Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979
F ( t ) = time function, eq 3 k = kinetic rate constant, (kPa-min)-' k , = gas-solid mass transport coefficient, (kPa-min1-l PO, = oxygen partial pressure in gas stream, kPa (PO,)' = inlet oxygen partial pressure, kPa PO,)^ = oxygen partial pressure at solid surface, kPa r = reaction rate, mg-mol of char consumed/min P, = reaction rate, fraction of char converted/min R = gas law constant, 8.3144 J/mol-K t = time, min E = average residence time, min T = temperature, K X = fraction of char converted Literature Cited Burnham, A. K., Lawrence Livermore Laboratory, Preprint UCRL-80551 (1978). Burwell, E. L., Jacobson, I. A,, U . S . Bur. Mines Tech. frog. Rept., TPR85 (1974). Burwell, E. L., Jacobson, I. A., paper S E 5335, presented at Rocky Mtn. Regional Mtg., SOC.Petr. Engrs., Denver, Colo., April 7-9, 1975.
667
Campbell, J. H., Koskinas, G. H. Gallegos, G., Gregg, M., Lawrence Livermore Laboratory, Rept. UCRL-82032 (1978). Campbell, J. H.,Burnham, A. K., Lawrence Livermore Laboratory, Preprint UCRL-80545 (1978). Campbell, J. H., Koskinas, G. H., Stout, N. D., In-Situ, 2(1), 1 (1978). Dockter, L. AIChE Symp. Ser., 72, 24 (1976). Duir, J. H., Deering, R. F., Jackson, H. R., Hydrocarbon Process., 147 (May 1977). Haynes, W. P., Gasior, S. J., Forney, A. J., "Catalysls of Coal Gasification at Elevated Pressure", Bu Mines, Pittsburgh, Pa., 1972. Lewis, A. K., Gilliland, E. R., Hiskin, H., Ind. Eng. Chem., 45, 1697 (1953). Mallon, R. G., Braun, R. L., Lawrence Livermore Laboratory, Preprint UCRL-77829 (1976). Schachter, Y., J . Catal., 11, 147 (1968). SlettvoM, C. A. Biermann, A. H., Bunham, A. K., Lawrence Livermore Laboratory, Report UCRL-52619 (1978). Smith, J. M., "Chemical Engineering Kinetics", 2nd ed, McGraw-Hill, New York, N Y . 1970.
Son/, Y:, Thomson, W. J., "Proceedings of the 11th Oil Shale Symposium", p 364, Colorado School of Mines Press, 1978.
Received for review September 13, 1978 Accepted May 14, 1979
The Effect of Solvent on Solvent Refined Coal Denitrification David W. Staubs, Ronald L. Miller, and Howard F. Silver' Mineral Engineering Department, University of Wyoming, Laramie, Wyoming 820 7 7
Robert J. Hurtubise Chemistry Department, University of Wyoming, Laramie, Wyoming 8207 1
The oxidation of organic nitrogen in solvent refined coal (SRC) may lead to excessive NO, emissions. This study was designed to investigate the effect of solvent characteristics on the nitrogen content of SRC. Both total nitrogen analyses and nitrogen type analyses were performed on the solvents used and on the SRC produced in a batch autoclave by the hydrogenation of Wyodak coal in the presence of a solvent.
