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Approaches and steps for process package development 1. Determine the process route. Except for a small number of new products, in most domestic chemical technologies, the process route has already 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 across the various approaches are similar; the approach that makes it easier to set the operational parameters should be given priority ； 2. Investment ； 3. Energy consumption ； 4. Safety ； 5. Environmental protection ； 6. Requirements for materials ； 7. Product quality ； 8. Whether there is any infringement. 2 Data collection: Collect basic data through experiments (laboratory, pilot scale, pilot plant, 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 the protection of intellectual property rights formed throughout the process. //Regarding the reaction: As is well known, the reaction is the soul of the entire system and lies at the very core of the \"onion model.\" If there are problems with it, all other efforts are in vain; if it is incorrect, the entire benchmark becomes invalid. So, it’s very, very, very important! Reactions are classified based on 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, one must have a thorough understanding of the reaction; the reaction mechanism should be crystal clear and well-understood. Researchers who are only engaged in laboratory research find it difficult to develop proper process packages, which is constrained by two factors: the first factor is the lack of engineering experience ； Factor two: Lack of production experience from the industrial era. Technical personnel who only handle 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 production experience. It’s also difficult for technicians who do only production work to perform well, due to a lack of experience and data in research, development, and engineering design. For catalytic reactions, process package developers must have at least a basic understanding of the physical properties of catalysts, such as strength, porosity, bulk density, active components, and support. 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 absorbed or released, consequences of overheating, and protective measures against reaction runaway. //On 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 break the original gas-liquid equilibrium and achieve separation by changing partial pressures; desorption is the reverse process of absorption. Ordinary distillation relies on boiling points for separation. When there are azeotropes or substances with very similar boiling points in the mixture, special distillation methods such as azeotropic distillation, extractive distillation, or pressure-swapped 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, which is then required to carry out accurate separation calculations. 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 approach must be employed to achieve higher yields, as in the case of plants for ammonia synthesis, urea production, ammonium carbonate synthesis, coal tar hydrogenation, melamine production, methanol production, and ethylene glycol production. In addition, for some difficult-to-separate systems, a recycling method 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 higher the complexity of the process, and the greater the difficulty in designing, controlling, and operating it. //Regarding the enthalpy and specific heat values of all substances/flows involved in heat transfer//collection technologies, as well as the heat of reaction, heat of fusion, etc., of all reactions. Heat is recovered within the unit through heat exchange along temperature and thermal gradients (whenever possible, heat recovery should be considered within the unit; for any heat that cannot be recovered within the unit, heat recovery should be considered from a plant-wide perspective). 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: Collect parameters such as the viscosity and vaporization pressure of all flow streams; avoid piston flow in two-phase flows, and reduce momentum loss through appropriate equipment layout to save energy. 3 Process simulation: For the development of a process package, conducting full-process simulation is essential. 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 the above viewpoints are like blind men touching an elephant; they fail to provide an objective understanding of simulation software. //The correct understanding of simulation // 1. Process simulation is very helpful for understanding a 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 merely about input and output; it requires a great deal of human analysis. Every change in parameters and their influencing factors, as well as the resulting changes throughout the entire system due to a single parameter change, must be analyzed individually. 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; there is no output without input. If the input is incorrect, the output will definitely be wrong. 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 mismatch ； 4. The application of process simulation can **shorten the development time of process packages, reduce the amount of experimental work, guide production, and predict the trend of 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 schemes can be comprehensively compared through simulation, thereby determining the optimal scheme. //Specific work to be carried out // 1. Determine the property measurement method based on the physical 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 aim is to make the model predictable, 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, perform simulation calculations (including regression of property data, analysis and calculation of heat exchangers, etc.). Analyze and correct any problems that are identified, and simultaneously conduct calculations and comparisons for various possible processes to determine the optimal solution. Once the optimal process is identified, further optimization of individual equipment is carried out ； 4. Match utility services (keep the specifications as minimal as possible while considering investment). Thus, the simulation work is essentially complete. I hope this casual treatment above 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 not be sufficient. 4 Once the PFD, PID, and equipment data sheets have been developed through accurate full-process simulation, a complete material flow diagram (PFD) can be obtained. Referencing the process patterns of typical unit equipment, taking into account the characteristics and requirements of the process, and involving the instrumentation team, the PID is developed together. The economic flow rate is determined based on the information regarding various flow streams shown on the PFD; pipe pressure drops are calculated, and then the pipe diameter is fixed. Considerations such as purging, catalyst heating/reduction or shutdown protection, and pre-sulfidization are taken into account according to the needs for startup and shutdown, along with the necessary lines for these operations. Design calculations are carried out for all equipment; for standardized equipment, detailed parameters and material selection principles are specified, while for custom-made equipment, dimensions, size, height, internal components, etc. are calculated. //The reactor // is determined based on a comprehensive consideration of various 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 // Include packed columns and tray columns; there are also columns that have both packing and trays within them. 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 plate/packing element. //Heat exchanger // Import the data from the process simulation into the heat exchanger calculation software to carry out the calculations. Generally, the verification mode in HTRI is used for calculations. In process simulation, the temperature difference between the hot and cold sides is usually maintained at ≥8°C; attempts are made to avoid temperature cross-over. Factors such as fouling heat resistance, the need for cleaning, 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 may be considered, as it is generally used in situations where the heat load is high and the temperature difference is small. 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 site—such as electricity prices, availability of surplus steam, feasibility of installing boilers or captive power plants, coal prices, and other factors—a comprehensive analysis is conducted to determine whether electric drive or steam drive should be adopted. When electric drive is used, the compressor generally requires a lower initial investment, occupies less space, and involves less work in operation/maintenance. However, when adjusted for the unit cost of the product, electricity is usually more expensive than steam. In the case of steam drive, generally speaking, the initial investment in compressors is high, they require a large amount of space, and entail substantial operation, inspection, and maintenance efforts. However, after calculating the unit cost of the products, 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 total condensation, extraction condensation, or backpressure operation (this needs to be taken into account within the overall plant steam balance). If the compressor employs total condensation or extraction condensation, it is also important to decide whether surface cooling should be achieved through water cooling or air cooling, as these two methods have different effects on the compressor’s steam consumption. //Separator // Based on the previous calculations, simply organize the completed equipment data sheet. //Storage tanks // Includes 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, product sealing, shift handover, etc.). //Other equipment // Non-standard equipment: provide detailed dimensions, types of internal components, detailed parameters, process parameters, etc ； For sizing equipment, detailed process parameters, process requirements, material selection principles, etc., should be specified. 5. Complete the design specifications, instrument specifications, interlock instructions, recommended equipment layout diagrams, etc. At this stage, 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. There must be a great team supporting it; this team comprises members from research and development, technology, engineering, production, etc. Two major manuals have been completed: the Analytical Testing Manual and the Operating Manual. The completion of these two manuals requires not only a thorough understanding of the processes involved, but also a large amount of experimental and pilot-scale data as support.