KR20030034056A - System for controlling and eliminating hydrogen - Google Patents

Abstract

The system is intended to monitor and remove hydrogen and flammable gases in the air with the help of catalysts. The system includes a device consisting of a passive hydrogen recombiner and a monitoring detector, wherein a free convection supply of the gas mixture of the indicated and removed elements is used, the elements having the same type of structure, wherein the detector is internal to the recombinator. Or may be located externally.

Description

System for monitoring and removing hydrogen {SYSTEM FOR CONTROLLING AND ELIMINATING HYDROGEN}

The measuring system WS-85 of the catalytic detector and the recombiner FR90-1500 are known from SIEMENS, based on the German patent DE 3727207 A1, patented in 1989.

Most catalytic devices known for hydrogen removal are filled with solid catalyst located on an internal base (especially in FR90-1500) in the duct. The gaseous mixture in the duct is heated to indicate the exothermic process of hydrogen oxidation in the catalyst. The heated gas allows the external gas mixture to be continuously supplied to the base of the recombiner because of Archimedes' principle when expanding through the duct.

Known recombiners (patent DE 3727207 A1, 1989) use flat metal modules and ceramic panel elements as catalysts. In order to prevent a probable effect on the catalyst of the external environment, the outermost surface of the cover is fitted with an additional system, which opens the catalyst only at the moment of incidence (increase in temperature or pressure). A system of heat release is used to prevent possible large fires of the incoming gas mixture resulting from overheating of the catalyst. The cover of the recombiner is used to protect the catalyst from overheating during the oxidation of the surrounding hydrogen.

In considering this way, the inventors have developed the hope of achieving optimum hydrogen oxidation conditions immediately on the catalyst surface in developing the structure of the hydrogen recombiner. As a result, it is not acceptable for all processes generated by moving hydrogen to the catalyst surface (hydrogen diffusion on the catalyst surface, convective flow in the cover of the recombiner).

The geometries of highly controlled catalysts among the hydrogen recombiners considered, therefore, have a stable boundary layer structure. Because of the presence of the boundary layer, hydrogen migration through the boundary layer is essentially reduced, thereby not only reducing the combustion rate of hydrogen, but also incomplete combustion. Incomplete combustion of hydrogen can cause a large fire by the hot air and hydrogen mixture of a potentially hazardous outlet, with respect to the hydrogen and air mixture that is burned at the bottom of the active module of the recombiner. For a stable boundary layer, the rate of migration of hydrogen at this location is of considerable magnitude, essentially faster than the rate of heat transfer. This factor can also cause breakdown of the catalyst coating through partial overheating.

On the other hand, a stable boundary layer structure on the catalyst wall can move the flow of hydrogen and air to the core, which increases the overall dynamic resistance of the gas in the system. The magnitude of the gas's dynamic resistance to natural convection systems determines the efficiency of hydrogen and air flow rates through the catalyst and the recombiner's efficiency.

Thus, the hydrogen recombiners shown are not optimal at certain combustion rates.

Known thermal catalyst hydrogen detectors are used by being coated with a conductive wire made of a catalyst material heated by a thermal resistance, i.e., current, and included in the measuring device. In the presence of an analytical mixture of combustible gas and oxygen, a catalytic reaction occurs at the sensor surface, which causes heating. The characteristic signal of the presence of hydrogen is a change in the electrical resistance of the sensor, which occurs because of an increase in the catalyst temperature and a balance of the measuring device. If there is excess oxygen, the reaction rate is linearly proportional to the concentration of combustible gas. However, heated filaments that are exposed as they are are not safe at the rate of disasters caused by hydrogen. Likewise, the presence of exposed conductors carrying electricity is generally undesirable. For this reason, it is common to find a sensor of a hydrogen detector that is segregated from the analytical medium, and the measurement is carried out in a specially constructed flow of analyteable gas (gas supplied at constant velocity). For this reason, an external inducer (such as a fan) is used, or a special cover of porous material for supplying the gas analyzed by diffusion to the sensor is used.

