Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
  • F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
  • F22B31/0084—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed with recirculation of separated solids or with cooling of the bed particles outside the combustion bed
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
  • F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
  • F22B31/0015—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed for boilers of the water tube type
  • F22B31/003—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed for boilers of the water tube type with tubes surrounding the bed or with water tube wall partitions
  • F22B31/0038—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed for boilers of the water tube type with tubes surrounding the bed or with water tube wall partitions with tubes in the bed

Definitions

• forced flow or continuous steam generators for generating electrical energy by firing fossil fuels, for example.
• the latter are used particularly in modern or large power plants.
• the heat released during the combustion of the fuel in the combustion chamber of the once-through steam generator is transferred to heating surfaces through which working medium flows, consisting of, for. B. combustion chamber surrounding walls, radiation, or convective heating surfaces, the continuous steam generator.
• the working medium is integrated in a water / steam circuit of a steam turbine, in which it passes on the thermal energy absorbed.
• Such continuous steam generators in which the working medium is preheated, evaporated, superheated and possibly reheated essentially in one pass of the steam generator, have been known for a long time and are usually equipped with burners for burning fossil fuels.
• a conventional, coal dust-fired continuous steam generator has become known from the publication "forced flow boiler for sliding pressure operation with vertical combustion chamber pipes", VGB Krafftechnikstechnik 64, issue 4, April 1984, H. Juzi, A. Salem and W.
• Continuous-flow steam generators with circulating fluidized-bed firing systems must not be inclined or inclined, as in conventional coal-dust-fired continuous-flow steam generators, but must be vertically drilled.
• the circulating fluidized bed combustion systems were therefore mainly combined with evaporator systems that operate in natural circulation or forced circulation mode and are therefore equipped with vertically-drilled surrounding walls.
• a few circulating fluidized bed furnaces also generate the steam with a forced flow system, however as a downpipe / riser system and at low steam pressures (e.g. KW Moabit). Considerations have already been made to use the once-through steam generator with ZWSF also in the pressure range 1 ⁇ 0 to 300 bar and thus more economically, i.e. to run on less fuel. Because of the need
• ZWSF once-through steam generators which are operated with subcritical steam pressures, require a higher fuel consumption compared to supercritical steam pressures with the same steam generator output and thus generate more harmful emissions.
• the object of the invention is now to create a continuous steam generator with circulating atmospheric fluidized bed combustion, in which the aforementioned disadvantages are avoided or the criteria mentioned below are met or adhered to.
• the solution according to the invention creates a once-through steam generator with circulating atmospheric fluidized bed combustion, which has the following advantages:
• Combustion chamber floor or in the top edge of the funnel and in the combustion chamber ceiling can be integrated.
• Mass flow density set which is required to mass flow
• Fig. 1 shows schematically a continuous steam generator with circulating atmospheric fluidized bed combustion in longitudinal section
• FIG. 2 schematically shows a fluidized bed combustion chamber of a fluidized bed continuous steam generator with a combustion chamber funnel in longitudinal section
• FIG. 4 schematically shows a combustion chamber of a fluidized bed continuous steam generator (with a combustion chamber funnel) in cross section according to section AA of FIG. 2, section rotated through 90 °
• 5 schematically shows a combustion chamber of a fluidized bed continuous steam generator (with two combustion chamber funnels) in cross section according to section BB of FIG. 3, section rotated through 90 °
• FIG. 6 shows a schematic cross section of an alternative box-shaped heating surface (box bulkhead) according to detail C of FIGS. 4 and 5,
• FIG. 7 schematically shows a box-shaped heating surface with a vertically aligned transition from the refractory lining to the upper membrane tube wall in longitudinal section, corresponds to section A - A of FIG. 8,
• FIG. 8 shows a schematic cross section of a box-shaped heating surface according to section C - C of FIG. 9,
• FIG. 9 shows a schematic longitudinal section of a box-shaped heating surface according to section BB of FIG. 8.
• FIG. 1 schematically shows a once-through steam generator 1 with circulating fluidized bed combustion 2 (ZWSF) for the combustion of coal or other combustible substances.
• the substance to be burned is introduced either together with an inert material or separately through the feed line 10 into the fluidized bed or fluidized bed combustion chamber 3 of the once-through steam generator 1 with ZWSF.
• a fluidizing gas through the feed line 11 is usually the Wirbelbrennk ⁇ mmer 3 fed from below.
• the fluidizing gas is usually air and is therefore used as an oxidizing agent for combustion.
• the exhaust gas or flue gas produced during the combustion and the solids carried by the exhaust gas are discharged from the combustion chamber 3 in the upper area via the opening 1 2 and to a separator, usually a centrifugal separator, via an exhaust pipe 1 3 or cyclone separator 14 supplied.
