Fluid Coking : A Coke Treatment process in Refinery

 

                 

                                                                                                 

PC:http://content.inflibnet.ac.in

It is a much simpler version of flexi-coking process consisting of a reactor bed and a burner.

It does not consist of a gasifier.

In fluid coking, feed is first preheated to 260oC and then sent to a scrubber unit located above the reactor bed for recovering fine particles of coke from overhead vapors. The fine particles are recycled with heavy compounds and are entered into the reactor bed and the coking process takes place.

The lighter products from the reactor are withdrawn as overhead vapors and the remaining coke at the bottom is separated continuously . 

The cold coke at the bottom of the reactor is fed into the burner in a layering manner , and a scrubber is also present there to scrub any heavier hydrocarbons on coke, where it is fluidized with the help of steam. Some part of coke (15-30%) is sent to burner for combustion along with injected air and the coke is heated up and the rest is separated out.

The hot coke is sent back to the reactor bed and combustion of coke in the burner produces flue gases of lower calorific value which is processed with the help of separators, scrubbers etc. and can be used in steam generation , power generation etc.

The pet coke so obtained out of burner is used as cement industry fuel and partial oxidation feed.

So, it can be analyzed that both fluid and flexi-coking processes involve separation of lighter materials from the VDU residue and reduction of coke as plenty of coke is used in heating up the coke.

Therefore, much of the residue is converted to fuel gases during combustion to heat up the coke and lighter fractions at the top of reactor bed  and the remaining is left up as pet coke. Also, the amount of coke left in case of flexi-coking is less than that of fluid coking.

Bioplastic From Starch- Phase 1 : Extraction of Starch from potatoes

  INTRODUCTION

Plastic is a material that is used to a great extent. Most plastics that are commercially used today are petroleum based, meaning that they can take more than a century to degrade. Nothing in our natural environment is capable of easily breaking them down since polyurethane and polyethylene are man made polymers that microorganisms don’t recognize as food. When burned, plastics release cancer causing carcinogenic chemicals that are equally harmful to people and the environment. The world is drowning in excess environmentally harmful plastic which is made from oil- a nonrenewable resource.

Bioplastics are a large family of different materials with different properties. Fossil fuel-derived plastics are non-renewable, often threaten the environment, have declining impacts on marine life and increase dependence on imported fossil fuel-based feedstock’s. A plastic material is defined as bioplastics if it is either, biobased, biodegradable, or features both properties.Biodegradation is a chemical process during which the tiny organism or microorganism that is present in the environment convert materials into natural substances such as water, carbon dioxide, and compost that predominantly depend on the surrounding environmental conditions. One of the most undeniable and long-lasting recent changes to our planet is the accumulation and fragmentation of plastics.

One environmentally friendly alternative to the current commercial plastic is Bioplastics. Bioplastics are biodegradable plastics that have components derived directly from renewable raw plant materials. Their polymers are made from plant materials and they decay into natural materials that blend harmlessly with soil. Some bioplastics can break down in a matter of weeks. Therefore, bioplastic can be a better option for our present day problem of waste management and our project will be based on potato obtained starch bioplastic.

    

Experiment Procedure:

Objective-

To prepare bioplastic from starch extracted from potato.

The experiment was done in two phases :

1. Extraction of starch from potato.

2. Preparation of bioplastic from starch.

Phase 1:

Extraction of starch from potato.

Aim: To isolate the starch from the given potato sample.

Principle: Starch is an important polysaccharide found in plant sources. The microscopic appearance of starch is in the form of granules. It is typical for the individual starch granules. They differ in size depending on the source from which they were isolated. Starch is insoluble in water and rapidly settles at the bottom and can be collected by decanting the supernatant. 

Materials Required: 500 gm Potato, Muslin Cloth, Watch Glass, Mortar and Pestle, Test Tube, Iodine solution etc., 

Procedure: 

1. Peel a raw potato and cut into small pieces, and record the initial weight. 2. Grind them in a motor and pestle with sufficient water. 

3. Collect the potato homogenate into a beaker and add enough water. 

4. Then filter the homogenate through a muslin cloth to remove the particles. 

5. Allow the filtrate to settle. Starch rapidly settles at the bottom. Decant the starch free supernatant carefully. 

6. Wash 3-4 times and decant the supernatant. Collect the compact mass of starch and allow it to dry. 

7. Record the final weight of isolated starch and calculate the yield.

Result: The given sample contains  18 gm of starch/100 gm potato. 

Iodine Test: Take a small quantity of test solution with a drop of 1 N HCl and then add two drops of iodine solution. Formation of blue colour indicates the presence of starch. 

Product from this Experiment :

We got nearly 100 gram of  starch from 500 gm of potato from the above done procedure which will be used further for preparation of bioplastic.

Bioplastic from Strach - Phase 2 : The making of Bioplastic

 

Phase 2:

Theory:

We used potato starch for our research because we reflected about a sustainable use of potato peel, which is often degraded to waste and potato starch is easily accessible in every grocery. Plants store starch in special organelles called amyloplasts which are present in the cells in form of granules to save the energy produced by photosynthesis. 

The glucose produced by photosynthesis forms bonds to grow to a macromolecule following the equation: 

n(C6 H12O6) →(C6H10O5)n+(n-1)H2O

There are two products which can form: amylopectine and amylose. For amylopectine „n“ in the above equation can vary between 2 000 and 200 000, which means that the amylopectine chains are formed by between 2 000 and 200 000 glucose units, which form branchings every 24 to 30 glucose units. For amylose, „n“ varies between 300 and 3000 and there are no branchings in the chain ,in contrary to amylopectine, and, as a consequence, amylose is less soluble in water than amylopectine because its molecules do not link to water molecules via hydrogen bonds. In the image below, the structures of amylose and amylopectine are respresented. The branchings of amylopectine are visible.

 

The potato starch we used contains 70 % amylopectine and 30% amylose.

Glycerin (Propan-1,2,3 triol):

Glycerin is a hygroscopic liquid with a high viscosity. It has 3 hydroxyl groups which make it be soluble in water.

Glycerin makes the biolastic more flexible.

Water: 

Water plays an important role in the production of bioplastic. First, it acts as a solvent to dissolve the starch. Secondly, it helps the starch molecules to stay disrupted after heating.

Acid (Vinegar): Vinegar, a 6% in volume solution of acetic acid liberates acetate ions and hydrogen ions in solution. This is important, because ions react with the starch polymers and make them be disordered more easily in the solution. This disorder, resulting from the disruption by the water and the ionization by the acetic acid, makes the resulting cast film more homogenous. 

Determination of the best water/starch ratio :

We did some tests to find out in which proportion we have to mix water to starch in order to receive a plastic which conforms to our criteria. The plastic has to be flexible, but not too soft.

Solution number	Mass of Water in %	Mass of Starch in %
1	82	18
2	55	12
3	61	13.5

Plastics produced with solution 2 seemed to fit the best to our conditions, so we continued with this proportion for further experiment.

Experimental Procedure:

Aim: To prepare bioplastic sheet from the starch extracted from a specified amount of potatoes.

Materials Required: Extracted starch,glycerine,glacial acetic acid,distilled water,beaker,heating pan,spatulla,measuring flask,aluminium foil.

Procedure: 

1. Weigh 50 gm of starch from our extracted sample.

2. Add it to 250 ml of water with continuous stirring so that no lumps are formed.

3.Add 25 ml of glycerine drop by drop with continuous stirring.

4. Heat the mixture with a heating pan until a dense paste of the above mixture is formed .

5. Spread the mixture on aluminium foil and allow it to dry for 2-3 days.

6. Carefully Peel off the prepared bioplastic from the aluminium foil in order to reduce the wear and tear.

Result : We got a piece of bioplastic of required strength which can be used for our daily purpose. 

Precautions:

1. Addition of starch to water must be done with continuous stirring so that no lumps forms.

2. Glycerine should be added drop by drop otherwise a homogeneous mixture will not be formed.

3. Spread the prepared paste carefully and uniformly over the aluminium foil in order to get bioplastic of constant thickness.

4. Handle the heating pan carefully and the heat provided to the solution must be in a controlled amount.

Conclusion:

All in all, we can say that our produced plastic satisfied our expectations. Now, we are looking for a practical application of this material. Further, we are going to analyze the biodegradability and its strength must be tested to know how much load it can bear before commercial use.