The direct use of such a detector in an analytical gas medium poses certain difficulties since the detector's response to a finite amount of heat generation is determined by the thermal properties of the medium. Likewise, the response time of the detector to the emergence of hydrogen can be very long, especially for diffusion detectors based on diffusion through porous materials. A characteristic signal of the presence of hydrogen is a change in the electrical resistance of the sensor with respect to the electrical resistance of the comparison element that occurs due to the temperature increase of the catalyst.

The hydrogen detector described above has many disadvantages. In other words,

Hydrogen concentrations are not measured directly in the analytical medium, and in specially prepared probes.

The reaction time depends on the rate of diffusion of the hydrogen, ie the rate of preparation of the probe, which is very long.

Sensors operating in extreme conditions (platinum filaments and heat resistance carrying high currents) are used.

It costs a lot

The present invention relates to a system for the principle of monitoring hydrogen accumulation in air and also preventing hydrogen from accumulating above 4% by volume, the low flammability limit of hydrogen in air.

1 is a cross-sectional view in a vertical plane of a device according to the invention.

2 is a detailed view showing how a monitoring detector embodied in section and in accordance with the present invention is constructed;

3 is a basic flow diagram for connecting a detector to data monitoring.

The present invention relates to a system for the principle of monitoring hydrogen accumulation in air and also preventing hydrogen from accumulating above 4% by volume, the low flammability limit of hydrogen in air. This process is carried out using the maximum parameters in the process of hydrogen recombination, ie greater operating efficiency at a smaller overall dimension and minimal possible catalyst material. Process safety for hydrogen recombination is achieved with maximum hydrogen oxidation efficiency (actually 100%). By characterizing the gas mixture structure at the maximum volume, the hydrogen content read should be reduced quickly, in order to use the minimum amount of operating parameters immediately measured for concentration reading without the hydrogen content being dependent on external conditions. In other parameters of influence and maintenance of the external environment, all elements of the device shall not be sources of ignition or explosion of flammable or explosive gas mixtures.

Hydrogen monitoring and removal systems are implemented in complex devices where it is essential to prevent the accumulation of hydrogen in the air at multiple locations throughout. The system is a tool for a method for rapidly removing hydrogen in an emergency caused by a large concentration of hydrogen in the air region and for measuring the concentration of hydrogen quickly and safely in a medium on gas containing oxygen. Is proposed. The above-mentioned device is proposed as an add-on to the standard cooling system for hydrogen power plants under normal conditions, and in case of emergency it is not possible to use the cooling system in an effective manner, the basic device in case of emergency caused by the disturbance in the electrical supply. Is proposed as.

The apparatus consists of two basic components: a passive catalytic hydrogen recombiner (RPC) and a thermo-catalytic hydrogen detector (DTC).

DTC and RPC devices are based on known principles of catalytic combustion of hydrogen with abundant air, and in the case of DTC, readings on the thermal effects of catalysis are used to determine the concentration.

The system is used in various fields of industrial production, for example in the accumulation of explosive concentrations of hydrogen and flammable gases, including nuclear power plants using reactors cooled with water, and also in the electrochemical industry, gas pumping. It is applicable as a safety measure to prevent explosion by heat at the pumping station.

Based on several means of increasing the combustion rate and safety of hydrogen, the claimed system overcomes the above-mentioned problems and also reduces the cost of the corresponding hydrogen recombiner, while increasing safety and reliability and tapping among test elements for the hydrogen detector. It was designed to increase the absence of.

The technical result of the hydrogen recombiner is obtained by an activated high performance porous material (HPCM) used as catalytic element, which has an irregular three-dimensional spatial structure, which prevents the creation of a stable boundary layer for dynamic gas flow. Since it is not allowed by default, the use of HPCM catalysts, and even the use of these smaller catalysts, results in a substantial increase in material and heat transfer parameters. The choice of catalyst allows the development of recombiners with optimum hydrogen burning rates.

