ТПУС-2 Лекция 1.pptx chemical process the

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1. Chemical Processes: Thermal processes Visbreaking and coking

2. 2 Physical and chemical processes Physical Chemical Thermal Catalytic Distillation Solvent extraction Propane deasphalting Solvent dewaxing Blending Visbreaking Delayed coking Flexi coking Hydro treating Catalytic reforming Catalytic cracking Hydrocracking Catalytic dewaxing Alkylation Polymerization Isomerization

3. Agenda: two processes – visbreaking and coking Introduction Objective, why is that needed and importance Feedstock, products, chemistry Raw materials Outcome of the process (main product) Chemistry of the process Technology Dicsussion of technological scheme of the process Review main parameters Thermodynamics Q&A session Conclusion

4. VISBREAKING PROCESS: introduction Visbreaking is a mild thermal cracking of vacuum or atmospheric residues to produce light products and 75–85% cracked material of lower viscosity that can be used as fuel oil. Also, the cracked oil has to meet EURO 6 oil specifications (which is usually used for undustrial burners) Visbreaking is carried out at conditions to optimize the breaking off of these long side chains and their subsequent cracking to shorter molecules with lower viscosities and pour points. The objective is to reduce the viscosity as much as possible without significantly affecting the fuel stability. Why do we need this process? Why do we need to decrease the viscosity?

5. VISBREAKING PROCESS: introduction Probable answers So, low-viscosity products from visbreaking can be used as a boiler fuel or fuel for furnaces Instead of using dilluients which are expensive, oil visbreaking process can be considered as low-cost process Sometimes, visbreaking process can be used to produce gas oil, the feedstock for hydro- and catalytic- cracking

6. Feedstocks: RAW MATERIAL Atmospheric residue (AR) Vacuum residue (VR) *Vacuum residue is the heaviest distillation product and it contains two fractions: heavy hydrocarbons and very heavy molecular weight molecules, such as asphaltene and resins.

7. Products of the process: Four products are produced in the visbreaking process: 1) gases (C4 ) 2) Naphtha C5 166 C 3) G as oil 166–350 C 4)Residue or tar 350C

8. Products of the process: • Visbreaking results in an increase of API of 2–5 for the vacuum residue feed and a reduction of viscosity of 25–75%.

9. С hemistry of the process: The main reaction in visbreaking is thermal cracking of heavy hydrocarbons, since resins are holding asphaltene and keep them attached to the oil. The cracking of resin will result in precipitation of asphaltene forming deposits in the furnace and will aslo produce unstable fuel oil The possible reactions in visbreaking are: Paraffinic side chain breaking which will also lower the pour point; Cracking of naphthens rings at temperature above 482 C; Coke formation by polymerization, condensation, dehydrogenation and dealkylation;

10. С hemistry of the process: Figure 6.3. Overall chemistry of visbreaking – breaking up long chains of hydrocarbons. Credit: Dr. Semih Eser © Penn State is licensed under  CC BY-NC-SA 4.0

11. TECHNOLOGY: Coil visbreaker: •thermal cracking occurs in the coil of the furnace •same feedstock • same product • different temperature Soak visbreaker •thermal cracking occurs in a soak drum • same feedstock • same product • different temperature

12. TECHNOLOGY: coil visbreaker

13. TECHNOLOGY: coil visbreaker Vacuum or atmospheric residue feedstock is heated and then mildly cracked in the visbreaker furnace. Coil furnace visbreaking is used and the visbroken products are immediately quenched to stop the cracking reaction. The quenching step is essential to prevent coking in the fractionation tower. The gas oil and the visbreaker residue are most commonly used as quenching streams (Parakash, 2003). After quenching, the effluent is directed to the lower section of the fractionator where it is flashed. The fractionator separates the products into gas, gasoline, gas oil and visbreaker tar (residue). The gas oil withdrawn from the fractionator is steam-stripped to remove volatile components and then blended with the visbreaker bottoms or routed for further processing, such as hydrotreating, catalytic cracking or hydrocracking. The un-stabilized naphtha and fuel gas, recovered as overhead products, are treated and then used as feedstock for catalytic reforming, blended into finished products or sent to the fuel system. The visbreaker bottoms are withdrawn from the fractionator, heat exchanged with the visbreaker feedstock, mixed with stripped gas oil (optional) and routed to storage

14. TECHNOLOGY: soaker visbreaker

15. TECHNOLOGY: soaker visbreaker The pre-heated raw material is fed into the furnace, where it is heated up to certain temperature, then its introduced into the soaking-visbeaker reactor after that the cracked material is put into fractionation tower which works under atmospheric pressure

16. TECHNOLOGY: parameters Coil visbreaker: Temperature = 480-500C Residence time = 1,5-2,0 mins Pressure = 1-5M Pa Soak visbreaker: Tempreature = 430-450C Residence time = 10-15 mins Pressure = 1-5M Pa

17. TECHNOLOGY: thermodynamics

18. TECHNOLOGY: comparison Coil visbreaker: High temperature, short residence time Yield = same More stable products Generally more flexible and allows the production of heavy cuts, boiling in the vacuum gas oil range. Soak visbreaker: Lower temperature, long resideence time Yield = same Usually requires less capital investment Consumes less fuel Has longer on-stream times More control-able due to regulations of two variables: pressure and temperature

19. COKING PROCESS: introduction Coking process 1. Delayed coking 2. Fluid coking 3. Flexi-coking

20. The common objective of the three coking processes is to maximize the yield of distillate products in a refinery by rejecting large quantities of carbon in the residue as solid coke, known as petroleum coke.  Coking is the most severe thermal process used in the refinery to treat the very bottom-of-the-barrel of crude oil, i.e., vacuum residue. Coking units convert heavy feedstocks into a solid coke and lower-boiling hydrocarbon products, which are suitable as feedstocks to other refinery units for conversion into higher value transportation fuels. In recent years, coking has also been used to prepare hydrocracker feedstocks and to produce a high-quality “needle coke” from stocks such as heavy catalytic gas oils and decanted oils from the fluid catalytic cracking unit

21. Coking: feedstock and product Raw material: mainly heavy residual oil (tar from VD) and all the resifual such as pyrolysis resins, tar, AR and so on Products: Sponge coke: hard, porous, irregularly shaped lumps ranging in size from 50 cm down to fine dust. Needle coke: microscopic elongated crystalline structure. Needle coke is produced from highly aromatic feedstocks (FCC cycle oils) and used electrode manufacture because of its lower electrical resistivity and lower coefficient of thermal expansion. Shot coke: clusters of shot-sized pellets that characterize it. Produced from some high-sulfur residuals. Shot coke is undesirable because it does not have the high surface area of sponge coke nor the useful properties, characteristic of needle coke, for electrode manufacture.

22. Coking: products Apart from the different types of coke, the coking process can release other products such as: •unsaturated gases (C1–C4) •olefins (C¼ 2 C¼ 4 ) and iC4

23. Coking products application The main uses of petroleum coke are as follows: 1. Fuel 2. Manufacture of anodes for electrolytic cell reduction of alumina 3. Direct use as a chemical carbon source for manufacture of elemental phosphorus, calcium carbide, and silicon carbide 4. Manufacture of electrodes for use in electric furnace production of steel, elemental phosphorus, titanium dioxide, calcium carbide, and silicon carbide 5. Manufacture of graphite

24. Delayed coking Delayed coking is a type of thermal cracking in which the heat required to complete the coking reactions is supplied by a furnace, while coking itself takes place in drums operating continuously on a 24 h filling and 24 h emptying cycles. The process minimizes residence time in the furnace, while sufficient time is allowed in the drums where coking takes place.Coke is rejected in the drums, thus increasing the H/C ratio in the rest of the products. The feed to coker is usually vacuum residue which is high on asphaltenes, resins, aromatics, sulphur and metals. The deposited coke contains most of the asphaltenes, sulphur, and metals present in the feed, and the products are unsaturated gases (olefins) and highly aromatic liquids

