RO128151B1 - Process for burning the mixture of hydrogen and carbon dioxide and installation for using the same - Google Patents

Abstract

The invention relates to a process and an installation for obtaining thermal energy by the combustion of hydrogen in admixture with carbon oxides, nitrogen oxides and/or sulphur oxides in the presence of a magnesium catalyst which is a mixture of magnesium chips and powder. The process for obtaining the thermal energy according to the invention consists of a first stage wherein the combustion of hydrogen in admixture with carbon oxides, nitrogen oxides and/or sulphur oxides in the presence of the magnesium catalyst is performed in an enclosure with orifices for discharging the gases and the carbon and/ or sulphur atoms, with the formation of Mg0 and water and a second stage wherein magnesium is regenerated in the same enclosure by introducing extra hydrogen.

Description

The invention relates to a process for combustion of the mixture of hydrogen with carbon dioxide, and to a plant for its implementation.

There is a known process of combustion of hydrogen and a catalytic burner of hydrogen that operates at low temperatures without flame, according to document WO2006 / 136316 A1, in which two catalysts are used, Pd (palladium) and Pt (platinum), the first of these being for initiating the oxidation of hydrogen in the air flow at ambient temperature, which is followed by other catalysts located in a downstream combustion chamber, to further support the oxidation. To prevent clogging of the catalyst pores, the air used is purified and supplied by a compressor. The burner is designed to provide a source of heat to residential hot water or district heating systems.

A hydrogen combustion process and a catalytic hydrogen burner operating at low temperatures are known, according to WO 2005/024301 A1. Hydrogen is mixed with air and burned in a combustion chamber on a catalyst (palladium or platinum), at a low temperature, without flame. The combustion chamber is surrounded by a heat exchanger through the flue gases, the heat released by the combustion being taken over by a cooling water circuit.

Global warming caused by increasing concentrations of greenhouse gases in the atmosphere is a major concern related to air quality. Carbon dioxide is the most abundant greenhouse gas emitted by burning fossil fuels used for heating, electricity generation and transportation, being responsible for most of climate change. Reducing _CO2 emissions requires measures such as reducing energy consumption, increasing energy efficiency and using alternative energy sources, renewable.

One of the major alternatives of fossil fuel energy is hydrogen energy. The object of high specific uses in the chemical, electronic and space industries, hydrogen has attracted the interest of public authorities and research organizations, as well as of business people, for more than three decades, and in quality. of clean fuel for the means of transport or as a source for generating electricity. Wide multidisciplinary research and development activities have been initiated and carried out with priority throughout the world, aiming at developing efficient technologies for generating, separating, purifying, storing, transporting and using in safe conditions of hydrogen.

Hydrogen is the cleanest fuel from the environmental point of view (by its combustion resulting only to water) and, at the same time, the most efficient energy carrier, having an energy content per unit of weight 2.1 times higher than for gases. natural. Hydrogen is also the most versatile renewable energy resource, which can be used anywhere in the world, independent of traditional energy resources, as a fuel for engines of all types of vehicles, as well as for thermal installations that serve a very wide range of uses (housing, buildings). , localities, etc.), as well as for fuel cells that produce electricity without pollution, having a wide variety of applications, including in electronics, telecommunications, computing technique.

An important technical problem to be solved for the use of hydrogen as a fuel is that of the burner. The combustion rate of pure hydrogen is very high, being in the range 265 ... 325 cm / s, compared to 37 ... 45 cm / s in the case of methane. For this reason, under normal conditions, hydrogen cannot support a flame. It is necessary to reduce the combustion rate of hydrogen at the same time as reducing the risk of explosion.

RO 128151 Β1

The temperature of the flame and its propagation speed are dependent on the composition of the combustion mixture, which increases the size of the flame, and decreases its speed. Depending on the concrete requirements imposed by a particular use, the composition of the combustion mixture must be carefully optimized. The burning of hydrogen usually involves more frequent maintenance work of the burners, since the rapid combustion often makes possible the contact of the flame with the components of the burner, leading to their rapid degradation. 7

At the global level, solutions have been conceived and implemented regarding the adaptation of thermoelectric power stations operating on fossil fuels to hydrogen operation. Since 1993, 9 in a demonstration project, carried out in Germany by SWB, the operation of boilers with a thermal capacity of 20 KW has been tested, using modified burners 11 for the combustion of hydrogen, natural gas or mixtures of these gases ( International Journal of Hydrogen Energy, vol. 19, no. 10, 1994). In Japan, 13 new Rankine cycles have been developed for power plants that use hydrogen as fuel (International Journal of Exergy, vol. 1, no. 1, pp. 29-46, 2004). 15

Improperly designed hydrogen burners vibrate and make noise. More important is the fact that in such burners improperly designed the flame can be 17 very unstable and can be detached from the burner. Some burner producers limit the hydrogen concentration to 90 ... 95%, the difference being methane. Outstanding 19 world-class results obtained by the US company Coen, California. The design and commissioning of some 250,000 Ib / h (113.5 t / h) boilers have been reported, 21 using 95% hydrogen fuel with Coen burners, as well as the fact that this company can produce 100% burning burners. hydrogen in steam boilers of type 23 Rentech or Babcock & Wilcox.

Taiwanese company De Fu Technology currently produces 25 "hydrogen-oxygen burners with a maximum thermal capacity of 250,000 kcal / h for boilers. furnaces for heat treatment and other applications (www.dfb.com.tw). 27

In order to burn hydrogen safely, it is essential to maintain a minimum combustion rate at the level of hydrogen injectors, so that conventional flow and pressure control devices are not sufficient. The American company CB NATCOM has designed (for the Olin Chior Chemicals chemical plant) a burner that uses multiple zones of 31 hydrogen injection (surplus product of the plant, available at a pressure of 0.48 bar), which opens and closes so that to maintain the pressure within optimum limits (intended for 33 aquatubular boilers with a capacity of 34 t / h, and operating at pressures of the order of 10 bar).

A system with 6 such zones provides a 20: 1 adjustment ratio. The control system 35 developed allows the safe and efficient operation in five modes of combustion: only natural gas, only fuel, only hydrogen, hydrogen with natural gas and hydrogen with fuel. To reduce the formation of nitrogen oxides, the immediate contact of the fuel with the air is avoided by steam injection at the periphery of the hydrogen injectors. Also to avoid the formation of nitrogen oxides 39, the operating temperature should be kept below 650 ° C. At the mentioned chemical plant, the project of installing two steam boilers using surplus hydrogen 41 and, if necessary (the availability of hydrogen as surplus product is not constant), the natural gas or fuel oil required a period of 14 months to complete. The benefits, in 43 year-on-year increases, due to price increases and fuels, were estimated at $ 2.5 million annually. 45 in August 2008, a similar system for the use of surplus hydrogen for the fuel supply of some steam boilers was put into operation and at the 47 Runcorn plant (northwest of England) of INEOS Chior, a global leader in the production of chlorinated derivatives (http://www.chemicalprocessing.com/articles/2010/132.html). 49

RO 128151 Β1 in document WO 2009/068424 A1 there is a transition sector coupled upstream with the vortex generator, and a mixing sector coupled upstream with the transition sector and downstream with the combustion chamber.

WO 2007/021053 A1 presents a burner for hydrogen gas, and a heat supply system that uses this burner. Hydrogen is generated in situ in an electrolytic cell, by electrolysis of an aqueous solution, and is filtered before use. It is also possible to temporarily store the electrolytic hydrogen product in a metal alloy, for later use in the burner. An efficient heat dissipation is ensured, preventing the overheating of the hydrogen feed nozzle. The burner according to this invention can be used in a domestic cooking installation.

WO 2006/136316 A1 presents a catalytic hydrogen burner, operating in safe conditions at low temperatures (around 300 ° C), without flame. A first catalyst for initiating hydrogen oxidation in air flow at ambient temperature is followed by other catalysts located downstream in the combustion chamber, to further support oxidation. To prevent clogging of the catalyst pores, the air used is purified and supplied by a compressor. The burner is designed to provide a heat source for residential hot water and / or heating systems.

