【Weekly Topic】Special Lecture on Polymer Materials: “Plastics” – Learn a Little Every Day (9) Producing Olefins “Improve Yourself””

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This post was last edited by tclz007 on 2013-12-16 at 13:04. Starting this month, learning activities will be carried out in the field of polymer materials; we hope that fellow enthusiasts will come to learn, offer good suggestions, engage actively in learning, and those who participate in in-depth discussions will receive substantial rewards in terms of wealth and charms~~~! To encourage everyone to come and participate in discussions more actively, as well as to study more diligently, the top ten participants each time will receive a “Motivation Reward for Active Learning”. Some people might think that it’s terrifying to spend their working days doing nothing useful, performing menial tasks without knowing what to do or what to learn; day after day, year after year, with no vision for their future We must start working hard from now on; even if we learn a little knowledge every day, it will add up over time and help us enrich ourselves. We need to set clear goals – only by filling our minds first can we enrich other aspects of our lives as well. . . . . . It only takes a short ten-odd minutes per day, and you will see the future! ! ! (Anyway, I have learned it; whether you learn it or not is up to you. Apart from those experts like Hai Chuan, there are still others who know it.) . . ) Enough talk – let’s start with the basics today~~! Olefin production process 1. Determination of the process route (1) Evaluation of existing production methods (analysis of process advancement and maturity, technical and economic evaluation): Ethanol dehydration is a mature process with a simple setup and low investment requirements ； Cheap ethanol raw materials are needed. Thermal cracking of hydrocarbons is mature, complex in process, and requires large investment ； Oil prices above $80 per barrel result in a loss of cost advantage. Methanol to ethylene: not yet mature at large scale, with complex processes and high investment costs; it has a cost advantage when oil prices are above $80 per barrel. 2. 3. Analysis of process conditions (1) Reaction principle (known conditions): Primary reactions: The raw hydrocarbons are cracked to produce ethylene and propylene. (1) Alkanes undergo dehydrogenation and chain scission. (2) Naphthenes: Dealkylation – when the side chains are methyl or ethyl groups – followed by dehydrogenation to yield aromatics. (3) Aromatics: Side chain scission, dehydrogenation, and condensation (dehydrogenation occurs more easily than ring opening). Secondary reactions: Lower alkenes such as ethylene and propylene undergo further reactions to produce various products (these reactions are more complex than primary reactions; the alkenes produced in primary reactions are further cracked). The ability of various hydrocarbons to undergo thermal cracking to produce ethylene and propylene. (2) Analysis of reaction process conditions – Temperature: Cracking reactions require the absorption of a large amount of heat. Thermodynamic and kinetic analyses show that high temperatures are favorable for production. Economic considerations and material limitations also play a role. The optimal temperature range is 900–1100°C. (3) Analysis of reaction process conditions – Pressure: It is a gas-phase reaction involving an increase in volume. The effect of concentration changes must also be considered. Thermodynamic analysis indicates that low pressures are advantageous for production, as they increase the conversion rate of reactants. Safety considerations dictate that partial pressures should be reduced (by adding steam). Reasons for adding steam: Advantages include: 1. Reducing the partial pressure of hydrocarbons to increase yields. 2. Maintaining normal pressure to ensure process safety. 3. Facilitating separation. 4. Preventing carbon deposition. 5. Stabilizing temperature, suppressing corrosion, and protecting the furnace tubes. Disadvantages: 1. Reduced production capacity; 2. Increased energy consumption. (4) Analysis of reaction process conditions – time. Kinetic analysis: The competition between first-order and second-order reactions results in an optimal residence time; too long a residence time leads to a decrease in ethylene yield, while a shorter residence time is beneficial for production. Apparent residence time. Conclusion: The key characteristics of hydrocarbon thermal cracking process conditions are high temperature, low hydrocarbon partial pressure, and short residence time. Tubular cracking furnace. II. Process flow for hydrocarbon thermal cracking. 1. Process diagram for hydrocarbon thermal cracking (using light hydrocarbons as raw material); 2. Process diagram for hydrocarbon thermal cracking (using distillate oils as raw material). Everyone is welcome to listen to my broadcasts. I hope those who, like me, want to gain knowledge every day will listen, and that we can all learn together and discuss daily! 【Special Lecture】Special lecture on polymer materials: “Plastics”; continuously being updated. http://bbs.hcbbs.com/thread-1256917-1-1.html