Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B35/00—Control systems for steam boilers
  • F22B35/06—Control systems for steam boilers for steam boilers of forced-flow type
  • F22B35/14—Control systems for steam boilers for steam boilers of forced-flow type during the starting-up periods, i.e. during the periods between the lighting of the furnaces and the attainment of the normal operating temperature of the steam boilers

Definitions

• the invention relates to a method for starting up a continuous steam generator with a combustion chamber having a number of burners for a fossil fuel, the gas-tight surrounding wall of which is formed from at least approximately vertically arranged evaporator tubes which flow through from the bottom to the top on the feed water side become. It further relates to a start-up system for performing the method.
• the heating of vertically arranged tubes of an evaporator forming the gas-tight surrounding wall of a combustion chamber leads to complete evaporation of the flow medium in the evaporator tubes in one pass.
• a circulating flow is usually superimposed on the continuous flow of the evaporator - and often also a flue gas-heated preheater or economizer arranged in the continuous steam generator.
• the pipes are to be reliably cooled by correspondingly high speeds.
• the minimum current, consisting of continuous flow and superimposed circulating current, for vertically arranged pipes in the peripheral walls of the combustion chamber is between 25% and 50% of the full load flow. This means that when starting, the steam generator load must be increased to at least 25% to 50% before the continuous operation with its high steam outlet temperatures, which is favorable in terms of efficiency, is achieved.
• the amount of the flow medium to be delivered by a feed pump is preferably kept constant. It is the feed flow of the feed pump is equal to the evaporator throughput.
• the start-up times beginning with the ignition of a first burner of the continuous steam generator and ending with continuous operation with high steam temperatures are very long. This results in comparatively high start-up losses, since their height is significantly influenced by the start-up times.
• the invention is therefore based on the object of specifying a method for starting a continuous-flow steam generator in which start-up losses, in particular due to the removal of excess water, are largely avoided. This should be achieved with simple means in a start-up system suitable for carrying out the method.
• this object is achieved according to the invention in that the water level in the evaporator tubes and the ratio of fuel flow to feed water flow are set in such a way that the feed water run through the evaporator completely evaporated, so that there is no more water at the evaporator outlet.
• the invention is based on the consideration that before starting, i.e. before firing the first burner, the water level in the evaporator is raised to a defined level.
• the water level in the evaporator tubes should be high enough to ensure adequate cooling of the evaporator tubes.
• the water level in the evaporator tubes must not be too high in order to avoid the formation of a water plug which occurs during the start-up process downstream of the start of evaporation.
• the amount of feed water to be supplied per unit of time should then depend on the
• Burners per amount of fuel supplied per unit of time are set with the aim that even without a separating device, no water gets into the evaporator-connected superheater heating surfaces on the steam side.
• the level of water i.e. the water level in the evaporator tubes can be derived from the differential pressure which is divided over the evaporator. Therefore, in an expedient development, the pressure difference, preferably between the evaporator outlet and the evaporator inlet, is determined both for determining and for adjusting the water level in the evaporator tubes.
• the gas-tight peripheral wall of which has at least approximately vertically running evaporator tubes which can be flowed through according to the invention from below to above on the feed water side by means of an adjusting device for adjusting the water level in the evaporator and for adjusting the ratio of fuel flow to feed water flow.
• the setting or control variable is expediently the evaporator throughput, ie the amount of feed water supplied to the evaporator on the medium side per unit of time.
• the setting device is therefore expediently connected to an actuator and a flow sensor, which are connected to a feed water line leading into the evaporator.
• the adjusting device is connected to an actuator and a flow sensor, which are connected in a fuel line leading to the or each burner.
• the adjusting device is connected to an actuator which is connected to a drain line connected to the evaporator on the inlet side for dewatering.
• the setting device is connected to means for determining the water level in the evaporator. Both for determining and for setting the water level in the evaporator, at least two pressure sensors arranged along the evaporator are expediently provided.
• a connecting line between the evaporator outlet and the evaporator inlet is also provided, into which a fitting, e.g. a non-return valve is connected to avoid backflow towards the evaporator outlet.
• a fitting e.g. a non-return valve
• Any water that may be present at the evaporator outlet can be fed to the evaporator inlet via the connecting line if the existing pressure ratios permit it. Otherwise, this water can be discharged via an outflow line connected to the connecting line.
• the advantages achieved by the invention are, in particular, that simply by adjusting the ratio of fuel flow to feed water flow, the steam temperature can be adjusted or regulated to the required value during start-up, since there is no longer a defined evaporation end point.
• a start-up system with a separator would be fixed due to the When the end of the evaporation is stopped, the fresh steam temperature inevitably adjusts to the ratio of the evaporator to superheater heating surface when starting, so that it is not possible to adjust the fresh steam temperature to the required value during starting.
• FIG. 1 An embodiment of the invention is explained in more detail with reference to a drawing.
• FIG. 1 shows schematically a once-through steam generator with a vertical throttle cable and with a one-piece device of a start-up system.
• the vertical throttle cable of the steam generator 1 according to FIG. 1 with a rectangular cross-section is formed by a surrounding wall 2 which merges into a funnel-shaped bottom 3 at the lower end of the gas cable.
• Evaporator tubes 4 of the surrounding wall 2 are gas-tightly connected to one another on their long sides, e.g. welded.
• the bottom 3 comprises a discharge opening 3a for ashes, not shown.
• the lower region of the peripheral wall 2 forms the combustion chamber 6 of the once-through steam generator 1 provided with a number of burners 5.
• the entry collector 8 and the exit collector 10 are located outside the passageway and are e.g. each formed by an annular tube.
• the inlet collector 8 is connected via a line 12 and a collector 14 to the outlet of a high-pressure preheater or economizer 15.
• the heating surface of the economizer 15 is in a space above the combustion chamber 6
• Umfa ⁇ ung ⁇ wand 2 arranged.
• the economizer 15 is on the input side via a collector 16 and a feed water line 18 connected with a medium steam D heated heat exchanger 20 which is connected to the pressure side of a feed water pump 22.
• the suction side of the feed water pump 22 is connected in a manner not shown in more detail via a condenser to a steam turbine and thus switched into its water / steam cycle.
• the outlet header 10 is connected via a connecting line 24 and a branch line 26 to an inlet header 27 of a high-pressure superheater 28, which is arranged between the economizer 15 and the combustion chamber 6 within the peripheral wall 2.
• the high-pressure superheater 28 is connected to a high-pressure part of the steam turbine on the output side via a collector 30 during operation.
• an intermediate superheater 32 is provided within the surrounding wall 2, which is connected via collectors 34, 36 between the high-pressure part and a medium-pressure part of the steam turbine.
• the economizer 15, the high-pressure superheater 28 and the reheater 32 lie as convection or bulkhead heating surfaces in the so-called convection train of the continuous steam generator 1.
• the connecting line 24 which leads from the outlet header 10 of the surrounding wall 2 of the convection duct of the steam generator 1 to the lower-level inlet header 27 of the high-pressure superheater 28, is vertical up to the level of the inlet header 8, i.e. de ⁇ evaporator entry, continued.
• a check valve 40 is connected in the connecting line 24.
• drainage lines 42, 44 are connected to the connecting line 24 and are connected to the drainage valves 46 and 48, respectively.
• a first valve 50 and a first flow sensor 52 are connected into the feed water line 18 in the flow direction of the feed water S behind the heat exchanger 20.
• the flow sensor 52 is used to determine the quantity of feed water S conducted via the feed water line 18 and thus to determine the feed water flow.
• the amount of feed water S fed per unit of time via feed water line 18 corresponds to the feed water quantity supplied to the evaporator consisting of evaporator tubes 4 and thus to the evaporator throughput.
• a second flow sensor 54 is connected to a fuel line 56 which opens into the burners 5 via sub-lines 58.
• a second valve 60 is connected in the fuel line 56 to adjust the quantity of fuel B supplied to the or each burner 5 per unit of time and thus to set the fuel flow. Oil, gas or coal can be used as fuel B.
• the flow sensors 52 and 54 are connected via signal lines 62 and 64 to a controller module 66 as an adjusting device.
• Another signal line 68 connected to the controller module 66 is connected via measuring lines 70 and 72 to pressure sensors 74 and 76, respectively, which are provided for measuring the pressure p at the evaporator inlet or the pressure ⁇ and at the evaporator outlet.
• the regulator module 66 is also connected to the valves 50, 60 and 48 via control lines 78, 80 and 82.
• Feed water S and valves 50 and 60 serving to adjust the amount of fuel B are components of a start-up system 84 for starting the continuous steam generator 1. Further components of the start-up system 84 are the pressure sensors 74 connected to the controller module 66 via the signal line 68, 76 and valve 48 connected to control module 66 via control line 82 for dewatering from the lower evaporator part 1.
• the start-up system 84 is used to set the ratio of fuel flow to feed water flow with the aim that the feed water ⁇ during the passage through the evaporator Ferrohre 4 completely evaporated, so that at the evaporator outlet, ie at the outlet collector 10, there is no longer any water.
• the Was ⁇ er ⁇ tand H is moved into the evaporator tubes in the evaporator 4 before starting to a defined height H m i n that lies just above the burner. 5 This takes place, for example, by replenishing feed water S by means of feed water pump 22 or by dewatering from the lower evaporator part via the dewatering line 44.
• the differential pressure is sent to the controller module 66 via the signal line 68 supplied as a measured value, which results from the difference between the mean pressure p ⁇ and p ⁇ measured at the pressure sensors 74 and 76 at the evaporator outlet or at the evaporator inlet.
• the water level H in the evaporator tubes 4 is thereby zwi ⁇ rule the two limit values H max and maintained H m i n, where
• Hgg the height (upper edge) of the highest burner, which with the
• F is an adaptation factor that has been empirically determined to be approximately 0.5 to 2; H KHF the height at which the convection or bulkhead heating surfaces begin with a narrow pitch ( ⁇ 400 mm); ⁇ min the time (3 to 10 minutes) to fill the storage tank, ie the evaporator tubes to the water level H, at the speed v W / s; v ⁇ s the water speed in the evaporator tubes at the start of the feed water flow at the time of the ignition of the first burner.
• the controller module 66 is sent via signal line 62 the current value, measured by means of the flow sensor 52, of the amount of the feed water S supplied to the evaporator, ie the evaporator tubes 4, per unit time.
• This value supplied to the controller module 66 by the flow sensor 52 corresponds to the current feed water flow and thus the evaporator throughput.
• the value of the amount of fuel B supplied to the burners 5 is transmitted to the controller module 66 via the signal line 64 by means of the flow sensor 54 at the current time.
• the level, ie the water level H, at the time “fire ON” and the ratio of fuel flow to feed water flow is selected such that pure steam is present at the outlet collector 10, so that no water flows into the superheater heating surface 28 .
• the branch line 26 from the connecting line 24 is arranged at the inlet height of the superheater heating surface 28.
• any water present in the outlet collector 10 will flow past this branch to the superheater heating surface 28 and collect in the lower part of the perpendicular connecting line 24. From there, this water can either be discharged via the drain valve 46 or fed to the inlet manifold 8 of the evaporator. Alternatively, this water, which may be present, can also be fed to the line 12 between the economizer 15 and the inlet collector 8 of the evaporator. A backflow to the outlet manifold 10 is prevented by the check valve 40.

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• 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)
• Control Of Steam Boilers And Waste-Gas Boilers (AREA)

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• 1995
  • 1995-08-02 DE DE19528438A patent/DE19528438C2/de not_active Expired - Fee Related
• 1996
  • 1996-07-19 WO PCT/DE1996/001343 patent/WO1997005425A1/de active IP Right Grant
  • 1996-07-19 JP JP9507092A patent/JPH11510241A/ja not_active Ceased
  • 1996-07-19 DE DE59604183T patent/DE59604183D1/de not_active Expired - Lifetime
  • 1996-07-19 EP EP96924761A patent/EP0842381B1/de not_active Expired - Lifetime
  • 1996-08-01 IN IN1373CA1996 patent/IN189235B/en unknown
• 1998
  • 1998-02-02 US US09/017,466 patent/US5983639A/en not_active Expired - Lifetime

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