L. R. Aalund
Managing Editor-Technology
The reunification of Germany has brought some 22 million tons/year or 435,000 b/d of crude oil processing capacity into the European Economic Community from the former German Democratic Republic or East Germany. Most of this-16.2 million tons or 323,000 b/d-comes from two refineries,
PCK AG Schwedt and Leuna-Werke AG.
Both have entered a period that will test their survival, at least as independent enterprises in their present configurations (OGJ, Oct. 1, pp. 46-47 and Oct. 15, pp. 52-53).
PCK has 218,000 b/d of capacity with a mixture of western and East German technology.
(Although the Germanies have unified, the designations East and West Germany will be used to make distinctions.) Schwedt, about 54 miles northeast of the center of Berlin (Fig. 1) is on the Polish border. It was a grassroots complex that went on stream in 1963.
Leuna has some 105,000 b/d of refining capacity in a sprawling refining/chemical complex in a small town of the same name about 15 miles east of Leipzig. Until recently, the complex produced in addition to transportation fuels nearly 50 chemicals and plastics plus consumer products.
The company has developed and makes practically all the refining catalysts it now uses.
Some of these are also used at the PCK refinery and in other former East Bloc countries, including Cuba.
The Leuna complex traces its origins back to World War 1. It was the venue for historic developments in industrial-scale organic chemistry.
A review of the technology, processing schemes, and hardware at these two refineries reveals the influence of history, state planning, and a state ordered "do it yourself" policy. The latter arose from a shortage of hard currency to pay for foreign technology and a fear of letting engineers and scientists develop contact with the West. Incompetent Communist Party hacks were sometimes put in technical leadership positions.
A result was a deemphasis on pollution control and the institution and preservation, in some cases, of uneconomic technology and procedures. But there were, under the circumstances, some laudable independent process and technology developments and examples of make-do improvisation.
Paradoxically, the western free market also influenced Leuna and PCK. For years they were practically the sole suppliers of gasoline to the island city of West Berlin where West German regulations and western market demand ruled. This made the production of high-octane and unleaded gasolines necessary. Some processes in both refineries reflect this once and still important market. They also reflect a steady diet of Russian crude oil-soviet export blend (SEB) via the "Friendship" pipeline from the distant Urals. The German terminal is at Schwedt. Another line carries it on from there to Leuna.
The relatively poor 32.5 API crude with high sulfur, metals, and bottoms content (see the accompanying assay) has for years been the sole crude oil processed at the refineries. Fortunately, the operators say, the quality has remained remarkably constant over the years. All operations are by necessity oriented toward this one crude.
The existence of this pipeline could be a form of insurance for Leuna and Schwedt, given the German/Soviet economic treaties and Russian needs for hard currency. However, in recent months, the Soviets have been trying harder to meet the demands of their now vocal population. As their production decreases, the pipeline flow declines.
By contract, the Soviet Union was to supply all East German refineries 17 million tons in 1990. Part of this goes to the third largest refinery in East Germany, Hydrierwerk Zeitz GmbH (Fig. 1). It has 74,000 b/d of distillation capacity, a vacuum unit, and hydrocracking and hydrorefining capacity. Two smaller operations account for the remaining capacity.
As of mid-November it appeared the Soviets would fall 5 million tons short, or fulfill only 70% of the contract. PCK Schwedt has lost some 2.5 million tons and is utilizing only about 60% of its crude oil distillation capacity. Whether the lure of hard currency, which will become the medium of exchange starting Jan. 1, draws out more Soviet crude remains to be seen.
But change is coming rapidly. Both refineries are owned by a German federal agency that is trying to sell them wholly or partially (OGJ, Oct. 1, pp. 46-47). Both have shut down obsolete processes this year to improve efficiency. Both could quickly have more major surgery before this article appears.
But this is how it looked inside PCK Schwedt and Leuna a few weeks ago.
PCK SCHWEDT
When the Communists ran East Germany, VEB PCK Schwedt was the most important oil and chemical enterprise in the country. It was a "Kombinat" or combine that controlled a number of major "subsidiaries," including the world-scale ethylene cracker at Bohlen and the organization that ran the entire East German crude and product pipeline system. During its heyday, Schwedt did studies for and provided process training and licenses to many former East Bloc countries and a few western companies.
Now PCK AG Schwedt runs only the refinery. Its process configuration (Fig. 2) and yield structure are similar in many ways to a modern Western refinery. In fact, it was probably the most modern refinery in the East Bloc.
It has in a number of cases multiple units to do the same job. The reason is that before 1970 the communist state required that all units be redundant. The refinery also covers an enormous area for its size because of the open space between most units. This openness of course means greater safety during operations, but it and the redundancy also mean less chance of a knockout blow in case of a bombing attack. The cold war mentality of the time influenced this layout, which resulted in unusually long and expensive runs of piperacks, underground piping, and cables. Fig. 3 shows some of this openness.
The flow diagram, Fig. 2, is an understated representation of what is going on at Schwedt.
The refinery has three atmospheric crude distillation units and associated vacuum units. Capacities, with vacuum capacity in parentheses, in b/sd are:
- No. 1-67,000 (39,700)
- No. 2-67,000 (19,800)
- No. 3-117,000 (43,600)
Soviet export blend crude is, as mentioned, the only oil refined at Schwedt.
The refinery also has multiple catalytic reformers dedicated for specific purposes. Their designation, primary purpose, capacities, and other data are presented in Table 1. There are corresponding hydrotreating units of some 50,000 b/sd total capacity for naphtha pretreating. All use Ni/Mo catalysts developed at Leuna, except the Aromizer hydrotreater which uses a Co/Mo catalyst made there.
Unit No. 5, the Aromizer (Fig. 4), is a continuous catalyst regeneration unit licensed by Institut Francaise du Petrole that stresses benzene-toluene-xylene (BTX) production. But it employs a platinum/rhenium chromium oxide modified catalyst, also developed and made at Leuna. It is designated catalyst 8840.
Before choosing this catalyst formulation, the Leuna researchers screened copper and tin modified combinations before selecting the chromium modified catalyst. They say it showed exceptional catalyst life and the best results in selectivity and stability.
As the flow diagram shows, the reforming capacity sends reformate to gasoline while other streams go to isomerization, reaction, and extraction to make BTX.
OTHER UNITS
Paraxylene made at Schwedt goes to a terephthalic acid plant that employs the Amoco Mid Century process. The 65,000 ton/year acrylonitrile plant uses the Sohio process.
Schwedt also makes ammonia which is further processed to ammonium nitrate and combined with limestone to make a fertilizer.
Some 100,000 ton/year of normal paraffins are extracted from the diesel cut with the East German mol sieve Parex process, which is not related to the UOP process of the same name. The Normal paraffins are used to manufacture detergent.
Until recently, a stream of hydrotreated diesel served as raw material for a yeast plant to make animal feed. Schwedt operators say this was a safe and wholesome product, but the plant was built for the sake of technological prestige, and the product cost too much and had to be subsidized. The plant was shut down this year.
DESUS
The most interesting process arrangement at Schwedt is a sequence of double visbreaking, mild hydrocracking, and fluid catalytic cracking (Fig. 5). Schwedt's first step to bottom-of-the-barrel processing began in 1981 when it started up its UOP fluid catalytic cracker. Table 2 shows the characteristics of the bottoms streams that the Schwedt planners had to consider when making the first step toward bottoms processing.
Also, East German gasoline standards in 1980 required limits of 0.03 wt % sulfur in regular gasoline and 0.05 wt % in the higher octane grade. It would not be possible to meet these standards with untreated SEB vacuum gas oil. Therefore, 80% of the VGO had to be desulfurized. As a result, the Desus (Desulfurization Schwedt) process was developed.
The first unit was rated at 30,000 b/sd, employed two Leuna catalysts in a single reactor, and operated at 500 psig. The developers designated it a "mild hydrotreater." A second Desus unit of 13,650 b/sd, designated a mild hydrocracker (MHC) and operated at 860 psig, was added in 1984. The developers say that mild hydrocracking of the SEB VGO increases the FCC gasoline yield over untreated VGO from 47 wt % to 59 wt %, a jump of 12 percentage points.
Also in 1984, the refinery took a bigger swing at the short resid with a new 30,000 b/sd Shell/Lummus soaker visbreaker. The residue from this unit went to a power station in the refinery with six boilers, each with a capacity of 220 ton/hr of high pressure steam. Up to 50 ton/hr of visbroken residue and other refinery fuel blends and fuel gas were used at peak load during the winter.
Cracked distillates from the visbreaker were also treated in the Desus unit as part of a development program between Toyo Engineering Co. and PCK Schwedt that went back to 1982. Toyo has been involved in major projects at Schwedt since 1977 when it got the order for the FCC unit.