Introduction A major problem that may tend to limit the use of the extensive U S . coal reserves as an energy source alternative to our diminishing natural gas and petroleum supplies is the emission of pollutants including particulate matter, sulfur dioxide, SOz, and nitrogen oxides, NO,. One means of reducing the emission of pollutants from coal is to eliminate the pollutants before combustion. This can be accomplished by dissolving the coal in the presence of hydrogen and a coal-derived liquid solvent boiling between 450 and 700 K a t elevated pressures and temperatures to form solvent refined coal (SRC). Other approaches include gasifying the coal with air and burning the low-Btu gas produced as well as cleaning the stack gas after combustion. Coal liquefaction processes were initiated by the Germans on a large scale in the 1920's and are currently being carried out in pilot plants by the Pittsburg and Midway Coal Mining Company (PAMCO),by Southern Company Services, Inc., as well as by others. Most studies of the SRC process have concentrated on sulfur reduction and mineral matter removal. The filtered or centrifuged SRC is a low particulate matter, low sulfur fuel which melts a t about 450 K. It has a fairly uniform heating value of about 37 MJ/kg (16000 Btu/lb). On the other hand, SRC generally contains a higher concentration of organically 0019-7882/79/1118-0667$01.00/0
bound nitrogen than the coal from which it is made. Consequently, there is some question as to whether or not NO, emission standards can be met while burning SRC. High NO, levels cause eye irritation, respiratory disease, fade dyes, and cause the deterioration of fibers. NO, emissions are formed not only from the oxidation of organically bound nitrogen, called fuel NO,, but also from the high-temperature oxidation of nitrogen in the air, called thermal NO, (Martin, 1976). Burner and combustion modifications designed to reduce thermal NO, by lowering combustion zone temperatures and minimizing the available air do not always result in the efficient use of the fuel. The lowest practical excess air levels are dictated by the need to limit products of incomplete combustion such as carbon monoxide, soot, and unburned hydrocarbons (Lachapelle et al., 1976). An SRC combustion test of 3000 tons of a PAMCO prepared Kentucky coal-derived SRC containing about 1.6 w t % nitrogen has recently been conducted in a 22.5 MW boiler a t Plant Mitchell Station of the Georgia Power Co. A Babcock and Wilcox modified dual register, water-cooled burner was used in the Plant Mitchell test. A two-stage combustion process was employed in the experimental burner with a fuel-rich first stage and combustion air-rich second stage. NO, emissions were maintained a t a level of about 350 ppm (0.4 lb/106 Btu) (Carr, 1977). Currently, 0 1979
American Chemical Society
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Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979
Table I. Wyodak Coal Analysis Proximate, Wt %, MF volatile matter 43.01 fixed carbon 49.37 ash 7.62 Ultimate, W t %, MF hydrogen 4.74 carbon 68.23 nitrogen 0.93 oxygen 18.03 sulfur 0.45 ash 7.62 Screen Analysis (Tyler), Wt % 27.4 65/100 16.2 11.1 100/150 150/200 8.8 2001325 9.6 3 25/PAN 26.9 t 65
the EPA has set the NO, emission standards a t 500 ppm (0.7 lb/106 Btu) for coal-fired utility boilers. However, research goals are 200 ppm of NO, (0.3 lb/106 Btu) by 1980 and 100 ppm of NO, (0.15 lb/106 Btu) by 1985 (Lachapelle e t al., 1976). Despite the favorable NO, emission results a t Plant Mitchell, the test also resulted in initial excessive particulate matter emissions through an electrostatic precipator which had been installed in 1946. Although the carbon losses were essentially the same for both the SRC and for Kentucky coal burned in the experimental unit a t Plant Mitchell, the quantity of ash from the SRC test was much lower than the quantity of ash from the coal test. As a result, the concentration of carbon on the SRC ash was much greater than the concentration of carbon on the coal ash. This increased carbon concentration increased the electrical conductivity of the particulate matter emitted from the combustion of SRC, decreasing the effectiveness of the electrostatic precipitator used in the initial test. Unfortunately, improved fuel-air mixing to reduce the