PROCESS FOR CONVERSION OF RESIDUE EMPLOYING DE-ASPHALTING AND DELAYED COKING

Abstract

The present invention relates to resid processing, particularly related to conversion of resid material with maximum recovery of lighter hydrocarbons. The invented process utilizes a novel scheme for integration of solvent de-asphalting and delayed coking processes to maximize the residue conversion to valuable products, with cleaner quality of middle distillates and fuel oil products, in comparison with other integrated solvent de-asphalting and delayed coking schemes. This process also has an additional flexibility to vary the recycle quantity, without impacting fractionator operation of the delayed coking section, which further enhances the product recovery and achieves maximum conversion of the resid feedstock, with minimum impact on liquid product properties.

Claims

1. An integrated coking and solvent de-asphalting process, the process comprising: (a) introducing a feedstock [1] near to bottom of a fractionator column [2] to obtain a mixed feed [3] drawn out from the bottom of the fractionator column; (b) contacting the mixed feed [3] with a solvent [5] in a extractor [4] to obtain a pitch stream [6] containing asphaltenic fraction and predominantly a paraffinic stream [10] containing a de-asphalted oil and the solvent; (c) passing the pitch stream [6] to a pitch solvent stripper [7] to obtain a residual pitch stream [8] and the solvent; (d) heating the residual pitch stream [8] in a furnace [16] to a coking temperature to obtain a hot pitch stream [17]; (e) transferring the hot pitch stream [17] to one of a plurality of coke drums [18, 19] where it undergoes thermal cracking reaction to obtain hydrocarbon vapours [20] and coke; (f) passing the hydrocarbon vapours [20] to the fractionator column [2] to obtain product fraction.

2. The process as claimed in claim 1, wherein in step (a) the mixed feed [3] comprises the feedstock [1] and an internal recycle stream in the range from 5 to 80 wt % of the feedstock.

3. The process as claimed in claim 1, wherein the solvent to the mixed feed ratio in step (b) is in the range of 2:1 to 50:1.

4. The process as claimed in claim 1, wherein the paraffinic stream [10] is transferred to a solvent separator [11] to obtain the solvent and the de-asphalted oil [12].

5. The process as claimed in claim 1, wherein the paraffinic stream [10] further comprises a lighter paraffinic fraction of the internal recycle stream.

6. The process as claimed in claim 1, wherein the solvent is recovered from the de-asphalted oil [12] in an oil solvent stripper [13] to obtain the solvent and a residual de-asphalted oil [14].

7. The process as claimed in claim 1, wherein the solvent recovered from the pitch solvent stripper [7], the solvent separator [11] and the oil solvent stripper [13] is recycled to the extractor [4].

8. The process as claimed in claim 1, wherein the solvent is selected from the group comprising of hydrocarbons having 3 to 7 carbon atoms and mixtures thereof.

9. The process as claimed in claim 1, wherein the extractor [4] is operated at a temperature in the range of 55 to 300? C.

10. The process as claimed in claim 1, wherein the extractor [4] is operated at a pressure in the range of 1 to 60 kg/cm.sup.2 (g).

11. The process as claimed in claim 1, wherein the coke drums [18, 19] are operated at a temperature in the range of 470 to 520? C.

12. The process as claimed in claim 1, wherein the coke drums [18, 19] are operated at a pressure in the range of 0.5 to 5 Kg/cm.sup.2 (g).

13. The process as claimed in claim 1, wherein residence time of the hot pitch stream [17] in the coke drums [18, 19] is in the range of 10 to 26 hours.

14. The process as claimed in claim 1, wherein the feedstock [1] has conradson carbon residue content in the range of 4 to 30 wt % and density in the range of 0.95 to 1.08 g/cc.

15. The process as claimed in claim 1, wherein the feedstock [1] is selected from vacuum residue, atmospheric residue, shale oil, coal tar, clarified oil, residual oil, heavy waxy distillate, foots oil, slop oil or blend of hydrocarbons.

16. The process as claimed in claim 1, wherein the product fraction is offgas selected from the group consisting of LPG and naphtha [21], Kerosene [22], Light coker gas oil [23], Heavy coker gas oil [24] and Coker fuel oil [25].

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The aforementioned aspects and other features of the present invention will be explained in the following description, taken in conjunction with the accompanying drawings, wherein:

[0020] FIG. 1 illustrates the schematic diagram of the process scheme of present invention.

[0021] FIG. 2 illustrates the schematic diagram of conventional mode of integration of solvent de-asphalting with delayed coker unit.

[0022] FIG. 3 illustrates schematic diagram of process of present invention.

DESCRIPTION OF THE INVENTION

[0023] It should be understood at the outset that although illustrative implementations of the embodiments of the present disclosure are illustrated below, the present invention may be implemented using any number of techniques, whether currently known or in existence. The present disclosure should in no way be limited to the illustrative implementations, and techniques illustrated below, but may be modified within the scope of the appended claims along with their full scope of equivalents.