Treatment of the visbreaker distillates was the preamble to the addition of another visbreaker to crack the residue from the first visbreaker and provide more feed for the cat cracker (Fig. 3). The cracker's capacity was significantly increased in 1986 from its original 25,000 b/d.
The second generation visbreaker used the High Conversion Soaker Cracking process (HSC) developed by Toyo Engineering Co. and Mitsui Kozan Chemical Corp.
The developers say the HSC process is an advanced soaker visbreaker technology featuring high conversion and stable residue.
In the process, the feedstock (the Shell/Lummus visbreaker residue) is first heated in a charge heater to 440-460 C. The cracking in the heater tube is minimized by employing high liquid velocity and steam injection. The heater effluent passes into a soaking drum where sufficient residence time is provided to crack to the desired conversion. A 14,000 b/sd HSC unit went on stream in September 1988. It yields 8 wt % light gas oil, 33 wt % heavy gas oil, and 53 wt % residue.
The HSC heavy gas oil was seen as a candidate for cracking in the FCCU, but its 0.4 wt % nitrogen content made it unsuitable. To cope with this, a second reactor was added to the Desus mild hydrocracker and filled with a special catalyst, a Co/Ni catalyst from Leuna designated 8207, for removing the nitrogen.
The developers say that after treatment a 60:40 blend of HSC HGO and virgin VGO contains only 0.011 wt % sulfur and less than 0.01 wt % nitrogen.
The HSC 520+ C. residue, however, contains 3.2 wt % sulfur and 0.93 wt % sulfur. This means the Schwedt power plant where it is burned needs emission control equipment. Toyo and Kerr McGee Corp. are proposing processing the residue with the Residuum Oil Super-critical Extraction (ROSE) process to recover asphaltene free oil and condensed asphaltene solid flakes. After hydrotreating, the oil could serve as an additional FCC feed. Such a unit is not in place at Schwedt or planned.
The FCCU now has a capacity of 40,000 b/sd, 60% higher than original design. It has a high efficiency regenerator, catalyst cooler, and high efficiency regenerator. Catalyst consumption is 0.11 lb/bbl and conversion is 80+ Vol %.
RON of the FCC gasoline ranges from a low of 93 to a high of 96, while the MON has a low of 81.5 and a high of 84.5, the highest in Europe say the operators. No FCC catalysts are produced in East Germany. This unit uses Resoc G from Grace/Davison.
A UOP HF alkylation unit has a capacity of 6,000 b/sd and makes 95 RON clear alkylate.
Though the Soviet crude volumes to Schwedt were decreasing this fall, the refinery was able to keep its FCC loaded. But it no longer sends a VGO stream to Leuna.
LEUNA
The Leuna refinery, while not the most efficient refinery in the world, is certainly the most interesting one. It owes its existence to the lignite reserves in the region of Leuna/Merseburg, which are paradoxically of thin veins and relatively poor quality.
Germany, poor in crude oil reserves and rich in the science of organic chemistry, turned to coal as a major source of fuel and chemicals during the first half of this century, particularly during the war years. A long gone subsidiary of present day BASF AG, Ammoniak Werke Merseburg GmbH, built the world's first ammonia synthesis plant at Leuna in 1916-17. It employed the breakthrough Haber/Bosch process. The first world war ended before the plant was utilized for its original purpose to furnish ammonia for an initial step in gunpowder manufacture, but the technology was employed until the summer of 1990. In 1923, the world's first methanol synthesis plant was built at Leuna.
In 1927, the hydrogenation and liquefaction of lignite to make gasoline began at Leuna under the I.G. Farben-industrie or "dye" cartel, the predecessor of the post-war German chemical giants of BASF AG, Bayer AG, and Hoechst AG. Coal liquefaction continued through World War II on to 1954 when it was shut down. The generation of synthesis gas and processing of tars from lignite, however, continued until this summer when these operations were stopped. Lignite's sole role at the complex now is that of a fuel to produce steam or generate electricity.
The high-pressure reactors from the coal liquefaction era are now the backbone of Leuna's 2 million ton/year (48,000 b/cd) hydrocracking capacity.
Leuna processed some crude-oil atmospheric residue in the hydrogenation chambers as far back as the 1930s. This activity picked up after the second world war, but it was 1977 before the modern 5 million ton/year crude oil distillation unit went on line at Leuna. It was followed in 1978 by a vacuum unit rated at 2.5 million tons/year (50,000 b/cd).