carbon concentration in the particulate matter emissions from SRC combustion may also increase thermal NO, emissions. The use of an electrostatic precipitator of more modern design in later phases of the SRC combustion tests resulted in particulate matter emissions which met EPA standards. However, it remains to be demonstrated that adequate control of both particulate and NO, emissions can be attained simultaneously while burning high nitrogen content SRC without some additional stack gas cleanup. NO, in stack gas can be catalytically reduced with NH3 to form NP. The removal of NO, by stack gas cleanup has been proven in Japan on a plant size scale but has also been shown to be extremely expensive (Ushio, 1975). Another possible means of reducing NO, emissions to meet research goals is to reduce the organically bound nitrogen content of the SRC. Organically bound nitrogen is a major source of NO, emissions (Pershing et al., 1975; Turner et
al., 1972; Bartok et al., 1972; Haebig et al., 1975). The objective of this study has been to determine the effect of different coal-derived solvents at one set of reactor operating conditions on both the concentration of total fuel nitrogen as well as the concentration of types of different fuel nitrogen compounds in a Wyodak coal-derived SRC. The total concentration of nitrogen in SRC's produced using different solvents was measured using a modified Kjeldahl procedure while estimates of the concentrations of different types of nitrogen compounds were made using nonaqueous potentiometric titrations combined with infrared analyses of the benzene soluble portions of the SRC's. Materials Coal. Wyodak coal from the Roland and Smith seams in the Belle Ayr Mine of the Amax Coal Co. used in this work was supplied by Catalytic Inc. from the Southern Company Services Inc. SRC plant in Wilsonville, Ala. Analysis of the coal used is presented in Table I. Solvents. Coal-derived solvents from two different sources have been used in this work. The first coal liquid studied was a 450-750 K boiling range Wyodak coal recycle solvent supplied by Catalytic Inc. from the Southern Company Services Inc. SRC plant. This solvent was designated F-1. The F-1 solvent was then hydrogenated a t two different levels of severity for 1h over a Co-Mo on A1203 catalyst (Nalcomo 471) supplied by the Nalco Chemical Co. The mildly hydrogenated solvent was designated F-2 while the more severely hydrogenated solvent was designated F-3. All three of these solvents were then distilled to moduce light fractions designated F-1LT. F-BLT, and F-3LT, and heavy fractions designated F-1HV; F-BHV, and F-3HV. In addition to the Wyodak coal-derived solvents, coal tars from a Pittsburgh seam coal supplied from the Clairton works of the U S . Steel Corp. were studied. One coal tar with a boiling range of 500-590 K was designated F-4 and a second coal tar with a boiling range of 590-630 K was designated F-5. Properties of the solvents studied are presented in Table 11. Properties of the hydrogen used are presented in Table 111. Equipment a n d Procedure Hydrogenation. Before initiating the coal liquefaction runs, a series of hydrogenation runs were made to modify the Wilsonville solvent F-1 in a 2.0-L Autoclave magnedrive stirred batch reactor. The hydrogen donor capacity of the Wyodak coal-derived solvent was increased by first hydrogenating the solvent in a series of runs under an initial hydrogen pressure of 13.8 MPa (2000 psi) a t 644 K for 1 h over a Co-Mo on A1,0, catalyst (Nalcomo 471) which had been thermactivated at 810 K for 2 h in a muffle furnace. The product was designated F-2. In a second series of runs the F-1 solvent was hydrogenated under an initial hydrogen pressure of 20.7 MPa (3000 psi) a t 700 K for 1h over thermactivated Nalcomo 471 catalyst resulting
Table 11. Properties of Solvents Studied solvent ult. anal., wt % C H N S
0 VABP,
KO
F -1
F -2
F-3
F-1LT
F-2LT
F-3LT
F-1IIV
F-PHV
F-3HV
F-4
F -5
87.95 8.49 0.49 0.13 2.94 559.0
87.92 9.07 0.45 0.12 2.44 549.0
88.43 9.25 0.34 0.04 1.94 536.0
86.74 9.07 0.23 0.15 3.81 508.0
86.95 9.19 0.22 0.00 3.64 507.0
87.82 9.55 0.25 0.00 2.38 499.0
88.07 8.46 0.70 0.31 2.46 601.0
88.08 8.50 0.60 0.10 2.72 598.0
88.97 8.81 0.46 0.06 1.70 602.0
89.25 7.31 1.27 0.75 1.42 553.0
90.38 6.51 1.03 0.81 1.27 626.0
Volumetric average boiling point.
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979 669
Table 111. Properties of Hydrogen extra dry 99.8% (min.) -75 " F (max.) 2000 psig
grade purity dew point cylinder pressure
in a product designated F-3. Each reactor charge consisted of 60 g of catalyst and 1000 g of solvent. The initial F-1 solvent and the two solvents produced by hydrogenation of F-1 were individually distilled in an ASTM D-1160 apparatus. The solvents were distilled into a fraction boiling below 535 K and a second fraction boiling above 535 K. The coal tar solvents were used directly as received. Coal liquefaction studies were then initiated by charging 300 g of coal-derived solvent and 150 g of dried coal to the Autoclave reactor. Compressed hydrogen was added to the reactor until a cold reactor pressure of 13.8 MPa (2000 psi) was reached. If the pressure of the reactor showed less than 0.2 to 0.4 MPa (25 to 50 psi) decrease over a 1 2 h period after an initial stirring period, the run was initiated. The reactor was heated using electric heaters to 715 K a t a rate of about 3 K/min. As soon as the desired reaction temperature had been reached, the electric heaters were turned off, cooling air was directed over the outside of the reactor and into a coil within the reactor, and the reactor was allowed to cool to room temperature. The gases in the reactor were then vented to sample tanks and analyzed using a Hewlett-Packard H P 5840A chromatograph. T h e liquid product from the reactor was siphoned into a glass flask and any solid particles remaining in the reactor were removed with a hand scraper and added to the liquid in the glass flask. The total mixture was then centrifuged at 1500 rpm to separate the liquids and solids. In these runs, liquid from the centrifuge, called decant oil, was essentially ash free, indicating good solid separation. Distillation of Products. Approximately 50 g of toluene was added to 100 g of decant oil in a 500-mL distilling flask. The mixture was allowed to boil for over 12 h in a Dean-Stark apparatus following ASTM D-95 procedures to remove any water contained in the decant oil. The water-free decant oil was then distilled in a modified ASTM D-86 apparatus with a vacuum jacketed ASTM D-1160 head to remove the toluene and the oil boiling below 450 K at 0.1 MPa (14.7 psi). The distillation residue was cooled and a vacuum ASTM D-1160 distillation was initiated. A vacuum of approximately 260 P a (2 mmHg) was applied to the distillation flask. Cuts a t 450-535 K, 535-615 K, and 615-700 K were taken. The solid-free vacuum distillation residue product boiling above 700 K was called solvent refined coal (SRC). A portion of the SRC was extracted with benzene in a Soxhlet extractor. Both the total SRC and the benzene insoluble SRC were analyzed for nitrogen content and the benzene soluble SRC was used in nitrogen type analyses.
Kjeldahl Analysis. The nitrogen content of all liquid and solid samples (decant oil, SRC, feed solvent, coal, centrifuge residue, and benzene insoluble SRC) was obtained by use of a modified Kjeldahl method (ASTM 3179). In this procedure a sample of about 1g was digested in a boiling mixture of sulfuric acid and potassium sulfate with elemental mercury as the catalyst to convert the nitrogen into ammonium salts. The ammonia produced when caustic NaOH solution was added to the ammonium salt solution was collected in a 5% boric acid solution and titrated with 0.1 N HC1 to the end point. Nitrogen Type Analyses. Samples of the solvents used and of the benzene soluble fraction of the SRC were analyzed for nitrogen types using nonaqueous potentiometric titrations and infrared analyses (Koros et al., 1967). The solvents used in the nonaqueous titrations were reagent grade glacial acetic acid, reagent grade acetic anhydride, and 0.1 M acetic anhydride in acetic acid, termed mixed solvent. Reagent grade benzene was used as a diluent in all analyses. The procedures used were essentially the same as had been used in this laboratory for the analyses of shale gas oils (Wang, 1973; Staubs, 1977). When the titration data were combined with the data from the infrared analyses, it was possible to classify the nitrogea compounds into the following types: quinolines (including pyridines, quinolines, and acridines); aryl amines (including 1,2,3,4-tetrahydroquinolines,2,3-dihydroindoles, and anilines); indoles (including pyrroles, indoles, and carbazoles); primary and secondary alkyl amines; amides (including quinolones and oxindoles); and unidentified compounds. Two changes were made in the procedures used for nitrogen type analyses of shale gas oils by Wang. First, the benzene soluble SRC samples were filtered through Whatman 42 filter paper to remove suspended solids, rotavaporized to remove benzene, and then dissolved in CC14 for the infrared analyses. Shale gas oil samples did not require this step. Further, only 50% of the indole type compounds