we focus on your process Systems Page 1

Transcription

1 Systems Page 1

2 Presentation Our Target: Boiler Combustion Optimization with Get a better view into the combustion of your boiler! Page 2

3 Presentation Boiler Combustion Optimization UBC On-line measurement of the unburned carbon in the fly ash Coal On-line measurement of the coal mass flow between the mill and the burner Air On-line flow measurement of preheated excess air or flue gas Page 3

4 Pulverized fuel Secondary air Primary air System Application for Boiler Optimization Steam generator Air Burner Air preheater Electric precipitator Flue gas Coal bunker Coal Coal mill FD-Fans Intermed. Flyash bunker Excess Air Fly ash UBC Page 4

5 UBC Page 5

6 UBC Measurement Principle: Unburned carbon content Dielectric constant of fly ash is a function of the carbon content. Measuring the shift of frequency in a resonator ( f) the carbon content can be calculated. UBC = A + B f A and B are the calibration coefficients Page 6

7 UBC Accuracy of the values Unit Block1 1 Sensor Sensor1 1 Unit Block1 1 Sensor2 2 Unit Block2 2 Sensor1 1 Unit Block2 2 Sensor2 2-0,60% +0,60% Single calibration at different coal types for several month Page 7

8 Coal Page 8

9 Coal Measurement Principle: Density Microwave measurement: 2 sensors in one pipe are used to measure the coal concentration over the FULL cross sectional area of the pipe Transmitter Receiver Easy installation: The sensors are mounted through easy drill and tap holes (14x1 mm) In case of roping: cover full cross section Page 9

10 Coal Measurement Principle: Velocity Coal Dust Pipe Velocity W=S/T Signal Sensor 1 Signature Signal Sensor 2 Sensor 1 X(t) S=const. Sensor 2 Y(t)=X(t-T) correlation Correlation T=-26 ms Optimum of correlation Example S=54 cm T=26 ms Time T w=20,8 m/s (average velocity of the particles!) Page 10

11 Coal Absolute mass flows and velocities Page 11

12 Coal psa Particle Size Analysis Page 12

13 Coal psa Particle size distribution Example: Biomass PSA Page 13

14 AIR System Air Page 14

15 Air Measurement Principle: Velocity Air Duct or Pipe Signal Sensor 1 Signature Signal Sensor 2 Sensor 1 X(t) S=const. Sensor 2 Y(t)=X(t-T) correlation Correlation T=-26 ms Optimum of correlation Example S=54 cm T=26 ms w=20,8 m/s (average velocity of the air!) Time T Page 15

16 Air Velocity trends and 4-20mA outputs Page 16

17 13 golden rules for efficient combustion I. Fuel preparation: No 1. Fuel shall be consistent in size and quality No 2. Fuel shall be fed to pulverizer by an accurate feeder (gravimetric feeder) No 3. Pulverized fuel shall be 75% below 70 µm Coal psa and less than 0.1% larger than 200 µm. Page 17

18 13 golden rules for efficient combustion II. Fuel conveying to the burners: No 4. Primary air flow needs to be measured and Air controlled to a tolerance of 3% of full scale value No 5. Primary air to fuel ratio shall be accurately Coal controlled when above the minimum No 6. Fuel velocities shall always be higher than 23 m/sec Coal No 7. Mill outlet temperature shall be consistent and controlled temp to a tolerance of 5 K No 8. The balance of coal velocities on all pipes shall be Coal within a tolerance of 2 m/sec No 9. The coal mass flow distribution shall be within Coal a tolerance of 5 % Page 18

19 13 golden rules for efficient combustion III. Combustion: No 10. Secondary air distribution controlled Air to a tolerance of 5% No 11. Overfire air distribution controlled Air to a tolerance of 5% No 12. Swirl air settings controlled Air to a tolerance of 5% No 13. Excess air level reduced to the point UBC where UBC is below max taget value (usually 5%) Page 19

20 Checking the 13 Rules on a boiler Boiler Secondary Air PA FD Fan Primary Air Coal Bunker Feed Coal bunker Air 16 Brenner Burner pipes Coal Coal psa Burner Air Four pulverizers Page 20

21 Massflow [t/h] Particle Frequency [%] Rule No 3: Particle size consistency This mill has no coarse particles in the Pf Test Data: PS Reuter West, Berlin ,0 MECONTROL Coal Measurement with Feedersignal and Particlesize Distribution , , , , ,0 06:00 08:24 10:48 13:12 15:36 18:00 20:24 22:48 0 Sum Burner 1-4 [t/h] Feeder [t/h] > 200 µm [%] µm [%] < 90 µm [%] Page 21

22 [m/s] [Nm³/h] [ C] Rule No 4: Accurate PA flow control can check the PA flow into the mill as well as out of the mill PROMECON MECONTROL Air Primärluft Mühle :00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 Graph shows PA flows into the mill as well as Mill inlet temperature PL M40-1 PL M40-2 M 40 dp Mühle 40 M 40 Temp. Mühle 40 BlnPA_D_IPC MECONTROL Air Kohlenstaubgeschwindigkeit Mühle 40 PROMECON 40,0 35,0 30,0 25,0 20,0 15,0 10,0 5,0 0,0 00:00 02:24 04:48 07:12 09:36 12:00 14:24 16:48 19:12 21:36 00:00 Brenner 41 Brenner 42 Brenner 43 Brenner 44 Graph shows the resulting velocities out of the mill. It can be checked if the velocities into the mill are appropriate for each load point and coal type. Page 22

23 Velocity (cm/s), Temperatur Dichte Rule No 5: Accurate control of coal concentration Underperforming pulverizer High standard deviation of concentrations and velocities Pipe Variation of velocity 1s: m/s (4.6 ft/sec) Velocity Density Variation of coal loading 1s: g/m :24:00 16:48:00 19:12:00 21:36:00 00:00:00 02:24:00 04:48:00 07:12:00 09:36:00 Page 23

24 09:59 10:19 10:40 11:00 11:20 11:40 12:00 12:20 12:41 13:01 13:21 13:41 14:01 14:21 14:41 cm/se c Rule No 6: Control of minimum coal velocities Low velocities cause pulsations in the coal flow Results Coal Velocities Velocities Velocities Pipe 1 Pipe 2 Pipe 3 Pipe Vertical piping Horizontal piping Page 24

25 Rule No 7: Accurate control of mill outlet temperature Drifting Mill outlet temperature at constant load Page 25

26 Rule No 8: Adjustment of coal velocities Adjustment of coal flow velocity Burner Coal Valve Coal Splitter Box Pulverizer Example Pipe Arrangement Page 26

27 Rule No 8: Adjustment of coal velocities Here a large velocity spread has been corrected by a variable orifice Page 27

28 Rule No 9: Adjustment of coal mass flows Same coal mass flow to every burner Coal distribution before the adjustment Coal distribution after the adjustment Page 28

29 Rule No 10, 11 and 12: Adjustment of SA and OFA Typical Problems with delta P measurement 15% deviation Page 29

30 Rule No 13: Adjustment of O2 set point with UBC value O 2 set point reduction Page 30

31 UBC [wt.-%]; O 2 [vol.-%] Secondary air x 1000 [m³/hr] STP UBC Optimisation Results Rule No 13: Adjustment of O2 set point with UBC value Trial run at Wedel power plant Excess air: n abs = 7.6 %-pts = 0.5 %-pts Secondary air Basis: n = Resulting efficiency increase: 0.42 %-pts! UBC: C abs = -2 %-pts = %-pts O 2 right duct O 2 left duct UBC Basis: gash = 3.6 % Excess Air Reduction Time 200 Page 31

32 Example: Power station Stigsnaes, DONG Energy Capacity 265 MW el Erected in 1969 as oil fired unit Later converted to coal 4 pulverizers with dynamic classifier 24 burners Individually ducted secondary air Page 32

33 Stigsnaes firing system Burner Coal Splitter Box Pulverizer Page 33

34 NOx optimization Page 34

35 Boiler / Mill optimization by UBC monitoring General example calc.: Black coal utility plant Increase in efficiency* 0.45% 0.40% 0.35% 0.30% 0.25% 0.20% 0.15% 0.10% 0.05% UBC at 7.2 % g A UBC at 3.6 % g A O % 0% 1% 2% 3% 4% 5% 6% O 2 -content of flue gas; UBC in fly ash *) Without power savings of fans Excess Air Reduction Page 35

36 Boiler efficiency increase Page 36