August 2024

Special Focus: Plant Safety and Environment

Utilizing pilot plant operations for new chemical process technology development: A roadmap to scale up success and commercial plant safety

To demonstrate a new chemical process technology (flowsheet, raw materials, product) or improve an existing one, pilot plants are designed and operated at a scale between laboratory benchtop and commercial scale—often with specific goals for operability, product quality, economics and process safety. Identifying where potential safety, technical risks or uncertainties may occur is always a key goal in evaluating a new process.

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M. NUNLEY, B. CLARK and G. PHILLIPS, AVN Corp., South Charleston, West Virginia 

Developing a new chemical process technology is often a long, difficult and complex process. Starting with a simple process design helps eliminate unnecessary complexity that may introduce additional risk and uncertainty in both the scale-up and process safety aspects of the project. Safety and technology reviews play a key role in the mitigation of these risks. However, reviews that are too simple may overlook possible failure modes or consequences. A systematic approach to define the project’s scope, goals, known variables and potential unknowns is essential to keep these reviews effective and focused. 

Identify potential safety issues in a pilot plant facility. To demonstrate a new chemical process technology (flowsheet, raw materials, product) or improve an existing one, pilot plants are designed and operated at a scale between laboratory benchtop and commercial scale—often with specific goals for operability, product quality, economics and process safety. Identifying where potential safety, technical risks or uncertainties may occur is always a key goal in evaluating a new process. A thorough literature review covering chemistry, process, product, unit operations and chemical hazards is always recommended prior to any pilot plant study. However, often there is limited information available—this is usually the key reason for conducting a pilot plant study. Without a basic understanding of the technology in advance, it is difficult to evaluate the design for technical performance or safety gaps, and one must rely on experience and leveraging learnings from similar processes or products (FIG. 1). 

FIG. 1. Process complexity can be due to the chemistry, the number of steps, the material handling, and layout needs and automation, among others.  

Working in a pilot plant research environment requires a diverse technology team (chemists, engineers, operators) that includes members with a broad knowledge and experience across many different process technologies and functions (design, improvement, operations, analytical), as well as subject matter experts with a more narrow but deeper focus in areas that are key to the project’s goals and success (e.g., separation, reaction engineering, mixing, heat transfer) and to ensure the identification and mitigation of all technical and safety risks. The team should not only identify and mitigate known risks, but they should also be on the lookout for unknown risks.  

Pilot plant process safety is improved with a thorough evaluation and understanding of each step in the operation and the expected/desired outcome. This awareness is required throughout all aspects of the design, including construction, commissioning, operations and maintenance. The process of evaluating a system for safety should identify the objectives and systematically develop the scope with increasing sophistication until the details are clearly presented.  

Understand project goals and objectives. At the beginning of every project, the team should define the project scope and specific goals (e.g., technology development, demonstration, validation, market development or improvement). This formulates the basis of the testing and helps identify the potential for and consequences of known and unknown variables.  

In assessing any new process, it is important to know what can go wrong. When studying a new reaction, product or route to an existing product, the team should explore not only the desired chemical reactions, but also consider other possible or unexpected byproduct reactions. Even if the project involves only mixing or separation operations, unexpected reactions (heat release, byproduct formation) must also be considered as these may impact safety or product quality. In the case of safety, look beyond the intended scope in a “What if?” approach, and search for unintended conditions that could have major consequences.  

Develop early project and technology definition documents. Next, the team should identify each step of the process that is necessary to achieve the defined objectives and what unit operations, operating conditions and physical/chemical changes are involved in each stage. The scope of a project is defined incrementally, starting with simple flow diagrams and eventually leading to a complete and detailed picture of the process [process flow diagrams (PFDs), piping and instrument diagrams (P&IDs)]. These documents are key to defining the safe operating envelope of the process:   

1. Block flow diagram (BFD): A simple BFD shows the basic processing steps and material flow. This simplifies early process reviews so that broad and basic issues—such as mixing, recycle and reactivity issues—can be identified.  
2. Material and energy balances: These are used as the design basis for the project and operating conditions at the pilot plant scale. The balances ensure the system design encompasses all necessary equipment to reach and maintain operating conditions, including normal operation, turndown, maximum operating conditions and any potential upset conditions at that proposed scale. For example, an exothermic reaction that might be easily controlled on a laboratory scale can be much more difficult to control and could possibly generate a runaway reaction at a pilot plant or larger scale.  
3. PFDs: These diagrams show major and minor equipment, critical valves, major flow streams and basic process controls. PFDs are like a roadmap for the process and communicate the necessary equipment and controls while simplifying the process essentials for equipmnent sizing and outlining operational procedures. PFDs typically include the material and energy balance in tablular form and referenced to equipment item and flow stream numbers to make sizing decisions easy to follow. 
4. P&IDs: P&IDs are likely the most important documents. They are created early in the process, updated often and consistently maintained. P&IDS detail all equipment, valves, piping, controls and interlocks in the process, and must be kept evergreen as the project changes through conception, improvements, modifications and corrections. In a development-focused project, P&IDs can change very frequently. The project and support staff (drafting) must be prepared to support this high frequency of change. P&IDs serve as a completed vision of the operating system and are typically used as the basis for construction in a pilot setting. Layout and operating notes should be incorporated into these drawings to ensure that key design or operating requirements are clearly communicated, such as equipment elevation and piping free drain/self-venting requirements, key operating valves, etc. All design and development activities should use the most up-to-date P&IDs to avoid miscommunication and potential safety issues. 

Write operating procedures and an operations strategy. Written operating and maintenance procedures are critical to define potential safety and process risks. It is imperative that the development of initial and improved operating procedures actively involves engineers, operators, maintenance and control system personnel.  

Operations strategy. An operations strategy details the intended plans for operations and maintenance, and includes operator, maintenance and control system staffing support; a planned operating schedule (hours/day, days/week, shift schedule); target reliability, production and onstream time goals; operating schedule; batch vs. continuous operation; attended vs. unattended operation; equipment sparing philosophy; the need for isolation, vent and drain valves for maintenance; sample points; and basic interlocks to protect equipment (reliability, property loss) and ensure process safety.  

Operating procedures. These are typically written in conjunction with the development of P&IDs and the controls plan. Operating procedures must fully encompass the scope of the process and the necessary equipment, instruments and controls, as well as the mode of operation: startup, normal operation, shutdown, upsets, emergency response, preparation for maintenance, short- and long-term outages, and any special operating cases such as catalyst regeneration. 

Sampling plans. These include a detailed description of the samples that are needed, frequency, volume, type of sample (gas or liquid), analytical method and target (intermediate or final product specification). The plan is used to develop and define sample and analytical procedures, personal protective equipment (PPE) and analytical support needs (laboratory equipment and staffing requirements).  

Controls plans. These include a detailed description of the controls that will be used in automation. This document explains how the control plan is implemented and what level of safety interlock systems are needed.  

Process hazard analysis (PHA). A PHA is a disciplined approach to identifying known and potential hazards and the specific risk mitigation requirements to eliminate or minimize these hazards. The risk mitigations defined are documented and may be categorized as critical design requirements depending on the level of risk. Ideally, a list of the known unknowns is outlined for discovery during the development effort so that the unknowns can become understood.  

It is critical that a team with members who have different perspectives and knowledge work together to generate and protect against a comprehensive list of scenarios. This can be a difficult task because new technologies—by definition—will have limited prior data available to use in these studies (e.g., reactive chemistry). However, the team can often leverage information from similar known systems (e.g., distillation, similar chemistry).  

A thorough hazard review will identify the process hazards, risks and the level of safety interlock independence required for risk mitgation. This analysis is typically conducted after PFDs, operating procedures and P&IDs are available and well before procurement and construction in case a major design change is required. It is recommended to start these reviews early and hold milestone reviews throughout the project as the design progresses.  

Plan for changes. It is important to remember that validating knowns is often the purpose of piloting. Identifying and defining unknowns and how they impact the project are just as important and depend on the awareness and capability of the pilot plant team. Identifying, understanding and mitigating unknowns help the team minimize the risk of technical failures and safety incidents. As new process understandings come to light, plans and experimental designs may need to be changed. A daily review process with the pilot plant team (operations, engineering, maintenance, analytical, control systems, technical experts) helps identify new learnings and manage expectations for the pilot plant development process. All learnings, improvements and changes must be documented and shared immediately across all functions working on the project. 

Define equipment and piping specifications. After reviewing the process for design and construction issues, the equipment, piping and tubing must be selected. Design specifications for equipment must consider PHA requirements and evaluate possible upsets such as a runaway reaction, plugging, fouling or loss of control. Equipment sizing and specification should be conservative for target capacity (appropriate design margin) and operating conditions (maximum expected operating temperature and pressure) and result in a process that can be controlled safely and reliably.  