found by infrared analysis were assumed to titrate as weak bases in acetic anhydride rather than the 70% assumed in the shale oil studies. Both these figures were based on results of studies (Okuno e t al., 1965) in which it was found that pyrroles were only 30% titratable while indoles were 65% to 80% titratable. However, if 70% of the coal liquid indole types were assumed to be titratable as was done in the shale oil studies, negative values of amide concentrations were obtained. Results Solvent Nitrogen Types. In the initial phases of this study, nitrogen type analyses were performed on the solvents used. The results of these solvent nitrogen analyses are presented in Table IV. Comparison of the results obtained for the F-1, F-2, and F-3 solvents in Table IV leads t o some interesting conclusions. First, as hydrogenation serverity increases, the
Table IV. Nitrogen Type Analyses (Wt 7%) in Solvents Studied nitrogen type
-
quinolines aryl amines primary and secondary alkyl amines indoles amides unidentified total
' Note:
F-1LT F-2LT
solvent F-3LT
F -1
F -2
F-3
0.310 0.036 0.062
0.186 0.078 0.062
0.109 0.177 0.009
0.170 0.011 0.000
0.118 0.043 0.026
0.040 0.181 0.010
0.081 0.006 (0.005)a 0.49
0.082 0.013 0.029 0.45
0.079 (0.018) (0.016) 0.34
0.030 0.000 0.019 0.23
0.021 0.006 0.006 0.22
0.033 (0.019) 0.005 0.25
figures in parentheses indicate negative values.
F-1HV F-2HV F-3HV
F-4
F-5
0.407 0.037 0.010
0.245 0.126 0.050
0.161 0.063 0.002
0.851 0.045 0.057
0.539 0.000 0.051
0,099 0,011 0.136 0.70
0,115 0.016 0.048 0.60
0.111 0.071 0.052 0.46
0.258 0.028 0.031 1.27
0.144 (0.046) 0.342 1.03
670
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979
Table V. Nitrogen as Percent of Total Identified Nitrogen
2.0
A
investigator
GFETC wt % N in Wyodak recycle solvent nitrogen type quinolines indoles aryl amines alkyl amines amides total
Univ. Wyo.
F3
1.8
v Coal
U
0.64
0.49 62.6 16.4 1.3 12.5 1.2
-___ ____ -
-
100.0
100.0
concentration of the relatively refractory quinoline type compounds decreases, presumably forming aryl amines. On the other hand, the indole type compound concentration remains relatively constant with increasing hydrogenation severity. These results may be compared with pure component studies (Flinn et al., 1963) in which it was found that amines and anilines react rapidly to form ammonia while indole is much less reactive and quinoline is the most difficult to denitrify. The differences between the relative reactivities of nitrogen type compounds found in this work on mixtures as compared to pure nitrogen compound studies can be attributed t o differences in the competitive absorption characteristics of basic nitrogen compounds on acidic catalyst supports. Finally, a comparison of the total nitrogen in the F-1 solvent and the F-3 solvent produced by severely hydrogenating F-1 solvent over a Co-Mo on A1,0, catalyst is indicative of the difficulties that can be expected in removing nitrogen even from distillable coal-derived oils. In similar work, nitrogen compounds in coal-derived liquids were examined by means of mass spectrometry at the Grand Forks Energy Technology Center (Schiller, 1977). A summary of the probable compound types regrouped into nitrogen classes obtained a t Grand Forks on a Wyodak coal-derived recycle solvent, similar to the F-1 solvent examined in this work, is compared in Table V with results of this work. SRC Nitrogen Concentration, An analysis of SRC total fuel nitrogen concentration as a function of solvent properties was undertaken to determine which, if any, of the solvent properties were most effective in reducing this nitrogen. Solvent boiling above 700 K could not be separated from SRC produced from Wyodak coal as this SRC had an initial boiling point of 700 K. Consequently, only solvents containing less than 8 wt % material boiling above 700 K were included in this evaluation. Solvent properties evaluated included weight percent hydrogen in the solvent, aliphatic to aromatic hydrocarbon ratios as determined by infrared analyses, tetralin concentration, solubility parameters, volumetric average boiling points, and specific gravities. Of the variables studied, the volumetric average boiling point, VABP, seemed to give the best correlation. The nitrogen concentration of the SRC produced shows a decreasing trend as the VABP of the solvent increases (Figure 1). On the other hand, analysis of the detailed results reported by Silver and Hurtubise indicates that the grams of nitrogen in the SRC show an increasing trend with increasing solvent VABP (Silver and Hurtubise, 1979). This reflects the fact that nitrogen concentrations in coal derived solvents seem to be greater in the higher boiling fractions. However, the grams of SRC produced generally increased a t a more rapid rate than the grams of nitrogen in the SRC with increasing solvent VABP, resulting in the observed decrease in the concentration of nitrogen in the SRC.
