Water sachet nylons, polythene bags, plastic bottles, broken plastic buckets, basins, cans etc., litter the streets and gutters leading to blockage of drains and generally making the environment unsightly and unhealthy. It was so bad that the former Director-General of NAFDAC, Professor Dora Akunyili called for the banning of sachet water because of the amount of waste generated.
Sometimes, these wastes are buried in the ground but the problem is that they render such land infertile because they do not decompose easily. At the recently held Nigerian Secondary Schools Science Fair organised by Genius Illumina at the University of Lagos, students from various secondary schools from across the nation showcased their works. Most of them were geared towards solving the nation’s power and security challenges.
Government Girls’ Secondary School, Dutse, Abuja, one of the participating schools, showcased their project which was on generation of synthetic crude oil from plastic wastes. Although the principle has been in use in some parts of the world, but the girls made it so simple that it can be done in remote places and by anyone. The girls – Chukwumerije Chisom, Felix Blessing and Patience spoke with Vanguard Learning. Excerpts:
According to Chukwumerije Chisom, the device was fabricated for converting waste plastics into alternative source of fuel. “Plastic waste materials are the most common wastes in our environment.
They litter everywhere. They are non-biodegradable, i.e. they cannot be decomposed by microorganisms and as a result, they last for decades in the soil without decomposing and occupy a large land mass thereby making land scarce and expensive.
Burning of these plastic materials is not a solution because they release some gases such as sulphur and carbon dioxide into the environment. The sulphur combines with water vapour in the atmosphere and comes down as acid rain which is harmful to living things.
Also, if the carbon dioxide is inhaled by living organisms, they compete with the haemoglobin in the red blood cells for oxygen which leads to suffocation and death.
We thought of a better solution to this problem i.e. making use of a combustor to transform these wastes into an alternative source of fuel which can help sanitize our environment and as well serve as a source of fuel in homes and industries.”
The process:
Describing the process, Felix Blessing said; “We have two combustors – Step A and Step B combustors. There is one for absorption of impurities, anhydrous cobalt (ii) chloride for absorption of the steam.
The Step A combustor is further divided into two chambers – upper and lower chambers.
In between the two chambers, there is a membrane which allows the passage of gas from the lower to the upper chamber of Step A combustor.
In the lower chamber, there is an inlet through which the plastic wastes are deposited and in the upper chamber of Step A combustor, there is a delivery tube through which the gases migrate from the upper chamber of Step A combustor to Step B combustor.
The process is called cracking. Cracking is the breaking down of larger hydrocarbons into smaller hydrocarbons.
When the plastic is placed in the lower chamber of Step A combustor, and as the heat increases, there is a change of state, from solid to liquid state and as the heat persists, the liquid changes to gases which then evaporate.
There are some gases that are present during the thermal cracking process in the Step A combustor because of the presence of heat.
Catalytic cracking takes place in Step B combustor because of the presence of oxidants.
The gases formed in Step A combustor are the organic and impurity gases. The organic gases are the smaller molecules of hydrocarbons like methane, butane and propane.
The impurity gases are the sulphur and carbon dioxide. What gives rise to the formation of the carbon dioxide is the heating of the carbon compound. And what gives rise to the formation of the sulphur is the vulcanization of the plastics.
The sulphur is added to plastic to make it hard so as the gas migrates to the upper chamber of Step A combustor, it passes through the delivery tube to Step B combustor.
Now, the carbon present in Step A combustor is oxidized to carbon dioxide in the Step B combustor while the sulphur present in Step A combustor is oxidized to sulphur (iv) oxide.
So the smaller hydrocarbon molecules pass through the delivery tube with the oxidized impurity gases into the dilute sodium hydroxide where the carbon dioxide is completely absorbed while the sulphur (iv) oxide is partially absorbed.
We are left with the organic gases and the partially absorbed sulphur dioxide which come into the iron (iii) oxide and the sawdust.
The iron (iii) oxide is deliquescent that is why the saw dust is added to it to prevent it from becoming a solution. If a deliquescent substance is exposed to the atmosphere, it absorbs water and becomes a solution so the function of the iron (iii) oxide is to absorb completely the sulphur dioxide that was partially absorbed in the dilute sodium hydroxide.
“We are now left with the organic gases which come along with steam. They pass through the delivery tube and go into the anhydrous cobalt (ii) chloride where the steam is absorbed leaving us with the smaller molecules of hydrocarbon (organic gases) which pass through the condenser and come out as crude oil.”
Benefits:
Said Patience; “We can get kerosene, petrol, bitumen, asphalt and gases from the crude oil when it undergoes fractional distillation. We can use kerosene for cooking in homes, bitumen and asphalt for road construction. When the steam being absorbed by the cobalt (ii) chloride is separated, it can be used by hydroelectric stations to generate electricity.
There is a residual from the Step A combustor and when it is mixed with silica, it can be used to make ceilings, tiles, and interlocks.
The dilute sodium hydroxide which turns yellow in colour, if poured on the ground, can cause damage to plants so what we do is to empty it into a pit toilet and it helps to decompose the waste in the pit toilet.
One of Nigeria’s problems is lack of electricity, so if government and individuals can help us, and this project is well established, you will find that the problem of electricity will be partially solved. It will help to sanitize the environment, serve as a source of revenue to government and will create employment for citizens.”
[Vanguard]
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