WO2012069850A1

WO2012069850A1 - Steam production

Info

Publication number: WO2012069850A1
Application number: PCT/GB2011/052330
Authority: WO
Inventors: Clive Telford; Lucy Igoe; Franck Letellier
Original assignee: Oxford Catalysts Limited
Priority date: 2010-11-25
Filing date: 2011-11-25
Publication date: 2012-05-31
Also published as: AU2011333502A1; GB201020052D0

Abstract

Apparatus and methods for producing steam are disclosed. In particular, the apparatus may comprise a reactor having at least one inlet and an outlet, at least one steam generation catalyst, and one or more of a pressure source capable of generating a pressure of greater than 0.1 MPa within the reactor; and a failsafe mechanism (30,32) operable to automatically deactivate a pressure source.

Description

STEAM PRODUCTION

TECHNICAL FIELD

This invention relates to apparatus and methods for steam production.

BACKGROUND ART

Apparatus and methods for producing steam are disclosed in WO 2009/013514 A 1.

DISCLOSURE OF THE INVENTION

A first aspect of the invention provides an apparatus for the production of steam, comprising a reactor comprising an inlet and an outlet; a steam generation catalyst positioned within the reactor; and a pressure source capable of generating a pressure of greater than 0.1 MPa within the reactor. The apparatus may be for use in a method of the second aspect of the invention.

A second aspect of the invention provides a method for generating a product stream comprising steam, said method comprising contacting a peroxide solution and an alcohol solution in the presence of a steam generation catalyst, wherein the peroxide solution comprises less than 12 wt% peroxide and the alcohol solution comprises less than 4 wt% alcohol. The method may be performed using the apparatus of the first aspect of the invention.

A third aspect of the invention provides an apparatus for shutting down a steam generation reaction, comprising a failsafe mechanism operable to automatically deactivate a pressure source. The apparatus may be used in conjunction with the apparatus and method of the first and/or second aspects of the invention. The failsafe mechanism may form part of an apparatus for the production of steam, comprising a reactor comprising an inlet and an outlet; a steam generation catalyst positioned within the reactor; and a pressure source, and may be operable to automatically deactivate the pressure source. A fourth aspect of the invention provides a heat source that acts on a steam generation catalyst. The apparatus may be used in conjunction with the apparatus and method of the first, second and/or third aspects of the invention. The heat source may form part of an apparatus for the production of steam, comprising a reactor comprising a first inlet and an outlet; and a steam generation catalyst positioned within the reactor, and may be operable to act on the steam generation catalyst. A fifth aspect of the invention provides an apparatus comprising a modified reactor for the production of steam in a multi-step reaction. The apparatus may be used in conjunction with the apparatus and methods of the first, second, third and/or fourth aspects of the invention. Thus, the modified reactor, which comprises a first inlet, a second inlet and an outlet; a steam generation catalyst positioned within the reactor between the first inlet and the second inlet; and a steam generation catalyst positioned within the reactor between the second inlet and the outlet may form part of an apparatus for the production of steam. The sixth aspect of the invention also provides a method for generating steam, comprising feeding a first reactant to the first inlet of the apparatus for the production of steam and a second reactant to the second inlet of the apparatus for the production of steam, wherein one of the first reactant and the second reactant comprises a peroxide and the other comprises an alcohol.

A sixth aspect of the invention provides a method for generating steam, comprising feeding a peroxide and an alcohol into the inlet of the apparatus of the first, third, fourth and/or fifth aspects of the invention.

Thus, the invention provides apparatus and methods for steam production that are improved in terms of safety, efficiency, and catalyst longevity as compared to the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1, Figure 2 and Figure 3 are schematics showing different arrangements for feeding reactants to the reactor.

Figure 4 and Figure 5 are schematics showing apparatus for the production of steam that include failsafe mechanisms.

Figure 6 is a schematic showing an apparatus for generating and analysing steam.

Figure 7 is a graph showing the fuel conversion obtained using the apparatus shown in Figure 6 as a function of pressure.

Figure 8, Figure 9 and Figure 10 are graphs showing the effect of catalyst preheating on effluent emission.

DETAILED DESCRIPTION OF THE INVENTION

Features of the various aspects of the invention are described in more detail below. Features related to one aspect of the invention are also, where applicable, features of the other aspects of the invention. It will be recognised that features specified in one embodiment of the invention may be combined with other specified features to provide further embodiments. Unless indicated to the contrary, any pressures mentioned herein are absolute pressures.

The conversion factors for the conversion of ppmw to ppmv in wet gases are proportional to the ratio of the molar weight species to water. These are CH₃OH = 0.5622; HCHO = 0.60 and methylformate = 0.30 to translate ppmw condensate results into ppmv wet gas.

Reactor

The reactor may be designed to withstand pressures of greater than 0.1 MPa (all pressures quoted herein are given as absolute pressures unless stated otherwise) and the temperatures produced by steam generation. Thus, the reactor may suitably be constructed from metal {e.g. Al, steel, in particular stainless steel), although other materials may be used if capable of withstanding the pressures, temperatures and chemical atmospheres of steam generation {e.g. glass, such as Pyrex, and high temperature plastics). The reactor may be surrounded by an insulation layer to protect a user and to improve efficiency by the retention of heat. The reactor may comprise an inlet for receiving a single stream of reactants, or in some embodiments may comprise two or more inlets, thus enabling it to receive a plurality of reactant streams. Each inlet may be in fluid communication with a reservoir containing one or more reactants. The reactor also comprises an outlet, from which steam may be released.

