RU164691U1 - Pyrolysis heating device - Google Patents

Abstract

1. A pyrolysis heating device containing a solid fuel hopper located in a single vertically oriented housing, a gasification chamber below it having an internal heat-resistant heat-insulating coating and a pyrolysis gas exit window with a grate, and below it a pyrolysis gas combustion chamber having an internal heat-resistant heat-insulating coating , an outlet gas duct connecting the combustion chamber of the pyrolysis gas to the heat exchanger, as well as at least one fan installed outside the housing, from characterized in that the heat exchanger is spatially separated from the hopper, gasification chamber and the pyrolysis gas combustion chamber, the heat carrier circulating in the heat exchanger does not have direct contact with the outer walls of the gasification chamber and the combustion chamber, and the fan pumps 2 times the air into the combustion chamber 3 times higher than required for complete combustion of the pyrolysis gas. 2. The pyrolysis heating device according to claim 1, characterized in that there is a free space (internal cavity) between the outer walls of the combustion chamber and the inner walls of the housing through which the air flow, which is pumped by the fan into the pyrolysis gas combustion chamber, passes. The pyrolysis heating device according to claim 1 or 2, characterized in that the air entering the gasification chamber is supplied to it through an additional duct from the above-mentioned space between the outer walls of the pyrolysis gas combustion chamber and the inner walls of the housing. Pyrolysis heating device according to claim 1 or 2, characterized in that the pyrolysis gas combustion chamber is made in the form of two

Description

F 23 B 10

Pyrolysis heating device

The utility model relates to a power system, in particular, to heating devices in which solid fuel of plant origin (firewood, woodworking waste, wood chips, bark, straw, husk, sawdust briquettes) is subjected to high-temperature gasification (pyrolysis) followed by burning of pyrolysis gases.

A pyrolysis (gas-generating) heating device is known from the prior art, comprising a solid fuel hopper, a gasification chamber, a pyrolysis gas combustion chamber and a gas-liquid heat exchanger combined with a common vertically oriented housing, and the liquid coolant circulates in a “jacket” formed by double walls of a common device cases (for example, RU 98 534 U1, EP 2 221 540 A2). According to this scheme, many commercially available heating pyrolysis boilers are made, for example, products from Astra, Atmos, Buderus, Dakon, Lavoro, OPOP, Viessmann, Ziehbart.

This technical solution has several inherent disadvantages, the root cause of which can be formulated as follows: "what should be hot is cooled." To ensure efficient and sustainable gasification of wood, it is necessary to maintain a temperature of 100-200 degrees. C in the upper part of the hopper (drying zone), 300-550 degrees. at the bottom of the hopper (dry distillation zone), 750-900 degrees. in the active zone of the gasification chamber. Direct contact of the external walls of the solid fuel bunker and the gasification chamber with the coolant prevents the provision of such a thermal regime; This is especially pronounced in cases when water having a high heat capacity is used as a heat carrier.

The practical consequence of this is the low efficiency and instability of the process of gasification of solid fuels, the need to use firewood of long-term drying with a moisture content of not more than 20% (as conscientious manufacturers directly warn the user), deposits of tar and ash on the walls of the fuel hopper and gasification chamber, which increases the cost and complicates the operation of the heating device.

In addition, direct contact of the liquid coolant (water) with the red-hot walls of the gasification chamber and the combustion chamber can lead to its rapid boiling in the event of an emergency failure of the forced coolant circulation system. Prevention of this danger requires the inclusion of additional systems in the composition of the heating device that complicate and increase its cost.

In addition, the combination of a gas generator and a gas-liquid heat exchanger in one housing forces the use of a geometrical shape of the heat exchanger that is not optimal in terms of structural strength (flat walls under hydrostatic pressure of a liquid column); there are additional restrictions on the height of the fuel hopper, the location of the loading hatch, etc.

