Plant for electrochemical production of hydrogen

The invention relates to electrochemical technology, in particular to installations for obtaining hydrogen by water hydrolysis, and can be used in the chemical industry, as well as to obtain hydrogen for household and other purposes.

The installation for obtaining hydrogen by the hydrolysis method is known, which includes a hermetic body, filled with working liquid, in which a bipolar electrolyzer is connected, connected to a continuous current source [1].

The disadvantage of this installation is the low reliability, high operating costs, as well as the fact that safety is not ensured when operating it.

The closest solution is the electrolyzer for the electrolytic obtaining of hydrogen, which includes a body, inside which are installed two cathodes, fixed by some current-conductive support plates, and two anodes, two diaphragms, which separate the cathode compartment from the anode. Above the electrode compartments are dome-shaped caps with hydrogen and oxygen exhaust connections. In the anodic and cathodic compartments there are located electrolyte outlet connections, connected at the bottom with о capacity, which communicates through a discharge pipe with a circulation pump with о intake pipe [2].

The disadvantage of this electrolyser is that the process performed at it requires high energy costs and is not sufficiently effective.

The problem solved by the present invention is to reduce the energy costs and increase the efficiency of the electrochemical process of obtaining hydrogen.

The installation for electrochemical obtaining of hydrogen, according to the invention, removes the disadvantages mentioned above by including an electrolyzer, at the bottom of which is located о capacity, and at the top - a hermetically removable load. Inside the electrolyzer, on the extremities are installed a perforated flat anode and a porous cathode in flux, located in a closed block of dielectric material, equipped with an electrolyte inlet connection. The anode and the cathode are connected to the DC source, between the anode and the cathode being placed in series some combination electrodes in flux, executed from a porous material of foamy nickel with modified surface for the reduction of the excess release of hydrogen, of which a porous fibrocarbon material is attached by means of a mesh. In the lower part between the electrode blocks, ie in the capacity are installed some electrolyte inlet connections, coupled with an о inlet pipe with a recirculation pump, the electrolyte is discharged from the electrolyzer in capacity through a pipe, the capacity communicates with a reservoir of electrolyte supply with an airtight lid via a feed pipe, a dispenser and a valve pipe. At the same time, the lower end of the pipe is located at the same level as the upper limit of a level indicator, installed on the electrolyzer. At the top of the electrode blocks are installed with adjustable funnel-shaped caps, fitted with adjustable valves for separate electrolyte and hydrogen release, the removable hermetic cap is equipped with a manometer, о valve and a connection for hydrogen evacuation.

The anode is made from electrode graphite or wearable titanium sheathing, coated with ruthenium dioxide and / or iridium dioxide.

As a porous fibrocarbon material, textile and non-textile materials with a layer thickness of 4 ... 8 mm, tablets of 1,5 ... 2 times the clamping mesh, made of plastic, with a cell size of 3 .. are used. 4 mm.

The modified surface of the electrode blocks is obtained by chemical-catalytic coating with nickel-molybdenum or nickel-tungsten alloy, or nickel-rhenium.

The technical result obtained is the reduction of energy costs and the increase of the efficiency of the electrochemical process of obtaining hydrogen.

The technical result is ensured by the presence of the combination electrode blocks in flux, executed from a porous nickel foam material with modified surface, cathodic polarizafi, on which the discharge of hydrogen results in a diffusion current limited with low overvoltage of its release to a potential. from 80 ... 100 mV. At the same time, inside this electrode the potential moves in a positive direction, and the contact border with the electrode of porous fibrocarbon material is polarized anodically and moves completely in the electropositive part, characterized by a high overvoltage of oxygen release, the potential being located. limits 180 ... 220 mV. Within the limits

MD 4206 Cl 2013.09.30 these values ​​of the potential at low values ​​of the current density of the current up to 3 ... 5 А / dm², anodic polarization curves are characterized by passivation sectors, not reaching the level of active oxygen discharge to the anode.

As a porous fibrocarbon material, textile and non-textile materials with a layer thickness of 4 ... 8 mm, tablets of 1.5 ... 2 times the clamping mesh, made of plastic, with a cell size of 3 ... are used. 4 mm, which in turn increases the stability of the porous fibrocarbon material from destruction in the anodic processes. The summary specific surface area of ​​the fibrocarbon material, anodized polarized, is 2 ... 3 times larger than the surface of the porous material of foamy nickel, cathodically polarized. From this it follows that the density of the anodic current at the electrodes of fibrocarbon material is 2 ... 3 times lower than the density of the cathodic current on the porous material of foamy nickel. This further decreases the probability of the release of free oxygen into the electrolyzer, thus facilitating the release of hydrogen at the cathode.