• the solids are largely separated from the exhaust gas in the separator 14 and fed back to the combustion chamber 3 via the return line 15.
• the largely cleaned exhaust gas is fed via exhaust pipe 1 6 to a second flue gas duct 1 7, in which at least one economizer heating surface 1 8, at least one superheater heating surface 1 9 and possibly at least one reheater heating surface 20 for further use or removal of the Exhaust heat is arranged.
• the cross section of the combustion chamber 3 is generally rectangular. However, it can also be round or have another shape.
• FIGS. 2 to 5 show in longitudinal and in cross section the rectangularly shaped and essentially vertically arranged swirl combustion chamber 3 of a once-through steam generator 1.
• the combustion chamber 3 is essentially enclosed on all sides by surrounding walls 4, the surrounding wall 4 comprising the combustion chamber bottom 4.1, the combustion chamber side walls 4.2 and the combustion chamber ceiling 4.3, viewed from the bottom up.
• the combustion chamber base 4.1 is generally designed as a nozzle base through which the fluidizing gas is introduced.
• 2 shows a combustion chamber 3 with a simple funnel 6 in the lower region of the combustion chamber 3
• FIG. 3 shows a combustion chamber 3 with a double funnel 7, a so-called "pant leg" design.
• the combustion chamber surrounding walls 4 are designed as heating surfaces through which working medium flows, these Such membrane walls can be assembled by gas-tight welding of a tube-web-tube combination.
• the tube-web-tube combination comprises tubes 5 which are smooth on the outer circumference and which each have separate webs 21.
• fin tubes are also possible, the outer wall of which are already formed with webs and which are connected to one another.
• the present invention aims at continuous steam generator 1 with circulating fluidized bed combustion 2 of high output (approx. 300 to 600 Mwel) and high steam parameters (approx. 250 to 300 bar pressure and 560 to 620 ° C. temperature).
• additional heating surfaces 8 which are preferably arranged within the combustion chamber 3 for thermal reasons (uniform heat absorption).
• the continuous steam generator 1 according to the invention with ZWSF 2 provides that all pipes 5, 9 of the surrounding walls 4 and the heating surfaces 8 located within the combustion chamber 3 are designed as evaporator heating surfaces and are connected in parallel for the flow of the entire working medium to be evaporated, that all pipes 5 of the Boundary walls 4 are formed with an internally smooth tube surface and the heating surfaces 8 extend between the combustion chamber bottom 4.1 or the funnel top edge 24 and the combustion chamber ceiling 4.3.
• the parallel connection of the heating surfaces 8 and the heating surface of the peripheral wall 4 of the continuous steam generator 1 and the use of both heating surfaces as the evaporator heating surface advantageously means that the combustion chamber 3 can be designed efficiently by adapting the number of heating surfaces 8.
• the combustion chamber dimensions can be optimized with this measure, in particular the combustion chamber height (distance between the combustion chamber floor and ceiling) can be significantly reduced by integrating the heating surfaces 8.
• the effective heat flow densities within the fluidized bed combustion chamber 3 in the aforementioned circuit of the once-through steam generator 1 according to the invention despite the reduced working medium mass flow densities of approximately 400 to 1200 kg / ms, make it possible to use those for the tubes 5 of the surrounding walls 4 which have a smooth surface on the inside exhibit.
• the reduced working medium mass flow densities also result in an improved natural circulation characteristic within the evaporator heating surfaces, which means that if there is any local overheating, there is also an increase in the working medium throughput and thus reliable pipe cooling is ensured.
• tubes 5 with an internally smooth surface also called smooth tubes for short
• smooth pipes are much cheaper than internally finned pipes, have shorter delivery times, are available in considerably more sizes and are generally more readily available, since finned pipes are usually only available as a special design, and, in terms of assembly, smooth pipes are much easier to handle
• smooth pipes have a much smaller frictional pressure loss of the working medium compared to internally finned pipes, which has a positive effect on the uniform distribution of the working medium on the individual pipes 5 and on a reduction in the feed pump output of the continuous steam generator 1.
• continuous steam generators 1 are increasingly used in the supercritical range, i. H. operated at a steam pressure of over 220 bar and in the sliding pressure between supercritical and subcritical pressure (the operating pressure of the steam generator glides in the load range of the continuous steam generator, e.g. between 20 to 100% load).
• the steam generator With a continuous steam generator operating pressure of, for example, 270 bar at full load, the steam generator reaches the critical pressure range at a partial load of approximately 70% and is operated subcritically below this partial load, i.e. H. that a two-phase mixture occurs in the evaporator during the evaporation process in the part-load range approximately below 70%.
• the additional heating surfaces 8 used in the vortex combustion chamber 3 are so-called bulkhead heating surfaces.
• Schott heating surfaces are self-contained and plate-like heating surfaces (ie the individual side by side
• the adjacent tubes 9 are connected to one another with webs 22 - welded tube-web-tube combination - to form a bulkhead), which are in contrast to bundle heating surfaces which are open (ie the individual tubes arranged next to one another are not connected to one another with webs).
• the heating surfaces 8 are arranged essentially vertically within the combustion chamber 3 and the pipes 9 contained therein also run essentially vertically.
• the heating surfaces 8 either extend between the combustion chamber base 4.1 or the top edge of the funnel 24 and the combustion chamber ceiling 4.3. As a result, they can be fully used together with the surrounding wall 4 for parallel flow through the entire working medium to be evaporated.
• the heating surfaces 8 thus originate in the lower region of the vortex combustion chamber 3 essentially on the combustion chamber floor or on the lower funnel edge 4.1 in a combustion chamber 3 with a funnel 6 (FIG. 2) and central arrangement of the heating surfaces 8 within the combustion chamber 3 or on the upper funnel edge 24 in one Combustion chamber 3 with two funnels 7 (FIG. 3) and central arrangement of the heating surfaces 8 and ends in the upper region of the vortex combustion chamber 3 essentially at the combustion chamber ceiling 4.3.
• these can be welded, for example, to the combustion chamber floor 4.1 or upper funnel edge 24 and the combustion chamber ceiling 4.3. If more than two funnels are provided in the lower region of the combustion chamber 3, the heating surfaces 8 can be integrated accordingly.
• the parallel feeding of the heating surfaces 8 and the surrounding wall 4 takes place through collectors (not shown), by means of which the working medium to be evaporated is supplied to the above-mentioned heating surfaces from below. If the heating surfaces 8 in a combustion chamber 3 with two funnels 7 according to FIG. 3 only begin at the top edge of the funnel or at the funnel saddle 24, these heating surfaces 8 can be fed with working medium via the funnel-surrounding walls 4. A separate, parallel feed of the heating surfaces 8 is also possible.
• the heating surfaces 8 can be heated on one or two sides. In the case of bilaterally heated or Schott heating surfaces 8, it is advantageous to have the heating surfaces 8 with tubes 9 with internal ribs In order to ensure reliable cooling of the pipe 9 in the partial load range of the continuous steam generator 1 and to avoid the boiling crisis or DNB (departure from nucleate boiling) and drying out or dryout known in the specialist circles, which is caused by the heating of the heating surface 8, by the additional heating could occur from both sides.
• DNB departure from nucleate boiling
• FIG. 6 shows an advantageous embodiment of a heating surface 8 heated on one side.
• This heating surface 8 comprises an interior 23 on the circumference and is box-shaped, which is why the heating surface 8 is also referred to in the further description as a box-shaped heating surface or as a box bulkhead (s) 8.
• FIG. 6 shows an advantageous embodiment of the box-shaped heating surface 8 with a rectangular cross section.
• the box bulkhead 8 according to FIG. 6 has four side walls made of welded membrane tube walls which are welded together at the corners, the membrane tube walls being formed from tubes 9 and webs 22. The result is a box in a gas-tight welded tube-web-tube version or combination.
• the tubes 5, 9 Due to the vertical arrangement of the heating surfaces 8 and thus also the tubes 9 and the vertical tubes 5 of the surrounding walls 4, the tubes 5, 9 give the gas and particle stream flowing from bottom to top in the combustion chamber 3 as little erosion points as possible.
• the pipes 5, 9 in the lower combustion chamber area or in the funnel area 6, 7 are provided with a refractory lining 25.
• An advantageous embodiment of the invention provides, according to FIGS. 7 to 9, the tubes 9 in the combustion chamber funnel region 6, 7 with a refractory lining 25 provided box-shaped heating surface 8 in the transition region 26 between lined and unlined heating surface region 27 to bend inwards into the region of the interior 23 and to align the front edges of the refractory lining 25 and the non-lined region 27 of the heating surface 8 in the vertical direction.
• This measure prevents that there are erosion points of attack on the pipes 9 for turbulence flows of the gas and particle flow in the transition region 26.
• the refractory lining 25 of the tubes 5, 9 in the funnel area 6, 7 advantageously results in lengths of the tubes 5, 9 which are essentially the same heating within the combustion chamber 3.
• the tubes 9 used for the box-shaped heating surfaces 8 advantageously have
• the box-shaped heating surfaces 8 can be produced using materials and manufacturing processes customary in steam generator construction.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fluidized-Bed Combustion And Resonant Combustion (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Spray-Type Burners (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

Family

ID=32318650

Family Applications (1)

Country Status (7)

Families Citing this family (9)

Citations (5)

Family Cites Families (10)

• 2002
  • 2002-11-22 DE DE10254780A patent/DE10254780B4/de not_active Expired - Lifetime
• 2003
  • 2003-11-18 ES ES03767428T patent/ES2429872T3/es not_active Expired - Lifetime
  • 2003-11-18 US US10/535,810 patent/US7331313B2/en not_active Expired - Lifetime
  • 2003-11-18 WO PCT/DE2003/003808 patent/WO2004048848A2/de active Application Filing
  • 2003-11-18 CN CNB2003801037713A patent/CN100396991C/zh not_active Expired - Lifetime
  • 2003-11-18 EP EP03767428.0A patent/EP1563224B1/de not_active Revoked
  • 2003-11-18 PL PL377705A patent/PL207502B1/pl unknown

Patent Citations (5)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events