A review of estimation methods for flash points and flammability limits

Abstract

INTRODUCTIONFlash point measurements of various types are used as one measure of the flammability of liquid materials. The flash point is also related to the lower flammability limit, which is the minimum content of the combustible in a combustible-air mixture that will propagate flame [1]. Many manufacturing processes involve flammable chemicals; therefore, flash points and flammability limits are essential to maximize safety in process design and operational procedures.Flammability is an important factor in the development of safe practices for handling and storage of liquid mixtures. Regulatory authorities use flash point determinations made from small-scale test apparatus to classify flammable and combustible liquids. These determinations are based mainly on the use of the closed cup flash point temperature as the key property for classifying liquids according to their degree of flammability. Based on these classifications, regulators then specify or provide guidance on the appropriate methods for transporting, handling, packaging, storing, dispensing, and protecting these materials [2]. Also, federal regulations require that the mixture flash point be provided as part of materials safety data information.Industry works with mixtures under different conditions of temperature, pressure, and oxygen concentrations according to the process involved. The flash point can be used to determine the level of risk in different stages of a process because it is the temperature at which sufficient vapor is generated to bring the concentration of flammable vapor above the lower flammability limit. One question that must be answered to ensure a safe level of operation in a certain process is "What is the minimum oxygen concentration requirement for flame propagation?" Or, in terms more directly applicable to process operations, "What is the minimum amount of inerts required to prevent flame propagation?"The quantity of air that is required to decrease the combustible vapor concentration to a safe level in a particular process carried out at a specific temperature should be based on flammability measurements at that temperature.Knowledge of flammable limits at elevated temperatures and pressures is needed for safe and economical operation of some chemical processes. This information may be needed in order to start up a reactor without passing through a flammable range, to operate the reactor safely and economically, or to store or ship the product safely [3].Flash points are available for most pure liquids, but the information for mixtures is very limited and is usually at ambient pressures. For mixtures of flammable liquids, or more importantly, liquid mixtures containing both flammable and nonflammable constituents, the precise level of risk is more difficult to predict. Mixtures of flammable and nonflammable constituents are especially significant because the vapor phase composition differs from the liquid composition, and it can change from nonflammable to flammable as the mixtures evaporates or its temperatures changes....

Flammability of Li-Ion Battery Electrolytes: Flash Point and Self-Extinguishing Time Measurements

“…The most common oxidant is oxygen from the air. 15 During combustion a chemical reaction occurs between the fuel and the oxidant: 14 Fuel + Air → Products + Heat [1] Flame reactions for combustible liquids (and also for solids) always occur in the gas or vapor phase. The combustion is only sustained when it releases more heat than what is absorbed by the surrounding environment.…”

“…5,14,15 The lower flammability limit (also called lower explosion limit or lean limit of flammability, LFL) and the upper flammability limit (upper explosion limit, rich limit of flammability, UFL) confine the concentration range of the fuel vapor in air, in which combustion becomes possible. 15 They are usually given in vol.%.…”

Evaluation of lower flammability limits of fuel–air–diluent mixtures using calculated adiabatic flame temperatures

“…At the same time, reliable predictive methods that consider different conditions such as mixture compositions, presence of diluents, and different initial temperatures are needed. A compilation of available prediction methods can be found in the literature [3]. 1200 K is a good criterion for the prediction of the flammability zones for methane and ethylene.…”

On the relation between azeotropic behavior and minimum / maximum flash point occurrences in binary mixtures of flammable compounds

“…A more detailed review on flash point prediction models for pure components and mixtures is available in Vidal et al [27] and Liu and Liu [28].…”