Hydrothermal Treatments

Hydrothermal reactions in agricultural activities are an alternative to waste treatment to improve processing performance. This has several energy and economic advantages. The ability to process high moisture content biomass waste without practising priority watering leads to several energy and economic advantages without debarring several improvements in process performance. The complexity in the structure of wastes combined with the unique properties of water at a higher pressure and temperature leads to a collection of various physical and chemical reactions along with a wide spectrum of products. This article will deliver extensive information regarding the fundamentals and mechanisms involved in hydrothermal reactions.

What is Hydrothermal?

Hydrothermal refers to a thermochemical process used to deal with the decomposition of carbonaceous materials like biomass and coal by keeping water in a high temperature and high-pressure condition. As the name suggests, it combines water and its thermal properties. This is all about the hydrothermal process, and you have become familiar with its uses in agricultural activities. Let’s discuss in detail the hydrothermal treatment of processing for biomass.

Introduction to hydrothermal treatment

The basic fact for the hydrothermal treatment is the outstanding characteristics of water in subcritical or supercritical conditions. The basics included in hydrothermal treatment consist of the polar nature of water at ambient temperature. There is an infinite hydrogen bonding network, resulting in a failed solubilization of most organics. When heat is applied to water, the hydrogen bonds present in water start getting weak. It eventually results in the dissociation of water molecules into hydro one alliance and hydrocele ions, represented as H3O+ and OH- respectively.

The hydrothermal treatment process allows the subcritical water to further dissolve with organic compounds with the help of a low dielectric constant. In contrast, a high dielectric constant allows the subcritical water to produce an acidic medium and allows the hydrolysis of biomass components.

In addition to that, the change in temperature or pressure of water in the subcritical region results in tuning several physical properties of water like density, ion product, dielectric constant, and viscosity. 

A three-step guide to understanding the Hydrothermal processing

Hydrothermal processing of wastes is divided into three specific processes depending on the operating conditions. 

• At temperatures between 180 and 250 degrees Celsius, the process is hydrothermal carbonization, where the main product is hydrochar containing similar properties as low-rank coal.

• At temperatures between 250 and 375 degrees Celsius, this process is known as hydrothermal liquefaction, where the end product is a liquid fuel which is widely known as biocrude. Biocrude can be further used after distilling a range of products derived from petroleum.

• At higher temperatures above 375 degrees celsius, hydrothermal treatment is known as hydrothermal gasification. The product is a synthetic gas different from the conventional syngas consisting of hydrogen and carbon monoxide.

However, it is to be noted that all three processes of hydrothermal treatment result in generating a biofuel that offers high energy compared to the initial waste. 

Benefits of Hydrothermal Process

Hydrothermal treatment is a combined process that utilises the properties of water to carry out the production of biofuel from various wastes. Mostly it is used to convert agricultural waste to biofuel. Now that you have understood the concept of hydrothermal treatment and its use as a production process for various biofuels.

Let’s understand the advantages and benefits offered by hydrothermal treatment of processing. The technique of using hydrothermal processes for thermochemical conversion is quite beneficial and holds several advantages like

• A much lower temperature for hydrothermal treatment
• It takes place in a wet environment
• The high moisture content of biomass is not needed
• Water acts as a decomposition chemical reactant
• It is often considered best to treat biomass with high moisture content.

The best advantage of hydrothermal processing is its ability to process wet waste. The waste does not require drying as hydrothermal processes can hold hand process wastes with total solids ranging from 10 to 30%.

Conclusion

The hydrothermal process refers to compressed hot water as a medium to facilitate a reaction. We have discussed the three processes involved in hydrothermal treatment with their conservative results as a biofuel production process from different types of wastes.  As it requires water, it is considered a suitable method for treating wet biomass resources like agricultural waste. In this article, we have discussed the concept of hydrothermal processing and how it is beneficial in the case of wet waste processing.