Chemical Engineering Processes
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Chemical Engineering Processes

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Questions and Answers

What is the main advantage of the absence of the riser in the described reactor?

  • Increased thermal processes
  • Decreased catalyst efficiency
  • Higher coke formation
  • Reduced reaction zone (correct)

    • In the reaction process, the feed is injected at an angle to the catalyst flow.

    False

    What is injected into the first stage riser?

    Fresh feedstock

    The catalyst stripping is more efficient due to the __________ temperature present.

    <p>higher</p> Signup and view all the answers

    What type of feed is introduced in the second stage riser?

    <p>Heavy cycle oil</p> Signup and view all the answers

    The process described increases gas yield while decreasing gasoline yield.

    <p>False</p> Signup and view all the answers

    What facility is used for the separation of products from the catalyst?

    <p>Primary separator and cyclones</p> Signup and view all the answers

    Match the following components with their respective characteristics:

    <p>Fresh feedstock = Easy to crack but difficult to vaporize Heavy cycle oil (HCO) = Opposite adsorption and reaction properties Pre-stripped catalyst = Not treated with steam Regenerated catalyst = Combines with hot catalyst for cooler stream</p> Signup and view all the answers

    The catalyst/products separation occurs in two steps: inside a PRIMARY __________ and externally in __________.

    <p>separator, cyclones</p> Signup and view all the answers

    Which substances were used as classical catalysts in the hydrogenation process?

    <p>Co, Mo, Ni, SULFIDES</p> Signup and view all the answers

    The first step of the process includes reactions that occur at high conditions.

    <p>False</p> Signup and view all the answers

    What are the two main steps in the developed two-stage process?

    <p>Desulfurization and deazotation in the first step; acidic catalyst with low hydrogenation activity in the second step.</p> Signup and view all the answers

    The process involves a _______ solution to keep the temperature at the right value.

    <p>aqueous amine</p> Signup and view all the answers

    Match the following components of the process with their functions:

    <p>High-Pressure Separator = Separates products from hydrogen Amine Scrubber = Removes H2S from gas Fractionator = Separates high-value products Hydrogenation Promoting Catalyst = Facilitates desulfurization and deazotation</p> Signup and view all the answers

    What role do nitrogen compounds and NH3 play in the process?

    <p>Inhibit the acidic sites</p> Signup and view all the answers

    The first reactor is filled with a catalyst that has high hydrogenation activity.

    <p>False</p> Signup and view all the answers

    What is the main product of interest produced from the low-pressure separator?

    <p>Diesel</p> Signup and view all the answers

    The gas resulting from the first stage can be ______ after being treated.

    <p>recycled</p> Signup and view all the answers

    Match the following stages with their characteristics:

    <p>First Step = Desulfurization and deazotation reactions Second Step = Low hydrogenation activity catalyst Gas Recycling = Temperature adjustment Recovery Process = Regeneration of amines</p> Signup and view all the answers

    Which of the following coking processes produces more gasoil?

    <p>Fluidised bed coking</p> Signup and view all the answers

    Asphaltenes are solid at room temperature.

    <p>True</p> Signup and view all the answers

    What is used to collect carbonaceous particles from combustion gases?

    <p>Cyclone</p> Signup and view all the answers

    Flexicoking allows around ____% of the feed to be converted into liquids and gas.

    <p>90</p> Signup and view all the answers

    Match the following products with their respective yields in delayed and fluid coking:

    <p>Gas ≤ C4 = 7.5 (delayed) - 6.5 (fluid) Gasoline = 17 (delayed) - 10 (fluid) Gasoil = 53.5 (delayed) - 72 (fluid) Coke = 22 (delayed) - 11.5 (fluid)</p> Signup and view all the answers

    What is the main difference in the flexicoking process compared to other plants?

    <p>Introduction of a gasifier</p> Signup and view all the answers

    What is a primary benefit of using zeolites as catalysts in cracking processes?

    <p>They allow only small molecules to enter their pores.</p> Signup and view all the answers

    The use of zeolites in catalytic processes provides lower gasoline yields compared to other catalysts.

    <p>False</p> Signup and view all the answers

    What starting material can be used for hydrocracking besides hydrocarbons?

    <p>Cellulose</p> Signup and view all the answers

    The pretreatment of cellulose before hydrocracking involves using _____ to lower the molecular weights.

    <p>alcohol</p> Signup and view all the answers

    Match the catalytic properties of zeolites with their effects:

    <p>Strongly acidic catalytic sites = Enhanced cracking efficiency Uniform pore structure = Selective molecular access High stability and duration = Longer catalyst life Higher gasoline yields = Increased product output</p> Signup and view all the answers

    Which of the following is a feature of zeolites?

    <p>High stability and duration</p> Signup and view all the answers

    The presence of olefins and asphaltenes in feedstock does not affect yield.

    <p>False</p> Signup and view all the answers

    What is the yield range achieved after treating cellulose for hydrocracking?

    <p>C2-C9 yields around 89%</p> Signup and view all the answers

    Only certain products can exit active sites and move through channels, which is referred to as ______ selectivity.