Fig. 6 is a simplified flow diagram of the refinery. (Not shown in the diagram but closely related to refinery operations are an ethylene unit, a low-pressure methanol plant, and a methyl tertiary butyl ether unit.) The imported residue can come from PCK Schwedt or smaller complexes in the area with some refining operations (Fig. 1).
The net effect of this combination, according to Leuna management, is that every 100 tons of crude oil processed produces 49 tons of diesel fuels, 30 tons of gasolines, 18 tons of petrochemical feedstocks, and 3 tons of sulfur and other useful materials.
Resid is eliminated. An interesting step in the scheme is vacuum distillation of the visbreaker residue.
Leuna officially reported that it processed 4,514,000 tons of crude oil and imported 639,000 tons of atmospheric residue and 154,000 tons of vacuum distillate in 1988. In addition, it used 33,600 tons of MTBE.
The refinery produced that year 1.36 million tons of gasoline and 2.0 million tons of diesel fuel.
Current technical management in September confirmed that those figures were essentially correct and that the refinery had been running in 1990 at about the same level as 1988. However, the decreasing Soviet crude supply level is now just as much a factor there as it is at Schwedt.
The program for this year, as in the past year, is to make 1.2 million tons of diesel fuel, with a sulfur limit of 0.2 wt %, and 800,000 tons of 0.45% sulfur diesel for what was formerly inland demand. On Jan. 1, 1991, West German standards with the 0.2% sulfur limit for diesel go into effect. Leuna has been studying ways to cope with this.
The program again also calls for 1.3 million tons of gasoline, with 400 tons of that being unleaded and leaded super. Leaded regular (92 RON) is banned in what was formerly West Germany. But it is allowed in the East, at least temporarily, because so many of the autos made in the East Bloc are still on the road and require it.
West German regular of 92 RON is unleaded. The only leaded gasoline allowed in West Germany is a 98 RON premium gasoline with 0.15 g/l. lead. Unleaded premiums of 95 and 98 RON are also offered.
Though the market is tilted now toward the leaded regular in the East, Schwedt and Leuna will have to move toward more unleaded premium as the western auto population increases and as West German environmental regulations take hold.
CRUDE YIELDS
Management says that per 1,000 tons of SEB crude, the atmospheric and vacuum distillation units yield the following, in tons:
Raw naphtha 199
Raw diesel 229
Atmospheric gas oil 60
Vacuum gas oil 55
Vacuum distillate 172
Vacuum residue 276
Gas 9
Leuna in 1982 added its 26,000 b/d visbreaker to make specification heavy fuel oil. It was designed by M.W. Kellogg and built by Voest Alpine.
In 1986, Leuna began vacuum distillation of the visbreaker residue for several reasons: It was state policy to convert heavy fuel oil into clear product, the heating oil had an unsatisfactory 3% sulfur content, there was a need for more hydrocracker feedstock as demand for gasoline grew, and syngas was needed for chemical synthesis.
The scheme fills these needs, although management admits this was not the most economical route.
The visbreaker vacuum residue is gasified in a Shell gasification unit. The syngas is converted in a low pressure methanol unit with a capacity of 650,000 ton/year methanol. A part of the synthesis gas furnishes hydrogen for refinery processing.
Fig. 7a shows the visbreaker yields and how the visbreaker vacuum distillate joins the original vacuum distillate for feed to the hydrocracking units.
HYDROCRACKING
Today's operators at Leuna have a great deal of flexibility in choosing reactor combinations because they inherited so many from the days of coal liquefaction. The description of the hydrocracking units is complicated by this. At the end of 1945 there were 18 high pressure "chambers" in operation at Leuna. These contained multiple reactors. Inner diameters were primarily 1.2 m (47 in.) with some of the larger ones going to 2.5 m (98 in.). Fig. 8 shows the reactor train today and one track for the huge overhead gantry for working and changing out the reactors. The view has changed little since the 1930s. This is the equipment from which Leuna began putting together a modern hydrocracking system in 1972.
Because of this inheritance, the process development, Leuna management said, took place at an operating pressure of 250 bar (3,625 psi) in contrast to the internationally typical pressure of 150 bar (2,175 psi). This also meant that in contrast to international standards, the particle size of the catalyst had to be from 8 to 10 mm.
