Oil Shale, Tar Sands, and Related Materials - American Chemical

15 Commercial-Scale Refining of Paraho Crude

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Shale O i l into Military Specification Fuels N. J. WASILK The Standard Oil Company, P.O. Box 696, Toledo, OH 43694 E. T. ROBINSON The Standard Oil Company, 4440 Warrensville Center Road, Warrensville Heights, OH 44146

In September, 1977 the Standard Oil Company (Ohio) was contracted by the U.S. Navy to refine up to 100,000 barrels of crude Paraho Shale Oil into Military Transportation Fuels. The objective of the program was to demonstrate that shale oil could be converted into stable, specification military fuels utilizing conventional refining technology and in sufficient volumes to support an extensive engine testing program. Yields of JP-5 (jet fuel) and DFM (diesel fuel marine) were to be maximized while minimizing the yield of residual fuel. The crude shale was produced by Paraho Development Corp. over the three year period from 1976 to 1978. Paraho's Anvil Point, Colorado works utilizes a vertical direct heat retort to recover the oil from crushed shale (1). For contractual reasons the program was divided into three phases. During Phase I, the proposed shale oil processing scheme was tested and developed in appropriate pilot plants. Phase II constituted engineering preparation and the actual refinery run. Post run analysis and report writing were completed in Phase III. Paraho Shale O i l The unique nature of crude shale o i l r e q u i r e s s p e c i a l cons i d e r a t i o n i n handling and processing. Table I summarizes some t y p i c a l i n s p e c t i o n s of raw shale o i l and a West Texas crude. In comparison to conventional petroleum, shale o i l has s e v e r a l deleterious characteristics: (1) High n i t r o g e n and oxygen content. (2) Low hydrogen/carbon r a t i o . (3) Low y i e l d of 650°F minus m a t e r i a l ( < 30 v o l . % ) . (4) Moderate a r s e n i c and i r o n content. (5) Suspended ash and water. 0097-6156/81/0163-0223$05.00/0 © 1981 American Chemical Society

In Oil Shale, Tar Sands, and Related Materials; Stauffer, H. C.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

OIL SHALE, TAR SANDS, AND RELATED MATERIALS

224


Table I P r o p e r t i e s of Paraho Shale O i l and West Texas Sour Crude

G r a v i t y , °API S p e c i f i c Gr. @ 60°F Pour Point, °F V i s c o s i t y , SSU @ 60°F @ 100°F @ 210°F V i s c o s i t y - G r . Constant Reid Vapor Pressure, PSI T o t a l A c i d No., mg KOH/gm Asphaltenes, wt.% Ramsbottom Carbon, wt.% B.S. & W., V o l . % S a l t , lb/M B b l s . Elemental A n a l y s i s C, wt.% H, wt.% 0, wt.% N, wt.% S, wt.% Metals As, ppm Na, ppm K, ppm V, ppm N i , ppm Fe, ppm TBP 650°F P o i n t , v o l . % (True B o i l i n g P o i n t )

Paraho Shale O i l

West Texas Sour

20.4 0.9315 +85

34.1 0.8545 F l u i d @ -30

Too heavy 213 44.9 0.8899 1.988 0.889 2.977 0.05* 4.9**

57.1 43.1 0.722 5.1 0.265 1.028 2.65 0.30 3.3

83.68 11.17 1.38 2.02 0.70

0.10 1.40

7.5 0.3 0.17 0.17 2.4 53 28.24

4.4 2.6 2.0 58.64

* (0.06 u n s e t t l e d ) ** (8.20 u n s e t t l e d )



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The high n i t r o g e n content i s probably the l a r g e s t area of concern, as i t i s an order of magnitude higher than that found in petroleum. The technology f o r processing high nitrogen crudes i s not n e a r l y as advanced as comparable technologies f o r d e s u l f u r i z a t i o n or cracking ( i n c r e a s i n g y i e l d of lower b o i l i n g hydrocarbons). Nitrogen compounds are known poisons f o r many petroleum processing c a t a l y s t s such as f l u i d bed catalytic cracking, naphtha reforming and hydrocracking catalysts. In a d d i t i o n , n i t r o g e n compounds have been found to create s t a b i l i t y problems i n g a s o l i n e , j e t and d i e s e l f u e l s . Fuel bound n i t r o g e n w i l l a l s o increase the N 0 emissions from p r a c t i c a l l y any type of combustor. F i n a l l y , n i t r o g e n compounds q u i t e o f t e n have a p e c u l i a r and o f f e n s i v e odor which i s uncommonly d i f f i c u l t to remove (2). X

