for a pulse input would give a response curve of Cpuise vs 0, but this can be obtained more easily by differentiating the J ) curve in Fig. 6-5. From Eq. (6-7), the derivative J B) is proportional to The derivative of the dashed line in Fig. 6-5 will be largest at 0 = 0 and will continually decrease toward zero as 0 increases. Such a distribution curve, given as the dashed line in Fig. 6-6, shows that the most probable [largest J ) d6 residence time is at 0 = 0 for a stirred-tank reactor. 

Laboratory Fischer-Tropsch synthesis tests were performed in a slurry-phase Constant Stirred Tank Reactor. The pre-reduced catalyst (20-30 g) was suspended in ca 300 ml molten Fischer-Tropsch wax. Realistic Fischer-Tropsch conditions were employed, i.e. 220 °C 20 bar commercial synthesis gas feed 50 vol% H2, 25 vol% CO and 25 vol% inerts synthesis gas conversion levels in excess of 50%. Use was made of the ampoule sampling technique as the selected on-line synthesis performance monitoring method [23]. 

An endothermic continuous stirred tank reactor (CSTR) is shown schematically in Figure 15.2. The symbols used in the control schematics are listed in Table 15.1 The controlled variable is the temperature of the product leaving the reactor, and the manipulated variable is the flow rate of steam to the heat exchanger, which adds heat to the recycle line. The final control element is the control valve and associated equipment on the steam hue. The sensor is a temperature sensor/trans-mitter that measures the temperature of the product stream leaving the reactor. The controller compares the measured value of the product temperature with its desired temperature (setpoint) and makes changes to the control valve on the steam to the heat exchanger. The process is the... 

R.T. Echols, J.F. Tyson, Determination of rate constants by a double-line flow injection method incorporating a well-stirred tank reactor, Talanta 41 (1994) 1775. 

A simplified scheme of the RCH/RP unit is presented in Figure 2 [1, 10, 11], The reactor (1) is essentially a continuous stirred tank reactor equipped with a gas inlet, a stirrer, a heat exchanger and a catalyst recycle line. Catalyst and reactants are introduced at the bottom of the reactor. Vent gas is taken from the head of the reactor and from the phase separator. Control of the liquid volume inside the reactor is simple the liquid mixture composed of catalyst solution and aldehydes leaves via an overflow and is transferred to a phase separator (2), where it is partially degassed. The separation of the aqueous catalyst solution (density of the catalyst solution 1100 g/L) and the aldehydes occurs rapidly and completely, favored by the difference in densities (density of aldehyde layer 600 g/L due to dissolved gases). The catalyst solution passes a heat exchanger and produces process steam that is consumed in downstream operations. Some water is extracted from the catalyst solution by its physical solubility in the aldehydes (about 1.3% w/w) which may be replaced before the catalyst solution re-enters the reactor. 

All actual reactors would operate in the shaded area between the two lines. Tubular reactors would be close to the upper line, stirred-tank reactors would be close to the lower line, and packed-tower reactors would be approximately halfway between. 

---