A pyrolysis heating device is known (see EP 2 615 369 A1) comprising a solid fuel hopper, a gasification chamber, a pyrolysis gas combustion chamber united by a common vertically oriented housing, inside of which a spiral pipe with liquid heat carrier (water) surrounds only the pyrolysis gas combustion chamber , and the gasification chamber has a powerful thermal insulation that provides high temperature inside the chamber. The disadvantages of this technical solution are: the use of an ineffective heat exchanger circuit (liquid in a spiral pipe surrounded by hot gas) and direct contact of the liquid coolant with the red-hot walls of the combustion chamber.

A heat generator is known, consisting of two spatially spaced and connected by a common gas duct modules, in one of which there is a cylindrical loading compartment (hopper) for solid fuel and an annular gasification chamber underneath, and in the other a pyrolysis gas afterburner and a heat exchanger, while the gasification chamber made with the possibility of cooling by the air flow from an external fan (RU 132 531 U1)

This technical solution has the following disadvantages:

- placing the pyrolysis gas afterburning chamber at a large distance from the gasification chamber prevents the use of the heat of combustion of gases for heating the gasification chamber,

- the air stream cooling the gasification chamber is discharged into the surrounding space without transferring its heat to the main heat carrier in the heat exchanger

- air is supplied to the pyrolysis gas afterburner at room temperature, without heating, which reduces the efficiency of the afterburner

- the cylindrical shape of the loading compartment imposes additional restrictions on the shape and size of the wood fuel used

- the grate, performing rotational and translational (up and down) movement complicates the design, reduces its reliability and durability, because the bearing assembly and the pivot shaft are in the high temperature zone

The technical result for which the claimed utility model is proposed is to increase the efficiency and stability of the process of gasification of solid fossil fuels, including firewood and wood waste from natural (i.e., high) humidity, the most complete combustion of pyrolysis gas, increase the safety of operation of the device and reduce the complexity of its maintenance.

The specified technical result is achieved by the fact that in the pyrolysis heating device

containing a bunker for solid fuel placed in a single vertically oriented housing, below it a gasification chamber having an internal heat-resistant heat-insulating coating (lining) and a window for the exit of pyrolysis gases with a grate, and below it a pyrolysis gas combustion chamber having an internal heat-resistant heat-insulating coating (lining) , an outlet gas duct connecting the pyrolysis gas combustion chamber to the heat exchanger, as well as at least one fan installed outside the housing,

the heat exchanger is spatially separated from the hopper, the gasification chamber and the pyrolysis gas combustion chamber, the heat carrier (gas or liquid) circulating in the heat exchanger does not have direct contact with the outer walls of the gasification chamber and the combustion chamber, and the fan pumps 2- 3 times higher than required for complete combustion of the pyrolysis gas.

The flow of air pumped by the fan into the pyrolysis gas combustion chamber may previously pass through the free space (internal cavity) between the outer walls of the combustion chamber and the inner walls of the housing.

The air entering the gasification chamber can be supplied to it through an additional duct from the aforementioned cavity between the outer walls of the pyrolysis gas combustion chamber and the inner walls of the housing.

The pyrolysis gas combustion chamber can be made in the form of two compartments - symmetrical, parallel and oriented along the longitudinal axis of the casing, between which the flow of air pumped by the fan moves.

In the gasification chamber, the pyrolysis gas exit window with the grate can be displaced to the front wall of the gasification chamber, and the nozzle air supply openings can be displaced to the back wall of the chamber

A flat nozzle panel containing at least one narrow slot with sharp edges oriented along the longitudinal axis of the combustion chamber can be installed below the grate at the inlet of the pyrolysis gas combustion chamber.

These design solutions ensure the achievement of the claimed technical result and in their totality are not found in any of the known pyrolysis heating devices, thus the claimed utility model meets the criterion of novelty.

The inventive pyrolysis heating device can be manufactured on standard equipment using well-known and traditional processes and materials for the production of heating boilers. Thus, the claimed utility model meets the criterion of industrial applicability.

The device of the inventive pyrolysis heating device is illustrated by drawings. In FIG. 1 shows a General view of the device, figure 2 shows a cross section of a device in the embodiment of a combustion chamber with two compartments, figure 3 shows a longitudinal section of a gasification chamber and a combustion chamber.

