Effluent control a t a large oil H
Robert T. Denbo and Fred W. Gowdy Humble Oil & Refining Co. Baton Rouge, La. 70821
DM
I I
retinery More efficient use of water highlights the results of a
five-year abatement program at Humble’s huge Baton Rouge refinery
umble’s 450,000-barrel( bbl) / day capacity Baton Rouge refinery is the largest in the U.S. and is considered one of the most complex in the world. The refinery manufactures a complete line of petroleum products including motor gasolines, aviation fuels, diesel and other distillate fuels, and lubricants and greases. A number of petrochemical units are located within the refinery proper. Since the refinery came on-stream in 1909, waste water quality considerations have continually changed as more industry was installed and the population south of Baton Rouge increased. In this area, groundwater has high salinity and is not suitable for domestic use. Consequently, approximately 1.5 million people in South Louisiana depend on the Mississippi River as their source of drinking water. Louisiana has set stream standards to protect drinking water
quality, and at the request of the state, the Environmental Protection Agency Water Programs Office has conducted taste and odor control studies of Mississippi River water since late 1968. Planning to improve waste water from the refinery has been carried out in conjunction with both state and federal agencies. The complexity of sewer and waste water systems of older refineries adds significantly to the effort and costs associated with high-quality waste water. During the five-year period ending in mid 1971, approximately 72 man-years of professional planning effort were expended to develop the current waste water improvement program at the Baton Rouge refinery (below). Projects completed or under construction amount to over $22 million in investment cost-and the program is still not completed. There is no question that the percent of to-
Waste Water improvement Program at Humble’s Baton Rouge Refinery Phase
I
Purpose
Planning effort [man years)
Status as of Aug. 1 1971 % cor;lptet;
6
100
30
Completion
Project cost
1968
N o t applicable
85
1st quarter 1972
$19,000,000
6
80
Lagoon to be expanded
1,000,000
13
20
4th quarter 1972
1,500,000
To provide faster follow-up on eff I ue nt problems
3
20
Mid 1972
Removal of suspended oil a n d solids
To provide pretreatment t o
2
20
Probable 1974
Not available
VI I
Additional treatment facilities
To remove dissolved organics for meeting long-range effluent quality goals
6
40
Schedule not developed
Not available
Vlll
Rainfall detention
To detain a n d treat rainfall prio?
6
20
Schedule not developed
N o t available
Waste water characterization
Problem definition
II
River water replacement
To reduce waste water volume by 90% a n d oil discharge by 80%
111
Taste and odor reductior
To reduce taste and odor
IV
In-plant waste load reduction
To abate pollution a t t h e source
V
Monitoring and surveillance improvements
VI
prevent upsets i n additional treatment facilities
t o discharge
Total 1098 Environmental Science & Technology
200,000
72
$22,000,000 plus
feature Huge. Humble's Baton Rouge refinery, operating since 1909, is the largest US. refinery and one of the most complex in the world
Waste water characterization The characteristics and volumes of approximately 325 specific waste water streams were determined. This information was necessary to develop methods to reduce pollutants at the source and treatment techniques for pollutants not removed. Details were presented at the 43rd Water Pollution Control Federation meeting in Boston, Mass. River water replacement tal investment devoted to waste water control to achieve a given level of waste water quality is significantly higher for ,a ,large exieting refinery than it would be for a new refinery. Similar approaches are being employed at the Baton Rouge refinery to control air emissions and solid waste disposal. Overall, approximately 9 0 man-years have been spent in environmental quality planning at the refinery during the past five years. In recent years, substantial improvements have been made in the quality of waste water from the refinery. During the 10-year period ending 196869, abatement efforts were directed primarily at reducing the amount of oil and phenol in waste water discharges. Marked reductions in those parameters amount to a 75% reduction in oil and 85% in phenol. Since 1968-69, efforts have been directed at reducing total organics in the effluent with emphasis on taste and odor reduction. Intensified planning efforts in water pollution abatement were started in 1965. Overall, the approach in the Baton Rouge refinery program has stressed increasing reuse and eliminating pollution at the source. The most important step in this program has been a $19 million project to eliminate once-through use of river water for cooling by installing a recirculating system employing cooling towers. This project not only will reduce oil discharges to the river by 80% below the 1 9 6 8 4 9 level, hut will cut waste water volume by 9'0%.
