Samenvatting
A fundamental continuum-based numerical model was developed to simulate a non-isothermal non-adiabatic reactor which does not employ any empirical closures. The model was able to capture unique features of an exothermic catalytic reactor such as parametric sensitivity, hot-spot formations and multiplicity of steady states. Furthermore, the model inherently accounts for the various aspects of classical phenomenological models such as axial and radial dispersion of heat and mass and the intrinsic coupling of heat and mass transport between the fluid phase and the solid phase. The numerical procedure was validated with existing literature data before moving on to the simulation of a bed consisting of 340 spherical particles packed using the Discrete Element Method. Five simulations were performed by varying the rate of reaction and keeping all other parameters constant to capture the ignition/extinction phenomena exhibited by exothermic packed bed reactors.
| Originele taal-2 | Engels |
|---|---|
| Artikelnummer | 123641 |
| Aantal pagina's | 16 |
| Tijdschrift | Chemical Engineering Journal |
| Volume | 385 |
| DOI's | |
| Status | Gepubliceerd - 1 apr. 2020 |
Financiering
This work was supported by the Netherlands Center for Multiscale Catalytic Energy Conversion (MCEC), an NWO Gravitation programme funded by the Ministry of Education, Culture and Science of the government of the Netherlands. This work was carried out on the Dutch national e-infrastructure with the support of SURF Cooperative. The authors thank SURF SARA ( www.surfsara.nl ) and NWO for the support in using the Cartesius supercomputer. Appendix A The 1-D heterogeneous plug-flow model used for comparison with the DNS results assuming steady state for the fluid phase concentration reads (57) v x ∂ C f ¯ ∂ x = D ax ∂ 2 C f ¯ ∂ x 2 + ( 1 - ε ) 3 R sp k m ( C s ¯ - C f ¯ ) The fluid phase temperature reads (58) ρ f C pf v x ∂ T f ¯ ∂ x = k ax ∂ 2 T f ¯ ∂ x 2 - h w 2 R cyl ( T f ¯ - T cyl ) + ( 1 - ε ) 3 R sp h f ( T s ¯ - T f ¯ ) The particle phase concentration reads (59) 0 = D s 1 r 2 ∂ ∂ r r 2 ∂ C s ¯ ∂ r - k C s ¯ The particle phase temperature reads (60) 0 = k s 1 r 2 ∂ ∂ r r 2 ∂ T s ¯ ∂ r - k C s ¯ ( Δ H ) The boundary conditions used for closing the above system of governing equations are (61) C f ¯ ( x = 0 ) = c o ; ∂ C f ¯ ∂ x ( x = L ) = 0 (62) T f ¯ ( x = 0 ) = T o ; ∂ T f ¯ ∂ x ( x = L ) = 0 (63) - D s ∂ C s ¯ ∂ r ( r = o ) = 0 ; - D s ∂ C s ¯ ∂ r ( r = R sp ) = k m ( C s ¯ - C f ¯ ) (64) - k s ∂ T s ¯ ∂ r ( r = o ) = 0 ; - k s ∂ T s ¯ ∂ r ( r = R sp ) = h f ( T s ¯ - T f ¯ ) 3 empirical correlations are used for estimating D ax , k ax , h f , k m , h w to complete the above described 1-D model. The Edwards and Richardson [56] correlation to estimate the axial dispersion coefficients (65) D ax = 0.73 D f + 0.5 v in d sp 1 + 9.7 D f v in d sp and assuming D ax D f = k ax k f . The Edwards and Richardson [55] correlation to estimate the fluid to particle heat and mass transfer coefficients (66) Nu = ( 7 - 10 ε + 5 ε 2 ) ( 1 + 0.7 Re 0.2 Pr 0.33 ) + ( 1.33 - 2.4 ε + 1.2 ε 2 ) Re 0.7 Pr 0.33 with Nu = Sh for cases when Pr = Sc wherein we have Nu = h f ( 2 R sp ) k f and Sh = k m ( 2 R sp ) D f . The correlation by Yagi and Wakao [57] is used for estimating the wall-to-bed heat transfer with the wall Nusselt number ( Nu w ) given by (67) Nu w = 0.6 Re 0.5 ( Re < 40 ) ; Nu w = 0.2 Re 0.8 ( Re > 40 ) where Nu w = h w ( 2 R sp ) k f .
| Financiers | Financiernummer |
|---|---|
| MCEC | |
| Netherlands Center for Multiscale Catalytic Energy Conversion | |
| Surf, Stichting | |
| Surf, Stichting | |
| Ministerie van OCW | |
| Nederlandse Organisatie voor Wetenschappelijk Onderzoek |