[0024] The terminology and structure employed herein is for describing, teaching and illuminating some embodiments and their specific features and elements and does not limit, restrict or reduce the scope of the claims or their equivalents.

[0025] Reference throughout this specification to an aspect, another aspect or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase in an embodiment, in another embodiment and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0026] The terms comprises, comprising, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting. Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[0028] Any particular and all details set forth herein are used in the context of some embodiments and therefore should NOT be necessarily taken as limiting factors to the attached claims. The attached claims and their legal equivalents can be realized in the context of embodiments other than the ones used as illustrative examples in the description below.

[0029] In an embodiment, an integrated coking and solvent de-asphalting process, the said process comprises introduction of a feedstock [1] near to bottom of a fractionator column [2] to obtain a mixed feed [3] drawn out from the bottom of the fractionator column; contacting the mixed feed [3] with a solvent [5] in a extractor [4] to obtain a pitch stream [6] containing asphaltenic fraction and predominantly a paraffinic stream [10] containing a de-asphalted oil and the solvent; passing the pitch stream [6] to a pitch solvent stripper [7] to obtain a residual pitch stream [8] and the solvent; heating the residual pitch stream [8] in a furnace [16] to a coking temperature to obtain a hot pitch stream [17]; transferring the hot pitch stream [17] to one of a plurality of coke drums [18, 19] where it undergoes thermal cracking reaction to obtain hydrocarbon vapours [20] and coke; passing the hydrocarbon vapours [20] to the fractionator column [2] to obtain product fraction.

[0030] According to an aspect of the present subject matter, in said embodiment the mixed feed [3] comprises the feedstock [1] and an internal recycle stream in the range from 5 to 80 wt % of the feedstock.

[0031] According to an aspect of the present subject matter, in said embodiment the solvent to the mixed feed ratio in step (b) is in the range of 2:1 to 50:1.

[0032] According to an aspect of the present subject matter, in said embodiment the paraffinic stream [10] is transferred to a solvent separator [11] to obtain the solvent and the de-asphalted oil [12].

[0033] According to an aspect of the present subject matter, in said embodiment the paraffinic stream [10] further comprises a lighter paraffinic fraction of the internal recycle stream.

[0034] According to an aspect of the present subject matter, in said embodiment the solvent is recovered from the de-asphalted oil [12] in an oil solvent stripper [13] to obtain the solvent and a residual de-asphalted oil [14].

[0035] According to an aspect of the present subject matter, in said embodiment the solvent recovered from the pitch solvent stripper [7], the solvent separator [11] and the oil solvent stripper [13] is recycled to the extractor [4].

[0036] According to an aspect of the present subject matter, in said embodiment the solvent is selected from the group comprising of hydrocarbons having 3 to 7 carbon atoms and mixtures thereof.

[0037] According to an aspect of the present subject matter, in said embodiment the extractor [4] is operated at a temperature in the range of 55 to 300? C.

[0038] According to an aspect of the present subject matter, in said embodiment the extractor [4] is operated at a pressure in the range of 1 to 60 kg/cm.sup.2 (g).

[0039] According to an aspect of the present subject matter, in said embodiment the coke drums [18, 19] are operated at a temperature in the range of 470 to 520? C.

[0040] According to an aspect of the present subject matter, in said embodiment the coke drums [18, 19] are operated at a pressure in the range of 0.5 to 5 Kg/cm.sup.2 (g).

[0041] According to an aspect of the present subject matter, in said embodiment the residence time of the hot pitch stream [17] in the coke drums [18, 19] is in the range of 10 to 26 hours.

[0042] According to an aspect of the present subject matter, in said embodiment the feedstock [1] has conradson carbon residue content in the range of 4 to 30 wt % and density in the range of 0.95 to 1.08 g/cc.

[0043] According to an aspect of the present subject matter, in said embodiment the feedstock [1] is selected from vacuum residue, atmospheric residue, shale oil, coal tar, clarified oil, residual oil, heavy waxy distillate, foots oil, slop oil or blend of hydrocarbons.

[0044] According to an aspect of the present subject matter, in said embodiment the product fraction is offgas selected from the group consisting of LPG and naphtha [21], Kerosene [22], Light coker gas oil [23], Heavy coker gas oil [24] and Coker fuel oil [25].

[0045] The liquid hydrocarbon feedstock suitable to be used in the process disclosed herein is selected from hydrocarbon residues like reduced crude oil, vacuum tower bottoms, reduced fuel oil from the bottom of delayed coker quench column etc. The conradson carbon residue content of the feedstock can be above 4 wt %, preferably in the range of 4 wt % to 30 wt % and density can be minimum 0.95 g/cc, preferably in the range of 0.95 to 1.08 g/cc.

[0046] The solvent de-asphalting section of the process disclosed herein operates with solvent to oil ratio in the range of 2:1 to 50:1. Solvents that are suitable to be used include paraffinic hydrocarbons with carbon numbers ranging from 3 to 7. Liquefied Petroleum Gas can also be employed as a solvent for this section. Operating temperature for the extractor can vary from 55 to 300? C. and the pressure from 1 to 60 Kg/cm (g). Solvent is recovered using supercritical operation known in the art and recycled after recovery.

[0047] The coke drums in the delayed coking section of the process disclosed herein is operated at a higher severity with desired operating temperature ranging from 470 to 520? C., preferably between 480? to 500? C. and desired operating pressure ranging from 0.5 to 5 Kg/cm (g) preferably between 0.6 to 3 Kg/cm (g). The residence time provided in coke drums is more than 10 hours, preferably in the range of 10 to 26 hours.

[0048] FIG. 1 illustrates an integrated coking and solvent de-asphalting process. Feedstock (1) is routed to the bottom of the fractionator column (2) where it mixes with the internal recycle fraction and is drawn out from the bottom of the fractionator column as mixed feed (3). The mixed feed is then routed to an extractor (4), where it mixes with the solvent (5) and the heavier aromatic fraction containing asphaltenes get separated out and is drawn from the bottom of the extractor as pitch stream (6). The pitch stream is then sent to a pitch solvent stripper (7) where steam stripping of the more volatile solvent takes place. The paraffinic stream from the top of the extractor containing de-asphalted oil and solvent (10) is sent to a solvent separator (11). The de-asphalted oil (12) containing minor quantity of solvent from the solvent separator is then sent to a oil solvent stripper (13) for further recovery of solvent. The recovered solvent streams (5, 9, 15) are sent back to the extractor (4). The pitch stream (8) exiting the pitch solvent stripper is sent to a furnace (16) for heating to delayed coking temperatures. The hot pitch stream (17) exiting the furnace is then routed to one of the two coke drums (18, 19) where an extended residence time is provided to the feed for completion of thermal cracking reactions. The product hydrocarbon vapours (20) exiting the coke drum are sent to the fractionator (2) for further separation into desired products. Gaseous products (21) exiting the fractionator top are routed to a gas concentration section for further separation. Liquid products like kerosene (22), Light Coker Gas Oil (LCGO) (23), Heavy Coker Gas Oil (HCGO) (24) and Coker Fuel Oil (CFO) (25) are also withdrawn from the column.

[0049] FIG. 2 illustrates conventional mode of integrated solvent de-asphalting unit with delayed coker unit; it describes an integration of solvent deasphalting with delayed coking process being done conventionally. Vacuum residue feedstock (30) is sent to a solvent deasphalting unit (31) where the deasphalted oil (33) is taken out. The pitch (32) is then sent to the fractionator column bottom (34) of the delayed coker unit. The pitch is mixed with the internal recycle fraction and the combined pitch and recycle stream (36) is sent to the furnace (37) of the delayed coker unit. The hot feed (38) exiting the furnace is then sent to the coke drums (39) for reaction. The reaction products (40) are sent to the fractionator of the delayed coker unit for further separation to desired products (35). Here, in this sort of scheme of integration, the product quality is hampered when we maximize yields because of the higher heaviness of the pitch compared to the vacuum residue feedstock in terms of carbon residue content. The heavy pitch material sent to the delayed coker unit generates heavier products compared to that from vacuum residue feedstock. This necessitates the operation of fractionator at high recycle ratio (higher internal recycle fraction to be dropped into bottom feed) in order to maintain the product quality. But, this high recycle operation causes a deterioration in the yield pattern in the delayed coker section, in terms of higher coke yield compare to low recycle operation.

[0050] FIG. 3 illustrates an embodiment of the process of present invention, the vacuum residue feedstock (41) is sent directly to the bottom of fractionator column (42) of the delayed coker unit. The fractionator is operated at high recycle ratio and the internal recycle fraction mixes with the vacuum residue feedstock and the combined feed stream (44) is sent to the solvent deasphalting unit (45). In the solvent deasphalting unit, the deasphalted oil along with the lighter hydrocarbons of the internal recycle fraction are separated out as the deasphalted oil (51). The pitch along with the heavy hydrocarbons of recycle fraction (46) is sent to the furnace (47). The hot feed stream (48) exiting the furnace is then sent to the coke drums (49) for reactions. The vapor products (50) from the reaction are sent to the fractionator column (42) for separation into desired products.

[0051] The process integrating coking and solvent de-asphalting is further exemplified by following non-limiting examples.

Example-1

[0052] Vacuum residue feedstock of properties as provided in Table-1 was taken for the study.

TABLE-US-00001 TABLE 1 Properties of feedstock used in this invention Feed Properties Value CCR (wt. %) 22.05 Asphaltene (wt. %) 7.1 Sulfur (wt. %) 5.18 Na (ppm) 4 Mg (ppm) 1 Ni (ppm) 91 V (ppm) 146 Fe (ppm) 10 Paraffins (wt. %) 43.5 ASTM D 2887 Distillation, (wt. %/? C.) 514/590/608 IBP/30/50

[0053] In the first step, said vacuum residue feedstock is subjected to solvent de-asphalting at two solvent/oil ratios. De-asphalted Oil yield of 23 and 50 wt % were obtained from the de-asphalting process. The detail of solvent de-asphalting experiments is provided in Table-2.

TABLE-US-00002 TABLE 2 Solvent de-asphalting experimental data Run 1 Run 2 LPG Solvent/Oil ratio (vol./vol.) 3.5 4.8 De-asphalting temperature, ? C. 85 90 CCR of VR, wt. % 22.05 22.05 Pitch yield, wt. % 77 50 Pitch CCR, wt. % 28 35.2 DAO yield, wt. % 23 50 DAO CCR, wt. % 2.5 7.04

[0054] The pitch is then subjected to coking in batch coker experimental reactor set up. An experiment was conducted with using vacuum residue feedstock also, in the batch coker reactor for data comparison. Results of the batch coker experiments are provided in Table-3.

TABLE-US-00003 TABLE 3 Batch coker experimental data Vacuum Pitch from Pitch from Feed residue Run-1 Run-2 Coking temperature, ? C. 486 486 486 Reactor pressure, Kg/cm.sup.2 (g) 1.05 1.05 1.05 Coke yield, wt % of feed 36 45.35 49.82 ? Coke yield [VR-Pitch] (neglecting ?1.08 ?11.09 DAO coke), wt %

Example-2

[0055] Another set of experiments were carried out using solvent de-asphalting employing n-pentane solvent and batch coking employing vacuum residue feedstock of Table-1. The detail of solvent de-asphalting experiments is provided in Table-4.

TABLE-US-00004 TABLE 4 Solvent de-asphalting experimental data RUN: 1 RUN: 2 Solvent/Oil ratio (wt./wt.) 2 3 De-asphalting temperature, ? C. 50 50 Pitch yield, wt. % 25 24 DAO yield, wt. % 75 76 Pitch CCR, wt. % 29.33 33.54 DAO CCR, wt. % 20.02 17.61

[0056] The pitch is then subjected to coking in batch coker experimental reactor set up. An experiment was conducted with using vacuum residue feedstock also, in the batch coker reactor for data comparison. Results of the batch coker experiments are provided in Table-5.

TABLE-US-00005 TABLE 5 Batch coker experimental data Vacuum Pitch from Pitch from Feed residue Run-1 Run-2 Coking temperature, ? C. 486 486 486 Reactor pressure, Kg/cm.sup.2 (g) 1.05 1.05 1.05 Coke yield from batch coker, wt % 36 47.52 54.34 ? Coke yield [VR-Pitch-DAO Coke as ?2.91 ?3.06 0.8 * feed CCR], wt. %

Example-3

[0057] A case is provided as Table-6 wherein the stream summary of two schemes is compared. It can be seen that in the first case, 100 MT/hr vacuum residue feed is routed to Solvent De-asphalting (SDA), from which 50 wt % of pitch and DAO are generated. Pitch is then sent to the delayed coker fractionator, where it mixes with 5 MT/hr of recycle fraction (at 10% recycle) and enters the coke drums.

[0058] In the second case, 100 MT/hr vacuum residue feedstock is routed to (Delayed Coker Unit) DCU main fractionator column, where it mixes with 10 MT/hr recycle fraction (at 10% recycle) and enters the SDA unit. The recycle fraction generally contains much lesser quantity of asphaltenes compared to the vacuum residue feedstock and therefore is recovered along with the DAO (50+10 MT/hr). The neat pitch is sent to the coke drums for delayed coking reactions, thereby achieving zero recycle operation of the delayed coking section.

TABLE-US-00006 TABLE 6 Stream comparison SDA .fwdarw. DCU main DCU main fractionator.fwdarw. fractionator.fwdarw. Furnace.fwdarw.Coke SDA.fwdarw.Furnace Vacuum residue routed to drums .fwdarw.Coke drums Feed to SDA, MT/hr 100 110 DAO yield, MT/hr 50 60 Pitch yield, MT/hr 50 50 Pitch entering Coke drums, MT/hr 50 50 Recycle fraction entering Coke 5 0 drums (assuming 10% recycle ratio), MT/hr Product recovered from DCU main 50 40 fractionator, MT/hr

[0059] While specific language has been used to describe the present subject matter, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein. The drawings and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment.