BIOCONVERSION OF HEAVY CRUDE OILS: A BASIS FOR NEW TECHNOLOGY

E. T. Premuzic, M. S. Lin, and H. Lian

Department of Applied Science Biosystems and Process Sciences Division

Brookhaven National Laboratory Upton, NY 11973

To be Presented at U.S. DOE'S 1995 International Conference on Microbial Enhanced Oil Recovery and

Biotechnology for Solving Environmental Problems Dallas, Texas

September 11-14,1995

This research was performed under the auspices of the U.S. Department of Energy under Contract No. DE-AC02-76CH00016.

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Bioconversion of Heavy Crude Oils: A Basis for New Technology

E.T. Premuzic, M.S. Lin, and H. Lian Biosystems and Process Sciences Division,

Department of Applied Science, Brookhaven National Laboratory,

Upton, New York 11973.

Abstract

Systematic studies of chemical mechanisms by which selected microorganisms react with crude oils have led to the identification of biochemical markers characteristic of the interactions of microbes with oils. These biomarkers belong to several groups of natural products ranging from saturate and polyaromatic hydrocarbons containing heterocyclics to organometallic compounds. The biochemical conversions of oils can be monitored by these chemical markers, which are particularly usefbl in the optimization of biochemical processing, cost efficiency, and engineering studies. Recent results from these studies will be discussed in terms of biochemical technology for the processing of crude oils.

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thcreof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recorn- mendation, or favoring by the United States Government or any agency thereof. The Views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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Introduction

Biochemical reactions which occur during the interaction of select microorganisms and crude oils follow distinct trends which can be monitored by means of unique chemical markers”. The chemical markers used represent several groups of compounds ranging fiom those containing sulfhr and nitrogen to organometallic compounds, saturates, aromatics, resins, and asphaltenes each representing certain chemical properties of oils which are affected by the action of microorganisms. To a certain extent, these markers resemble a group of compounds, known as “biomarkers” used in petroleum exploration, source rock and reservoir correlations, as well as maturation and degradation studies3. The versatility and applicability of chemical markers has been discussed in detail elsewhere in this volume (see 2). For the purposes of this discussion, it suffices to say that bioconversion of crude oils results in a 20% to 45% reduction in suhr content, a 15% to 45% reduction in nitrogen content, and a 16% to 99% reduction in the concentration of trace metals such as vanadium, nickel, arsenic, and others. Further, current data indicate that the biochemical action occurs in the heavy fiactions of crude oils such as resins and asphaltenes and favors formation of lighter fiactions. The chemical markers serve as diagnostic tools by which several aspects of the biochemical conversion can be monitored. These include the nature and the extent of bioconversion of the crude by microorganisms, properties essential in the cost-efficiency analyses of any processes based on microbial interactions with crude oils. This paper will briefly discuss the use of a chemical marker in the development of a heavy crude oil upgrading process.

Materials and Experimental

Chemical and biochemical methods have been discussed elsewhere lV4 and will not be dealt with here. Assuming a ten year life span of the plant, there are three major steps to consider in cost analysis. To obtain the total capital investment is the first step6. The detailed cost estimation for each unit is derived fiom graphs and formulas using published data6*’. The second step is to calculate manufacturing cost. This step combines the ECI and Ulrich methods6**. The third step is to calculate the net present value and pay back period which relates to the interest rates, Le. the cost of borrowed money. For this purpose, the procedure described in Chapter 8 of reference 6 has been used.

