PILOT PLANT PROGRAM FOR UPGRADING HEAVY OILS BY HYDROPYROLYSIS

Transcription

1 Chapter 123 PILOT PLANT PROGRAM FOR UPGRADING HEAVY OILS BY HYDROPYROLYSIS Kent E. Hatfield* and Alex Oblad** The primary separation technique for the production of synthetic fuels from such sources as oil shale, tar sand, and black oils, produces a hydrocarbon liquid that is similar in properties to the heavier fractions of crude oil or heavy crudes. Extensive processing of these materials is required to bring them to a stage suitable for further processing in a normal oil refinery. This general problem seems to hold true for both in-situ as well as mined materials. Coal-derived liquids generally must undergo an even more drastic upgrading prior to reforming into transportation fuels. Most work for production of synthetic crude oil carried out by the government or in private industry has concentrated on the technology for primary hydrocarbon production or extraction. These process schemes have added to their flow sheets, existing oil refinery hydroheating, or coking steps to improve the properties of the intermediate oil and otherwise produce an acceptable synthetic crude oil product from the process. In many cases this adaptation of existing oil refinery technology to the synfuel process has been less than ideal, and penalties have or will occur in the overall process economics. Two examples are typical of this problem. In the recovery of Canadian tar sands, a crude bitumen is produced from the tar sand ore and is then upgraded to a synthetic crude oil using a more or less conventional oil refinery coking step. The coke produced, which is currently being "stockpiled," is essentially a waste product. Coking is a common oil refinery process that is being considered for several synthetic crude oil processes. The data in table are from actual test runs, using a delayed coking process with various heavy oil materials. The examples typify synthetic crude intermediate materials. If a process alternate to coking were available that produced considerably high yields, a significant improvement would be made in synfuel economics as well as in the production of up to 20 percent more crude from a given raw material input. Table Results of some delayed coking test runs Yield from Thermal California Coking Tar Residue Gas (Cj, Oil Coke C 2 ) 18.1% 30.0% 59.9% 12.0% 66.4% 21.6% Mid-Continent Residue 6.5% 73.5% 21.1% 100.0% 100.0% 100.0% Another example encompasses the catalytic hydrogenation of heavy synfuel intermediate oil, which, in one form or another, is being considered for many projects. A major problem with the intermediate oil produced from most primary extraction processes is the presence of particulate matter in the oil. This matter is present either as coal-ash residue in the case of coal-derived liquids, spent shale in the case of shale oil, or clay or fine sand in the case of "black" oils and tar sand bitumens. Particle sizes are usually less than ten microns and are difficult and usually costly to remove by conventional settling, centrifugation, filtration, or such means as solvent extraction. Removal of these particulates is essential in some step prior to the point at which the materials are ready for refining. An excellent review of this general problem is given by Hossein et al. (1980) with an analysis of several possible solutions to the problem all with less than ideal results. A significant improvement could be made in synfuel technology if a non-catalytic hydrogenation process could be developed that would handle a dirty oil, produce little or no coke, and not be subject to the above problems. Using funds provided by the U.S. Department of Energy, the Fuels Engineering Department at the University of Utah, under the direction of Alex G. Oblad, Joseph Shabti, and James W. Bunger, developed an improved, non-catalytic, non-coke forming synthetic crude oil and heavy oil upgrading process, using a novel and innovative thermal hydropyrolysis technique. The process consists * Executive Vice President, Enercor ** Distinguished Professor of Fuels Engineering, University of Utah 1175