Tar
VI
e
65.9 12.9 21.2
FI
1
1.6
z ;r
ji
1.4
1.2
A
-
I
1
I
500
525
I
550
VABP OF
I
I
I
575
600
625
SOLVENT, I:
Figure 1. SRC N2 concentration as a function of solvent.
Further, the results reported by Silver and Hurtubise show that, on the average, the total grams of nitrogen in the SRC and in the solid residue are very nearly the same as the grams of nitrogen in the coal charged to the Autoclave reactor. These results suggest that the grams of nitrogen in the solid residue decrease with increasing solvent VABP. However, in this case, the concentration of nitrogen parallels the grams of nitrogen in the solid residue and also shows a decreasing trend with increasing solvent VABP. As the grams of nitrogen in the SRC and solid residue are very nearly the same as the grams of nitrogen charged with the coal, any ammonia produced in the reaction must have originated from the nitrogen introduced with the solvent. This suggests that lower boiling range nitrogen compounds are more easily denitrified than higher boiling range nitrogen compounds. As shown in Figure 1,lines of different slopes had to be drawn through the Wyodak coal-derived solvent data and the coal tar data. The difference between the two lines may be due to the hydrogen content of the solvents. The coal tar solvents had hydrogen contents ranging from 6.5 to 7.3 wt % while the Wyodak coal-derived solvents had hydrogen contents ranging from 8.5 to 9.6 wt 70. In order to more completely define the effect of solvent characteristics on the denitrification of SRC, experiments were performed to quantitatively distinguish between the types of fuel nitrogen present in the SRC produced from the Wyodak coal-derived solvents. This information should be of value to others who wish to continue studies of the combustion characteristics of model nitrogen compounds. Significant results have been reported in this area (Axworthy et al., 1976; Martin and Berkan, 1972; Turner et al., 1972; Haebig et al., 1975). As benzene was used as a cosolvent in the nonaqueous potentiometric titrations, rather than distilling benzene from the total SRC Soxhlet extract and then rediluting the benzene soluble SRC with benzene, samples of the total SRC Soxhlet extract were used directly. The concentration of benzene soluble SRC and the concentration of nitrogen in this SRC were determined indirectly by material balances. Unfortunately, a very small but detectable amount of material that was soluble in benzene boiling in the Soxhlet was not soluble in benzene a t ambient temperatures at which the titrations were carried out. As a result of the indirect manner in which the total nitrogen in the benzene soluble SRC was determined and as a result of the temperature effect on the benzene soluble SRC, a large fraction of the benzene soluble SRC nitrogen could not be specifically identified. However, the unidentified nitrogen is probably of the same general composition as the identified nitrogen. Results of the benzene soluble SRC nitrogen type studies are presented in Figures 2 through 5. The quinoline type
Ind. Eng. Chem. Process Des. Dev., Vol. 18, No. 4, 1979 671
pL-44 1 I
500
I 1 500
525
,l
I
I
575
600
I
625
Figure 2. Quinoline type nitrogen as a function of solvent.
i
4 1
L d 500
525
I
1
I
I
550
575
600
625
VABP OF
I
SOLVENT, K
Figure 3. Indole type nitrogen as a function of solvent. A
F1 F2
F3
500
525
,
A
550 575 VABP OF SOLVENT. K
575
600
625
Figure 5 . Aryl amines as a function of solvent.