The reactor may be, for example, an impregnated tube reactor, a fixed bed reactor, or a microchannel reactor. The reactor may be an air gap reactor comprising an internal reactor housing the steam generation catalyst separated from an external envelope by an air gap, which may increase efficiency and minimise thermal mass, thus allowing a rapid start to the steam generation reaction. In some embodiments, the reactor is a pressurised water reactor (PWR) . This type of reactor operates in both liquid and gas phases (a triphasic system), in which steam, liquid water, oxygen, and C0₂ exist together. Such a reactor may include cooling circuits that use a compressed fluid, such as water/steam, to carry heat away from the heart of the reactor. If the reactor is a PWR, then the steam generation reaction may take place mostly {i.e. > 50 %) in the liquid phase.

The reactor houses a steam generation catalyst. The steam generation catalyst is a catalyst that may promote the decomposition or reaction of one or more reactants to generate steam. The steam generation catalyst may be coated onto a surface of the reactor, or may take the form of a porous monolith, a honeycomb or chunks, extrudate, pieces, pellets, spheres, or a combination thereof. The steam generation catalyst may be packed in a catalyst bed with SiC and may be held in place by one or more porous screens, which may further serve to distribute reactants evenly across the catalyst. In some embodiments, the reactor houses two or more steam generation catalysts, which may be the same or different. In some embodiments, one catalyst may initially generate steam whilst a second catalyst may remove unsafe effluents (e.g. by causing them to react to create additional steam and C0₂) from the products exiting the reactor.

In some embodiments, the reactor comprises a heat source (e.g. an electric heater) that may act on at least one steam generation catalyst. Preferably, the heat source is in thermal communication with the at least one steam catalyst, i.e. direct thermal communication or thermal communication through one or more other objects such as the wall of the reactor. The heat source typically acts on the catalyst towards the outlet of the reactor to avoid heating incoming reactants in order to minimise the risk of causing them to ignite or decompose. Preferably, the heat source is in contact (i.e. direct thermal communication) with the steam generation catalyst such that the steam generation catalyst can be heated without also heating any incoming reactants.

The heat source may be capable of preheating (i.e. heating before the steam generation reaction commences) the steam generation catalyst up to 300 °C, up to 500 °C or up to 700 °C. An advantage of preheating the steam generation catalyst is that the reaction can be started up with the catalyst at a sufficiently high temperature prior to contact with reactants, thus reducing the output of unsafe effluents (e.g. CO, HCOH, HCOOH, HCOOCH₃, CH₃OH etc) as compared to a catalyst operated from a cold start.

The heat source may continue to heat the steam generation catalyst for all or part of the time during which the reactants are in contact with the catalyst. An advantage of heating the steam generation catalyst is a reduction in the output of unsafe effluents (e.g. CO, HCOH, HCOOH, HCOOCH₃, CH₃OH etc throughout the reaction time.

In one embodiment, the apparatus may comprise a pressure source which, when in operation, causes reactants to flow into the reactor; and a failsafe mechanism operable to automatically deactivate the pressure source. The failsafe mechanism may operate by detecting levels of one or more unsafe effluents (e.g. CO, HCOH, HCOOH, HCOOCH₃, CH₃OH etc). The failsafe mechanism would then automatically deactivate the pressure source when a critical level of one or more of the unsafe effluents was detected. Since heating of the steam generation catalyst reduces the output of unsafe effluents, monitoring the levels of unsafe effluents is an indirect method of monitoring the efficacy of the steam generation catalyst heating.

The failsafe mechanism is described in more detail hereinafter. The reactants may be supplied to the reactor from one or more reservoirs, and may be pre- mixed outside the reactor. Figure 1 illustrates this and shows a single reactant stream (2) moving into the inlet (4), over the catalyst bed (6) where it is converted into a single product stream (8) and passes through the outlet (10).

In some embodiments, the reactants may be supplied from separate reservoirs and mixed prior to entering the reactor, or a mixture of reactants may be supplied from a single reservoir. In other embodiments, where the reactor has two or more inlets, the reactants may be mixed in the reactor prior to contact with the catalyst. For instance, the reactor may comprise an ante chamber in which mixing takes place. Figure 2 illustrates this and shows two reactant streams (12), (14) operating at flow rates 1 and 2 respectively. Reactant stream 1 may comprise CH₃OH gas. Reactant streams (12) and (14) are combined and mixed in an ante chamber (5) of the reactor to form a single reactant stream which moves over the catalyst bed (6) where it is converted into a single product stream (8) comprising steam and C0₂ and passes through the outlet (10). The ante chamber may contain a mixing device to assist the mixing of the reactants.

Alternatively, again where the reactor has two or more inlets, the reactants may be mixed on the catalyst. In a further embodiment in which the reactor has two or more inlets, a first reactant may be contacted with a first catalyst, followed by mixing with a second reactant and then contacting the mixture with a second catalyst. For instance, an aqueous hydrogen peroxide solution may be contacted with a first catalyst, generating steam and 0₂, which are then mixed with a methanol spray or vapour before contact with a second catalyst. Thus, in some embodiments, the reactor comprises one inlet in front of the first catalyst and one inlet between the first catalyst and the second catalyst. Figure 3 illustrates this and shows inlet 1 (16) wherein the aqueous hydrogen peroxide is introduced and contacted with the first catalyst bed (18) generating steam and 0₂. Inlet 2 (20) can also be seen, which introduces methanol spray or vapour which is mixed with the steam and 0₂ (21) before contact with the second catalyst bed (22) where it is converted into a single product stream (8) comprising steam and C0₂ and passes through the outlet (10).

