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I. Determining the process route: Except for a small number of new products, the process routes for most domestic chemical technologies have been basically determined. For the same raw materials and the same product, if there are several process routes available, each route is analyzed and compared separately before a decision is made. It is mainly considered from the following aspects: 1. Parameters such as required temperature and pressure. The results achieved among the various approaches are similar; the approach that makes it easier to set the operating parameters should be given priority ； 2. Investment ； 3. Energy consumption ； 4. Safety ； 5. Environmental protection ； 6. Requirements for materials ； 7. Product quality ； 8. Whether it constitutes infringement. II. Data Collection: Collect basic data through experiments (laboratory tests, pilot tests, scale-up tests, industrial production, etc.) or by consulting various sources such as literature, papers, and technical books, using all possible channels (within legal boundaries). This includes: the physical properties of all substances involved in the technology and the interactions between them, all relevant reactions as well as catalysts and reaction mechanisms, etc. At the same time, pay attention to protecting the intellectual property rights arising throughout the process. Regarding reactions: It is well known that reactions are the soul of the entire system and lie at the very core of the \"onion model.\" If there are problems with them, all other efforts become pointless; if they are incorrect, the entire benchmark becomes invalid. So, it’s very, very, very important! Reactions are classified according to the presence of a catalyst: catalytic reactions, uncatalyzed reactions ； Classified by phase: homogeneous reactions, heterogeneous reactions. Regardless of the type of reaction, as a process package developer, it is necessary to have a thorough understanding of the reaction, with a clear and precise knowledge of its mechanism. Research scientists who are only engaged in laboratory research find it difficult to develop proper process packages, and this is constrained by two factors: the first factor is a lack of engineering experience ； Factor two: Lack of production experience from the industrialization era. Technical personnel who only focus on engineering design also find it difficult to develop a proper process package, due to a lack of understanding of reaction mechanisms and relevant data, as well as a lack of production data and experience. Technical personnel who are only involved in production also find it difficult to do a good job, due to the lack of experience and data in research and development as well as engineering design. In the case of catalytic reactions, process package developers must at least be familiar with the physical properties of catalysts, such as strength, porosity, bulk density, active components, and support materials. In addition, it is necessary to understand the chemical properties of catalysts, such as the conversion rate and selectivity of the reaction, factors affecting the reaction (including temperature, pressure, flow rate, component ratios), space velocity, factors that cause catalyst deactivation and poisoning, parameters of reaction thermodynamic equilibrium, reaction kinetic equations, and the steps governing the reaction, among others. Of course, this data can also be provided by the personnel in the project team who specialize in catalyst research and development. In the case of a non-catalytic reaction, it is also necessary to understand the reaction mechanism, factors affecting the reaction, reaction kinetic equations, steps for controlling the reaction, heat absorption/release, consequences of overheating, and protective measures against reaction runaway. Regarding separation and recycling, common separations in chemical plants include gas-liquid separation, absorption, stripping, desorption, distillation, etc. The calculation for ordinary separation tanks is generally based on the diameter of the separated droplets, while high-efficiency separation tanks usually have specific process requirements. The key to absorption is finding the appropriate absorbent. Stripping is used to disrupt the original gas-liquid equilibrium and achieve separation by altering partial pressures; distillation is the reverse process of absorption. Ordinary distillation relies on boiling points for separation, but when there are azeotropes or substances with very similar boiling points, special distillation methods such as azeotropic distillation, extractive distillation, or pressure-swinging distillation can be considered. It needs to be determined after analyzing the specific conditions of the substance to be separated. If the binary interaction parameter is missing from the database, it is necessary to measure the gas-liquid equilibrium data or obtain it by consulting relevant literature. Subsequently, a regression analysis of the gas-liquid equilibrium data is performed to determine the binary interaction parameter, thereby enabling accurate separation calculations to be carried out. Circulation is generally divided into gas-phase circulation and liquid-phase circulation, and it is usually carried out to meet the requirements of reactions or separation. In chemical plants, the one-pass conversion rate for most reactions is not high; therefore, a cyclic process must be employed to achieve higher yields, as in the case of plants for synthesizing ammonia, urea, ammonium carbonate, hydroprocessing coal tar, producing melamine, methanol, ethylene glycol, and so on. Furthermore, for some difficult-to-separate systems, a cyclic approach is also employed in order to achieve high yields and good product quality. The greater the circulation volume and the greater the circulation pressure drop, the higher the energy consumption; there is therefore significant potential for reducing energy use in this area. Generally, the more loops there are, the greater the complexity of the process, and the harder it is to design, control, and operate. Regarding heat transfer, the enthalpy and