US2813824A - Process for coking hydrocarbonaceous liquids - Google Patents

Description

Nov. 19, 1957- E. GORIN PROCESS FOR COKING HYDROCARBONACEOUS LIQUIDS Filed March 9, 1955 GAISES HYDROOARBONACEOUS RE YOLE GASES I LIQUID g 2 20 I I 26 1 PRIMARY SECONDARY I6 I VAPOR LTREATING TREATING AQ Q L ZONE ZONE I SWEEP 2 GAS 950- 950- I200F I600F LIQUID women I? l2 FIG. I Q HIGH ASH Low ASH I cox: COKE PITcI- GASES HYDROGARBONAOEOUS REOYGLE GASES LIQUID 4| .40

I Q Q 3 PRIMARY VAPOR i aa- 1'45 RECOVERY 3| TREATING zone SECONDARY 42 sweep 950- TRZEATIENG GAS F 32 LIQUID .950- PRODUCTS I600F a? 44 39 V FIG. 2 PITCH HIGH ASH Low ASH COKE cox:

" INVENTOR. EVERETT GORIN BY ATTORNEY United States Patent'Q i PROCESS FOR COKING HYDROCARBONACEOUS LIQUIDS Everett Gorin, Pittsburgh, Pa., Consolidation Coal Company, poration of Pennsylvania assignor to Pittsburgh Pittsburgh, Pa., a cor- The present invention relates to a process for coking ash-containing hydrocarbonaceous liquids- More particularly, it relates to a process of the continuous type for preparing low-ash-content coke -from high-ash-content hydrocarbonaceous liquids.

Hydrocarbonaceous liquids, especially those derived through pyrolysis of carbonaceous solids, frequently contain substantial quantities of finely divided solids which are ditficult to remove. These finely divided solids are particles of the original carbonaceous solids and partially pyrolyzed solids which become entrained in the pyrolysis vapors. It is not unusual for low temperature coal carbonization liquid products, for example, to contain as much as 15 to 25 percent by weight of these finely divided solid particles which contain all of the ash originally present in the particles prior to carbonization. 'The ash composition of these particles may be as much as to percent by weight.

As used herein, ash is defined as the non-combustible inorganic residue which remains following exhaustivecombustion of the material. I

Cokes produced by thermal treatment of these ash-containing hydrocarbonaceous liquids cannot be marketed as premium carbon sources because of their high ash contamination. The same problem arises in connection with utilization of the products of liquid phase coal hydrogenation, the liquid product resulting from solvent extraction of coal, the liquid product from'oil shale pyrolysis, and like materials having relatively high-ash content.

To utilize these hydrocarbonaceous liquids as a premium solid carbon source, for use as an electrode carbon, for example, they must be converted into a coke having essentially no ash. Filtration of ash-containing solids from the hydrocarbonaceous liquids is diificult and expensive, if possible at all. The fine state of subdivision of the solids results in plugging of the pores of conventional filters; the viscous character of the liquids requires preliminary heating to permit passage through filters. Hence filtration is ordinarily not practiced.

Frequently the more valuable lower boiling liquid con- ;stituents of these hydrocarbonaceous liquids are first re- .covered as product by distillation. The undistilled resi- .due of such distillation hereinafter will be referred to as pitch. In some instances, for example, this undistilled residue boils above 230 C.; in other instances the undistilled residue boils above 300 C.; the precise temperature of separation is determined by the proportions of the starting material and the demand for the lower boiling material. The high boiling undistilled residue usually is referred to as pitch.

I have discovered a method for preparing low-ash carbon solids from high-ash hydrocarbonaceous liquidsby a -two stage thermal treatment. The high-ash liquid is rather than the batch type.

v treatment zone separating non-condensable subjected to a primary thermal treatment under mild cok I 2,813,824 latented Nov. 19, 1957 in'gconditions at 950 to 1200 F. for preparinga high-ash coke containing essentially all of the ash-containing solids in -the' starting liquid together with a small portion of coke derived through thermal degradation of the more readily cokable constituents of the liquid. The uncoked components of the original liquid are recovered from the primary thermal treatment in vapor form, essentially free of ash containing materials. All or a portion of these uncoked vapors are subjected to a secondary thermal treatment under more severe coking conditions at 950 to 1600 F. The secondary thermal treatment produces an ash-free coke suitable as a premium carbon source together with non-condensable gases, low boiling liquid products, and an ash-free liquid residue which may be recycled to the secondary thermal treatment for further coking or may be recovered as a premium quality pitch, if desired. The ash-containing coke produced in the primarythermal treatment may be used as a fuel or as a low grade source of carbon,'such as used in carbide production, metallurgical installations, and the like.

