Seven stages of chemical technology from creativity to industrialization (Issue 58/100 in total)--MDI supporting project cases

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Seven stages of chemical technology from creativity to industrialization (Issue 58/100 in total) - Technology finalization: MDI supporting project cases Dear friends: Hello everyone! In the last issue, we talked about the final version review and document delivery of the technology package, and all the sixteen core tasks in the technical finalization stage were covered. Starting from this issue, two real project cases will be used to conclude the fourth phase. Today we will first talk about the MDI supporting project - a practical case of international process package docking. This case is different from the PPS and p-phenylenediamine projects mentioned earlier. PPS is an amplification of its own technology, p-phenylenediamine is an original innovation, and the MDI project faces how to digest, transform, and implement it under local conditions after obtaining a mature process package from a world-class chemical enterprise. This scenario is very common in the industry - the introduction of international technology and domestic engineering. Many companies have experienced this process. 1. Project background The MDI supporting project is the construction and renovation project of a large-scale chlor-alkali plant, which includes multiple main lines such as capacity improvement of the caustic soda plant, new chlorine drying and chlorine compression, new chlorine debromination unit, and energy-saving transformation. One of the core aspects of the project is to directly connect with a complete process package provided by a world-class chemical company. The other party has decades of industrial experience in the field of chlor-alkali and chlorine gas treatment. The technical depth and document standardization of the process package are among the first in the world. But for the project team, this is the first time to directly digest an international process package of this level, and it is also the first time to carry out engineering transformation according to the other party's standardized system. Technical attachments are the basis for much subsequent work. The other party's process package has a rigorous and detailed description of various process parameters, control indicators, and performance guarantee values. But it is precisely this kind of rigor that places high demands on the project team's digestion capabilities - you must understand the design intent behind each data and the safety logic behind each interlocking setting value in order to accurately translate the other party's standardized design into an engineering plan that adapts to local conditions. 2. “Translation” of technical attachments The first challenge in the docking of international technology packages is the interpretation and transformation of technical attachments. The other party's technical attachments were prepared in English, and the legal framework, standard specification system, and design habits adopted were somewhat different from those in China. For example, for pipe material grade, the other party uses the American standard system, which is different from the commonly used domestic standards in material code and allowable stress value. For example, for the calculation of the relief volume of the safety valve, the standard adopted by the other party is different from the processing logic of SHSG-052 in some details. Faced with these differences, what the project team needs to do is not to simply translate English into Chinese, but to understand the engineering logic behind the other party's standards, and then find equivalent or better solutions within the framework of local standards. This "translation" process is actually a process of recalculation and verification. A typical example is the determination of equipment design pressure. The other party's process package gave the design pressure of each piece of equipment, but the team could not copy it directly - because the value of the design pressure was related to local meteorological conditions, public engineering conditions, and the setting pressure setting of the safety valve. The team checked each other's calculations one by one and confirmed that the design basis was consistent before adopting it. ； Where there were differences, we recalculated and conducted technical communication with the other party. The rigor of the technical attachments played an important role in subsequent project advancement. Many potential disputes - the adjustment range of a certain operating parameter, the performance guarantee value of a certain piece of equipment - can be found in the technical attachments with clear agreements and basis. This also confirms the point emphasized in Issue 35: The technical attachment is the "constitution" of the process package preparation. If you spend time in the early stage to make it solid, the management cost in the later stage will be significantly reduced. 3. Conversion of PFD to Equipment Data Sheet One of the most worthwhile aspects of this international process package is the data integrity of PFD. When they received the other party's PFD, the team was quite convinced - the temperature, pressure, flow rate and composition of each stream of logistics were clearly marked, the operating conditions and design conditions of each piece of equipment were clearly distinguished, and the logic of each control loop had been initially expressed on the PFD. The data marked on the PFD can be found in the subsequent equipment data sheets and instrument data sheets. This discipline of "PFD is the only data source" is exactly the iron rule repeatedly emphasized in Issue 40. But completeness does not mean that it can be used directly. The other party's PFD was compiled based on the standardized design conditions of its own equipment. The settings of certain boundary conditions - such as the supply temperature of cooling water and the pressure level of steam - were not completely consistent with the actual local conditions. What the project team needs to do is to adapt the process parameters on the PFD to the local utility conditions. For example, the other party's heat exchanger is designed according to the local cooling water temperature in winter, and the heat transfer temperature difference is relatively small. The local cooling water temperature in summer is much higher than the other party's design basis. If the other party's heat exchanger data sheet is directly applied, the heat exchange area may not be enough in summer. The project team conducted a summer operating condition check on each heat exchanger involved in cooling water and made adjustments to