RU2181463C2 - Catalytic gas convector - Google Patents

Abstract

FIELD: power engineering; low-power domestic heating appliances. SUBSTANCE: proposed invention relates to low-power heating appliances operating on liquefied gas and used for periodical heating of rooms and locations with natural ventilation. Catalytic gas convector consists of housing accommodating tubular catalytic heating elements, convector starting system, gas flow rate stabilizer, thermoelectric converter, temperature controller pickup and gas supply pipelines. EFFECT: provision of new type of heating device ensuring effective ecologically clean combustion of hydrocarbon gases and safe operation of device owing to use of new principles of organization of operation of appliance. 6 cl, 2 dwg

Description

 The invention relates to household energy, to its industries related to household heating appliances of small power, operating on liquefied gas and used for periodic heating of household premises with natural ventilation.

 Currently, catalytic methods for the oxidation of hydrocarbon gases are widely used to create low-power household heating devices.

 In contrast to flame combustion methods, catalytic methods have significant advantages in terms of greater safety of the devices created due to the absence of flame and a significant reduction in the concentration of harmful impurities in the combustion products. When creating catalytic heating devices, porous catalytic plates are usually used, made of fibrous aluminosilicate or other media on which an active component is deposited, which provides the necessary activity of the catalyst. A variant of this design of catalytic heaters is described in R.E. Thompson, D.W. Pershing, E. E. Berkan. Catalytic combushion, a pollution-free means of Energy conversion. EPA-650 / 2-73-018 NTIS No. PB 22-3002. In this device, a platinum catalyst is supported on a fibrous aluminosilicate carrier. The catalytically active material is made in the form of a flat plate of a certain thickness. The heater uses two types of plates, one of which serves to ensure uniform distribution of gas over the entire surface of the plate, and the second to oxidize it. In this embodiment of the device, gas is supplied through a gas supply unit installed in the center of the gas distribution plate.

 The tests performed showed a high sensitivity of fuel oxidation to the flow rate of the supplied gas and the thickness of the fibrous plate, insignificant to the content of the plate with a twofold increase in its concentration relative to standard values. In the experiments, the thickness of the fibrous plate was measured from 1 to 2.5 cm.

Significant disadvantages of this design are:
- very strong sensitivity of the composition of the exhaust gases to the fuel feed rate, which provides a small range of power control;
- the presence of significant concentrations of unreacted hydrocarbons (600-1200 ppm) in the combustion products;
- the content of hydrocarbon oxide at the level of 10-20 ppm;
- heterogeneity of the composition of the emissions on the surface of the catalytic plate, increasing approximately two times during the transition from the central part to its edges and from bottom to top.

 Closest to the proposed invention is a gas catalytic fireplace, described in US Pat. RF 2057277, F 24 C 3/00, 1996]. In it, as in [R.E. Thompson, D.W. Pershing, E.E. Berkan. Catalytic combushion, a pollution-free means of Energy conversion. EPA-650 / 2-73-018 NTIS No. PB 22-3002. A fiber based catalyst is used.

 Structurally, the fireplace is made in the form of a box of sheet steel, inside of which a fuel element with a catalyst plate is placed. To ensure heat transfer, the upper wall of the box is made with perforations in the form of grooves, on the front side there is a window closed by a perforated wall. Below the grid there is a small hole, inside of which there is a flare device, on the right on the case there is a gas valve that regulates the gas supply with the help of an adjusting screw.

 The fuel element is a metal tray, inside which there is a coarse-mesh mesh, on it is a mat of fibrous thermostable material, which distributes gas over the entire surface and acts as a primary catalyst, and a second quartz-silica mat, on which a catalytically active composition is deposited. This mat serves as the secondary primary catalysis of flameless oxidation of gaseous hydrocarbons. All the elements listed above are fixed in the bath with the help of a clamping frame, on which a mesh of nichrome wire is stretched.

 To start, during which the catalyst plate is heated, a flare device is located under the fuel element, which simultaneously controls the flow of gas throughout the entire operation of the fireplace. In the flare device, a clock stone is used as a nozzle, the calibrated opening of which provides the necessary quality of a gas jet. Gas passes through a valve, a tee and simultaneously enters the cavity of the metal bath and into the flare device. A torch is ignited with a match, which, in turn, ignites the gas entering the bath and penetrating the two catalyst layers. As the catalyst warms up, the pulsating flame on its surface disappears and the combustible gas is almost completely oxidized. The torch is significantly reduced, but it burns constantly, controlling the gas supply during the entire time the fireplace is operating.

The disadvantages of this device are:
- the presence of an open flame as an indicator of the operation of the device;
- the complexity of the uniform distribution of hydrocarbon gas supplied in small quantities over the surface of the fibrous catalyst;
- an increase in the underburning of hydrocarbon gas along the length of the plate, due to an increase in the boundary layer and worsening mass transfer conditions;
- lack of automatic ignition and reliable stabilization of the flow rate of the supplied gas.