Steam generation catalyst

The steam generation catalyst may be a catalyst as described in WO 2009/013514 Al, which is incorporated herein in its entirety by reference. The steam generation catalyst may comprise active components such as precious metals and/or transition metals which may be Pt, Pd, Rh, Ir, Ru, Ni, Os, Re, Co, Fe, Mn, Cu, Ag, Au, or combinations thereof. The active component may be Pt used alone, or may comprise a combination of Pt and Pd. The active component(s) may be used in the reduced state. The active component(s) may be promoted by any main group metal, non-metal, transition metal, rare earth metal, or compounds and/or combinations thereof to increase the catalyst activity and/or stability. The catalyst may thus comprise a promoter that may be a transition metal, such as Ni or Co, or a rare earth metal, such as Ce. The promoter may be present as the native element, as a compound (e.g. an oxide) thereof, or as a mixture of both. As used herein, references to a given promoter (e.g. Ce) include the native element, compounds (e.g. Ce0₂) thereof and mixtures of both. In some embodiments, the promoter is Ce, which is capable of stabilising and enhancing the activity of Pt.

The steam generation catalyst may be supported. The support can be any stable, inert support, such as alumina, modified alumina, silica, a molecular sieve, such as zeolite Y, silicon carbide or any inert material composite. The support may be alumina, including γ-alumina, θ-alumina and a-alumina. The support may be modified using other compounds to increase its stability. Typical modifiers include rare earth metals and their compounds, or non-metal compounds, such as phosphate.

The steam generation catalyst may be prepared by wet impregnation, incipient wetness impregnation, ion-exchange, mechanical mixing and sol-gel methods.

The steam generation catalyst may be of one of the following formulae:

x%Pt-y%Ce/y-Al₂0₃

x%Pt/y-Al₂0₃

x%Pt-y%Pd/y-Al₂0₃

x%Pt-y%Pd/y-Al₂0₃-La₂0₃

x%Pt-y%Pd/[z%CZY- t%Al₂0₃-La₂0₃].

CZY stands for cerium-zirconia stabilised by yttria and having the composition a%Ce0₂-b%Zr0₂-c%Y₂0₃ (x and y are quoted in percent by weight of the total weight of the catalyst; a, b and c are quoted in percent by weight of CZY; and z and t are quoted in percent by weight of the catalyst support).

x and y may independently be a value from 0.001 to 10, from 0.1 to 8, from 0.1 to 5; or from 0.25 to 2; z may be a value from 30 to 70, or about 40; and t may be a value from 70 to 30, or about 60. z and t add up to 100. a may be a value from 1 to 60, or 20 to 60, or 30 to 60, or 40 to 60, or 40 to 50, or about 50; b may be a value from 1 to 60, or 20 to 60, or 30 to 60, or 40 to 60, or 40 to 50, or about 46; and c may be a value from 1 to 10, or 1 to 8, or 1 to 6, or about 4; wherein a, b and c add up to 100.

In some embodiments, Pd may be replaced by Au. The steam generation catalyst may be 3%Pt-l%Pd/[50%CZY-50% Al₂0₃-La₂0₃ doped] wherein CZY is 50%CeO₂-46%ZrO₂- 4%Y₂0₃. Alternatively, the steam generation catalyst may be 0.5%Pt-0.1%Ce/y-Al₂O₃, 1.5%Pt-0.7%Ce/y-Al₂O₃ or 3%Ρί-0.7%ϋε/γ-Α1₂Ο₃.

Pressure source

The pressure source may be capable of generating a pressure of greater than 0.1 MPa, or greater than 0.12 MPa, or greater than 0.2 MPa, or greater than 0.35 MPa, or greater than 0.5 MPa, or greater than 1.0 MPa, or greater than 1.5 MPa, or greater than 2.0 MPa within the reactor. The pressure source may also be capable of generating a pressure of up to 1.3MPa, or up to 2.0 MPa, or up to 5.5 MPa within the reactor. The pressure source may be capable of maintaining a substantially constant (i.e. deviates by less than ±10 %) pressure within the reactor. The generation of increased pressure within the reactor may allow alcohol conversion up to completion (100% conversion), even in the presence of a large amount of liquid water, and may allow steam generation (in particular saturated steam generation) from more dilute reactants than previously thought feasible, thus reducing the toxicity of the reactant solutions, increasing user safety and potentially avoiding restrictions on sales. In addition to reducing water inhibiting effects, the generation of increased pressure also raises the boiling point of water, thus enabling the catalyst to warm up above 100 °C and thereby further activating it.

In some embodiments, the pressure source comprises a pump in fluid communication with the inlet of the reactor. The pump may be mechanically or electrically actuated. For instance, the pump may be an HPLC pump. Alternatively, the pump may be a peristaltic pump. If mechanical, the pump may be manually (e.g. operated by a trigger). If electrical, the pump may be powered by battery, or by mains power supply (e.g. via an electric train track). The apparatus may comprise two or more pumps, e.g. if the reactor comprises two or more inlets.

In other embodiments, the pressure source comprises a compressed gas source, such as a gas cylinder, in fluid communication with the inlet of the reactor. The gas cylinder may contain an inert gas, such as nitrogen. The pressure source may be capable of feeding one or more reactants to the reactor at a flow rate of at least 0.1 ml/min, at least 1.0 ml/min, at least 5.0 ml/min, at least 20 ml/min, at least 50 ml/min or at least 200 ml/min. In some embodiments, the pressure source may feed the reactants to the reactor at a substantially even flow rate. A "substantially even flow rate", as used herein, refers to an instantaneous flow rate which is within ±10% of the average flow rate. In some embodiments, the pressure source may feed the reactants to the reactor at a flow rate that progressively increases following start up of the apparatus for producing steam up to a maximum flow rate. This may be achieved by use of a buffer reservoir or porous buffers between the reactant reservoir(s) and the reactor inlet, by use of an adjustable pressure source (e.g. a pump with several output settings) or by use of a plurality of pressure sources (with different output capabilities). The pressure source may be set to provide a flow rate increasing at a ramp of up to 0.1 ml/min², up to 1 ml/min², up to 10 ml/min², up to 100 ml/min², or up to 1000 ml/min². Progressive increase of the reactant flow rate may reduce emissions of compounds such as CH₃OH and HCHO during the initial operation of the apparatus for the production of steam and prolong the life of the catalyst.

Alternatively or additionally, the pressure source may comprise a valve or a back-pressure regulator in fluid communication with the outlet of the reactor. The valve or back-pressure regulator may be operable to control the pressure within the reactor, thus allowing the pressure in the reactor to be controlled by a mechanism downstream of it.

Reactants

The apparatus and methods of the invention may generate steam from two or more reactants. The reactants may comprise at least one peroxide and at least one alcohol. Although the invention will be described with reference to hydrogen peroxide and methanol, it will be appreciated that alternative peroxides and alcohols can be used.

For instance, the peroxide may be an inorganic peroxide or an organic peroxide. Examples of inorganic peroxides include hydrogen peroxide and metal peroxides. Metal peroxides include peroxides of alkali metals, such as lithium, sodium and potassium, and alkaline earth metals, such as magnesium, calcium and barium, e.g. sodium peroxide or barium peroxide. Organic peroxides include alkyl peroxides, such as t-butyl peroxide and cumyl peroxide. Benzoyl peroxide may also be used.

The alcohol may be a mono-alcohol or a polyol. Mono-alcohols include methanol, ethanol, propanol (including n-propanol or i-propanol), butanol and pentanol or a mixture thereof. Polyols include ethylene glycol and glycerols. The hydrogen peroxide and methanol may be used in pure form but are typically used in the form of a solution, such as an aqueous solution. The percentages of each component in solution are quoted in percent by weight of the total weight of the solution. The hydrogen peroxide solution may comprise less than 28 wt% hydrogen peroxide, less than 20 wt% hydrogen peroxide, or less than 16 wt% hydrogen peroxide. The methanol solution may comprise less than 8 wt% methanol, or less than 5 wt% methanol. In each case, the balance may be water.

In some embodiments, the present invention is capable of generating steam from reactant solutions that have a reactant concentration below a certain threshold. For instance, the threshold might be the upper concentration limit for the sale of the reactant solution to the general public, or the upper concentration limit for the sale of the reactant solution without a skull and crossbones marking on its packaging. Thus, the hydrogen peroxide solution may comprise less than 12 wt% hydrogen peroxide. Similarly, the methanol solution may comprise less than 4 wt% methanol. The reactant solution(s) may contain at least 50 wt% water to avoid entering a detonable range.

The molar ratio of hydrogen peroxide to methanol at the catalyst may be from 10:1 to 1 :10, from 4:1 to 1 :4, or from 3:1 to 1 :3. To maximise steam production, the molar ratio of hydrogen peroxide to methanol at the catalyst may be from 10:1 to 2:1, from 4:1 to 3:1 , or from 3.5:1 to 3: 1, or about 3.3:1.

Each reactant may be fed to the reactor as a liquid (e.g. as an aqueous solution), in the form of a spray (e.g. as fine droplets of an aqueous solution) or as a gas (e.g. as a vapour). The apparatus may therefore comprise equipment to generate a reactant spray or gas, such as a heat source.

Steam

The invention is capable of generating steam as the direct product of a chemical reaction (e.g. CH₃OH + 3H₂0₂→ C0₂ + 5H₂0) and/or by the boiling of water using heat generated in a chemical reaction. Steam generated in this way may be referred to as "chemical steam". The steam may be non-saturated steam, saturated steam or superheated steam, depending on the application for which it is being produced. In addition to steam, other gases and liquids may be produced in the invention. For instance, the product exiting the reactor may, in addition to steam, comprise C0 and, potentially, liquid water and/or 0₂, and various effluents, e.g. CH₄, CO, HCOH, HCOOH, HCOOCH₃, unconverted CH₃OH etc. It is preferable to keep the amount of effluents in the product to a minimum, i.e. it is preferable that all/substantially all of the methanol is converted to steam and C0₂. "Substantially all" as used herein means "greater than 95 wt%".

The steam produced may be released at a temperature of from 100 °C to 900 °C, or 150 °C to 700 °C, or 200 °C to 500 °C, or 300 °C to 400 °C. The steam produced may be released at a temperature of 100 °C to 300 °C. If the steam is superheated steam, the degree of superheating may be at least 10 °C, at least 25 °C, at least 50 °C, at least 100 °C, or at least 300 °C.

The steam produced in the invention may be used in a variety of applications. For instance, the steam may be used to power a model or full-sized train, plane, car, boat or rocket; to clean, decontaminate and/or degrease a surface; to strip and/or repair paint; to kill weeds; to generate electricity (e.g. by driving a turbine or a dynamo); or to generate remote mechanical energy (e.g. for drilling operations).

The invention therefore provides both industrial and domestic apparatus for the production of steam. The apparatus may be mobile (i.e. it can be moved either manually, for instance by a single user, or under its own power (e.g. by the generation of mechanical energy from steam, or by using steam as a propellant)) and may, in some embodiments, be hand-held.

Failsafe mechanism

The failsafe mechanism is designed to prevent an unsafe failure mode of an apparatus for the production of steam. It may be used as an indirect method of monitoring the efficacy of the steam generation catalyst heating, as discussed hereinbefore. In optimal conditions, all/substantially all of the methanol is converted to steam and C0₂. However, if the apparatus fails (e.g. the steam generation catalyst heating source fails), various effluents, such as CO, HCOH, HCOOH and other compounds containing a carbonyl group, and unconverted CH₃OH may be emitted from the apparatus. The failsafe mechanism may therefore be operable to automatically deactivate the pressure source, thus stopping the flow of reactants into the reactor, causing the steam generation reaction to cease and the emission of effluents to stop, thereby protecting the user of the apparatus.

In some embodiments, the failsafe mechanism may comprise a detector set to deactivate the pressure source upon detection of a compound at a concentration above a threshold concentration. Thus, the detector may be capable of detecting one or more of CO, compounds containing a carbonyl group (such as HCOH, HCOOH and HCOOCH₃) and CH₃OH. The threshold concentration may vary for different compounds, and may be set according to government guidelines in the country of sale of the apparatus. For instance, the threshold concentration (given in parts per million by volume (ppmv) of the product exiting the reactor) for HCOH may be < 1000 ppmv, < 500 ppmv, < 250 ppmv, < 100 ppmv, < 50 ppmv, < 10 ppmv, < 2.0 ppmv, < 0.5 ppmv, < 0.1 ppmv, < 0.05 ppmv or < 0.01 ppmv. The threshold concentration for HCOH may be 0.3 ppmv.

The threshold concentration for HCOOH may be < 200 ppmv, < 25 ppmv, < 2.0 ppmv, < 0.5 ppmv, < 0.1 ppmv, < 0.05 ppmv or < 0.01 ppmv. The threshold concentration for HCOOH may be 5.0 ppmv.

The threshold concentration for HCOOCH₃ may be < 1000 ppmv, < 250 ppmv, < 20 ppmv, < 5.0 ppmv, < 1.0 ppmv, < 0.5 ppmv or < 0.1 ppmv. The threshold concentration for HCOOCH₃ may be 50 ppmv.

The threshold concentration for CH₃OH may be < 5000 ppmv, < 1000 ppmv, < 250 ppmv, < 50 ppmv, < 10 ppmv, < 5 ppmv or < 1 ppmv. The threshold concentration for CH₃OH may be 200 ppmv.

The threshold concentration for CO may be < 1000 ppmv, < 100 ppmv, < 10 ppmv, < 2 ppmv, < 0.5 ppmv, < 0.1 ppmv or < 0.05 ppmv. The threshold concentration for CO may be 30 ppmv.

The detector may be located at any suitable position in the apparatus for the production of steam. In some embodiments, the detector may be in fluid communication with the outlet of the reactor. The detector used depends on the compounds to be detected. In some embodiments, the detector may comprise a laser diode and a photo detector for detecting compounds such as those containing a carbonyl group (e.g. HCOH and HCOOH). The laser diode may be set to emit light of a wavelength that will be absorbed by the compounds to be detected but not by other compounds in the product exiting the reactor. Thus, for compounds containing a carbonyl group, the laser diode may emit light at between 1665 cm^"1 and 1760 cm^"1, in particular at about 1750 cm^"1.

Alternatively or additionally, the failsafe mechanism may comprise a temperature sensor (e.g. a thermocouple) set to deactivate the pressure source upon detection of a steam temperature shift indicative of a drop of fuel conversion (e.g. a drop in steam temperature of at least 10 %) and/or a pressure sensor set to deactivate the pressure source upon detection of abnormal pressure variations (e.g. variations of at least 10%) in the apparatus, particularly the reactor. For instance, the above-described detector may be used together with a temperature sensor and set to deactivate the pressure source upon detection of a compound (e.g. methanol) at a concentration above a threshold concentration in conjunction with a temperature drop of, for example, at least 10%. In this way, if methanol is ejected during warm-up of the apparatus, triggering of the failsafe mechanism can be avoided. The detector/sensor(s) may be in communication with the pressure source (e.g. a pump in fluid communication with the inlet of the reactor) and, upon detection of a particular compound at a concentration above a threshold concentration, may deactivate the pressure source (e.g. shut the pump off).

A schematic of an apparatus for the production of steam that includes a failsafe mechanism comprising a chemical detector is shown in Figure 4. In Figure 4, the pressure source, gear pump (24), pumps the reactant stream into the reactor (26) where it is contacted with a steam generation catalyst (not shown) to produce a product stream (28) which may comprise HCOH and other carbonyl type unsafe effluents. The product stream passes between a photodetector (30) and a laser diode (32) which use a laser beam of 1750 cm^"1 to detect the levels of unsafe effluents in the product stream. If the photodetector and laser diode detect a certain level of one or more unsafe effluents, the electronic failsafe device (44) automatically deactivates the pressure source (24) preventing the reactant stream flowing into the reactor.

A schematic of an apparatus for the production of steam that includes a failsafe mechanism comprising a chemical detector (34), a temperature sensor (36) and a pressure sensor (38) is shown in Figure 5. Figure 5 shows a fuel tank (40) which comprises the reactants. The fuel tank may be made from high density polyethylene. The fuel tank has a vent (42) to prevent pressure build up during operation. The reactants pass through a check valve (43) and the pressure source, gear pump (24), pumps the reactant stream into the reactor (26) where it is contacted with a steam generation catalyst (not shown). The reactor (26) includes a pressure relief system (28). Each failsafe mechanism (the chemical detector (34), the temperature sensor (36) and the pressure sensor (38)) are connected to the electronic failsafe device (44) which can automatically deactivate the pressure source (24) on receipt of a critical reading from one of the failsafe mechanisms thereby preventing the reactant stream flowing into the reactor. Figure 5 also shows a monitoring device (25), which monitors the premixed fuel shelf life and the check valve to prevent gas or contaminants flowing back into the fuel tank from the reactor.

