What is the leanest stream to sustain a nonadiabatic loop reactor: Analysis and methane combustion experiments

Abstract

While previous studies experimentally demonstrated that loop reactor (LR) can be sustained with a lean feed (using ethylene combustion) and have analyzed the single‐reaction adiabatic case, this work analyzes the effects of heat loss and of reactor size to determine the leanest stream (expressed in terms of adiabatic temperature rise ΔTlim) that will sustain the operation. For an adiabatic infinitely long reactor ΔTlim→0 while for a finite reactor ΔTlim scales as (1 + Pe/4)−1 where Pe = Luρcpf/k, and heat loss increases this limit by (β/Pe)1/2. Thus, a good design of a LR will aim to decrease conductivity (k) and radial heat‐transfer coefficient (β) while increasing throughput (u) and reactor length. This article is also the first experimental demonstration of auto‐thermal operation in a LR for catalytic abatement of low‐concentration of methane, showing the leanest stream to be of 8000 ppm vs. 33,000 ppm in a once‐through reactor. Experimental combustion results of methane and of ethylene are compared with model predictions. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2030–2042, 2017

Dynamics and control of loop reactors - a review

“…This system was successfully validated for an adiabatic long reactor [9]. In the following studies the effect of heat losses [17] as well as the effects of finite length BC and of incomplete conversion [21,32] were accounted for.…”

“…This reaction can be carried out at a relatively low temperature (∼200 C), and our group proceeded to demonstrate this concept with methane combustion which requires a maximal temperature of 600 C or so [21]. The englishTITLE WILL BE SET BY THE PUBLISHER experimental system incorporates three fixed-bed reactors arranged in the form of a loop.…”

“…Decreasing the feed flow rate causes a decline in the maximal temperature (Fig. The analysis of the effects of the heat loss and of the reactor size on the leanest stream (expressed in terms of the adiabatic temperature rise ∆T lim a ) that will sustain the operation shows the following [21]: For an adiabatic infinitely long reactor ∆T lim a → 0 while for a finite reactor ∆T lim a scales as (1+Pe y /4)-1 with Pe y defined via the reactor length (Eq. 8); the heat loss increases this limit by (βP e y ) 1/2 where β = 2U z 0 /(r w (ρc p ) f u 0 is the dimensionless heat transfer coefficient.…”

Reverse flow reactors as sustainable devices for performing exothermic reactions: Applications and engineering aspects

“…It should be noted that two reactions of different heat of reaction, but the same adiabatic temperature rise, may exhibit a similar thermal performance in a reverse flow reactor. The first question in the design of a reverse flow reactor is determining the minimum feed concentration necessary to achieve autothermal operation [139]. The heat storage efficiency (η th ) is defined as the ratio of the heat stored in the reactor between cycles (Q st ) and the total amount of heat that can be theoretically stored, i.e.…”

Nonlinear Dynamics in Chemical Reaction Engineering: In Celebration of Moshe Sheintuch's 70th Birthday

“…Moshe's experiments revealed the existence of such patterns in a packed bed catalytic reactor, a workhorse of chemical industry (6)(7)(8). In addition to explaining how such patterns arise through the interplay of interphase transport and chemistry, he proposed several strategies for harnessing these patterns in novel reactor configurations (9)(10)(11)(12)(13)(14). These are just two key examples from the list of Moshe's contributions to nonlinear analysis of chemical reactors.…”