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  • Depannvnt of CHEMICAL ENGINEERING

    Documen C ntr

    NORTH CAROLINA AGRICULTURAL AND TECHNICAL STATE UNIVERSITY

    GREENSBORO 2741 1

    TELEPHONE (9101 334-7564 FAX (9101 334-7904

    1 Center U.S. D e p m e n t of Energy Pittsburgh Energy Technology Center

    Pittsburgh, PA 15236-0940 P.O.BOX 10940, MS 921-118

    FEFI 2 5 m Q t

    SUBJECT Quarterly Technical Report for U.S. DOE Grant No.: DE-FG22-92MT92020

    Dear Sir,

    Three copies of the quarterly technical progress report for the period April 1,1996 to June 30, 1996 for the above grant are enclosed. If you have any concerns about the repop, please feel free to contact me.

    Sincerely,

    Vinayak N. Kabadi Grant PI

    cc: Dr. Psalmonds, Division of Research, NCA&TSU

    An Equal Opponuniry [Affirmative Action Employer

    A Conm'ruenr Instirution of THE UNIVERSITY OF NORTH CAROLINA

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    QUARTERLY TECHNICAL REPORT April 1,1996 to lune 30,1996

    Project Title

    Improvement of Hydrogen Solubility and Entrainment in Hydrocracker Feedstocks U.S. DOE Grant No.: DE-FG22-92MT92020

    Investigator

    Vinayak N. Kabadi, Department of Chemical Engineering, North Carolina A&T State University, Greensboro, NC 2741 1

    Project Objectives and Scope:

    The objective of this project is to determine the conditions for the hydrogen-heavy oil feed preparation so as to optimize the yield of hydrocracking reactions. Proper contacting of hy- drogen with heavy oil on the catalytic bed is necessary to improve the yields of the hydro- cracking reactions. It is most desirable to have the necessary amount of hydrogen available either in the dissolved or in entrained state, so that hydrogen diffusion to the reaction site does not provide rate controlling resistance to the ovpall rates of hydrocracking reactions. This projecr proposes to measure solubility and entrainment data for hydrogen in heavy oils at conditions such as in hydrocrackers, and investigate the improvement of these properties by usage of appropriate additives. Specifically, measurements will be carried out at temperatures up to 300 "C and pressures up to 120 atmospheres. Correlations for solubility and entrainment kinetics will be developed from the measured data, and a method for estimating yield of hy- drocracking reactions using these conelations will be suggested. Exxon Research and Engi- neering Company will serve as private sector collaborator providing A&T with test samples and some technical expertise that will assure successful completion of the project.

    Technical Highlights and Milestones:

    The final experimental measurements or hydrogen solubility in hydrocarbons are in progress. The nevel experimental apparatus has been successfully operated for these measurements. The apparatus wil l be utilized for many more measurements of solubility of gases in liquids in the future. The calibration procedures and some of the initial data measurements are summa- rized in the attached write-up.

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    An experimental method for measuring the solubility of hydrogen gas in liquid

    Hexadewne is being developed utilizing a Gas Chromatograph outfitted with both Flame

    Ionization Detector (FlD) and Thermal Conductivity Detector (TCD) for detection, laboratory PC

    with Waters Dynamic Solutions Baseline 810 chromatography software for analysis, and an

    equilibrium cell of in-house design with associated piping. The basic principle of operation of the

    apparatus involves the sparging of hydrogen gas through tiquid hexadecane at different

    pressures and temperatures as specified by the experimental parameters and withdrawing both

    liquid and vapor phase samples to be analyzed with the gas chromatograph. As this experiment

    involves equilibrium compositions, care must be taken to ensure a condition of equilibrium exists

    before experimental data may be obtained. The chemicals involved in the experiment shall all be

    of HPLC grade or higher or of the highest grade possible for all liquids and the gases shall be of

    Ultra Pure Carrier grade.

    PRELIMINARY STUDIES

    Prior to obtaining any experimental data, development of a suitable method is required.