MODES FOR CARRYING OUT THE INVENTION

Fuel conversion using a PWR reactor

A fuel mixture of 1 1.5 wt% H₂0₂ / 3.28 wt% C¾OH / H₂0 85.2 wt% was passed over a 1.5%Pt-0.7%Ce/y-Al₂O₃ catalyst using the apparatus shown in Figure 6. The reaction was initiated from room temperature and operated in a steady state using a HPLC pump (46) set at a flow rate of 7 ml/min. The HPLC pump pumps fuel (47) through inlet pressure gauge Pi (48) and into the reactor (26) to contact the catalyst and be converted into the product stream (52). The product stream (52) passes through relief valve and pressure gauge P₂ (54) and past a thermocouple (56) to measure the temperature of the steam. The reactor pressure was set using a high temperature/pressure valve (58) located at the outlet of the reactor. The reactor pressure was varied up to 20 bar. Following condensation (60), the dry gases (62) were passed to a gas chromatography machine. The methanol conversion was monitored by gas chromatography (Varian GC-3800) via dry gas analysis (the liquid products being condensed). The methanol conversion into C0₂ was observed to increase steadily up to reaction completion (99% conversion) as the pressure increased up to 18 bar (see the uppermost line in Figure 7). Figure 7 also shows the displacement of the boiling point of water as a function of pressure from thermodynamics database (dark diamonds starting from origin). Figure 7 also shows the experimentally measured steam temperature as a function of pressure (light diamonds).

Model steam train

Apparatus of the invention (1.0 to 3.0g 3%Pt-0.7%Ce y-Al₂O3 catalyst; air gap reactor with internal dimensions of 3/8" diameter x 5 to 8 cm and an external envelope of 3/4" diameter (and length adjusted accordingly)) were fitted to a model steam train along with a steam/piston engine in place of an electric motor and boiler. The pump, powered by an electric train track, fed fuel (13.5 wt% hydrogen peroxide / 3.85 wt% methanol for a steam temperature of 100 °C (non-saturated), 25.0 wt% hydrogen peroxide / 7.14 wt% methanol for a steam temperature of 130 °C; 28.0 wt% hydrogen peroxide / 8.0 wt% methanol for a steam temperature of 260 °C (superheated) - balance = water in each case) into the reactor at a rate up to 20 ml/min, generating steam sufficient to power the steam/piston engine to produce a movement of the train. The train could be stopped and started and the speed controlled at will, and completed several circuits of the test track before the fuel ran out. Cumulative methanol emissions (measured by GC - Varian GC-3800) were below 2% of the safety limits (200 ppmv methanol for a 20 m³ room, 1 atm, 25 °C) given a reactor pressure of 2.5 bar, 2.5 g of catalyst and a 3/8" diameter x 8 cm reactor. Preheated catalyst

Experiments:

(1) No preheating

(2) 300 °C and 500 °C preheating (5 min prior start + 2 min after start)

The temperature in the middle of the catalyst bed and the steam temperature at the outlet were monitored. The following conditions and equipment were used:

• 3g benchmark catalyst 0.5 %Pt-0.1 % Ce / γ-Α1₂0₃

• 3g SiC 97% passivated (SiC/catalyst: 1/1 w/w)

• Reactor L/D = 20 with L = 17 cm and D = 3/8"

· Fuel 28.0 wt% Nanopure® (Evonik) hydrogen peroxide / 8 wt% methanol / 64 wt% water

• Fuel flow rate 30 ml/min

• 15 minutes run

Preheating (300 °C and 500 °C) was applied externally on the last 6.5 cm of the bottom of the reactor (to avoid preheating the feed for safety reasons) and insulated.

Liquid effluents were collected every minute (averaged values over 1 min - wet gas composition equivalent) and injected into a GC (Varian GC-450) calibrated against CH₃OH, CO, HCHO, HCOOH, and HCOOCH₃.

According to the calibration curves, the GC-450 detection limits have been established (wet gas composition equivalent) as:

1 ppmv for CH₃OH

500 ppmv for HCOH

5000 ppmv HCOOH

1 ppmv for HCOOCH₃

1 ppmv for CO

(1) No preheating

GC manual injections were carried out over 4 days and repeated twice at least for the first 4 minutes run. The results were compared to manual injections of standard solutions of 5 wt% CH₃OH/H₂0, 1000 ppmw (parts per million by weight) HCHO and 5000 ppmw HCHO to help identification. The results are shown in Figure 8.

• 1.35 wt% (13500ppmw) of CH₃OH was detected initially (dark blue line - full blue diamond symbol), which then decreased dramatically when the steam temperature passed the vaporisation barrier 100 °C. From the second minute, extremely low levels were detected.

• No HCOOH was detected, probably because of the high detection limit.

• HCOOCH₃ detection (sky blue line - no symbols) was very low in the condensate (below 50 ppmw).

• HCOH was detected (red curve - full red triangle symbol) up to 2000 ppmw (repeatable injection the second day) at 4 minutes, the first 5 minutes showing also a baseline.

Also shown in Figure 8 are:

• The catalyst bed temperature (green empty circles);

• The steam temperature at the outlet of the reactor (full green circles);

• The predictive model quantification of methanol in effluents (empty blue triangles); and

• The TCD GC response to the presence of an unknown compound in the effluents (violet cross).

An unknown compound was detected, and the peak associated with it on the chromatogram grew with time, showing the condensates were not stable over time. A repeat of the injection of the 4 minute sample on the third day showed a disappearance of the HCHO peak but a reinforcement of this unknown peak, suggesting a reaction between the unknown compound and HCHO in the condensate. The unknown peak may also be the result of an increasing concentration of residual organics left in the column run after run (accumulation process).