2 HEAVY CRUDE AND TAR SANDS of subjecting a heavy oil to a hydrogen atmosphere at psig and F in a tube-type reactor and with short residence times. The initial results with pure compounds were very encouraging. Later, a variety of very heavy oils was used as feedstock and each was converted into a free-flowing material resembling crude oil. It is of major importance that little or no material resembling coke was found in the reactor or liquid recovery vessels. Subsequent improvements were made to the laboratory equipment and technique in order to improve the oil and hydrogen reactor feeding technique, the unused hydrogen recycle rate, the reactor tube design, etc., all of which are critical to the success of the process, and have resulted in reproducible results for several typical feedstocks. As expected, different feedstocks require slightly different process conditions and result in different product characteristics. However, only a narrow range of process variables for feedstocks of high paraffin, aromatic, aliphatic, and mixed content have been studied. This encourages the application of this technique to heavy oils from different sources, including heavy, coal-derived liquids. The amount of hydrogen utilized in the process is important to the overall process economics. During the thermal hydrogenation reactions, some light hydrocarbon gases (methane, ethane) are formed. These materials can be used to produce the process hydrogen requirements using conventional steam reforming. Results also indicate that the first hydrogen introduced into the cracked oil molecule does the most good, with diminishing returns thereafter. Excellent results occur when about 1000 ft 3 of hydrogen per barrel of feed is utilized. If this hydrogen consumption is allowed to reach 2000 ft 3 /barrel, much less oil improvement takes place per unit of added hydrogen and more gas product results. More importantly, the cost of the processing step increases due to the extra hydrogen production costs. Tables and give some typical results of applying this hydropyrolysis step to various synthetic crude oil intermediate materials and heavy oil. The oil produced from these and other laboratory runs is typical of that produced by thermal coking or catalytic hydrogenation, but without the disadvantages of large yield losses to coke formation or a high catalyst cost from temporary or permanent fouling. Enercor is interested in utilizing the hydropyrolysis technology for the upgrading of bitumen recovered from tar sands and would like to offer the process through a University of Utah license to other interested users. Negotiations are currently underway between Enercor and the University of Utah to this end. In order to demonstrate the technology on a continuous basis and develop commercial plant design data, Enercor is planning to construct a pilot plant at its research facility in Salt Lake City. A preliminary design of a 50 barrels per day continuous hydropyrolysis pilot plant has been completed, using as a basis the experimental work and apparatus developed at the University of Utah. The basic reactor for this process consists of a multitube furnace-type unit. The pilot plant will use a reactor consisting of a single commercial-size tube. This represents a scale-up of approximately 50 to 1 for the pilot plant over the university laboratory model. Consequently, no scale-up will be required in the commercial process. The simplified process flow sheet in figure describes in graphic format the proposed flow scheme. The process consists of one or two critical elements forming the main part of a commercial scheme and some routine steps included to make the pilot plant function as simply as possible. The main piece of equipment in the process flow sheet is the hydropyrolysis reactor, which consists of a rather Table Hydropyrolysis of synthetic oil intermediates Feed Heavy Tar A Heavy Tar B Heavy Tar C API gravity Av molecular wt Boiling range % over 530 C % over 530 C % over 530 C Reactor Conditions Temperature Pressure Hydrogen consumption 525 C C 1800 psig C 1800 psig 600 Product API gravity Av molecular wt Boiling range Liquid yield Gas yield (C lt C 2 ) % above % above 530 C % above 530 C

3 PILOT PLANT PROGRAM FOR UPGRADING HEAVY OILS BY HYDROPYROLYSIS Table Hydropyrolysis results of heavy oils Feed Cold Lake- Lloydminster Synth oil Asphalt Ridge Bitumen Altamont Crude San Ardo Heavy Oil Type B.P. Range Heavy black oil Aromatic 45% over 550 C Naphthenic 63% over 500 C Paraffinic 10%over410 C Mixed with 14.5% Asphaltenes 57% over 538 C Reactor Conditions Temperature Pressure 520 C 525 C 1055 psig 525 C 550 C 1000 psig 525 C Product B.P. Range Liquid yield (%) Gas make (%) Light amber oil High Low 7%over410 C %over450 C % over 100 C 90% over 200 C % over 538 C and 3% asphaltenes standard oil refinery-fired heater. The feed oil enters this unit after passing through feed-effluent heat exchange and the radiant section of the furnace. The oil is raised to a temperature somewhat below the reaction temperature. Fresh and recycle hydrogen enter the unit after passing through the furnace radiant section. The hydrogen is heated to a temperature above the reaction temperature and the hydrogen and oil are brought together at the top of a downflow, single pass, reactor tube located in the convection section of the furnace. A special hydrogen-oil mixer is used. The reactants are held at a near constant temperature and for a short residence time in the reactor. The reaction products flow out of the bottom of the tubes to a temperature quench column. The reaction is estimated to be slightly exothermic. Oil feed pumps and hydrogen compressors have the capability of supplying 2000 psig at the furnace. Figure Pilot unit of the heavy oil hydropyrolysis process 1177