    The method is the plan order of operations necessary to perform the actual experiment and

    analyze the data. The experimental operation was developed by Kabadi and involves charging

    the equilibrium cell with approximately 75 milliliters of Hexadecane, sealing it to ensure a

    leakproof seal, and sparging hydrogen gas through it. The hydrogen gas shall be supplied by

    cylinder via piping network inclusive of a digital flow meter. The gas shall be introduced to the

    cell through four inlet ports at the poles of the base of the cell at the specified pressure and

    flowrate. Exit of the gas product shalt be through a single exhaust port at the top of the cell which

    terminates inside the laboratory exhaust hood. Cell pressure shall be maintained by a control

    valve in the exit gas stream line. Sample extraction shalt be performed utilizing two sample

    valves, a three port sampling vafve and a six port routing valve. The carrier gas stream (argon)

    shall flow continuously to the Gas Chromatograph (GC) through the six port routing valve. The

    sample, vapor or liquid, shall be selected by the three port valve and directed io the six port

    valve where it is combined with the carrier gas for routing to the GC.

  • Purging of the entire sampling loop is effected with the six port valve also. When sample

    analysis is not required, the contents of the sample loop is routed to a vent in order to assure an

    uncontaminated sample for the subsequent analysis. The size of the sample is determined

    through the selection of the appropriate external sample loop and shall be the same for both the

    liquid and vapor samples. The entire equilibrium cell and sampling and routing valves shall be

    maintained at the desired operating temperature through the use of a laboratory oven in which

    they shall be placed. The exit line to the GC shall be maintained at the desired temperature with

    the use of an electrical heating tape.

    Due to the expected change in volume due to the vaporization of the liquid hexadecane

    in the liquid sample, and the fact that the external sample loop shall be utilized for both the vapor

    and liquid samples, it is probable that differing volumes of the sample will be required depending

    on the phase of the sample. Consequently, determining the appropriate sample size for actual

    injection is of extreme importance. The GC measures total amounts of components which pass

    through it. In general, detectability can be accurate in the range from 1 - 1000 ppm. Relatively small amounts of compounds may be analyzed with very good results. However, if excessive

    amounts of compunds are introduced, the results show marked deterioration of indicator peaks

    and consequently degrade the accuracy of the analysis. Because of this, division of the sample

    entering to the GC from the six port valve must be performed as necessary to produce good,

    accurde, and reproducable results. Spliting this stream is achieved through the use of the PSS

    (Programable Split Splitless) injector on the GC. By instituting a split flow configuration, a

    fraction of the total incoming sample may be routed to the GC and the remainder vented out.

    The primary concern is the determination of the appropriate split ratio. As the total incoming

    sample size is determined by the size of the external sample loop, the split ratio will be

    dependant upon that volume and the maximum allowable sample volume for which the GC

    produces satisfactory results.

    The initial step in determing the split ratio was to determine the maximum sample size which

    may be injected to the GC. This was done by doing manual injections of differing amounts to the

    GC and obtaining the corresponding chromatographs. Two FID sensitivity settings are available

    the GC which allow for differing amounts of components to be introduced. Only one sensativity

    setting exists for the TCD. Injections were made using both FlD sensitivity settings. The FID shall

    be used to detect hexadecane amounts while the TCD shall detect hydrogen amounts. Injections

    of pure components were made and the corresponding chromatograph analyzed visually for

    satisfactory peak definition. The desired camer gas flowrate was specified to approximately 10

    milliliters per minute and the detector temperature was set to 300 degrees Celsius. The first set

    of injections were made at FID sensitivity of 20 as we expected a large amount of liquid sample

  • to be analyzed since the split ratio was unknown. The choice of external sample loops for the

    apparatus was previously limited to either a five microliter or two microliter loop.

    Beginning with a 5 microliter injection, available sample loops are 5 and 2 microlitersie

    loop volumes ( 5 and 2 microliters ) chromatograph 1 was produced. Good peak definition was

    demonstrated but an additional smaller peak was noted a s well as a prominent tail. Possible

    explanations for these phenomena included an incorrect oven ramp rate and an elongated

    elution time due to the amount of the sample. A second injection was made at the same

    conditions but incorporated a sample split of 99.4390617% a s

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