WO 20067058843 A1 discloses a method and a device for burning a gas fuel that contains hydrogen or consists of hydrogen. The burner is provided with a whirlpool generator, the gas fuel being introduced axially and / or coaxially into it. The combustion air flow is introduced tangentially and is rotating.

In WO 2005/024301 A1 hydrogen is mixed with air and burned in a combustion chamber on a catalyst (for example: palladium, platinum), at a low temperature (200 ... 450 ° C), without flame. Hydrogen is supplied at a low pressure, preferably 20 millibars. The combustion chamber is surrounded by a heat exchanger through the flue gases, the heat released by the combustion being taken over by a cooling water circuit. The heated water can be stored in a tank, and used as needed. Hydrogen can be produced in situ by electrolysis, or it can be taken from storage cylinders after a pressure reduction. The patented burner is designed for equipping a hot water supply system for some buildings. When no hot water is needed, hydrogen can be accumulated in metal hydrides and stored.

The objective technical problem that the invention solves is to maintain the minimum fuel burn rate at the level of hydrogen injectors.

The solution to this problem, proposed by the process of combustion of the hydrogen gas mixture with carbon dioxide, consists in the use of magnesium as a catalyst to achieve the combustion of hydrogen from the H ₂ -CO ₂ mixture, using two moles of hydrogen for at most one. mol of carbon dioxide.

The solution to this problem, proposed by the combustion plant of the hydrogen-carbon dioxide mixture, consists in the use of a housing provided with a hydrogen inlet pipe, inside which is a uniform hydrogen distribution chamber, a distribution chamber. uniform carbon dioxide, and a chamber for the catalyst, provided with a deflector for homogenization of the gas mixture.

The process of combustion of the H ₂ -CO ₂ mixture, according to the invention, eliminates the aforementioned disadvantages by the fact that, in a first phase, the combustion of hydrogen in the mixture (H ₂ -CO ₂ ) is carried out in the presence of magnesium in a chamber with holes. for the evacuation of gases and carbon atoms, as a catalyst, with MgO formation, and in the second phase, in the same chamber where the hydrogen was burned according to the first phase, the added hydrogen addition allows the magnesium to regenerate. All this is carried out according to the following phase reactions:

RO 128151 Β1

H ₂ + CO ₂ + Mg -> MgO + C + H ₂ O 1

MgO + H ₂ Mg + H ₂ O + Q and the general balance sheet reaction:

2H ₂ + CO _{2 —} catalyst M _g ) —q ₊ 2H ₂ O + Q, the cycle being continuous.

The plant for combustion of the H ₂ -CO ₂ mixture, according to the invention, eliminates the disadvantages of the above-mentioned inventions by the fact that it is formed of a stainless steel housing (9 stainless steel pipe), on which a lid connected to a hydrogen supply pipe is fixed. , inside the housing being included: 11

- a uniform hydrogen distribution chamber, delimited by two caps, both of stainless steel sheet; 13

- a uniform distribution chamber of carbon dioxide, bounded by two caps of stainless steel sheet; 15

- a mixing chamber H ₂ -CO ₂ , delimited by a lid made of stainless steel, and containing quartz sand or quartz in the form of hexagonal crystals; 17

- a chamber for the catalyst, inside which is a magnesium catalyst both in the form of chips and in the form of powder; 19

- some copper pipes that ensure the uniform transport and distribution of H ₂ gases and

CO ₂ on the surface of the quartz and that of the catalyst; 21

- a deflector for mixing gas mixture, which ensures a mixing of the mixture

H ₂ -CO ₂ . 23 before entering the quartz layer, on the outside of the housing are provided:

- a pipeline to complement the catalyst; 25

- a supply line with H ₂ and a supply line with CO ₂ ;

- hot air directing plant for industrial applications. 27

The process of combustion of the mixture of hydrogen with carbon dioxide, and the installation thereof, according to the invention, has the following advantages:

- promotes, raises awareness and takes responsibility for the new generation regarding the role and importance of energy in the domestic and industrial applications of hydrogen, the transition to a new era based on hydrogen energy, an inexhaustible source;

- the system allows the burning of H ₂ and CO ₂ both at low and medium pressure; 33

- reducing the pollution effect of the environment by recovering carbon atoms;

- obtaining high purity carbon, which can be used in various fields; 35

- controlling the burning speed of hydrogen, as well as the desired temperature, with numerous applications in the industrial field; 37

- providing a well-controlled combustion atmosphere, which allows its use in industrial thermal treatments; 39

- the higher utilization of the hydrogen surplus of the chemical compounds and the units of profile, in order to obtain caloric energy or electricity; use of a relatively inexpensive catalyst (Mg), which provides a transfer of O ₂ from CO ₂ to H ₂ based on simple reactions, using at most 2 moles of H ₂ at most one mole of CO ₂ ; 43

- relatively simple construction;

- safety in exploitation; 45

- high reliability;

- the process allows the monitoring of the combustion temperature and the atmosphere by regulating the hydrogen burning rate 47.

RO 128151 Β1

Two examples of embodiments of the invention are given below, in connection with FIG. 1 ... 6, which represents:

FIG. 1, the combustion plant of the mixture H ₂ -CO ₂ ;

FIG. 2, the cross-section of the combustion plant of the H ₂ -CO ₂ mixture;

FIG. 3, detail B, catalyst chamber fixation;

FIG. 4, detail C, deflector mounting;

FIG. 5, deflector shape;

FIG. 6, variants for directing air heat provided by a fan for industrial applications.

The process of combustion of the hydrogen-carbon dioxide mixture according to the invention comprises, in the first phase, the combustion of hydrogen from the H ₂ -CO ₂ mixture in the presence of magnesium, in a chamber with holes for the discharge of gases and carbon atoms. catalyst, with MgO formation, and in the second phase, in the same chamber, the hydrogen addition introduced regenerates magnesium, according to the phase reactions:

H ₂ + CO ₂ + Mg -> MgO + C + H ₂ O

MgO + H ₂ Mg + H ₂ O + Q and the general balance sheet reaction:

2H ₂ + CO ₂ - ^{catalyst (} . ^M sl — q + 2H ₂ O + Q, the cycle being continuous.

From the chemical balance of the reaction it can be observed that two moles of hydrogen are used for one mole of carbon dioxide. Quantitatively, about 2400 Nm ³ H2 / h and 1200 Nm ³ CO2 / h, ie 2 moles H ₂ / max 1 mol CO ₂ , for which the volume of the cylindrical chamber with Mg was D300x30 (about 5.7 kg Mg ).

The combustion takes place on the surface of the chips magnesium layer, the place where the combination of hydrogen and oxygen is produced, and the release of the carbon atom. Magnesium has a tendency to oxidize, but it is regenerated by hydrogen by yielding oxygen to the hydrogen atom. Both the magnesium oxidation reaction and the hydrogen oxidation are highly exothermic reactions, which lead to a higher energy balance in relation to the energy loss required for decomposition of carbon dioxide. The catalyst and CO ₂ flow rate decrease the PL burning rate, and the quartz layer ensures homogenization of the H ₂ -CO ₂ mixture and interrupts the flame when the hydrogen supply is switched off (it does not allow it to propagate in the H ₂ feed circuit).

The combustion process of the H ₂ -CO ₂ - domestic mixture is carried out sequentially as follows:

- open the valve of the pipe with H ₂ at minimum flow;

- a piezoelectric system ignites hydrogen;

- the flow of hydrogen is increased;

- open the valve of the pipe with CO ₂ until the optimum molar ratio is ensured. At the stop, the operations are the opposite of the ones from the start.

The process of combustion of the H ₂ -CO ₂ - industrial mixture is carried out sequentially as follows:

- a methane flame is brought on by a piezoelectric system, brought through a supply line, the wake flame being directed perpendicular to the axis of the hydrogen burner;

- the hydrogen supply tap is progressively opened to the maximum flow rate;

- the feed valve with CO ₂ is progressively opened until the molar ratio H ₂ / CO _{2 is} equal to 2 / maximum 1.