the affected heat exchangers. The difficulty of this transformation lies not in the calculation of a single device, but in the systematic correlation. If you change the area of ​​a heat exchanger, it may affect the consumption of public works ； Changes in utility consumption may affect the design of supporting systems. Therefore, every modification must be re-marked on the PFD, and then all downstream documents—equipment data sheets, instrument data sheets, and utility consumption sheets—are updated item by item to ensure the consistency of the entire process package data. 4. Localization of interlocking logic International technology packages are usually more rigorous in interlocking design, with clear divisions between SIS and DCS, and clear requirements for the independence and redundant configuration of interlocking loops. But the localization of interlocking logic is more than just translating logic diagrams. The other party's interlock setting value is determined based on the operating experience and operating window of its own device. When applied to the local device, it needs to be re-verified based on the local operating conditions. A specific example is interlock protection for chlorine compressors. The surge control curve and interlock setting value of the compressor in the other party's technology package are based on the performance curve of the other party's own compressor. However, the compressors actually purchased for the project may come from different manufacturers, and the performance curves are not completely consistent with the other party's benchmark. The interlock setting value needs to be verified and confirmed by the compressor manufacturer and the process professional after the actual compressor model is determined. In addition, the SIL level of some interlocking loops also needs to be re-evaluated based on local risk acceptance standards. The other party's risk acceptance standards may differ from domestic standards or the owner's corporate standards. The project team organized independent HAZOP analysis and LOPA grading, and conducted localized verification and adjustment of the SIL level of each SIS interlocking loop to ensure that it was neither lower than the requirements of international standards nor over-designed, which would increase the risk of investment and mis-stopping. 5. Challenges of interface management In the docking of international technology packages, interface management is a link that is easily overlooked but can be very troublesome if not handled well. The other party's process package covers the scope of the core process equipment, but the public engineering facilities, raw material supply and product transportation outside the boundary area need to be designed by the project team. Every parameter on the boundary conditions table—temperature, pressure, flow, delivery method—must be agreed upon between the process contractor and the project team. A practical problem encountered during project execution is that the conveying pressure of a certain material in the boundary area of ​​the other party's process package is determined based on the characteristics of the pipeline system of the other party's own equipment. However, the pipe gallery layout of the local installation is different. The pipeline from the boundary area to the downstream equipment is longer and has greater resistance, and the required boundary pressure is higher. This requires a new agreement on the boundary condition table, and the other party confirms whether the process package can operate safely under a higher boundary pressure. At the same time, the project team checks the pipeline design and the endurance capacity of the downstream equipment. Dealing with such interface problems often requires multiple rounds of technical communication. But precisely because the interface conditions were clarified one by one in the technical attachments and boundary condition tables in the early stage, the communication was always well-founded and there was no mutual dispute. 6. Several points of experience Looking back at the international process package docking process of the MDI project, there are a few points of deep experience. First, the rigor of international craft packages is worth learning from. From the data integrity of the PFD, to the independence of the interlocking logic, to the orderliness of the technical accessories, the other party's approach to many details reflects the concept of "risk fronting" - thinking clearly about the issues that should be considered at the drawing stage. This kind of engineering discipline is in sharp contrast to the habit of "drawing first and then revising" in the development of proprietary technology. Later, we implemented the iron rule of "PFD is the only data source" in our own projects, largely based on the experience of this project. Second, international craft kits are not something you can just buy and use. Differences in standard systems, differences in public engineering conditions, and differences in operating habits all determine that they cannot be directly applied. The process of digesting international technology packages is essentially a process of recalculation, reverification, and reexpression. Digest well, the international craft package is a good learning object ； If you have poor digestion, you may not be able to adapt to the local conditions if you try to use something foreign. Third, interface management is key to international project cooperation. Boundary condition table, technical attachments, performance guarantee values ​​- these interface documents are the common language for communication between both parties. In international cooperation, the root cause of many problems is not technical differences, but different understandings of the same thing by both parties. If the interface conditions are clearly written, signed, and approved by both parties, the subsequent communication efficiency and problem solving speed will be much better. Next Issue Preview Issue 59: Para-phenylenediamine case - the process package preparation of original innovative technology MDI project is the digestion and transformation of the introduction of internationally mature process packages. The next issue will talk about a completely different type of case - p-phenylenediamine continuous flow process. This is a set of processes that are completely independently developed and have no industrial precedent to refer to. How to establish technical standards from scratch for the process package and how to make design decisions with limited data. This case is very complementary to the MDI case. One is the digestion and absorption of mature standards, and the other is the establishment of standards from blanks. Expand next issue.