specific heat values of all substances/flows involved in the collection technology, as well as the heat of reaction, heat of fusion, etc., of all reactions. Heat is recovered through staged heat exchange based on temperature and heat levels within the unit (efforts should be made to recover heat within the unit itself; if heat cannot be recovered there, then recovery should be considered from the perspective of the entire plant). When designing heat exchange networks, it is important to avoid relying solely on theoretical considerations; operational and process feasibility must also be taken into account. Factors such as dew point corrosion, crystallization, blockages, and the impact of gas-liquid phases on catalysts, all resulting from heat exchange, need to be thoroughly considered. Regarding momentum transfer, parameters such as the viscosity and vaporization pressure of all flow streams are collected; piston flow is avoided in two-phase flows, and reasonable equipment layout is used to reduce momentum loss and save energy. III. Process Simulation: For the development of process packages, it is essential to conduct full-process simulation. There are two extreme and incorrect views regarding process simulation. Viewpoint 1: Process simulation is omnipotent; everything can be understood by simulating it ； Viewpoint 2: Process simulation is useless; there are too many influencing factors, so it’s impossible to get accurate results. Both of these views are like trying to understand an elephant by feeling it; they do not allow for an objective understanding of simulation software. Regarding my personal views on simulation, I would like to share my thoughts based on my own practical experience: 1. Process simulation is extremely useful for gaining an understanding of a manufacturing process; especially after conducting a full-process simulation, there is a qualitative improvement in the understanding of the entire system ； 2. Process simulation is not simply a matter of input and output; it requires substantial manual analysis. Every change in a parameter, its influencing factors, as well as the changes throughout the entire system resulting from a change in a parameter, all need to be analyzed one by one. Furthermore, the key data also need to be compared and analyzed with data from experiments, pilot tests, scale-up trials, and industrial production, in order to further refine the model data ； 3. Process simulation is not a panacea; without input, there is no output, and if the input is incorrect, the output will definitely be incorrect. Even if the input is correct, the output may still not match the experimental or production data; it is necessary to conduct a thorough analysis of such discrepancies in order to identify the causes of the inconsistency ； 4. The application of process simulation can **shorten the development time of process packages, reduce the amount of experimental work, guide production, and predict trends in data development** ； 5. Through process simulation, complete data on material and energy balances, as well as property parameters, can be obtained, providing foundational data for engineering design and production ； 6. Various options can be comprehensively compared through simulation to determine the optimal one. Specific work procedures (the following is in my personal style and for reference only): 1. Determine the methods for assessing physical properties based on those properties ； 2. Starting from the reaction, if it is influenced only by thermodynamic equilibrium, then a chemical equilibrium reactor module can be considered, and relevant parameters can be obtained by adjusting the equilibrium temperature difference. If the reaction is influenced not only by thermodynamic equilibrium but also by reaction kinetics, the reaction rate equation and related parameters (including activation energy, pre-exponential factor, adsorption factor, adsorption/reaction equilibrium constants, etc.) are derived through fitting experimental data. These parameters are then used in the reaction module of process simulations, and the simulation results are compared with experimental data for analysis and correction. The purpose is to make the model predictable, thereby providing a reliable basis for industrial scale-up ； 3. Address the issues related to separation and heat exchange. Based on the data collected earlier and the initially developed process flow, conduct simulation calculations (including regression of property data, analysis and calculation of heat exchangers, etc.). Analyze and correct any problems that are identified, and simultaneously perform calculations and comparisons for various possible process flows to determine the optimal one. Once the optimal process flow is identified, further optimization of individual equipment is carried out ； 4. Match utility systems (use as few specifications as possible while also considering the investment). Thus, the simulation work has been basically completed. I hope this casual treatment of the matter will not mislead some people. Because chemical engineering is truly vast and complex; to achieve mastery in even just one aspect of it could require an entire lifetime, yet still might not be sufficient. IV. Complete the PFD, PID, and equipment data sheets. After performing an accurate simulation of the entire process, a complete Process Flow Diagram (PFD) can be obtained. Referring to the process patterns of typical unit equipment and taking into account the characteristics and requirements of the process, the instrumentation discipline is also involved to jointly develop the PID. Based on the information of various streams shown on the PFD, the economical flow velocity is determined, the pipeline pressure drop is calculated, and then the pipe diameter is established. Considering startup and shutdown needs, factors such as purging, catalyst heating and reduction/shutdown protection, presulfurization, etc., are taken into account, along with the necessary start-up/shutdown lines. Design calculations are carried out for all equipment; for standardized equipment, detailed parameters and material selection principles are specified, while for custom-designed equipment, dimensions, size, height, internal components, etc. are calculated. Reactor: It is determined based on a comprehensive consideration of the reaction factors, including the type of reaction (rapid/slow reaction, gas-liquid reaction/gas-gas reaction/liquid-liquid reaction/gas-solid reaction, catalytic/non-catalytic reaction, etc.), catalyst performance (in the case of catalytic reactions), space velocity, reaction rate, reaction control steps, residence time, mass distribution, heat transfer, and scaling effects, among others. Column types: There are packed columns and tray columns; some columns also have a combination of packing and trays. Packed towers generally have low pressure drops, while tray towers have higher pressure drops. Packed towers usually require a higher spray density compared to tray towers. Additionally, the properties of the material being processed also have a significant impact on the choice of tower type. Based on the separation requirements, the feed position is optimized, the reflux ratio and the number of theoretical plates are adjusted; an appropriate flooding coefficient is selected according to the properties of the material, and calculations for the tower are carried out to determine the gas-liquid phase loads, liquid holdup, spray density, and pressure drop for each tray/packing element. Heat exchanger: Import the data from the process simulation into the heat exchanger calculation software to carry out the calculations. The author generally uses the verification mode in HTRI for calculations. In process simulation, the temperature difference between the hot and cold sides is usually maintained at ≥8°C, with efforts made to avoid temperature cross-over. Factors such as fouling thermal resistance, cleaning requirements, thermal expansion, and appropriate margins are taken into account. Depending on the climate conditions and water supply situation at the site where the plant will be built, air cooling is considered; it is generally used in areas with high heat loads and small temperature differences. High-efficiency heat exchangers are considered for applications with high heat exchange requirements, a small temperature difference between the hot and cold sides, low pressure drop requirements, and limited space constraints. Compressor: The type of compressor is determined based on the volume of gas, pressure ratio, and the composition of the gas being transported. Based on the specific conditions of the plant, such as electricity prices, the availability of steam, the possibility of installing boilers or a separate power generation unit, coal prices, and other factors, an decision is made after comprehensive analysis regarding whether to use electric drive or steam drive. When electric drive is used, the compressor generally requires a lower initial investment, occupies less space, and involves less work in operation and maintenance. However, when adjusted for the unit cost of the product, electricity is usually more expensive than steam. If steam drive is used, generally the initial investment for the compressor is high, it requires a large amount of space, and there is a lot of work involved in operation and maintenance. However, when the cost per unit of product is taken into account, steam is usually cheaper than electricity. Of course, there are also some exceptions among factories; therefore, it is necessary to adapt measures to local conditions and never make generalizations! In addition, for systems driven by steam, it is necessary to consider whether the compressor uses a full-condensation, extraction-condensation, or back-pressure design (this needs to be taken into account within the overall steam balance of the plant). If the compressor employs a full-condensation or extraction-condensation design, it is also necessary to decide whether surface cooling should be achieved through water cooling or air cooling, as these two methods have different impacts on the compressor’s steam consumption. Separator: Based on the previous calculations, simply organize the equipment data sheet. Storage tanks: including buffer tanks, intermediate storage tanks, finished product storage tanks, etc., which are determined based on residence time, storage duration, as well as production operational requirements (such as requirements for manual sampling, sealing of products, and transition between shifts, etc.). Other equipment: Customized equipment; detailed specifications regarding external dimensions, internal components, detailed parameters, and process parameters are required ； For shaping equipment, detailed process parameters, process requirements, material selection principles, etc. should be specified. V. Complete the design specifications, instrument specifications, interlock instructions, recommended equipment layout diagrams, etc. At this stage, it is necessary to refer to the requirements outlined in the SHSG 052-2003 Process Design Package for petrochemical plants (a comprehensive set of technical specifications) and carry out each task in accordance with those requirements. Of course, this involves a wide range of knowledge areas and high standards; in addition to process-related aspects, it also covers equipment, instruments, hygiene, safety, environmental protection, analysis, piping materials, layout, production, and more. Therefore, creating a good, mature process package that can be applied in practice truly cannot be accomplished by an individual alone. It must be supported by a good team, one that includes specialists in research and development, technology, engineering, production, etc. Sixth, complete the two main manuals: the analysis and testing manual and the operation manual. To prepare these two manuals, not only a thorough understanding of the manufacturing process is required, but also a large amount of experimental data and results from pilot tests. Furthermore, it is necessary to analyze the involvement of professionals and production technicians in its development; only in this way can the resulting manual be used for staff training, to guide operations during startup and shutdown as well as in accident handling, thus serving a practical purpose.