 The invention solves the problem of creating a new type of heating device that provides efficient environmentally friendly burning of hydrocarbon gases and safe operation of the device through the use of new principles for organizing the operation of the device.

 The problem is solved due to the design, which is a catalytic gas convector for periodic heating of household premises with natural ventilation, consisting of a housing inside which there are tubular type catalytic heating elements, a convector start system, a gas flow stabilizer, a thermoelectric converter, a temperature regulator sensor, pipelines for gas supply. The catalytic heating element is a tubular structure consisting of a gas distribution tube plugged on one side, on the surface of which, in a state sintered with it, a layer of catalytically active material is applied, which ensures environmentally friendly oxidation of hydrocarbon gas. One of the options for a catalytic heating element (KNE) is given in US Pat. RF 2062402, 6 F 23 D 14/18, 1996.

 The convector uses an automatic gas flow controller, there is a viewing window, a light electrical indicator of the operating mode, an air intake hole, a grill for hot gases, gas control knobs, a temperature regulator button and a piezo ignition system button for starting a flame burner. The catalytic heating elements are arranged vertically one below the other with gaps between them and the convector body. A thermoelectric converter is installed on the surface of the catalytic heating element to generate electrical energy.

 Figure 1 presents a General view of the convector. It consists of a housing, inside which all the main convector units are installed, shown in figure 2: a hydrocarbon gas supply unit, a device for starting a convector, catalytic heating elements with a thermoelectric converter, a temperature regulator to control the operating modes of the device, pipelines for gas movement.

 At the lower end of the casing there is an opening for air intake, which, after its heating as a result of a chemical reaction, enters the environment through a grate at the upper end of the convector.

 Front and rear, the convector body is closed by walls. On the front wall there is a viewing window and an indicator of the convector in steady state flameless catalytic combustion of gas. A grill is installed on top of the case. The housing is mounted on legs. On top of the body are the handles for controlling the convector.

 Functional diagram of the convector is shown in figure 2.

 Gas (propane-butane mixture) 1 from the cylinder through the inlet fitting of the convector enters the gas filter 2, which ensures the purification of gas from mechanical impurities.

 In the ignition mode, gas is supplied through the valve 3 to the burner 4 when the control knob for supplying gas 5 to the burner is installed.

 By pressing and lowering the button of the piezoelectric gas ignition device 6, the gas exiting the burner 4 is ignited by spark discharges in the gas stream.

 With the manifestation of a stable flame on the burner 4, which is controlled through the viewing window of the front wall of the convector (Fig. 1), the gas supply to the KNE 7 is turned on by installing the control knob 5 for the gas supply to the KNE 7 and pressing the button of the thermo-electromagnetic valve 8.

 In this position of the controls, gas is supplied to the KNE 7 through an open thermo-electromagnetic valve 8, an open channel of the rozig of the temperature control valve 9 and a collector 10.

 The gas leaving the lower CNE is ignited by the flame of the burner. The gas leaving the upper CNF is ignited by a transfer of flame from the lower to the upper CNF. The appearance of a pulsating flame on the surface of the KNE is controlled visually through the viewing window (lower KNE) and the convector grate (upper KNE). The button of the thermo-electromagnetic valve 8 is manually held pressed for 10-20 s after the appearance of a pulsating flame on the surface of all CNEs.

During this time, the sensing element (hot junction) of the thermocouple - 10 is heated up to a temperature of (300 ± 20) ^o C. by an external pulsating flame of the lower KNE - from a thermocouple to the winding of thermo-electromagnetic valve 8, a voltage of less than 7 mV is applied, which makes it possible to keep thermo-electromagnetic valve 9 in the open condition. The need to manually hold the button disappears.

If the ignition mode passes normally, then after about 450 s an external pulsating flame is not observed on the KNE, the convector enters the flameless catalytic combustion of gas at a temperature on the surface of the KNE of about 450-550 ^o C.

 Then the gas supply to the burner device is shut off by installing the gas supply control knob 5 to the burner device 4, as a result, the flame on the burner device 4 goes out, the device is in working condition. To carry out the oxidation reaction on CNE, air 11 is supplied through a lower opening in the housing due to natural circulation. The resulting hot gases 12 are emitted through the upper convector grill into the environment to heat it.

 In operating mode, gas at KNE 7 is supplied through an open thermo-electromagnetic valve 8, a working channel of a thermoregulator tap 9, a gas flow stabilizer automatic 13, and a collector 10.

 The gas flow stabilizer automatic 13 provides stabilization of the gas flow in the operating mode, which allows to reduce the content of CO and unreacted hydrocarbon gas in the combustion products within environmental standards by eliminating the increase in gas pressure above (2000 ± 200) Pa.