RO 128151 Β1

The shutdown operation of the installation is the reverse of the start operation, namely: 1 CO ₂ stop, H ₂ stop, flame wake with methane. The industrial installations will also be provided with two optical sensors for the wake-up flame and for the flame of the mixture of H ₂ with CO ₂ 3, which is included in a special automation scheme, but which is not subject to the present invention.

The blown air with a fan is directed into a room that allows the cooling of the system, fig. 5 1, then the heated air is swirled through a truncated space inside the boiler furnace. The casing for directing the hot air into the boiler is provided with a circuit containing 7 copper pipe filling, which ensures the transfer of heat to the ventilated air.

The installation, both for the variant used in the domestic and industrial fields, as 9 can be seen in fig. 1, according to the invention, is composed of a housing 1 made of stainless steel, and a stainless steel pipe on which a lid 3 is connected connected to a supply line with 11 hydrogen 2. Inside the housing 1 is a distribution chamber hydrogen uniform M1, bounded by a cover 3 and a cover 5, both of stainless steel plate, connected to 13 a uniform distribution chamber of carbon dioxide M2, bounded by the cover 5 and a cover 6, also of sheet stainless steel. Also inside the housing 1 is a room M3 of homogenization mixture H ₂ -CO ₂ , delimited by a lid 9 of stainless steel plate, and inner screen 14, homogenization being realized with the help of a deflector 16, made of sheet of stainless steel, such as 17 and quartz sand or quartz crystals with granulation 0.8 ... 2 mm, and a chamber for catalyst 14, of stainless steel screen with perforations of 50 pm, inside which is a catalyst of 19 magnesium 13 both in the form of chips and in the form of powder.

The installation comprises some copper or stainless steel pipes 8, which ensure the transport and 21 the uniform distribution of H ₂ and CO ₂ gases on the surface of the catalyst 13, and a deflector 16 which ensures a turbulence of H ₂ and CO ₂ through the quartz start 18. 2. 3

Outside of housing 1, there is provided a catalytic supplement line 17, a supply line with H ₂ 2 and a supply line with CO ₂ 4. 25

The arrangement of pipes 7 and 8 inside the housing 1 can be seen in fig. 2.

The fixing of the chamber for the catalyst 14 with the element Mg which acts as a catalyst 27 can be seen from FIG. 3, this being achieved with a nut 11, a gasket 12 and an elastic element 15. 29 at the bottom of the chamber for the catalyst is technologically executed an inclination of 15 ° on its height, so that the carbon remaining in the catalyst can be recovered 31 through a pipe 10.

The fixing and the shape of the baffle 16 are shown in FIG. 4, respectively, FIG. 5. The stainless steel bolt 33 19 has a tightening adjustment for fixing in the CO ₂ distribution pipe, and is provided with some holes to allow the entry of CO ₂ into the mixing chamber. 35

The Mg catalyst is in the form of chips and inside the enclosure with Mg powder. Mass ratio Mg shavings / Mg powder = 5/1 ... 4/1. 37

From chamber M1, the hydrogen is evenly distributed through the pipes 7 beaded or welded on the covers 5, 6 and 9, to achieve a seal of the chambers. 39

Through pipe 8 it is evenly distributed and CO ₂ . It is fixed to the covers 6 and 9 by boring or welding, depending on the material used (copper or stainless steel). Following the combustion process, catalyst 13, which ensures the transfer of oxygen from carbon dioxide (CO ₂ ) to hydrogen (H ₂ ), may also have some losses which require periodically the completion of the 43 room in which it is destined, which is made by the pipe 17.

For industrial applications, it is also necessary to direct the flame and the heat with the help of the blown air from outside the combustion plant, according to fig. 6.

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The air blown by a fan is directed to a room that allows the system to cool (fig. 1), then the heated air is swirled through a trunk space, on which fins of sheet 27 are welded inside the furnace of the boiler 20. The housing 22 is provided with a circuit containing 23 supply pipes 23 in 12 pieces, copper pipe filling Φ 10x1x10 mm 26, which provides the heat transfer to the ventilated air. Also at industrial applications, a wake-up flame must be provided through a supply line 25, a piezoelectric system 21 for ignition of the flame.

