temperature change) Single reaction occurring in the bulk of the fluid (homogeneously). A material balance on the differential volume of a fluid element, or plug, on species i of axial length dx between x and x + dx gives: [accumulation] = [in] - [out] + [generation] - [consumption] Accumulation is 0 under steady state; therefore, the above mass balance can be re-written as follows: 1. . where: x is the reactor tube axial position, m dx the differential thickness of fluid plug the index i refers to the species i Fi(x) is the molar flow rate of species i at the position x, mol/s D is the tube diameter, m At is the tube transverse cross sectional area, m2 ν is the stoichiometric coefficient, dimensionless r is the volumetric source/sink term (the reaction rate), mol/m3s. The flow linear velocity, u (m/s) and the concentration of species i, Ci (mol/m3) can be introduced as: and where is the volumetric flow rate. On application of the above to Equation 1, the mass balance on i becomes: 2. . When like terms are cancelled and the limit dx → 0 is applied to Equation 2 the mass balance on species i becomes 3. , The temperature dependence of the reaction rate, r, can be estimated using the Arrhenius equation. Generally, as the temperature increases so does the rate at which the reaction occurs. Residence time, , is the average amount of time a discrete quantity of reagent spends inside the tank. Assume: isothermal conditions, or constant temperature (k is constant) single, irreversible reaction (νA = -1) first-order reaction (r = k CA) After integration of Equation 3 using the above assumptions, solving for CA(x) we get an explicit equation for the concentration of species A as a function of position: 4. , where CA0 is the concentration of species A at the inlet to the reactor, appearing from the integration boundary condition. Operation and uses PFRs are used to model the chemical transformation of compounds as they are transported in systems resembling "pipes". The "pipe" can represent a variety of engineered or natural conduits through which liquids or gases flow. (e.g. rivers, pipelines, regions between two mountains, etc.) An ideal plug flow reactor has a fixed residence time: Any fluid (plug) that enters the reactor at time will exit the reactor at time , where is the residence time of the reactor. The