Recombinant safety is obtained through the choice of metal as the material for the solid porous catalyst. The high thermal conductivity of the catalyst material facilitates the absence of certain hot spots that can cause ignition of hydrogen.

High hydrogen burn rates are obtained, in particular, by constructing a convection cover of the recombiner, which consists of two vertical walls inside and outside. The space between them is filled with insulation. The rate of hydrogen combustion is determined by the rate of hydrogen and air mixture through the catalyst, which balances the gas dynamic resistance of the recombiner and the increase in Archimedes force. The Archimedes force is determined by the temperature of the gas in the convection cover. If there is a significant heat loss in the convection cover of the recombiner, the hydrogen burning rate is reduced. The recombiner is insulated so that there is no heat loss in its convection cover.

The solid catalyst is located in a support that is insulated from the convection cover of the recombiner so that catalytic combustion of the hydrogen begins as soon as hydrogen appears and minimizes heat loss.

The space inside the convection cover of the recombiner is divided into two or more parts through a vertical partition to prevent non-uniformity of catalytic combustion when the recombiner effect is reduced under the through-section.

The hydrogen combustion efficiency of the Siemens FR-90 / 1500 recombinator closest to the German patent 3727207 A1 does not exceed 0.4 nl / s when the hydrogen concentration is about 3% by volume and the through cut of the convection cover is about 300cm ² . Under these same conditions, the hydrogen combustion efficiency for the recombiner of the invention amounts to 0.8 nl / s.

The technical result for a hydrogen detector is by using natural convection flows to supply analytical air to the detector's sensor (solid porous catalyst). Within the cover, the explosive test heat transfer element is positioned to allow for natural convective flow of air that can be analyzed through the detector sensor.

The use of highly porous porous materials (HPCM) with specially selected parameters allows the required velocity of the convective flow.

The convection cover consists of two vertical walls inside and outside, where the intermediate space is filled with insulation to minimize heat loss and to minimize the power required to preheat the incoming gas stream and catalyst.

The safety of the detector is achieved by selecting a metal as the material for the porous catalyst. The high thermal conductivity of the catalyst material allows for the absence of local hot spots that can cause disasters by hydrogen. For this same purpose, the catalyst is located in the separating support which is insulated from the hydrogen detector cover.

The temperature difference between the previously heated air stream and the catalyst and the air stream exiting the catalyst is measured to determine the concentration of hydrogen in the air. When hydrogen is completely oxidized in the convection stream of air through the catalyst, the following simple proportionality exists between temperature and concentration. In other words,

C _H2 = AT (3 &.% F2) /83.5 (where AT = measured temperature difference, C _H2 = volume concentration of hydrogen).

The hydrogen detector can be located both outside and inside the recombiner convection cover, where inside the hot convection flow of the detector accelerates the start of the recombiner process in the presence of hydrogen. In the recombiner operation in the presence of hydrogen, the working distance of the detector is essentially large, and if the convection flow of the recombiner is stronger, more volume of air is supplied.

The switching block includes a thermocouple signal amplifier and a microprocessor for processing, storing and displaying signals at the detector, which switching block can be used to read the measurements of the complete hydrogen detector of the system.

As the active element of the hydrogen detector, a porous material having a very high porosity (HPCM) is used.

According to a preferred example of a practical embodiment of the present invention, the following drawings are attached as an integral part of the detailed description in order to help complete the detailed description of the invention and to better understand the features of the present invention, wherein the drawings are The description is not intended to be limiting.

In the above figure, how a system for monitoring and removing the hydrogen mounted in the apparatus is composed of two basic components, one corresponding to the term "recombinant A" and another component corresponding to the "detector B" of the recombiner. It is shown to see whether it includes.

Rejoiner A according to the invention represents a vertically mounted duct with double walls assembled to a corrosion resistant material, for example stainless steel. The inner wall of the recombiner is a convective cover 1, in which the overall size of the convective cover is for example a through cut of 180 250 mm ² for the purpose of achieving the required efficiency and reading the position of the device ( through-section) and the weight of 1500.

