FI65666C - ANORDNING VID UGN - Google Patents

Description

This invention relates to an arrangement for burning a solid fuel such as logs, coke, coal and the like, comprising a primary combustion chamber and a secondary combustion chamber, each combustion chamber being provided with a separate combustion air supply.

In previously known furnaces of this type, attempts have been made to achieve the afterburning of incompletely burned gases by introducing secondary air into them in the combustion chamber. However, measurements 10 have shown that this desired effect is rarely achieved in smaller furnace units, and that it is due to very favorable coincidences in these cases.

Due to recent signs of future energy shortages, there has been a growing interest in using forest-based timber as a heat source for housing. In this connection, there is a need for an environmentally friendly furnace for burning forest timber and the like, which has the highest possible efficiency and can be controlled as well as possible.

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Such a furnace is characterized in that the fuel undergoes partial (pyrolytic) combustion at a relatively low temperature in the primary chamber. In this process, flammable gases (pyrolysis gases) are released at a rate determined by temperature and the form and composition of the fuel. The temperature of the primary chamber depends on the rate of combustion taking place there, i.e. the combustion air supply and the thermal insulation of the primary chamber. The possible total energy output of the furnace is thus the sum of the primary combustion intensity and the calorific value of the pyrolysis gas. Controlled power consumption means that the pri-30 amount of air and the primary chamber insulation must be adapted to the respective fuel.

In order to ensure complete combustion of the pyrolysis gas and thus to obtain a high efficiency, it is necessary to introduce secondary air into the gas by controlling the conditions in terms of quantity, temperature and retention time. Combustion can most efficiently take place in a separate secondary chamber with adapted heat release and air supply.

It is therefore an object of the present invention to provide a furnace for burning solid fuel in which combustion takes place in two stages, namely first in the primary chamber and then in the secondary chamber in a manner which ensures high efficiency in the furnace and further arranges the furnace to allow controlled combustion.

This is achieved according to the invention, above all, by the arrangement of the furnace mentioned in the preamble, characterized in that both chambers 15 are thermally insulated, usually that the secondary chamber is better thermally insulated than the primary chamber and that the secondary chamber is formed as a two-stage chamber. to allow complete combustion over a high power range-la.

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The size of the optimal secondary chamber depends on the power output of the furnace. The two-stage secondary chamber thus ensures good secondary combustion over a large control range, since low-power combustion takes place in the first stage, while it is completed at a higher stage in the second stage.

The invention will be explained in more detail below with reference to a schematic drawing showing an embodiment of the invention.

The furnace according to the invention consists of a primary chamber 1 which is at least insulated from the roof 2. However, there is no obstacle to the fact that the walls can also be insulated, as this would be necessary to increase the temperature in the primary chamber in order to achieve the desired flue gas velocity. The combustion air entering the primary chamber is sucked into the si-35 weather through the draft openings at the front of the furnace.

The combustion gases coming from the primary chamber 1 are led into the secondary chamber 6 through an opening 5 in the rear wall 3. This is formed as a two-stage chamber in which low-power combustion continues in step 1, while high-power combustion is completed in step 2. Combustion air in the secondary chamber is drawn in simultaneous control of primary and secondary air is obtained. The duct 8 is insulated against the primary chamber, as can be seen from the drawing, but is provided with a heat transfer panel 9 against the duct 10 coming out of the secondary chamber. The secondary chamber is very well thermally insulated so that a sufficiently high temperature (750-1000 ° C) can be achieved in the secondary chamber. In order to ensure that the combustion gases ignite and burn completely in the secondary chamber, i.e. that the temperature rises above the ignition temperature of the gases, 13 energy elements 12 with an additional energy supply can be used. . Instead of being placed in the secondary chamber itself, the heating element may be located in the supply channel 8 of the secondary chamber. The secondary chamber may also be provided with plates, rods or the like having a certain thermal inertia, whereby the ignition of the combustion gas takes place more easily than in a free gas atmosphere. It will be appreciated that the arrangement of thermocouples, catalysts or thermally inertial rods or the like may be utilized individually or in combination.

The warm gases from the secondary chamber 6 are led out through the outlet 10 and turn around the front edge of the roof 11 and pass through a duct 13 on the upper side of the roof 11 to the chimney 14. The flue gases from the outlet of the duct 10 give off as much heat as possible .

A chimney 15 can be arranged in the chimney 14, which can receive current from a thermoelectric element 16 arranged on the roof surface of the duct 13. This thermoelectric element releases current depending on the temperature difference between the support surface against the hot surface and the environment. The fan 15 can be controlled by a room thermostat, whereby the supply of combustion air becomes dependent on the desired indoor temperature. The start-up of a cold furnace can be performed with a buffer battery, as the thermoelectric element does not give off any current, or with natural barrel draft.

No extra power to the secondary chamber is needed at all times. The following parameters can be used to control this te-10 power supply: a) Temperature in the secondary chamber. If this falls below 800 ° C, power is required, provided that there is a continuous flow of fuel gas from the primary chamber. The temperature sensor can then be installed in the secondary chamber.

15 b) Temperature rise from secondary chamber inlet to borehole. A positive value for this, not due to an extra energy supply, indicates that there is a constant supply of combustible fuel gas.

c) The temperature is measured in the chamber. The low limit value indicates that there is no more fuel in the furnace and that there is no need to import 20 extra energy.

The combination of these parameters, for example in the form of electrical signals from thermocouples, thermistors or the like, makes it possible to ensure fully automatically that all 25 combustion gases are burned.

Claims (1)

An arrangement in a furnace for burning solid fuel such as logs, coke, coal and the like and comprising a primary combustion chamber (1) and a secondary combustion chamber (6), each combustion chamber (1,6) being provided with a separate combustion chamber (1,6). combustion-5 air supply, characterized in that both chambers (1,6) are thermally insulated, usually so that the secondary chamber is better thermally insulated than the primary chamber, and that the secondary chamber (6) is formed as a two-phase chamber comprising two chamber parts (6) and 10) to allow complete combustion in the 10 high power range.