    <p>product</p> Signup and view all the answers

    What role does the composition of the feedstock play in the hydrocracking process?

    <p>It influences the yields and catalyst effectiveness.</p> Signup and view all the answers

    What is the primary use of petroleum coke produced in the process?

    <p>Fuel in power plants</p> Signup and view all the answers

    High pressure water is used to cut petroleum coke from the drum.

    <p>True</p> Signup and view all the answers

    What temperatures are considered optimal for the coke in the reactor during the fluidized bed coking process?

    <p>500-550 °C</p> Signup and view all the answers

    The coker produces different fractions, which are separated in the __________ column.

    <p>rectifying</p> Signup and view all the answers

    Match the product with its subsequent process:

    <p>Fuel gas = Fuel application or other purposes Naphtha = Gasoline production Light Coker Gas Oil = Diesel processing Heavy Coker Gas Oil = Diesel processing</p> Signup and view all the answers

    What happens during the initial stage of the coking process?

    <p>The feed undergoes cracking</p> Signup and view all the answers

    The vapour that did not undergo cracking is sent to the rectifying column.

    <p>False</p> Signup and view all the answers

    What is done to the offline drum before it is opened to the atmosphere?

    <p>Steamed, vented, and cooled</p> Signup and view all the answers

    In the fluidized bed reactor, coke is kept in motion by a flow of __________ entering from the bottom.

    <p>steam</p> Signup and view all the answers

    What is the pressure range mentioned in the content for the cracking unit?

    <p>3-4 atm</p> Signup and view all the answers

    Study Notes

    Catalytic Cracking and Separation Processes

    • FEED is injected perpendicular to catalyst flow, maximizing contact.
    • Products are separated through a two-step process: a PRIMARY SEPARATOR followed by CYCLONES.
    • Absence of a riser minimizes thermal processes, reducing reaction zone size and enhancing catalyst-product separation speed.
    • CATALYST STRIPPING efficiency increased by higher temperatures and lower hydrogen in coke, leading to more liquid yield.

    Dual Risers Cracking System

    • Two risers operate at distinct temperatures and conditions, allowing optimization of selectivity and yields for light oils.
    • Fresh feedstock, easier to crack, is injected into the FIRST STAGE RISER, while HEAVY CYCLE OIL (HCO) is processed in the SECOND STAGE RISER.
    • Excluded part of the exhausted catalyst is mixed with regenerated catalyst to lower temperature.

    RxCat FCC Technology

    • Incorporates pre-stripped catalyst combined with hot regenerated catalyst for improved conversion and selectivity at lower temperatures.
    • Higher catalyst/oil ratio achieved, boosting gasoline and propylene yields while reducing gas yield.
    • Utilizes catalysts containing Co, Mo, and Ni sulfides, sensitive to nitrogen compounds, inhibiting acid sites.

    Two-Step Process

    • FIRST STEP involves desulfurization and deazotation to prevent catalyst deactivation; multiple fixed beds used to manage temperature.
    • SECOND STEP uses acidic catalyst with low hydrogenation activity, managing unreacted feed recycling and utilizing aqueous amine solutions for process stability.

    Zeolite Catalysts

    • Zeolites are effective for catalytic cracking and hydrocracking due to strong acidic sites and uniform pore structure.
    • Their properties include high stability, selectivity for reagents/products, and superior gasoline yields based on molecular size restrictions.
    • Shape selectivity ensures molecules smaller than a certain size access active sites, promoting efficient conversion.

    Hydrocracking of Biomass-Derived Materials

    • Cellulose derived from agricultural residues can be hydrocracked after a pretreatment in alcohol to lower molecular weights.
    • Achieves yields of C2-C9 compounds around 89%.

    Feedstock Properties and Yield Considerations

    • Composition of feedstock is vital for maintaining yields and avoiding catalyst poisoning.
    • Presence of olefins and asphaltenes can hinder performance and result in financial losses.

    Fluidized Bed Coking

    • Coke fluidized bed reactors are coupled with furnace-burner units to maintain coke motion and facilitate cracking at temperatures of 500-550 °C.
    • Vapor from cracking is separated into various fraction cuts; heavier fractions returned for further processing.
    • Generates more gasoil and less gasoline compared to delayed coking.

    Flexicoking Process

    • Integrates a gasifier to enhance flexibility, converting around 90% of feed into liquids and gas.
    • Excess coke can be converted into gas for energy or chemical feedstock.

    Asphaltenes Extraction

    • Asphaltenes, solid at room temperature, can reduce gasoil yield during cracking and hydrocracking if not removed.
    • Deasphalting processes recover non-asphaltene materials, improving overall yields and enabling fuel use in industries like cement and asphalt manufacturing.

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    Description

    Explore the mechanisms of catalyst flow and product separation in chemical engineering. This quiz covers key concepts such as thermal processes, catalyst stripping, and the roles of primary separators and cyclones. Test your knowledge on how these processes influence efficiency and yield.

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