Shale O i l R e f i n i n g

Process

A schematic of the process developed f o r t h i s program i s shown i n Figure 1. The crude shale o i l i s i n i t i a l l y allowed to s e t t l e batchwise at above ambient temperature. This has been found to be e f f e c t i v e i n breaking the w a t e r / o i l emulsion, thereby p r e c i p i t a t i n g suspended water and ash to the bottom of the tank. The shale o i l i s a l s o pumped through a 20 micron filter enroute to the h y d r o t r e a t e r to remove any entrained debris l e f t i n the tank. After settling, the shale o i l i s mixed with hydrogen, preheated and passed through a guard bed. The purpose of the guard bed i s to remove the organic i r o n and a r s e n i c as w e l l as any ash and s o l i d s which survived the s e t t l i n g and filtering procedure. Following the shale o i l pretreatment steps ( s e t t l i n g and guard bed demetall'ization) the whole shale o i l i s c a t a l y t i c a l l y hydrotreated at elevated temperature and hydrogen partial pressure. Hydrotreating, the most important processing step, i s the c a t a l y t i c r e a c t i o n of hydrogen with s u l f u r , oxygen and nitrogen compounds to form H2S, H2O and NH3, r e s p e c t i v e l y , plus heteroatom-free hydrocarbons. In a d d i t i o n , aromatic s a t u r a t i o n and c r a c k i n g occur to some extent thereby i n c r e a s i n g the hydrocarbon/carbon r a t i o and i n c r e a s i n g the y i e l d of m i l i t a r y f u e l feedstock (650°F minus m a t e r i a l ) . The hydrotreated shale o i l i s f r a c t i o n a t e d by d i s t i l l a t i o n methods into gasoline, jet, diesel, and 650°F bottoms (residua). The j e t and diesel fuel boiling ranges were determined experimentally to meet f l a s h point and freeze or pour point requirements. Some of the r e s i d u a was r e c y c l e d back to the h y d r o t r e a t e r to increase j e t and d i e s e l f u e l y i e l d s .


226

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A final finishing step, acid and c l a y included to meet m i l i t a r y specification gum requirements•

t r e a t i n g , was and s t a b i l i t y


Refinery M o d i f i c a t i o n s P r i o r to the shale o i l operation, f a c i l i t i e s m o d i f i c a t i o n s at the Toledo r e f i n e r y were r e q u i r e d to be able to r e c e i v e , store and process the shale o i l and i t s products without contamination from normal r e f i n e r y stocks. Raw shale o i l was shipped from the Paraho f a c i l i t i e s to Toledo by r a i l r o a d tank c a r . An u n d e r u t i l i z e d r a i l c a r rack was revamped to provide a new unloading as w e l l as a product loading system. A new steam heated tank was b u i l t i n which to store the shale o i l as i t was r e c e i v e d over a 3 month p e r i o d . A hydrocracker which normally processes d i s t i l l a t e fuels i n t o gasoline products was modified to process the shale o i l . New c a t a l y s t (Shell 324) was charged to the f i r s t stage reactor. A guard bed packed with alumina extrudate was placed i n the feed preheat t r a i n . A 20 micron f i l t e r was i n s t a l l e d on the i n l e t l i n e from the shale o i l storage tank. A new s t r i p p e r tower was i n s t a l l e d on the d i s t i l l a t i o n tower to s t r i p the DFM product. Numerous p i p i n g and instrumentation m o d i f i c a t i o n s were made to allow f o r a s i n g l e stage h y d r o t r e a t e r o p e r a t i o n . For a c i d t r e a t i n g of the d i e s e l f u e l and j e t f u e l products a "new" a c i d t r e a t e r was designed and b u i l t , the major v e s s e l of which were refinery surplus equipment. These v e s s e l s included a s e t t l e r , c l a y contactor and sludge storage tank. To provide product storage f o r JP-5 and DFM, two tanks were removed from r e f i n e r y s e r v i c e and cleaned p r i o r to p r o c e s s i n g . A l l l i n e s used f o r shale o i l m a t e r i a l which interconnected with lines c o n t a i n i n g normal r e f i n e r y stocks were either blanked or had the i s o l a t i n g valves chained and locked. Refinery L o g i s t i c s and Process