The carbon resulting from the process of decomposition of CO ₂ , due to the reactivity of hydrogen with oxygen from CO ₂ , is recovered through the pipe 10, and another part is dusted at the base of the outbreak of the thermal boiler, where the installation is located, which is periodically recovered. It is very important to note that the creation of a larger amount of atomic carbon in the outbreak is not allowed, as there would be a risk of its ignition, which would lead to the outbreak of the outbreak.

In a first embodiment, an installation with an external diameter of 300 mm, a length of 300 mm, a thickness of the Mg layer of 30 mm, a thickness of the powder Mg layer of 5 mm, and a thickness of the quartz layer of 20 mm are used.

At this size of the plant, flow rates of 900 m ³ / h and 3000 m ³ / h can be burned, and carbon dioxide proportional to at most half of the hydrogen used (at 2 moles of H ₂ at most 1 mole of CO ₂ ).

For situations where we do not have carbon dioxide with high concentrations of 98 ... 99% you can also use gas mixture such as nitrogen: 40 ... 60%, oxygen 2 ... 4% and CO ₂ 36 .. .48%, gas obtained from existing chemical processes.

In all situations, the requirement of O ₂ in both free and in combination with CO ₂ is taken into account, so as to ensure the complete combustion of hydrogen.

In the second embodiment, respectively, in the industrial one, in addition to the installation described in example 1, a housing with a diameter of 1200 mm is used, and a fan that ensures both the cooling of the above-mentioned installation and the management of the flame obtained. . A pipe is also used for the adduction of methane gas in order to make the wake fire, and the ignition is carried out with a piezoelectric installation. The operating cycle is as follows: when starting - boiler ventilation, ventilation shutdown, flame ignition, progressive hydrogen valve opening, progressive CO ₂ valve opening, hot air introduction for flame and heat management, and at stop - ventilation stop, stop CO ₂ , stop H ₂ , stop flame wake.

Claims (2)

1. Burning process of hydrogen carbon dioxide mixture, based on 3 phase reactions H ₂ + CO ₂ + Mg -> MgO + C + H ₂ O, MgO + H ₂ -> Mg + H ₂ O + Q and the general balance reaction 2H ₂ + CO ₂ -> C + 2H ₂ O + Q, using two moles of hydrogen for at most one mole of 5 carbon dioxide, characterized in that, in a first phase, the hydrogen is burned from the H ₂ -CO ₂ mixture in the presence of magnesium as a catalyst, in a chamber 7 with holes for the discharge of gases and carbon atoms, with MgO formation, using two moles of hydrogen for at most one mole of carbon dioxide, in the second phase, in the same enclosure where the combustion of hydrogen takes place according to the first phase, the addition of hydrogen allows the magnesium to regenerate, and the flame and heat released by the combustion of hydrogen and 11 magnesium are directed with hot air after the air goes through a circuit with copper pipe filling, based on an operating cycle previously established, namely: starting the boiler 13 ventilation, followed by the ventilation stop, the ignition of the wake flame, the progressive opening of the hydrogen valve which is continued with the progressive opening of the carbon dioxide valve 15, the introduction of hot air to direct the flame and heat, and when the shutdown occurs, the ventilation, carbon dioxide, hydrogen and the flame wake are stopped. 17 2. Combustion plant for combining hydrogen with carbon dioxide, consisting of a housing (1) of stainless steel, on the outside of which there is a hydrogen supply line (2), 19 a carbon dioxide supply line ( 4), a carbon recovery pipe (10) and a catalyst filling pipe (17), which ensures the transfer of oxygen from 21 to carbon dioxide to hydrogen in case of losses, characterized in that, inside, of the hydrogen inlet pipe (2), there is a uniform distribution chamber of 23 hydrogen (M1), connected to a uniform distribution chamber of carbon dioxide (M2), a chamber (M3) for mixing hydrogen with carbon dioxide, and a chamber 25 for the catalyst (14), provided with a deflectord homogenization of the gas mixture (16), and comprises feed pipes (23), located in a housing (22) inside which it is 27 a filling of tea copper wire (26) and a methane feed pipe to ensure the flame wake (25). 29