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The seven stages of chemical engineering technology from concept to industrialization (Issue 67/100) — Engineering transformation: Special topics on fire protection, environmental protection, and occupational health. Dear readers: Hello! In the previous issue, we discussed the special section on safety facility design; it is the only one among the four special sections for chemical projects that still needs to be submitted to the relevant government authorities for review. In this issue, we will discuss three other special topics: fire protection design, environmental protection facility design, and occupational health and safety facility design. Although these three specialized aspects are no longer submitted separately for review by the relevant government authorities, fire safety design reviews have been integrated into the construction drawing reviews in some areas, and environmental protection and occupational health inspections have been replaced by self-inspections carried out by the project owners – yet these changes in the review processes do not diminish their importance in engineering design. Any oversight in fire protection design can directly lead to an expansion of a fire accident ； Lack of environmental protection facilities may lead to reduced production or even shutdowns ； The lack of occupational health protection can harm the health of operators over the long term of operation. These three special sections together constitute the device’s technical commitments in terms of fire protection, environmental protection, and occupational health; each of them requires a solid design foundation and reliable technical solutions. I. Special Section on Fire Protection Design The basis for preparing the special section on fire protection design is primarily the \"Code for Fire Protection Design of Buildings\" and the \"Technical Code for Fire Water Supply and Fire Hydrant Systems\". After the fire safety inspection function was transferred to the housing and construction department, for chemical projects that fall under the category of \"special construction projects\", the fire safety design documents must be submitted to this department for review ； For other construction projects, a system of random inspections for record-keeping is implemented, with fire protection design documents being part of the review of construction drawings. The core of the fire protection design section consists of three things: fire hazard classification, fire compartmentation, and calculation of fire water volume. These three things are the foundation of all fire protection design; one mistake will lead to errors in everything that follows. Fire hazard classification is the starting point for all fire protection design. Based on the properties of the materials and the operating conditions, each building and each area of the facility is classified according to its fire hazard level: Class A, Class B, Class C, Class D, and Class E. The classification is based on characteristic data such as the flash point, lower explosive limit, and operating temperature of flammable liquids and gases in the materials, which were already compiled in the material property table in Issue 36. The classification result directly determines all subsequent design parameters such as fire separation distances, fire resistance ratings, and fire-fighting water volume. Areas containing flammable liquids with a flash point below 28 degrees are typically classified as Class A, requiring the highest standards in terms of fire separation distances and fire resistance ratings ； Flammability range of 28 to 60 degrees corresponds to Category B ； Above 60 degrees is Category C ； Non-combustible materials belong to Class D and E. The fire separation distances for various categories are determined in accordance with the relevant specifications, while the fire separation distance between adjacent buildings shall meet the requirements of the higher category. Fire compartmentation is a scheme for isolating and protecting the space of equipment after determining the fire hazard category. The allowable area for each fire compartment depends on the fire category and fire resistance rating. For single-story Class A factories with a fire resistance rating of Grade 1, the maximum allowable area per fire compartment is usually 4,000 square meters, while for Grade 2 it is 3,000 square meters. For Class C factories with a fire resistance rating of Grade 1, a single floor can cover an area of 8,000 to 12,000 square meters. The boundaries of fire compartments are established using facilities such as firewalls, fire doors, and fire curtains, with the aim of containing fires within a specific area and preventing them from spreading. The fire resistance rating of a firewall is usually not less than 3 to 4 hours, and the doors installed in such firewalls must be Class A fire doors. Pipes and cable trays that pass through fire compartments must be fire-sealed – this detail is often indicated by a single symbol on the design drawings, but it is an essential item to check during construction and inspection. The calculation of fire water volume is a part of the fire protection section where errors are prone to occur. The fire-fighting water volume is not a figure determined arbitrarily; it is calculated item by item based on parameters such as the type of fire, the scale of the installation, the area of the fire compartments, and the simultaneous use coefficient for fire-fighting systems. It includes the sum of various water consumption amounts, such as those for outdoor fire hydrants, indoor fire hydrants, automatic sprinkler systems, and fire monitors. Taking outdoor fire hydrants as an example, Class A installations typically require 30 to 45 liters per second, while Class C installations require 20 to 30 liters per second; the specific values are determined based on the volume of the installation and its fire resistance rating. The capacity of the fire pump room and the effective volume of the fire water tank must meet the requirements of the maximum fire water demand and the longest possible duration of a fire. The fire duration for chemical plant facilities is typically taken as 3 hours. The effective volume of a fire water tank is equal to the amount of fire-fighting water required multiplied by the duration of the fire, with a certain safety margin taken into account. The fire pump room should meet the power supply requirements for Class I loads – one source of mains power supplemented by a diesel generator as a backup, or two separate sources of mains power. At the most unfavorable fire hydrant location, the specified pressure and flow rate must be maintained—the dynamic pressure at the outlet of the fire hydrant should not be less than 0.35 MPa, and the range of the fire monitor under normal operating conditions should cover all equipment within the protected area. The fire protection piping network should be arranged in a circular pattern, so that maintenance of any section of the pipes does not affect the fire water supply in other areas. Fire protection design also includes the selection of automatic fire alarm systems and fire extinguishing facilities. For Class A and Class B installations, a fixed foam fire extinguishing system or a dry powder fire extinguishing system may also be required. Large tank farms typically are equipped with fixed foam fire extinguishing systems and fire monitors; the supply rate and duration of the foam mixture are determined based on the type of tanks and the substances stored in them. The fire control room should be located upwind or to the side of the installation, to ensure that personnel can reach it and operate it safely in case of a fire. II. Special Section on the Design of Environmental Protection Facilities: The special section regarding the design of environmental protection facilities no longer needs to be submitted to the environmental protection authorities for review; the completion inspection of such facilities is now carried out by the construction unit itself. But the responsibility becomes even greater—self-inspection means that the company bears full responsibility for the design, construction, and operational outcomes of its environmental protection facilities. Environmental protection facilities must be designed, constructed, and put into use simultaneously with the main project – the \"three simultaneities\" principle is an unbreakable legal requirement. The preparation of the environmental protection section is based on the material balance of the process package and the waste discharge data from the PFD. The emissions and composition of wastewater, waste gas, and solid waste must be traced back to their sources in the PFD; figures cannot appear out of nowhere. The environmental impact assessment report and the corresponding approval documents serve as the legal basis for the environmental protection section; every requirement specified in the approval documents must be addressed through corresponding design solutions within this section. Wastewater treatment is one of the core topics in environmental protection. What are the sources of wastewater? Process wastewater, cleaning wastewater, cooling wastewater, initial rainwater, and domestic sewage. What are the volume and quality parameters for each type of wastewater—COD, ammonia nitrogen, pH, and characteristic pollutants. High-concentration organic wastewater may need to undergo advanced oxidation or biochemical pretreatment first, before being mixed with low-concentration wastewater and fed into the biochemical treatment system. If saline wastewater is introduced directly into a biochemical system, it will inhibit microbial activity; therefore, MVR evaporation crystallization for desalination may be required first. Wastewater containing heavy metals or high levels of toxicity must be pre-treated to a certain standard before it can be fed into the comprehensive treatment system. The selection of wastewater treatment processes requires consideration of pilot plant data or operational experience from similar facilities, to ensure that the treatment efficiency can consistently meet the discharge standards. Waste gas treatment is also a key focus. Sources of organized exhaust emissions include reactor off-gases, non-condensable gases from distillation columns, vent gases from storage tanks, and drying exhaust gases. It is necessary to understand the composition and emission characteristics of each type of waste gas – whether it is emitted continuously or intermittently, and what characteristic pollutants it contains – VOCs, acidic gases, particulate matter. Whether the VOC emissions meet the current emission standards, and whether it is necessary to install an RTO regenerative thermal oxidizer or activated carbon adsorption units. If high-concentration chlorine-containing waste gas enters an RTO directly, dioxins may be generated; therefore, special pretreatment is required or an incineration process suitable for treating chlorine-containing waste gas must be used. The control of unorganized emissions is equally important—emissions from tank vent valves, volatilization during loading and unloading, and leaks at sampling points need to be controlled through measures such as sealed collection, nitrogen blanketing, and vapor recovery. Waste disposal requires a distinction between hazardous waste and general solid waste. Temporary storage sites for hazardous waste must meet regulatory requirements—ground impermeabilization, drainage ditches, collection ponds, and protection against rain and sunlight. When entrusting a qualified entity for disposal, the hazardous waste transfer form and disposal contract must be specified in a separate section. General solid waste can be comprehensively utilized or landfilled, but the disposal method and destination must also be clearly specified. The environmental protection section also needs to outline emergency measures for environmental risks. In the event of an accident, how are fire-fighting wastewater and spilled materials collected and contained? Is an emergency containment tank in place, and does its capacity suffice to hold the combined volume of the maximum possible spillage and the amount of water used for fire fighting? Check whether the rainwater and wastewater switching valve is in place, and ensure that initial rainwater is collected and treated to prevent it from being discharged untreated. III. Special Section on the Design of Occupational Health Protection Facilities: The design of such facilities no longer requires government approval; instead, the construction entity is responsible for organizing expert reviews and preparing a written report for record-keeping. However, the primary responsibility of employers under the Law on the Prevention and Control of Occupational Diseases remains unchanged – what has been abolished is administrative approval, not legal liability. The comments from the review experts still must be addressed and implemented item by item. The focus of the special section on occupational health is the cumulative effects of long-term low-dose exposure. Operators work on the equipment for eight hours per day; the core question that needs to be answered in the section on occupational health is whether the daily and weekly exposure levels to these harmful factors exceed safe limits as a result of such prolonged exposure. The first step in preparing a special section on occupational health is the identification of occupational disease