4 In the quench tower system, a small heavy-oil slipstream is removed from the bulk of the main product stream, flashed and removed. This oil would contain the bulk of the foreign matter in the oil feed and is a small fraction of the total product (less than 3 percent for most oils). The main oil product stream flows through a series of cooling heat exchangers to condense the product oil from the gases made in the reactor and the unused hydrogen. The oil flows to product storage. The gas is separated from the recycle hydrogen and burned. (In commercial Table Pilot plant major hydropyrolysis equipment lis 1. Furnace Reactor 300,000 btu/hr Alloy tubes-2000 psig 650 C 2. Hydrogen Make-up Compressor 6 Ib/hr AP = 2000 PSI Diaphram Carbon Steel 3. Hydrogen Recycle Compressor 150 Ib/hr AP = 400 PSI Diaphram Carbon Steel 4. Refrigeration Unit 1,000 btu/hr Freon Unit-100 F 5. Storage Tanks (two required) 5 ft diameter x 10 ft high Carbon Steel 6. Furnace Outlet Separator 8 in diameter x st with demister screen Stainless Steel 7. Product Scrub Tower (two required) 8 in diameter x 6 ft. Carbon Steel 600 C 200 psig 8. Product Cooler Knock-Out 8 in diameter x 3 ft. Carbon Steel 50 C 2000 psig 9. Low Temperature Knock-Out 8 in diameter x 3 ft. Alloy Steel 75 C 2000 psig 10. Vent Knock-Out 8 in diameter x 3 st Alloy Steel 75 C 2000 psig 11. Furnace Product to Feed Heat Ex Shell and Tube 2000 psig 450 C 10 ft Product Gas Water Cooler 50 ft psig Tube Side 150 C 13 Feed Preheater 20 ft 2 50 psig 450 C Shell and Tube 14. Furnace Liquid Product Cooler 10 ft 2 Alloy Tubes 450 C 2000 psig Tubes Shell and Tube 15. Bitumen Feed Pump 1.6 GPM 2000 psig Piston Type Carbon Steel HEAVY CRUDE AND TAR SANDS 1178 operation, this gas could be steam-reformed to make feed hydrogen.) In commercial operation, a turbine expander-compressor may be the best method for separating recycle hydrogen from gas. For convenience, a refrigeration unit is used in the pilot plant. Product oil is stored for later evaluation and study. Feed hydrogen is purchased. The cost of designing the pilot plant, procuring equipment, and constructing the plant at the Salt Lake City site is estimated to be $2,500,000. Table describes the individual equipment items required for this pilot plant. The pilot plant operation would have as its goals: 1. The demonstration of the process on a continuous basis as a totally integrated unit. 2. The evaluation of recycle gas composition and any impurity buildup, coke formation, corrosion, or other factors not found to be present in the experimental laboratory work. 3. The establishment of operating temperature, pressure, and residence time, conditions vs product results. 4. The establishment of commercial design parameters and expected full-scale investment and operating cost figures. 5. The preparation of fully descriptive reports for synfuel industry review. A twelve-month program is envisioned for the pilot plant operation of four three-month phases. Phase One. During a shakedown period, a small-size reactor tube would be used to test, modify, if necessary, and otherwise condition the process for continuous, reliable around-the-clock operation. One or two runs of 100 hours each would be made to establish the unit's integrity. Phase Two. Using a regular-size commercial reactor tube, a detailed program would be carried out to test various synthetic intermediate crude oils under a matrix of temperature, pressure, reactor residence time, and hydrogen consumption and recycle gas composition conditions. An evaluation between feed and product quality improvement would be made at these various conditions. If available, feedstocks evaluated would include: heavy oil, black oils, tar sand bitumen, oil shale liquids, SRC II liquids, Lurgi tars, coal pyrolysis liquids, and other heavy residues. Phase Three. A series of 100- to 200-hour runs at the conditions established above as optimum would be made. Data would be collected as well as product accumulated and stored for full later oil refinery evaluation. This

5 PILOT PLANT PROGRAM FOR UPGRADING HEAVY OILS BY HYDROPYROLYSIS longer operation would be made with as many and as much of the above feedstocks as would be available. Phase Four. Synthesis of data, preparation of final reports and conceptual designs of commercial operations would be made. Investment and operating cost data for typical synfuel plant applications would be made. The cost for this program of pilot plant operation is estimated at $3 million as outlined in table Total program cost, construction, and operation has been budgeted at $5.5 million for which funding sources are currently being pursued. Table Pilot plant operating costs Operating labor and associ iated overhead Operating supervision and associated overhead Pilot plant maintenance and facilities revamp (if necessary) Utilities Oil feed stock Hydrogen Analytical support Miscellaneous supplies Subtotal Report preparation and d< ssign studies Total cost of pilot plant o pe ration $1,060, , , , , , , ,000 $2,730, ,000 $3,000,000 Reference Hossein, Magill and Rubin, 1980, Upgrading coal products can affect the environment: Hydrocarbon Processing, October, p

6 THE FUTURE OF HEAVY CRUDE AND TAR SANDS Second International Conference Sponsored by THE UNITED NATIONS INSTITUTE FOR TRAINING AND RESEARCH and PETROLEOS DE VENEZUELA S.A. in cooperation with THE UNITED STATES DEPARTMENT OF ENERGY and ALBERTA OIL SANDS TECHNOLOGY AND RESEARCH AUTHORITY 7-17 February 1982 Caracas, Venezuela Joseph Barnea Scientific Secretary R.F. MEYER, J.C. WYNN, and J.C. OLSON Editors

7 THE FUTURE OF HEAVY CRUDE AND TAR SANDS THE SECOND INTERNATIONAL CONFERENCE Copyright 1984 by Unitar. All Rights Reserved. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. ISBN m COAL AGE MINING INFORMATION SERVICES McGraw-Hill, Inc Avenue of the Americas, New York, N.Y