The pyrolysis heating device comprises a solid fuel hopper 1, a gasification chamber 2, a pyrolysis gas combustion chamber 3, a fan 4, which supplies air to the inner cavity 5 formed by the outer walls of the combustion chamber and the inner walls of the housing, a heat exchanger 6, inside which the coolant circulates (for example, water or air) 7. The air flow from the inner cavity 5 through the duct system 9, through the nozzle holes 10 and 11 is supplied to the gasification chamber and the pyrolysis gas combustion chamber. In the window between the gasification chamber and the combustion chamber, a flat nozzle panel with a slot 12 is installed.

Pyrolysis heating device operates as follows. Solid fuel (for example, wood or wood waste of natural humidity) is loaded into hopper 1. Under the influence of gravity and as it burns out in gasification chamber 2, wood fuel is lowered down, passing through the drying zone (upper part of the hopper) and the dry distillation zone (lower part of the hopper).

The flow of air pumped by the fan 4 into the internal cavity 5 passes along the side surfaces of the combustion chamber, heating up from them, and then through the piping system 9 enters the nozzle openings 10 in the gasification chamber and the nozzle openings 11 in the combustion chamber.

In the gasification chamber with insufficient supply for the complete combustion of fuel, the so-called of "primary air" there is a flameless burning (smoldering) of wood fuel, and the pyrolysis gas formed in this case moves through a layer of hot coals to an outlet window located at the bottom of the gasification chamber, and then enters the combustion chamber of the pyrolysis gas.

The absence of cold (compared with the temperature inside the gasification chamber) coolant at the outer walls of the chamber, the presence of a heat-insulating coating on the inner walls of the chamber, as well as the powerful heat flow from below, from the pyrolysis gas combustion chamber, ensure that the required high temperature is maintained inside the gasification chamber. The separation of the combustion chamber into two compartments increases the bottom area of the gasification chamber heated by heat from the combustion chamber. The shift of the exit window to the front wall of the gasification chamber, and the nozzle openings of the "primary air" supply to the rear wall, leads to an increase in the length of the so-called "recovery zone" (space filled with hot coals, passing through which the pyrolysis gas is saturated with combustible components as a result of chemical reactions : carbon monoxide and hydrogen).

Pyrolysis gas enters the combustion chamber 3 by passing through a nozzle panel with a slot 12 having sharp edges, which leads to turbulization of the pyrolysis gas stream (numerous local turbulences occur inside the stream) and their effective mixing with the preheated so-called "secondary air" coming from the nozzle openings 11. The separation of the combustion chamber into two compartments, between which the "secondary air" moves, contributes to the intensive preliminary heating of the "secondary air". A heat-resistant heat-insulating coating applied to the inner surface of the walls of the combustion chamber provides a high temperature of the combustion flame and, at the same time, a low temperature of the external surface of the combustion chamber, which makes it possible to use ordinary structural steels for its manufacture.

The hot flue gases from the combustion chamber enter the heat exchanger, where they give their heat to the heat carrier, which can be used as water or air. At the exit of the heat exchanger, the flue gas stream enters the chimney 8 and is then released into the atmosphere.

The main difference between the claimed design and the known analogues is that almost all the heat generated in the combustion chamber is transferred to the coolant by transferring the mass of hot flue gases to the heat exchanger (unlike the traditional scheme, where a significant part of the heat is removed by convection from the walls of the gasification chamber and the chamber combustion). To achieve such a result in the claimed design, the amount (mass flow rate) of the "secondary air" entering the combustion chamber is 2-3 times greater than that required for complete combustion of the pyrolysis gas.

The technical reachability of such a solution can be illustrated by the following simplified calculation. When 1 g of wood fuel of natural (40-50%) humidity is burned, about 11-12 KJ of heat are released. For the complete burning of 1 g of wood fuel with a moisture content of 40-50%, 4.3-4.0 g of air is needed, and about 5 g of flue gases are formed. If 2.5 times more air is supplied (i.e., about 10.5 g), the total mass of the resulting flue gas will be about 11.5 g. The heat capacity of the flue gas at a temperature of 800 degrees. C is 1.2 KJ / g. Thus, 11.5 g of chimneys when they are heated from 20 to 800 degrees will be taken out of the combustion chamber by 10.8 KJ, i.e. almost all the heat generated during the combustion of 1 g of fuel.

