Introduction

The processes of conversion of matter from one state to another have been fundamental to the evolution of the energy industry. One of the most relevant phase changes is the liquid-to-gas transition, which is widely used in various sectors, from power generation to cryogenics and energy storage. This article focuses on the fundamentals of liquid-to-gas conversion, its industrial applications, technological advances, efficiency, and sustainability of operational processes.

Fundamentals of liquid to gas conversion

It is a physical phenomenon based on the absorption of heat energy by a liquid substance. As the liquid receives heat, the kinetic energy of its molecules progressively increases until the intermolecular forces that hold them together weaken, allowing their release as a gas.

There are two main mechanisms in this transformation

Evaporation: Occurs at any temperature below the boiling point and only at the surface of the liquid. It is a gradual process where some molecules of the liquid acquire enough energy to escape to the gaseous state, reducing the temperature of the remaining liquid (evaporative cooling effect). This phenomenon is exploited in industrial application such as water desalination and natural cooling.
Vaporization: A process that occurs when the liquid reaches its boiling point, forming gas bubbles throughout its mass and allowing faster and more uniform conversion. At this point, all the molecules of the liquid acquire sufficient energy to become gas. Vaporization is widely used in steam generation in power plant boilers and in the production of gaseous fuels.

General properties of matter and changes of state

The properties of matter play an important role in the efficiency of conversion processes, as they determine how a substance responds to different environmental and operating conditions. These properties include density, specific heat, thermal conductivity and vapor pressure, which directly influence the ease with which a material changes state.

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Changes of state of matter, particularly vaporization and evaporation, are fundamental processes in multiple industrial applications and depend on variables such as:

Temperature: The higher the temperature, the more kinetic energy the molecules acquire, accelerating the transition from liquid to gas. In the case of evaporation, this can occur at any temperature below the boiling point, while boiling requires reaching a specific temperature.
Pressure: Ambient pressure affects the boiling point; at lower pressure (as in vacuum), liquids boil at lower temperatures, while at higher pressure more heat is required for conversion to gas.
Volume: Expansion of the available volume allows greater dispersion of gaseous molecules, facilitating phase change and preventing premature condensation.

These factors are carefully controlled in industrial processes such as distillation, steam turbine power generation, cryogenic storage and refrigeration systems, where efficient management of state changes improves the safety, performance, and sustainability of operations.

Industrial applications

Liquid to gas conversion has multiple applications in various industries, being a fundamental process to optimize energy efficiency and improve the performance of different systems. Some main industries where it is applied to include:

Power generation with steam turbines: one of the very important operational processes in the energy industry is the generation of electricity through steam turbines. In this system, water is heated in boilers to boiling point and transformed into high-pressure steam that drives the turbines, generating electricity. The efficiency of the process depends on the precise control of vaporization and the properties of the material involved.
Liquid Air Energy Storage (LAES): Liquid Air Energy Storage (LAES) is a recent innovation that takes advantage of changes in the state of matter to improve energy management in power grids. In this system, ambient air is liquefied at extremely low temperatures and stored in cryogenic tanks. When energy is required, the liquid air is heated, expanding into a gas and driving turbines to generate electricity.This process makes it possible to store surplus energy and release it when needed, contributing to the stability of the electricity supply and reducing dependence on fossil fuels. Liquid air energy storage is a promising technology, but still faces challenges in terms of efficiency and cost.
Gasification of liquid fuels: Another field where the transition from liquid to gas has a significant impact is in the gasification of liquid fuels. This process heats liquid hydrocarbons at high temperatures in the presence of steam and oxygen, transforming them into synthetic gas (syngas) for power generation, facilitating their use in gas turbines and internal combustion engines. Gasification allows for more efficient combustion and a reduction in polluting emissions, in line with sustainability objectives in the energy industry.
Regasification of cryogenic fuels: Liquefied natural gas (LNG) stored at extremely low temperatures is gradually heated in heat exchangers or vaporizers, transforming it into gas for distribution and consumption. Similarly, liquefied gases such as nitrogen, oxygen, and hydrogen are vaporized in controlled systems for medical, aerospace and industrial applications.
Chemical and petrochemical industry: In distillation and evaporation processes, heat and pressure reduction are applied to selectively vaporize liquid components and separate them by differences in their boiling points.
Ammonia and methanol production: Precursor liquids are subjected to steam reforming or catalytic processes, transforming them into intermediate gases essential for chemical synthesis.
Metalworking industry: Liquid oxygen and acetylene are vaporized in pressure regulators before being mixed in the torch, producing a high-temperature flame for cutting and joining metals.
Heat treatment: Liquid nitrogen evaporates on contact with hot surfaces, absorbing heat and generating rapid cooling in cryogenic and metal hardening processes.
Food industry: Freeze-drying of food freezes the food and reduces the pressure to sublimate the water directly from solid to vapor, preserving its structure and nutrients.
Medical and pharmaceutical industry: Liquid oxygen is heated to room temperature in vaporizers to convert it into a gas and supply it to patients on life support.
Cryopreservation: Liquid nitrogen is used, which evaporates progressively, keeping biological samples and medicines at ultra-low temperatures without degradation.
Aerospace and transportation: In rocket propulsion, liquid hydrogen is heated in combustion chambers, transformed into gas and mixed with oxygen to generate propulsive force.

Biomass gasification and energy sustainability

Biomass gasification is a process in which organic matter is converted into combustible gas by thermochemical reactions in the presence of oxygen or water vapor. This gas can be used as a renewable energy source, reducing dependence on fossil fuels, with the following challenges and benefits of gasification:

Reduction of carbon emissions: By using organic waste, the process emits less CO₂ than conventional fuels.
Use of agricultural and forestry waste: Minimizes waste and promotes the circular economy.
Decentralized energy supply: Allows electricity to be generated in communities far from the traditional power grid.
Challenges: Despite these benefits, biomass gasification faces challenges such as process efficiency, variability in waste quality and the need for investment in adequate infrastructure.

Conclusion

Advances in operational liquid-to-gas conversion processes are driving the transformation of the energy industry. Technologies such as biomass gasification and liquid air energy storage present significant opportunities to improve the efficiency and sustainability of the sector. However, it is important to address the technological and economic challenges to optimize these solutions and ensure a cleaner and more efficient energy transition in the future.

The future of the energy industry will largely depend on the continuous improvement of these processes, consolidating the transition to a more efficient and environmentally friendly energy matrix.