FR2880102A1 - Fluidized bed biomass combustion device for burning slurry, has pneumatic projector re-injecting non burned combustible parts and solids received from one branch of inverse U shaped combustion chamber into another branch - Google Patents

Abstract

The device has an inverse U shaped combustion chamber (1) equipped with a conical base (6) at a branch (1a), and a fluidizing plate (3) fixed in the base (6). A pneumatic projector (16) receives non burned combustible parts and solids from a base of a branch (1b) and re-injects the non burned parts and solids to the base of the branch (1a). A recycling fan (14) permits to maintain combustion temperature at low value.

Description

1 2

  Fluidized bed biomass combustor 4 - The present invention allows various fuels to be burned to produce heat energy by heat recovery from the flue gases.

  6 - It is described. in detail. in the case of biomass combustion alone. then it is indicated. How? 'Or' What.

  7 without significant changes. this invention makes it possible to burn sludge mixed with S or biomass. other products. notably, meat products.

  9 - Combustion device to burn only biomass I I) - Currently_ thermal energy used in the world is produced. essentially_ by fossil fuels.

  12 - The fossil fuel deposits have a life time that. according to the greatest specialists.

13 will not exceed two hundred years.

  14 Their combustion produces greenhouse gases and ash-laden fumes containing heavy metals. ash that must first be collected by expensive devices and then evacuate in controlled dumps where they are received at high prices.

  17 - Biomass, when burned, provides renewable energy 18 - The amount of carbon dioxide captured during the natural production of biomass corresponds to the amount of carbon dioxide released during its combustion.

  - Its combustion produces little ash. less than 2% of its mass for wood felled in the forest.

  21 - In developed countries as is France. as a result of the displacement of rural populations towards the city and the improvement of agricultural productivity, the forest is becoming more and more covered.

  24 - Biomass deposits are expanding and their reasoned exploitation makes it possible to preserve the accessibility and aesthetics of wooded areas.

  26 - For these reasons. France and the European countries are waiting to see the development of new technologies to make the combustion of biomass more economical.

  28 - Boilers of medium or high power burning biomass. currently available on 29 the market. are of an old design.

  3t1 - The implementation of these boilers entails heavy investments and operating and maintenance costs. high.

  2 - Boiler manufacturers in France who were among the best in the world. victims of the competition from the countries of Eastern Europe. have virtually disappeared.

  4 - Large European industrial groups are no longer investing in the search for innovative solutions for burning biomass.

  6 - All these reasons pushed THEL-ETB to look for and to invent the combustion device 7 which is described in the present text.

  8 - The combustion device is economical in installation and operation.

  9 - It is not polluting because the combustion is carried out at low temperature with a strong excess of air.

  It is designed with little mechanical equipment without a grate in the combustion chamber. I 1 - The device consists of: 12 - A combustion chamber 13. It is equipped: 14 - At its base, a plenum 2 where the combustion air is mixed with recycled fumes after cooling in a boiler by recovering the sensible heat they contain.

  16. The controlled mixture of combustion air and recycled fumes controls the temperature of the combustion chamber by keeping it at low values.

  18 - A fluidization plate 3 made of refractory materials. of a lower section than that of the combustion chamber, placed in a refractory steel piece, bolted to welded flanges.

  one on the walls of the lower part of the combustion chamber. the other on the walls of the upper part 21 of the combustion air intake plenum.

  22 - This piece once unbolted can rotate around a vertical axis 4 to exit the assembly 23 combustion chamber. plenum. allowing easy intervention on the fluidization plate.

  24 - The fluidization plate comprises vertical injectors of combustion air distributed over its surface. injectors allowing after shutdown of the fans of combustion and recirculation of 26 fumes. to the circulating mass of calibrated products, in its downward fall, to cross the 27 injectors and come to collect in the hopper 5 at the base of the plenum.

  This fluidizing plate design is protected by the THEL-ETB patent. N 0212832000 29 - The combustion chamber of circular section, inverted U-shaped. contains the flow of combustion gases mixed with balls of expanded refractory material, balls carried by the flow of 1 gas, combustion and combustion air.

