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Methanol Stream Reforming For Hydrogen Production

Abstraction:

Methanol is extensively used in production of H through heterogenous contact action due to it high Hydrogen-Carbon ratio. Micro-reactors used for the methyl alcohol steam reforming has shown promising consequences and enkindled extended research in last 2 decennaries. This study discusses 3 novel thoughts to develop a simplified theoretical account of Heterogeneous contact action. It addresses the single draw dorsums of a accelerator by multilayer deposition of two different sort of accelerator in the same reactor. And has explores the thought of increasing the output from general combination of basic unit micro-reactor under safer bounds of temperature and force per unit area. The fresh thoughts discussed includes the combination of two mirror imaged micro-reactor in to one individual unit known as Micro R+ . And later stacking them together to organize a Parallel reactor Mega M

Introduction:

Because of increasing demand of energy, diminishing resources of conventional Fuels and planetary heating, the demand for greener and high efficiency fuel has increased. Since last century a batch of ways has been presented by the scientist around the universe for the solution but merely few denumerable methods can be applied practically. Hydrogen fuel cell is one of the most effectual engineering which shown a high potency for managing all the energy demand of the modern universe. It was foremost developed in 1839 by sir William Grove and is now considered as the energy beginning for the hereafter ( Llinich, et al. , 2008 )

An extended research has been initiated all around the universe for development & A ; optimisation since last two decennaries for the production of H on illumination graduated table, so that it can be safe and easy incorporated in applications. However the engineering has shown the promising consequences in laboratory graduated table theoretical accounts, but could non be successfully applied extensively on commercial graduated table. This is because of the trouble in commanding non merely the reactant and merchandise but the reaction itself. Merely really few theoretical accounts were successfully proposed and implemented commercially.

Methanol has been shown good consequences in both, in direct usage of fuel cell every bit good as in the precursor for the H fuel cell. Methanol can be obtained from natural perishable hydrocarbon beginnings every bit good as from petroleum oil and natural gas. For commercial intents, methyl alcohol is chiefly produced from natural gas through a syngas path. Syngas is so converted to methanol over Cu accelerator at around 200 & A ; deg ; C. In 1960, a really active Cu-based accelerators was developed which revolutionized the catalytic procedure ( Jiang, 1993 ) . And since so there has been a batch of development in the field of Heterogeneous contact action for H forming from methyl alcohol. Today, a finely tuned Cu/ZnO with Alumina ( Al2O3 ) composing is employed for the same procedure.

Steam reforming of methane produces a mixture of CO2, CO, and H2 harmonizing to combining weight ( 1 ) & A ; ( 2 ) .

Methanol can be converted to hydrogen at low temperatures ( 150-350 & A ; deg ; C ) than most other fuels ( & gt ; 500 & A ; deg ; C ) because it has no carbon-carbon bonding. It can easy be activated at low temperatures than methane. Low-temperature transition leads to low degrees of CO formation, even if the accelerator provides no particular mechanism for selectivity of CO2 over CO. But low temperature will take to long abode clip and high degree of methane formation, without a accelerator. This will be a serious job for the H production. But in Presence of a accelerator, the reforming of the methyl alcohol to hydrogen will be at higher rate and good selectivity.

Effectiveness of Cu-based accelerators in the production of methyl alcohol which occur of course led to their probe in the steam reforming of methyl alcohol, which can be seen as the contrary of reaction equation ( 3 )

An surplus of steam to the same reaction under assorted Cu assorted accelerator can bring forth the equation ( 1 ) so as to maintain the reaction frontward.

Assorted accelerators were used for the intent as change overing methyl alcohol to H.

There are many accelerators proposed for the procedure, and all plants with different selectivity and different rate transition. It is by and large seen that the higher the temperature more is the CO formation, which may take to the accelerator toxic condition. CO, antonym to CO2 has a really high surface assimilation rate to the accelerator, which can impact the overall rate of transition, and debasement of the accelerator.

There are assorted accelerators which were proposed in changing combinations to undertake this job but merely tried and tested for little or micro-scale degrees and besides deducing the rate equation will be more complex than that for the single accelerators.

Micro-reactors are micro-channel plotted on an inert or on an active substrate which may or may non take portion in the reaction mechanism. These devices are devised to obtain the high efficiency outputs, as they worked on a molecular degree. They improve mass and heat transportation by cut downing the effectual conveyance distance and increasing interfacial country per unit reactor. They suppress heat accretion countries and enabling safer operations. The Micro-reactors can run under conditions that can non be easy attained in conventional reactor systems because of fixed and good defined features, high heat and mass transportation rates, spacial and temporal control over temperature, blending and abode clip.

The purpose of the undertaking is to develop a theoretical account to maximize the rate transition and selectivity of the micro-reactor for H production by methanol steam reforming procedure. Simultaneously, it is to develop a high capacity theoretical account with the simplified equation of rate, within the safer possible procedure parametric quantities.

Challenges faced:

To develop a methanol-based system for the production of the H is non simple in any footings, though there are other engineerings such as Partial Oxidation and Auto-thermal Reforming, Pyrolysis, etc. involves much more than merely the steam reforming and associated procedure operations. There are specific system challenges that have great bearing on type of system selected, how it is operated, how it is deployed, and finally how it performs practically.

The study discuss the proficient challenges related to the system as a whole, and the focal point remains on the portable power applications, which is where most of the methyl alcohol steam reforming work is directed.

Literature study:

Hydrogen can be produced by assorted methods which are as follows:

Plasma Reforming.

Electricity is used to make a plasma which generates energy and forms the free groups required for reforming. ( Biniwale, 2004 ; Bromberg, 1999 ; O’Brien, 1996 ; Paulmier, 2005 ; Czernichowski, 2003 ; Sekiguchi, 2003 ) . Usally steam is used to organize free groups, such as H+ , OH- , and O- when injected with a fuel the negatrons fascilitates redox reactions ( Sekiguchi, 2003 ) .

Plasma reforming has many advantages, such as deficiency of accelerator, smaller systems and lower operating temperature, high response clip and riddance of poisoning factor. ( Biniwale, 2004 ; Bromberg, 1999 ; O’Brien, 1996 ; Czernichowski, 2003 ) The chief disadvantage of Plasma reforming is the demand for electricity.

Besides, the electrodes used in the procedure tends to gnaw during the operation which will add in to the care cost

Pyrolysis.

Decomposition of hydrocarbons into H and C in a H2O and air less/free environment is known as pyrolysis and can be done with organic stuff. ( Muradov, 2003 ) If no H2O or air is present, accordingly no C oxides will formed. This procedure offers important emanations decrease. Since no CO or CO2 is present, extra secondary reactors are non necessary for down watercourse reactors.

Pyrolysis can reply the inquiry for the increasing concerns over CO2 emanations. It may play a important function in environmental protection, since it can able to retrieve a important sum of the C as a solid ( Muradov, 2003 ; Guo, 2005 ) .

Pyrolysis procedure requires vaporisers, a pyrolysis reactor, and restorative heat money changers in a typical apparatus. One of the major drawbacks is the deposition of C as a fouling agent for effectual heat transportation, which is formed as a by-product. ( Guo, 2005 ) This can do the procedure limited to relatively big installings merely where C remotion will be done easy.

Partial Oxidation and Auto-thermal Reforming.

Hydrocarbon is being used on widely for big graduated table H production, such as for car fuel ( Trimm et al. , 2001 ; Hohn et al. , 2001 ; Krummenacher et al. , 2003 & A ; Pino et al. , 2002 ) . It employs a non-catalytic partial oxidization of hydrocarbons in the presence of O and steam at temperature runing from 1300-1500 & A ; deg ; C to obtain a high transition and cut down the C carbon black formation ( Rostrup-Nielsen et.al. , 2003 ) . A accelerator is some clip used to cut down the operating temperature, nevertheless, it is hard to command because of coking and heat accumulatione ( Trimm et.al. , 2001 ; Song, 2002 ; Pietrogrande et al. , 1993 ; Hohn, 2001 ; Krummenacher et al. , 2003 ; Pino et al. , 2002 ) . ( Krummenacher et al. , ) it has shown good consequences in non-portable signifiers but it can non be suited for light and portable devices.

Aqueous Phase Reforming.

When H is produced from oxygenated hydrocarbons and saccharides it is known as Aqueous Phase Reforming. ( Cortright, 2006 ; Cortright, 2002 ; Davda, 2003 ) These reaction occur in a high force per unit areas ( 25-30 MPa ) and temperatures ( 220-750 & A ; deg ; C ) even with a accelerator.

This method is non suited due to high heat and force per unit area demands. Catalyst are being researched to get the better of this job

Ammonia Cracking.

Ammonia is one of the strongest rival for the methyl alcohol steam reforming as it is cheap as a fuel and has been proposed for fuel cells in portable power applications.

Energy denseness of Amonia is 8.9 kilowatt H kg-1, which is higher than that of methyl alcohol i.e.5.5 kilowatt h kg-1 but it is less than that of Diesel i.e.13.2 kilowatt h kg-1.

Ammonia checking takes topographic point under endothermal conditions and is considered as the rearward reaction of synthesis.

But Ammonia is synthesised at really high temperature and force per unit area this made ammonium hydroxide a comparatively less investigated boulder clay now.

