A boil-off calorimeter for the measurement of the enthalpy of coal

A Freon-11 (CFCI3) reference fluid boil-off calorimeter was developed to measure the enthalpy of coal-derived liquids and representative model compoun...
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Ind. Eng. Chem. Process Des. Dev. 1984, 23, 267-271

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A Boil-off Calorimeter for the Measurement of the Enthalpy of Coal- Derived Liquids John R. McConneil, Roberta R. Fleckenstein, Arthur J. Kidnay, and Victor F. Yesavage' Department of Chemical and Petroleum Refining Engineering, Colorado School of Mines, Golden, Colorado 8040 1

reference fluid boikff calorimeter was developed to measure the enthalpy of coalderived liquids and representative model compounds at temperatures between 18.3 OC (65 O F ) and 400 O C (750 O F ) and pressures up to 10500 kPa (1500 psia). Results using water and n-heptane as the test fluids indicate a maximum error of f0.5% with an average error of 1.5 kJ/kg (0.6 Btu/lb,). A Freon-1 1 (CFCI,)

Introduction Coal-derived liquids are a new and vital class of industrial compounds but have thermodynamic properties that are largely unknown and presently unpredictable. Thermodynamic properties are needed to make more efficient design calculations of equipment using these new liquids. Enthalpy measurements offer significant information to the design engineer since they can be used directly in the determination of process heat loads. The purpose of this work is to discuss an experimental apparatus capable of making enthalpy difference measurements accurate to within f0.5% on coal-derived liquids. The apparatus was first tested by measuring the enthalpy of water over the pressure range of 700-10 500 kPa (100-1500 psi) and a temperature range of 18.3-290 (65-550 O F ) and comparing the data obtained with that in the literature. The calorimeter was further evaluated using n-heptane as the test fluid in order to obtain enthalpy data across a vapor-liquid phase transformation. The equipment has subsequently been used to measure the enthalpies of coal-derived liquids and model compounds representative of these liquids. Experimental Apparatus A comprehensive review of calorimetric methods and data interpretation for the enthalpy of fluid mixtures under pressure has been presented recently (Ng and Mather, 1978). A detailed drawing of the calorimeter is presented in Figure 1, and the schematic diagram of the flow system is shown in Figure 2. The first law of thermodynamics applied to a flow calorimeter with negligible potential and kinetic energy effects at steady state is

where HT p 2 and HTlplrepresent the enthalpies per unit mass of t i e fluid at outlet conditions (approximate reference conditions) and inlet conditions respectively, Q is the net rate of heat transfer to the fluid, W is the net rate of work output, F is the mass flow rate, and x represents a constant overall composition. In a boil-off calorimeter heat is transferred from the system containing the flowing test fluid to a boiling reference fluid. Thus for a boil-off calorimeter Q = -FJ, - 4 ; W = 0 where F, is the boil-off rate of the reference fluid, A, is the reference fluid enthalpy change on vaporization, and q is the net rate of heat loss from the calorimeter-reference fluid system which represents a limitation in the accuracy 0196-4305/84/1123-0267$01.50/0

of a measurement. For a boil-off calorimeter eq 1 thus becomes

From eq 2, one can see that the heat loss error term is q / F and is thus inversely proportional to flow rate. Furthermore, as flow rate decreases, the maintenance of a steady measurable flow rate becomes more difficult. Thus most flow calorimeters, including this one, have been developed to operate at flow rates in the order of l cm3/s where heat losses are minimal and reproducible flow rate measurements can be obtained (Nelson and Holcomb, 1958; Lenoir et al., 1970a). The enthalpy differences are obtained at constant total composition between a given temperature and the reference fluid boiling point temperature. Freon 11 (CFCl,) is used as the reference fluid in this apparatus since it boils near room temperature at 18.3 OC (65 O F ) in Golden, CO. The calorimeter was constructed to operate at essentially constant pressure, and thus, the final results consist of enthalpy differences at approximately constant pressure levels between the inlet temperatures and 18.3 "C. In the two-phase region the measured enthalpy values represent the total enthalpy of a vapor-liquid mixture with a combined composition equal to that of the original sample. The calorimeter as shown in figure 1consists of three chambers. The inner chamber constitutes the boiling bath. The heat exchanger, a 35 ft long coil of 1/8 in. 0.d. stainless steel tubing provides more than adequate heat transfer area to cool the sample to within 0.5 "C of the Freon 11 bath. The Freon vapors that boil off from the inner chamber and leave the calorimeter through the center tube travel through a demister before leaving the inner chamber in order to remove any entrained liquid. The middle chamber which also contains boiling Freon acts as an insulating barrier by eliminating any temperature difference between the inner chamber and its surroundings. The middle chamber also increases the capacity of the calorimeter for holding Freon 11 since the two chambers are connected by a Freon feed tube. The outer chamber is evacuated by the vacuum system to a pressure of less than 7X mmHg (0.09 Pa). The flow system was designed for use with corrosive, relatively unstable coal-derived liquids, and for running with the relatively small samples (several liters) of coalderived liquids which were available. For virtually all of the system l/s-in. outside diameter 316 stainless steel tubing was used. The possibility of two-phase flow developing in the sample line required a constant downward movement of the stream once the heating process began 0 1984 American Chemical Society

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Ind. Eng. Chem. Process Des. Dev., Vol. 23, No. 2, 1984

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Figure 3. Difference between experimental enthalpy values and Keenan et al. "Steam Tables" (1969) values as a function of enthalpy for liquid water.

Figure 1. Flow calorimeter.

1 %:::

----REFERENCE

-

FLU10

CIRCUli

SAMPLE CIRCUIT

Figure 2. Flow diagram of the recycle flow system.

to prevent trapping of the liquid in a low spot of the system. The sample is pumped from the surge tank using a Milton-Roy dual-diaphragm metering pump, with the ability to level out the pulsating flow with its double action. An in-line stainless steel 60-pm filter is located after the pump to remove particles from the liquid. After the filter, a bladder accumulator incorporates a nitrogen filled bag to absorb the force of the pump stroke and minimize pressure fluctuations. To minimize sample decomposition, the test fluid is preheated gradually using a 2 5 f t preheater coil in a fluidized bed sand bath. The fluid is heated to the desired inlet temperature with an in-line bayonet heater, controlled by a three mode controller using an in-line thermocouple. The inlet and outlet pressures are measured with two Heise bourdon tube gauges. The inlet and outlet temperatures are measured with in-line platinum resistance thermometers. A nitrogen dome loaded back-pressure regulator is used to maintain the system pressure. The sample is then returned to the surge tank or to the collecting tube by a three-way valve. An in-line platinum resistance thermometer measures the temperature of the Freon 11vapor as it leaves the calorimeter. The

Freon 11vapor exit tube is heated to prevent condensing of the vapor before it reaches the condenser. The subcooled condensed liquid flows past a vent, through a vapor trap, to a three-way valve which directs flow to either the return heater or the collection tube. The return heater is used to heat the sub-cooled liquid Freon to the saturation point before allowing it to enter the calorimeter. The boil-off from the calorimeter outer chamber is condensed in the small condenser and returned to the calorimeter together with condensed vapors from the return heater. The platinum resistance thermometers used for the measurement of the inlet and outlet oil temperatures were custom made, 100-ohm nominal resistance units sheathed in 316 stainless steel. These thermometers are located at the surface of the inner Freon chamber. The thermometer outputs were measured with a Fluke digital volt/ohm meter. Calibration over the temperature range of interest was accomplished with a Leeds and Northrup 8167-25-B platinum thermometer which was in turn calibrated by the manufacturer on IPTS-68. The temperature measurementa are believed accurate to f0.05 OC. The inlet and outlet pressures were measured with Heise gauges, calibrated by the manufacturer, with an accuracy of f14 kPa (2 psia). The weights of Freon and oil collected during an experimental measurement were determined to f0.05 g. Further details of the equipment design are presented elsewhere (McConnell, 1976; Andrew, 1978). Results For evaluation of the calorimeter a series of enthalpy measurements on compressed liquid water were taken, and the results are presented in Table I and Figwe 3. In Table I, the enthalpy differences are between the inlet temperature and an outlet temperature that was within 0.5 O C (1O F ) of the reference temperature of 18.3 "C (65 OF). The pressure drop across the coil was in general about 200 kPa, and thus the reported enthalpy differences, which were the actual measured values, differ somewhat from isobaric enthalpy differences relative to a constant reference temperature. The measured enthalpies were compared to the accepted standard for water, Keenan et al. (1969), "Steam Tables", to obtain the errors reported in the last two columns. The standard enthalpies were calculated by interpolating the "Steam Tables" using the measured inlet and outlet temperature and pressure. Thus, the two enthalpy differences, experimental and standard, apply for the same inlet and outlet conditions. Figure 3 shows the error between the

Ind. Eng. Chem. Process Des. Dev., Vol. 23, No. 2, 1984 269

Table I. Enthalpy Measurements for Water" temp, "C ( O F ) inlet outlet 91.1 (195.9) 91.4 (196.6) 95.4 (203.8) 100.0 (212.0) 117.1 (242.7) 117.2 (243.0) 133.0 (271.4) 135.3 (275.5) 136.9 (278.5) 139.7 (283.5) 140.0 (284.0) 141.4 (286.6) 150.2 (302.3) 152.1 (305.8) 153.1 (307.6) 153.3 (307.9) 167.9 (334.2) 167.7 (333.9) 208.4 (407.1) 208.7 (407.7) 223.9 (435.0) 227.4 (441.3) 234.2 (453.6) 234.4 (453.9) 252.4 (486.3) 252.5 (486.5) 254.1 (489.3) 256.7 (494.4) 256.9 (494.4) 257.2 (495.0) 265.3 (509.6) 283.7 (542.7) 288.1 (550.5)

18.9 (66.1) 18.9 (s6.oj 18.6 (65.5) 18.4 (65.2) 18.8 (65.9) 18.6 (65.5) 18.6 (65.4) 18.5 (65.3) 18.4 (65.1) 18.4 (65.2) 18.4 (65.1) 18.5 (65.3) 18.4 (65.1) 18.7 (65.6) 18.4 (65.1) 18.4 (65.1) 18.4 (65.2) 18.4 (65.2) 18.6 (65.4) 18.6 (65.4) 18.2 (64.8) 18.3 (64.9) 18.6 (65.4) 18.6 (65.4) 18.0 (64.4) 18.0 (64.4) 18.1 (64.5) 18.5 (65.3) 18.6 (65.4) 18.6 (65.4) 18.4 (65.2) 18.6 (65.5) 18.6 (65.5)

press., Wa (psia) inlet

outlet

enthalpy diff, kJ/kg (Btu/lb)

1244.0 (180.4) 1237.0 (179.4 j 1259.0 (182.6) 1275.0 (184.9) 1351.0 (195.9) 1369.0 (198.6) 4131.0 (599.1) 4131.0 (599.1) 4148.0 (601.6) 4173.0 (605.3) 4133.0 (599.5) 4137.0 (600.0) 1271.0 (184.4) 1249.0 (181.2) 7494.0 (1086.9) 7489.0 (1086.2) 3802.0 (551.5) 3727.0 (540.5) 3782.0 (548.6) 3738.0 (542.1) 8525.0 (1236.5) 8483.0 (1230.3) 10429.0 (1512.6) 10441.0 (1514.4) 7529.0 (1092.0) 7528.0 (1091.9) 7521.0 (1090.9) 10547.0 (1529.7) 10515.0 (1525.0) 10532.0 (1527.5) 7210.0 (1045.7) 10541.0 (1528.9) 10525.0 (1526.5)

1156.0 (167.6) 1069.0 (155.0 j 1137.0 (164.9) 1109.0 (160.9) 1193.0 (173.0) 1193.0 (173.0) 3922.0 (568.8) 3910.0 (567.1) 3936.0 (570.8) S940.0 (571.5) 3932.0 (570.3) 3910.0 (567.1) 1161.0 (168.4) 1155.0 (167.5) 7249.0 (1051.4) 7248.0 (1051.2) 3600.0 (522.2) 3596.0 (521.6) 3638.0 (527.6) 3638.0 (527.7) 8353.0 (1211.5) 8310.0 (1205.3) 10300.0 (1494.0) 10307.0 (1494.9) 7357.0 (1067.0) 7356.0 (1066.9) 7349.0 (1065.9) 10423.0 (1511.7 ) 10390.0 (1507.0) 10408.0 (1509.5) 7043.0 (1021.5) 10438.0 (1513.9) 10421.0 (1511.5)

302.8 (130.2) 304.0 (130.7 j 321.5 (138.2) 340.1 (146.2) 412.9 (177.5) 414.5 (178.2) 480.1 (206.4) 491.5 (211.3) 499.9 (214.9) 509.9 (219.2) 511.7 (220.0) 515.7 (221.7) 554.5 (238.4) 564.3 (242.6) 567.5 (244.0) 566.8 (243.7) 630.1 (270.9) 632.0 (271.7) 811.1 (348.7) 813.6 (349.8) 879.5 (378.1) 890.9 (383.0) 928.1 (399.0) 923.7 (397.1) 1013.4 (435.7) 1016.5 (437.0) 1026.7 (441.4) 1035.3 (445.1) 1033.0 (444.1) 1035.5 (445.2) 1076.5 (462.8) 1169.5 (502.8) 1187.7 (510.6)

error in A H , kJ/kg (Btu/lb) +0.9 ( + 0 . 4 ) +0.5 (+0.2j -0.2 (-0.1) -1.6 (-0.7) +0.9 (+0.4) +0.7 (+0.3) -0.5 (-0.2) +1.2 (+0.5) +2.1 ( + 0 . 9 ) 1 0 . 5 (+0.2) +0.9 ( + 0 . 4 ) -0.9 (-0.4) 0.0 (0.0) +1.9 ( + O B ) +1.4 ( + 0 . 6 ) 0.0 (0.0) -1.2 (-0.5) +1.6 ( + 0 . 7 ) +0.7 (+0.3) +1.9 ( + O B ) -0.2 (-0.1) -4.4 (-1.9) 14.2 (+1.8) -0.9 (-0.4) -1.4 (-0.6) +0.7 ( + 0 . 3 ) +3.5 (+1.5) +4.9 (+2.1) +1.6 ( + Q . 7 ) e2.6 (+l.l) 0.0 (0.0) +3.5 ( + 1 . 5 ) -0.7 (-0.3)

%

+0.3 +0.1 -0.1 -0.5 +0.2 +0.2 -0.1 + 0.2 +0.4 +0.1 +0.2 -0.2 0 .o +0.3 +0.3 0 .o -0.2 +0.3 +0.1 +0.2 -0.0 -0.5 +0.5 -0.1 -0.1 + 0.1 + 0.3 +0.5 +0.2 +0.3 0 .o +0.3 -0.1

" Average absolute error, kJ/kg (Btu/lb,) = 1.44 (0.62);average absolute error (%) = 0.20; maximum error, kJ/kg (Btu/ lb,) = +4.9 (+2.1); maximum error (%) = -0.49. experimental and standard enthalpies as a function of the experimental enthalpy difference. For purposes of comparison the water enthalpy measurements reported by Lenoir et al. (1970b) for the evaluation of their Freon 11 reference calorimeter are also shown in figure 3. If the enthalpy data of the "Steam Tables" can be considered as an absolute standard, the results of the 33 measurements reported here demonstrate a calorimeter accuracy of f0.5% of the measured enthalpy value in the ranges of 300 to 1190 kJ/kg (130 to 511 Btu/lb,), 91 to 288 "C (196 to 551 OF), and 1230 to 10540 kPa (179 to 1529 psia). These operating conditions encompass most of the measurements on coal-derived liquids. The accuracy of the calorimeter (*0.5% of the measured AH) compares very favorably with errors reported by other research groups for Freon 11 reference calorimeters (Lenoir et al., 1970a,b; Thinh et al., 1973; McCracken and Smith, 1956). The reliability of a reference fluid calorimeter depends upon the reliability of the heat of vaporization of the reference fluid, in this case Freon 11. In the present study a heat of vaporization at 18.3 OC of 184.70 kJ/kg was obtained from the thermophysical properties data of Benning and McHarness (1939, 1940a,b,c). Due to the very large heat of vaporization of water it was not possible to operate the calorimeter with a steam or steam water mixture at the inlet. Thus, to determine if any operational difficulties would be encountered with a vapor or vapor + liquid condition at the calorimeter inlet, a series of runs on n-heptane were conducted in the vapor, two-phase, and liquid regions along an isobar. The nheptane sample used was pure grade, purchased from Phillips Petroleum Co. A typical lot analysis is (in w t %): n-heptane, 99.8, dimethylcyclopentane, 0.2, and trace

+

p"

ENTHALPY OF n-HEPTANE PRESSURE 1060 KPll

-

2W 185

50

100

I50

200

250

3W

350

TEMPERATURE, 'C

Figure 4. Enthalpy for n-heptane as a function of temperature at 1060 kPa.

quantities of 3-ethylpentane and methylcyclohexane. The results are presented in Table II and Figure 4. The experimental enthalpy differences were corrected to the reference temperature of 18.3 "C (65 O F ) using the heat capacity of heptane at 65 "F of 2.1 kJ/kg K. This correction never exceeded 0.5 kJ/kg. The pressure drop across the callorimeter was generally less than 140 kPa and using the thermodynamic property charts of Starling (1973)the pressure corrections needed to obtain an isobaric enthalpy difference at 1060 kPa were in all cases less than 0.2 kJ/kg and corrections were not made. Figure 4 presents the corrected enthalpy difference relative to a basis of 18.3 OC at 1060 kPa (154 psia) as a function of temperature. Also presented in the figure are the results of Thinh et al. (1974). Their data were relative to a 25 "C

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Ind. Eng. Chem. Process Des. Dev., Vol. 23, No. 2, 1984

Table 11. n-Heptane Enthalpy Data temp, "C (OF) run no. l a

2a 4a 3a 10 9 16 15 11 12 13 14 6 5 8 7 18 17 20 19 a

press., kPa (psia)

inlet 93.9 (201.0) 94.2 (201.5) 177.7 (351.9) 178.3 (353.0) 181.6 (358.8) 182.1 (359.8) 204.4 (399.9) 204.5 (400.1) 204.8 (400.6) 204.9 (400.8) 205.4 (401.7) 205.5 (401.9) 227.7 (441.8) 228.3 (443.0) 258.0 (496.4) 258.2 (496.7) 306.5 (583.7) 307.4 (585.3) 337.8 (640.0) 338.2 (640.7)

inlet 1034.0 (150) 1034.0 (150) 1034.0 (150) 1034.0 (150) 1087.0 (155) 1062.0 (154) 1055.0 (153) 1055.0 (153) 1069.0 (155) 1069.0 (155) 1069.0 (155) 1076.0 (156) 1041.0 (151) 1034.0 (150) 1048.0 (152) 1062.0 (154) 1069.0 (155) 1062.0 (154) 1062.0 (154) 1062.0 (154)

outlet 827.0 (120) 827.0 (120) 827.0 (120) 827.0 (120) 1000.0 (145) 979.0 (142) 958.0 (139) 958.0 (139) 993.0 (144) 993.0 (144) 993.0 (144) 993.0 (144) 958.0 (139) 965.0 (140) 965.0 (140) 965.0 (140) 958.0 (139) 958.0 (139) 951.0 (138) 951.0 (138)

A H (exptl) (65 "F ref),

kJ/kg (BtNIb,,) _.. 174.2 (74.9) 175.6 (75.5) 409.4 (176.0) 413.3 (177.7) 422.9 (181.8) 423.6 (182.1) 698.0 (300.1) 704.8 (303.0) 533.8 (229.5) 541.0 (232.6) 592.0 (254.5) 582.7 (250.5) 762.7 (327.9) 770.6 (331.3) 851.5 (366.1) 844.8 (363.2 j 993.7 (427.2) 1001.3 (430.5) 1082.8 (465.5) 1096.0 (471.2)

Approximate outlet pressure.

Table 111. Estimated Accuracy of Measurement measured quantity inlet calorimeter temperature Freon-11 mass in receiver coal liquid mass in receiver outlet calorimeter temperature pressure measurement Freon 11 valve switching error hydrocarbon valve switching Freon latent heat pressure correction error estimated measure men t uncertainty

uncertainty , kJ/kg 0.5 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 1.3

basis and for a pressure of 1030 kPa. Their results were adjusted to a basis of 18.3 "C using the tabulation of Starling (1973), however, no pressure adjustment from 1030 kPa was made. From the figure, the heat of vaporization was estimated as 214 kJ/kg at 1060 kPa and 205 "C. The heat of vaporization reported by Thinh et al. (1974) was 214 kJ/kg at 1030 kPa and 205 "C. The vapor pressure estimated from this experiment was 1060 kPa at 205 "C as compared to a value of 1055 kPa at 205 "C from Stull (1947). From these results it was concluded that reliable data across the two-phase region could be obtained. In addition, Table I11 estimates the sources of error caused by various measurement uncertainties with an overall predicted uncertainty of 13 kJ/kg. In reporting future data for coal derived liquids and model compounds a reference state of the liquid at 18.3 "C (65 O F ) , the approximate boiling point temperature of Freon 11 in Golden CO, and 1 atm was selected. Thus, it is necessary to first adjust the enthalpy values for slight variations in the outlet temperature by using a heat capacity obtained from the slope of a plot of the data at low temperatures. It is anticipated that this correction will always be less than *l.O kJ/kg, and since the correction is based on experimental data, a negligible uncertainty will be introduced. The reported experimental enthalpy values will include this correction. In referencing the data to 1 atm it is necessary to estimate the effect of pressure on the liquid from the outlet pressure to 1.0 atm at 18.3 "C. To make this adjustment the Kelser-Lee (1976) correlation was selected since it is the most recent for petroleum fractions. Although the correlation has not been tested for coal derived liquids, since the effect of pressure on

liquid enthalpy is small, the correction should in all cases, even at the highest pressures, be less than 5% of the measured enthalpy. Thus, even significant percent errors in the correlation would have only a minimal effect on the accuracy of reported enthalpy values. Both sets of enthalpy values, with and without the pressure correction, are to be reported, as well as the magnitude of the pressure correction. Conclusions A reference fluid boil-off calorimeter has been developed which is capable of measuring the enthalpy of coal-derived liquids from 18.3 to 400 "C (65 "F to 750 O F ) and from 700 to 10300 kPa (100 psia to 1500 psia). The water and n-heptane evaluation runs demonstrate that under normal operating conditions there is no significant heat leak into or out of the calorimeter and that a conservative estimate of the error in the enthalpy measurements is f l % of the measured A H value. Naturally, some data points will exhibit errors greater than 1% due to unobserved equipment malfunctions or operator reading errors. The calorimeter continues to be used to measure the enthalpy of coal-derived liquid samples and model compounds representative of coal-derived liquids. Acknowledgments The authors wish to thank the Office of Fossil Energy, Department of Energy for support of this work (Contract No. E(49-18)-2035). The authors wish to thank H. Omid, J. R. Andrew, and R. Sharma for experimental assistance. Registry No. Water, 7732-18-5; heptane, 142-82-5.

Literature Cited Andrew, J. R. M.S. Dissertation, Colorado School of Mines, Golden, CO. 1978. Benning, A. F.; McHarness. R. C. Ind. Eng. Chem. 1039, 37,912. Benning, A. F.; McHarness, R. C. Ind. Eng. Chem. 1040a, 32, 497. Benning, A. F.; McHarness, R. C. Ind. Eng. Chem. 1040b, 32, 698. Bennlng, A. F.; Mcbrness, R. C. Ind. Eng. Chem. 1 0 4 0 ~3 2 , 814. Keenan. J. H.; Keyes. F. G.; Hill, P. G.: Moore, J. G. "Steam Tables"; Wiley: New York, 1969. Kesler, M. G.; Lee, 6. I.Hydrocarbon Process. 1076, 55(3) 153. Lenoir, J. M.; Robinson, D. R.; Hipkin. H. 0. J. Chem. Eng. Data 107Oa, 15, 23. Lenoir, J. M.; Robinson, D. R.; Hipkin, H. G., material deposited with the American Society for Information Services, c/o CCM Information Services, Inc., 22 West 34th St.. New York. NY 10001,Document NAPS-00625, 1970b. McConnell, J. R. M.S. Dissertation, Colorado School of Mines, Goiden. CO, 1976. McCracken. P. G.; Smith, J. M. AIChE J . 1056, 2,498

Ind. Eng. Chem. Process Des. Dev. 1984, 23, 271-273

271

Thinh, T. P.; Ramalho, R. S.; Kaliagulne, S.Can. J . Chem. Eng. 1973, 51, 86. Thinh, T. P.; Ramalho, R. S.; Kaliaguine, S. J . Chem. Eng. Data 1974, 19, 193.

Nelson, J. M.; Holcomb, D. E. Chem. Eng. Rog. Symp. Ser. 1958, 49(7), 93. Ng, H. J.; Mather, A. E. American Institute of Chemical Engineers 71st Annual Meeting, Miami Beach, FL, Nov 1978; American InstlMe of Chemical Engineers, New York, 1978. Starling, K. E. "Fluid Thermodynamic Properties for Light Petroleum System"; Gulf Publishing Company: Houston, 1973 p 97. Stull, D. R. Ind. Eng. Chem. 1947, 39, 517.

Receiued for review February 2, 1982 Accepted June 28, 1983

Enthalpy Measurements of a Syncrude and a Distillate Derived from Western Kentucky Coal Hosseln Omld, James R. Andrew, Vlctor F. Yesavage;

and Arthur J. Kldnay

Department of Chemical and Petroleum Refining Engineering, Colorado School of Mines, Golden, Colorado 8040 1

Enthalpy data at pressures of 690, 3450, 6895, and 10340 kPa (100, 500, 1000, 1500 psia) for temperatures between 18.3 and 375 OC (65 to 705 OF) are presented for a Western Kentucky syncrude produced by the Char-011-Energy-Development (COED) process, and for a combined distillate of the Western Kentucky syncrude for pressures of 690, 3450, and 6895 kPa (60, 100, 500 psia) and temperatures between 18.3 and 402 OC (65 to 765 OF). The data were obtained in a Freon 11 (CFCI,) reference fluid boll-off calorimeter.

Introduction Coal-derived liquids are a new and vital class of industrial compounds, but they have thermodynamic properties that are largely unknown and, presently, unpredictable. Enthalpy measurements are needed to make more efficient design calculations of equipment using these new liquids. Experimental results are presented here for a syncrude and a distillate derived from a Western Kentucky coal by the COED process. The data were obtained in the Freon 11 (CFCl,) reference fluid boil-off calorimeter described previously that was developed for measurements with coal-derived liquids (McConnell et al., 1984). Based on previous evaluation of the calorimeter using both water and n-heptane as test fluids, the estimated error in the enthalpy measurements should be less than *LO% of the measured value. Experimental Section The boil-off calorimeter system, operation, and calibration is described in detail elsewhere (McConnell et al., 1984; McConnell, 1976; Andrew, 1978). A major experimental concern during operation of the calorimeter with coal-derived liquids is the occurrence of sample decomposition at high temperatures. To determine the significance of this decomposition on the enthalpy measurements, low-temperature runs were repeated after hightemperature runs were obtained. In general, the lowtemperature runs obtained before and after heating up the sample were in agreement. At times, however, the runs differed indicating decomposition. This decomposition generally occurred together with system pressure buildup from coking or a change in appearance of the sample. When decomposition occurred, the sample was replaced. As a check on the continued reliability of the system, enthalpy measurements on n-heptane were generally repeated whenever the sample was replaced. The n-heptane data always agreed with previous measurements to within kl.O%. Experimental details are reported elsewhere (Omid, 1977). 0196-4305/84/1123-0271$01.50/0

Table I. Physical Properties and Elemental Analyses

molecular weight, wt av (no. av) bromine no., g/100g ASTM D1159 refractive index, specific gravity

Western Kentucky whole oil

Western Kentucky distillate

180 (145) 7.3

130 (120) 7.9

1.5186 0.923

1.4997 0.884

4.35

2.11

(60"/60")

kinematic viscosity (100 OF), cSt, ASTM D 445 "API K Watson elemental analysis C

21.8 10.9 87.40

H

11.06

N

0.52

28.5 10.7 88.04 (88.79)a 10.98 (10.75 ) 0.92 (.74)

___

S 0.04 Data in parentheses are duplicate analyses performed a t Texas A&M.

Each of the coal-derived liquids studied was analyzed in detail and the analytical results are presented in Tables 1-111. The properties measured include specific gravity, molecular weight, bromine number, refractive index, kinematic viscosity, and asphaltene content. In addition to property measurements, the coal-derived liquids were subjected to an elemental analysis, a distillation, and a compositional analysis by use of a gas chromatographicmass spectrometer combination. The GC-MS analysis was done by Dr. C. V. Philip of Texas A & M University with a Hewlett-Packard 5710A gas chromatograph, a 5980 mass spectrometer, a 5947A multiion detector, and a 5933A data system and is presented in Table S1 presented as Supplementary Material. 0

1984 American Chemical Society