By the term coal as used herein, I comprehend all ranksof coal including anthracite, bituminous, sub-bituminous, lignite and the like. The present invention also finds utility in the treatment of liquid products resulting from the pyrolysis of oil shale.

The present process is applicable to those coking systems which are susceptible to controlled fractional coking, i. e., those systems which are of the continuous type The extent of coking which results in batch processing cannot be controlled withthe precision required to realize the benefits of the present invention. Examples of batch processes are the sole-heated ovensin which a cokable, high boiling, hydrocarbonaceous liquid is heated under quiescent conditions to produce a solid block'of residuum coke. Examples of continuous type processes are those coking systems carried out in fluidized beds, in moving solids' beds, in rotating kilns and the like. i

For a clear understanding of the present invention, its objects and advantages,'reference should be had to the following description and accompanying drawings in which:

v Figure 1 is a flow sheet illustrating the preferred embodiment of the present invention; and

Figure 2 is a How sheet illustrating an alternative method for carrying out the present invention.

The apparatus shown schematically in Figure lincludes a source of high-ash-feedstock 10; heaters 11 and 12 for raising the temperature of liquid feedstock; a primary thermal treatment zone 13; a secondary thermal 14; and a vapor recovery system 15 for gases, liquids and unconverted pitch.

The material used as a feedstock in the present process is a hydrocarbonaceous liquid containing ash. The process is especially applicable to treatment of that fraction of low temperature carbonization tar boiling above 300 C. as well as treatment of the entire liquid product from low temperature carbonization, although it is preferable to remove at least the valuable constituents boiling below 230 C. for recovery prior to thepresent treatment since these materials are susceptible tothermal degradation to less valuable materials. The feedstock, quite viscous at ordinary temperatures, may be heated to facilitate its pumping through pipes. A heater 11 is provided for this purpose. The amount of preheat should be .sufficient to reduce the viscosity of the liquid to permit heater. lreferablythe liquid is preheated to a temperature in the range 200 to 800 F.

Preheated hydrocarbonaceous liquid is introduced into the primary thermal treating zone 13, maintained at a temperature of 950 to 1200 F. This primary treating zone is a suitable coking unit of the continuous type, c. g. 'a fluidizedpitch coker, a downward1y movirig bed pitch "coker, a rotating kilnjapugmilhzarid'the like. Thepri- 'mary zone 13contains amass of heated carbonaceous pebbles. These carbon pebblessupply the necessarysur- "face area for depositionfof a layer of coke from the liquid ffe'edstock. It may be necessary'from timeto'tirneto supply additional seed pellets as nuclei for the formation of additional carbon pebbles. Sweep-"gas is'introducedinto 'the'primary treating zone 13 through'a'conduitflsto allow regulation of the extentof' coking occurring" therein. The 'sweep'gas serves to reduce the partial pressure of the vaporized feedstock and to facilitate removal ofthe vapors from the primary treating zone 13. 'Recycle productga'ses are preferred assweep' gases. The'temperature; residence time and sweep gas rate in the primary-zonal? arereg'w lated toallow only a minimum coking of the liquid portion of the feedstock.

As feedstock is introduced into the-primary treating bed "of carbon pellets, a film of liquid feedstock forms on the surface of eachpebble. The substantial bulk of the feedstock is volatilized and recovered as a vapor through conduit 16. The finely divided ash-containing'parti'cles of the feedstock adhere to the moist surfaces of the carbon pellets and are incorporated into the carb onpellets-during the subsequent coking of the liquid film resulting from its continued exposure to co ng conditions in'the primary zone 13. A portion of the carbon pebbles from the' first zone is removed continuously or intermittently from the 'bed for screening. Oversize pebbles are removed as'product high-ash coke and undersize pebblesare returned to the primary zone for additional size accretion'through further coking. I prefer'tolimit production 'of-high-ash coke in the'primary zone to about 5 to percent ofthe liquid portion of the feedstock by weight.

