Pergamon

ORIGINAL CONTRIBUTION

Waste Management, Vol. 14, Nos. 3-4, pp. 231-235, 1994 Copyright © 1994 Elsevier Science Ltd Printed in the USA. All rights reserved

0956-053X/94 $6.00 + .00

THE E N G I N E E R I N G ASPECTS OF A USED OIL R E C Y C L I N G PROJECT

Charles Harrison Texaco, Inc., P.O. Box 430, Room 944 East, Bellaire, Texas 77402-0430, U.S.A.

ABSTRACT. In an era of environmental awareness recycling projects have proven almost irresistible to both the private and public sectors. The benefits of more recycling operations are obvious to us: less waste, less pollution and a more prudent utilization of our precious natural resources. However, in the rush to recycle newspaper, aluminum, steel, glass, plastics, solvents or hydrocarbons, many projects have floundered due to dismal economics ineffective technol- ogy, or legal constraints. In order to avoid the pitfalls associated with many recycling efforts the operators must be en- sured of both positive economics and reliable technology. This paper presents an overview of the engineering of Texaco's used oil recycling operation which recycles an environmentally unfriendly waste to a valuable product while achieving positive economics.

I N T R O D U C T I O N

In an era of environmental awareness recycling pro- jects have proven almost irresistible to both the pri- vate and public sectors. The benefits of more recycling operations are obvious to us: less waste, less pollution and a more prudent utilization of our precious natural resources. However, in the rush to recycle newspaper, aluminum, steel, glass, plastics, solvents or hydrocarbons, many projects have floundered due to dismal economics ineffective technology, or legal constraints.

In order to avoid the pitfalls associated with many recycling efforts the operators must be en- sured of both positive economics and reliable tech- nology. This paper presents an overview of the engineering of Texaco's used oil recycling opera- tion which recycles an environmentally unfriendly waste to a valuable product while achieving posi- tive economics.

we all live, the ability to profit from recycling useable materials, and legal concerns. Texaco's motivation for this project encompasses all three factors. It has been stated that one gallon of used oil pollutes one million gallons of drinking water and the impact improper disposal of used oil has on the environment is well known. Texaco, as a mar- keter of lubricating oils, wishes to share the respon- sibility of seeing that these oils are disposed of properly. In the absence of legislative incentive to recycle (which is the situation at the moment), it is very difficult to justify a project that is not eco- nomically profitable. Reprocessing is at a very low level in the U.S. with few companies active today. Most used oil collected is burned in industrial heat- ers, kilns and at electric power generation plants which are continuously being more regulated. This project will be profitable, meet present regulations, and assure that Texaco is well situated to address future legislation on this subject.

S U C C E S S F U L R E C Y C L I N G

There are several motivating factors which can con- tribute to a successful recycling project. These fac- tors include concern for the environment in which

231

P R O C E S S DESIGN C ONSIDE R AT IONS

Before any serious process design can be under- taken, several items must be quantified. These in- clude such things as what is the charge stock, what

232

is availability of the charge stock, what products and by-products will be manufactured, and what re- cycled product specifications do customers demand. Also, what process will be used to make the prod- ucts and where will the plant be located.

Regarding feed characteristics, one thing certain about used oil is quality is variable. Unlike most refinery processes, where feed quality is reasonably consistent, used oil is an unknown that is a function of what materials are dumped into it. Many of these materials can be contaminants. It is very much a function of the collection system, geo- graphic location, and degree to which sampling and testing are monitored.

Many different components (fluids and solids) can contaminate used oil. Examples of common contaminates are gasoline and diesel from internal combustion engines, vegetable oils, synthetic motor oils, asphaltenes, glycols, water, chlorinated sol- vents, dirt, soot, wear metals, crude oil, spent and unspent additives, tank bottoms, and hazardous ma- terials such as polychlorobiphenols (PCB's, from electrical transformer oils).

Figure 1 is an abbreviated list of typical charge stock properties. One method of mitigating the in- herent variability of used oil is to homogenize it in larger lots in tankage. The value of this on opera- tions must be weighed against segregated tankage and inventory cost.

