delayed coking

Delayed coking is similar to thermal cracking, except that it heats the material to the temperature required for coking reactions in a short period of time; it prevents cracking reactions from occurring within the furnace tubes, instead delaying such reactions to a dedicated coke tower – which is why it is called \"delayed coking\". The delayed coking unit is mainly composed of 8 parts: (1) the coking section, whose main equipment are the heating furnace and the coke drum. There are configurations with one furnace and two towers, two furnaces and four towers, as well as those that are directly integrated with other devices. (2) The distillation section, whose main equipment is the distillation tower. (3) Coking gas recovery and desulfurization; the main equipment includes absorption/desorption towers, stabilization towers, and reabsorption towers. (4) Hydraulic coking removal section. (5) Dewatering, storage, and transportation of coke. (6) Blowing and venting system. (7) Steam generation section. (8) Coke roasting section. The outlet temperature of the furnace selected domestically is 495–500°C, and the pressure at the top of the coke tower is 0.15–0.2 Mpa. 　　The feedstock for delayed coking can be heavy oil, residue, or even asphalt. Delayed coking products are divided into gas, gasoline, diesel, wax oil, and coke. For domestic residue, the gas yield is 7.0–10%, the crude gasoline yield is 8.2–16.0%, the diesel yield is 22.0–28.66%, the wax oil yield is 23.0–33.0%, the coke yield is 15.0–24.6%, and the excess oil amount is 1–3.0%. Coker gasoline and coker diesel are the main products of delayed coking, but their quality is poor. Coker gasoline has a very low octane rating, typically ranging from 51 to 64 (MON), while diesel fuel has a higher cetane number, usually between 50 and 58. However, both types of oils have high levels of olefins, as well as high contents of impurities such as sulfur, nitrogen, and oxygen; their stability is poor. Therefore, they can only be used as semi-finished products or intermediate materials. Only after refinement can they be used as components in the formulation of gasoline and diesel. Coking wax oil is of poor quality for further processing due to its high contents of sulfur and nitrogen compounds, gums, and char; it is currently typically blended into catalytic or hydrocracking processes as a feedstock. Petcoke is one of the important products of the delayed coking process; depending on its quality, it can be used as electrodes, in metallurgy, and as fuel. After desulfurization, coking gas can be used as a raw material for hydrogen production or sent to the fuel pipeline network as fuel. 　　It is precisely due to the aforementioned advantages of delayed coking that it has seen rapid development in China, mainly because: (1) delayed coking is an effective means of addressing the imbalance between the supply and demand of fuel oil and gasoline. This is because the crude oil in our country is generally heavy and has a high wax content, resulting in a low yield of diesel; the yield of diesel from domestic crude oil is 5–7 percentage points lower on average than that from foreign crude oil. Therefore, at present our country imports approximately 80×104 tons of diesel per year, and at the same time has to export 30×104 tons of gasoline in order to maintain balance between supply and demand domestically. Secondly, since the secondary processing in China’s refining enterprises relies mainly on catalytic cracking, the diesel-to-gasoline ratio is low (1.94 for delayed coking and 0.56 for catalytic cracking). Therefore, developing delayed coking is an effective way to address the supply-demand imbalance in this ratio and increase diesel production. (2) Compared with hydrocracking, although delayed coking has poor stability of light oil products, its low operating costs (the processing cost is about 1/2 to 1/3 of that in hydrocracking) give it strong competitiveness. 　　Due to its advantages of low investment, low operating costs, and high conversion depth, delayed coking has become one of the main processing methods for lightening residue oil. Therefore, given the current financial constraints in our country and the prominent supply-demand imbalance for light oil products, especially the ratio of diesel to gasoline, delayed coking is one of the more ideal solutions to this issue.

There’s a lot to say about delayed coking. 1. May I ask how is the oil-water separation in the overhead oil-water separator tank of the delayed coking unit? Will adding a demulsifier work? 2. Which units’ delayed coking units have three types of sludge reprocessing, and how is the amount of reprocessed sludge measured? What type of flow meter is being used? Where are all the coke inhibitors used in the 3 delayed coking units located? Are there any good calibration methods? How does a 4-stage hydrocyclone separate coke powder from the cold coke water in delayed coking? Where do everyone use the radiation pumps in 5 delayed coking heaters? 6 Coal tar delayed coking 7 For delayed coking units, how is the head pressure required of the high-pressure water pumps determined for different coke drum diameters? 8 Waste coke water from the delayed coking coke yard 9 Please provide statistics on the types and quantities of the three types of additives used in the delayed coking units of various companies! 10 What are the minimum and maximum loads that your delayed coking unit can handle? 11 How is the minimum flow rate for the furnace tubes in a delayed coking heater calculated? 12 Calibration and commissioning of the step-controlled system for delayed coking units 13 Issues with the radiation pumps in delayed coking 14 “Delayed Coking Processes and Engineering” is now available for purchase by colleagues in the coking industry! 15 May I ask how the operating load of your delayed coking unit is determined? 16 What is the minimum flow rate for the furnace tubes in a delayed coking heater? 17 Which equipment determines the bottlenecks in the low-load operation of delayed coking? 18 Summary post on oil refining technology exchanges (Part 1) – Links related to catalytic reforming, catalytic cracking, hydrocracking, delayed coking, etc. 19 Issues related to delayed coking. 20 The coke tank in delayed coking units. 21 Is it necessary to install a bypass line in the oil discharge tank of delayed coking units? 22 Request for assistance with simulating the distillation tower in delayed coking (HYSYS). 23 Which delayed coking units conduct regular analysis of the four components of residue? Is there any practical value in such analyses? 24 How to reduce production fluctuations in delayed coking fractionation towers? 25 Photos of on-site installation of the automatic bottom cover loading/unloading machine for delayed coking coke towers 26 May I ask what is the current technical level of delayed coking units in China? 27 Delayed coking forum 28 What are the main uses of the coke produced in delayed coking units? 29 Precautions for tube charring in delayed coking units 30 For similar delayed coking installations, from which aspects should one start? 31 Delayed coking process and engineering 32 Delayed coking units 33 Some literature on delayed coking 34 What types of reactions occur inside the delayed coking coke tower