The solid catalyst 2 as a module located perpendicular to the incoming flow is located under the convection cover. The solid catalyst 2 is inserted in the cartridge 3 to prevent heat transfer to the wall of the convection cover. The cartridge 3 has two symmetrical structures, each of which has a long runs of wire 4. The cross section of the cross passage of the cartridge is smaller than the geometric area of the solid catalyst. The solid catalyst is inserted between the upper and lower structures of the cartridge, and the structures gradually get closer to each other. The cartridge 3 with the solid catalyst 2 is in full contact with the through-section of the convection cover, which is to prevent the cartridge 3 from direct air flow passing out of the catalyst.

There is a metal partition 5 which is firmly enclosed on the solid catalyst 2 and above the separation of the upper convection cover, the metal partition being located along the axis of the convection cover 1 in a manner parallel to the flow of the gas mixture. do. The metal partition 5 divides the internal volume of the convection cover into two or more parts associated with the cross section of the convection cover. For example, in the specimen of the recombiner shown in FIG. 1, the cross section of the convection cover is divided into three parts.

The convection cover 1 of the recombiner is located in the outer protective cover 6 of the recombiner, with a space of 10-20 mm between both covers. The space between the inner convection cover and the outer protective cover is filled with insulating material or material 7, for example air. The upper and lower portions of the protective cover of the recombiner have a wire mesh mouth 8.

In the recombinator "A" a monitoring detector "B" is located at the bottom between the cartridges 2 and 3 with the solid catalyst and the wire mesh mouse 8.

The monitoring detector "B" has two working versions, an internal detector and an external detector, which depend on the presence of the safety screen and the wire mesh (external).

The monitoring detector "B" comprises a solid catalyst 12 as a whole, like a disk located underneath the double walled vertical duct. The walls are made of anticorrosion material, for example stainless steel (convection cover). The convection cover is designed to compose a natural convective flow of the analytable mixture through the sensing element of the detector. As an example in FIG. 2, the total size of the detector is 100 mm in height and 30 mm in diameter.

The convection cover of the detector has an inlet and an outlet opening in the side region next to the end face closed by the wire mesh 22. There is a space between the inner cover 9 of the detector and the wall of the outer cover 10, which is filled with insulating material or air 11.

Like the disk, the solid catalyst 12 is mounted perpendicular to the flow into the metal cartridge cover 13 slightly away from the wall. An electric heating element 18 is located between the wall of the detector inner cover and the cartridge cover 13. The bottom and top of the solid catalyst are equipped with wire meshes-screens-heat exchangers 14 and 17.

An operational thermocouple 15 which measures the temperature of the incoming gas stream is mounted and connected to the central line of the structure under the screen of the heat exchanger 14. Thermocouple 16 measures the temperature of solid catalyst 12 or the temperature of the effluent gas stream. An actuating thermocouple 16 is mounted and connected between the on-axis screen-heat exchanger 17 with the thermocouple 15 and the solid catalyst. The cold junction connection of thermocouples 15 and 16 is a thermostat 19. Is made in the welding zone. Both the output of the thermocouple and the output from the heater are fed through a welding power point. In the configuration of the detector, the thermocouple 20 is used to measure the temperature of the weld zone of the thermostat. The thermocouple 20 is included in the structure of the cable carrying conductor. The thermocouple 21 is included in the structure of the detector to usefully investigate the catalyst in the recombiner and to measure the hydrogen concentration at large values of at least 2% by volume. The connection of the thermocouples 21 in the control panel is made in the solid catalyst 2 and the cold junction connection is made in the region 19.

