FI98854B - Procedure and burner for combustion of fluid and solid materials with broad particle-size distribution - Google Patents

Description

98854 ·

METHOD AND BURNER FOR COMBUSTION OF LIQUID AND WIDE PARTICULATE8 SIZE KZINTBIDES

The invention relates to a method for the combustion of liquid solids with a wide particle size distribution in a controlled manner using a vortex chamber, in which the substance is fed into the vortex chamber tangentially together with the air flow and thus generates a vortex, which provides a selective delay time for coarse particles. The invention also relates to a burner implementing the method.

Conventional flame combustion of powdered materials has been based on grinding the combustible material into fine dust which has been burned in a flame formed outside the actual bulb. The maximum delay time allowed for flame combustion, i.e. the time in which the particle must have time to burn completely, is clearly less than 1 second and usually only a few tenths of a second. In order to stabilize the flame and keep the flame length reasonable, the combustible material had to be ground to a size of less than 0.1 mm. Grinding has taken place in a separate mechanical mill. Grinding biofuels to a particle size suitable for flame combustion is much more problematic than, for example, grinding coal.

*. Grinding biofuels suitable for dust combustion consumes. 25 energy 1-5 KJ / kg, which is economically quite ·. too much. Milled peat must also be ground before it can be used for flame combustion. Especially in smaller units \ dust combustion, which requires efficient grinding, has been • economically uncompetitive and has also had to be applied quite a bit: 30 expensive fluidised bed incinerators. It can be said that the lack of a cheap combustion technology solution has been one of the factors that has weakened the economic competitiveness of peat and biofuels.

»·· • · ...

.. 35 The problem with dust combustion is the short reaction time of the particles, which “* means that the material to be combusted has to be ground very finely.

Stability conditions for dust burners are strict due to the very low mass of the ignition zone. Adequate and even dryness of the combustible dust is also a condition for stable combustion. For safety reasons, dust burners usually need to be secured with support flames using oil or ^ 000 ^ 2 gas. Dust combustion systems thus require drying, grinding, stabilization burners and the actual dust burners of the material to be burned. In small units, such a system is not economically competitive.

5

The incineration method, which is already known and has been applied quite widely in practice in the past, is sulasyklonipoltto. In cyclone burners, all the combustion air is introduced into the cyclone and they have generally operated at such a high temperature that the ash accumulated in the cyclone 10 has been removed as a melt. The problems with cyclone burners have been e.g. temperature control. Too low a temperature has led to an uncontrolled growth of the slag layer accumulating on the walls of the cyclone, and at high temperatures the service life of the protective liners of the cyclone has remained too short. Due to the large number of patients with combustion heat-15, the nitrogen oxide emissions of cyclone burners are also high and exceed the permissible emission limits. For these reasons, cyclone combustion is hardly used anymore.

A solution has been sought to the costs 20 and technical problems of the dust and cyclone combustion described above, e.g. fluidized-bed technology. Unfortunately, however, despite advances in fluidized bed technology, it appears that its economic competitiveness remains poor in small units. The fluidized bed technology is divided into so-called bubbling fluidized bed (BFB) and 25 circulating mass technology (CFB). In the latter, a large stream of solids passes through the combustion chamber, which is separated in a cyclone and returned to the lower part of the vertical combustion chamber. CFB combustion requires complex equipment that includes an air distribution chamber with nozzle bottoms, a vertical reaction chamber, a cyclone, and 30 solids recovery equipment. CFB incineration and cyclone incineration thus have in common that both techniques include, as an integral part, a cyclone to provide coarse particle selection. tight delay time. In CFB combustion, the particle delay time is determined. primarily according to the conditions of the vertical chamber (riser).

35 In cyclone combustion, the particle delay time is formed solely by ‘cyclone conditions’. Another essential difference between CFB combustion and: conventional cyclone combustion is the amount of solids stored in the system. In CFB combustion, the solids content of the system is 98854 3 very much higher than in cyclone combustion, and almost without exception, CFB combustion uses other solids in addition to fuel, which form the bulk of the system solids. The purpose of the high solids content is to improve the stability of the system and, in some applications, to reduce emissions. It is clear that CFB combustion does not operate above ash sintering temperatures. In cyclone combustion, the amount of solids is very small and the burners usually operate in the molten ash area. Both combustion techniques have obvious advantages and certain uniformities. The question therefore arises as to whether it is possible to combine the technical simplicity of cyclone combustion with the process technical advantages of CFB combustion. This invention relates to a process in which the key advantages of a CFB reactor are achieved in a simple vortex chamber. Poor quality liquid fuels also pose a technical problem with combustion-15. The present invention seeks to solve these problems of known telenics.

The characteristic features of the method according to the invention are set out in the appended claim 1 and the characteristic features of the corresponding burner are set out in claim 6. Other advantages and embodiments of the invention will become apparent below.

: The process according to the invention makes it possible to burn coarse fractions, solids and poor quality liquid fuels: 25 efficiently and at low cost. In the method according to the invention, the vortex chamber is used for the simultaneous chemical and physical processing of the material to be treated.

. Later, the invention is referred to as a description of its operation

Chemi Mechanical Reactor (CMR), which works as follows. Coarse-30 fraction fuel is fed with oxygen-containing gas to the CMR. The oxygen to fuel ratio is clearly regulated • .....

on the sub-stoichiometric side so that the temperature in the CMR *: is preferably between 600 and 750 C. Typically, air is used as the oxygen-containing gas, in which case the CMR is controlled ».

. 35 The amount of air flow for dry fuel is 30-50% of the amount of air that is completely burned. Oxidizing gas is brought to CMR • ......

“Tangentially, creating a vortex in the CMR that prevents coarse particles from leaving the CMR. As a result, solid material enriches the 4 yo CHR, which circulates strip-like along the sheath of the CMR. Under the influence of the internal vortex of the CMR: the temperature-fragile particles collide with each other and with the walls of the CHR and thus grind into finely divided particles. When the particles fall below a threshold depending on their physical state, they leave the CMR. The CHR vortex is adjusted to allow the passage of particles with a sufficiently short reaction time in flame combustion. In CMR, the residence time of large particles becomes large, while the finely divided material is rapidly removed from the CHR. It is clear that such a selective residence time is advantageous for combustion.

Based on the above, the following advantages are achieved in the CHR: 15 1. Thanks to the rich solids circulation and the sub-chiometry, the temperature control is easy and precise.

2. The solids vortex formed inside the CHR compensates for the circumferential temperature differences and protects the structure from overheating.

20 3. With the chemical and thermal treatment of the combustible material, the energy consumption required for grinding is insignificantly »· • · reduced.

4. The amount of solids accumulating inside the CMR stabilizes the flame V for sure, so no support combustion is required.

‘I 25 5. A high power density (MW / m3) is achieved in CMR.

i.v 6. Organically bound nitrogen is released under reducing conditions, thus minimizing the formation of nitrogen oxides.

7. CHR can be implemented as a non-cooled steel structure without material problems.

30

The burner according to the invention can also act as a carburetor. In this case, • e ... it is better to talk about the reactor instead of the burner.

e ........ ...............................- · · e e ......

• .....

«................ '-.- s- ·" ·' · '

The invention will now be described with reference to the accompanying figures, which show a burner according to the invention.

Figure 1 shows a side view of the burner in partial section.

98854 5

Figure 2 shows a cross-section of the bulb of Figure 1 from point II-II.

Figure 3 shows the parts of the burner in an axonometric view.

Reference numeral 1 denotes a vortex chamber (CMR chamber) into which the fuel is introduced by means of carrier air from a pipe 11 together 12 through a direction tangential to the vortex chamber 1. The end of the vortex chamber 1 has a flange 8.1 with which it is attached to the end 8.2 of the secondary chamber 6. Through these ends 10 an outlet pipe of the vortex chamber, designated as intermediate channel 4, is placed. This extends somewhat into the secondary chamber 6. At one end, the outlet channel 5 of the secondary chamber 6 extends partially over the channel *, whereby an annular gap channel is formed. Secondary air is introduced through a pipe 2 and a joint 3, which is also oriented parallel tangentially to the unit 12. The burner is fixed, for example, to the boiler wall from a flange 7.

In order to ignite the burner, electric resistors 22 and an oil nozzle 9 are connected around the vortex chamber 1. Naturally, gas can also be used for igniting 20. Vortex chamber 1. in the middle of the front end there is a thermocouple protection tube 21, which ··· · • j. in the thermocouple itself is installed to measure the temperature of the vortex chamber .V l (CMR chamber).

m · • · .....

9,099 9 .....

** I 25 In Figure 3, the vortex chamber and the secondary air system are separated and the vortex chamber 1 is rotated about 90 * relative to the situation in Figures 1 and '·' * 2. The intermediate tube 4 is here attached to the flange 8.2 of the second chamber 6 and for this purpose the flange * 8.1 of the vortex chamber 1 has a hole 15. Figure 3 does not show electrical resistors, 30 temperature sensors or an ignition burner.

* ......

• 09 '.......

• · · • 9 · ...... ......

The main dimensions of a pilot unit and 2 MW burners are as follows: »e ......

··· 0 ........... y ': \.

Pilot 2MW Unit 35 CMR chamber diameter 200 800 mm CMR chamber length 150 600 mm

Exhaust pipe diameter 50 225 mm 98854 6

Sawdust properties:

Water / dry matter mass ratio 0.06 0.06

Maximum particle size 5 5 mm

Avg. particle size 1 1 mm 5 -:

Airflow to CMR / stoichiometric airflow:

Minimum 0.4 0.35

Maximum 1.2 1.2 10 Bite feed:

Maximum 4.0 110 g / s

Minimum 1.7 20 g / s

Minimum power density 5 1.33 MW / m3

Maximum power density 11 6.6 MW / m3 15

Flame length:

Maximum 400 mm

Minimum 150 mm 20 In the vortex chamber 1, i.e. in the CMR chamber, the air volume of the substoichiometric combustion is controlled so that the temperature is between 600 and 7501 C. This generally corresponds to 25-35% of the oxygen consumption taking place in the vortex chamber. It is essential that the secondary air flow is a concentric ring flow, most preferably it is a vortex ring flow around the primary flow as shown. It is also important that the outlet channel 5 is so close to the end 8.2 that a pressure drop occurs between them, which equalizes the ring flow.

The length to diameter ratio of vortex chamber 1 (CMR chamber) is: most preferably between 0.8 and 1.2. The length of the secondary chamber 6 is. most preferably 30-50% of the length of the vortex chamber chamber l. The intermediate ».. ----------------, the channel 4 and the secondary chamber outlet channel 5 most preferably overlap by 20-30% of the diameter of the intermediate channel. The diameter of the intermediate channel 4 is: most preferably 25 to 35% of the diameter of the vortex chamber 1.

: 35 "...... ...

In the vortex chamber, i.e. the CMR reactor, it is not primarily a question of separation, but of processing the solid particles into a gaseous 98854 7 compound and small coke particles. These all exit the vortex chamber through the intermediate channel.

In some cases, it is preferable to use an inert granular material in the vortex chamber that improves the grinding of the solid fuel and increases the heat capacity of the chamber to even out combustion. The use of an inert substance can often be arranged so that it is fed only to the extent that it leaves the vortex chamber to a small extent.

10> · I · I · • · »·» · • · »· · · · ...... ......

·· • · • · »· ........

> · • »• · .........

• · m · .....

· • e »· • ·» · ·· • · .....

• .... .....

• 9 • ».......... ·· · · • ..... ..... 1 2 · ..... ......

2 ... ........ ..... ...... '

Claims (11)

A method for controlled combustion of liquid and of seed solids having a wide particle distribution, by means of a cyclone chamber, according to which the method is measured tangentially in the cyclone chamber (1) together with the air stream and the material stream is swirled away from the center, characterized by. that between the tangential feed stream and the central a feed stream a vortex is generated, with which a selective delay time is obtained for the coarser particles so that the size of the outgoing particles decreases to a size which is smaller than the set limit size and the air feed is divided. in two phases, during which, in the first phase, the substance to be burned is measured together with a sub-geometric amount of air in the cyclone chamber (1) while maintaining the temperature below the ash melting point and during the second phase a secondary air stream is supplied in an annular stream with the same center around the current flowing out of the cyclone chamber. 20 2. A process according to claim 1, characterized in that the ratio of oxygen to fuel in said first sub-stoichiometric combustion is regulated such that the temperature ϊ is between 600 - 750 ° C. • ·· • · · Λ | 1 '··· '"..... ·. · 125 • ·' ·" .......... ·: 1 3. A process according to claim 1 or 2, characterized in that 25 - 35% of oxygen consumption takes place in the cyclone chamber. • 9 9 ·· "9 9 9. .............. ····" ' Method according to Claim 1, 2 or 3, characterized in that the secondary air stream is formed as a vortex with; v the same center and in the same direction as the primary stream. »·· • __________ ··· ......... • · 1 _______ .... —..... '............ \ 1 5. A process according to any of claims 1 to 4, characterized in that inert granular material is also fed into the cyclone chamber. 999. ...... • .. ..... -. · - · '··· ..... .111 A burner for carrying out the method according to claim 1, which comprises a cylindrical cyclone chamber (1) with tangential fuel and air connections (11) and a central discharge channel as below. is referred to as intermediate channel (4) / Characterized by. said burner comprising a secondary chamber (6) arranged with the same center after the cyclone chamber (1) / which secondary chamber comprises a tangential secondary air coupling (3) and an outlet duct (5) having the same center, and said intermediate channel (4) extends to a portion from the secondary chamber (6) as the secondary chamber discharge channel (5) extends from the opposite end partially to the intermediate channel (4), forming an annular space for the secondary air flow supply around the main stream. Burner according to claim 6, characterized by. that the ratio between the length and diameter of the cyclone chamber (1) is in the range 0.8 - 1/2. Burner according to claim 6 or 7. characterized in that there is electrical resistance around the cyclone chamber for heating the cyclone chamber and further in the primary air connection an oil / gas nozzle for igniting the burner. Burner according to claim 6, 7 or 8, characterized in that the length of the secondary chamber (6) is 30 - 50% of the length of the cyclone chamber (1). ··· ..... *, · 125 ...... . .. · 10. Burner according to any of claims 6 - 9, characterized in that the intermediate duct (4) and the secondary chamber output | : 2 · Thread channel (5) overlaps each other by 20 - 30% of the diameter of the intermediate channel II. • e e. . . . 30 Burner according to any of claims 6-10, characterized by. that the diameter of the intermediate channel (4) is 25 - 35% of • ♦ ♦ .................... - ··· - * · 1 2 cyclone chamber (1) diameter. · # 1 # ♦ ..... e · - ...... 3:35 · # ♦ ee 2 • -------------- 3 • e • e ♦