High Purity And High Activity Calcium Oxide Used in Industrial Production

What Is High Activity Calcium Oxide?

Calcium oxide, commonly known as quicklime, is a widely used inorganic compound. It can be found in many industries including metallurgy, environmental protection, chemical engineering, building materials, and others. However, even for the same calcium oxide, its reactivity can vary significantly. Thanks to its fast reaction rate and high utilization efficiency, high‑activity calcium oxide has become the preferred material for high‑end applications, standing in sharp contrast to ordinary calcium oxide.

So what kind of calcium oxide can be called high‑activity calcium oxide? What are its core characteristics and evaluation standards?

High‑activity calcium oxide, also known as active quicklime, has the most outstanding advantage compared with ordinary calcium oxide: extremely high hydration reactivity. When in contact with water, it reacts rapidly, releases a large amount of heat, and reacts completely without residue. This is the core reason for the name “high‑activity”.Simply put, ordinary calcium oxide is a basic raw material with “slow reaction and low utilization”, while high‑activity calcium oxide is a high‑end material with “fast reaction and high utilization”. The difference between them is reflected not only in indicators but also in the essential differences in production processes and microstructures.

Hydration reactivity is the core characteristic of high‑activity calcium oxide and the easiest indicator to judge on site — it refers to the reaction speed, heat release intensity, and completeness of the reaction between calcium oxide and water. In the industry, “digestion temperature rise” and “digestion time” are commonly used for quantitative evaluation.

When high‑activity calcium oxide is mixed with room‑temperature water, hydration occurs rapidly within a few minutes, accompanied by intense heat release, heavy steam emission, and a sharp rise in solution temperature. It can be completely digested in a short time without residual hard lumps. In contrast, low‑activity calcium oxide reacts slowly with weak heat release and long digestion time. It may even have an “unreacted core” and cannot react completely.

The high reactivity of calcium oxide is not inherent; it is determined by the production process. The key production requirements are “light burning, rapid heating, and moderate temperature”. Using high‑purity limestone as raw material, it is calcined at 900–1050 °C with appropriate holding time to ensure that calcium carbonate (CaCO₃) is fully decomposed into calcium oxide (CaO) and carbon dioxide (CO₂), without “over‑burning” caused by excessively high temperature or overly long time.

If the calcination temperature exceeds 1100 °C and the duration is too long, calcium oxide crystals will grow and the structure will become dense, forming over‑burned lime with sharply reduced hydration activity. If the temperature is too low or the time is insufficient, calcium carbonate will not decompose fully, leaving a large amount of unreacted impurities, which also reduces the activity of calcium oxide. Therefore, the “light burning process” is the key to producing high‑activity calcium oxide.

Core Characteristics of High‑Activity Calcium Oxide

Fast and complete hydration reaction, no residual hard lumps, reaction utilization rate above 95%.

High effective content, low impurities, stable chemical reaction, able to meet precise high‑end production requirements.

Loose and porous structure, good adsorption performance; can participate in chemical reactions and adsorb impurities and odors.

Under the same application effect, dosage is 10%–20% less than ordinary calcium oxide, reducing production costs.

Main Application Fields

High‑activity calcium oxide is mainly used in fields requiring high reaction speed and purity, different from basic applications of ordinary calcium oxide:

Metallurgy: Used for molten steel refining, desulfurization, and dephosphorization. It quickly reacts with harmful impurities in molten steel, improving purity and reducing smelting time.

Environmental protection: Flue gas desulfurization, wastewater pH adjustment, soil remediation. Fast reaction and high treatment efficiency, rapidly neutralizing acidic wastewater and removing sulfur dioxide from flue gas.

Chemical industry: Used as raw material for calcium carbide, calcium hydroxide, bleaching powder, etc. Complete reaction improves the purity and yield of downstream products.

Building materials & soil improvement: Used for rapid solidification of construction mortar and soil pH adjustment, shortening construction period and improving improvement effect.

Livestock breeding: Used for disinfection and deodorization in farms. Rapid heat release and strong alkalinity quickly kill pathogens and decompose odors without harmful residues.

On‑Site Rapid Identification Method (No Professional Instruments Needed)

For non‑laboratory testing, the following two simple methods can quickly judge the activity level of calcium oxide, suitable for purchasing and on‑site acceptance:

1. Hydration reaction test (most accurate):

Take about 50g of calcium oxide sample, add about 100ml of room‑temperature water, and observe the reaction.

If the sample disintegrates rapidly, emits heavy steam, releases intense heat, the solution temperature rises sharply, and completely turns into fine paste without hard lumps in a short time — it is high‑activity calcium oxide.

If the reaction is slow, heat release is weak, hard lumps remain for a long time, or almost no reaction occurs — it is low‑activity or over‑burned lime.

2. Appearance and hand‑feel test:

High‑activity calcium oxide is usually loose powder or fine particles, white in color, without obvious hard lumps. It feels light and fragile when rubbed, with no rough particles.

If the sample is dense and hard block, dark in color, difficult to crush by hand, or has obvious stone texture — it is over‑burned lime with very low activity.

On www.cncalcium.com, we specialize in supplying different purity calcium hydroxide and calcium oxide products that are suitable for a wide range of applications, including the chemical, environmental protection, and agricultural sectors. If you're interested in learning more about calcium hydroxide (slaked lime) and calcium oxide(quick lime), please feel free to visit our official website at www.cncalcium.com.