The technology has been in change and development since then. There are now "eight to nine" hydrocracking units of varying capacities with four to six reactors each.
Typically today, a unit consists of four reactors in a series. The first three are filled with catalyst 9514 developed at Leuna (see OGJ, Oct. 15, p. 55), the fourth with catalyst 9522 and operated at a pressure of 230 atm, or 3,380 psi.
Feed is the vacuum distillate and visbreaker vacuum distillate in the ratio of 3:1 VD to VVD. The feed typically has a gravity at 20 C. of 0.90-0.915 kg/l., a Conradson number of 0.3%, 1.8-2.0 wt % sulfur, and bromine number of 4-5 g/100 l.
Fig. 7b shows the typical yield. Aim of recent changes in catalysts and conditions was the 350+ C. hydrocracker paraffin stream that was formerly used as a fuel component. Objective was to saturate this stream to a level that made a good ethylene feed. This is reflected in the stream's good BMCI value (Bureau of Mines Correlations Index) of 15-17 and the relatively high hydrogen consumption of the process.
The bulk of this stream goes to the 1 billion lb/year ethylene cracker operated by Sachsischen Olefinwerke at nearby Bohlen. Leuna, Bohlen, and other processing centers around Leipzig are connected by pipelines.
Leuna has its own small ethylene cracker (No. 3) of 200,000 lb/year capacity. This has been a major source of frustration for the operators since it was built in 1986. Leuna management in 1989 said the problems stemmed from a design error by the process licensor. Operations have been improved with post start-up revamp work.
The Shell gasification process provides 115 MMcfd of hydrogen for the hydroprocessing units at Leuna. A catalytic offgas reforming unit also produces hydrogen. The 600,000 ton/year (15,000 b/d) semi-regenerative catalytic reformer yields 18 tons hydrogen/1,000 tons of heavy naphtha throughput.
HCF PROCESS
Leuna specialists describe the HCF or "Hydrocrack Forming" process, Fig. 7c, as the most flexible process at the refinery. It falls between hydrocracking and reforming. Its purpose is to take the heavy diesel components from atmospheric and vacuum distillation, boiling in the range of 270 to 430 C., over a special catalyst and meet market demand for either gasoline or diesel components. System operating pressure is also 230 atm. Fig. 7c shows the options. The unit is rated at 450,000 ton/year (12,000 b/cd).
Also, in the winter with the help of another catalyst present in the unit, the cloud point of the heavy diesel fraction can be improved. A cobalt/copper/wolfram catalyst with a mol sieve-to-alumina silicate ratio of 60:40 converts the gas oil while the following catalyst was specially developed for cracking n-paraffins. Its active components are nickel and wolfram on a carrier of 70:30 mol sieve to amorphous alumina silicate.
OTHER UNITS
The refinery has a diesel hydrotreating unit operating at medium pressure of 360 psig (Fig. 7d).
The catalyst employed reduces the nitrogen brought in by the visbreaker vacuum gas oil. There is a total of 19,000 b/cd of hydrotreating capacity there.
The semi-regenerative catalytic reformer at Leuna employs a platinum/rhenium catalyst. RON for the total reformate runs 92-98; that for the heavy reformate 98-102. The unit operates at 18-19 atm. or 280 psi.
Another octane kick comes from the 45,000 ton/year MTBE plant. The plant, which employs the Huls process, gets isobutylene feed from the Leuna and Bohlen ethylene crackers, though some must be imported. The methanol is produced in the complex.
The plant needs more octane, and management would very much like to install a light straight run isomerization unit as a first step.
A large volume of gas is produced by the cracking processes at Leuna. A low heating value gas is obtained in the first decompression step from some 230 atm. down to 40 atm. It contains primarily hydrogen, methane, and hydrogen sulfide. After desulfurization, this gas covers all process heat needs at the refinery.
Management has considered removing the hydrogen but has not found a suitable process to operate at the necessary pressure. Also, the burner system would have to be revamped in the absence of hydrogen.
In the last decompression step, the ethane, propane, and heavier rich gas are recovered.
Units shutdown this past summer marked the beginning of the end.
And after more than 60 years, the use of lignite as a raw material, in one form or another in the Leuna processing scheme, also ended this summer.
Whether the improvisation and flexibility that characterize the history of this complex since the 1920s can continue and meet the demands of a modern refining industry is a question that will be answered in the coming months.
Copyright 1990 Oil & Gas Journal. All Rights Reserved.
