Leaving Cert Chemistry - Option 1A: Industrial Chemistry

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Magnesium oxide is manufactured by Premier Periclase in Drogheda.
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This magnesium oxide (also called periclase) is used to make heat resisting blocks for lining furnaces.

There are 4 steps in the process of manufacturing periclase.
1. Limestone [CaCO3 is converted to lime [CaO]
2. Lime is converted to slaked lime [Ca(OH)2]
3. Slaked lime reacting with magnesium chloride in seawater to produce magnesium hydroxide [Mg(OH)2]
4. Magnesium hydroxide is converted to magnesium oxide [MgO]

The important factors to take into account when setting up a chemical industry are:
Feedstock (produced from raw materials)
Reaction Rate
Product Yield
Co-Products
Waste Disposal and Effluent Treatment
Quality Control
Safety
Costs (Fixed and Variable Costs)
Site Location
Plant Construction Materials

periclase1a.jpg
There are three types of industrial process - continuous, and semi-continuous.
The process where the reactants are continuously fed into the reaction vessel, and the products continuously removed is known as .
Whereas in a batch process, a certain amount of product is made in a reaction vessel in a particular .
A process is where part of the process is batch and part is continuous.
This is a case study of the manufacture of magnesium by Premier Periclase near the town of Drogheda.
The feedstock in any process are the .
Feedstock is made from the .
The feedstock here is [MgCl2] and [Ca(OH)2].
The magnesium chloride and calcium hydroxide are obtained from the raw materials, seawater and respectively.
Solids in the seawater are allowed before the seawater is acidified with acid and passed against a rising current of air to remove .
The limestone is and washed and heated in a to form calcium oxide. Fresh water is added to the calcium oxide to form calcium .
The rate of production is not affected as there is no used, the reaction is not reversible, and it can only be carried out at atmospheric pressure.
When magnesium chloride and calcium hydroxide react, they form ,
MgCl2 + Ca(OH)2 ---> CaCl2 + Mg(OH)2
In order to produce large of magnesium hydroxide, the incoming seawater is diluted with spent , and the reaction mixture is seeded with a slurry of magnesium hydroxide.
The magnesium hydroxide is converted into by heating it in a furnace.
Mg(OH)2 ---> MgO + H2O
The magnesium oxide is a fine powder which is changed into under pressure, and then heated in a kiln to produce large of magnesium hydroxide.
There are no commercially profitable co-products.
Dust is extracted from the combustion gases by .
The of the water is adjusted before returning to sea.
All from the plant are monitored.
Quality Control: Acid-base and X-ray analysis are used at various stages of production.
Health and Safety: Personal protective equipment is used where required e.g. safety goggles, boots, helmets, earplugs, clothing are used.
The fixed costs include labour, plant and plant depreciation.
Variable costs include electricity, , materials and waste disposal.
The site is located near Drogheda because of (i) the availability of a skilled workforce,
(ii) near a supply of limestone and seawater.
(iii) rail, and sea transport are available nearby, and
(iv) there were kilns already on the site from a previous .