A Process For Production Of Needle Coke

Abstract

The present invention relates to production of high-quality graphite / needle grade coke with reduced impurity levels and improved coefficient of thermal expansion using an integrated hydrotreatment, catalytic cracking and coking reaction sections, employing a combination of highly paraffinic hydrotreated VGO stream and aromatic CLO stream, which is thereafter processed in a delayed coking section.

Claims

A process for production of graphite / needle grade coke with reduced impurity levels and improved coefficient of thermal expansion, wherein the process comprises:(a) routing a vacuum gas oil (VGO) feed (1) to a riser reactor (2) of a fluid catalytic cracking unit, wherein the VGO feed reacts with a hot catalyst supplied from a regenerator (4) and wherein the fluid catalytic cracking unit is operated at a reactor outlet temperature of 550 to 650℃, at a pressure in a range of 0.7 to 2.5Kg / cm2 (g) and having a catalyst to oil ratio in a range of 10 to 25;(b) sending products of reaction from step (a) along with a catalyst to a stripper (3) for separation of a hydrocarbon vapor product (5) from the catalyst;(c) sending the hydrocarbon vapor product (5) to a first fractionator column (6) for separation into different products comprising off gases with naphtha (32), light cycle oil (LCO) (33), and heavy cycle oil (HCO) (34);(d) mixing a VGO stream (7) with H2 (8) and sending to a furnace (9) for heating to obtain a hot feed;(e) sending hot feed (10) from step (d) to a fixed bed reactor (11), wherein the hydrotreatment of a vacuum gas oil (VGO) stream occurs to obtain a hydrotreated VGO stream at a reactor pressure in a range of 30-55 Kg / cm2 (g) and a temperature in a range of 300-380℃, and reaction products (12) are sent to a high-pressure separator (13) where lighter gases (14) are removed and sent to a low-pressure separator;(f) sending a liquid (15) after removing the lighter gases from the reaction products to a second fractionator column (16) for further separation of lighter products (17);(g) routing a stream consisting of the hydrotreated VGO stream (18) from the second fractionator column (16) and a clarified oil (CLO) product fraction to a bottom section of the first fractionator column (6), wherein the clarified oil (CLO) product fraction is generated in the fluid catalytic cracking unit, wherein the hydrotreated VGO stream comprises aromatics 19 wt% and a mixture of paraffins and naphthenes 80 wt%, wherein the CLO product fraction comprises aromatics 98 wt% and a mixture of paraffins and naphthenes 2 wt%;(h) exchanging heat between the hydrotreated VGO stream (18) and the CLO product fraction occurring in the bottom section of the first fractionator column (6) and forming a homogenous mixture, wherein a lighter fraction in the hydrotreated VGO stream boiling at a temperature of not more than 350℃ is separated in the first fractionator column, wherein weight percentage of the hydrotreated VGO stream in the homogenous mixture is in a range of 20-50 wt%;(i) sending the homogenous mixture through a parallel filtration assembly (20) for separation of entrained catalyst fines present; and(j) routing the homogenous mixture after catalyst removal to a third fractionator column (22) of a delayed coking section.The process as claimed in claim 1, the homogenous mixture is mixed with an internal recycle fraction in the third fractionator column (22) of the delayed coking section and is withdrawn from the third fractionator column (22) as a secondary feed (27).The process as claimed in claim 2, wherein the secondary feed (27) is heated in a furnace (28) and a hot feed (29) is produced.The process as claimed in claim 3, wherein the hot feed (29) is sent to a coke drums (30) operated at a temperature in a range of 460-515℃, drum pressure in a range of 2-10 Kg / cm2 (g) and cycle time of 18-42 hrs for delayed coking reaction.The process as claimed in claim 1, wherein a vapor product (31) generated in the coke drums (30) is sent to the third fractionator column (22) for further separation into various streams comprising off gas with naphtha (26), light coker gas oil (LCGO) (23), heavy coker gas (HCGO) (24) and coker fuel oil (CFO) (25).The process as claimed in claim 1, wherein a needle coke produced in the coke drums (30) is removed after a filling cycle by high pressure water jet cutting.The process as claimed in claim 1, wherein after step (f) an aromatic CLO stream (60) is injected at a bottom section of the second fractionator column (59) to mix with the hydrotreated VGO stream (18).The process as claimed in claim 1, wherein sulfur content of the CLO product fraction is not more than 1 wt% and sulfur content of the hydrotreated VGO stream is not more than 0.4 wt%.

Images