There are many techniques for H coevals by reforming and from figure of beginnings every bit good to the fuel cells But the pick ever remain with the production of H alternatively of storage as it is more unsafe to manage in molecular signifier.Though the pick is dependent upon the demand of the terminal user but in general the safer engineering is most preferable over the otherwise. Therefore, Using micro-reactors is a feasible option for steam reforming of methyl alcohol.

Assorted accelerators used in the micro-reactors:

  1. Cu/ZnO
  2. Cu/ZnO/Alumina ( Al2O3 )
  3. Pd/ZnO
  4. Pd/ZnO/ Alumina ( Al2O3 )
  5. Mixtures of different Catalyst in varing % ages.

There are many challenges faced in both signifiers of accelerator ( separately and in combinatipon ) in micro-reactors. Particularly in deducing rate equations, Poisoning etc.

Methodology:

There are three wide stairss involved in the fiction of new micro-reactor. These are

  1. Writing the micro-reactors mirror images
  2. Joining the two mirror imaged micro-reactor as MicroR +
  3. Stacking the individual unit of MicroR+ to organize Mega-M 1

Writing the micro-reactors mirrors:

There are two basic stairss in the fiction of the Primary unit. The first measure is the basic unit of the Mega-M1 is the basic micro-reactor fabricated most normally in today ‘s clip, get downing from lithographic authorship of PMMA +ve templet which will bring forth the parent -ve Template. The 2nd measure is by utilizing Electron beam vapor deposition technique for composing the accelerator on to the surface of the channels.

a. The first measure is the foundations for the new reactor in which even Numberss of precisely same micro-reactors of ceramic substrate will be fabricated utilizing a PMMA templets fabricated from Parent ceramic templet itself. The lone alteration in the design will be go forthing a little hole in all the reactors except for two which will hold hole merely on one side on the substrate home base in such a manner so that they lie on the alternate path.

The Production rhythm is being given in fig.1

( Fig.1 ) Process flow diagram of Ceramic Micro-reactor production

In the 2nd measure the beds of copper and Pd accelerator along with ZnO and Alumina will be coated. But will be in separate zones in micro-reactors. The zones were divided under the doctrine that the micro-reactor will be immune to high temperature and toxic condition every bit good as high in transition rate. As shown in figure 2

Joining of the two mirror imaged micro-reactor as MicroR + .

The two micro-reactors can be joined by carefully utilizing the same ceramic which has been used for the substrate of the micro-reactor. The procedure stairss are briefly described in the procedure fig 4. below.

Fig 4. Cementing of two microreactors.

Stacking the individual unit of MicroR+ to organize Mega -M1:

The individual unit of microR+ is placed on the top of the each other really carefully so as to obtain a sandwiched superimposed construction of the micro-reactor. The stacking should hold the recess at one face and the mercantile establishment on the other face of the reactor but at the underside. This construction will let the equal distribution of reactants over the catalytic surface inside the channels.

As shown in the diagram.The stacking can be hold together by a Plate and frame type heat money changer agreement in fig 5. between the two supports.

Fig 5. Plate Heat Ex. Type Assembly of MicroR+ : Mega M

Comparison to the conventional methods

Conventionally the micro-reactors were used as a individual unit and homogenously coated with the accelerator or mixture of accelerators

Mega M has the following comparing with the conventionally used micro-reactor:

Mega M is a multiple bed micro-reactor which can able to bring forth more volume through them the. It can besides promote the graduated table up design of the micro-reactor. it can be calculated by using one of the most simple manner to cipher rate as each accelerator as map of surface country of the micro-reactors from the Langmuir- Hinshelwood dynamicss. The consequence of temperature in this reactor will be minimal. The consequence of CO Poisoning on this reactor will be minimal as the initial transition will be Catalysed by Pd which show really less production of CO.

Freshness:

The procedure can be considered Novel in Various ways:

  1. Layered surfacing for micro-reactor channels can supply the better manner of reforming
  2. MicroR+ can be considered as an safer manner to increase the volume of output without impacting the rate transition
  3. Stacking the MicroR+ in to Mega M1 can besides be considered as a fresh manner to bring forth a high volume output but the % transition needs to be studied by experimentation.
  4. All the method described above can taken up as a broader attack to develop more specific theoretical accounts for farther survey.

Decision

The New Reactor Micro-R+ and MegaM1 shows a promising promotion in the Fieldss of micro-reactors as supplying the new and fresh method of maintaining the Rate equation simple every bit good as increasing the output volume of the reactor.

There may be a opportunity of heat accretion in the MegaM1 due to low heat transportation rate between the ceramic substrate. But this job can be overcome by presenting thermocouples between the two MicroR+ units.

Mention

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