Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23B—METHODS OR APPARATUS FOR COMBUSTION USING ONLY SOLID FUEL
  • F23B90/00—Combustion methods not related to a particular type of apparatus
  • F23B90/04—Combustion methods not related to a particular type of apparatus including secondary combustion
  • F23B90/06—Combustion methods not related to a particular type of apparatus including secondary combustion the primary combustion being a gasification or pyrolysis in a reductive atmosphere

Definitions

• the invention relates to a method for burning inferior fuels, in particular based on lignite.
• the combustion takes place for the production of high pressure steam using the principle of pre-firing and the smoldering gas combustion for the substitution of the high-quality fossil fuels previously used.
• the process is used without changing the existing, previously used high-pressure steam generators.
• Inferior fuels are burned according to the principle of pre-firing and smoldering gas combustion.
• pre-firing and smoldering gas combustion For this purpose, several, for example three, pre-firings with the same function are operated in parallel.
• the pre-firing is supplied with uncontrolled primary air during the charring.
• the fuel is fed into the pre-firing from above and moistened with a humidification system.
• a flame tube arranged above or to the side of the grate, the fuel is charred with simultaneous ignition of the carbonization gases.
• Several pre-firings are necessary for effective operation of the high pressure boiler.
• the hot smoke and smolder After passing through the flame tube, gases are fed individually to a flue or smoldering gas collecting duct.
• the smoldering gases of all pre-firings connected in parallel are brought together in this collecting duct.
• Secondary air is also supplied via the carbonization channel.
• the residual molten gas mixed with the secondary air and flue gases is introduced into the actual high-pressure steam generator, for example a two-pass boiler, via a swirl rosette.
• the cooling circuits of the flame tubes can be connected in parallel and integrated into the boiler circuit of the steam generator on the water side via corresponding supply lines and on the steam side via corresponding discharge lines.
• a forced fan is inserted behind the steam generator and a by-pass control is provided.
• the method permits the combustion of the inferior fuels mentioned, the energy yield does not correspond to the yield that would be expected on the basis of the calorific values of the fuels used.
• the specified method at least one third of the carbonization gases generated are already burned in the pre-firing or in the downstream flame tube. This leads to a relatively high additional consumption of fuels in relation to the output in the steam generator.
• Another disadvantage of the specified method is poorly controllable and thus spontaneous charring or combustion both in the pre-firing and also in the actual steam generator. In the past, oversized pre-firing with increased investment costs has been used to eliminate these disadvantages.
• the aim is to specify a process with which the optimal combustion of low-quality fuels is possible in conventional high-pressure steam generators, which were previously operated with high-quality fossil fuels.
• the task is to burn low-quality fuels in conventional high-pressure steam generators using appropriate pre-firing according to the principle of smoldering gas afterburning, the smoldering gas afterburning taking place largely in the steam generator.
• the low-quality fuels are first burned in a plurality of preheaters with the same structure, connected in parallel, independently of one another, the operation of all existing preheaters being possible but not necessary.
• an atmosphere reducing the combustion is generated in each case.
• this is achieved by the regulated primary air supply, realized by a suction draft downstream of the high pressure boiler and by increasing the flow velocity in the flame tube.
• the primary combustion air is supplied from below through the ember bed of the pre-firing.
• the smoldering process is also influenced by a variable grate height.
• an ember bed increase or decrease is provided in connection with the primary hip and suction control.
• the flame tube in which the carbonization gases according to the invention are accelerated with the supply of secondary combustion air, without ignition or combustion of the carbonization gases already taking place here.
• the speed is of the low-end of the flame tube 12 to 18 m / s at a temperature of 1000 ° C compared with a speed of 8 12 m / s and 850 0 C at the beginning of the flame tube.
• the flame tubes of the individual pre-firings are brought together in a suitable manner before entering the boiler.
• the accelerated carbonization gas streams are fed separately into the high-pressure boiler and swirled with secondary combustion air immediately after entering the boiler. For this purpose, a tangential supply of secondary air takes place immediately before the bundled flame tubes enter the high-pressure steam boiler, which initially flows around the bundled flame tubes, warms up and then with the Smoldering gas mixed by swirling.
• the inflammation of the carbonization gas only takes place immediately before the boiler enters or the ignition is delayed accordingly by the secondary air supply and the acceleration in the flame tube.
• the complete combustion then takes place in the high-pressure steam boiler, which is provided on the output side with a forced fan and by-pass control can.
• the implementation of the process ensures the separation of charring and combustion of the carbonization gases and mainly shifts the combustion to the area of the high-pressure steam boiler. This makes it possible to replace the combustion of high-quality fossil fuels and to use inferior fuels with the same output of the high-pressure steam boiler.
• a conventional high-pressure steam boiler such as is used to burn high-quality fossil fuels, is preceded by three pre-firings and a suction fan downstream.
• Each pre-burner is equipped with a lowerable rotating grate, above which a flame tube is led outwards to the high-pressure steam boiler.
• the inferior fuel on the respective rotating grate becomes sweaty.
• a reducing atmosphere is created in the pre-firing by primary air supply, by a suction draft downstream of the boiler and by an increase in the flow rate of the carbonization gases in the gutter pipes.
• the rotating grate in the pre-firing is lowered or raised to adapt to the load conditions of the boiler (variable embers). This variation of the ember bed height is done in connection with a regulation of the primary air supply and the suction draft.
• the smoldering gases generated in the pre-firing are accelerated in the subsequent flame tubes.
• secondary combustion air is supplied.
• the speed of the carbonization gas is approx. 10 m / s when entering the respective flame tube and approx. 15 m / s when exiting.
• the temperature rises from approx. 850 ° C to over 1000 ° C.
• the flame tubes Before the flame tubes enter, they are brought together in a suitable manner. Secondary combustion air is fed tangentially in such a way that it first flows around the flame tubes and heats up in the process.
• the three smoldering gas streams are swirled with the heated secondary air.
• the smoldering gas-air mixture is ignited. The combustion takes place in the high pressure steam boiler.

Landscapes

• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Gasification And Melting Of Waste (AREA)
• Solid-Fuel Combustion (AREA)
• Combustion Of Fluid Fuel (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=5555390

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• 1984
  • 1984-03-16 DD DD26097084A patent/DD244894A3/de not_active IP Right Cessation
• 1985
  • 1985-03-16 EP EP85103058A patent/EP0157263A3/fr not_active Withdrawn

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