As of the summer of 1971, this project was 60% complete. Nevertheless, substantial improvements in waste water quality were achieved from this and other projects. Improvements were greater than predicted (below) resulting from excellent cooperation of personnel at the various refinery units. Early start In 1965, facilities for treating refinery waste water consisted of inplant facilities such as: * sour water stripping a Phenex unit for removing phenol by solvent extraction * a ballast water treating tank and effluent treatment including a silt deoiling unit and seven pairs of modernized oil-water gravity separators, followed by a holding basin providing 21/*-hr detention time for final oil removal. A segregated system for ponding effluent from the phenol treating plant for detention and biological oxidation was in operation also. Approximately 55% of process cooling river water i s utilized on a once-through basis. The remainder of water cooling employed recirculating systems with cooling towers. Since this once-through water amounted to approximately 170 million gal/day (gpd) (90% of the waste water flow), treatment beyond primary was impractical. In 1965, a comprehensive program for waste water improvement was undertaken at the Baton Rouge refinery. Eight phases were delineated (see previous page).
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By the mid 1960's, significant progress had been made toward the refinery's goal of eliminating oil losses to the Mississippi River. However, 80% of the remaining oil was associated with use of large quantities of once-through river water for process cooling, The incoming river water contained approximately 325 yd3/day of silt. Fine silt particles formed oil-siltwater emulsions of about the same density as water and were not removed satisfactorily by gravity separation, These emulsions were responsible for most of the remaining oil discharged in the waste water from the refinery. It was decided to replace once-through river water with recirculated cooling water systems. Consequently, a $19 million project was developed. to replace Once through river water by installing nine
Refinery Waste Water Improvement Since 1968-69 %reductions in absolute quantities from the 196869levels Actual Best
Predicted
July week
Oil
71
62
Phenol
42 30
68 72
20 20 50-70
59 65
BOOi
coo TOC
Odorcontribution
60
81 68
80
EO 80 70
Volume 5. Number 11, November 1971 1099
Steam generator eliminates need for larger
cooling towers, varying in size from 4500 to 46,000 gal/min (gpm). Reducing volume from 135,000 gpm to 14,000 would also permit additional treatment to remove dissolved organics. Although a number of heat efficiency projects were found to be economically attractive, the total project has no economic return. Water circulation in the system amounted to 135,000 gpm in 18 units throughout the refinery. Initial process design efforts were complicated by lack of adequate information on the 18-unit river water piping systems, and up-to-date drawings had to be prepared. Process design information on all cooling equipment in the river water service was also obtained, and heat removal requirements and water rates for all coolers and condensers using river water had to he completely redefined. A highlight of this phase included selecting a makeup water source which is required to replace evaporation losses. In addition, water must
1100 Environmental Science & Technology
LKGO coolers
be continually withdrawn from the system, “blown down” to avoid excessive buildup of dissolved materials. Three sources of cooling tower makeup water were considered: * additional groundwater batture wells (water present in shallow sands near the river bank) and clarified river water. It was necessary to select the highest cost source of the three considered-larified river water. Investment and operating wsts for clarifying river water, makeup water distribution system, and cooling towers were compared for operation at 1.5, 2 , and 4 cycles of concentration. Cycles of concentration refers to the buildup in concentration of dissolved solids via evaporation where the initial dissolved solids content is 1. Therefore, 2 cycles of concentration refers to doubling the initial concentration of dissolved solids. Operation of cooling towers at 4 cycles of concentration sets the clarification plant size, giving minimum investment and minimum operating costs.
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Sufficient capacity is included in the clarification plant to supply anticipated increases in water requirements for new projects through 1975. The clarification plant includes two completely independent 10,000-gpm trains for removing silt and partially softening raw river water. Each train is capable of supplying 100% of the water needs for the project. If necessary, a third train can be added to supply additional clarified water for refinery use. In the early stages of process design, several outside clarification plants were visited. As a result, care was taken to avoid a numher of potential problems. Storing and feeding chemicals in liquid form eliminate maintenance problems associated with dry chemical feeders. Also, sludge pits and sludge pumps were eliminated by discharging sludge by gravity. Two 40,000-bbl clarified river-water tanks provide 4-hr holdup at design pumping nates. A diesel engine driver, selected for the spare clarified river-water pump, .also provides emergency fire water in the event of a total electrical and steam failure at the refinery. The heat removal requirements for all coolers and condensers in the system were redefined, and a number of projects were identified to reduce cooling-water requirements, Additionally, many problem areas involving cooling water were spotlighted. A few examples that improved efficiency of existing operations include:
Recirculated cooling water passes through two clean barometric condensers
.The light coker gas oil (LKGO) coolers were inadequate (upper left), but installation of a 10,000-lb/hr highpressure steam generator yielded an acceptable return on investment and allowed continued use of the existing coolers at a lower water rate. .Before this project, all pipe stillvacuum tower barometric condensers used once-through river water (below left). Cooling in the second-stage barometric condenser was by direct contact with the ,river water. Condensed steam and hydrocarbons formed an emulsion with silty river water which interfered with the gravity separator operation to remove oil. The second-stage ejector was discharged to the atmosphere which presented an air pollution problem. Both of these problems were solved. The direct-contact barometric condenser was eliminated by installing a shell and tube intercondenser utilizing recirculated cooling water. Thus, the hydrocarbon-water-silt emulsion was eliminated. The second-stage ejector discharge, formerly vented to the atmosphere, is now condensed in a new shell and tube aftercondenser. A small amount of gas, still uncondensed at this stage, is burned in a special waste gas burner installed at an existing furnace. Tbis eliminates a potential odor pollution problem associated with venting s t e m ejector gases containing a trace of sulfur compounds to the atmosphere. The extremely small amount of sulfur dioxide formed by combustion caused no atmospheric pollution problem. .The steam condensate produced in the shell and tube equipment is reused as desalter water, thereby saving well water.
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I
In conjunction with a consulting iirm, a computer program was developed to solve cooling water distribution problems in complex piping networks. Results included significant investment savings in piping and pumping equipment when compared to designing by manual calculation. Installing an air-fin cooler on the atmospheric sidestream at one of the large pipe stills released sufficient cooling tower capacity for the heat load of vacuum tower surface condensers. * “Clean” barometric condensers use once-through river water for condensing steam only. This once-through river water is being eliminated by connecting these systems to new recirculated cooling-water systems. On one unit, recirculating cooling water was passed through a second barometric condenser before being returned to the cooling tower (above). * Replacing barometric condensers with surface condensers was impractical on certain units in the lube operations area where entrainment and
carry-over of wax or asphalt would plug shell and tube equipment at woling temperatures. In this situation, once-through water was eliminated by installing a specially designed “oily-water” cooling tower (below) which provided recirculated water to he used at the barometric condensers. The new “oily-water” cooling tower is constructed entirely of ceramics instead of flammable materials. The ceramic tower consists of two separate sections, each designed to handle the total cooling load. Piping is provided for circulating basin water through a direct-contact steam heater to the return water distribution headers. When the accumulation of wax in the tower becomes a problem, one section can he shut down at a time for a high-temperature wash cycle. A skimming pump is provided for transporting skimmings to the emulsion treating tanks. Taste and odor reduction
In 1969, a study was carried out to determine the major contributors to the taste and odor of refinery waste water. Essentially all of the specific waste water streams were reevaluated by the Threshold Odor Number (TON) test. Waste water from the barometric condensers at the crude vacuum distillation units contributed approximately half of the total odor tn refinery waste water. Fortunately, these condensers were being replaced by surface condensers at all crude distillation units as part of the river water replacement project. Odor from these sources was reduced by 95% by using the condensate from the new surface
Oilv water coolina tower eliminates once-through water
Volume 5, Number 11, November 1971 1101
condensers as makeup water for crude desalting operations (odor-causing agents are extracted from the water by the crude). The volume of the existing phenolholding pond was increased and 7-75hp surface aerators were added to accelerate biological oxidization of any phenol that may be accidentally spilled at the lube phenol treating plant, Aeration capacity was included for treating other streams selected for odor reduction. The addition of these streams to the lagoon also provided a biological seed, so that, in the event of a spill, the time required for phenol degradation in the lagoon is reduced. Three aerators were installed in August 1970, four more were added in April 1971, and the installation of three more aerators of 100 hp each is planned by the end of 1971. In-plant waste load reduction
Construction of the river water replacement project was well under way in the summer of 1970. Pilot plant operations to determine treatment plant configuration and design parameters were scheduled (early 1972) to begin after 90% reduction in waste water flow following completion of river water replacement. The in-plant waste load reduction program was developed to coincide with the completion of the river water replacement project. A set of economic guidelines was developed to compare the cost of installing facilities to correct pollution at the source with the cost of treatment facilities. The cost of treatment was based on an activated sludge plant feeding approximately 20 million gpd of waste water complete with sludge disposal. The total savings are the combined effects of overall savings in investment and overall operating costs over equipment life, discounted to present worth. On this basis, saving 1 gpm of waste water reduces cost by $550 and eliminating organic loading reduces cost by $35/lb of BOD^ per day. Actually, these reductions in cost are understated since elimination at the source is totally affective for the organics removed, while treatment is only partially effective. The waste load reduction survey included a detailed inspection of each unit. Total manpower requirement for the inspection phase of this project was eight man-years, and engineering efforts for these projects will amount to another five man-years. One of the largest sources of excess 1102 Environmental Science & Technology
waste water usage throughout the refinery was found to be pump jacket cooling water discharged to the sewer. Water used on the bearing jacket, gland jacket, and pedestal jacket is clean and can be returned to the cooling towers. Also, cooling water could be routed in series through the bearing jackets, gland jackets, and pedestal jackets. Only the water used on the gland or mechanical seal may come in contact with hydrocarbon. A small needle valve to restrict flow will reduce this from up to 15 gpm/pump to an average of 1/4 gpm/pump. Cooling tower water used on pump jackets and for other purposes on the unit which is discharged to the sewer affects cooling tower operations by increasing makeup requirements. Most of the existing towers on well water makeup were operating at 1-1.5 cycles of concentration due to the large quantity of cooling tower water being blown down to the sewer through pump jackets and other equipment. By installing new piping systems to return pump jacket water to the cooling tower, cooling tower blowdown to the sewer from this source will be reduced by 95%. Using this approach, the cycles of concentration on the existing cooling towers, which use well water makeup, will be increased to 2 cycles of concentration or higher (below). Some of the more significant water reduction items include: * T h e 4500 gpm of pump jacket water which is currently discharged to the sewer at units throughout the refinery will be reduced to approximately 200 gpm by installing necessary piping to return this water to the cooling towers. Approximately 600 gpm of steam condensate can be economically recovered and returned to the boiler feed water system. Besides reducing waste water treatment plant investment, it will reduce significantly the size of a future boiler feed water treatment facility. The volume of water used for washing alkylation reactor product can be reduced 150 gpm by installing a system to recycle the wash water and to maintain a controlled blowdown. Plans have been made on a trial basis to reuse cooling tower blowdown (950 gpm) in the fire and utility water system to determine if the hydrocarbon content could present a safety problem. If the operation proves to be
successful, cooling tower blowdown water from other cooling towers will be injected into the system and water saving will be increased. If this system proves workable, analyzers will be evaluated to detect hydrocarbons in the cooling tower blowdown (which would allow switching cooling tower blowdown to the sewer if the water became contaminated). A typical existing desalter system (upper right) on a crude distillation unit employing a quench for hot desalter brine uses approximately a total of 500 gpm of once-through water to cool hot desalter brine by direct contact. The combined brine and cooling water are discharged to the sewer through a condensible blowdown drum. The direct-contact cooling operation will be eliminated by installing shell and tube equipment. The coolant in this equipment will be makeup water for the desalting operation. This, in effect, will provide warmer water contacting crude with a resultant reduction in heat loss in the crude, will save water and reduce emulsion problems with the brine-cooling water discharge, and will provide an attractive economic return based on heat economy. The refinerywide taste and odor study, Phase 111, spotlighted the pipe still barometric condenser water as being the largest taste and odor contributor (about half of the total refinery contribution). Installing surface condensers to replace barometric condensers decreased the volume of odorous water from 4000 to 200 gpm. However, the 200 gpm required some type of treatment for odor improvement. Reusing this odorous steam condensate as desalter water makeup not only reduced water usage but also improved the quality of the waste water discharged. Crude extracts organics from this stream resulting in 95% odor reduction, 90% oil reduction, and 40% COD reduction. No harmful ef-
Pipe Still Cooling Tower Operation Present
Cycles
1.4
Makeup, g p m 700 Evaporation, gprn 200 Wind loss, g p m 13 Blowdown, gprn to sewer 487
1st Step
2nd Step
2.0 440 220
4.0 293 220
14
14
206
59
I Desalter brine exchanger eliminates river water quench
fects have been observed in product streams as a result of this extraction. In-plant effects
The refinery waste water flow after river water replacement is predicted to be 14,000 gpm. The in-plant project is expected to reduce the waste water flow by an additional 50% and make significant reductions in organic pollutants. The incentive for this reduction is significant. The estimated investment for in-plant modification is $1.5 million which will reduce costs in the waste water and water treatment plants about $4.5 million (average savings to investment ratio of 3 to 1). About 70% of these projects have even higher savings-to-investment ratios. The present schedule calls for 80% completion of the projects by second quarter, 1972; completion on the remaining 20% is fourth quarter, 1972. Monitoring and surveillance
The current program is based mainly on 8-hr and 24-hr composite samples which are taken at key points in the system for oil, total organic carbon, and phenol analyses in the lahoratory. Gas chromatographic analyzers are being used to identify soluble organic chemicals for quick tracing of problems to the source. An effluent monitoring project, based on the application of on-stream analyzers for the semicontinuous monitoring of critical points in the waste water system, is under development. The on-stream analyzer system provides immediate indication of an upset condition, thus allowing faster followup on problems. Data from the analyzer will be fed to a computer. Printouts will be available for routine reports on the performance in the various waste water systems and for quick recall during pollution episodes. The development of this entire effluent monitoring project is expected to re-
I
quire at least three man-years.
ids will require a pended oil and solids the segregated system for . . handling process water requiring +mn+mPn+ treatment. Such a system will leave the existing oily water sewer and separator system for handling only rainfall runoff. More study is required to define the volume of detention that should be provided and the manner of treating prior to discharge. A major problem in this study is providing space for rainfall detention because of limited land availability in the area where waste water is discharged from the refinery.
.......“”
Suspended oil and solids
Acknowledgment
Efficient removal of suspended oil and solids by gravity separators was inadequate; excessive quantities remained in process water. Consequently, additional facilities for removing suspended oil and solids are expected to be required, particularly if activated carbon is selected for additional treatment. Laboratory studies are just under way to compare dissolved air flotation and various sand filtration techniques.
The authors express appreciation to personnel who actively participated in Humble’s pollution abatement programs.
Additional treatment
Facilities will be designed to remove dissolved organics from waste water after maximum volume reduction and elimination of pollutants at the source has been accomplished. Laboratory studies are currently under way comparing biological treating (employing activated sludge) with activated carbon treating. So far, activated carbon treatment appears feasible on strong refinery waste water (after primary treatment only). Several disadvantages to biological treatment may be overcome by activated carbon treating. These include sensitivity of the biological system to fluctuation in hydraulic and organic loadings, toxic shock, and organic sludge disposal problems. Moreover, biological treatment requires substantially more land than facilities employing activated carbon. By the end of 1971, Humble expects to have sufficient data to complete a technical comparison of these two methods on Baton Rouge Refinery waste water so that a process can be selected for development. Rainfall detention
At present, the oily water sewer system handles any rainfall admixed with oily process water. The facilities for additional removal of sus-
Robert T. Denbo, senior staff engineer at Humble’s Baton Rouge Refinery, received his BS degree in chemistry from Louisiana State University. For the past seven years, Mr. Denbo has been involved with environmental quality control at the Baton Rouge Refinery and is presently responsible for environmental planning and development work there. Address inquiries to Mr. Denbo.
Fred W. Gowdy is staff engineer at Humble’s Baton Rouge Refinery. He received his BS and MS in mechanical engineering from Louisiana State University. For the past four years, Mr. Gowdy has been project manager o f the river water replacemenf and inplant waste load reduction projects. Volume 5, Number 11, November 1971 1103