Flow

When a l l the shale o i l had been r e c e i v e d , the storage tank was heated to 185°F, and an attempt was made to drawoff any free water. No free water was found. The shale o i l r e c e i v e d at Toledo measured only 0.07 v o l . % sediment and water, (B.S.&W.), whereas e a r l i e r p i l o t plant samples contained 0.8 vol.% B.S.&W. The shale o i l was pumped continuously from the tank through the 20 micron feed f i l t e r into the h y d r o t r e a t e r surge drum. From here i t was pumped through the feed preheat s e c t i o n and guard bed together with hydrogen gas and i n t o the reactor. Reactor e f f l u e n t was cooled, water washed and r e c y c l e hydrogen and l i g h t ends removed, p r i o r to e n t e r i n g a muiltidraw d i s t i l l a t i o n column. Here four products were recovered from



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the e f f l u e n t : an overhead g a s o l i n e stock, a j e t f u e l cut (JP-5 or JP-8), a marine d i e s e l f r a c t i o n (DFM) and a bottoms r e s i d u a l fuel fraction. The gasoline stock was sampled, but not recovered i n bulk, instead i t was used as feed to another hydrocracker. The JP-8 was acid t r e a t e d on rundown to a r a i l c a r , while JP-5 and DFM were run down to storage f o r l a t e r acid treating. Any o f f spec JP-5, JP-8 or DFM were returned to the shale o i l storage tank. Part of the bottoms r e s i d u a were r e c y c l e d through the h y d r o t r e a t e r to increase conversion, while the remainder was used as cat cracker feed with a small amount rundown d i r e c t l y to r a i l c a r s f o r recovery as heavy f u e l o i l . Refinery

Run

The h y d r o t r e a t i n g run began on November 4, 1978 and ended on December 4, 1978. In that time 73,100 b a r r e l s of the 88,225 b a r r e l s of shale o i l r e c e i v e d were h y d r o t r e a t e d . However, some of the products fom t h i s volume were returned to the shale o i l storage tank as o f f s p e c i f i c a t i o n product. An e x c e s s i v e l y high pressure drop across the Guard Bed caused the run to be terminated before a l l the shale o i l was processed. The hydrocracker was f i r s t shutdown on day 25 of the run because of a high guard bed pressure drop. The top 25% opf the Guard Bed packing was removed because a black viscous sludge was present on the top of the bed. When returned to o p e r a t i o n , the Guard Bed soon redeveloped a high pressure drop and the run was terminated due to c o n t r a c t u r a l time l i m i t a t i o n s . O r i g i n a l plans c a l l e d f o r the JP products to be acid t r e a t e d on rundown to tankage or r a i l c a r . This plan was modified a f t e r a c i d t r e a t i n g s t a r t u p problems r e s u l t e d i n poor denitrification. The JP-5 was rundown to tankage without a c i d t r e a t i n g , as was the DFM, and both were t r e a t e d a f t e r the h y d r o t r e a t i n g run was complete. F o r t u n a t e l y , the a c i d t r e a t i n g problems were resolved i n time to t r e a t the JP-8 on rundown to a railcar. The r e s i d u a l hydrotreated shale o i l was mixed with r e g u l a r r e f i n e r y cat cracker feed at a rate of 3%, with no d e t e c t a b l e s h i f t s i n y i e l d s or other adverse consequences. S i m i l a r l y , the g a s o l i n e range cut had no detectable e f f e c t s on hydrocracker operations at 1.5% of feed. The shale o i l which remained a f t e r the processing run was burned as b o i l e r f u e l . No problems developed over the 1 month combustion p e r i o d . Following c o n c l u s i o n of the run, an examination of the Guard Bed contents revealed two separate problems, the sludge at the top of the bed and F e S f i n e s throughout the bed. The sludge was t h e o r i z e d to have been formed by a r e a c t i o n between shale o i l , iron, and sulfuric acid. The acid had been x


OIL SHALE, TAR SANDS, AND RELATED MATERIALS

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unwittingly introduced into the shale o i l feed tank by r e c y c l i n g o f f - s p e c JP-5 from the a c i d t r e a t e r during s t a r t u p . A large q u a n t i t y of f i n e s c o n t a i n i n g a high c o n c e n t r a t i o n of FeS was found throughout the bed. Apparently FeS had been d e p o s i t i n g throughout the run and f i l l e d the i n t e r s t i t i a l spaces among the extrudate, thus causing a high pressure drop. x

x


M a t e r i a l Balances E s s e n t i a l l y a l l of the conversion of 650°F plus bottom m a t e r i a l to t r a n s p o r t a t i o n f u e l occurs i n the h y d r o t r e a t i n g step. Table I I compares the o v e r a l l m a t e r i a l balance and y i e l d and n i t r o g e n l e v e l s obtained at Toledo with o r i g i n a l pilot plant r e s u l t s . These data i n d i c a t e that the d e n i t r i f i c a t i o n a c t i v i t y of the c a t a l y s t was c o n s i s t e n t with p r i o r r e s u l t s , however the apparent yield s t r u c t u r e was different. The d i f f e r e n c e s i n y i e l d s are a t t r i b u t e d to two factors: (1) poorer d i s t i l l a t i o n e f f i c i e n c y i n the r e f i n e r y operation and (2) lower DFM pour point and f l a s h point t a r g e t s during the r e f i n e r y run. The a c t u a l conversion of 650°F plus bottoms m a t e r i a l a t t a i n e d i n the r e f i n e r y run i s very s i m i l a r to the pilot plant results. The distillation curve of whole hydrotreated products (minus r e c y c l e ) shown i n Figure 2, i l l u s t r a t e s this observation. Net hydrogen consumption metered i n the r e f i n e r y run was s i g n i f i c a n t l y l e s s than p i l o t plant r e s u l t s ( ^ 1500 versus 1050 SCFB). Chemical a n a l y s i s of the v a r i o u s hydrotreated products i n d i c a t e that the level of aromatic saturation, c r a c k i n g and heteroatom removal f o r both r e f i n e r y and pilot plant were n e a r l y the same. The d i f f e r e n c e i n measured hydrogen consumption i s most probably a r e s u l t of scaleup and p i l o t plant e r r o r . Needless to say, hydrogen consumption i s a very important parameter i n determining overall shale o i l economics. The t o t a l amount of each f i n i s h e d f u e l produced i s shown i n Table I I I . In a c i d t r e a t i n g the y i e l d losses were found to be p o r p o r t i o n a l to n i t r o g e n content and molecular weight of the fuel. For a 3300 ppm n i t r o g e n JP-5 stock, y i e l d l o s s was 4 wt.% and on a 3300 ppm n i t r o g e n DFM the l o s s was 5.4 wt.%. Other l o s s e s i n c u r r e d i n the system were s t a r t u p and l i n e - o u t slop, h e e l l e f t i n feed tanks and t r e a t i n g v e s s e l s and losses during the c l a y column changes. Product

Analyses

Gasoline Stock. Analyses of the r e f i n e r y and p i l o t p l a n t gasoline stocks are shown i n Table IV. Both m a t e r i a l s are very s i m i l a r i n aromatic content, n i t r o g e n l e v e l and octane number.


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Oil

Table I I Shale O i l H y d r o t r e a t i n g Y i e l d s


Gasoline Stock (including Butanes) JP-5 JP-8 DFM Residual Fuel TOTAL H

2

Toledo Refinery Bbls. V o l . % Wt.%N 8743 11.96 0.067

9546 490 18939 37220 74939

13.73

0.220

25.30

0.250

25.90 50.91 102.50

0.340 0.380

34.50 35.20 106.00

0.430 0.220

1500

1050

Cons. SCFB

P i l o t Plant Vol.% Wt.%N 11.00 0.050

Table I I I Net Fuels Produced A f t e r A c i d / C l a y T r e a t i n g Bbls. Gasoline Stock 7,718 JP-5 6,615 JP-8 462 DFM 16,357 Residual F u e l 37,220 Table IV Gasoline Stocks Analyses P i l o t Plant API G r a v i t y Reid Vapor Pressure, p s i Distillation I n i t i a l B o i l i n g P o i n t , °F 10 V o l % Off, °F 50 V o l % O f f , °F 90 V o l T Off, °F End Point % Recovered % Residue Paraffins Monocyclo. P a r a f f i n s Dicyclo Paraffins Alkylbenzenes Indans + T e t r a l i n s Naphthalenes Carbon No. P a r a f f i n s Carbon No. Alkybenzenes Nitrogen, Wt.% Research Octane Number, c l e a r

57.8 1.3 D-86 190 226 258 288 332 99.0 1.0 58.87 29.61 9.97 9.97 0.11 0.33 8.01 7.81 0.040 47

Toledo 54.7 5.6 D-86 100 249 283 317 370 98.0 1.0 49.95 31.62 2.40 15.20 0.51 0.32 9.36 7.85 0.078 Not run


230

OIL SHALE, TAR SANDS, AND RELATED MATERIALS LIGHT ENDS Ho GASOLINE COMPONENTS JP-5

DFM GUARD BED


SHALE OIL SETTLING

HYDROTREATER

RESIDUAL

RECYCLE

FUEL

20

30

Shale oil processing

40

50

60

block-flow

FINISHED

ACID/ CLAY

550 F + BOTTOMS

Figure 1.