hazards. Which positions are exposed to dust hazards – the material feeding stations, packaging stations, and points where solid materials are transported. Which positions are at risk of exposure to toxic gases—sampling ports, pump seals, flange connections, and valve packings. Which areas have excessive noise levels – compressor rooms, fan rooms, and high-pressure pump areas. Which positions involve working in high or low temperatures – reactor operation platforms, refrigeration rooms. The design of protective measures follows a priority order. The top priority is process improvement – can toxic materials be replaced with non-toxic or low-toxic materials? The second priority is engineering controls – whether it is possible to carry out operations in enclosed environments, to improve ventilation, to set up isolated work areas, and to use automated systems to reduce human contact. The third priority is management measures—rotational shift systems, limiting exposure time, and regular health checks. Last are the personal protective equipment – gas masks, protective clothing, and gloves. During the process package and basic design phases, process engineers should fully incorporate the findings and recommendations of occupational health assessments when carrying out automation design and control room layout, considering from the outset how to reduce the frequency of operator contact and exposure risks through encapsulation and automation methods. Sampling ports, discharge ports, and feeding ports – these points where manual operations take place – are areas that require special attention in terms of occupational health protection. Although closed sampling systems and automated discharge devices involve additional investment, they can significantly reduce the exposure risks for operators. The special section on occupational health also requires the design of emergency rescue facilities. Eye wash stations, emergency shower units – installed in areas where chemical burns may occur, such as acid and alkali storage areas and chemical loading/unloading areas. First-aid kits, chemical protective suits – stored in the control room or safety station. Toxic gas detection alarm – installed in areas where leaks may occur; the alarm signal is sent simultaneously to the control room as well as to the on-site audible and visual alarms. The location, quantity, and specifications of emergency rescue facilities are listed in detail in a separate section. IV. Commonalities and connections among the three specialized sections: The three sections on fire protection, environmental protection, and occupational health each have their own focus, but they are interconnected with the section on safety facility design. The calculation of fire-fighting water volume is the core of the fire protection section, whereas the collection and disposal of fire-fighting water fall under the scope of the environmental protection section. Alarm and interlock systems for toxic gas leaks are the focus of the safety section, whereas the acute hazards to operators and assessments of long-term exposure after a leak are covered in the occupational health section. The discharge volume and discharge destination of a safety valve are calculated and determined in the safety section, but the treatment measures for the discharged gases, if they are VOCs or malodorous gases, are covered in the environmental protection section. The four special sections were prepared independently, but they all draw from the same data sources: the material property tables in the process package, the flow and operating conditions specified in the PFD, and the equipment parameters in the equipment data sheets. During compilation, the persons in charge of each section must regularly compare the data to ensure that the same values are used across all four sections; for example, the capacity of a given storage tank and the setting pressure of its safety valve should not have different values in the safety section and the fire protection section. V. Some Insights After compiling several special reports, there are a few insights that I would like to share. First, a monograph is not “written” but “computed”. The amount of water required for firefighting is not determined arbitrarily, but is calculated item by item based on the type of fire, the size of the installation, and the area of the fire compartment. The discharge volume of the safety valve is not estimated based on experience, but is calculated individually for each overpressure condition. The waste discharge data are not copied from the environmental impact assessment report, but are derived point by point from the material balance in the PFD. Data has its sources, and calculations are based on solid foundations; only then can a specialized article have technical credibility. Second, the timing of compiling a special issue is very important. Although several special studies were prepared during the basic design phase, the large amount of basic data required came from the PFDs and equipment data sheets in the process package. If the data from the process package phase is incomplete—with missing waste emission points, absent material safety data, or ambiguous equipment operating conditions—it will be necessary to either collect the missing data later or use conservative assumptions in the dedicated report. With too many conservative assumptions, the safety margin and investment costs increase. Third, the review of special reports cannot be a mere formality. External review of the safety section is mandatory, and in some areas, the review of the fire protection section has also been incorporated into the construction drawing review. Although environmental protection and occupational health aspects are now subject to self-inspection, internal reviews must still be thorough. The safe operation of a chemical processing plant relies precisely on these protective layers, which are carefully reviewed and verified during the design phase. Any vulnerability in the protective layer identified during the special review was addressed on the drawings, rather than being remedied in hindsight after an accident occurred. Preview for the next issue: Issue 68 – Energy Conservation Assessment and Soil and Water Conservation. The four special topics have been covered. In the next issue, we will discuss the other two tasks that need to be carried out simultaneously during the project implementation phase: energy efficiency assessment and soil and water conservation. How to prepare a performance evaluation report, how to incorporate energy-saving measures into equipment selection, what are the key elements of a water conservation plan, and how do these specialized tasks connect with the design of the main project. To be continued in the next issue.