At the same time, at the cathode when the water molecules are discharged, the process of active hydrogen release proceeds. Moreover, due to the large specific surface area of ​​the porous material of foamy nickel, which is of a higher order due to the volume of the pores, the actual density of the current at the electrode made of porous material of foamy nickel is of a lower order. In this connection, the release of hydrogen at such an electrode results in low voltage at the electrodes and the yield of hydrogen is close to 100%, which contributes to the reduction of energy costs for electrolysis.

The porosity of the electrode blocks combining m flux and their increased active specific surface area allows the considerable reduction of the electrolyser dimensions and its more compact execution with the possibility of releasing a larger quantity of hydrogen, relative to the volume unit of the electrolyser. The possibility of carrying out the process of electrolysis in flux is ensured, which allows to increase the efficiency of this process due to the exchange and mass transfer, which diminishes the polarization and increases the yield of hydrogen.

At the same time, due to the intense flow of electrolyte through the pores of the electrode blocks in the flux, the gas bubbles that release quickly break off their surface, removing their blocking for the process of electrolysis of the water molecules, ensuring their removal in the free side of the slime. cathode of the electrolyte, diminishing its saturation with gas, which is one of the causes of the increased resistance of the electrolyte, and the increase of the voltage at the electrodes, which lead to the decrease of the current to the electrolysis and, respectively, to the diminution of the energy consumption.

The porous fibrocarbon material is produced on an industrial scale and represents the product of carbonization of textile and non-textile materials, obtained by heating them in an oxygen-free atmosphere. The process of obtaining them includes two stages: carbonization - carried out at temperatures of 900 ... 1500 ° C and graphitization - at temperatures of 2600 ... 2800 ° C. As a result, a carbon skeleton is obtained that confines over 99% carbon and repeats the shape of the initial material - the wires and fibers of the material. They possess high electroconductivity, high specific surface values, porosity and provide an intense mass transfer under the conditions of the fluid flow, which is why they can be used as porous electrodes, being one of the types of three-dimensional electrodes.

For these purposes, non-textile porous fibrocarbon materials such as ВНГ-50-2, ВИНН-250, HTM-200, ВВП-66-95, KHM can be used, which according to the literature data have the following characteristics: monofiber size 4.5. .6 pm, specific reaction surface 1900 ... 3000 cm²/ g, the electrical conductivity in the free state 0.1 ... 1.3 S / cm, and in the compressed state 0.4 .... 2.6 S / cm, their porosity is within the limits of 0.92 ... 0.98. Textile porous fibrocarbon materials can be used as the type ТВШ, ТГН with the size of the monophyrite of 4.3 ... 4.6 pm, gathered m ropes with a diameter of 0.04 ... 0.06 mm. The specific reactive surface area is 2900 ... 3100 cm²/ g, the electrical conductivity of 0.13 ... 0.4 S / cm and the porosity of 0.83 ... 0.91.

MD 4206 Cl 2013.09.30

The invention is explained by the drawings in FIG. 1 -2, which represents:

FIG. 1, the scheme of the installation for the electrochemical obtaining of hydrogen;

FIG. 2, diagram of the combined layers of an electrode (in section).

The installation for electrochemical hydrogen obtaining includes an electrolyzer 1, at the bottom of which is located о capacity 13, and at the top - a hermetically removable cap 22. Inside the electrolyzer 1, on the ends there is a perforated flat anode 2 and a cathode. 3 pores in flux, located in a closed block 4 of dielectric material, equipped with an electrolyte inlet connection 11. The anode 2 and the cathode 3 are connected to the DC power source 26. Between the anode 2 and the cathode 3, series of electrodes 5 in combination fluxes, executed in a porous material 6 of foamy nickel with modified surface, are used in series to reduce the overvoltage of the hydrogen release, which is attached by means of a clamping net. 8 a material 7 fibrocarbonic pores. In the lower part between the electrode blocks 5, namely in capacity 13, there are installed connections 11 of the electrolyte inlet, joined by an о conduit 12 with a recirculation pump 14. The electrolyte is discharged from the electrolyzer 1 in capacity 13 through a conduit 15. Capacity 13 communicates with an electrolyte feed tank 18 with a hermetic lid 19 via a feed pipe 15, a dispenser 17 and a pipe 16 with a valve 20, at the same time the lower end of the pipe 16 is located at the same level as the upper limit. of a level 21 indicator, installed on the electrolyzer 1. At the top of the electrode blocks 5 are installed with adjustable funnel caps 9 in the form of a funnel, equipped with adjustable valves 10 for the separate discharge of the electrolyte and the released hydrogen. The removable airtight lid 22 is equipped with a pressure gauge 23, a valve 25 and a connection 24 for the evacuation of hydrogen.

Anode 2 is made of electrode graphite or wearable titanium sheathing, coated with ruthenium dioxide and / or iridium dioxide.

As a porous fibrocarbon material 7, textile and non-textile materials with a layer thickness of 4 ... 8 mm, tablets of 1.5 ... 2 times the clamping mesh 8, made of plastic, with a cell size of 3 are used. .4 mm.

The modified surface of the electrode blocks 5 is obtained by chemical-catalytic coating with nickel-molybdenum or nickel-tungsten alloy, or nickel-rhenium.

The facility for electrochemical hydrogen obtaining works as follows.

The concentration electrolyte solution fixed by means of the dispenser 17 to the open position of the airtight lid 19 and of the valve 20 is blocked in capacity 13, and through the pump 14, passing through the pipe 12, the connections 11 'and 11 and through the electrode blocks 5 and cathode 3, fills the electrolyzer 1 up to the top level of the electrode blocks 5 and starts the electrolyte leakage through the pipe 15?, according to the data of indicator 21. At this point the liquid will reach the same level in the pipe 15, which will lead to the closing of the lower edge of the pipe 16, of the dispenser 17 and the liquid will cease to enter the electrolyzer 1.

Then, at the continuous recirculation of the electrolyte through electrolyzer 1, the anode 2 and cathode 3 from the DC source 26 are supplied with DC, the electric circuit is included in the electrolyzer, which ensures the alternative formation of the negative and positive charge at the electrodes 5 and the beginning of hydrogen release. At the same time, the electrode blocks 5 work in pairs.

The perforation of the perforated anode 2 is conditioned by the possibility of increasing the distribution of the power lines of the electric current in the gap between the electrodes and of the increase, as a result, of the capacity of dispersion in the volume of the electrolyte, which improves the functioning of the blocks of electrodes combined.

A double role is played by the funnel-shaped caps 9 with the valves 10, installed with play above the electrode blocks 5 for separating the gas-liquid phase, and at the same time ensuring the formation of an overpressure of the electrolyte in the electrode blocks 5 for the electrolyte pass through. porous electrodes. At the same time, the liquid phase (electrolyte), under a certain pressure, is emitted by this play in the recirculating electrolyzer spool, and the hydrogen gas phase is released through the calibrated holes, with which

MD 4206 Cl 2013.09.30 the lids 9 are fitted, in the recess above the electrode blocks 5, limited by the removable hermetic cover 22 with the subsequent discharge through the connection 24.

The electrolyte surplus as its level increases in electrolyzer 1, is it continuously drained through the pipe 15? in capacity 13 for recirculation. As electrolyte for electrolysis, distilled or desalinated water with electrical conductivity up to 10 'is used.⁴ S / m, to increase the electrical conductivity of which solutions with known compositions are prepared, for example, KOH solution of 25 ... 30% or NaOH of 16 ... 20% with addition of sodium or potassium chromate in quantity 2.5 ... 3 g / L, or other solutions. The role of the latter is oriented towards improving the functioning of the cathodes on account of passivating their surface and not allowing them to discharge electrolyte impurities.

The mechanism of the hydrogen regeneration process at the electrode is related to the dissociation of 2H water molecules₂O <-> 2H⁺ + 2OH 'and the discharge of hydrogen ions, which takes place through a series of reactions: H⁺ + e -> Hads, which is further softened by the recombination reaction: Hads. + Hads. -> H2, or by electrochemical desorption according to Heyrovsky's reaction: H3O⁺ + Hads + e -> H₂ + H₂O. Theoretically, to obtain 1 m³ 805 g of water is consumed by hydrogen, but as a result of vapor formation the consumption can be increased by 5 ... 10%. In these conditions, the consumption of electric current practically depends only on the losses to the electrical resistance in the installation. The presence of capacity 13, of tank 18 with lid 19, of pipe 16 with valve 20 and of dispenser 17, allows the continuous correction of the electrolyte concentration and the automatic maintenance of the given level by filling with water for electrolysis.

The hydrogen released in the electrolyzer is discharged at normal pressure, but in extreme cases the pressure may increase more than atmospheric, which is fixed by the manometer 23 and the valve 25.

Thus, the operation of the combination electrode blocks in flux, executed from different porous materials - foam metal with modified surface with nickel alloy with molybdenum, tungsten or rhenium, applied by chemical-catalytic deposition to reduce the excess release of hydrogen - on the one hand, and fibrocarbon materials, which possess a high voltage surge of oxygen release, connected according to the bipolar electrolysis scheme, ensure the achievement of the proposed purpose, oriented to increase the efficiency of the electrochemical process of obtaining pure hydrogen and to reduce the energy costs for obtaining it.

(56) Bibliographic references cited in the description:

1. MD 3660 G2 2008.07.31

2. RU 2038422 Cl 1995.06.27 (57) Claimant: