MINIMIZATION OF AIR INGRESS DURING THE

RETROFIT OF BUBBLING FLUIDIZED BED

COMBUSTION TO OXYFUEL COMBUSTION

Gabriel M. Faé Gomes

Leandro Dalla Zen Guilherme P.S. Priebe

Felipe H. Guarienti Jorge A.S. Cunha

Pedro Henrique E. de Lima

OBJECTIVES 1. To determine the effect of fan power, recycling valve opening and gases flow in air ingress minimization

2. To realize the transition of air combustion to oxyfuel combustion by developing a procedure to adjust the process

3. To realize oxyfuel combustion and to compare with air combustion by using the same coal feed

Work structure: 1. Air combustion

2. Gases recycling without oxygen feed

a. Fan power effect analysis b. Recycling valve opening effect analysis c. Gases flow effect analysis

3. Gases recycling with oxygen feed

a. Procedure for process adjuustment b. Oxyfuel combustion

MATERIALS Coal: Oxygen: Industrial oxygen with 99,5 vol. % purity from 10 m3 cilinders.

HHV (MJ/kg) 22,991 LHV (MJ/kg) 22,047

C (%) 55,81 H (%) 3,73 N (%) 0,93 S (%) 0,83 O (%) 8,05

Ashes (%) 30,65

METODOLOGY The pilot plant

METODOLOGY The fluidized bed

RESULTS 1. Air combustion

Condition 1 2 3

mfuel (kg/h) 22,0 26,0 31,0

mair (kg/h) 301,5 343,7 465,7

Air/Fuel Ratio (kg air/kg fuel)

13,7 13,2 15,0

Air excess (%) 98 91 117

” Pleito (Pa) 3873 3971 4560

Pf (Pa) 314 441 706

T04 ( C) 857 851 854

T05 ( C) 859 857 859

FLUE GASES

CO2 (%) 9,1 9,3 8,2

O2 (%) 10,4 10,0 11,3

RESULTS 2.1 Fan power effect Fan 70% 80% 90%

Pf (Pa) 0 0 0

P2 (Pa) - 490 - 490 - 1079

P3 (Pa) - 1079 - 980 - 2059

RESULTS 2.2 Recycling valve analysis

Fan 70% 80% 90%

Recycling valve

opening 100% 50% 25% 10% 100% 50% 25% 10% 100% 50% 25% 10%

P1 (Pa) 2530 2530 2481 2324 2765 2746 2707 2491 2863 2863 2785 2383

P2 (Pa) - 588 - 490 - 392 - 98 - 490 - 392 39 98 - 108 - 686 - 726 - 59

P3 (Pa) - 1079 - 1177 - 1471 - 2667 - 981 - 784 - 117

7 - 3236 - 2059 - 1961 - 2648 - 3923

FLUE GASES

O2 (%) 3,1 2,7 2,1 0 3,5 2,6 2,3 0 5,3 5,1 3,9 0

CO2 (%) 13,7 14,3 14,8 12,4 13,7 14,6 12,8 16,7 12,2 14,7 12,4 14,2

RESULTS 3. Gases recycling with oxygen feed 3.1 Adjustment procedure 1. 100% valve recycling opening;

2. Partial chimney close (via damper);

3. Progressinve recycling valve close;

4. Progressive air feed decrease with O2 feed;

5. Entrance flow adjustment via recycling valve adjustment.

RESULTS AND DISCUSSION 3. Gases recycling and oxygen feed 3.2 Oxyfuel combustion

Fan 80%

Recycling valve opening 7%

mfuel (kg/h) 31

mgases (kg/h) 182,7

” Pbed (Pa) 3923

Pf (Pa) 137

Te (K) 322,15

T04 (K) 1046

T05 (K) 1046

ENTRANCE

CO2 (vol. %) 34,2

O2 (vol. %) 29,3

N2 (vol. %) 36,5

CO2 (wt. %) 43,4

O2 (wt. %) 27,1

N2 (wt. %) 29,5

EXIT

CO2 (vol. %) 59,6

O2 (vol. %) 3,9

N2 (vol. %) 36,5

CO2 (wt. %) 69,5

O2 (wt. %) 3,3

N2 (wt. %) 27,1

SUMMARY 1. The adjustment of three parameters showed to be crucial for the transtion of air combustion to oxyfuel combustion in a BFB: fan power, recycling valve and gases flow

2. Negative and positive pressure points along the system must be kept via process adjustment according to the system configuration

3. Positive pressure points and system sealing showed to be essential for controlling air leakage

Project continuation