Results and Discussion

This discussion will deal with the results obtained by using a biochemical process for the upgrading of low grade oil, as shown in Figure 1. In this process, a fifty- five gallon bioreactor has been used. There are two major parts to this process. The first part is a biochemical batch process in which the oil and the biocatalysts are mixed by concurrent pumping through a mixer to make a water-in-oil

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emulsion. The process is set to run in a batch mode and a thirty-six hour, fifiy cycle pass. The second part deals with the processing of waste products. In this particular example, the aqueous phase is separated fiom oil by sedimentation centrifige although other de-emulsification processes can be used. The aqueous phase is then hrther treated using several available technologies, such as co- precipitation and/or absorption of metals and by-products. In this experimental process, a single chemical marker, i.e. total concentration of sulfur has been used in the economic and technical analysis of the process. For the analysis, a heavy crude, 3% sulfir oil, has been used as the material.' In this particular case, as shown in Figure 2, regardless of the amount of sulfir removed, e.g. from 33% to 45%, the annual net profit increases with the decrease in the reaction time. The analysis described in Figure 3 shows that the annual net profit increases as a hnction of an increase in the level of sulfir removal fiom the oil at different reaction times. The combined data given in the two figures clearly indicate that in order to maximize the annual net profit, it is necessary to shorten the reaction time and simultaneously remove maximum amount of sulfir fiom the oil. Using this approach, a cost-efficiency analysis has been canied out yielding results which can be applied directly to the design and optimization of biochemical processes using a single chemical marker such as sulfur. Figure 4 shows the cash flow profiles for the oil upgrading process which assumes a ten year life span for a plant that can remove 33% of sulfbr from oil within 48 hours of reaction time. In this case, there is no profit regardless of interest rates which may be charged by financial houses for borrowed capital finds. With a decrease in reaction time to 42 hours and an increase in the extent of sulfbr removal to 36%, a profit can be obtained. However, the invested capital represents in-house funds and does not involve any moneys fiom outside financial groups, a scenario represented by Figure 5. In this case the pay back period is 7.4 years with a net present value of $0.6 million, assuming that the plant will operate for ten years to reach its anticipated life time. On the other hand (see Figure 6), if the reaction time can be reduced to 36 hours and at the same time the sulhr removal fiom the oil increased to 40%, then the pay back period can be reduced to 2.7 years. In this case, the net present value after operating for 10 years becomes $3.6 million, without borrowing any moneys fiom financial houses (Figure 6). Using such cost analyses enables us to define laboratory engineering experimental protocols which allow to identify the optimization parameters needed to reduce the reaction times and at the Same time reach the maximum s u l k removal efficiency. Concurrent with this strategy, fbrther cost-efficiency fine tuning can be accomplished by tailoring the use of the end product such as utilities, refining, and others. This can be accomplished by modifjing process variables to account for nitrogen and trace metals removal. In all cases, such R&D strategies use chemical markers in the development and application of new upstream and downstream oil processing operations.

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Conclusions

Ultimate success of any applicable process depends on its technical feasibility and its cost-efficiency. Use of chemical markers to evaluate the bioconversion of crude oils by microorganisms allows to monitor major variables characteristic of microbial action on crude oils. These include changes resulting in:

1. the composition of organic sulfur compounds;

2. the composition of nitrogen compounds;

3. the composition of organometallic compounds;

4. distribution of hydrocarbons.

In addition, the use of chemical markers allows to predict the cost-efficiency of a process and simultaneously guides the R&D effort in process optimization.

Acknowledgments

This work is supported by the U.S. Department of Energy, Division of Fossil Fuels, under Contract No. AS-219-ECD, and Contract No. DE-ACO2- 76CH00016 with the U.S. Department of Energy. We wish to express our gratitude to Ernie Zuech of the U.S. DOE, Bartlesville office for the supply of OSC oils and the Synfbels Research Corporation and the Santa Fe Energy Resources, Inc. of Houston for the supply of MWS oil. We also wish to acknowledge Yao Lin of Brookhaven National Laboratory for the graphic materials.

References

1. Premuzic, E.T., Lin, M.S., Racaniello, L., and Manowitz, B.: Microbial Enhancement of Oil Recovery--Recent Advances, Proceedings of the International Conference on Microbial Enhanced Oil Recovery, Elsevier Science Publishers, Amsterdam (1993) 37-54.