Products to be manufactured must be determined early in a project to target customers and evaluate economics. This phase has an impact on process selection. Two primary options were considered. Recycle used oil to virgin quality base oil or target the distillate fuel market.

~.3o (MAX]

SPECIFICATIONS USED MOTOR OILS

PROPERTY TYPICAL APi GRAVITY 25-30 SSU @ 100F 40-140

C. H A R R I S O N

SPECIFICATIONS R E P R O C E S S E D OIL & MDO

DMDO PROPERTY ISO-8217 DMB

API GRAVITY 25 (MIN) SSU @ 100F tO0 (MAX) WATER, % I

SULFUR, % 2.0 (MAX)

ASH, %

POUR, F 32 (MAX) FLASH, F 140 (MIN)

FIGURE 2.Reprocessed oil and MDO specifications.

Considering many factors including fuel oil prices, base oil prices, base oil avails, processing costs and marketing logistics along with internal factors, Texaco chose to target the high sulfur distil- late fuel market. More specifically, the marine die- sel oil market became the primary focus. Marine Diesel Oil (MDO) is a fuel used to power medium speed diesel engines commonly found aboard inter- national cargo vessels. Figure 2 illustrates typical specification for marine diesel oil as described by DMDO, ISO-8217 DMB. These are the specifica- tions that a marketer can expect their customers to demand.

PROCESS SELECTION

Process selection is the next step to a project reali- zation. The block flow diagram in Figure 3 illus- trates the basics of used oil processing. The basic

~ U S E D OIL PROCESSING STEPS

HYDROFINISHED LIGHT RECYCLED HYDROGEN GASOIL

rVATER, % 2 - 1 C

SULFUR, % 0.15-0.35

% S H , % O . 2 - 1 .!

POUR, F 10-20 FLASH, F 100 25% COST 75%

FIGURE l.Used motor oil specifications. FIGURE 3. Used oil processing steps.

USED OIL R E C Y C L I N G

SPECIFICATIONS REPROCESSED OIL & MDO

REPROCESSED DM ~DO PROPERTY USED OIL USED OIL ISO-8217 DMB

API GRAVITY 25-30 28-32 25 (MIN) SSU @ 100F 40-140 100 100 (MAX) WATER, % | -10 0.30 (NIA) 0 (MA] SULFUR, % 0.15-O.35 0.2 2.0 (MAX) ASH, % I 0.01 (MA 1.2-1.5 0.01 0.01 (MA POUR, F 10-20 (-5)-5 32 (MAX) FLASH, F 100 200+ 140 (MIN)

FIGURE 4. Reprocessed oil and MDO specifications.

fundamentals of processing to base oil for lube manufacture are removal of heavy metals to allow hydrotreating the lube stocks without poisoning (deactivating) the hydrotreating catalyst. Removal of the heavy metals can be accomplished chemi- cally or physically. Current common practice in the U.S. is physical separation of these ash containing components by distillation methods.

Investment costs can be reduced by eliminating the last two steps and electing to produce distillate fuels. Further investment reduction is possible by eliminating the final three steps and producing a de- watered non-distillate fuel of high ash content which can be marketed to the power generation in- dustry as a blend component for low sulfur (1%) Number 6 Fuel Oil.

After careful consideration of markets, invest- ments and profit potential, Texaco chose the three step route to distillate fuels.

Figure 4 shows the properties of used oil and re- processed used oil Texaco expects to receive and produce. The recycled distillate product is also compared against the specification for marine diesel oil which is intended to be a major target market.

Final process selection was aided by review of existing operations in Canada, the U.S. and Mexico. Familiarization with the Phillips Rerefined Oil Process (PROP) and Thin Film Evaporator (TFE) distillation technology, as practiced by Evergreen and Safety Clean, aided the selection process as did discussions with external contractors and licensors.