  2 - The conical shape of the base 6 of the combustion chamber located above the fluidization plate 3 allows the following operating modes: 4 - Starting phase before combustion or "hot" waiting phase - The flow rate of Air injected into the plenum, passing through the fluidization plate, keeps the expanded balls in the conical portion 6 of the base of the combustion chamber and prevents the balls from passing through the fluidizing plate into the plenum.

  9 - The burner 7 placed in the air stream of the combustion air supply door. at startup, the combustion chamber at the temperature chosen to allow ignition 11 of the fuel in the combustion chamber.

  12 - Low combustion loads 13 - The balls are carried by the flow of combustion gas which. remaining weak. holds them 14 in the lower part of the combustion chamber.

  - The fluidized bed constituted by the balls and the combustion gases. is a fixed bed 16 - Medium and high combustion loads 17 - When one increases, gradually, the heat load, the speed of circulation of the 18 gases in the combustion chamber increases with the increase of the load. to reach a rate such that the lift forces acting on the base of the balls drive them upwards to the top of the first branch la of the U-shaped combustion chamber. Arrivals at the summit. they descend downwards 22 into branch 1b. driven by the gas flow but also by their gravity.

  23 - In the lower part of the second branch of the combustion chamber. the gas flow 24 containing the circular balls and the ashes of the combustion, meets, first. a device for refocusing the balls 8 constituted by a grid formed of axial bars in the form of an inverted cone (upside down) with an angle chosen to allow the descent by gravity of the balls. The circular center 9 of the cone is free to allow the passage of the balls 28 once they have been recentered 29 - This inverted cone is extended by a cylinder whose walls are grid.

  - The flow described. above. crosses the centering device as follows: 1 - The combustion gases and fine ash pass through the grids of the cone and the cylinder 2 whose bars are sufficiently spaced to pass them.

  3 - The unburnt balls and fuel parts. can not cross the grids 4 and are gathered in the center of cone left free. They fall. then, by gravity by the cylinder in the feed hopper of the designer described. below. whose role 6 is to reinject the balls into the combustion chamber.

  7 - The flow of the combustion gases separated from the balls, is directed by the outlet of the combustion chamber 10 located on the lower part of the second part of the combustion chamber.

  9 to the recovery boiler Whenever the fumes cool down, then. to the flue gas treatment device 12. and, finally, to the exhaust fan 13 which pulses them into the chimney.

  12 - This combustion chamber design makes it possible to separate the combustion gases from the 13 balls without resorting to a cyclone, and therefore. provides little pressure drop 14 during the flow of gas.

  Part of the fumes cooled by the boiler are taken up by the recycling fan 13 to enable the combustion temperature to be controlled and by the fan 17 of the pneumatic blower.

  18 - By the pneumatic designer 19 - The pneumatic projector 16 powered by the fan 15 sucking a portion of the cooled fumes so that there is no risk of ignition in the projector. receives. in its first part. from above, with a rotary distributor 17, the unburnt logs and fuel parts from the base of the second branch of the combustion chamber. hopper base.

  24 - In the second part of the designer. thanks to a progressive and adjustable system 18 (screws, pushers, squeegee conveyor, etc.) is introduced. Above. the biomass prepared to have the appropriate particle size at its introduction (sawdust.

  27 crushed. plates, etc.) 28 - The designer reinjects logs and fuel into the combustion chamber to allow continuous operation.

  3o. It is designed with a horizontal sole on which the mass of the balls 1. The stop of the pneumatic supply. immediately interrupts the supply of fuel 2 to the combustion chamber 3 - This type of projector is protected by the patent THEL-ETB No. 0212832000 4 - To isolate the designer, during unplanned or programmed shutdowns of the machine_ two hatches 19, 20 actuated by cylinders, are closed.