25. Delayed coking: technology Delayed coking unit technology main points: The process feeding is continius, but removal or product withdrawal is made by batch The feed firstly injected into the distillation column and them it injected into furnances which are work periodically In mot cases, there are four coke drums which work periodically as well (two of them work, another two prepared for the next proess) Coking process (formation of coke) happens in the coke drums When the coke drums are filled up to 70-80% the fresh coke can be removed from the drum by strong water vapour

26. Delayed coking: affecting parameters High temperature = less volatile materials Average working temperature = 480-560C Coke yield when temperature Why? Short cycle time will increase capacity but will give lower amounts of liquid products and will shorten drum lifetime Increasing pressure will increase coke formation and slightly increase gas yield. However, refinery economics require operating at minimum coke formation. New units are built to work at 1 bar gauge , while existing units work at 2.4 bar. In a case of production of needle coke, a pressure of 10 bar is required. Feedstock variables are the characterization factor and the Conradson carbon which affect yield production. Sulphur and metal content are usually retained in the coke produced.

27. Fluid coking Fluid coking is a thermal cracking process consisting of a fluidized bed reactor and a fluidized bed burner. Coke produced in the reactor is laid down on the coke bed particles, typically in a layering manner. Process description: Vacuum residue is heated to 260 C and is fed into the scrubber which is located above the reactor for coke fine particle recovery, and it operates at 370 C. The heavy hydrocarbons in the feed are recycled with the fine particles to the reactor as slurry recycle. The reactor operating temperature is 510–566 C. The heavy vacuum residue feed is injected through nozzles to a fluidized bed of coke particles. The feed is cracked to vapour and lighter gases which pass through the scrubber to the distillation column. Coke produced in the reactor is laid down on the coke bed particles, typically in a layering manner. Steam is introduced at the bottom of the reactor, where a scrubber is also added to scrub any heavy hydrocarbons from the surface of the coke particles. This steam is also used to fluidize the bed. Part of the coke flows into the burner where 15–30% is combusted by the injection of air into the burner. The rest of the hot coke is recycled back to the reactor to provide the required heat. The operating temperature of the burner is in the range of 593–677 C.

28. Flexicoking It is more complicated form of fluid-coking The flexicoking process is a development of the fluid coking process where only 2 wt% of coke is produced, thus most of the coke is used to heat the feed. A fluidized bed is added to the process which acts as a gasifier in which steam and air are injected to produce synthesis gas called Low Btu Gas (LBG) The gasifier which operates at 816–982 C (1500–1800 F) produces hot coke which remains after combustion. This coke flows into the middle vessel, which acts as a heat exchanger to heat cold coke coming from the reactor. It operates at 593 C (1100 F). The operation of the reactor is the same as fluid coker. The net coke is purged in the heater

29. Conclusion: Comparison of flexi/fluid coking and delayed coking processes: Flexi / fluid coking Delayed coking The liquid product outcome more The liquid product quality is better Continuous process which can reduce the some capital investments Cyclic (batch) process which increases the capital investments Spendings = 3100$ / barrel Spendings = 3400$ / barrel Less outcome of coke Considerable amount of coke is produced Spendings of energy for heaters = 0 Spendings of energy for heaters = high More eco-friendly Less eco-friendly

30. Just nice representation of coking processes in the industry 

31. Q&A session: Students will be asking questions related to the new topic, in case they don’t have any questions, several questions will be asked from the students by teacher

32. Why batch operations not amenable for commercial expansion? Why do we need all these thermal processes? What factor affected the demand for the products from thermal processes? Q&A session: