P.1 

OAR Box 1865 

Prepped by Charmelle Mathews 

Document Number: 

78) IV-J-21 

Docket Number: 

A-83-27 

Printed 12/3/2008 9:15:31 AM Sheet 78 of 105 
P.2 

A-83-27 

IV-J-21 

DOE/FE/60181-2127 

(DE • ) 

FLUIDIZED BED COMBUSTION OF LOW-RANK COALS 

Final Report for the Period Ending June 30, 1986 

By 

M.D. Mann 

D.R. Hajicek 

B.J. Zobeck 

D.P. Kalmanovitch 

M.H. Bobman 

R.J. Kadrmas 

N.S. Grewal 

September 1986 

Work Performed Under Cooperative Agreement No. DE-FC21-83FE60181 

For 

U.S. Department of Energy 

Office of Fossil Energy 

Morgantown Energy Technology Center 

Grand Forks Project Office 

Grand Forks, North Dakota 

By 

University of North Dakota 

Energy Research Center 

Grand Forks, ND 

TECHNICAL INFORMATION CENTER 

U.S. DEPARTMENT OF ENERGY 
P.3 

DOE/ FE/ 6 0181.-2127 -

Distribution Category UC-90 

FLUIDIZED BED COMBUSTION OF LOW-RANK COALS 

Final Report for the Period Ending June-30, 1986 

By 

M.D. Mann, D.R. Hajicek, B.J. Zobeck, D.P. Kalmanovitch 

M.H. Bobman, R.J. Kadrmas, and N.S. Grewal 

University of North Dakota Energy Research Center 

Box 8213, University Station 

Grand Forks, North Dakota 58202 

September 1986 

Technical Project Officer - Harvey M. Ness 

Prepared For 

United States Department of Energy 

Office of Fossil Energy 

Morgantown Energy Technology Center 

Grand Forks Project Office 

Grand Forks, North Dakota 

Under Cooperative Agreement Mo. DE-FC21-83FE60181 
P.4 

TABLE 3.2.3 

CHEMICAL ANALYSIS OF LIMESTONE 

^estone Type 

j-^inpntal Analysis: 

SiO? 

Al2&3 

Fe2°3 

Cao 

MgO . 

N a 2 0 

S03 

Moisture 

Loss on Ignition 

Big Horn, MT 

Percent 

1.6 

0.3 

0.2 

53.9 

0.3 

0.0 

0.2 

0.2 

43.3 

Paris, TX 

Percent 

2.7 

0.4 

0.5 

55.1 

0.3 

0.0 

0.1 

0.2 

40.0 

4. A flue gas system consisting of two cyclones, a heat exchanger, and a 

baghouse; and 

5. A sampling system capable of measuring and recording the O2, COo, CO, N0X, 

SO2, and total hydrocarbon concentrations of the flue gas. 

A more detailed description of the test system has been presented 

previously (35). 

3.2.2 Results and Discussion 

Summaries of selected data points from testing of the four coals are 

presented as Tables 3.2.4, 3.2.5, 3.2.6, and 3.2.7. This data has been 

analyzed using regression analysis to determine the effects of the main 

parameters and the performance characteristics of the AFBC. The regression 

equations and plots of the data follow for the main variables studied. 

3.2.2.1 Sulfur Retention 

Sulfur oxides (S02 and SO3) released during AFBC are controlled by 

reactions with calcium or other alkaline sorbents to form a sulfur-retaining 

solid which is thermally stable at operating conditions. Fluid bed combustors 

firin g high sulfur coals typicall y rely on the addition of limestone as the 

source of calcium for the capture of SO2. Some low-sulfur, low-rank coals 

naturally contain enough alkaline ash for sufficient sulfur capture to meet 

the 1979 New Source Performance Standards (NSPS) without the addition of 

auxiliary sorbent materials. The inherent alkaline components contained i n 

the LRC responsible for sulfur capture are calcium and sodium. The high 

alkaline ash and low sulfur results in high alkali/sulfu r (A/S) ratios for 

many LRCs allowing operation using "inert" bed materials or very low addition 

rates of sulfur-sorbing material. 

