CombustionCombustion ofof AgriculturalAgricultural BiofuelsBiofuels in in FluidizedFluidized BedBed BoilersBoilers

Prof.Ing. František Hrdlička,PhD.Ing.Jan Hrdlička,PhD.

Department Department ofof Fluid Dynamics Fluid Dynamics andand PowerPower EngineeringEngineering

Czech Technical University in Prague (CTU), Czech Republic

Renewables in heat production

Total heat consumption is 381 PJ/yr , including centralized heat sources (CZT) 209 PJ/yr and decentralized heat sources (DZT) 172 PJ/yr

SUCCESSFUL EXAMPLE – co-firing of sugar beet and coal in 2MW BFBC boiler with internal bed material

circulation

Co-firing of sugar beet chips and coal – experimental data

- significant

SO2

reduction- works

well

up

to 1:1 coal:chips

ratio

Analysis of sugar beet chips

Water content Wr

= 79,7 %

Ash content Ar = 1,21 %

Combustibles hr

= 19,09 %

LHV Qs

= 3,41 MJ/kg

Co-firing of sugar beet chips and coal – experimental data

coalcoal : chips ratio3 : 1 1 : 1

Power output kW 1150 1100 1200O2 % 10,1 9,2 8,6CO at O2 =6 % mg/m3 24 111 196Excess air ratio - 1,95 1,78 1,70NOx at O2 =6% mg/m3 658 616 570Bed temperature °C 860 835 845

Unsuccessful example – combustion of dry grain stillage in 1,5 MW coal BFBC boiler

0

200

400

600

800

1000

1200

9:00 10:00 11:00 12:00Time

Tem

pera

ture

s (°

C),

O2 x

10

(%)

O2x10FB temp 1FB temp 2End-of-chamber temp

Agricultural biofuels – ash melting problem

Important properties influencing FB operation

- ash

and

water

content

- volatiles

content

- ash

melting

temperatures

- elementary

composition

Properties of several biofuels of agricultural origin

Fuel A (wt.%)

W (wt.%)

Vdaf

(wt.%)HHV

(kJ/kg)LHV

(kJ/kg)sorrel

lucernesorrel + phalaris 1:1grain residues – rye

grain wastesorrel + sawdust 1:1

hay

4,957,134,993,596,152,909,01

9,328,099,209,0610,477,879,48

80,379,479,278,485,277,080,0

17 52017 14916 74017 14216 26716 31015 690

15 95115 61915 21415 52514 55814 72914 097

Fuel C H O N S Cl Fsorrel

lucernesorrel + phalaris 1:1grain residues – rye

grain wastesorrel + sawdust 1:1

hay

43,4043,3743,2842,3542,2345,1041,20

6,076,035,896,326,586,296,16

35,2032,1335,8636,2830,2437,3131,63

0,942,940,442,053,080,241,63

0,090,170,090,290,240,070,15

0,0300,1400,1400,0600,2700,1000,147

--------

0,110----

0,7400,1200,600

Ash properties

Fuel Softening

point °C

Melting

point °C

sorrel 1255 1280lucerne 1500 >1500sorrel + phalaris

1:1 860 905

sorrel

+ sawdust

1:1 875 920grain residues

–

rye 1120 1135

hay 1080 1170grain

waste 1080 1140

Ash properties in pictures – furnace and heat exchanger input after 1 month operation

Ash properties in pictures – ash from the bottom of the furnace

SORREL – an example of influence of various locations on ash composition in a biofuel

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10 11 12

wt.

%

SPAlMgNaSiCaK

Conclusions

necessity of modification of the density orgranulation of the inert bed componentgood knowledge of composition of theenergetic cropsfeeding of energetic crops throughsecondary air

Thank you for your attention!