Equipment reliability is always a key consideration. It is important to identify and design for possible failures (e.g., seized pump head, loss of utility, instrument failure, plugging), and determine if additional measures could make it safer if the failures occur, such as spare equipment, proactive maintenance or shutdown interlocks. 

Materials for piping, tubing and valve wetted parts (including elastomers) must be compatible with the process at expected and extreme high- and low-operating temperatures, pressures and compositions, including skin temperatures of contact heaters (heating mantles/heat tape) and chiller temperatures (especially cryogenic).  

If compatibility information cannot be found for the concentrations and operating conditions of interest, a simple experiment can be done by contacting the metal or elastomer with the chemicals at those conditions for an appropriate time period and confirming if there have been adverse effects to the material (e.g., pitting, embrittlement, dissolution).  

Material selection can also be difficult if the chemistry results in byproducts that are unexpected and can attack wetted parts (FIG. 2). The pipe specification break location (valve) often requires highly specialized alloys or polymers to allow for compatibility with uniquely different chemicals as they are being mixed.  

FIG. 2. Fouling, plugging and unexpected material phases should be considered for equipment reliability. 

Develop the layout for operations and maintenance. Once the process and operating needs have been identified, the next task is to lay out the equipment and piping for construction and operation (FIG. 3). The layout need not include every detail, but not considering the location for a piece of equipment or critical valve can lead to issues as the project proceeds. Improper spacing for valves, insulation or maintenance can require major rework and cause delays and cost increases. Safety needs for material handling or maintenance are the most common reasons for rework. The team should also consider the placement of equipment valves and piping for maintenance (e.g., venting/free drain requirements), the creation of low points (liquid traps), the consequences of unintended gravity flow, and the location of pressure and level transmitters and how they might impact operations and maintenance. 

FIG. 3. The layout should help make the process easy to operate by keeping the piping clearly labeled and easy to follow, easy-to-reach valving, and unobstructed equipment for ease of maintenance and troubleshooting. 

Identify critical operating tasks. A list of the daily, weekly and other critical operating and maintenance tasks that are required of operators is key to ensuring that these tasks are completed at the proper frequency and that correct PPE (proper gloves, chemical resistant suits, breathing air) is on-hand and available when needed (FIG. 4). Tasks can include preventative maintenance, inspections, cleaning, verification of quenching/inhibitor solution activity, catalysts and material inventory of chemicals (e.g., inhibitors, additives, cylinder gases, raw materials), PPE and other consumable items or items with a fixed shelf life. 

FIG. 4. PPE appropriate to the task is essential to avoid accidental exposure.  

Pre-startup safety review (PSSR). After the system has been constructed and prior to the initial startup, the project team and appropriate experts (safety focal point, chemists, separations, mechanical and maintenance) must review the process for completeness and any additional safety concerns. It is important to have an independent reviewer as part of the PSSR review team to provide an unbiased opinion for safety, technology and operating concerns.  

While it may be best to examine the process as separate unit operations or subsystems to simplify the review, it is also important to look at all interfaces—both internal and external—as these are typical points of failure or miscommunication. It is also important to review the process as a whole to identify how the process will actually operate and to determine if an upset in one part of the process might cause an issue upstream or downstream. These knock-on effects could affect utilities, storage or waste disposal, and may impact the project or process outside the project. 

Identify and review all potential safety issues and impacts. A PSSR checklist with specific questions helps to ensure the completeness of the design, construction and operational readiness, and prevents the PSSR team from moving too fast and missing important safety concerns or risks. Categories may include but are not limited to: 

• Facilities design and construction: Equipment and piping layout and support, elevated work requirements, safe egress and adequate ventilation. 

• Valve and piping: Correct materials of construction of wetted parts, specifications such as pressure and temperature rating, line size and types of piping and tubing connections (e.g., welded vs. flanged vs. tubing based on the operating conditions and chemicals of the process).  

• Equipment: Pressure/temperature rating, connections (flanged vs. welded vs. tubing), materials of construction of wetted parts, testing, grounding, support, spares, thermal and mechanical guards, and labeling.  
• Instrument and electrical: Safety interlock design (initiators, actions), valve failure position, verification of initiators and actions testing, bypasses, interlocks, labeling, and integration with the facilities’ systems such as hood ventilation, and flare or thermal oxidizer vent handling (FIG. 5).  
• Operating (digital control system) and analytical computers and software: Operator interfaces and workstations, testing, training, documentation and proper information technology (IT) support. 

• Operations: Procedures, training, sampling plan and procedures, the need and location of vents and drains and preparation of maintenance (washing/drying), labeling, hazard communication, valve and equipment location for safety and ease of access for operations.  

• Maintenance: Cleaning (washing, steaming, decontamination and waste disposal), isolation, lifting, access and training. 

• Safety systems: Relief devices, fire protection, personnel safety and buildings safety: 

• • Occupational health and industrial hygiene 

• • Environmental protection 

• • PPE 

• • Elevated work and fall protection 

• • Glass handling best practices. 

• Emergency response and training: Exposure to hazardous chemicals, rescue personnel and equipment required, symptoms and treatment, fires and other process emergencies. 

FIG. 5. Electrical wiring failure under insulation resulted in loss of heating and a potential fire hazard.  

These reviews should be conducted with a balance between structured questions and checklists to avoid missing issues common to every project, and brainstorming or “out-of-the-box” thinking sessions with a focus on the process and a “what can go wrong?” mindset.  

Find the operational unknowns during commissioning. Commissioning is a key opportunity to find operational unknowns before operation at target conditions with the actual chemicals of interest. When commissioning a pilot plant for the first time, it is a best practice to first test with water or a similar but safer surrogate chemical (e.g., a simple alcohol) in an environment that is simple, safe and constrained. These tests include a check of instrumentation, pipe and equipment pressure or vacuum testing, control logic, heating and cooling capabilities (FIG. 6), and interlock functional tests, and they provide valuable experience in defining the safe operations of the process. A process test with water can uncover unexpected results that could ultimately result in a safety incident. Surrogate chemicals that replicate desired operating conditions—but limit the process exposure to more hazardous chemicals—can also be useful in validating expected performance. 

FIG. 6. Verification of adequate heating in equipment commissioning using infrared photography. 

Manage change and new learnings before and after startup. Prior to beginning operations, all P&ID documentation changes should be completed in, at least, draft form for all parties of the team to refer to for normal troubleshooting. Pilot plants are operated to study or validate a new process technology or improve an existing process. Experimentation and continual changes during the pilot plant project are both expected and normal. This higher frequency of change and experimental nature differentiates the safety needs of operating a pilot plant from a demonstrated commercial process and demands updated documentation.  

Once the pilot plant is operational, the team must maintain focus on the safety issues and operating procedures, conditions and mitigations identified during the prior reviews. This focus is needed to identify any changes that are outside the previously defined safe operating envelope, known as process creep. Examples include: new operating conditions; changes in the experimental plan, flowsheet (order or new unit operation), equipment, valve, piping or instrument design related to temperature, pressure and materials; and changes in the specifications or source of raw materials and additives or inhibitors. Even simple changes can have significant consequences for safety, quality, technology and operability, all of which impact project success. 

As the process, procedures or objectives change, the pilot team must review the implications of the change. The team must be prepared to conduct appropriate breadth and depth process technology, operations and safety reviews as often as necessary to ensure all design changes and new learnings are incorporated into the design documentation. All review findings must also be clearly communicated across the team as quickly as possible. Keeping the technology well documented and the safe operating envelope updated is critical for safe operation and the efficient completion of the development effort.  

Managing process technology and safety in a pilot plant or commercial facility is highly dependent on understanding the process—both knowns and potential unknowns. Breaking the process down into simple steps, looking at interfaces and the integrated facility as a whole, while working with a team that has a diverse knowledge and experience base, makes it easier to identify potential problem areas in advance. When potential issues or risks (unknowns) are uncovered, the appropriate actions to mitigate these issues and risks to limit adverse consequences become clear.  

Pilot plant testing and facilities. When selecting a partner for outsourcing pilot plant development, it is important they have the appropriate facilities and resources (skills, experience) to safely test and develop new chemicals and processes. The ideal partner will have the process knowledge to understand scale-up needs and laboratories that can accommodate experimentation and scale-up work with an emphasis on safety. 

The authors’ company has an experienced technical staff with expertise in operations, design, construction, process development, separations, mixing, heat transfer, solids handling, custom glass fabrication and chemistry. The company works with both laboratory and pilot plant scale chemical processes. Dedicated pilot plant facilities are equipped with enhanced features such as single and multi-level, large scale cells with high volume turnover ventilation, reinforced walls and roof with directional relief for overpressure and blast protection, common utilities, waste system management, process control systems, advanced laboratory support for experimental needs, and online and offline analytics. 

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