An unusually large (usually wood-burning furnaces operate with an excess air coefficient of not more than 1.5) the mass flow of “secondary air” will lead to a decrease in the temperature of the flue gas at the outlet of the combustion chamber, from about 1400 to 800-900 degrees. C, which will inevitably affect the efficiency heat exchanger. The value of this decrease can be estimated by the well-known coefficient of efficiency. "perfect heat exchanger"

efficiency = (Tweak. - Thy.) / Tweak

The temperature of the flue gases at the outlet of the heat exchanger (for reasons of preventing condensation) should not be lower than 120 degrees C. Thus, the traditional scheme corresponds to the efficiency 91% ((1400 - 120) / 1400), and the claimed utility model - 85% ((800 - 120) / 800).

At the cost of loss of the order of 5-6% efficiency the consumer receives a heating device in which raw wood waste can be used, often having zero or even “negative” costs for it, while the traditional scheme (with heat removal from the walls of the gas generating section) forces us to buy, import and store high-quality firewood two years of drying.

In addition, we should not forget that the efficiency a real heat exchanger is always below an ideal heat-physical maximum. Since in the claimed design - unlike the pyrolysis heating boilers of the traditional scheme - the heat exchanger is a separate unit, the dimensions and geometric shape of which are in no way related to the dimensions of the gas generating section, it becomes possible to use time-tested effective solutions (for example, a vertically oriented high fire tube heat exchanger) . An excessively large amount of air in flue gases leads to an increase in their specific gravity (density) and volumetric flow rate, and hence to an increase in the speed of movement of the flue gas through the heat pipes of the heat exchanger. Both increase heat transfer (mathematically this is expressed in an increase in the Reynolds criterion, the physical meaning of the phenomenon is a greater degree of turbulization of the flow inside the flame tubes), therefore there is reason to assume that the real efficiency the heat exchanger will be no lower than the best of the existing pyrolysis boilers of the traditional scheme.

Claims (6)

1. A pyrolysis heating device containing a solid fuel hopper located in a single vertically oriented housing, a gasification chamber below it having an internal heat-resistant heat-insulating coating and a pyrolysis gas exit window with a grate, and below it a pyrolysis gas combustion chamber having an internal heat-resistant heat-insulating coating , an outlet gas duct connecting the combustion chamber of the pyrolysis gas to the heat exchanger, as well as at least one fan installed outside the housing, from characterized in that the heat exchanger is spatially separated from the hopper, gasification chamber and pyrolysis gas combustion chamber, the coolant circulating in the heat exchanger does not have direct contact with the outer walls of the gasification chamber and the combustion chamber, and the fan pumps air into the combustion chamber in an amount of 2- 3 times higher than required for complete combustion of the pyrolysis gas. 2. The pyrolysis heating device according to claim 1, characterized in that between the outer walls of the combustion chamber and the inner walls of the housing there is a free space (internal cavity) through which a stream of air is pumped by the fan into the combustion chamber of the pyrolysis gas. 3. The pyrolysis heating device according to claim 1 or 2, characterized in that the air entering the gasification chamber is supplied to it through an additional duct from the above-mentioned space between the outer walls of the pyrolysis gas combustion chamber and the inner walls of the housing. 4. The pyrolysis heating device according to claim 1 or 2, characterized in that the pyrolysis gas combustion chamber is made in the form of two compartments - symmetrical, parallel and oriented along the longitudinal axis of the housing, between which a stream of air is pumped by the fan. 5. The pyrolysis heating device according to claim 1, characterized in that in the gasification chamber the pyrolysis gas exit window with the grate is offset to the front wall of the gasification chamber, and the nozzle air supply openings are offset to the rear wall of the chamber. 6. The pyrolysis heating device according to claim 1, characterized in that the flat nozzle panel containing at least one narrow slot with sharp edges oriented along the longitudinal axis of the combustion chamber is installed below the grate at the entrance to the pyrolysis gas combustion chamber.

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