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EP-4656941-B1 - BOILER PLANT AND METHOD FOR PRODUCING HEAT BY COMBUSTION OF AT LEAST ONE FUEL

EP4656941B1EP 4656941 B1EP4656941 B1EP 4656941B1EP-4656941-B1

Inventors

  • BEYER, MICHAEL

Dates

Publication Date
20260513
Application Date
20240529

Claims (15)

  1. A boiler plant for generating heat by burning at least one fuel, comprising a burner (30) for generating a flame (40) which is oriented along a longitudinal axis (41) in a combustion chamber (1) of the boiler plant (40) , wherein the boiler plant is configured to perform an internal recirculation (51) of exhaust gas (50) generated during combustion back into the flame (40), wherein a cooling unit (60) is arranged in the region of the exhaust gas recirculation (51), with which heat from recirculated exhaust gas (50) can be absorbed and dissipated, wherein the cooling unit (60) comprises at least one cooling element (70) in which a cooling medium (61) can be accommodated or is accommodated, and wherein the cooling medium-carrying cooling element (70) can be flow-surrounded by recirculated exhaust gas (50), characterized in that the cooling medium-carrying cooling element (70) is displaceable by means of a positioning unit (90) substantially along the longitudinal axis (41) of the flame (40) such that it can be positioned at different positions along the longitudinal axis (41) of the flame (40).
  2. The boiler plant according to claim 1, characterized in that the cooling element (70) at least partially surrounds the longitudinal axis (41) of the flame (40) radially, in at least one position.
  3. The boiler plant according to one of the preceding claims, characterized in that the boiler plant comprises a combustion chamber wall (10) and the positioning unit (90) comprises at least one insertion sleeve (95) in the combustion chamber wall (10), in which a conduit element (12) of the cooling unit (60), which is fluidically connected to the cooling element (70), is received, such that the conduit element (12) can be guided through the insertion sleeve (95) and the cooling unit (60) can thus be positioned at different locations along the longitudinal axis (41) of the flame (40).
  4. The boiler plant according to at least one of the preceding claims, characterized in that the cooling element (70) has a substantially rotationally symmetric configuration (100).
  5. The boiler plant according to claim 4, characterized in that the cooling element (70) essentially has a hollow cylindrical shape (101).
  6. The boiler plant according to claim 4, characterized in that the cooling element (70) essentially has a hollow truncated cone shape (102).
  7. The boiler plant according to at least one of the preceding claims, characterized in that the cooling element (70) comprises at least one tube through which a cooling medium (61) flows or can flow through.
  8. The boiler plant according to claim 7, characterized in that the tube (70) is arranged helically around the longitudinal axis (41).
  9. The boiler plant according to claim 7, characterized in that the tube (70) extends in a meandering pattern around the longitudinal axis (41) of the flame (40).
  10. The boiler plant according to at least one of the preceding claims, characterized in that the cooling element (70) comprises at least one flow-guiding element (130) arranged such that it has a guiding function for guiding recirculated exhaust gas (50) from the radial exterior into the flame (40).
  11. The boiler plant according to claim 10, characterized in that the cooling element (70) comprises at least one meandering pipe and at least one flow-guiding element (130) arranged between pipe sections (112) connecting the loops (113) of the meander
  12. The boiler plant according to claim 10, characterized in that the cooling element comprises at least one tube (70) arranged helically around the longitudinal axis (41) and at least one flow guide element (130) arranged at at least one angular position at the circumference of the cooling element (70) between the tube sections at this angular position.
  13. The boiler plant according to claim 10, characterized in that the cooling element 70 comprises at least one flow guide element 130 through which a cooling medium 61 flows or can flow through, wherein the flow guide element (130) extends with at least one component of its longitudinal direction parallel to the longitudinal axis (41) and is fluidically connected to a distribution unit (140) for distributing cooling medium (61) to the flow guide elements (130).
  14. The boiler plant according to claim 13, characterized in that the flow guide elements (130) have flow-optimized inflow surfaces (131).
  15. A method for generating heat by burning at least one fuel using a boiler plant according to any one of claims 1-14, in which a flame (40) is generated in the combustion chamber (1) of the boiler plant using the burner (30) along the longitudinal axis (41), and the resulting exhaust gas (50) is recirculated internally into the flame (40), wherein, by means of the cooling unit (60) heat is absorbed and dissipated from the recirculated exhaust gas (50), and by means of the positioning unit (90), the cooling medium-carrying cooling element (70) of the cooling unit (60) is displaced essentially along the longitudinal axis (41) of the flame (40) generated by the burner (30) and the position of the cooling element (70) is adjusted substantially along the longitudinal axis (41).

Description

The present invention relates to a boiler system and a method for generating heat by burning at least one fuel. In heat generators such as boilers or boiler systems with tube-ribbed-tube walls or finned walls as the combustion chamber walls, generally referred to as water-tube boilers, burner openings in the walls are created by bending tubes. These projecting tubes are also called burner baskets. The tubes are bent outwards and sealed and covered with refractory material. A gas-tight burner box is welded around the burner basket to the outside of the boiler wall, covering and insulating the bent tubes. The burner is mounted on the burner box, with its burner nozzle leading into the boiler's combustion chamber. The sum of the extended tube lengths of all tubes in a burner basket depends on the required clear installation diameter of the burner. For low-NOx burners with air and/or fuel staging, this installation diameter is larger than for standard burners without staging. In fire-tube boilers, the burners are typically mounted on the end wall or front wall of the fire tube. The side of this front wall facing the combustion chamber is usually lined with refractory material for insulation, or, less commonly, with a smooth steel wall and water cooling. It is known that NOx formation via thermal pathways during the combustion of gaseous, liquid, and solid fuels can be effectively reduced by exhaust gas recirculation. A distinction is made between external and combustion chamber-internal exhaust gas recirculation. In external exhaust gas recirculation, a portion of the exhaust gas stream is extracted after it leaves the combustion chamber and returned to the burner or back into the combustion chamber. This portion is often mixed with the combustion air to lower the oxygen partial pressure of the oxidizer. In contrast, with combustion chamber-internal exhaust gas recirculation, the burner acts as an injector, drawing exhaust gas from the outer recirculation zone directly at the edge of the air outlet. In burners with supercritical swirl, exhaust gas is also recirculated along the flame axis or in the low-pressure area at the core of the flame root. The efficiency of internal combustion chamber exhaust gas recirculation is influenced by several factors, such as the magnitude of the motive impulse flow of the air stream exiting the burner, the fuel flow or air-fuel mixture flow, possibly mixed with externally recirculated exhaust gas; the burner nozzle design; and the intensity of the mixing of the motive jet and the internally drawn-in exhaust gas stream. Regarding the nozzle design, it is particularly important whether the nozzle cross-section has a cylindrical outlet, a conical widening, or a conical narrowing. The WO 2008/ 119753 A1 The document discloses a gasification reactor comprising a pressure jacket and a reaction zone partially bounded by a vertically oriented, tubular membrane wall. The gasification system further includes a burner basket for generating a flame and is designed to recirculate exhaust gas back to the flame. The exhaust gas passes through a cooling device. The EP 3 467 383 A1 discloses a boiler system according to the preamble of the first claim. The invention is based on the objective of providing a boiler system and a method for generating heat by burning at least one fuel using the boiler system according to the invention, with which a reduction in pollutant emissions, in particular NOx emissions, can be achieved in an efficient and energy-saving manner. This problem is solved by the boiler system according to claim 1 and by the method for generating heat energy by burning at least one fuel using the boiler system according to claim 15. Advantageous embodiments of the boiler system are specified in dependent claims 2-14. The features of the claims can be combined in any technically meaningful way, taking into account the explanations from the following description as well as features from the figures, which include supplementary embodiments of the invention. According to the invention, a boiler system for generating heat by combustion of at least one fuel is provided, which has a burner for generating a flame directed along a longitudinal axis into a combustion chamber of the boiler system, wherein the boiler system is configured to implement internal recirculation of exhaust gas generated during combustion into the flame. A cooling device is arranged in the area of exhaust gas recirculation, with which heat from the recirculated exhaust gas can be absorbed and dissipated, wherein the cooling device has at least one cooling element in which a cooling medium is absorbed or contained. The cooling element carrying the cooling medium is permeable to recirculated exhaust gas and is connected by means of a positioning device essentially displaceable along the longitudinal axis of the flame in such a way that it can be positioned at different positions along the longitudinal axis of the flam