  6 - The combustion device used to burn biomass with sludge 7 or other waste

8 - The description remains the same

  9 - As it is waste. it will be necessary that the characteristics of the combustion device in particular the combustion temperature. the length of the combustion chamber as a function of the flow rate of the flow of the combustion gases and the balls. allow to comply with the regulations in force for the waste (currently for ordinary waste, 850 c, 2 seconds in the combustion chamber 13 with at least the presence of 6% of 02 in these ci) 14 - sludge . before their introduction in the designer. will be mixed with biomass.

  - For liquid waste. For example, the solid parts included in the liquid must be finely comminuted.

  17 - The introduction will be done directly by spraying. at the base of the first part of the combustion chamber.

  19 - When the products to be burned will have significant percentages of sterile material. sterile generating ash during combustion, the first part of the designer will be modified.

  21 - It will have a sole that will be formed of a grid for passing the fines combustion residues and not the balls.

  23 - The base hopper of the combustion chamber and the first part of the pneumatic projector 24 will be mounted on a vibrating table 21 generating an alternating movement favoring the descent of the balls and the evacuation of fine products through the grid.

  26 - More. to avoid collages on the walls of the boiler tubes. the flue gas temperature at the outlet of the combustion chamber will be lowered to approximately 600 ° C. by reinjection into the combustion gases before the boiler, of a flow rate of cooled fumes taken after the recovery boiler.

  -6- 2880102 Examples of operation of the combustion device Operation of wood alone Designation of unit fuel used wood wood wood wood wood wood flow t / h 2 1 0.5 2 1 0.5 percentage of moisture wood% 35 35 35 50 50 50 flow stochio combustion air '' '' 5828 2914 1457 4483 2241 1121 excess air flow rate 3697 1748 874 2690 1345 672 combustion temperature (1 = 850 850 850 850 850 850 recycled flue gas flow rate 8116 4057 2028 4317 2160 1078 flue gas flow 19115 9556 4778 13352 6677 3337 flue gas temperature boiler output "g '150 150 150 150 1.50 150 flue gas composition CO2 N"' 3'h 2077 1038 519 1359 679 340 H20 2960 1480 740 2785 1393 696 N2 12802 6400 3200 8374 4188 2093 02 1276 638 319 835 417 209 total 19115 9556 4778 13352 6677 3337 outlet temperature fumes C 150 150 150 150 150 150 quantity of 02 in the chamber of% 14.3 14.3 14.3 15.5 15.5 15.5 combustion quantity of 02 in the fumes% 6.7 6.7 6.7 6.3 6.3 6.3 Puissanc e useful boiler output kW 5593 2796 1398 3935 1968 983 Combustion efficiency 82 82 82 75 75 75 speed of circulation of gases in furnace 111'seC 6 6 6 6 6 6 Diameter dufour m 2.15 1.52 1.08 1.80 1.27 0.90 -7- 2880102 Examples of combustion device operation Combustion wood and sludge waste water Designation unit fuel used wood wood wood sludge sludge sludge wood flow t / h 2 1 0.5 sludge t / h 2 1 0.5 moisture content wood 4, 35 35 35 sludge% 80 80 80 combustion air flow stoichi "'' '' 1 '6801 3401 1700 excess air flow" ", 3h 5441 2720 1360 combustion temperature 850 850 850 recycled flue gas flow' 'm' ' 2730 1364 681 flow rate filmed 18000 8999 4499 fl ows boiler output d 150 150 150 _temperature flue gas composition CO2 1644 822 411 H20 4515 2257 1128 N2 "310494 5247 2623 02" n3 h 1347 673 337 total "'"' '18000 8999 4499

_

  quantity of 02 in the chamber of% 18.5 18.5 _ combustion 18.5 quantity of 02 in the fumes% 7.5 7.5 7.5 Output power boiler output kW 5321 2660 1330 Combustion efficiency% 67 67 67 velocity of the gas flow in oven nuszc 6 6 6 Diameter dufour m 2,09 1,48 1.

045 Examples of combustion device operation Combustion wood and paper sludge Designation unit fuel used wood wood wood sludge sludge sludge wood flow t / h 1.5 0.75 0.40 sludge t / h 3 1.5 0.75 moisture percentage wood% 35 35 35 sludge% 50 50 50 combustion air flow stochio Nm3h 8025 4011 2078 flow rate of excess air N '' 3 '' 6417 3208 1662 combustion temperature 'z 2 850 850 850 recycled flue gas flow rate Nm 8050 4025 2098 filmed flow rate No. 23221 11610 6043 flue gas temperature boiler output 150 150 150 flue gas composition CO2 \ m3'1 2518 1259 653 H20 Nm3ih 5594 2797 1432 N2 "113 '' '13045 6523 3423 02 2063 1031 535 total Nn'3ih 23221 11610 6043 quantity of 02 in the chamber of% 16.7 19.7 16.6 combustion quantity of 02 in the fumes% 8.9 8.9 8.9 Power output boiler output kW 6916 3458 1798 Efficiency combustion% 0.74 0.74 0.74 speed of circulation of gases in furnace n, aec 6 6 6 Diameter dufour m 2,3 7 1.68 1.21 Examples of operation of the combustion device Combustion raw meat Designation unit fuel used raw raw raw flow t / h 5 2.5 L25 moisture percentage cm 64 64 64 combustion air flow stochio N'n " m 10814 5407 2704 flow rate of excess air N "'', '' 6489 3244 1622 combustion temperature '' 850 850 850 flow rate of recycled fumes> hn ^, '4645 2318 1158 fume flow rate'" h 26939 13465 6731 boiler flue gas temperature 150 150 150 flue gas composition CO2 N "" '' 2107 1053 527 H20 Nm3.h 6669 3334 1667 N2 N2 h 16516 8255 4127 02 Nm? h 1646 823 411 total Nn'3 / h 26939 13465 6731 quantity of 02 in the chamber of% 17.8 17.8 17.8 combustion quantity of 02 in the fumes% 6.1 6.1 G.

1 Output power boiler output kW 7898 3948 1974 Combustion efficiency% 0.68 0.68 0.68 Circulation velocity of gases in kiln 6 6 6 Oven diameter m 2.56 1.81 1.28

Claims (3)

1 Claims,   2 1) Combustion device characterized by the combination of the following features: 3. the combustion device consists of an inverted U-shaped combustion chamber (1) composed of two vertical cylinders (1a) and (1b) ) connected to their summit.   5. At the bottom of the first cylinder (la), where the combustion air is blown, is located a fluidization plate (3) 7. A solid charge constituted by refractory material balls is carried by the air and the 8 combustion gases.   9. At low load the bed is fixed .. A medium and high load, it is circulating 10. It travels, then, the entire combustion chamber (1) inverted U-shaped.   1. At the end of the combustion chamber (1), at the bottom of its second cylinder (1b), the solid charge 12 separates from the combustion gases and ashes which flow towards the recovery boiler (11), the smoke treatment (I2) and chimney.   14 - The solid charge, balls and unburned fuel parts, falls into the hopper of a pneumatic jet which reinjects them at the base of the first cylinder (la) of the combustion chamber (1), above the grid fluidization (3).   17 - The combustion stream comprising the solid charge constituted by balls of refractory material, the fuel and the gases, circulates in the combustion chamber without the need to pass through a cyclone to separate, at the end of combustion, the gas solids, cyclone which increases the losses to be overcome by the combustion fan 21 2) Device according to claim 1 characterized by a cone-shaped device (6) at the base 22 of the combustion chamber (1), above the fluidization plate (3), allowing the combustion chamber to operate in fixed flow at low load, and in medium and high-load flow 3) Device according to claim 1 or 2 characterized by a device, at the end of combustion, 26 constituted by a part composed of an inverted cone (8) extended by a cylinder (9), cone 27 and cylinder whose walls are grids channeling the balls and the non-burned solid parts downwards where the hopper of the pneumatic jet is located and allowing the combustion gases and ashes flowing to the recovery boiler (11) to pass through, the flue gas treatment (12). ) then the chimney