The total vapors resulting'from :the primary thermal treatment zone are passed'throughpaconduit 16 to a-secondary. thermal treating zone 14, operated under-more severe coking conditions at 950 to 1600 F. In the preferred embodiment shownin Figure 1; thersecondarygtreating zone 14 may function as a; liquid eoker or may function eoncurrently as a' liquid coker and as a retormerto upgrade in quality the uncoked products from the primary treatment. Where the secondary, treating zone is to be operated as a concurrent liquid coker and reforrrien its temperature should be maintained in the range of 1300 to 1600" Where the secondary treating zone is operated as a liquid coker, its temperature should be main- .tained in the: range of 950 to 1200? F. to avoid thermal conversion of the 1uncoked constituents. The;temperature of the secondary treatment zone (as aliquidcoker) need not necessarily behigher than that of theprirnarytreat- ,ment zone since the extent of coking canjbe effectively regulated through control of the sweep gas rate and vap'or residence time. The secondary treating zone 14'c'oiit'ains a heated mass of carbon pebbles'which su ply the necessary surface for the additional "coke: formation. The pebbles in this instance are premium; essentially ash-free, carbon pellets. p I i The vapors entering the secondary treating zone 14'are essentially ash free. A" portion'of the vapbrscon'clenses to form a film upon the surface of the earbonpellets which 7 is converted into coke on extended exposure to the processing conditions in the secondary 'zone'14; When thesecondary treatment zone 14 is operatedfas a concurrent liquid coker and reformer, the uncoked components of the liquid experience a beneficial reforming which results from the severe .thermal conditions maintained in the secondary zone 14. The resulting uncoked vaporsiarerecovered "through a conduit'ls. A portionof the solid -pellets in 5 rently satisfied by high 'Ifdesired, a portion of the'ash-free reformed pi'tchmay be recycled through a conduit 24and heater 12 for further 4 coke" production and reforming in the secondary thermal i preventing its recycle may beconductedunder fluidized conditions. 'i'zed technique provides a sweep gas rates to control maryzone. To produce the'lump form coke product de- 1 'manded in the market, the secondary thermal treating zone -may be operated as a 4 the secondary zone 14 is removed continuously or intermittently through a conduit 19 and screened. Oversize pellets are recovered as product, low-ash, premium carbon; undersize pellets are returned to the secondary zone 14 for additional size accretion through further coking.

The ash-free vapor product from the secondary treatment zone 14 passes through a conduit 18 to the vapor recovery system 15. Non-condensable gases are recovered through a conduit 20 for further processing, for use as fuel or for disposal. If desired, a portion of the noncondensable gases may be returned through conduits 21 and 26 to provide the sweep gas for controlling the coking rate'in'the primary treatingZone 13 and the secondary treatingzone 14 respectively. Low boiling liquid products are recovered through a conduit 22, e. g. those boiling below 300 C. High boiling residue, e. g. pitch boiling above 300 C., is recovered through a conduit 23 as an ash-free reformed pitch. This reformed, ash-free pitch is valuable in itself as an electrode binder, an impregnant, a roofing material, or any of the similar applicationscurtemperature carbonization pitches.

treating zone 14. A portion of the pitch in conduit 23 -'--niust-be'-' removed as' product since the thermal treatment introduces a refractory property to the ash-free pitch, to extinction via continued coking.

Toavoid the operability problems which'arise from the used a moving bed contacting technique for the primary coking' process,"the primary thermal treatment zone 13 The fluidconvenient means for regulating the extent of coking in the pridownwardly moving bed. The alternative embodiment of the present invention 3 illustrated in Figure 2 is adapted to the treatment of ash- #liquids' without the'necessity l valuable lowboiling constituents.

containing .hydrocarbonaceous liquids and particularly to the treatment of a wide boiling range fraction of said for preliminary removal of The apparatus shown in Figure 2 includes a-source of feedstock 30; heaters 31 and 32 for elevating the temperature of liquid feedstock;

- a' 'primary-thermal treating zone 33; a .secondarythermal treating zone 34; and a vapor primary thermal treatment zone recovery system 35. The 33, in structure, operation and function corresponds to the primary zone 13 of Figure l.

