DEBOTTLENECK SOLUTION FOR DELAYED COKER UNIT

Abstract

The present invention relates to debottleneck solution for delayed Coker unit. More particularly, this invention relates to bottoms of vacuum residuum routed to Coker unit through de-asphalting unit to avoid revamp of existing Coker for the processing of heavier feed stock when there is a change in crude slate. Another object of the invention, in particular, relates to improved delayed coking products, a process used in petroleum refineries to crack petroleum residue, thus converting it into gaseous and liquid product streams and leaving behind solid, carbonaceous petroleum coke.

Claims

1. A process for producing rich feedstock to delayed Coker unit form different crude slate, the process comprising: introducing a feedstock to crude distillation unit after physical and chemical treatment of raw crude; passing the bottoms of the crude distillation unit to vacuum distillation unit for further extraction of product fraction, wherein the bottoms routed for further extraction as feed; contacting at least a portion of the feed with solvent in a de-asphalting unit to obtain a pitch stream containing asphaltenic fraction and predominantly a paraffinic stream containing a de-asphalted oil and the solvent; passing the de-asphalted oil stream to a DAO stripper in SDA unit to obtain a DAO and the residual solvent; heating the de-asphalted oil stream in a furnace to a coking temperature to obtain a hot stream; transferring the hot stream to one of a plurality of coke drums where it undergoes thermal cracking reaction to obtain hydrocarbon vapors and coke; passing the hydrocarbon vapors produced from coking of de-asphalted oil to the fractionator column to obtain various product fraction.

2. The process as claimed in claim 1, wherein the solvent is selected from the group comprising of hydrocarbons having 3 to 6 carbon atoms and mixtures thereof.

3. The process as claimed in claim 1, wherein the feed is selected from vacuum residue, atmospheric residue, cracked vacuum residue from resid Hydrocrackers, Wax Oil (Slop Oil) or blend of hydrocarbons.

4. The process as claimed in claim 1, wherein the product fraction from Coker unit is offgas selected from the group consisting of LPG, naphtha, Kerosene, Light Coker gas oil, Heavy Coker gas oil and Coker fuel oil and Pet Coke.

5. The process as claimed in claim 1, wherein the hydrocarbon vapors from Coker furnace is de-asphalted oil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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:

[0023] FIG. 1 operation of existing Coker unit. FIG. 1 of the present invention represents the operations of existing Coker unit, where the VR bottoms receiving as a feed for Coker unit, wherein the drawbacks as mentioned the performance of the Coker unit is not up to the mark when there is change in crude slate.

[0024] FIG. 2 operation of existing Coker for new feed rate and CCR. FIG. 2 of the present invention represent the operation of existing Coker unit for new feed rate and CCR, In this case Coker requires revamp to manage the new operating scenario.

[0025] FIG. 3 present process scheme using ROSE technology. FIG. 3 of the present invention describes the new process scheme VR bottoms routed to Coker unit through de-asphalting unit, as de-bottleneck solution which eliminates the need of Coker revamp.

[0026] FIG. 4 illustrates an analysis of ROSE Scheme (simplified block flow diagram of FIG. 3).

[0027] FIG. 5 illustrates an Existing Delayed Coker Unit.

[0028] FIG. 6 illustrates a Coker Operation for higher feed rate high CCR requiring revamp (Base Case).

EQUIPMENT DESCRIPTION

[0029] 101: VACUUM DISTILLATION COLUMN [0030] 102: COKER FRACTIONATOR [0031] 103: COKER FURNACE [0032] 104/105: COKE DRUM [0033] 201: VACUUM DISTILLATION COLUMN [0034] 202: COKER FRACTIONATOR [0035] 203: COKER FURNACE [0036] 204/205: COKER DRUM [0037] 301: VACUUM DISTILLATION COLUMN [0038] 302: COKER FRACTIONATOR [0039] 303: COKER FURNACE [0040] 304/305: COKE DRUM [0041] 306: ASPHALTENE SEPARATOR [0042] 307: DAO SEPARATOR [0043] 308: DAO STRIPPER [0044] 309: ASPHALTENE STRIPPER [0045] 310: SOLVENT SURGE DRUM [0046] 311: KBR LICENSED SOLIDIFICATION PROCESS

DETAILED DESCRIPTION

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] In the present invention, VR bottoms or a portion of it routed to DCU through ROSE unit as shown in FIGS. 3 and 4, the said process comprises introducing the vacuum residuum bottoms to solvent containing ROSE unit, predominantly a paraffinic stream containing a de-asphalted oil and the solvent; bottoms of ROSE having pitch stream containing asphaltic fraction, which is processed or handled by using KBR licensed solidification process (AiMS). The flakes thus produced from AiMS has similar properties as Petcoke and it is used as substitute of Petcoke in CFBC boiler and in Cement industry. The de-asphalted oil is routed to Coker unit which is within the hydraulic and quality limits of the existing Coker unit. Passing the de-asphalted stream to a DAO stripper to obtain a DAO stream and the residual solvent; heating the DAO stream in a furnace to a coking temperature to obtain a hot stream; transferring the hot de-asphalted stream to one of a plurality of coke drums where it undergoes thermal cracking reaction to obtain hydrocarbon vapors and coke. The hydrocarbon vapors from the coke drums in Coker unit are routed to fractionator column to obtain product fraction.

[0053] The feed is selected from vacuum residue, atmospheric residue, cracked vacuum residue from resid Hydrocracker, Wax Oil (Slop Oil) or blend of hydrocarbons, hydrocarbon vapors from Coker furnace is de-asphalted oil and the product fraction from Coker unit is offgas selected from the group consisting of LPG, naphtha, Kerosene, Light Coker gas oil, Heavy Coker gas oil and Coker fuel oil and Pet Coke.

[0054] Solvent de-asphalting (SDA) is a process that separates heavy hydrocarbon oil into two phases, an asphalt phase, which contains substances of relatively low hydrogen to carbon ratio often called asphaltene type materials and a de-asphalted oil phase, which contains paraffinic type material substances of relatively high hydrogen to carbon ratio often called De-asphalted Oil (DAO). Hydrocarbons have affinity towards like hydrocarbons, The C3 to C6 paraffinic solvents used have high affinity towards paraffinic material present in vacuum residue.

[0055] The scheme considers an existing DCU (Coker) with nominal design capacity of 1.8 MMTPA for the processing of VR feed containing 19% wt CCR as shown in FIG. 5. As a normal design practice it has been assumed that 10% hydraulic margin is considered for the design of Coker unit and it is still available to utilize. The refinery has two folds plans—(1) to process heavier crude oil (2) with an increase in the crude processing capacity such that there is an increase of 30% in VR rate. The new VR feed has CCR 24.7 wt % as shown in FIG. 6. Such increase in capacity and high CCR goes beyond the design limits of the Coker unit and requires expensive modifications. The high CCR has direct impact on Coker furnace run length and requires significant modifications in furnace, coke drums and other associated equipment.

TABLE-US-00001 TABLE 1 Design Information of Existing Coker Existing DCU Operating Capacity, MMTPA  1.8 Design CCR, wt % 19.0 Overcapacity Available 10% Revamp Conditions Increase in VR feed Rate 30% CCR in Vacuum Residue, wt % 24.7

[0056] The ROSE unit in combination with existing Coker eliminates the need of expensive Coker revamp as shown in FIGS. 3 and 4. Build the ROSE unit independently and integrated with the existing system in short shutdown period whereas the Coker revamp will require longer plant shut down to implement changes leading to production loss. Additionally, the major advantage of present invention KBR scheme is the cost saving in terms of investment required i.e. low cost SDA vs high investment Coker revamp.

[0057] The ROSE unit in this case is a high lift DAO design which acts as a treater for the vacuum residue stream and helps in rejecting CCR in Pitch which is solidified and used as substitute of Petcoke (solid fuel). The DAO thus produced has lower CCR than the new feed and also lower than in original VR feedstock. A small fraction of high CCR feedstock is added to DAO stream to reach up to the allowable limit of CCR (i.e. 19%). The resultant feed rate to Coker in this case is little higher than original feed rate but still within the hydraulic design limits after considering the 10% overdesign available. By the implementation of this scheme since CCR and the feed rate both remains within the design limits, no expensive revamp of Coker is needed.

BEST MODE OF THE INVENTION

[0058] An embodiment of the invention includes a process combining KBR licensed ROSE unit with the existing Coker unit so that existing Coker does not require any revamp by processing de-asphalted oil produced from ROSE unit in a Coker unit.

[0059] The present invention is explained with the following example.

[0060] 1. Existing delayed Coker, which was designed to process vacuum residue having a CCR of 19 wt % with a nominal capacity of 1.8 MMTPA as shown in Figure-1. It is assumed that additional 10% hydraulic design capacity is available to utilize.

[0061] 2. Currently crude processing capacity has been increased such that there is an increase of 30% vacuum residue and crude slate has been changed such that vacuum residue CCR is increased from 19.0 wt % to 24.7 wt %.

[0062] 3. Existing Coker cannot process the new vacuum residue feed as CCR and feed rate exceeds the design range, and hence revamp is required with expensive modifications and longer implementation time. The configuration with revamp requirement is shown in Figure-2.

[0063] 4. KBR licensed ROSE unit combined with the existing Coker is proposed in the present invention to eliminate the need for expensive revamp. The line-up of proposed scheme is detailed below and is shown in Figure-3. [0064] 2.3 MMTPA of vacuum residue having 24.7 wt % of CCR is available to process. A part (1.8 MMTPA) of vacuum residue is routed to ROSE unit instead of directly routing to Coker unit. [0065] Depending on the crude oil being processed, vacuum residue typically contains 15 to 30% asphaltenes. This leaves 70 to 85% of the vacuum residue as potentially recoverable DAO. DAO and asphaltenes will be separated in ROSE SDA unit. ROSE unit uses light hydrocarbon solvent to extract DAO from vacuum residue. [0066] The yield of DAO from the ROSE unit is about 80 wt % with DAO CCR of 16.8 wt %. [0067] The DAO from ROSE unit is routed to existing Coker by mixing with rest of the available vacuum residue of 0.5 MMTPA. The combined flow at the Coker inlet is 2.0 MMTPA and the CCR in combined feed is 19 wt %. [0068] The combined feed to Coker with this configuration is within the design limits of existing Coker; hence, no expensive revamp is required as shown in FIG. 4. [0069] With the proposed configuration, the ROSE unit can be built independently and can be integrated with the existing system in short shutdown period whereas the Coker revamp will require longer plant shut down to implement changes leading to production loss. [0070] The pitch produced from ROSE unit can be solidified in the form of flakes (solid fuel) in KBR licensed solidification process (AiMS). The flakes thus produced has similar properties as Petcoke, can be used as substitute of Petcoke in CFBC boiler, and can be used in Cement industry.

[0071] The words “comprising” and “comprises” as used throughout the claims, are to be interpreted to mean “including but not limited to” and “includes but not limited to”, respectively.

[0072] As used herein, the word “substantially” shall mean “being largely but not wholly that which is specified.”

[0073] As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0074] As used herein, the term “about” in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter).

[0075] As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.