CA2333549A1 - Method for adaptive control of exothermal catalytic reactors and reactors therefor - Google Patents
Method for adaptive control of exothermal catalytic reactors and reactors therefor Download PDFInfo
- Publication number
- CA2333549A1 CA2333549A1 CA002333549A CA2333549A CA2333549A1 CA 2333549 A1 CA2333549 A1 CA 2333549A1 CA 002333549 A CA002333549 A CA 002333549A CA 2333549 A CA2333549 A CA 2333549A CA 2333549 A1 CA2333549 A1 CA 2333549A1
- Authority
- CA
- Canada
- Prior art keywords
- reactors
- component
- reactor
- different
- exothermal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/24—Stationary reactors without moving elements inside
- B01J19/248—Reactors comprising multiple separated flow channels
- B01J19/2485—Monolithic reactors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/008—Details of the reactor or of the particulate material; Processes to increase or to retard the rate of reaction
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
- B01J8/0285—Heating or cooling the reactor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
- B01J8/06—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds in tube reactors; the solid particles being arranged in tubes
- B01J8/067—Heating or cooling the reactor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
- B01J2208/00008—Controlling the process
- B01J2208/00017—Controlling the temperature
- B01J2208/00026—Controlling or regulating the heat exchange system
- B01J2208/00035—Controlling or regulating the heat exchange system involving measured parameters
- B01J2208/00088—Flow rate measurement
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
- B01J2208/00008—Controlling the process
- B01J2208/00017—Controlling the temperature
- B01J2208/00026—Controlling or regulating the heat exchange system
- B01J2208/00035—Controlling or regulating the heat exchange system involving measured parameters
- B01J2208/00097—Mathematical modelling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
- B01J2208/00008—Controlling the process
- B01J2208/00017—Controlling the temperature
- B01J2208/00106—Controlling the temperature by indirect heat exchange
- B01J2208/00168—Controlling the temperature by indirect heat exchange with heat exchange elements outside the bed of solid particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
- B01J2208/00008—Controlling the process
- B01J2208/00017—Controlling the temperature
- B01J2208/00106—Controlling the temperature by indirect heat exchange
- B01J2208/00309—Controlling the temperature by indirect heat exchange with two or more reactions in heat exchange with each other, such as an endothermic reaction in heat exchange with an exothermic reaction
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
Methods are disclosed for constructing packed-bed and monolith reactors/converters, which are more resilient against process disturbances than their conventional counterparts. These stabilized reactors have a reduced tendency to develop, in response to accidental or planned changes of operating parameters, transient hot spots which otherwise can compromise safe and economical reaction operation. The invention involves creating conditions under which transient heat waves that originate from the process disturbances propagate in different radial zones of the reactor with different speeds. As a result, they accumulate phase-shifts relative to each other and interfere destructively through intra-reactor radial heat flows. This constitutes the adaptive mechanism of suppression of the noxious high-temperature waves in exothermal reactors and effects their enhanced operational stability. The area of applicability of stabilized reactors includes chemical and petro-chemical industries as well as automotive (car catalytic converter), environmental (VOC
incinerator) and power/heat generation (catalytic combustor) applications.
Advantages of the SR are enhanced safety and life span of catalyst and other reactor components, and in production applications - improved throughput, selectivity and product quality.
incinerator) and power/heat generation (catalytic combustor) applications.
Advantages of the SR are enhanced safety and life span of catalyst and other reactor components, and in production applications - improved throughput, selectivity and product quality.
Description
The present invention relates to methods of constructing packed-bed and monolith reactorslconverters with improved stability against process disturbances and of controlling transient reactor behavior.
BACKGROUND OF THE INVENTION
Many commercial catalytic reactions are exothermic, hence they are inherently prone to self-acceleration and thermal runaway. Furthermore, the catalyst bed absorbs a fraction of reaction heat and thereby slows down the transport of heat relative to that of matter. This unbalanced transport of heat and matter, in combination with positive temperature feedback gives rise to reactor dynamic instability. As a result, in response to accidental changes of operating parameters (feed temperature, composition, and flow rate, etc.) or during planned transient operations (start-up, shut-down, load change) these reactors tend to develop transient waves of temperature and chemical composition (Onken H.U. and Wicke E., 1986, Statistical Fluctuations of Temperature and Conversion at the Catalytic CO Oxidation in an Adiabatic Packed Bed Reactor, Ber. Bunsen. Ges. Phys. Chem., 90, 976; and Chen Y. C. and Luss D., 1989, Wrong-Way Behavior of Packed Bed Reactor: Influence of Interphase Transport, AIChE J., 35,1148). The peak temperatures of these waves can substantially exceed the maximum temperature of steady-state reactor operation. Such transient traveling hot spots (THSs) represent hazards to the safe and efficient reactor operation: they can limit throughput, selectivity and product quality, and shorten the life of catalyst and of other reactor components.
Packed-bed reactors, especially those with big adiabatic beds, can be sensitive even to small procEas disturbances, operating under certain conditions as resonant amplifiers of incoming perturbations. On the other hand, very large variations of operating pararneters are inherent in the operation of monolith converters and combustors in automotive and power generation industries.
.:::::....:.:::::....:...::::...:.:...:....:::::::::....:: :::.:.:_:. ~ ~..r.
".r a ~ -.
:.::: ~:::'::::::::~s::a:::::.:::.::::;:::~f:::~:: Q . .
t~ .. _;~., ,.:;,.,....,.,...,,~;,CA 02333549 2000 11 27 :...
1~~1~ : w _ _ '...':
Despite the better dynamic (transient) stability of monolith reactors, relative to packed beds, car catalytic converters develop sharp, highly localized temperature spikes, triggered by severe variations of inlet conditions during acceleration-deceleration cycles, {Kirchner T. and Eigenberger G., 1997, On the Dynamic Behavior of Automotive Catalysts, Catalysis Today, 38, 3) and other transient maneuvers (Oh Se H. and Cavendish J.C., 1982, Transients of Monolithic Catalytic Converters: Response to Step Changes in Feedstream Temperature as Related to Controlling Automobile Emissions, Ind. Eng.
Chem. Prod. Res. Dev., 21, 29). Another air pollution control device that can be viewed as a monolithic exothermal reactor is the diesel-particulate trap. Its most popular type, namely the wall-flow filter, represents a ceramic monolith with axial channels open at one end <~nd closed at another. The open and closed channels alternate in a checkerboard manner, hence, exhaust gas is forced through the porous channel walls before it can escape from the trap. This constitutes a filtration process. When the soot load reaches a certain level, the trap must be cleaned up (regenerated}, generally by combustion (thermal or catalyticaily assisted) of soot inside the filter.
Common problems with the monolith reactors and diesel-particulate traps arise from their overheating and from the sharp temperature gradients and thermal stresses that develop during transient operation. Thermal ageing of the automobile catalytic converters results mainly from high-temperature sintering of catalyst and support and from deactivating catalyst-carrier interactions (Heck R.M. and Farrauto R.J., 1995, Catalytic Air Pollution Control: Commercial Technology, Van Norstrand Reinhold, New York). In the diesel-particulate traps, during the regeneration process that has the character of a self-propagating combustion wave, the heat released sometimes causes the monolith to crack or to melt {Neeft J.P.A., Makee M., Moulijn J.A., 1996, Diesel Particulate Emission Control, Fuel Processing Technology 47, 1 ). Serious overheating problems also occur in emerging catalytic technologies, e.g.
BACKGROUND OF THE INVENTION
Many commercial catalytic reactions are exothermic, hence they are inherently prone to self-acceleration and thermal runaway. Furthermore, the catalyst bed absorbs a fraction of reaction heat and thereby slows down the transport of heat relative to that of matter. This unbalanced transport of heat and matter, in combination with positive temperature feedback gives rise to reactor dynamic instability. As a result, in response to accidental changes of operating parameters (feed temperature, composition, and flow rate, etc.) or during planned transient operations (start-up, shut-down, load change) these reactors tend to develop transient waves of temperature and chemical composition (Onken H.U. and Wicke E., 1986, Statistical Fluctuations of Temperature and Conversion at the Catalytic CO Oxidation in an Adiabatic Packed Bed Reactor, Ber. Bunsen. Ges. Phys. Chem., 90, 976; and Chen Y. C. and Luss D., 1989, Wrong-Way Behavior of Packed Bed Reactor: Influence of Interphase Transport, AIChE J., 35,1148). The peak temperatures of these waves can substantially exceed the maximum temperature of steady-state reactor operation. Such transient traveling hot spots (THSs) represent hazards to the safe and efficient reactor operation: they can limit throughput, selectivity and product quality, and shorten the life of catalyst and of other reactor components.
Packed-bed reactors, especially those with big adiabatic beds, can be sensitive even to small procEas disturbances, operating under certain conditions as resonant amplifiers of incoming perturbations. On the other hand, very large variations of operating pararneters are inherent in the operation of monolith converters and combustors in automotive and power generation industries.
.:::::....:.:::::....:...::::...:.:...:....:::::::::....:: :::.:.:_:. ~ ~..r.
".r a ~ -.
:.::: ~:::'::::::::~s::a:::::.:::.::::;:::~f:::~:: Q . .
t~ .. _;~., ,.:;,.,....,.,...,,~;,CA 02333549 2000 11 27 :...
1~~1~ : w _ _ '...':
Despite the better dynamic (transient) stability of monolith reactors, relative to packed beds, car catalytic converters develop sharp, highly localized temperature spikes, triggered by severe variations of inlet conditions during acceleration-deceleration cycles, {Kirchner T. and Eigenberger G., 1997, On the Dynamic Behavior of Automotive Catalysts, Catalysis Today, 38, 3) and other transient maneuvers (Oh Se H. and Cavendish J.C., 1982, Transients of Monolithic Catalytic Converters: Response to Step Changes in Feedstream Temperature as Related to Controlling Automobile Emissions, Ind. Eng.
Chem. Prod. Res. Dev., 21, 29). Another air pollution control device that can be viewed as a monolithic exothermal reactor is the diesel-particulate trap. Its most popular type, namely the wall-flow filter, represents a ceramic monolith with axial channels open at one end <~nd closed at another. The open and closed channels alternate in a checkerboard manner, hence, exhaust gas is forced through the porous channel walls before it can escape from the trap. This constitutes a filtration process. When the soot load reaches a certain level, the trap must be cleaned up (regenerated}, generally by combustion (thermal or catalyticaily assisted) of soot inside the filter.
Common problems with the monolith reactors and diesel-particulate traps arise from their overheating and from the sharp temperature gradients and thermal stresses that develop during transient operation. Thermal ageing of the automobile catalytic converters results mainly from high-temperature sintering of catalyst and support and from deactivating catalyst-carrier interactions (Heck R.M. and Farrauto R.J., 1995, Catalytic Air Pollution Control: Commercial Technology, Van Norstrand Reinhold, New York). In the diesel-particulate traps, during the regeneration process that has the character of a self-propagating combustion wave, the heat released sometimes causes the monolith to crack or to melt {Neeft J.P.A., Makee M., Moulijn J.A., 1996, Diesel Particulate Emission Control, Fuel Processing Technology 47, 1 ). Serious overheating problems also occur in emerging catalytic technologies, e.g.
catalytic NOX reduction in lean environments and catalyticaily supported thermal combustion (Heck R.M. and Farrauto R.J., 1995, Catalytic Air Pollution Control: Commercial Technology, Van Norstrand Reinhold, New York). In the catalytic combustion of fuels for power generation on monolith combustors, one ;i encounters demanding thermal regimes, unmatched in any other catalytic technology. During planned transient operation (start-up, shut-down, load-change) or as a result of accidental process disturbances, the catalyst and substrate may experience temperatures as high as 1300-1400°C, sometimes with catastrophic consequences (Heck R.M. and Farrauto R.J., 1995, Catalytic Air Pollution Control: Commercial Technology, Van Norstrand Reinhold, New York; and Kolaczkowski S. T., 1996, Catalytic Stationary Gas Turbine Combustors: A Review of the Challenges Faced to Clear the Next Set of Hurdles, Trans. I. Chem. E. 73a, 168).
There are currently several methods of preventing noxious temperature 1;5 waves, traveling hot spots, iin commercial catalytic reactors. These include thorough control of operating parameters (inlet temperature, flow rate, composition of feed). This is the standard approach in chemical plants where stable operation is achieved by feedback control systems. In power generation, however, and (especially) in automotive exhaust clean-up, the very nature of the applications involves large variations of inlet conditions. This severe external forcing produces a nonlinear, saturated response, and sometimes leads to dramatic noxious temperature wave overshoots that are damaging to catalyst and substrate (Kirchner T. and Eigenberger G., 1997, On the Dynamic Behavior of Automotive Catalysts, Catalysis Today, 38, 3; and Oh Se H. and 2.5 Cavendish J.C., 1982, Transients of Monolithic Catalytic Converters:
Response to Step Changes in Feedstream Temperature as Related to Controlling Automobile Emissions, Ind. Eng. Chem. Prod. Res. Dev.,21,29).
Another method of preventing noxious traveling hot spots in commercial catalytic reactors is conservative operation under mild operating conditions (dilute feeds and catalysts, low space velocities). However, the price paid for this safety is a reduced throughput.
Appropriate reactor design and choice of parameters is another approach taken to alleviate the problem of traveling hot spots. An important paradigm of this approach, that is not widely recognized, is utilization of the catalyst-pellet size as a parameter governing reactor stability (Matros Yu. Sh., 1985, Unsteady Processes in Catalytic Reactors, Elsevier Science, Amsterdam}. The use of large pellets (up to l0mm in diameter) entails a decreased observed activation energy of the reaction and an increased fluid-solid heat flow resistance. The former diminishes the tendency of the reaction to self-accelerate, improving thereby both dynamic and static reactor stability. The latter exerts on the reactor an influence similar to that of heat dispersion which tends to even out temperature inhomogeneities, suppressing the tendency of the reactor to form noxious temperature waves. In monolith reactors, the thermal properties of the monolith material, the channel size and wall thickness have a profound influence on temperature wave formation.
There is a need for packed-bed reactors, monolith reactors and diesel-particulate traps with enhanced operational stability, less prone to overheating and thermal deterioration during transient operation. Such reactors could be operated at higher levels of throughput without compromising their operational safety and quality of the process (e.g. selectivity and product quality in production applications}. A further advantage that derives from improved reactor stability is a greater durability of the equipment including longer life of catalyst and other reactor components.
t'.5 SUMMARY OF THE INVENTION
The present invention provides a method of adaptive control of temperature fluctuations arising from transient heat waves in exothermal catalytic reactors, comprising:
There are currently several methods of preventing noxious temperature 1;5 waves, traveling hot spots, iin commercial catalytic reactors. These include thorough control of operating parameters (inlet temperature, flow rate, composition of feed). This is the standard approach in chemical plants where stable operation is achieved by feedback control systems. In power generation, however, and (especially) in automotive exhaust clean-up, the very nature of the applications involves large variations of inlet conditions. This severe external forcing produces a nonlinear, saturated response, and sometimes leads to dramatic noxious temperature wave overshoots that are damaging to catalyst and substrate (Kirchner T. and Eigenberger G., 1997, On the Dynamic Behavior of Automotive Catalysts, Catalysis Today, 38, 3; and Oh Se H. and 2.5 Cavendish J.C., 1982, Transients of Monolithic Catalytic Converters:
Response to Step Changes in Feedstream Temperature as Related to Controlling Automobile Emissions, Ind. Eng. Chem. Prod. Res. Dev.,21,29).
Another method of preventing noxious traveling hot spots in commercial catalytic reactors is conservative operation under mild operating conditions (dilute feeds and catalysts, low space velocities). However, the price paid for this safety is a reduced throughput.
Appropriate reactor design and choice of parameters is another approach taken to alleviate the problem of traveling hot spots. An important paradigm of this approach, that is not widely recognized, is utilization of the catalyst-pellet size as a parameter governing reactor stability (Matros Yu. Sh., 1985, Unsteady Processes in Catalytic Reactors, Elsevier Science, Amsterdam}. The use of large pellets (up to l0mm in diameter) entails a decreased observed activation energy of the reaction and an increased fluid-solid heat flow resistance. The former diminishes the tendency of the reaction to self-accelerate, improving thereby both dynamic and static reactor stability. The latter exerts on the reactor an influence similar to that of heat dispersion which tends to even out temperature inhomogeneities, suppressing the tendency of the reactor to form noxious temperature waves. In monolith reactors, the thermal properties of the monolith material, the channel size and wall thickness have a profound influence on temperature wave formation.
There is a need for packed-bed reactors, monolith reactors and diesel-particulate traps with enhanced operational stability, less prone to overheating and thermal deterioration during transient operation. Such reactors could be operated at higher levels of throughput without compromising their operational safety and quality of the process (e.g. selectivity and product quality in production applications}. A further advantage that derives from improved reactor stability is a greater durability of the equipment including longer life of catalyst and other reactor components.
t'.5 SUMMARY OF THE INVENTION
The present invention provides a method of adaptive control of temperature fluctuations arising from transient heat waves in exothermal catalytic reactors, comprising:
_. ._ .___ __ __ ._-_ _ -_. _... .a. - ~. _ ~ rmV~_W Jv~o~ r!t:~ YW
%:K:.i~i~.u.ns:v:r , 2t~-~o-2~7~V C~, OO~~O~SGJ
providing at least twc~ component exotherrnal catalytic reactors, each of said at least two component exotherma! catalytic reactors including means far inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into differanl, phase-shifted t~mperature ruaves; and thermally coupling said at least two component exothermal catalytic reactors so that heat exchange occurs between said at least two component exothertnal catalytic reactors in the radial direction, wherein said phase-shifted temperature waves in each of said at least t~wa component exothem~al catalytic reactors destructively interfere through radial inter-reactor heat fiiuw then.by dampening said temperature fluctuations and reducing deviations of reactor temperature fields from desirable steady state temperature profiles.
In another aspect of the invention there is provided an exotherrnal catalytic reactor with adaptive control of temperature fluctuations, comprising:
't5 at least two component exothermal catalytic reactors each having a longitudinal direction, said at least two component exothermal catalytic reactors being thermally coupled so that heat exchange occurs between said at least two component exothermal catalytic reactors in the radial direction;
each of said at least two component exothermal catalytic reactors including means for inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into different, phase-shifted temperature waves, wherein said phase-shifted temperature waves in each of said at least two component exothermdt catalytic reactors destructively interfere through radial inter reactor heat flow thereby dampening said temperature fluctuations and reducing deviations of reactor temperature fields from desirable steady state temperature profiles.
In an embodiment of the reactor using passive inserts to obtain stabilization, if the reactor and passive insert are not thermally coupled there will b2 wave in the reactor and na wave in the passive insert. lNhen the reactor and the insert are thermally coupled, the wave in the reactor induces secondary wave in the insert and drags this secondary wave downstream. The secondary wave lags behind being thus phase-shifted (phase-delayed relative to the primary wave in the reactor. The very same radial heat flow that gives rise to the secondary wave makes the primary and the secondary waves destructively interfere.
BRIEF DESCRIPTION OF THE DRAWINGS
The method of enhancing stability and performance of catalytic exothermal reactors in accordance with the present invention will now be described, by way of example only, reference being had to the accompanying drawings, in which;
Figure1 a is a schematic diagram of various types of a prior art catalytic reactors such as basic packed-bed reactor (PBR), or monolith reactor (MR);
Figure1 b is a schematic diagram of various types of co-current PBR or MR of the present invention, composed of two dynamically different component reactors;
Figure 1c is a schematic representation of a prior art counter-current tandem PBR or MR, composed of two identical component reactors;
Figure 1d is a schematic representation of a bent reactor with internal counter-current heat exchange;
Figure 1 a is a schematic representation of a tandem reactor of the present invention with catalyst removed from non-functional downstream parts of component reactors;
Figure 1 f is a schematic representation of a prior art bent reactor with one sleeve emptied of catalyst, since only one sleeve can be used to carry the reaction;
Figure 2a is a cross-sectional view of a stabilized reactor with a shell and tube configuration constructed in accordance with the present invention;
Figure 2b is a cross sectional view of a stabilized packed-bed reactor of the present invention constructed with a checkerboard configuration;
Figure 2c is a cross sectional view of a checkerboard configuration for a monolith reactor constructed in accordance with the present invention;
Figure 3a is a cross sectional view of a stabilized packed-bed reactor constructed in accordance with the present invention using a passive-insert stabilization scheme with the passive-inserts being rods (depicted by black circles);
Figure 3b is a cross sectional view of a stabilized packed-bed reactor constructed in accordance 'with the present invention using a passive-insert stabilization scheme with the passive-inserts being internal walls, running along the reactor axis;
Figure 3c is a cross sectional view of a stabilized monolith reactor constructed in accordance with the present invention using a passive-insert stabilization scheme with the passive-inserts being in the form of massive internal walls;
Figures 4a and 4b show plots of temperature response of two packed-bed reactors with different Lewis numbers to slight periodic variations of the temperature of feed for the two packed-bed reactors operating independently;
Figures 4c and 4d show plots of temperature response of two packed-bed reactors with different Lewis numbers to slight periodic variations of the temperature of feed for the two packed-bed reactors being co-currently thermally coupled as shown in Figure 1 b;
Figure 5a shows a reference response of an isolated packed-bed reactor of Figure 1a. A snapshot of transient temperature distribution is shown (wavy curve) as welt as temperature envelopes and uncertainty.
Figure 5b shows similar data to Figure 5a but for the case when the reactor operates as a component of the counter-current arrangement of Figure1 c;
Figure 6a shows a reference temperature response of a basic packed-bed reactor of Figure 1a to a small-amplitude periodic perturbation of the temperature of feed (dotted curve) and response of a reactor stabilized by passive inserts in the form of internal walls of Figure 3b (solid curve);
Figure 6b shows the temperature response of stabilized catalyst bed (solid line) of Figure 3b and of a passive insert, an internal wall, used to stabilize the bed (broken line);
;i Figure 6c is a plot showing temperature envelopes for the basic packed-bed reactor (dotted-line being the reference response) and for the passive-insert stabilized packed-bed reactor (solid line);
Figure 7a illustrates the improved dynamic stability of a checkerboard monolith reactor of Figure 2c (solid lines) relative to the basic monolithic reactor 1() of Figure 1a (broken lines); and Figure 7b demonstrates stabilization of monolith reactor operation using passive inserts stabilization scheme of Figure 3c under typical conditions of the MR production applications.
1 Ei DETAILED DESCRIPTION OF THE INVENTION
Prior art catalytic reactors of the type schematically illustrated in Figure1a are widely used in chemical and petrochemical industries as well as in automotive (car catalytic converter) and environmental (VOC incinerator) applications. A new, emerging technology, namely catalytic combustion for 2U power generation in gas turbines, involves catalytic monolith combustor as its core unit. Catalytic reactors comprise a porous soiid support and, bound to it, a catalytically active component which promotes the reaction of interest. In packed-bed reactors (PBRs) the support is granular, and in monolith reactors (MRs) it represents a rigid ceramic or metallic structure with a multitude of 2;i regular, axial channels.
The present invention discloses methods of rendering exothermal reactors, such as but not limited to packed-bed reactors, monolith reactors and diesel-particulate traps, inherently more stable, compared to their conventional counterparts, in the sense that their tendency to develop transient waves of temperature and chemical composition is considerably diminished. The invention exploits the stabilizing effect of lateral heat exchange between different radial sections of the reactor in which the heat waves are made to develop phase shifts relative to each other. These phase-shifted waves attenuate each other through radial heat flows, which process can be likened to destructive interference.
Another source of enhanced reactor stability is the increased thermal conductance of the bed which is operative when passive inserts are employed as a means of reactor stabilization. Both contributing factors, destructive interference of heat waves and enhanced heat conductance of the bed, promote 1~~ more uniform distribution of heat carried by temperature waves over reactor volume diminishing both the maximal transient temperatures and the temperature gradients. The area of applicability of thus stabilized reactors (SRs) includes chemical and petro-chemical industries as well as automotive (car catalytic converter), environmental (VOC incinerator) and power/heat generation 1.5 (catalytic combustor) applications.
The present invention achieves the objective of controlling transient behavior of exothermal reactors by employing reactor designs that have an improved dynamic stability built into their structure. This signifies enhanced resilience of the stabilized reactors against process disturbances and smoother 2'D operation during planned transient maneuvers, compared to their conventional counterparts. Reduced deviations of intra-reactor temperature fields from their intended stationary profiles are achieved through a more uniform distribution of heat carried by transient temperature waves over the reactor volume. The invention provides reactor designs that exploit destructive interference of 25 transient heat waves and enhanced thermal conductance of the bed. This is achieved through the following two approaches.
The first approach, the coupled-reactor (CR) scheme, involves thermally coupled operation of two or more component reactors. When operated in the co-current mode as shown in Figure1 b, the component reactors must be dynamically different in the sense that identical process disturbances evolve in them into different, phase-shifted transient waves. This is accomplished through different thermal properties of the catalyst carriers (e.g. different heat capacities) in these reactors or different space velocities. Transient waves in reactor with faster flow or with lower heat capacity propagate at increased speeds. Due to this difference in propagation speeds, transient waves in component reactors accumulate a phase-shift and interfere destructively through radial inter-reactor heat flows. In the counter-current mode, shown in Figure1c, identical component reactors may be used since the transient waves propagate in opposite directions.
Figures 2a, 2b and 2c; show different embodiments of operationally stabilized reactors that implement the coupled-reactor stabilization scheme.
Figure 2a shows a stabilized reactor 20 including a shell 22 and tubes 24 on the interior of the shell to form a shell and tube configuration. In co-current stabilized 1 ~~ reactors using this, 20, configuration, both the shell 22 and the tubes 24 are filled with catalyst. The shell and tube sides are operationally (dynamically) different e.g. through different heat capacities of catalyst carriers in them as described above. Catalytic component may be the same with different catalyst carriers. In counter-current stabilized reactors 20, certain domains of the reactor's inner space must be void of catalyst as shown in Figure 1 a because of the parametric sensitivity considerations discussed below (see EXAMPLE 2).
Figure 2b shows a packed-bed reactor 30 having a checkerboard configuration including for the co-current stabilized reactor, internal walls 32 that sub-divide the inner volume of the reactor into prismatic sections 34 filled with catalyst such 2C~ that adjacent cells are dynamically different e.g. through different heat capacities of catalyst carriers 36 and 38. Complete leak-tight separation of cells is not necessary, so that a frame composed of internal partitions (e.g. metal sheets) may be placed inside the shell loosely and then filled with catalyst in a checkerboard manner. This scheme is not convenient for the counter-current stabilized reactors where complete separation of fluids flowing to meet each other must be provided in order to sustain pressure gradients of opposite signs driving these flows. Figure 2c shows a cross section of a monolith reactor 40 having a checkerboard configuration to be used in chemical manufacturing processes, car exhaust.clean-up, VOC incineration, catalytic combustion for power and heat generation, diesel particulate matter retention and incineration.
The reactor is composed of alternating domains 42 and 44 with different thermal (e.g. heat capacity), operational (e.g space velocity), geometrical (e.g, channel wall thickness) or other properties.
The second stabilization method, referred to as the passive-insert (PI) method, employs embedding into the packed bed or monolith of extra heat capacitylconductance in the form of axial internal walls, rods, plates, etc.
The role of these passive-inserts is to absorb a fraction of the excess reaction heat released during an upward temperature excursion and to release it later on, 1 ~~ ideally during a downward deviation of the bed temperature. The passive-inserts also act as thermal shunts that reinforce the effective heat conductance of the bed and convey heat from the transient traveling hot spots to adjacent cooler areas.
Figures 3a, 3b and 3c; show different embodiments of stabilized reactors based on the passive-insert stabilization scheme. Figure 3a illustrates a cross section of a packed-bed reactor 60 with the passive-inserts 62 in the form of axial rods (depicted by black circles) surrounded by catalyst particles 64.
Figure 3b illustrates a packed-bed reactor 70 including internal walls 72 running along the reactor axis among the catalyst particles 74. Figure 3c shows a cross section 2~~ of a monolith reactor 80 with the passive inserts in the form of selected reinforced channel walls 82 as compared to thinner regular channel walls 84.
In the embodiment of the method using coupled-reactor stabilization, phase-shifted temperature waves develop due to the dynamical difference of companent reactors. Even if there is no heat exchange between the reactors, transient waves exist in the reactors whether or not they are thermally coupled and will in general be phase-shifted with respect to each other.
Radial heat flows between the thermally coupled reactors results in these pre-existing phase-shifted waves destructively interfering.
:5 In the embodiment of the method using passive inserts, if reactor and passive insert are not thermally coupled there will be wave in the reactor and no wave in the passive insert. lNhen the reactor and the insert are thermally coupled, the wave in the reactor induces secondary wave in the insert and drags this secondary wave downstream. The secondary wave lags behind being thus 1 () phase-shifted (phase-delayed) relative to the primary wave in the reactar. The very same radial heat flow that gives rise to the secondary wave makes the primary and the secondary waves destructively interfere.
The stabilized reactors that implement coupled-reactor- or passive-insert stabilization schemes rely on efficient heat exchange among the reactor's 1;i adjacent radial zones. This its necessary for destructive interference of the heat waves to occur or for the passive inserts to contribute their capacity to conduct heat effectively. The pitch, D, of the radial structure of a stabilized reactors, namely the distance between the neighbouring Pls or between component reactors, is determined by the distance of lateral drift of the heat within the 2() reactor's thermal response lame. For the packed-bed reactors, D
approximately equals (due"e,L)'~2, where dpe,~e, is the catalyst pellet size and L is the reactor length. Here L is representative of the reagent residence time inside the reactor (hence of the reactor thermal response time) and dPe"et represents the mean free path of the lateral turbulent heat dispersion inside the packed bed. E.g. for 2;i d~"e~ 5mm and L=2m, D=1C)cm.
Because of their greater stability, the stabilized reactors disclosed herein can be operated more aggressively than their conventional counterparts to attain higher levels of productivity. Alternatively, they can be operated more safely to extend the life-span of the catalyst and to improve the quality of the process, e.g.
selectivity in production applications, that is generally a sensitive function of temperature.
The radial heat exchange among the component reactors may be configured to occur through an additional (e.g. cooling) medium. As well, the reactors may be configured so that destructive interference of transient waves in the component reactors occurs through delayed interaction of similar or dissimilar component reactoirs through an additional (e.g. cooling) medium.
A reactor may also be: constructed in accordance with the present invention wherein the maximum temperature of the stationary hot spot and reactor parametric sensitivity are reduced through the interaction via cooling medium among the component reactors, in which stationary hot spots are positioned at different locations along the reactor axis. The difference in locations of the stationary hot spots in component reactors is achieved for example through the difference of flow velocities of reagents in said component reactors.
The following nonlimiting examples will further exemplify the method of stabilizing reactors and constructing stabilized reactors for various applications.
The coupled-reactor stabilization scheme is illustrated in Figure1 b for the co-current stabilized reactor and involves thermally coupled operation of two component reactors. The latter are designed to be dynamically different in the sense that identical perturbations evolve in them differently, e.g. propagate at different speeds. The goal is to force the same process disturbances to develop in the component reactors into heat waves that are phase-shifted relative to each other. With the reactor sizing and thermal properties appropriately chosen, radial heat exchange between the component reactors tends to suppress the temperature waves in them through the mechanism similar to destructive interference. This constitutes the adaptive mechanism of enhanced dynamic stability built into the stabilised reactor structure. As an example one may use two adiabatic packed-bed reactors with an exothermic reaction A=>B+heat, first operating independently and subsequently in a co-current arrangement.
The propagation speed of the heat waves in a packed-bed reactor is inversely proportional to its Lewis number Le = j(1-E)p,Cs + ep,C, ] /Ep,Cf (e is the void fraction of the bed; ~~5, p~ and CS, C, are the solid/fluid densities and heat capacities). The reference response of two packed-bed reactors with different Lewis numbers to a periodic perturbation is shown in Figures 4a and 4b in which the reactors operate independently. The curves 1 show the snapshots of transient temperature distributions inside the reactors: the waves that have evolved from identical perturbation are phase-shifted relative to each other.
The curves 2 show the upper and the lower temperature envelopes, the curves 3 (dotted) show the steady-state temperature profiles, and the curves 4 show the difference of the upper and lower temperature envelopes (temperature uncertainties). The perturbation is applied to the feedstream temperature, Ta, and it has amplitude 0.01 To. Transients which originate from these slight variations of the inlet temperature grow into the large-amplitude travelling waves of heat and chemical composition. The difference of upper and lower temperature envelopes which confine these waves (the temperature uncertainty) serves as a measure of reactor operational instability. Because of the difference in the Lewis numbers of the component reactors, transient waves propagate in them at different speeds and a phase-shift builds up between them.
The response of the above reactors to the same perturbation after they have been co-currently thermally coupled (Figure1 b) is shown in Figures 4c and 4d. While the steady-state temperature profiles are unaffected, the transient response is drastically reduced by the coupling. The improved stability of coupled configuration is evident: the temperature excursions are now confined to the immediate vicinity of the steady states and the temperature uncertainties are reduced both in amplitude and in width.
Another realization of the coupled-reactor approach is the counter-current stabilized reactor shown in Figure1c. Dynamic dissimilarity of component ;i reactors necessary to produce a phase-shift between the heat waves in them is inherent in this configuration since these waves propagate in opposite directions. This gives the reactor, composed of identical counter-currently coupled component reactors, a high degree of stability, as illustrated by Figure 5b (to be compared with the reference response of an isolated packed-bed reactor shown in Figure 5a). A snapshot of transient temperature distribution is shown (wavy curve) as well as temperature envelopes and uncertainty.
Packed-bed reactors with integrated counter-current heat exchange are employed in industry to achieve autothermal operation when hot reaction products preheat cold feed so that no external heat supply is necessary (Aris R., 1989, Elementary Chemical Reactor Analysis, Butterworth, Boston; Froment G. F. and Bischoff K. B., 1990, Chemical Reactor Analysis and Design, John Wiley, New York; Eigenberger G. and Nieken U., 1994, Catalytic Cleaning of Polluted Air: Reaction Engineering Problems and New Solutions, Int.Chem.Eng., 34, 4) . A famous example of this reactor type is the TVA
reactor for ammonia synthesis {see e.g. Aris R., 1989, Elementary Chemical Reactor Analysis, Butterworth, Boston). The elementary (conceptual) unit of the counter-current autothermal reactors is a reactor obtained by coupling of two basic PBRs of Figure 1 a in a counter-current arrangement of Figure 1 c (see e.g. Sun Q., Young B., Williams D.F., Glasser D. and Hildebrandt D., 1995, A Periodic Flow 2;i Reversal Reactor: an Infinitely Fast Switching Model and a Practical Proposal for its Implementation, Abstr. of the USPC-2 Conference, St. Louis, Missouri, USA.) or from a single basic packed-bed reactors by bending it at the mid-point and bringing the resultant branches into thermal contact as shown in Figure 1d. These reactor models, however, become parametrically sensitive and extinguish abruptly when the reaction zone approaches the mid-point of the tandem counter-current reactor or the knee of the bent reactor. Hence, the inlet branch [Aris R., 1989, Elementary Chemical Reactor Analysis, Butterworth, Boston] or the outlet branch (Eigenberger G. and Nieken U., 1994, Catalytic Cleaning of Polluted Air: Reaction Engineering Problems and New Solutions, Int.Chem.Eng., :14, 4) of the bent reactor or the up-(downstream halves of the component reactors in the counter-current arrangement must be emptied of catalyst. These reactor domains cannot be used because of the 1 C~ above limitation imposed on the reaction zone location. Moreover, if packed, they would produce extra hydraulic resistance of the bed. Two examples of this family of reactors are shown. schematically Figures1e and 1f. If operating conditions of two component reactors of the tandem configuration are identical, this reactor is operationally equivalent to the bent reactor with the 15 correspondence rules: c -> d, a -> f .
Stability of autothermal reactors is usually considered within the framework of parametric sensitivity approach that is based on reactor response to (infinitely) slow perturbations (Morbidelli M. and Varma A., 1982, Parametric Sensitivity and Runaway in Tubular Reactors, AIChE J., 25, 903). Dynamic 20~ aspect of the counter-current reactors stability is twofold. First, due to destructive interference of heat waves in component reactors, resonant disturbance amplification, characteristic of basic packed-bed reactors, is virtually eliminated. Secondly, thermal response time of this reactor is longer than that of single packed-bed reactor since exiting transients are reintroduced into the inlet 25 zone of adjacent component reactor. Prolonged thermal response time makes the reactor insensitive to shorter-time disturbances. This means enhanced operational stability.
The stabilizing effect of passive inserts (Pls) partially arises from destructive interference of heat waves in them and in catalyst bed. Enhanced thermal conductivity of the bed is another contributing factor. The passive insert stabilization scheme involves a single packed- or monolithic catalyst bed with passive inserts embedded in it parallel to the reactor axis. An important function of these passive inserts is to absorb a fraction of the excess reaction heat released during an upward temperature excursion and to release it later on, ideally during a downward deviation of the bed temperature. This dynamics can 1 D also be understood using the notion of secondary heat waves that are induced in passive inserts by the primary waves in catalyst bed. Due to the thermal inertia of the inserts and to the limited rate of heat exchange between them and the catalyst bed, secondary temperature waves are phase-shifted, delayed, relative to the primary ones. The result of interaction of these phase-shifted waves through radial heat flows is their destructive interference and partial annihilation. Additionally, the passive inserts conduct heat at a high rate, increasing thereby effective thermal conductivity of the bed and bringing further down both: the maximal temperatures and the temperature gradients. For optimal operation, the cumulative heat capacitance and conductance of the 2~D inserts must make up a noticeable fraction of these quantities of catalyst bed.
Figures 6a, 6b and 6c illustrate stabilizing effect of passive inserts on the transient operation of a packed-bed reactor. Figure 6a shows reference temperature response of a basic packed-bed reactor to a small-amplitude periodic perturbation of the temperature of feed (dotted curve} and response of a reactor stabilized by passive inserts (solid curve). Figure 6b shows the temperature response of catalyst bed and of passive inserts which have the form of internal wails, parallel to the reactor axis in which it can be seen that variations of the passive insert temperature are phase-delayed, relative to those of the bed. Figure 6c shows temperature envelopes for the basic packed-bed reactor (reference response) and for the passive insert-stabilized packed-bed reactor in which it can be seen that the degree of stabilization is quite appreciable.
In automotive and power/heat generation applications of monolith reactors, the reactor length is considerably smaller and flow velocity is considerably higher than in packed-bed reactor of chemical industry. The resulting short residence times limit the efficiency of solid/fluid heat and matter exchange and inter-phase concentration and temperature gradients are correspondingly large. Inter-phase heat flow resistance exerts a stabilizing influence on reactor operation, playing a role similar to that of axial heat conduction (Chen Y. C. and Luss D., 1989, Wrong-Way Behavior of Packed Bed Reactor: Influence of Interphase Transport, AIChE J., 35,1148). In production applications however, as exemplified by S02 => S03 oxidation in sulfuric acid manufacture (U.S. Patent No. 5,264,200), monolith reactors operating conditions are close to those of packed beds with residence times on the scale of 1 s. Under these conditions monolith reactors may operate as resonant amplifiers of perturbations, as illustrated in Figure7a. The hot-spot activity then can be controlled through implementation of the CR approach in the form of checkerboard monolith, shown in Figure2c. Figure7a illustrates the improved dynamic stability of a checkerboard monolith reactor relative to the basic monolith reactor. The passive-insert stabilization scheme is also applicable to monolith reactors as illustrated by Figure 7b.
The foregoing description of the preferred embodiments of the invention has been presented to illustrate the principles of the invention and not to limit the invention to the particular embodiment illustrated. It is intended that the scope of the invention be defined by all of the embodiments encompassed within the following claims and their equivalents.
%:K:.i~i~.u.ns:v:r , 2t~-~o-2~7~V C~, OO~~O~SGJ
providing at least twc~ component exotherrnal catalytic reactors, each of said at least two component exotherma! catalytic reactors including means far inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into differanl, phase-shifted t~mperature ruaves; and thermally coupling said at least two component exothermal catalytic reactors so that heat exchange occurs between said at least two component exothertnal catalytic reactors in the radial direction, wherein said phase-shifted temperature waves in each of said at least t~wa component exothem~al catalytic reactors destructively interfere through radial inter-reactor heat fiiuw then.by dampening said temperature fluctuations and reducing deviations of reactor temperature fields from desirable steady state temperature profiles.
In another aspect of the invention there is provided an exotherrnal catalytic reactor with adaptive control of temperature fluctuations, comprising:
't5 at least two component exothermal catalytic reactors each having a longitudinal direction, said at least two component exothermal catalytic reactors being thermally coupled so that heat exchange occurs between said at least two component exothermal catalytic reactors in the radial direction;
each of said at least two component exothermal catalytic reactors including means for inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into different, phase-shifted temperature waves, wherein said phase-shifted temperature waves in each of said at least two component exothermdt catalytic reactors destructively interfere through radial inter reactor heat flow thereby dampening said temperature fluctuations and reducing deviations of reactor temperature fields from desirable steady state temperature profiles.
In an embodiment of the reactor using passive inserts to obtain stabilization, if the reactor and passive insert are not thermally coupled there will b2 wave in the reactor and na wave in the passive insert. lNhen the reactor and the insert are thermally coupled, the wave in the reactor induces secondary wave in the insert and drags this secondary wave downstream. The secondary wave lags behind being thus phase-shifted (phase-delayed relative to the primary wave in the reactor. The very same radial heat flow that gives rise to the secondary wave makes the primary and the secondary waves destructively interfere.
BRIEF DESCRIPTION OF THE DRAWINGS
The method of enhancing stability and performance of catalytic exothermal reactors in accordance with the present invention will now be described, by way of example only, reference being had to the accompanying drawings, in which;
Figure1 a is a schematic diagram of various types of a prior art catalytic reactors such as basic packed-bed reactor (PBR), or monolith reactor (MR);
Figure1 b is a schematic diagram of various types of co-current PBR or MR of the present invention, composed of two dynamically different component reactors;
Figure 1c is a schematic representation of a prior art counter-current tandem PBR or MR, composed of two identical component reactors;
Figure 1d is a schematic representation of a bent reactor with internal counter-current heat exchange;
Figure 1 a is a schematic representation of a tandem reactor of the present invention with catalyst removed from non-functional downstream parts of component reactors;
Figure 1 f is a schematic representation of a prior art bent reactor with one sleeve emptied of catalyst, since only one sleeve can be used to carry the reaction;
Figure 2a is a cross-sectional view of a stabilized reactor with a shell and tube configuration constructed in accordance with the present invention;
Figure 2b is a cross sectional view of a stabilized packed-bed reactor of the present invention constructed with a checkerboard configuration;
Figure 2c is a cross sectional view of a checkerboard configuration for a monolith reactor constructed in accordance with the present invention;
Figure 3a is a cross sectional view of a stabilized packed-bed reactor constructed in accordance with the present invention using a passive-insert stabilization scheme with the passive-inserts being rods (depicted by black circles);
Figure 3b is a cross sectional view of a stabilized packed-bed reactor constructed in accordance 'with the present invention using a passive-insert stabilization scheme with the passive-inserts being internal walls, running along the reactor axis;
Figure 3c is a cross sectional view of a stabilized monolith reactor constructed in accordance with the present invention using a passive-insert stabilization scheme with the passive-inserts being in the form of massive internal walls;
Figures 4a and 4b show plots of temperature response of two packed-bed reactors with different Lewis numbers to slight periodic variations of the temperature of feed for the two packed-bed reactors operating independently;
Figures 4c and 4d show plots of temperature response of two packed-bed reactors with different Lewis numbers to slight periodic variations of the temperature of feed for the two packed-bed reactors being co-currently thermally coupled as shown in Figure 1 b;
Figure 5a shows a reference response of an isolated packed-bed reactor of Figure 1a. A snapshot of transient temperature distribution is shown (wavy curve) as welt as temperature envelopes and uncertainty.
Figure 5b shows similar data to Figure 5a but for the case when the reactor operates as a component of the counter-current arrangement of Figure1 c;
Figure 6a shows a reference temperature response of a basic packed-bed reactor of Figure 1a to a small-amplitude periodic perturbation of the temperature of feed (dotted curve) and response of a reactor stabilized by passive inserts in the form of internal walls of Figure 3b (solid curve);
Figure 6b shows the temperature response of stabilized catalyst bed (solid line) of Figure 3b and of a passive insert, an internal wall, used to stabilize the bed (broken line);
;i Figure 6c is a plot showing temperature envelopes for the basic packed-bed reactor (dotted-line being the reference response) and for the passive-insert stabilized packed-bed reactor (solid line);
Figure 7a illustrates the improved dynamic stability of a checkerboard monolith reactor of Figure 2c (solid lines) relative to the basic monolithic reactor 1() of Figure 1a (broken lines); and Figure 7b demonstrates stabilization of monolith reactor operation using passive inserts stabilization scheme of Figure 3c under typical conditions of the MR production applications.
1 Ei DETAILED DESCRIPTION OF THE INVENTION
Prior art catalytic reactors of the type schematically illustrated in Figure1a are widely used in chemical and petrochemical industries as well as in automotive (car catalytic converter) and environmental (VOC incinerator) applications. A new, emerging technology, namely catalytic combustion for 2U power generation in gas turbines, involves catalytic monolith combustor as its core unit. Catalytic reactors comprise a porous soiid support and, bound to it, a catalytically active component which promotes the reaction of interest. In packed-bed reactors (PBRs) the support is granular, and in monolith reactors (MRs) it represents a rigid ceramic or metallic structure with a multitude of 2;i regular, axial channels.
The present invention discloses methods of rendering exothermal reactors, such as but not limited to packed-bed reactors, monolith reactors and diesel-particulate traps, inherently more stable, compared to their conventional counterparts, in the sense that their tendency to develop transient waves of temperature and chemical composition is considerably diminished. The invention exploits the stabilizing effect of lateral heat exchange between different radial sections of the reactor in which the heat waves are made to develop phase shifts relative to each other. These phase-shifted waves attenuate each other through radial heat flows, which process can be likened to destructive interference.
Another source of enhanced reactor stability is the increased thermal conductance of the bed which is operative when passive inserts are employed as a means of reactor stabilization. Both contributing factors, destructive interference of heat waves and enhanced heat conductance of the bed, promote 1~~ more uniform distribution of heat carried by temperature waves over reactor volume diminishing both the maximal transient temperatures and the temperature gradients. The area of applicability of thus stabilized reactors (SRs) includes chemical and petro-chemical industries as well as automotive (car catalytic converter), environmental (VOC incinerator) and power/heat generation 1.5 (catalytic combustor) applications.
The present invention achieves the objective of controlling transient behavior of exothermal reactors by employing reactor designs that have an improved dynamic stability built into their structure. This signifies enhanced resilience of the stabilized reactors against process disturbances and smoother 2'D operation during planned transient maneuvers, compared to their conventional counterparts. Reduced deviations of intra-reactor temperature fields from their intended stationary profiles are achieved through a more uniform distribution of heat carried by transient temperature waves over the reactor volume. The invention provides reactor designs that exploit destructive interference of 25 transient heat waves and enhanced thermal conductance of the bed. This is achieved through the following two approaches.
The first approach, the coupled-reactor (CR) scheme, involves thermally coupled operation of two or more component reactors. When operated in the co-current mode as shown in Figure1 b, the component reactors must be dynamically different in the sense that identical process disturbances evolve in them into different, phase-shifted transient waves. This is accomplished through different thermal properties of the catalyst carriers (e.g. different heat capacities) in these reactors or different space velocities. Transient waves in reactor with faster flow or with lower heat capacity propagate at increased speeds. Due to this difference in propagation speeds, transient waves in component reactors accumulate a phase-shift and interfere destructively through radial inter-reactor heat flows. In the counter-current mode, shown in Figure1c, identical component reactors may be used since the transient waves propagate in opposite directions.
Figures 2a, 2b and 2c; show different embodiments of operationally stabilized reactors that implement the coupled-reactor stabilization scheme.
Figure 2a shows a stabilized reactor 20 including a shell 22 and tubes 24 on the interior of the shell to form a shell and tube configuration. In co-current stabilized 1 ~~ reactors using this, 20, configuration, both the shell 22 and the tubes 24 are filled with catalyst. The shell and tube sides are operationally (dynamically) different e.g. through different heat capacities of catalyst carriers in them as described above. Catalytic component may be the same with different catalyst carriers. In counter-current stabilized reactors 20, certain domains of the reactor's inner space must be void of catalyst as shown in Figure 1 a because of the parametric sensitivity considerations discussed below (see EXAMPLE 2).
Figure 2b shows a packed-bed reactor 30 having a checkerboard configuration including for the co-current stabilized reactor, internal walls 32 that sub-divide the inner volume of the reactor into prismatic sections 34 filled with catalyst such 2C~ that adjacent cells are dynamically different e.g. through different heat capacities of catalyst carriers 36 and 38. Complete leak-tight separation of cells is not necessary, so that a frame composed of internal partitions (e.g. metal sheets) may be placed inside the shell loosely and then filled with catalyst in a checkerboard manner. This scheme is not convenient for the counter-current stabilized reactors where complete separation of fluids flowing to meet each other must be provided in order to sustain pressure gradients of opposite signs driving these flows. Figure 2c shows a cross section of a monolith reactor 40 having a checkerboard configuration to be used in chemical manufacturing processes, car exhaust.clean-up, VOC incineration, catalytic combustion for power and heat generation, diesel particulate matter retention and incineration.
The reactor is composed of alternating domains 42 and 44 with different thermal (e.g. heat capacity), operational (e.g space velocity), geometrical (e.g, channel wall thickness) or other properties.
The second stabilization method, referred to as the passive-insert (PI) method, employs embedding into the packed bed or monolith of extra heat capacitylconductance in the form of axial internal walls, rods, plates, etc.
The role of these passive-inserts is to absorb a fraction of the excess reaction heat released during an upward temperature excursion and to release it later on, 1 ~~ ideally during a downward deviation of the bed temperature. The passive-inserts also act as thermal shunts that reinforce the effective heat conductance of the bed and convey heat from the transient traveling hot spots to adjacent cooler areas.
Figures 3a, 3b and 3c; show different embodiments of stabilized reactors based on the passive-insert stabilization scheme. Figure 3a illustrates a cross section of a packed-bed reactor 60 with the passive-inserts 62 in the form of axial rods (depicted by black circles) surrounded by catalyst particles 64.
Figure 3b illustrates a packed-bed reactor 70 including internal walls 72 running along the reactor axis among the catalyst particles 74. Figure 3c shows a cross section 2~~ of a monolith reactor 80 with the passive inserts in the form of selected reinforced channel walls 82 as compared to thinner regular channel walls 84.
In the embodiment of the method using coupled-reactor stabilization, phase-shifted temperature waves develop due to the dynamical difference of companent reactors. Even if there is no heat exchange between the reactors, transient waves exist in the reactors whether or not they are thermally coupled and will in general be phase-shifted with respect to each other.
Radial heat flows between the thermally coupled reactors results in these pre-existing phase-shifted waves destructively interfering.
:5 In the embodiment of the method using passive inserts, if reactor and passive insert are not thermally coupled there will be wave in the reactor and no wave in the passive insert. lNhen the reactor and the insert are thermally coupled, the wave in the reactor induces secondary wave in the insert and drags this secondary wave downstream. The secondary wave lags behind being thus 1 () phase-shifted (phase-delayed) relative to the primary wave in the reactar. The very same radial heat flow that gives rise to the secondary wave makes the primary and the secondary waves destructively interfere.
The stabilized reactors that implement coupled-reactor- or passive-insert stabilization schemes rely on efficient heat exchange among the reactor's 1;i adjacent radial zones. This its necessary for destructive interference of the heat waves to occur or for the passive inserts to contribute their capacity to conduct heat effectively. The pitch, D, of the radial structure of a stabilized reactors, namely the distance between the neighbouring Pls or between component reactors, is determined by the distance of lateral drift of the heat within the 2() reactor's thermal response lame. For the packed-bed reactors, D
approximately equals (due"e,L)'~2, where dpe,~e, is the catalyst pellet size and L is the reactor length. Here L is representative of the reagent residence time inside the reactor (hence of the reactor thermal response time) and dPe"et represents the mean free path of the lateral turbulent heat dispersion inside the packed bed. E.g. for 2;i d~"e~ 5mm and L=2m, D=1C)cm.
Because of their greater stability, the stabilized reactors disclosed herein can be operated more aggressively than their conventional counterparts to attain higher levels of productivity. Alternatively, they can be operated more safely to extend the life-span of the catalyst and to improve the quality of the process, e.g.
selectivity in production applications, that is generally a sensitive function of temperature.
The radial heat exchange among the component reactors may be configured to occur through an additional (e.g. cooling) medium. As well, the reactors may be configured so that destructive interference of transient waves in the component reactors occurs through delayed interaction of similar or dissimilar component reactoirs through an additional (e.g. cooling) medium.
A reactor may also be: constructed in accordance with the present invention wherein the maximum temperature of the stationary hot spot and reactor parametric sensitivity are reduced through the interaction via cooling medium among the component reactors, in which stationary hot spots are positioned at different locations along the reactor axis. The difference in locations of the stationary hot spots in component reactors is achieved for example through the difference of flow velocities of reagents in said component reactors.
The following nonlimiting examples will further exemplify the method of stabilizing reactors and constructing stabilized reactors for various applications.
The coupled-reactor stabilization scheme is illustrated in Figure1 b for the co-current stabilized reactor and involves thermally coupled operation of two component reactors. The latter are designed to be dynamically different in the sense that identical perturbations evolve in them differently, e.g. propagate at different speeds. The goal is to force the same process disturbances to develop in the component reactors into heat waves that are phase-shifted relative to each other. With the reactor sizing and thermal properties appropriately chosen, radial heat exchange between the component reactors tends to suppress the temperature waves in them through the mechanism similar to destructive interference. This constitutes the adaptive mechanism of enhanced dynamic stability built into the stabilised reactor structure. As an example one may use two adiabatic packed-bed reactors with an exothermic reaction A=>B+heat, first operating independently and subsequently in a co-current arrangement.
The propagation speed of the heat waves in a packed-bed reactor is inversely proportional to its Lewis number Le = j(1-E)p,Cs + ep,C, ] /Ep,Cf (e is the void fraction of the bed; ~~5, p~ and CS, C, are the solid/fluid densities and heat capacities). The reference response of two packed-bed reactors with different Lewis numbers to a periodic perturbation is shown in Figures 4a and 4b in which the reactors operate independently. The curves 1 show the snapshots of transient temperature distributions inside the reactors: the waves that have evolved from identical perturbation are phase-shifted relative to each other.
The curves 2 show the upper and the lower temperature envelopes, the curves 3 (dotted) show the steady-state temperature profiles, and the curves 4 show the difference of the upper and lower temperature envelopes (temperature uncertainties). The perturbation is applied to the feedstream temperature, Ta, and it has amplitude 0.01 To. Transients which originate from these slight variations of the inlet temperature grow into the large-amplitude travelling waves of heat and chemical composition. The difference of upper and lower temperature envelopes which confine these waves (the temperature uncertainty) serves as a measure of reactor operational instability. Because of the difference in the Lewis numbers of the component reactors, transient waves propagate in them at different speeds and a phase-shift builds up between them.
The response of the above reactors to the same perturbation after they have been co-currently thermally coupled (Figure1 b) is shown in Figures 4c and 4d. While the steady-state temperature profiles are unaffected, the transient response is drastically reduced by the coupling. The improved stability of coupled configuration is evident: the temperature excursions are now confined to the immediate vicinity of the steady states and the temperature uncertainties are reduced both in amplitude and in width.
Another realization of the coupled-reactor approach is the counter-current stabilized reactor shown in Figure1c. Dynamic dissimilarity of component ;i reactors necessary to produce a phase-shift between the heat waves in them is inherent in this configuration since these waves propagate in opposite directions. This gives the reactor, composed of identical counter-currently coupled component reactors, a high degree of stability, as illustrated by Figure 5b (to be compared with the reference response of an isolated packed-bed reactor shown in Figure 5a). A snapshot of transient temperature distribution is shown (wavy curve) as well as temperature envelopes and uncertainty.
Packed-bed reactors with integrated counter-current heat exchange are employed in industry to achieve autothermal operation when hot reaction products preheat cold feed so that no external heat supply is necessary (Aris R., 1989, Elementary Chemical Reactor Analysis, Butterworth, Boston; Froment G. F. and Bischoff K. B., 1990, Chemical Reactor Analysis and Design, John Wiley, New York; Eigenberger G. and Nieken U., 1994, Catalytic Cleaning of Polluted Air: Reaction Engineering Problems and New Solutions, Int.Chem.Eng., 34, 4) . A famous example of this reactor type is the TVA
reactor for ammonia synthesis {see e.g. Aris R., 1989, Elementary Chemical Reactor Analysis, Butterworth, Boston). The elementary (conceptual) unit of the counter-current autothermal reactors is a reactor obtained by coupling of two basic PBRs of Figure 1 a in a counter-current arrangement of Figure 1 c (see e.g. Sun Q., Young B., Williams D.F., Glasser D. and Hildebrandt D., 1995, A Periodic Flow 2;i Reversal Reactor: an Infinitely Fast Switching Model and a Practical Proposal for its Implementation, Abstr. of the USPC-2 Conference, St. Louis, Missouri, USA.) or from a single basic packed-bed reactors by bending it at the mid-point and bringing the resultant branches into thermal contact as shown in Figure 1d. These reactor models, however, become parametrically sensitive and extinguish abruptly when the reaction zone approaches the mid-point of the tandem counter-current reactor or the knee of the bent reactor. Hence, the inlet branch [Aris R., 1989, Elementary Chemical Reactor Analysis, Butterworth, Boston] or the outlet branch (Eigenberger G. and Nieken U., 1994, Catalytic Cleaning of Polluted Air: Reaction Engineering Problems and New Solutions, Int.Chem.Eng., :14, 4) of the bent reactor or the up-(downstream halves of the component reactors in the counter-current arrangement must be emptied of catalyst. These reactor domains cannot be used because of the 1 C~ above limitation imposed on the reaction zone location. Moreover, if packed, they would produce extra hydraulic resistance of the bed. Two examples of this family of reactors are shown. schematically Figures1e and 1f. If operating conditions of two component reactors of the tandem configuration are identical, this reactor is operationally equivalent to the bent reactor with the 15 correspondence rules: c -> d, a -> f .
Stability of autothermal reactors is usually considered within the framework of parametric sensitivity approach that is based on reactor response to (infinitely) slow perturbations (Morbidelli M. and Varma A., 1982, Parametric Sensitivity and Runaway in Tubular Reactors, AIChE J., 25, 903). Dynamic 20~ aspect of the counter-current reactors stability is twofold. First, due to destructive interference of heat waves in component reactors, resonant disturbance amplification, characteristic of basic packed-bed reactors, is virtually eliminated. Secondly, thermal response time of this reactor is longer than that of single packed-bed reactor since exiting transients are reintroduced into the inlet 25 zone of adjacent component reactor. Prolonged thermal response time makes the reactor insensitive to shorter-time disturbances. This means enhanced operational stability.
The stabilizing effect of passive inserts (Pls) partially arises from destructive interference of heat waves in them and in catalyst bed. Enhanced thermal conductivity of the bed is another contributing factor. The passive insert stabilization scheme involves a single packed- or monolithic catalyst bed with passive inserts embedded in it parallel to the reactor axis. An important function of these passive inserts is to absorb a fraction of the excess reaction heat released during an upward temperature excursion and to release it later on, ideally during a downward deviation of the bed temperature. This dynamics can 1 D also be understood using the notion of secondary heat waves that are induced in passive inserts by the primary waves in catalyst bed. Due to the thermal inertia of the inserts and to the limited rate of heat exchange between them and the catalyst bed, secondary temperature waves are phase-shifted, delayed, relative to the primary ones. The result of interaction of these phase-shifted waves through radial heat flows is their destructive interference and partial annihilation. Additionally, the passive inserts conduct heat at a high rate, increasing thereby effective thermal conductivity of the bed and bringing further down both: the maximal temperatures and the temperature gradients. For optimal operation, the cumulative heat capacitance and conductance of the 2~D inserts must make up a noticeable fraction of these quantities of catalyst bed.
Figures 6a, 6b and 6c illustrate stabilizing effect of passive inserts on the transient operation of a packed-bed reactor. Figure 6a shows reference temperature response of a basic packed-bed reactor to a small-amplitude periodic perturbation of the temperature of feed (dotted curve} and response of a reactor stabilized by passive inserts (solid curve). Figure 6b shows the temperature response of catalyst bed and of passive inserts which have the form of internal wails, parallel to the reactor axis in which it can be seen that variations of the passive insert temperature are phase-delayed, relative to those of the bed. Figure 6c shows temperature envelopes for the basic packed-bed reactor (reference response) and for the passive insert-stabilized packed-bed reactor in which it can be seen that the degree of stabilization is quite appreciable.
In automotive and power/heat generation applications of monolith reactors, the reactor length is considerably smaller and flow velocity is considerably higher than in packed-bed reactor of chemical industry. The resulting short residence times limit the efficiency of solid/fluid heat and matter exchange and inter-phase concentration and temperature gradients are correspondingly large. Inter-phase heat flow resistance exerts a stabilizing influence on reactor operation, playing a role similar to that of axial heat conduction (Chen Y. C. and Luss D., 1989, Wrong-Way Behavior of Packed Bed Reactor: Influence of Interphase Transport, AIChE J., 35,1148). In production applications however, as exemplified by S02 => S03 oxidation in sulfuric acid manufacture (U.S. Patent No. 5,264,200), monolith reactors operating conditions are close to those of packed beds with residence times on the scale of 1 s. Under these conditions monolith reactors may operate as resonant amplifiers of perturbations, as illustrated in Figure7a. The hot-spot activity then can be controlled through implementation of the CR approach in the form of checkerboard monolith, shown in Figure2c. Figure7a illustrates the improved dynamic stability of a checkerboard monolith reactor relative to the basic monolith reactor. The passive-insert stabilization scheme is also applicable to monolith reactors as illustrated by Figure 7b.
The foregoing description of the preferred embodiments of the invention has been presented to illustrate the principles of the invention and not to limit the invention to the particular embodiment illustrated. It is intended that the scope of the invention be defined by all of the embodiments encompassed within the following claims and their equivalents.
Claims (24)
1. A method of adaptive control of temperature fluctuations arising from transient heat waves in exothermal catalytic reactors, comprising:
providing at least two component exothermal catalytic reactors, each of said at least two component exothermal catalytic reactors including means for inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into different, phase-shifted temperature waves; and thermally coupling said at least two component exothermal catalytic reactors so that heat exchange occurs between said at least two component exothermal catalytic reactors in the radial direction, wherein said phase-shifted temperature waves in each of said at least two component exothermal catalytic reactors destructively interfere through radial inter-reactor heat flow thereby dampening said temperature fluctuations and reducing deviations of reactor temperature fields from desirable steady state temperature profiles.
providing at least two component exothermal catalytic reactors, each of said at least two component exothermal catalytic reactors including means for inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into different, phase-shifted temperature waves; and thermally coupling said at least two component exothermal catalytic reactors so that heat exchange occurs between said at least two component exothermal catalytic reactors in the radial direction, wherein said phase-shifted temperature waves in each of said at least two component exothermal catalytic reactors destructively interfere through radial inter-reactor heat flow thereby dampening said temperature fluctuations and reducing deviations of reactor temperature fields from desirable steady state temperature profiles.
2. The method according to claim 1 herein said means for inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into different, phase-shafted temperature waves includes the component reactors comprising interior elements of different heat capacity or operating said thermally coupled component catalytic reactors under different operating conditions.
3. The method according to claim 1 wherein the at least two exothermal catalytic reactors are selected from the group consisting of packed-bed and monolith reactors.
4. The method according to claim 3 wherein said component catalytic reactors are coupled co-currently wherein the component reactors are positioned adjacent to each other, wherein reactants are flowed through the component reactors in substantially the same direction, and wherein the transient temperature waves produced in adjacent component reactors are phase shifted relative to each other due to adjacent component reactors being operated under different operating conditions.
5. The method according to claim 4 wherein the different operating conditions of the two or more component catalytic reactors are produced by having different operating conditions for each of the at least two component reactors.
6, The method according to claim 4 wherein different operating conditions include using in the component reactors different flow rates and/or reactions With different reaction kinetics and/or different reactant concentrations and/or different inlet temperatures.
7, The method according to claim 2 wherein said at least two component catalytic reactors each include catalyst carriers having sufficiently different heat capacity such that transient waves propagate at different speeds in said at least two component reactors so that the phase shifts develop between the transient heat waves.
8. The method according to claim 3 wherein said at least two component reactors are positioned adjacent to each other and operated in a counter-current configuration wherein reactants are flowed through any two immediately neighboring component reactors in substantially opposite directions, and wherein any two immediately neighboring component reactors has a portion that is emptied of catalyst.
20~~
20~~
9. The method according to claim 8 wherein the portions of the immediately neighboring component reactors emptied of catalyst substantially do not overlap.
10. The method according to claim 9 wherein each of said at least two component reactors have a length, and wherein the portions emptied of the catalyst in each component reactor is substantially half the length of the associated reactor.
11. The method according to claim 1 where radial heat exchange among the at least two component reactors occurs through an additional cooling medium thermally coupled to said at least two component reactors.
12. An exothermal catalytic reactor with adaptive control of temperature fluctuations arising from transient heat waves, comprising:
at least two component exothermal catalytic reactors each having a longitudinal direction, said at least two component exothermal catalytic reactors being thermally coupled so that heat exchange occurs between said at least two component exothermal catalytic reactors in the radial direction;
each of said at least two component exothermal catalytic reactors including means for inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into different, phase-shifted temperature waves, wherein said phase-shifted temperature waves in each of said at least two component exothermal catalytic reactors destructively interfere through radial inter-reactor heat flow thereby dampening said temperature fluctuations and reducing deviations of reactor temperature fields from desirable steady state temperature profiles.
at least two component exothermal catalytic reactors each having a longitudinal direction, said at least two component exothermal catalytic reactors being thermally coupled so that heat exchange occurs between said at least two component exothermal catalytic reactors in the radial direction;
each of said at least two component exothermal catalytic reactors including means for inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into different, phase-shifted temperature waves, wherein said phase-shifted temperature waves in each of said at least two component exothermal catalytic reactors destructively interfere through radial inter-reactor heat flow thereby dampening said temperature fluctuations and reducing deviations of reactor temperature fields from desirable steady state temperature profiles.
13. The reactor according to claim 12 wherein said means for inducing identical process disturbances to propagate in said at least two component catalytic reactors at different speeds and evolve into different, phase-shifted temperature waves includes each component reactor comprising interior elements having a heat capacity different from the other component reactors.
14. The reactor according to claim 12 or 13 wherein the at least two exothermal catalytic reactors are selected from the group consisting of packed-bed and monolith reactors.
15. The reactor according to claim 14 wherein said at least two exothermal component catalytic reactors is two exothermal component catalytic reactors coupled co-currently wherein the two component reactors are positioned adjacent to each other, wherein reactants are flowed longitudinally through the component reactors in the same direction during operation.
16. The reactor according to claim 15 including an additional cooling medium thermally coupled to said two exothermal component catalytic reactors, and wherein radial heat exchange between the at two exothermal component catalytic reactors occurs through the additional medium.
17. The method according to claims 13 or 14 wherein each of said exothermal catalytic reactors include catalyst carriers having a heat capacity sufficiently different from the catalyst carriers in the other exothermal catalytic reactors such that transient waves propagate it said component reactors at different speeds so that the phase shifts develop between the transient heat waves.
18. The method according to claim 12 wherein said at least two component exothermal catalytic reactors are two exothermal catalytic reactors positioned adjacent to each other and operated in a counter-current configuration wherein reactants flow through the two exothermal catalytic reactors in substantially opposite directions, and wherein each of the two exothermal catalytic reactors has a portion that is emptied of catalyst.
19. The method according to claim 18 wherein the two portions of the two reactors emptied of catalyst substantially do not overlap.
20. The method according to claim 19 wherein each of said at least two component reactors have a length, and wherein the portions emptied of the catalyst in each component reactor is substantially half the length of the associated reactor.
21. The reactor according to claim 12 wherein a maximum temperature of stationary hot spots and reactor parametric sensitivity are reduced through the interaction of an additional cooling medium among the component reactors, and wherein stationary hot spots are positioned at different locations along the reactor axis.
22. The reactor according to claim 21 where difference in locations of the stationary hot spots in component reactors is achieved through the difference of flow velocities of reagents in said component reactors.
23. A ceramic monolith reactor, comprising:
cross-sectional areas of different thermal, geometrical or operational properties, alternating in a checker-board or different manner, so that transient temperature waves in adjacent cross-sectional areas of said reactor with appropriately different properties accumulate in the course of their propagation a certain phase-shift and through radial heat flows dampen each other so as to promote operational stability.
.ANG.
cross-sectional areas of different thermal, geometrical or operational properties, alternating in a checker-board or different manner, so that transient temperature waves in adjacent cross-sectional areas of said reactor with appropriately different properties accumulate in the course of their propagation a certain phase-shift and through radial heat flows dampen each other so as to promote operational stability.
.ANG.
24. A ceramic diesel particulate-matter trap, comprising:
a wall-flow monolith with cross-sectional areas of different thermal, geometrical or operational properties, alternating in a checker-board or different manner, so that transient regeneration waves in adjacent cross-sectional areas of said diesel particulate-matter trap with appropriately different properties accumulate in the course of their propagation a certain phase-shift and through radial heat flow dampen each other sa as to promote operational stability.
a wall-flow monolith with cross-sectional areas of different thermal, geometrical or operational properties, alternating in a checker-board or different manner, so that transient regeneration waves in adjacent cross-sectional areas of said diesel particulate-matter trap with appropriately different properties accumulate in the course of their propagation a certain phase-shift and through radial heat flow dampen each other sa as to promote operational stability.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US8859698P | 1998-06-09 | 1998-06-09 | |
| US60/088,596 | 1998-06-09 | ||
| PCT/CA1999/000523 WO1999064145A1 (en) | 1998-06-09 | 1999-06-09 | Method for adaptive control of exothermal catalytic reactors and reactors therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2333549A1 true CA2333549A1 (en) | 1999-12-16 |
Family
ID=22212295
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002333549A Abandoned CA2333549A1 (en) | 1998-06-09 | 1999-06-09 | Method for adaptive control of exothermal catalytic reactors and reactors therefor |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU4126099A (en) |
| CA (1) | CA2333549A1 (en) |
| WO (1) | WO1999064145A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008058918A1 (en) * | 2006-11-15 | 2008-05-22 | Basf Se | Process for conducting an exothermic heterogeneously catalyzed partial gas phase oxidation of an organic starting compound to an organic target compound |
Family Cites Families (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2418837A (en) * | 1942-04-04 | 1947-04-15 | Houdry Process Corp | Contacting apparatus |
| BE547489A (en) * | 1955-05-27 | 1900-01-01 | ||
| BE566186A (en) * | 1957-04-18 | |||
| FR1448758A (en) * | 1964-09-09 | 1966-03-18 | Fr Des Produits Pour Catalyse | Device for self-regulation and homogenization of the temperature in a bed of catalyst grains with low thermal conductivity |
| US3957619A (en) * | 1974-02-11 | 1976-05-18 | Gulf Research & Development Company | Process for the conversion of carbonaceous materials |
| US4101287A (en) * | 1977-01-21 | 1978-07-18 | Exxon Research & Engineering Co. | Combined heat exchanger reactor |
| US4521532A (en) * | 1984-04-23 | 1985-06-04 | General Motors Corporation | Monolithic catalytic converter for improved thermal performance |
| DE3435319A1 (en) * | 1984-09-26 | 1986-04-03 | Michael 4150 Krefeld Laumen | CATALYTIC STEAM GENERATOR |
| GB8530984D0 (en) * | 1985-12-17 | 1986-01-29 | Ici Plc | Gas turbines |
| PL163570B1 (en) * | 1990-05-18 | 1994-04-29 | Inst Chemii Nieorganicznej | Fixed catalyst reactor with internal heat exchange |
| US5250489A (en) * | 1990-11-26 | 1993-10-05 | Catalytica, Inc. | Catalyst structure having integral heat exchange |
| GB2269764A (en) * | 1992-08-18 | 1994-02-23 | Rolls Royce Plc | A catalytic combustion chamber |
| DE4240143C2 (en) * | 1992-11-28 | 1995-10-19 | Leuna Werke Gmbh | Process for the continuous implementation of exothermic reactions in a fixed bed cycle reactor |
| US5525311A (en) * | 1994-05-02 | 1996-06-11 | Uop | Process and apparatus for controlling reaction temperatures |
| DE4444364C2 (en) * | 1994-12-14 | 1998-03-26 | Chemtec Leuna Ges Fuer Chemie | Fixed bed reactor for the continuous implementation of exothermic reactions |
| JP3012167B2 (en) * | 1995-04-12 | 2000-02-21 | 日本碍子株式会社 | Exhaust gas purification filter and exhaust gas purification device using the same |
| NL1000146C2 (en) * | 1995-04-13 | 1996-10-15 | Gastec Nv | Method for performing a chemical reaction. |
| DE19624435C1 (en) * | 1996-06-19 | 1997-08-28 | Daimler Benz Ag | Mobile, economical, compact steam-methanol reformer |
-
1999
- 1999-06-09 AU AU41260/99A patent/AU4126099A/en not_active Abandoned
- 1999-06-09 WO PCT/CA1999/000523 patent/WO1999064145A1/en active Application Filing
- 1999-06-09 CA CA002333549A patent/CA2333549A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| AU4126099A (en) | 1999-12-30 |
| WO1999064145A1 (en) | 1999-12-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Cybulski et al. | Monoliths in heterogeneous catalysis | |
| Irandoust et al. | Monolithic catalysts for nonautomobile applications | |
| Zheng et al. | Numerical simulation of selective catalytic reduction of NO and SO2 oxidation in monolith catalyst | |
| Tronconi et al. | Selective catalytic removal of NOx: a mathematical model for design of catalyst and reactor | |
| Kolios et al. | Heat-integrated reactor concepts for catalytic reforming and automotive exhaust purification | |
| KR100868955B1 (en) | Radial flow gas phase reactor and method for reducing the nitrogen oxide content of a gas | |
| Sadeghi et al. | Investigating the effect of channel geometry on selective catalytic reduction of NOx in monolith reactors | |
| Marín et al. | Monoliths as suitable catalysts for reverse‐flow combustors: modeling and experimental validation | |
| KR100851663B1 (en) | Reactor and method for reducing the nitrogen oxide content of a gas | |
| Chen et al. | Structure-resolved CFD simulations to guide catalyst packing of selective NO reduction | |
| CA2333549A1 (en) | Method for adaptive control of exothermal catalytic reactors and reactors therefor | |
| Kommu et al. | Ignition of homo/hetero combustion of propane in a microreactor with catalyst segmentation | |
| Cominos et al. | Theoretical investigation of axially non-uniform catalytic monoliths for methane combustion | |
| Budzianowski et al. | Auto‐thermal combustion of lean gaseous fuels utilizing a recuperative annular double‐layer catalytic converter | |
| JP5292103B2 (en) | Controlled combustion for regenerative reactor with mixer / flow distributor | |
| JPH05501379A (en) | Apparatus for carrying out catalysis in granular beds | |
| Hevia et al. | Design and testing of a control system for reverse‐flow catalytic afterburners | |
| JP4521513B2 (en) | Internal heating type heat exchange structure | |
| Miranda et al. | Stability of a Feed-Effluent Heat Exchanger/Reactor system for catalytic combustion of VOCs: Influence of variable emission patterns | |
| García-Bordejé et al. | Study of configuration and coating thickness of vanadium on carbon-coated monoliths in the SCR of NO at low temperature | |
| CA2784914A1 (en) | Hybrid reactor with two reaction zones | |
| Yakhnin et al. | Convective instability and its suppression in packed-bed-and monolith reactors | |
| US20020159923A1 (en) | Gas phase reactor and process for reducing nitrogen oxide in a gas stream | |
| Cybulski et al. | Structured reactors, a wealth of opportunities | |
| JPH0867502A (en) | Fuel reformer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |