Difference between revisions of "Chemical reactor"
(more to come: examples of reactors, how they are used, etc.) |
(added batch reactor) |
||
| Line 3: | Line 3: | ||
The [[design equation]] for a chemical reactor is based directly on the [[general balance equation]] | The [[design equation]] for a chemical reactor is based directly on the [[general balance equation]] | ||
| − | :<math>F_{j0} - F_j + \int^V{r_jdV} = \frac{dN_j}{dt}</math> | + | :<math>F_{j0} - F_j + \int^V{r_jdV} = \frac{dN_j}{dt}</math><ref name="fogler">Fogler, H. Scott. ''Elements of Chemical Reaction Engineering, 4e''. Pearson Education: 2006.</ref> |
where | where | ||
| Line 9: | Line 9: | ||
:F<sub>j0</sub> is the molar flow rate into the system of species j | :F<sub>j0</sub> is the molar flow rate into the system of species j | ||
:F<sub>j</sub> is the molar flow rate out of the system of species j | :F<sub>j</sub> is the molar flow rate out of the system of species j | ||
| − | :r<sub>j</sub> is the [[rate equation|rate of | + | :r<sub>j</sub> is the [[rate equation|rate of appearance]] of species j<ref>Since the design equation is performed on a reactant, the rate of appearance is actually negative. For this reason -r<sub>j</sub> is often substituted, to represent dissapearance of the reactant.</ref> |
:V is [[volume]] in which the reactor takes place | :V is [[volume]] in which the reactor takes place | ||
:N<sub>j</sub> is the number of [[mole]]s of species j | :N<sub>j</sub> is the number of [[mole]]s of species j | ||
| − | The design equation is | + | The design equation is typically performed on the [[limiting reactant]] of a reaction. |
| + | ==Batch Reactor== | ||
| + | A ''batch reactor'' is the simplest form of a chemical reactor. A batch reactor is simply a vessel of fixed or variable volume which has no material flows into or out of the system. A batch reactor could be as small as a [[beaker]] in a chemistry lab, or as large as a 1,000 gallon fermenter in a large scale [[beer|brewery]]. | ||
| + | |||
| + | ===Design Equation=== | ||
| + | Since batch reactors have no in or out flows, F<sub>j0</sub> and F<sub>j</sub> are both equal to 0. If the reactor is assumed to be [[well mixed]], then there are no spacial variations of r<sub>j</sub> (in other words, r<sub>j</sub> is a constant and can be taken outside of the [[integral]]. Thus, the design equation for a batch reactor is | ||
| + | |||
| + | :<math>r_jV = \frac{dN_j}{dt}</math>. | ||
| + | |||
| + | ===Uses=== | ||
| + | Batch reactors are useful for | ||
| + | *small-scale operations | ||
| + | *testing new processes | ||
| + | *manufacturing expensive products | ||
| + | *very slow processes (such as [[biology|biological]] reactions) | ||
| + | |||
| + | ==Notes== | ||
| + | <references /> | ||
[[Category:Chemical Engineering]] | [[Category:Chemical Engineering]] | ||
Revision as of 20:41, October 29, 2007
A chemical reactor is a process unit which combines one or more chemicals into another by promoting a chemical reaction. Reactors can be run as flow systems or as batch systems.
The design equation for a chemical reactor is based directly on the general balance equation
- <math>F_{j0} - F_j + \int^V{r_jdV} = \frac{dN_j}{dt}</math>[1]
where
- j is a specific species (chemical) in the system
- Fj0 is the molar flow rate into the system of species j
- Fj is the molar flow rate out of the system of species j
- rj is the rate of appearance of species j[2]
- V is volume in which the reactor takes place
- Nj is the number of moles of species j
The design equation is typically performed on the limiting reactant of a reaction.
Batch Reactor
A batch reactor is the simplest form of a chemical reactor. A batch reactor is simply a vessel of fixed or variable volume which has no material flows into or out of the system. A batch reactor could be as small as a beaker in a chemistry lab, or as large as a 1,000 gallon fermenter in a large scale brewery.
Design Equation
Since batch reactors have no in or out flows, Fj0 and Fj are both equal to 0. If the reactor is assumed to be well mixed, then there are no spacial variations of rj (in other words, rj is a constant and can be taken outside of the integral. Thus, the design equation for a batch reactor is
- <math>r_jV = \frac{dN_j}{dt}</math>.
Uses
Batch reactors are useful for
- small-scale operations
- testing new processes
- manufacturing expensive products
- very slow processes (such as biological reactions)