Unlocking the Power of Phosphoric Acid: From Production Methods to Practical Applications

H3PO4, often referred to as Orthophosphoric acid or Phosphoric acid, is a silent hero in our daily routines that might not be well known but plays a vital role. This acid, which is very useful, finds uses in fertilizers that feed our crops, carbonated beverages we love, and many more! It is the same question that follows: how is this acid being manufactured and what are the places where we find it?

In this blog, we are going to take a glance at the really interesting world of phosphoric acid. We shall look at the two processes which are adopted for the production of it, i.e., wet and thermal processes. Following that, we will unravel the mystery behind its diverse uses, including its involvement in agriculture and the fact that it is surprisingly a component of our cosmetics and food!

We’ll explore handful of its many applications such as:

• Food science: It gives a fresh and strong kick to processed foods and drinks, while also working as a preservative.
• Plant power: Phosphoric acid, which is a main constituent of fertilizers, supplies the associated phosphorus which is required to sustain healthy plants.
• Beyond the surface: Phosphoric acid is one of the key ingredients in personal care products to keep the right balance of the pH level.

In short, this is the time to fasten your seatbelt as you are going to unveil the power of H3PO4.

Introduction

Phosphoric Acid (H3PO4) is a versatile acid with a presence in countless industries.  But before we delve into its uses, understanding its structure and properties is key.  These characteristics, essentially its makeup and behavior, are what make phosphoric acid so valuable in fields like agriculture, personal care, and even beverages.

These are:

• Rust removal: Phosphoric acid can convert the iron oxide layer (rust) on metal surfaces into a phosphate layer. This phosphate layer acts as a protective barrier, preventing further rust formation.
• Food and Beverage: Food-grade phosphoric acid adds a tangy flavor and acts as a preservative in colas, jams, and processed meats.
• Agriculture: The biggest use of phosphoric acid is in fertilizers. It provides essential phosphorus for plant growth.
• Personal care: Phosphoric acid helps adjust the pH level in cosmetics and skincare products.
• Pharmaceuticals: Phosphoric acid finds use in some medications and as a starting material for drugs.

Manufacturing Process

There are two main ways to make phosphoric acid: the wet process and the thermal process. The wet process is more common and used for fertilizers, while the thermal process creates a much purer form of phosphoric acid used in high-quality products like medicine, detergents, food, and beverages.

Wet Process

• Treating sulfuric acid (H2SO4) with naturally occurring phosphate rock involves drying and crushing the rock before continuously introducing it into a reactor alongside sulfuric acid. This reaction leads to the combination of calcium from the phosphate rock with sulfate, resulting in the formation of calcium sulfate (CaSO4), commonly known as gypsum.
• Gypsum is separated from the reaction solution through filtration. Facilities typically employ a dihydrate process, yielding gypsum in the form of calcium sulfate with 2 molecules of water (CaSO4.2 H2O, or calcium sulfate dihydrate)
• Some other facilities utilize a hemihydrate process, which yields calcium sulfate with half a molecule of water (CaSO4.½ H2O). The one-step hemihydrate process offers the advantage of producing wet process phosphoric acid with a higher concentration of P2O5 and fewer impurities compared to the dihydrate process.

A simplified reaction for the dihydrate process is outlined below:

• To produce the strongest phosphoric acid and reduce evaporation costs, typically 93 percent sulfuric acid is utilized. Maintaining the precise ratio of acid to rock in the reactor is crucial, so advanced automatic process control equipment is employed to regulate these two feed streams.

• During the reaction, gypsum crystals are formed and separated from the acid through filtration. These crystals undergo thorough washing to ensure at least a 99 percent recovery of the filtered phosphoric acid. After washing, the gypsum slurry is transferred to a gypsum pond for storage. Water is extracted and recycled through a surge cooling pond to aid in the phosphoric acid process.

• Considerable heat is generated within the reactor. In older plants, this heat was dissipated by blowing air over the hot slurry surface. However, modern plants employ vacuum flash cooling to cool a portion of the slurry, which is then recycled back into the reactor.

• Wet process phosphoric acid typically contains 26 – 30% of P2O5. To meet phosphate feed material specifications for fertilizer production, the acid often requires further concentration. Depending on the intended fertilizer types, phosphoric acid is concentrated to 40-55% of P2O5 using two or three vacuum evaporators.

Thermal Process

The production of phosphoric acid by thermal process requires elemental (yellow) phosphorus, air, and water as raw materials. This manufacturing process involves three main steps: Combustion, Hydration, and Demisting.

