323
the reactants takes place. At temperatures of 1000 °C and above the stoichiometric
formation of H 2 and CO by the DRM reaction, given by reaction number 2 in
Table 2, is achieved. In contrast, the undesirable carbon yield decreases with
increase in temperature and so does the yield of water (Fig. 2). To explain the
variations of H 2 , CO, H 2 O and solid-carbon with temperature, at temperatures lower
than 1000 °C, we need to consider at least three independent reactions, which may
include the DRM reaction, a reaction involving H 2 O (e.g. WGS or RWGS) and one
involving solid-carbon (e.g. methane cracking). Our results shown in Figs. 1 and 2
are in agreement with those of Pakhare and Spivey [8].
Though coke is produced in significant amounts at temperatures less than
1000 °C, it is possible to decrease its presence by considering different reactor setups. For example, coke formation and its removal can be stoichiometrically
represented by reactions 5 and 6 below (Table 3).
Thus, for lower coking rate, reactions 5 and 6 should proceed, such that the net
rate of coke formation is very small or negligible. This suggests that reaction 5
should proceed at a rate equal to reaction 6. Interestingly, experimental results
validate this prediction. Ginsburg et al. studied dry reforming of methane in a CREC
riser over 20 wt% Ni/USY-zeolite catalyst and found that as CH 4 /CO 2 ratio increases,
the moles of coke formed per mole of methane converted increases [9]. An increase
in the CH 4 /CO 2 reaction is expected to increase reaction 5 relative to 6.
One possibility to overcome carbon deposition is to carry out the reaction in a
recycle reactor with low per pass conversion to lower coke formation. In the recycle
Fig. 2 Effect of temperature on product distribution of DRM at thermodynamics equilibrium
condition. The DRM and carbon formation reactions have been modelled in ASPEN PLUS™.
Inlet moles: F CH4 = 1 mol/h and F CO4 = 1 mol/h
Flue Gas Treatment via Dry Reforming of Methane
the reactants takes place. At temperatures of 1000 °C and above the stoichiometric
formation of H 2 and CO by the DRM reaction, given by reaction number 2 in
Table 2, is achieved. In contrast, the undesirable carbon yield decreases with
increase in temperature and so does the yield of water (Fig. 2). To explain the
variations of H 2 , CO, H 2 O and solid-carbon with temperature, at temperatures lower
than 1000 °C, we need to consider at least three independent reactions, which may
include the DRM reaction, a reaction involving H 2 O (e.g. WGS or RWGS) and one
involving solid-carbon (e.g. methane cracking). Our results shown in Figs. 1 and 2
are in agreement with those of Pakhare and Spivey [8].
Though coke is produced in significant amounts at temperatures less than
1000 °C, it is possible to decrease its presence by considering different reactor setups. For example, coke formation and its removal can be stoichiometrically
represented by reactions 5 and 6 below (Table 3).
Thus, for lower coking rate, reactions 5 and 6 should proceed, such that the net
rate of coke formation is very small or negligible. This suggests that reaction 5
should proceed at a rate equal to reaction 6. Interestingly, experimental results
validate this prediction. Ginsburg et al. studied dry reforming of methane in a CREC
riser over 20 wt% Ni/USY-zeolite catalyst and found that as CH 4 /CO 2 ratio increases,
the moles of coke formed per mole of methane converted increases [9]. An increase
in the CH 4 /CO 2 reaction is expected to increase reaction 5 relative to 6.
One possibility to overcome carbon deposition is to carry out the reaction in a
recycle reactor with low per pass conversion to lower coke formation. In the recycle
Fig. 2 Effect of temperature on product distribution of DRM at thermodynamics equilibrium
condition. The DRM and carbon formation reactions have been modelled in ASPEN PLUS™.
Inlet moles: F CH4 = 1 mol/h and F CO4 = 1 mol/h
Flue Gas Treatment via Dry Reforming of Methane