When the temperature at the lower KNE decreases below (270 ± 20) ^o С, the gas supply to the convector is blocked by the thermo-electromagnetic valve 9 in the operating mode due to a decrease in the voltage taken from the thermocouple 10 below the threshold value.

With an abnormal increase in the temperature of the combustion products at the outlet of the convector grate to (270 ± 20) ^o С, the gas shutoff valve of the temperature control valve 9 is activated, the sensitive element of which 14 is installed near the grate in the exhaust stream of the combustion products.

 The gas supply to the NEC is reduced, the temperature of the combustion products at the outlet of the grate is reduced, which protects the NEC from overheating and, accordingly, destruction.

 A thermoelectric converter 10 is installed on the lower catalytic heating element, generating electricity for the operation of the indicator 15.

 The indicator 15 emits light without changing the luminous flux, since the voltage removed from the thermocouple 16 exceeds 2 V.

 The convector is turned off by shutting off the gas cylinder with a valve or by installing the knob 5 for controlling the gas supply to the KNE in the closed position. In this case, the gas supply to the KNE is stopped and the device turns off.

 The indicator 15 on the front wall of the convector for 2-3 minutes ceases to emit light due to the inertia of the thermal converter.

Distinctive features of the proposed technical solution are:
- the use of tubular catalytic heating elements for the environmentally friendly combustion of hydrocarbon gases;
- the use of piezoelectric ignition of the burner device to start the device;
- automatic stabilization of the flow of hydrocarbon gas supplied to the convector;
- the use of a thermoelectric converter mounted on a catalytic heating element and generating electricity for an indicator (light bulb) of operation modes;
- the use of a temperature controller to ensure the safe operation of the convector.

 The essence of the conversion is illustrated by the specific technical implementation of the device and the test results.

 Example 1. The catalytic gas convector.

Overall dimensions of the convector, mm, no more than:
Height - 664
Width - 225
Length - 534
Outer diameter of the outlet fitting of the convector, mm - 12 - 0.2
The mass of the convector, kg, no more - 12.8
Technical characteristics of the convector.

Rated thermal power, kW - 3 + 0.3
Fuel Consumption - Gas Mixture (Propane-Butane)
Nominal consumption of a gas mixture by volume, m ³ / h:
In operating mode - 0.108 ± 0.005
In the ignition mode, no more - 0.27
The working pressure of the gas mixture at the inlet of the convector, Pa ± - 2000 - 3000
The working pressure of the gas mixture at the inlet of the collector in operating mode, Pa - 2000 ± 200
The temperature of the surface heating of the catalytic heating elements, ^o C - 450 - 550
The convector can work in the following modes:
1) ignition (device start);
2) flameless catalytic combustion of gas (in operating mode);
3) gas supply shutdown when the temperature of the CNE surface decreases to (300 ± 20) ^o С (device shutdown);
4) automatic reduction of gas flow in the ignition mode when the temperature of the gas combustion products is increased to (270 ± 20) ^o С;
Convector Test Results
The consumption of combusted gas is 0.108 m ³ / h;
The temperature of the exhaust gas - 200 ^o C
The composition of the gases leaving the convector
CO - 2 - 3 ppm
NO - No
C ₃ H ₈ + C ₄ H ₁₀ - 6-8 ppm
O ₂ - -
As follows from the above example, the present invention ensures the achievement of the following technical result: the possibility of creating a device for the environmentally friendly burning of liquefied natural gas for heat during heating of domestic premises.

The thermal power of the convector is provided by flameless catalytic combustion of the gas mixture in the diffuse-convection type CNE at a temperature of 450-550 ^o С with the formation of combustion products that are harmless to humans: carbon dioxide and water vapor. This is achieved through the use of catalytic heating elements and automatic stabilization of gas flow.

Claims (6)

 1. Catalytic gas convector for periodic heating of household premises with natural ventilation, consisting of a housing inside which are located tubular catalytic heating elements, convector start system, gas flow stabilizer, thermoelectric converter, temperature regulator sensor, gas supply pipelines.  2. The convector according to claim 1, in which the catalytic heating element is a tubular structure consisting of a gas distribution tube plugged on one side, on the surface of which, in a state sintered with it, a layer of catalytically active material is applied, which ensures environmentally friendly oxidation of hydrocarbon gas.  3. The convector according to claim 1, in which an automatic gas flow controller is used.  4. The convector according to claim 1, in which there is a viewing window, a light electric indicator of the operating mode, an air intake hole, a grill for hot gas outlet, gas control knobs, a temperature regulator button and a piezo ignition system for starting a flame burner.  5. The convector according to claim 1 or 2, in which the catalytic heating elements are arranged vertically one below the other with gaps between them and the convector body.  6. The convector according to claim 1 or 2, in which a thermoelectric converter is installed on the surface of the catalytic heating element to generate electrical energy.

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