- Feedstock fromthe source 30 is heated in the heater 31 to a'pumpable temperature andsubjected to mild coking conditions at 950 to l200 F. in the primary thermal treatment zone 33. High-ash coke pellets are recovered through a conduit 37. Uncoked vapors are recovered through a conduit 36 and sent directly .to the vapor recovery system 35 for recovery of non-condensable gases through a conduit 40 and recovery of low boiling liquid products through aconduit 42. By avoiding treat- 'ment of these vapors under the more severe conversion conditions of thesecondary treating zone 34, loss of valuable low boiling tar acids from the feedstock is minimized. High boilingresidue pitch, ash-free, is recovered 41' 3116 45 to each of the through a conduit 43 and passed to the secondary thermal treating zone 34- through a conduit 44 and heater 32. The secondary treatment zone 34, operated at a temperature of 950to 1600 F.,' corresponds in structure, operasecondary treatment zone 14 shown in Figure l.- Low-ash coke pellets are recovered through a conduit 39 and volatilized portions of the ash- '-free pitch are recovered through a conduit 38 and fractionated in the vapor recovery system 35. -'Recyeling-- of non-condensablegases through. conduits thermal treatment zones, permits independentcontrol over the coking rate occurring in each of the treatment zones.

To illustrate the present invention, according to Figure 1 will be reported The feedstock was low temperature carbonization pitch boiling above 230 C. The pitch, produced in a fluidized low temperature carbonization process, contained 9 percent solids by weight and 0.78 percent ash by Weight. Pitch, preheated to 320 F., was passed downwardly through a primary coker maintained at 1000 F. and containing a downwardly moving bed of devolatilized coke pellets which had been screened to pass through a standard No. 8 mesh and be retained on a standard No. 16 mesh. The pellets were prevented from adhering through the action of a rotating stirrer.

For every 100 lbs. of pitch feedstock, 16.8 lbs. of highash coke were produced in the primary coker vessel. This product coke had an ash-content of 4.5 percent by weight. 97 percent of the ash in the feedstock appeared in the product coke.

83.2 lbs. of vapors were removed from the primary coking vessel and passed without condensation upwardly through a secondary reforming vessel containing a downwardly moving bed of devolatilized coke pellets which had been screened to pass through a standard No. 8 mesh and be retained on a standard No. 16 mesh. The reformer was maintained at a temperature of 1450 F.; no mechanical agitation of the bed was provided. The 83.2 lbs. of primary coker vapors were subjected to the reformer conditions for a contact time of 4 to 5 seconds. 20 lbs. of low-ash coke and 63.2 lbs. of vapors were produced in the reformer vessel. Product coke pellets from the secondary zone had an ash content of 0.115 percent by weight. 20 lbs. of ash-free pitch boiling above 230 C. were available for recycle or for use as premium quality pitch. 43.2 lbs. of gas, liquor and low boiling distillates were recovered.

A material balance for the described operation is presented in Table I.

results of operation by way of example.

43.2 lbs. gas, liquor and distillate.

The original feedstock contained 9 percent by weight of solids in which the ash constituents were concentrated. Based on the 91 lbs. of liquid pitch in the feedstock, 18.6 percent by weight was converted to a high-ash coke and 22 percent by weight was converted to a low-ash coke. An additional 22 percent by weight of the liquid portion of the feedstock was recovered as a pitch available for the production of additional coke by recycling if desired.

According to the provisions of the patent statutes, I have explained the principle, preferred construction and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. The method of preparing low-ash coke from an ash-containing hydrocarbonaceous liquid which comprises passing said liquid through a first mild coking zone at 950 to 1200 F., recovering a high-ash coke therefrom, separately continuously removing therefrom the uncoked portion of the feedstock as a substantially ash-free vapor, passing at least the high-boiling portion thereof through a second thermal treating zone at 950 to 1600' F., re-

6 covering a; low-ash coke and 1 separately continuously .removing the uncoke'd vapor from said second "zone.-

2. The method of preparing low-ash coke from an ash-containing hydrocarbonaceous liquid boiling above 300 C. which comprises passing said liquid through a first mild coking zone at 950 to 1200 F., recovering a high-ash coke therefrom, separately continuously removing therefrom the uncoked portion'of the feedstock as a substantially ash-free vapor, passing, of said ash-free vapor through a second thermal treating zone at 1300 to 1600 F., recovering a low-ash coke and separately continuously recovering uncoked vapors from said second zone.

3. The method of preparing low-a sh coke from an ash-containing hydrocarbonaceous liquid boiling above 300 C. which comprises passing said liquid through a first mild coking zone at 950 to 1200.F., recovering a high-lash coke therefrom, separately continuously removing therefrom the uncoked portion of the feedstock as a substantially ash-free vapor, passing all of said ashfree vapor through a second thermal treating zone at 1300 to 1600 F., recovering a low-ash coke therefrom, separately continuously removing therefrom the uncoked vapors from said second zone, recovering non-condensable gases from said uncoked vapors and recycling at least a portion thereof to said first mild coking zone as sweep gas for limiting high-ash coke production therein to 5 to 15 weight percent of the liquid portion of the feedstock.

4. The method of preparing low-ash coke from an ashcontaining hydrocarbonaceous liquid which comprises passing said liquid through a first mild coking zone at 950' to 1200 F., recovering a high-ash coke therefrom, separately continuously recovering therefrom the uncoked portion of the feedstock as a substantially ashfree vapor, recovering non-condensable gases, low boiling'distillate and high-boiling residue from said ash-free vapor, passing said high-boiling residue continuously through a second thermal treating zone at 950 to 1600 F., and recovering a low-ash coke and separately continuously recovering the uncoked vapors from said second zone.

5. The method of preparing low-ash coke from an ash-containing hydrocarbonaceous liquid which comprises passing said liquid through a first mild coking zone at950 to 1200 F., recovering a high-ash coke therefrom, separately continuously recovering the uncoked portion of' the feedstock as a substantially ash-free vapor, recovering non-condensable gases, low-boiling distillate and high-boiling residue from said ash-free vapor, passing said high-boiling residue continuously through a second thermal treating zone at 950 to 1600 F., recovering a lowash coke and separately continuously recovering the uncoked vapors from said zone, recycling at least a portion of said non-condensable gases to said first zone as sweep gas for limiting high-ash coke production therein to 5 to 15 weight percent of the liquid portion of the feedstock.

6. The method of preparing low-ash coke pellets from an as -containing hydrocarbonaceous liquid which comprises passing said liquid at 950 to 1200 F. through a first mild coking zone containing a bed of particulate carbonaceous solid pellets, passing sweep gas through said first zone to control deposition on the pellets therein of a coke layer containing 5 to 15 percent by weight of the liquid portion of the feedstock together with substantially all of the ash from the feedstock, recovering a. high-ash coke from said first zone, separately continu-- ously recovering therefrom the uncoked portion of the,: feedstock as a substantially ash-free vapor, passing said ash-free vapor at 1300 to 1600 F. through a second. thermal treatment zone containing a bed of particulate, essentially ash-free carbonaceous solid pellets, recovering. essentially ash-free carbonaceous solid pellets from said second zone, retaining uncoked vapors in said second.

said second zone. 7. The methodof claim 6v in which the asheontaim inghydrocarbonaeeous liquid is derived from-coal. 5

References Cited in the file of this patent UNITED STATES PATENTS 1,963,265 Fisher et a1 June 19, 1934 10 '8 'A'lbe ding Aug. 14, 1-934 Ramsburg Aug. 28, 1934 Atwell Dec. 15, 1936 Lefier v- Aug. 31, 1954 Findlay Nov. 9, 1954 Adams Dec. 28, 1954

Claims (1)

1. THE METHOD OF PREPARING LOW-ASH COKE FROM AN ASH-CONTAINING HYDROCARBONACEOUS LIQUID WHICH COMPRISES PASSING SAID LIQUID THROUGH A FIRST MILD COKING ZONE AT 950 TO 1200*F., RECOVERING A HIGH-ASH COKE THEREFROM, SEPARATELY CONTINOUSLY REMOVING THEREFROM THE UNCOKED PORTION OF THE FEEDSTOCK AS A SUBSTANTIALLY ASH-FREE VAPOR, PASSING AT LEAST THE HIGH-BOILING PORTION THEREOF THROUGHH A SECOND THERMAL TREATING ZONE AT 950 TO 1600*F., RECOVERING A LOW-ASH COKE AND SEPARATELY CONTINUOUSLY REMOVING THE UNCOKED VAPOR FROM SAID SECOND ZONE.

Images