35 
tttSmb___—_j_sm,r. 

^4i~^^m---_^v-i^/r,^ 

P.5 

RemoveaOie Door 

Coal Hopper 

Coal and Additive 

Feed System 

Fluidized Bed 

Figure 3.2.1 . Schematic of UflDERC's 2.25 ft 2 AFBC facility . 

36 
P.6 

Multiple regression analysis performed done on the data collected .from the 

tests of the four coals. Terms included in the model equations were selected 

t a 90% confidence level. The following equations were found to best fi t the 

u lfur retention data: 

South Hallsville Texas Lignite (Sample 1) (R2 = 0.123) 

SR = 19.2 - 1.8T 

South Hallsville Texas Lignite (Sample 2) (R2 = 0.620) 

SR = 6.78 - 11.7T + 5.70 - 7.1VD 

Navajo Mew Mexico Subbituminous (R2 = 0.902) 

SR = 49.6 - 8.9T + 37.7A - 9.3A< 

2

 = 0.990) 

4.3TA 

Gibbons Creek Texas Lignite (R 

SR = 71.5 - 3.3T = 45.2A - 2.8T 18.3A' + 2.2TA - 2.7TR 

Sarpy Creek Montana Subbituminous (R = 0.887) 

(Sulfur retention due to the inherent alkal i only) 

SR = 43.0 - 15.6T - 3.1V + 16.5A - 3.1A2 

Sarpy Creek Montana Subbituminous (R2 = 0.887) 

(Sulfur retention with added limestone) 

SR *** 53.2 - 15.6T - 3.1V + 16.5A - 3.1A2 + 2.7R 

[1] 

[2] 

[3] 

[4! 

[5] 

C6] 

where: SR = sulfur retention, pet sulfur in coal feed retained in the bed 

T = (bed temperature (°F) - 1550)/100 

V = (velocity (fps) -5)/2 

D = (stati c bed height (ft ) - 2.5)/0.4 

A = (alkali/sulfu r - 3.5)/3 

R *** -1 for no ash recycle, +1 for 50% ash reinjection 

It is apparent from the analysis that bed temperature and A/S ratio are 

the two main parameters affecting sulfur retention. Sulfur retention i s 

plotted as a function of temperature i n Figures 3.2.2 and 3.2.3 for South 

Hallsville and Sarpy Creek coals, respectively. Figures 3.2.4 and 3.2.5 are 

plots of sulfur retention as a function of temperature at various A/S ratios 

for Gibbons Creek and Navajo coals, respectively. In Figures 3.2.6 and 3.2.7, 

sulfur retention is plotted versus A/S ratio for Sarpy Creek (with and without 

ash recycle) and Navajo coals (different temperatures), respectively. The 

optimum temperature for sulfur retention is typically in the 1400° to 1500°F 

range (35). The plotted data indicate that the optimum temperatures for 

sulfur capture are less than 1450°F for the South Hallsville , Sarpy Creek, and 

Navajo coals. I t is difficul t to discern the optimum temperature for Gibbon 

Creek lignite , though i t appears to occur near 1550°F. Increasing the A/S 

ratio (by adding additional sorbent) i s shown to cause very significant 

increases in sulfur retention. All coals tested except Sarpy Creek 

subbituminous wil l require substantial amounts of added sorbent to meet 1979 

New Source Performance Standards (NSPS). The Gibbons Creek coal required 

limestone addition rates ranging from 17 to 40% of the coal feed rate, 

depending on the test conditions. This equates to added A/S ratios of 3.7 to 

8.9. 

41 
P.7 

'-- • '^'J'T.i'SlZV'r^..*:>-' •:~c*:-*?'^'' >r •?-,*?r;^:,'-...~~S'S'—:.:?%'f^-.l:*?: •^•^rY?'':\^'t.**S^<r.:^^ 

GAS VELOCITY'S FPS, 

EXCESS AIR-20 % 

NO ASH RECYCLE __ 

NO LIMESTONE ADDITION 

1.4 7 1.4.9 

T 1 1—~r 

1.53 1.5S 1.57 

(Thousands) 

BED TEMPERATURE (F) 

1.65 

Figure 3.2.2. 

8 0 

7 0 -

O 60 -

z o 

Iz 

u 

hUJ 

oe 

ac 

3 

u. 

_l 

3 

«fl 

5 0 -

4 0 -

3 0 -

2 0 -

1 0 

Sulfur Retention as a function of temperature at various bed 

depths when burning South Hallsville lignite. 

»«nt Addition & Ash Rscycls 

jhsrsnt Ash Only 

Velocity** 5 ft./sec. 

Excess Air** 20 pet. 

Static Bed (Depth** 2.2 ft. 

Ash Recycle** 50% Coal Feed 

Sorbent Rate** Added A/S of 2.0 

1.44. 1.48 

— I I 1 1 

1.52 1.56 

(Thousands) 

BED TEMPERATURE (°F) 

1.6 0 

— I 

1.64 

Figure 3.2.3. Sulfur retention as a function of temperature showing the 

effect of sorbent addition and ash recycle as compared to 

inherent ash when-burning Sarpy Creek subbituminous coal. 

42 
P.8 

*, 

Z 

g P 

z 

ui 

IbJ 

K 

Q** 

!5 

3 

tn 

rXi J-,r f ^•'-^i ---* : • *!-X* "'•: :\*' "t ^ •••»• -!•:.*-'»' «V^:»Da<^f*'i"V."«; 

100 -»*. 

90 H 

80 

70 -

60 -

50 -

40 -

30 -

VELOCITY'S TO 7 FPS 

EXCESS AIR-20% 

RECYCLE-50% COAL FEED 

BED OEPTH-2.1 FT 

A/S=6.7 

A/S=3.7 

i 1 1 1 1 i 1 1 1 1 1 r 

1.51 1.53 1.55 1.57 1.59 1.61 1.63 1.65 

(Thousands) 

BED TEMPERATURE (F) 

Figure 3.2.4. Sulfur retention as a function of temperature at various A/S 

ratios when-burning Gibbons Creek Lignite. 

100 

90 4 

80 A 

z 

o 1-

z Ul 

HUl 

oc 

0_ 

3 

l i . 

_1 

3 

V) 

7 0 

60 

5 0 

4 0 

3 0 

2 0 

10-1 

~l 1 1 1 i 1 1 1 r 

1.45 1.47 1.49 1.51 1.53 1.55 1.57 1.59 1.61 1.63 1.65 

(Thousands) 

TEMPERATURE (F) 

Figure 3.2.5. Sulfure retention as a function of temperature at various A/S 

ratios when-burning Sarpy Creek subbituminous coal. 

43 
P.9 

-• -'v''j^irrx^.-r'_.-"_^"\-..\,- p^-, 

100 

z 

o 

H 

z 

UJ 

I -

UJ 

IE 

K 

3 

Lu 

-J 

3 

tf) 

9 0 -

8 0 -

7 0 -

60 -

50 -

4 0 

1.00 

Ash Rsinlsetlon 

Ash R«In|«ctIon 

3.0 0 

T 1 -* " 

9.0 0 

T T 

7.0 0 

ALKAU-TO-SULFUR RATIO 

Bed Temperature*: U50 °P 

Velocity** 5 ft./sec. 

Static Bed Depths 2.2 ft. 

Excess Airs 20 pet. 

• i i i i 

9.0 0 11.00 13.0 0 

Figure 3.2.6. Sulfur retention as a function of A/S ratio showing the effect 

of ash recycle when-burning Sarpy Creek subbituminous coal. 

z 

o 

Ui I— 

Ui 

oc 

or 

3 

3 

tn 

ALKAU-TO-SULFUR RATIO 

Figure 3.2.7. Sulfur retention as a function of A/S ratio of various bed 

temperatures when-burning Navajo subbituminous coal. 

i 

44