• During combustion, liquid elemental phosphorus undergoes oxidation in a combustion chamber, typically at temperatures ranging from 1650 to 2760°C. This combustion reaction forms phosphorus pentoxide. It is depicted in the following reaction:

• The produced phosphorus pentoxide is then hydrated either with dilute H3PO4 or water to generate strong phosphoric acid liquid. This is depicted in the following reaction:

• The final step, demisting, involves the removal of phosphoric acid mist from the combustion gas stream before it is released into the atmosphere. This is typically achieved using high-pressure drop demistors.

• The phosphoric acid concentration typically falls between 75 – 85% in the output from the thermal process. Such a high concentration is necessary for the production of high-grade chemicals and various non-fertilizer products.

Applications of Phosphoric Acid

1. Agriculture

The phosphoric acid is considered as a crucial chemical in modern agriculture as it performs diverse functions including production of fertilizers, amendment of soils, animal nutrition, and environmental preservation. The majority of the phosphoric acid is applied to fertilizer production, where it plays the fundamental role of forming the phosphate fertilizers, which are essential for the healthy growth of crops and maintaining the soil fertility. Furthermore, phosphoric acid helps in poultry feed as a source of dietary phosphorus. Among the widely used phosphatic fertilizers are diammonium phosphate (DAP), monoammonium phosphate (MAP), NPKs, and SSP. DAP stands out as a valuable provider of both phosphorus and nitrogen, essential for plant growth and development, particularly in cereal grains, fruits, and vegetables. By improving soil fertility, DAP contributes to enhanced crop production efficiency.

2. Food & Beverages

Phosphoric acid finds application as a food additive, serving as an acidity regulator in various food products such as jams, cereal bars, processed meats, and cheese. Within the beverage industry, it acts as an acidic agent, playing a crucial role in preventing the growth of fungi and bacteria while imparting a distinctive flavor to these drinks.

3. Rust Removal

Phosphoric acid is among the various acids commonly employed for rust removal from metals like iron and steel. When applied, it initiates a chemical reaction wherein the reddish-brown ferric oxide, commonly known as rust, undergoes transformation into a black-colored compound known as ferric phosphate. This reaction effectively breaks down and reacts with the rust present on the metal surface. Subsequently, the resulting black ferric phosphate compound can be easily extracted, leaving the metal surface free from rust and restored to its original state.

4. Personal Care & Cosmetics

Phosphoric acid plays a crucial role in the production of a diverse range of personal care items, cleaning products, bath formulations, fragrances, hair care solutions, dyes, nail treatments, lipsticks, and skincare preparations. Its function extends to regulating the pH levels of these materials, ensuring their effectiveness and stability. However, it is advisable to seek guidance from reputable phosphoric acid suppliers to gain comprehensive insights into its proper usage, applications, and characteristics.

Market Outlook

The main reason for the market of phosphoric acid development is the rise of the demand for DAP phosphate fertilizers. Being the most essential intermediate product in the course of the phosphate fertilizer manufacture, phosphoric acid is employed to make DAP, MAP, NPKs and SSP. DAP plays a major role in fulfilling the fertilizer demand of which is due to its rich nutrient content and ability to increase the soil fertility and crop production. The rise of world population and consumers’ buying power is likely to lead to more agricultural output. Thus, DAP fertilizers are utilized to balance the soil phosphate deficiency and improve crop production. This is likely to be the reason behind the rise of phosphoric acid consumption in the near future.

Phosphoric Acid Major Global Producers

Main players in the Global Phosphoric Acid market are Mosaic Company, IFFCO, Nutrien, Ma’aden, J.R. Simplot Company, ICL-YTH Group, OCP Group, Wengfu Group Co., Ltd., ICL(Rotem), Indorama (Industries Chimiques du Senegal), PhosAgro, Foskor Group, Rotem Amfert Negev Ltd., Yara, Coromandal International limited, JIFCO, and Indo Maroc Phosphore SA (IMACID), and Others.

Conclusion:

Phosphoric acid (H3PO4) has a range of uses which are reflected by the fact that it provides the sharp fizz of your favorite cola and the fertilizer that nourishes your crops. It fights rust, brings out the shine of metal surfaces, and lengthens their life. In food science, it can do the trick of adding flavor and preserving the food. The phosphorus it provides for plant growth is one of the main constituents of fertilizers. Besides food and agriculture, phosphoric acid is used for the maintenance of proper pH level in personal care products and also is in the list of vital components in dentistry and pharmaceuticals. Therefore, the next time you sip a beverage, marvel at a rust-free piece, or maintain your garden, remember the hidden ability of phosphoric acid to bring its magic to everyday life.