Texaco has considerable experience with used oil collection and processing as a result of our ten year operation in Queretaro, Mexico. The review re- sulted in the use of Texaco in-house technology and Texaco's Central Engineering Department to com- plete the process design package for submittal to

233

contractors to bid on fabrication and erection of the plant. Previous experience in the used oil operation was of significant benefit.

LOCATION OF A FACILITY

Another factor which would have a significant in- fluence on the final design and cost of the project is geographical location. Because used oil is not read- ily available in large quantities at a central location, it is likely that economics of size normally available to large plants would be offset by high transporta- tion costs associated with a wide tank truck collec- tion program. However, Texaco elected to take advantage of lower costs/large volume barge trans- portation available on the U.S. inland waterway system by siting this plant on the Mississippi River. Also, Texaco decided to employ existing under-util- ized facilities such as closed or limited operation plants, marketing terminals, or similar facilities with surplus infrastructure such as tanks and build- ings. In the final analysis, the location selected for the first Texaco used oil recycling plant was at the Star Enterprise Marketing Terminal in Marrero, Louisiana, near New Orleans. This is Texaco's old- est sales terminal dating to the early 1900s. The re- cycling plant capacity will be 3500 BPD of used oil charge.

A terminal site presents several engineering chal- lenges for a project of this nature in addition to pre- viously mentioned considerations, such as feed variation and contamination.

The design must take into consideration the ex- tremes of feed variability. For example, water con- tent can vary from 2-10% and fuel dilution can vary over a wide range and processing of all combina- tions must be possible.

No flare exists at the terminal. Land space is limited and the terminal is in a relatively populated area inside the city limits of Marrero, Louisiana. These restrictions preclude the building of a con- ventional flare.

No process cooling water is available at the site. Some other utilities are limited as well. No steam or pipeline nitrogen is available. The result is heavy reliance on air cooling. City water and natu- ral gas are available.

Waste water treatment facilities are not available. In addition, waste water from used oil is difficult to treat making the installation of a comprehensive

234

TEXACO FUELS AND MARINE MARKETING USED LUBRICANT RECYCLING FACILITY, MARRERO, LA

SIMPLIFIED FLOW DIAGRAM TO ATMOSPHERE

TO A13~10SpHIE[1 F"

I WATE. ~, ,~,'D.OC^..O= I I I ~ - . q 1 I

FEED ~(CHANGIE VACUUM VACUUM DISTILLA'nES

. . . . . . . . . j , . . . . . . .

I I h . . . . . . ' :F . . . . . .

aL wA'nER B LOWDOWN

FIGURE 5. Simplified flow diagram of Texaco Fuels and Marine Marketing Used Lubricant Recycling Facility, Marrero, Louisiana.

system prohibitive. Solution of this problem re- quired innovation.

Finally, one of the major advantages of locating in an existing facility is to make use of existing tankage, pipelines and other infrastructure. Some- times these existing facilities are not exactly what is needed and must be modified for use. An example would be fixed roof vs. floating roof tanks. An- other example was the need for a heated tank for as- phalt flux storage.

ADDITIONAL CHALLENGES

Used oil recycling presents challenges which are unrelated to location. Used oil by its nature is cor- rosive at certain operating conditions. Used oil contains organic and naphthenic acids. Some of these occur naturally and some are formed as prod- ucts of combustion in automobile engines. Some corrosive materials such as halogens or mineral ac- ids may be introduced into the used oil from outside sources. Experience with processing used oil over 10 years in Mexico has shown that equipment fail-

TFAMM PLANT DATA

• CHARGE 3500 BPD OR (APPROX) 44 MM GPY (OPERATING 300 DAYS/YEAR)

• YI ELDS

• 5-10% WATER

• 5-10% LIGHT EN DS • 67-78% MEDIUM/HEAVY DISTILLATE

• 12-15% V A C U U M BOTTOMS

• 15-20 EMPLOYEES

• LESS 1/2 ACRE FOR PROCESS UNITS • LESS 2 ACRES FOR TOTAL PLANT

C. HARRISON

~ PRIgDICTED P R O D U C T PROPERTIES MA RIN E D IE SE L OIL

PROPERTY MDO

API GRAVITY 28.0

VISCOSITy, SSU @ 100 F 100

WATER, VOL % 0 SULFUR, WT % 0.2 ASH, WI'% 0.or

POUR POINT, o F 5 FLASH, F 200+

MOLECULAR WEIGHT 3 5 0

TB B F 5 % 5 5 0 5 0 % 7 5 0 9 S % 9 2 5

FIGURE 7. Predicted product properties marine diesel oil.

ures are often the result of rapid and catastrophic corrosion as well as gradual metal corrosion or ero- sion losses.

The Marrero installation required the use of some non-carbon steel metallurgy such as 316L stainless steel and 347 stainless steel. If the deci- sion had been made to recycle to base oil, additional metallurgy such as Inconel 625 likely would have been required.

The final factor influencing the design package was the decision on design standards and philoso-

P R O C E S S P R O D U C T S USED OIL INITIATIVE

PRODUCT YIELD % DISPOSITION

LUBE DISTILLATE 67-78% MARINE FUEL & CUTTER

ROAD AND ROOFING ASPHALT FLUX 12-15%

ASPHALT

LIGHT ENDS 5-10% PLANT FUEL

WATER 5-10% INCINERATED

INSOLUBLE GASES TRACE INCINERATED

FIGURE 8. Process products: Used oil initiative.

~.~ TEXACO USED O)L RECYCLING FACILITY MARRERO, LOUISIANA

FIGURE 6. TFAMM Plant data. FIGURE 9. Texaco's Used Oil Recycling Facility, Marrero, Louisiana.

USED OIL RECYCLING 235

phy. For this project the decision was made to ac- cept normal industry standards except where safety was an issue. Texaco design practices governed safety issues. In addition, the design philosophy adopted was to be willing to accept a shutdown to make repairs in the event of an equipment failure rather than spare all normally spared equipment.

As a result of the above, ANSI pumps were specified for non-critical service, pumps and com- pressors were not spared, lower TEMA ratings on heat exchangers were acceptable, and shorter than normal plant life was specified.

FINAL DESIGN RESULTS

The final design results are shown in Figure 5, which is a simplified process flow diagram. Used oil feed is exchanged with product prior to entering an atmospheric flash tower. This tower is control- led to remove all water present in the used oil feed. Since the tower is a simple one-stage flash tower, the overhead stream will also contain some low boiling hydrocarbons. This stream is fed to the heater to burn the organic portion for energy recov- ery. Supplemental heat is provided by natural gas to provide the required process duty. Water in the form of steam leaves the heater stack with the other stack gases. Caustic scrubbing removes the acid gases (SOx, COx, NOx, HCL, etc.) from the stack gases which are vented to the atmosphere.

The dry feed goes to a conventional vacuum dis- tillation tower which produces three product

streams: l.) light ends consisting of gasoline/kero- sene/diesel boiling range material, 2.) vacuum dis-

tillates (vacuum gas oil) and 3.) a residual bottom

stream. The distillate streams are cooled by ex- change with incoming feed and air fans in route to tankage. The bottoms are cooled by a water box cooler.

The vacuum distillates and some portion of the

light ends are blended to make marine diesel oil for sale and the bottoms will be sold into the asphalt market.

Because no flare exists, emergency relief for

both the atmospheric and vacuum fractionators is routed to a water quench tower. Relief materials

are collected and recycled to the process after the

emergency has abated. This allows their recovery under normal operating conditions.

Figure 6 illustrates expectations for the opera-

tion. The yield values are shown as ranges due to the variability of used oil. Figure 7 shows the prop- erties expected for Marine Diesel Oil and Figure 8

shows Texaco's proposed disposition of the prod- ucts. The status of the project is ongoing. Texaco

has approved the project and Petrocon was the suc- cessful bidder. Equipment fabrication and procure-

ment is essentially complete and erection is in

progress. Start-up is planned for the second quarter of 1994.

Figure 9 gives an artists conception of how the

plant will appear when it is completed and opera-

tional. It can be seen from this figure that the plant is compact and does not occupy a large land area.