10

ACID/ CLAY

JP-5 FINISHED

diagram

•

PILOT PLANT PRODUCT

•

REFINERY

•

RAW SHALE OIL

70

80

DFM

90

PRODUCT

100

CUMULATIVE VOLUME %

Figure 2.

T.B.P. distillation

comparison treated

of pilot plant and refinery whole product


hydro-

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Neither i s s u i t a b l e as a d i r e c t g a s o l i n e blending stock or as reformer feed. A d d i t i o n a l h y d r o t r e a t i n g i s required to reduce the nitrogen content to levels acceptable to catalytic reforming, which i s required to boost the octane number of t h i s material. Jet F u e l s . Product JP-5, before and a f t e r a c i d t r e a t i n g i s compared to p i l o t p l a n t prepared m a t e r i a l i n Table V. Again both stocks have s i m i l a r n i t r o g e n , hydrogen and aromatic content. Note that the thermal s t a b i l i t y of the untreated f u e l i s poor. However, once the n i t r o g e n compounds are s e l e c t i v e l y removed by a c i d t r e a t i n g , the f u e l s s t a b i l i t y as determined by gum and JFTOT (ASTM D-3241) measurements i s very good. In a d d i t i o n , storage s t a b i l i t y c h a r a c t e r i s t i c s of the f u e l s were tested by aging the m a t e r i a l f o r 1 month at 140°F and then repeating the JFTOT and gum t e s t s . The aging t e s t s r e s u l t s , shown i n Table VI f o r a composite sample of a l l treated JP-5 produced at the r e f i n e r y , i n d i c a t e that t h i s f u e l has very good storage s t a b i l i t y properties. 1

D i e s e l Fuel Marine. P h y s i c a l i n s p e c t i o n s of p i l o t plant and r e f i n e r y DFM are compared i n Table V I I . As previously mentioned, the d i s t i l l a t i o n (hence n e a r l y everything e l s e ) are d i f f e r e n t due to r e f i n e r y f r a c t i o n a t i o n p r a c t i c e s and a l t e r e d target specs. Again, a c i d t r e a t i n g i s r e q u i r e d to meet f u e l stability specifications, i.e. ASTM 2274 (accelerated oxidation gum test). These fuels have good combustion p r o p e r t i e s , as shown by the cetane number (^50) and hydrogen contents ( 13 wt.% hydrogen). Residual Fuel. The r e s i d u a l f u e l produced by both the p i l o t and r e f i n e r y meets a l l government s p e c i f i c a t i o n s f o r low s u l f u r , high pour point #6 f u e l o i l . The r e s i d u a l f u e l s are i n f a c t very " c l e a n " as shown i n Table VIII by the high hydrogen and low s u l f u r , metals, carbon and asphaltenes content. This stock i s b e t t e r u t i l i z e d as cat cracker feed than r e s i d u a l f u e l , since higher value gasoline and kerosene f u e l can be e a s i l y produced v i a c a t a l y t i c processing. Product Fuels D i s t r i b u t i o n A l l 6165 b b l s . of the treated JP-5 produced at the Toledo refinery was shipped to Rickenbacher Air Force Base in Lockbourne, OH. The treated DFM was shipped to four destinations: 3021 b b l s . were sent to General Motors D e t r o i t D i e s e l , A l l i s o n Plant #5 i n I n d i a n a p o l i s , IN, 8334 b b l s . were shipped to P h i l a d e l p h i a Naval Base i n P h i l a d e l p h i a , PA, 235 b b l s . were sent to Wright Patterson A i r Force Base, F a i r b o r n , OH and 4785 b b l s . went to the Defense Fuel Support Point i n C i n c i n n a t i , OH. Of the 4670 b b l s . of r e s i d u a l f u e l reserved


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MATERIALS

Table V JP-5 Analyses A - Untreated JP-5

P i l o t Plant


API G r a v i t y

Flash Point °F Freeze Point, °F E x i s t e n t gum (D-381) Mg/100 cc Distillation IBP, °F 10 Vol %, °F 50 Vol %, °F 90 Vol %, °F End P o i n t , °F Nitrogen, Wt. % Paraffins, Vol. % Naphthenes, V o l . % Aromatics, V o l . % JFTOT, V i s u a l (D-3241)

41.8

157 -52 12.2

D-86 356 380 415 456 477 0.32 43.9 33.1 23.0 4 (Fail)

Toledo 42.7

158 -57 Not Run

D-86 370 384 400 436 480 0.29 42.5 36.0 21.5 -

T-5624 K M i l l Spec. 36

Oil Shale, Tar Sands, and Related Materials - American Chemical

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