Carbon Dioxide

What is CO₂?

Carbon dioxide is the combination of two atoms of oxygen joined with a single atom of carbon. Its chemical formula CO₂, is almost as well-known as that of water, H₂O, and it is frequently referred to by its formula rather than its name.

In nature’s chain of life, the mutual dependence of plant and animal life is maintained through the link of carbon dioxide. Every time we breathe we release this gas, which plants need for life. Through the process of photosynthesis, the plants separate the carbon from the oxygen. In turn, plants release the pure oxygen, which we need to survive. We reverse the process, and by combining the oxygen with carbon from the foods we eat, produce carbon dioxide again.

CO₂ is a colourless, inert gas approximately 1 ½ times heavier than air and 0.03 % is present in the earth’s atmosphere. It is odorless, has a sweet biting taste (soda water) and is highly stable (difficult to separate).
It is produced in varying amounts by the common process of combustion of fuels high in carbon content. The most common source of fuel for combustion is oil which, when mixed with the correct proportion of air, burns to produce around 15 % CO₂ in the flue gases of a CO₂ plant. After combustion has taken place, the CO₂ can be separated from the flue gases and, through a simple process, made available for the many commercial purposes to which it can be applied.

CO₂ can exist in three forms:
– in gaseous form: for the beverage and food industries
– in liquid form: in a storage tank under pressure
– in solid form:  called dry ice (for cooling, blasting etc.)

Gaseous CO₂

Gaseous CO₂ can be liquefied under pressure provided its temperature is below 31 °C (87,8 °F), this temperature being referred to as the CRITICAL POINT. If compressed and cooled below the critical point, a colourless fluid, approximately the same density as water, is produced.
CO₂ will remain in the liquid form as long as its temperature remains below the critical point but will return to the gaseous state if its temperature rises above this point, regardless of the pressure applied.

Liquid CO₂

Liquid CO₂ can be stored indefinitely at high pressure or Low pressure as follows:

High Pressure CO₂
High pressure liquid CO₂ is produced by compressing the gaseous CO₂ in multistage compressors to pressures in the neighbourhood of 69 bar (1000,76 psi) pressure, then cooling it to around 18 °C (64,4 °F). It is customarily filled into specially constructed steel cylinders. Like water, liquid CO₂ can be weighed, and this is the normal form of measuring it.

Low Pressure CO₂
Low pressure liquid is an alternative method of storing CO₂ and is produced either by expanding high pressure CO₂ to a lower pressure or by refrigeration. It is held in specially constructed storage tanks, heavily insulated and equipped with refrigeration units to hold the internal tank pressure at or below 21 bar (304,58 psi) and -18 °C (-0.4 °F) temperature. Pressure switches are incorporated to control the refrigeration units and safety mechanism and electrical alarms are fitted to release the tank pressure and raise an alarm in the event of refrigeration malfunction.
Low pressure liquid CO₂ (sometimes referred to as “bulk”) is transported to one place from another in insulated road tankers or trailers (or, in some countries, by rail tank wagons), the liquid being simply transferred from mobile to static tank by pumping or gravity feed.
Unlike water, carbon dioxide cannot exist in the open air in liquid form. It must be held under pressure or refrigeration (or a combination of both) to remain in the liquid state.

Even though anhydrous ammonia is useful, it must be handled with caution. Ammonia can cause physiological damage, and can even ignite into deadly explosions.

Anhydrous Ammonia Uses

How is anhydrous ammonia used? As a liquid, it’s commonly diluted and used as a household cleaner. You may have smelled the sharp odor of ammonia while cleaning your bathroom or kitchen. Anhydrous ammonia is also an important industrial cleaner, where its full strength can eradicate some strains of harmful bacteria and make industrial metal shine.

As a fertilizer, anhydrous ammonia gas is compressed into liquid and mixed with other plant growth enhancers. It can also be applied in gaseous form, where it combines with the moisture in the dirt, resulting in ammonia-enriched fertilizer soil. Even though anhydrous ammonia can be very dangerous, the nitrogen within its chemical structure actually makes the chemical quite healthy for plant growth. Anhydrous ammonia is widely available and easy to apply, making it a good option to boost plant productivity.

Anhydrous ammonia is used in the manufacture of a number of medicines. However, that also makes it a high risk for theft and use in the illegal manufacture of methamphetamine, a psychoactive drug also known as meth. Theft of the amount of anhydrous ammonia needed to make methamphetamine usually targets agricultural storage centers, where the ammonia is kept for fertilizer use. Its importance as an intermediate step in the formation of other chemical compounds makes anhydrous ammonia a common presence in pharmaceutical chemistry labs.

Difference between Ammonia and Anhydrous Ammonia

It is designated in chemical notation as NH3. … Household ammonia is a diluted water solution containing 5 to 10 percent ammonia. On the other hand, anhydrous ammonia is essentially pure (over 99 percent) ammonia. “Anhydrous” is a Greek word meaning “without water;” therefore, anhydrous ammonia in ammonia without water.