2) 300 °C and 500 °C preheating applied at the bottom of the catalyst bed (5 min prior to start and 2 min after start)

GC manual injections were carried out over the same day and repeated twice at least for the first 4 minutes run. The results were compared to manual injection of standard solutions of 5 wt% CH₃OH/H₂O, 1000 ppmw HCHO and 5000 ppmw HCHO to help identification. For one experiment, only the first 6 minutes of the run were analysed. The results are shown in Figure 9 and Figure 10.

• Using 300 °C preheating, 1500 ppmw of CH₃OH was detected (dark blue line - full blue diamond symbol) at the start and decreased dramatically when the steam temperature passed above the vaporisation barrier 100 °C (2 minutes run). Using 500 °C preheating, the CH₃OH disappeared almost completely (few ppmw left) at the start.

• No HCOOH was detected, probably because of the high detection limit, but it is also believed that preheating at 500 °C destroys it completely.

· HCOOCH₃ detection (sky blue line - no symbols) was very low in the condensate (below 5 ppmw) in each case.

• Using 300 °C preheating, HCOH was detected (red curve - full red triangle symbol) up to 600 ppmw at 4 min. Using 500 °C preheating, HCHO was below the detection limit (the baseline also showed a very low noise).

Also shown in Figure 9 and Figure 10 are:

• The catalyst bed temperature (green empty circles);

• The steam temperature at the outlet of the reactor (full green circles);

• Preheater coil temperature around reactor (red empty circles);

The unknown compound appeared once in large amounts during the run preheated at 300 °C but disappeared almost completely during the run preheated at 500 °C used in combination with GC column wash with water.

Thus, preheating the bottom of the catalyst bed at 500 °C suppressed CH₃OH slippage completely, reduced HCOOCH₃ emission and brought HCHO emission below the detection limits.

It will be understood that the invention has been described by way of example only and modifications may be made whilst remaining within the scope and spirit of the invention.

Aspects of the present invention

Aspect 1. An apparatus for the production of steam, comprising: a reactor comprising an inlet and an outlet; a steam generation catalyst positioned within the reactor; and a pressure source capable of generating a pressure of greater than 0.1 MPa within the reactor.

Aspect 2. The apparatus according to aspect 1, wherein the pressure source is capable of generating a pressure of greater than 0.5 MPa within the reactor. Aspect 3. The apparatus according to aspect 2, wherein the pressure source is capable of generating a pressure of greater than 1.0 MPa within the reactor.

Aspect 4. The apparatus according to any one of aspects 1-3, wherein the pressure source comprises a pump in fluid communication with the inlet of the reactor.

Aspect 5. The apparatus according to aspect 4, wherein the pressure source is operable to feed reactants to the reactor at a flow rate that progressively increases following start up of the apparatus.

Aspect 6. The apparatus according to any one of aspects 1-5, wherein the pressure source comprises a valve or back-pressure regulator in fluid communication with the outlet of the reactor.

Aspect 7. The apparatus according to any one of aspects 1-6, wherein the reactor is a pressurised water reactor.

Aspect 8. The apparatus according to any one of aspects 1-7, wherein the apparatus further comprises a reservoir in fluid communication with the inlet of the reactor.

Aspect 9. The apparatus according to aspect 8, wherein the reservoir contains a peroxide and/or an alcohol.

Aspect 10. A method for generating steam, comprising contacting a peroxide solution and an alcohol solution in the presence of a steam generation catalyst, wherein the peroxide solution comprises less than 12 wt% peroxide and the alcohol solution comprises less than 4 wt% alcohol.

Aspect 1 1. An apparatus for the production of steam, comprising: a reactor comprising an inlet and an outlet; a steam generation catalyst positioned within the reactor; a pressure source; and a failsafe mechanism operable to automatically deactivate the pressure source. Aspect 12. The apparatus according to aspect 11, wherein the failsafe mechanism comprises a detector set to deactivate the pressure source upon detection of a compound at a concentration above a threshold concentration.

Aspect 13. The apparatus according to aspect 12, wherein the detector is in fluid communication with the outlet of the reactor.

Aspect 14. The apparatus according to either aspect 12 or aspect 13, wherein the detector is capable of detecting one or more of CO, compounds containing a carbonyl group and CH₃OH. Aspect 15. The apparatus according to any one of aspects 12 to 14, wherein the detector comprises a laser diode and a photo detector.

Aspect 16. The apparatus according to aspect 15, wherein the laser diode emits light at between 1665 cm^"1 and 1760 cm^"1.

Aspect 17. The apparatus according to aspect 16, wherein the laser diode emits light at about 1750 cm^"1.

Aspect 18. The apparatus according to any one of aspects 1 1 to 17, wherein the failsafe mechanism comprises a temperature sensor set to deactivate the pressure source upon detection of a steam temperature shift indicative of a drop of fuel conversion.

Aspect 19. The apparatus according to any one of aspects 1 1 to 18, wherein the failsafe mechanism comprises a pressure sensor set to deactivate the pressure source upon detection of abnormal pressure variations in the apparatus.

Aspect 20. An apparatus for the production of steam, comprising a reactor comprising a first inlet and an outlet; a first steam generation catalyst positioned within the reactor; and a heat source that may act on the first steam generation catalyst.

Aspect 21. The apparatus according to aspect 20, wherein the heat source is an electrical heater.

Aspect 22. The apparatus according to either aspect 20 or aspect 21, wherein the heat source is capable of preheating the first steam generation catalyst up to 500 °C.

Aspect 23. A method for generating steam, comprising feeding a peroxide and an alcohol into the inlet of an apparatus according to any one of aspects 1 to 9 or 1 1 to 22.

Aspect 24. The method according to aspect 23, wherein the peroxide is present in an aqueous peroxide solution that comprises less than 28 wt% peroxide; and the alcohol is present in an aqueous alcohol solution that comprises less than 8 wt% alcohol.

