Chemical Process Safety

Chemical process safety focuses on preventing incidents and accidents during large scale manufacturing of chemicals and pharmaceuticals – in particular, the unintentional release of potentially dangerous materials and energy to the environment during a chemical reaction, or because of a runaway reaction.

In the chemical industry, process safety incidents occur for different reasons, including:

• missing information
• insufficient operator training
• technical defects
• human errors
• concatenation of unfortunate coincidences

Malfunctions, human errors, and lack of full understanding of the chemistry, including all possible side-reactions, of the process and its parameters are among the most frequent reasons for which incidents or accidents take place.

Identifying and understanding hazards and risks, along with thorough risk analysis, enable evaluation of the risk of triggering decompositions and prevent loss of control over the reaction.

Chemical process safety is part of a comprehensive safety assessment for scale-up and manufacturing and must therefore be regarded as part of company culture and policy. The guideline under which Chemical Process Safety falls is also known as "HSE" or "SHE", and is included in the directives of many regulatory bodies.

Chemical process safety uses a framework of different techniques, technologies, and models and requires an understanding of the desired and potentially undesirable reactions possible during the process. This includes the investigation of thermal events, heat transfer, mixing, mass transfer, and gas evolution, as well as stability of the starting material, he reaction mass, and the resulting products.

Thus, a number of different disciplines are employed to ensure chemical process safety.

The implementation of effective chemical process safety measures prevents incidents and accidents at pilot or manufacturing scale. Typically, products are developed under challenging timelines with small amounts of material, and under extreme conditions. Over the years, chemical processes have become more numerous, plants more complex, chemistry more ambitious and more toxic, and operating conditions more dangerous. For these reasons, and owing to the occurrence of serious accidents, regulatory bodies and society at large have become more safety-conscious. These trends have forced companies to improve general chemical process safety and develop concepts that ensure inherently safe chemical processes and manufacturing. An inherently safe design prevents chemical hazards rather than controlling them.

To ensure safe and compliant operation, a process and its risks must be clearly understood.

Thorough chemical process safety studies do not just prevent runaway reactions, but also plant damage or destruction, injury or loss of life, and/or environmental degradation or pollution.

The purpose of such studies is to gain an overview of all potential dangers, effects, and consequences. It includes disciplines such as product and process, personal, and environmental safety. Appropriate attention, management, and investigation must be given to each of the above disciplines to ensure the safe manufacturing of chemicals at large scale.

Chemical process safety uses a framework of different techniques, technologies, and models in which scientists investigate the chemical reaction, the properties of the solvents and chemicals used, and suitable process parameters.

Chemical reactions, their progress, and the formation of by-products and impurities are usually controlled by the manipulation of parameters such as temperature, pH, pressure, dosing rates, stirring, mixing, solvent type, catalyst, etc.

In process development, additional parameters, such as chemical reaction kinetics, maximum heat release, accumulation of heat and unreacted material, heat and mass transfer, viscosity changes, fouling, precipitation, or gas evolution must also be taken into account.

Consequently, analysis of the desired and potentially undesirable reaction(s) is most relevant for chemical process safety and is subject to thorough investigation.

Calorimetry is used to analyze the thermal behavior of chemical reactions. While reaction calorimetry is applied to investigate the desired reaction, differential scanning calorimetry (DSC) is typically used to study the undesired reaction. The secondary reaction is often a decomposition of the reaction mass or components therein leading to a runaway reaction in the worst case.

Reaction calorimeters provide thermal information, including heat flow profiles as a function of time or dosing, maximum heat release, thermal accumulation, accumulation of reactants, reaction enthalpy, and heat transfer coefficients. Investigations of chemical processes in reaction calorimeters also enable scientists to uncover dependencies of the reaction on stirring and mixing. The combination of information from a reaction calorimeter with that collected by thermal screening (e.g. with DSC) allows the derivation of safety protocols, such as the runaway graph or the criticality of a reaction.

The comprehensive information obtained from reaction calorimetry supports scientists in identifying and eliminating critical or non-scalable parameters, thus achieving a high level of chemical process safety.

In reaction calorimetry, a chemical process is studied with regard to the influence of reaction and process parameters on the progress, reaction rate, heat release depending on time or dosage, maximum heat release, accumulation influence of energy and reactant, or mass and heat transfer.

While running a chemical reaction under process-like conditions, the amount of energy released or absorbed is determined as a function of time and recorded together with other process data.

The RC1mx supports different methods to measure the heat of a reaction. These include, for example, the proven heat flow technique, in which heat transfer behavior as a function of time is determined by calibration of the heat transfer coefficient, or RTCal (a technique that measures and presents the heat flow online and in real-time).

Independent of the method used, custom algorithms ensure that the heat of reaction is measured accurately and precisely – independent of the reactor setup, and under all experimental conditions, including

• Isothermal temperature conditions
• Non-isothermal temperature conditions
• Addition of cold and hot reactants

For thorough chemical process safety studies, reaction calorimeters are used to obtain details of the investigated reaction, including the:

• Influence of changing mixing behavior
• Side or consecutive reactions
• Changing heat capacities
• Evaporation or gas evolution

Individually, or as an integrated chemical workstation, these tools provide critical support for better chemical process safety:

• Chemical Synthesis Reactors
  Automated synthesis workstations enable unattended experiments with precise control of reaction conditions and data collected from every experiment, day and night.
   

• Reaction Calorimeters
  Screening reactions at small scale, identifying non-scaleable conditions, exploring process parameters for scale-up, and assessing the risks and criticality of processes are all made possible by reaction calorimeters, supporting the development of safe, economical, and ecological processes.
  
  
• FTIR and Raman Spectrometers
  Continuous monitoring allows users to trend components over time for a 'molecular video' of the reaction. The real-time tracking and profiling of key reaction species as a function of reaction time enabled by spectrometers aids kinetic and mechanistic investigations.
  
  
• iC Software
  Transform experimental data into important process knowledge and integrate data streams for comprehensive understanding and data management. iC DataCenter captures all experimental data securely, and allows the preparation and sharing of data across an organization to help in building up institutional knowledge.

Use Dynochem modeling to ensure effective mixing and heat transfer when scaling-up reactions. Dynochem makes it easy to quickly compare lab, pilot and production scale reactors, and find the appropriate mixing parameters to safely speed reactor-to-reactor process transfer. With data provided by reaction calorimetry and Dynochem modeling, quickly ensure chemical process safety and performance across scales. 

Chemical process safety and related applications are referred to in many publications. Below are some highlights:

• Thirumalai Lakshminarasimhan, Predicting 24 and 8 h Adiabatic Decomposition Temperature for Low Temperature Reactions by Kinetic Fitting of Nonisothermal Heat Data from Reaction Calorimeter, Org. Process Res. Dev. 2014, 18, 315−320
• Kamala Jyotsna G, Srikanth S, Ratnaparkhi V, et al. Reaction calorimetry as a tool for thermal risk assessment and improvement of safe scalable chemical processes. Inorg Chem Ind J. 2017;12(1):110
  
• Darja Pecar and Andreja Gorsek, Saponification Reaction System: a Detailed Mass Transfer Coefficient Determination, Acta Chim. Slov. 2015, 62, 237–241
  
• Christopher W. Mitchell, Josiah D. Strawser, Alex Gottlieb, Michael H. Millonig, Frederick A. Hicks, and Charles D. Papageorgiou, Development of a Modeling-Based Strategy for the Safe and Effective Scale-up of Highly Energetic Hydrogenation Reactions, Org. Process Res. Dev. 2014, 18, 1828−1835
  
• Min Hua, Min Qi, Xuhai Pan, Wendi Yu, Lu Zhang, and Juncheng Jianga, Inherently Safer Design for Synthesis of 3-Methylpyridine-N-Oxide, Process Safety Progress, Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/prs.11952
  
• Alexandre M. Monteiro, Roy C. Flanagan, Process Safety Considerations for the Use of 1 M Borane Tetrahydrofuran Complex Under General Purpose Plant Conditions, Org. Process Res. Dev. 2017, 21, 241−246
  
• Jingyao Wang, Yanyan Huang, Benjamin A. Wilhite, Maria Papadaki, M. Sam Mannan, Toward the Identification of Intensified Reaction Conditions Using Response Surface Methodology: A Case Study on 3‑Methylpyridine N‑Oxide Synthesis, Industrial & Engineering Chemistry Research 2019 58 (15), 6093-6104