2. Premuzic, E.T., Lin, M.S., Lian, H., Zhou, W.M., and Yablon, J.: “Microbial Interactions in Crude Oils: Possible Impact of Biochemical Versatility on the Choice of Microbial Candidates,” presented at the 1995 International Conference on Microbid Enhanced Oil Recovery and Biotechnology for Solving Environmental Problems, Dallas, September 1 1-14, 1995.

3. Peters, K.E. and Moldowan, J.M.: The Biomarker Guide, Prentice Hall (1993) 363.

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4. PremuZic, E.T., Lin, M.S., and Manowitz, B.: “The Significance of Chemical Markers in the Bioprocessing of Fuels,” Fuel Processing Technology, 40 (1 994), 227-239.

5. Premuzic, E.T., Lin, M.S., and Tin, J.Z.: “Recent Developments in Geothermal Waste Treatment Biotechnology,” Metals in the Environment, Vol. 1, Eds. R.J. Alan and J.O. Nriagu, CPS Consultants, Edinburg (1993) 356-363.

6. Ulrich, G.D.: A Guide to Chemical Engineering Process Design and Economics, John Wiley and Sons, New York (1994) Chs. 5,6, and 8.

7. Perry, J.H. and Chilton, C.H.: Chemical Engineers’ Handbook, 6th Edition, McGraw-Hill, New York (1993).

8. Dounias, G.A. and Stavropoulos, K.D.: “Economic Feasibility of Biochemical Upgrading of Heavy Crudes,” (1 995) Final Report.

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Preclpltant' 0.1 kglh

(9)

Aq. Phase 6.8 kglh

Biocatalysts Mixture (B.M.) Oil Phase 62.5 kglbatch 9.0 kglh

4 Precipitation

(7) ( 8 ) Drum 26 gal

198 kalh Sedimentation I

I. Biochemical batch process. (36 hour pass)

11 3.3 kglh Initial B-1 TWO (5)

Pump 1 Phase System

Batch

55 gal Pump 2 Bioreactor

(1°'1 Centrifuge

Thickener 26 gal

1 I I

Option (non-regulated) Sludge 6.1 kglh 0.8 kglh 55 gal

2. Product and waste processing plant. (9.2 hour)

* Based on the experience of biochemical processing of geothermal brines.@)

Figure 1. Biochemical process for upgrading of low grade oil (Batch per pws, 55 grl bioreactor, 1 set)

4 1 Reaction time (hr)

-33% s +36% S

Figure 2. The annual net pmfit at various reaction times in oil upgrading process with different sulfur removal kvels (l,OOO,OOO gal batch per pass)

+ Q) t

40 45 50 66 75

-1 J- Sulfur removal (%)

Figure 3. The annual net p d i t for various sulfur content removal in oil upgrading process at different =action times (l,OOO,OOO gal batch per pass)

-0.5

-1 .o

-1.5

-2.0

-2.5

I NPV: Net present value 1 PBP: Pay back period -3.0

Figure 4. Cash flow profiles for oil upgrading (48 hr batch, 33% S duction)

0.8

0.6

0.4

0.2

0.0

-0.2

-0.4

-0.6

-0.8

-1 .o -4.2

-1.4

NPV: Net present value PBP: Pay back period NPV = 0.6M

NPV = -0.2M

NPV = -0.4M

I Time (yr)

Figure 5. Cash flow profiles for oil upgrading (42 hr batch, 36% S reduction)

c c

4.0

3.5

3.0 3 G 2.5

0 2.0

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0

c v) m

B 1.0 E I

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-1.5

NPV: Net present value PBP: Pay back period DBEP: Discounted break even peflod

I DBEP

PBP 4--- 2.7 yr

4 7 ' 8 9 10 I 1 12 13

Figure 6. Cash flow profiles for oil upgrading (36 hr batch, 400/. S reduction)