Archive for December, 2011

December 17, 2011

Magnets are so magical.

by iSam

Happy Holidays to everyone and hope many magical things happen to you all.

Speaking about magic, magnets actually are not much different to this word . In fact, magnets are very mysterious and many of its properties are still not known. I will be back to that statement soon.

At this moment, I would like to share something about magnets, and tell you why magnets are so mysterious and magical. Furthermore, I also want to inform the applications of magnets that eventually could help us to achieve many great inventions in today’s world and tomorrow’s.

Before I start, however, I would like to share  a little bit of credibility. I have been learning physics since high school and this material (magnets) have been mesmerizing me and I wish to study them a lot more. I have done a lot of readings of text books, scientific journals, articles and even I have ever conducted experiment to make a small levitating device from neodymium magnets. Which is something look like this:

Last but not least is that I am currently taking quantum chemistry (mechanics) class which helps me to understand the subatomic events of a matter.

There are 2 main points that I would like to share. Let’s start with the first one:

600 BC (long time ago) people discovered stones that seemed to have magical powers. These stones were called lodestones and were made of mineral called magnetite. It is an iron-rich ore material that has chemical formula Fe3O4. Its power is called magnetic force and is emitted by magnetic field.

Lodestones were used as compasses in 12th to 13th century. 

Today, there are many kinds of magnets and they have different strengths. Some are weak and some are strong. The strongest magnets on earth are neodymium magnets (Nd2Fe14B) and it is widely used everywhere.

How do magnets work? What is magnetic field made of?  and how to observe them? These are good questions and deserve a good answer, and the best way to observe magnet is by simple observation – that is by “hands-on” experience with magnets.

We know magnets have 2 poles and so are called dipoles. North hates north, south hates south, and south loves north. There is no such thing as one pole magnets (monopole) even if u try so hard to split them into 2, you will still get 2 poles. Weird ah?

Now the fun begins,

Why magnets behave like this? why can’t we get 1 pole magnet? Honestly, we don’t know yet why would magnets behave like this.  And that makes magnets so magical and mysterious, people. Believe me.

Nevertheless, let’s begin the second main point.

There are countless applications of magnets in today’s world. I’m just going to inform you some:

1. Magnets are used in electrical devices to move engines, transmit sound waves, and so on.

2. Magnets are lately used in Maglev trains technology.

Superconductor + magnetic field = great levitation. Superconductor hates magnetic field so much. They repel each other. This property has been applied to the new era of train that can run up to 361mph.

Tomorrow applications are very tempting and promising.

1. Transportation

Imagine if cars or belts are made of superconductors at room temperature . You can almost be like superman hovering on earth above magnetic field track. Lately, scientists have discovered a very promising application of magnets which they call it as quantum locking ( it looks like the Meissner effect, but they call it quantum locking for credit).

2. Energy

We know energy is the society needs for survival and development. Today, we have energy from dead plants, oils and coals. These are fossil fuels which are not good because it is not renewable and not clean for our planet. Furthermore, it brings about conflicts between nations. So we can’t rely on this type of fuels too much and too long.

So does nuclear power (fission). It is not safe because it contains dangerous radioactive wave and if a reactor leaks it will endanger human life and our planet. We have seen many examples of this, one in this year was when Japan got shaken by earthquake. Fukushima nuclear reactor emits radiation.

Now, imagine an energy source which is safe, clean and abundant. It could have a profound effect to our society. It could change everything. That energy source in fact has been being developed by scientists since 60 years ago. And that energy source would be nuclear fusion.

Our sun is a massive fusion reactor, its core is so hot that atoms of hydrogen are forced together and eventually giving off massive amount of energy. Hydrogen is the fuel of the fission reactor. It is so clean and abundant in our planet. Currently, we just need a bigger reactor to conduct a self-sustaining nuclear fusion reaction and that will be built in France in 2020. A powerful magnetic field is needed in order to make this  reaction happen. And that’s you see how important magnets are. You may google them to gain more information.

Cheers,

December 15, 2011

SO2 removal from the flue Gas

by iSam


Sulfur dioxide is released by volcanoes and by various industrial processes such as from the combustions of fuels (oils and coal) in power plant or from fractional distillation process of crude oils. Generally, any fuels that contain sulfur compounds (e.g. Petroleum and coal) generate SO2 in their combustions unless the sulfur compounds are removed before it contacts with oxygen. However, the process of removal of sulfur compounds (e.g. hydrodesulphurization) from fuels is difficult and expensive and is not going to be discussed.

When sulfur dioxide dissolves in water droplets in clouds, it will form H2SO4, and thus it makes the rain more acidic than normal. This generates a phenomenon called acid rain. The impacts of acid rain are crucial to the environment; hence, the emission of SO2 from these fuels is regulated by federal laws in many countries.
There have been many methods developed to remove SO2 from the waste gas (flue gas). The most effective way is by microwave and beam processing which gives efficiency almost 100%. However, it’s never been easy and cheap to install the system. Therefore, it is not commercially applied in industries. In turn, a continuous Flue Gas Desulfurization (FGD) system is the most commercially-used method in many industries by using absorbance technology. Moreover, the installation and maintenance fees of FGD system are reasonably affordable.
The main contributor of SO2 is from power plants of coal or oils. However, for simplicity of making this report SO2 is injected from fractional distillation tower of crude oil. FGD system today has several process types:
a) Wet scrubbing
b) Dry scrubbing
c) Wet sulfuric acid method
d) Spray-dry
e) SNOX FGD
Regardless of the process type, the degree of SO2 removal attempted is a major consideration and wet scrubbing was found to give the highest efficiency of more than 95% removal of SO2. Wet scrubbing system itself uses various sorbents such as limestone (CaCO3), calcium oxide (CaO), lime slurry [Ca(OH)2)], magnesium hydroxide [Mg(OH)2], etc. To partially offset the cost of FGD-wet scrubbing installation, application of CaCO3 sorbent eventually produces a marketable by product (gypsum) when it is contacted with water. Commercially, this technique is known as forced oxidation and the overall reaction of the FGD system is:

CaCO3 (solid) + 1/2 O2 (gas) + 2H2O (liquid) + SO2 (gas) → CaSO4.2H2O (solid) + CO2 (gas)

A process diagram of FGD – wet scrubbing system is shown below:

File:Flue gas desulfurization unit EN.svg

According to US Energy Information Administration data, 27,973,918 barrels of sulfur was contained in a production of crude oils in 2010. This value is equal to 4,441,139,222 Liters of sulfur per year 2010.

By assuming an ideal system, if 1,174,904,556 gallons of sulfur comes into a distillation tower of crude oil, the same amount of SO2 will come out. Or by stoichiometry:

S +O2 → SO2

The amount of SO2 formed then will be going to the FGD-system as the inlet amount.

By having the stoichiometry of the overall reaction in the FGD system and knowing the fractional conversion of the process, we are able to determine how much gypsum is produced and how much SO2 is released every year from the system. Some calculations we have made:

4,441,139,222 Liters = 4,441,139.3 m3

m= 4,441,139.3 m3 x (2.6288 kg/mol)  = 11,674,867 kg

11,674,867 kg (1000g/kg) (1mol/64g) = 182,419,797 mol of SO2 comes into the FGD system.

From stoichiometry, we can find directly that:

182,419,797 mols of CaCO3; 91,209,899 mols of O2; and 364,839,594 mols of H2O come into the batch.

However, we have constrained to take 96% efficiency of FGD wet scrubbing system (96% fractional conversion is taken), and by using atomic balances we are able to find how many moles of SO2, CO2, and gypsum yielded, and how many mols of CaCO3, O2, and H2O needed.

Compounds

Mols  per year

Oxygen (O2) 87,561,503 mols needed
Limestone (CaCO3) 182,419,797 mols needed
Water (H2O) 350,246,010 mols needed
Carbon dioxide (CO2) 175,123,005 mols released
Gypsum (CaSO4.2H2O) 175,123,005 mols produced
Sulfur dioxide (SO2) 7,296,722 mols released

Since SO2 is an acid gas, the typical water used to help to absorb SO2 is sea water (alkaline).

The amount of gypsum produced as the byproduct of the reaction in turns can be sold in markets to produce valuable products such as plaster or plaster wallboard. The quality of gypsum produced is however affecting the selling price. Therefore, subsequent reduction-oxidation reactions for gypsum are sometimes applied in many industries to attain a high quality of gypsum.

Work Cited

Slack, A. V. (1971). Sulfur dioxide removal from waste gas. Noyes Data corporation.

(1991). Desulphurisation 2 technologies and strategies for reducing sulphur emissions. (symposium ed., Series no 123). Rugby, UK: Institution of Chemical Engineers (Great Britain).

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