Aspect 25. The method according to aspect 24, wherein the peroxide solution comprises less than 12 wt% peroxide.

Aspect 26. The method according to either aspect 24 or aspect 25, wherein the alcohol solution comprises less than 4 wt% alcohol.

Aspect 27. The method according to any one of aspects 23 to 26, wherein the pressure within the reactor is greater than 0.1 MPa. Aspect 28. The method according to aspect 27, wherein the pressure within the reactor is greater than 0.5 MPa.

Aspect 29. The method according to aspect 28, wherein the pressure within the reactor is greater than 1.0 MPa.

Aspect 30. The method according to any one of aspects 10 or 23 to 29, wherein the peroxide is hydrogen peroxide.

Aspect 31. The method according to any one of aspects 10 or 23 to 30, wherein the alcohol is methanol.

Aspect 32. An apparatus for the production of steam, comprising a reactor comprising a first inlet, a second inlet and an outlet; a first steam generation catalyst positioned within the reactor between the first inlet and the second inlet; and a second steam generation catalyst positioned within the reactor between the second inlet and the outlet.

Aspect 33. A method for generating steam, comprising feeding a feeding a first reactant to the first inlet of the apparatus according to aspect 32 and a second reactant to the second inlet of the apparatus according to aspect 32, wherein one of the first reactant and the second reactant is a peroxide and the other is an alcohol.

Aspect 34. The method according to aspect 33, wherein the first reactant is hydrogen peroxide and the second reactant is methanol.

Aspect 35. The method according to any one of aspects 10, 23 to 31, 33 or 34, wherein the flow rate of the reactants progressively increases following start up of the apparatus.

Aspect 36. A vehicle; a model vehicle; a cleaning, decontamination or degreasing device; a paint stripper or repairer; a weed killer; an electricity generator or a source of remote mechanical energy comprising the apparatus according to any one of aspects 1 to 9, 11 to 22 or 32.

Claims

1. An apparatus for the production of steam, comprising

a reactor comprising a first inlet and an outlet;

a first steam generation catalyst positioned within the reactor; and

a heat source that acts on the first steam generation catalyst.

2. The apparatus of claim 1, wherein the heat source is in thermal communication with the first steam generation catalyst.

3. The apparatus according to claim 1 or claim 2, wherein the heat source is an electrical heater.

4. The apparatus according to any preceding claim, wherein the heat source is capable of heating the first steam generation catalyst up to 500 °C.

5. The apparatus according to any preceding claim, wherein the heat source is capable of preheating the first steam generation catalyst up to 500 °C.

6. An apparatus according to any preceding claim, comprising:

a pressure source which, when in operation, causes reactants to flow into the reactor; and

a failsafe mechanism operable to automatically deactivate the pressure source.

7. The apparatus according to claim 6, wherein the failsafe mechanism comprises a detector set to deactivate the pressure source upon detection of a compound at a concentration above a threshold concentration.

8. The apparatus according to claim 7, wherein the detector is in fluid communication with the outlet of the reactor.

9. The apparatus according to either claim 7 or claim 8, wherein the detector is capable of detecting one or more of CO, compounds containing a carbonyl group and CH₃OH.

10. The apparatus according to any one of claims 7 to 9, wherein the detector comprises a laser diode and a photo detector.

11. The apparatus according to claim 10, wherein the laser diode emits light at between 1665 cm^"1 and 1760 cm^"1. The apparatus according to claim 1 1, wherein the laser diode emits light at about 1750 cm^"1.

The apparatus according to any one of claims 6 to 12, wherein the failsafe mechanism comprises a temperature sensor set to deactivate the pressure source upon detection of a steam temperature shift indicative of a drop of fuel conversion.

The apparatus according to any one of claims 6 to 13, wherein the failsafe mechanism comprises a pressure sensor set to deactivate the pressure source upon detection of abnormal pressure variations in the apparatus.

A method for generating a product stream comprising steam, said method comprising feeding a peroxide and an alcohol into the inlet of an apparatus according to any one of the preceding claims.

The method according to claim 15, wherein

the peroxide is present in an aqueous peroxide solution that comprises less than 28 wt% peroxide; and

the alcohol is present in an aqueous alcohol solution that comprises less than 8 wt% alcohol.

The method according to claim 15 or claim 16, wherein the peroxide solution comprises less than 12 wt% peroxide.

The method according to any of claims 15 to 17, wherein the alcohol solution comprises less than 4 wt% alcohol.

The method according to any one of claims 15 to 18, wherein the pressure within the reactor is greater than 0.1 MPa.

The method according to claim 19, wherein the pressure within the reactor is greater than 0.5 MPa.

The method according to claim 20, wherein the pressure within the reactor is greater than 1.0 MPa.

The method according to any one of claims 15 to 21, wherein the peroxide is hydrogen peroxide.

The method according to any one of claims 15 to 22, wherein the alcohol is methanol. The method according to any one of claims 15 to 23, wherein the flow rate of the reactants progressively increases following start up of the apparatus.

The method according to any one of claims 15 to 24, wherein the product stream comprises less than 1000 ppmv of CO.

The method according to any one of claims 15 to 25, wherein the product stream comprises less than 1000 ppmv of HCOH.

The method according to any one of claims 15 to 26, wherein the product stream comprises less than 200 ppmv of HCOOH.

The method according to any one of claims 15 to 27, wherein the product stream comprises less than 1000 ppmv of HCOOCH₃.

The method according to any one of claims 15 to 28, wherein the product stream comprises less than 5000 ppmv of CH₃OH.

A vehicle; a model vehicle; a cleaning, decontamination or degreasing device; a paint stripper or repairer; a weed killer; an electricity generator or a source of remote mechanical energy comprising the apparatus according to any one of claims 1 to 14.