SOLVENT, K
VABP OF
550
VABP OF SOLVENT, K
T -
550
525
1
I
600
625
Figure 4. Primary and secondary alkyl amines as a function of solvent.
nitrogen and indole type nitrogen compounds were found to be major nitrogen components in the benzene soluble SRC. The quinoline type accounts for approximately 40% of the identifiable nitrogen while the indole type accounts for approximately 10 to 30% of the nitrogen. As shown in Figures 2 and 3, the weight fraction of benzene soluble nitrogen found as quinolines and indoles seems to go through a maximum as the VABP of the Wyodak coalderived solvent increases. On the other hand, as shown in Figures 4 and 5, the weight fraction of benzene soluble nitrogen found as amines, including both the primary and secondary alkyl amines as well as aryl amines, seems to go through a minimum as the VABP of the solvent increases. Finally, the results obtained for amide type nitrogen showed generally less then 5 wt % of this class of nitrogen in the benzene soluble SRC for all Wyodak coal-derived solvents tested. Data points shown on these figures are average values from repeated analyses of the indicated nitrogen types in benzene soluble SRC obtained from two or more independent reactor runs. All results used to determine these
averages lie within the indicated intervals. A polynomial regression analysis of the averaged data points was used to analyze the effect of solvent VABP on nitrogen type concentrations in benzene soluble SRC. Multiple regression correlation coefficients for the curves obtained ranged from 0.52 to 0.89. Conclusions It appears that the concentration of nitrogen in SRC decreases as the boiling range of the solvent used to liquefy Wyodak coal increases. Based on the limited data available on the combustion characteristics of nitrogen compounds, it appears that decreasing the total nitrogen in the SRC will result in lowering NO, emissions. Quinoline type molecules appear to be the major nitrogen class in both coal-derived solvents and in SRC. However, the differences in the nitrogen type distribution of the SRC’s produced in this work should not significantly affect the combustion characteristics of the fuel. The final determination of whether an SRC fuel will meet NO, emission standards as well as particulate emission standards without some stack gas cleanup will depend on the mineral matter content of the SRC as well as the type of burner design and the combustion modifications employed. Acknowledgment Larry Jackson of the Laramie Energy Technology Center assisted in IR analysis, Jane Thomas, University of Wyoming, assisted in product analysis procedures, and Pete Gilman and Norm Stewart of EPRI provided helpful comments. Literature Cited Axworthy, A. E.; Schneider, G. R.; Shuman, M. D.; Dayan, V. H., Feb 1976, EPA Report 60012-76-039. Bartok, W.; Crawford, A. R.; Piegari, G. T. AIChESymp. Ser. 1972, 68(126), 66. Carr, R., EPRI, personal communication, 1977. Flinn, R. A.; Larson, 0. A.; Beuther, H. Pet. Refiner 1963, 42, 129. Haebig, J. E.; Davis, B. E.; Dzuma, E. R. Am. Chem. SOC. Div. Fuel Chem. Prepr. 1975, 20(1).203. Koros,.R. M.; Bank, S.;Hofmann, J. E.; Kay, M. I. Am. Chem. SOC. Div. Pet. Chem. Prepr. 1967, 12(4), 8165. Lachapelle, D. G.; Bowen, J. S.;Stern, R. D. AIChESymp. Ser. 1976, 72, (156), 263. Martin, G. B.; Berkan, E. E. AIChE Symp. Ser. 1972, 68(126), 45. Martin, G. B. June 1976, EPA Report 600/2-76-149. Latharn, D. R.; Haines, W. E. Anal. Chem. 1965, 37(1), 54. Okuno, I.; Pershing, D. W.; Martin, G. B.; Berkan, E. E. AIChESymp. Ser. 1975, 71, 148. Schiller, J. E.; Anal. Chem. 1977, 49(14), 2292. Silver, H. F.; Hurtubise, R. J. April 1979, DOE Final Report for Contract No. EX-764-0 1-2367. Staubs, D. W. M.S. Thesis, University of Wyoming, Laramie, Wyo., 1977. Ushio, S.;Chem. Eng. 1975, 15(82), 70. Turner, D. W.; Andrews, R. L; Siegmund, C. W. Combustion 1972, 2(44), 21. Wang, N. L. M.S. Thesis, University of Wyoming, Laramie, Wyo., 1973.
Received for review September 25, 1978 Accepted May 9, 1979 This study was supported by funds obtained from the Office of University Activities, U.S. Department of Energy, under Contract Number EX-764-01-2367.