3 shows a flow diagram for showing the joining arrangement of the elements according to the invention. The recombiner "A" is mounted at the point indicated, which includes an internal version of the monitoring detector "B _A ". In the apparatus according to the invention it is permissible to use an external monitoring detector "B ₁ -B _n " in a sufficient amount located in the region where hydrogen leakage is expected. The power supply for the detector heater is given on a line not associated with the measuring channel. Signals from thermocouples 15, 16, 20 and 21 (internal version “B _A ”) are treated as received signals and monitoring blocks, which may be system or business local area networks based on, for example, ADCs and personal computers. “Recoupler monitoring” couplings with proper use of thermocouples 21 allow the hydrogen content to be monitored in emergency situations (hydrogen concentrations above 2% by volume) simply by heating the recombiner's catalyst 2 without additional energy supply. Do it. “Recombinator Monitoring” combining is also a useful manual correction factor for recombiners. That is, when reading the hydrogen concentration of 1 vol% or more in the detector "B _A , B ₁ -B _n ", the thermocouple 21 must fix the temperature rise of the solid catalyst 2 in the recombiner.

The present invention relates to a system for monitoring and removing hydrogen and flammable gases in the air with the aid of a catalyst, comprising hydrogen and other fields of industrial production, including nuclear power plants using reactors cooled with water. It is applicable as a safety measure to prevent heat explosion in the field where the explosive concentration of flammable gas accumulates and also in the electrochemical industry, gas pumping station.

Claims (19)

A system for monitoring and removing hydrogen in air and for preventing the accumulation above the low flammability limit of hydrogen, and also intended to remove the hydrogen and combustible gas in the air, It contains two basic elements, a passive catalytic hydrogen recombiner and a thermo-catalytic hydrogen detector, The recombiner comprises a vertical duct defining convection cover 1, the through-section of the convection cover is completely covered with solid catalyst 12 included in the actual thermal catalyst detector. , Wherein said solid catalyst consists of a porous material with many pores. The method of claim 1, The solid catalyst has characteristic parameters corresponding to a mesh size of at least 2 mm, a size of a passing object below 1 mm, and a portion width of at least 3 mesh sizes, to monitor and remove hydrogen. System. The method according to claim 1 or 2, Wherein said solid catalyst is contained in a sponge metal. The method according to any one of claims 1 to 3, Wherein said solid catalyst is constituted and covered by a catalyst bed and an active element. The method according to any one of claims 1 to 4, The convection cover of the recombiner consists of two vertical walls of inner and outer walls, the space between the inner and outer walls being filled with insulation. The method according to any one of claims 1 to 5, And said solid catalyst is located in an adiabatic support separate from said convective cover. The method according to any one of claims 1 to 6, Wherein the space in the condenser cover of the recombiner consists of a series of vertical divisions located in two or more portions. The method of claim 1, And the catalyst detector for monitoring and removing the combustible gas comprises a heated solid catalyst in the form of a module and covering the through cut of the convection cover. The method of claim 8, And said solid catalyst is made of a porous material with many pores. The method according to claim 8 or 9, And said solid catalyst is made of a honeycomb of metal. The method of claim 8 or 10, Wherein said solid catalyst is of an alloy and is covered in a catalyst bed and an active element. The method according to any one of claims 8 to 11, Wherein said solid catalyst comprises characteristic parameters of a mesh size of at least 2 mm, a size of passing particles of at most 1 mm, and a module width of at least 3 mesh sizes. The method according to any one of claims 8 to 12, A system for monitoring and removing hydrogen, which is located inside the convection cover and comprises a heat transfer element for preheating the flow of incoming gas and the catalyst laminas. The method according to any one of claims 8 to 13, A central space defined between the vertical inner and outer walls of the convection cover is filled with insulation, wherein the system is for monitoring and removing hydrogen. The method according to any one of claims 8 to 14, Wherein said solid catalyst is located in an adiabatic support separate from the covers. The method according to any one of claims 8 to 15, And said solid catalyst is located in an adiabatic support separate from said convective cover. The method according to any one of claims 8 to 16, Using voltage thermocouples according to the incoming heated air stream and the temperature of the solid catalyst as a first signal in a monitoring sector. The method according to any one of claims 8 to 17, And use a voltage thermocouple according to the temperature of the incoming heated air stream and the effluent gas stream as a first signal at the monitoring detector. The method according to any one of claims 8 to 18, A connection of a thermocouple thermostat of a cold junction in said monitoring detector is used.