Crossing Reaction Equilibrium in an Adiabatic Reactor System

Abstract

The work presented in this paper looks at maximizing the conversion of an exothermic reversible reaction that is adiabatic overall, i.e. only allowing for internal heat exchange between streams. In a single adiabatic reactor the highest possible conversion is the equilibrium conversion. It is shown that an improvement can be made on this equilibrium conversion by using two reactors with two heat interchanging units. The heat interchange system can be further optimized by adding more reactors and heat interchangers. The optimum theoretical conversion for an adiabatic system was found to be the equilibrium conversion at the original feed temperature. This is achieved by operating a simultaneous heat interchanging and reactor structure. The work was extended to find a maximum conversion for a more practical system where account is taken of minimum temperature driving forces and incomplete conversions.

Operating envelope of Haber–Bosch process design for power-to-ammonia

“… 16 For design only, the reaction is considered to be accomplished when reaching 90% of the equilibrium composition, as for equilibrium conversion operation an infinite amount of reactor space is required. 29 Also, the reactants and the product present in purge stream were assumed to be lost. The breakdown of the reactor system for each catalyst bed volume and feed flow rate is shown in Table 2 .…”

“…This is accomplished through the use of several catalyst beds in series. 29 The usual operational envelope ranges are: pressure of 150 to 300 bar, temperature of 623 to 773 K, H 2 -to-N 2 molar ratios of 2 : 1 to 3 : 1 and inert gas content from 0 to 15 mol%. 1 The operational envelopes mentioned above for carrying out the ammonia synthesis reaction are quite general, and vary greatly.…”

Geometry and reactor synthesis: maximizing conversion of the ethyl acetate process

“…One critical issue here is: how much should one preheat the feed material? Geometrically, it be shown that any optimum configuration only occurs when the temperature at point (G) is the same as that at point (C) [5]. Point (x) has a conversion of 0.55, while point (G) has a conversion value of 0.73.…”

Optimisation of the Autothermal NH3 Production Process for Power-to-Ammonia

“…Cheema and Krewer tailored the volume of the catalyst beds along with intermediate flow rates with regard to maximum reactants' conversion fed at stoichiometric ratio (3 mol of H 2 to 1 mol of N 2 ) and operational temperature span, 673 to 773 K or 90% of the equilibrium temperature, see Figure 4. The reactor systems are preferably designed for operation up to 90% of the equilibrium composition that is mainly to avoid the infinite amount of reactor space requirement for accomplishing equilibrium conversion [32]. For comparison among performance of the reactor systems, the volume of catalyst beds, the initial conditions, the total process feed composition, and flow rate are kept constant for all the reactor systems and are taken from Cheema and Krewer [20]; see Table 1.…”

“…For the catalyst beds of each reactor system, T b out is the outlet temperature limited by the constraint. For bed b ∈ {1, 2}, T b out is maintained to 773 K and for bed 3, exit temperature is maintained to 90 % of the equilibrium temperature T EQ to limit the catalyst bed size [32]. The effectiveness ε HE of heat exchangers HE ∈ {1, 2, 3} of the respective reactor system are calculated by Equations (5) and/or (6) at optimum design conditions, and are later used in the off-design performance analysis for identifying the unknown stream temperatures.…”