To conclude, the production of starch based plastic film is a viable industry even though for the time ,it will be dependent on petroleum product such as energy resources for the machine operation. However ,the increased  influence of environment concern, use of renewable resources such as starch based plastic products. will be an obligation across the world.

References:

Video sources:

• https://youtu.be/5M_eDLyfzp8

• https://youtu.be/nr6Ks4R3aAM

• https://youtu.be/y1joh_t1thc

• https://youtu.be/nr6Ks4R3aAM

Article sources:

• https://www.academia.edu/27856907/Production_of_bioplastics_using_potato_starch

• Production of Bioplastic by Matthieu Schon and Pit Schwartz.

• https://aaas.confex.com/aaas/2017/webprogram/Paper20402.html

• http://www.mhhe.comnot

• http://green-plastics.net

Forbidden Energy Gap and Temperature Relationship

  Problem : Forbidden Energy Gap of Semiconductor:

1. Increases with temperature

2. Decreases with temperature

3. Slightly increase ,then decrease with temperature

4. Does not change with temperature

Solution : B.  Decreases with Temperature.

Explanation :

We shall be first discussing what actually is a “Forbidden Energy Gap” and then be discussing its variation with change in temperature.

As we know, the Energy band is a concept derived from the Bohr Model of an atom where the energy of an electron is dependent on the orbit in which it is revolving. Since solids have atoms closely packed, so the orbits of any two neighbouring atoms in a crystal may be overlapping and the entire energy model of atoms will be entirely different from those as isolated atoms. 

Every different atom in the crystal has a different energy band and no two electrons will have the same set of surrounding charges or electrons. These different energy levels with continuous energy variation form what are called energy bands. The energy band associated with the energy level of valence electrons of atoms is known as valence band and the energy band above the level of valence band is known as conduction band.

The energy gap or difference in level of energy between conduction band and valence band is known as energy band gap or forbidden energy gap. 

If the electrons in the highest level of valence band are completely bound and there is a sufficient amount of band gap ,the material will act as an insulator.

In the other case, when the lowest level of conduction band lies below the highest level of valence band, means that the forbidden energy gap is zero or electrons may travel freely between the two bands, the material will act as a conductor.

Whenever the electrons in valence band get excitation energy ( maybe thermal ) from an external source ,the electrons jump from valence band to conduction band ,the crystal may act as a semiconductor. Or, it can be said that the energy required for a valence electron to jump to conduction band in  case of semiconductor is forbidden energy gap.

Having clarified the concept of  forbidden energy gap along with its relationship with conductivity of a material, we shall be discussing the temperature variation of Forbidden energy  gap in a much better way.

Forbidden energy gap is the difference between energy of valence electrons and conduction band. If the valence electrons receive some energy from an external source ultimately increasing its energy means the electron’s energy is much nearer to the conduction band.

When the temperature of a semiconductor is increased, the electrons vibrate from their bounded position resulting in electron-hole pairs and mobility. Also ,the energy of the electrons rises in valence band to a much higher orbit or ionize itself if the thermal energy matches ionization energy setting the electron free. So, the electron will require much less energy to jump into the conduction band which means the forbidden energy gap has been reduced upon increasing the temperature.

So the correct option is:

B.  Decreases with Temperature.

Note : It is very important to note here that the valence band energy of an electron will match the Bohr energy of that orbit only at absolute zero temperature. At a temperature higher than absolute zero , the electrons will have some thermal energy which means valence electrons will have higher energy than that of Bohr energy. At absolute zero, the conduction band remains totally empty.

Why does Hydrogen Pop when set on fire ?

 “When set on fire, Hydrogen reacts with nearby air containing oxygen to release a large amount of heat . The release of such heat causes a mini explosion and gives a pop sound’’.

The question is an interesting one to know about , but have you ever thought about the following questions :

What causes the pop sounds ?

What is the chemistry behind burning hydrogen ?

Why is a mixture of hydrogen with air or oxygen in closed containers or balloons dangerous ?

Why is Helium used instead of Hydrogen in balloons ?

There are many more facts to think about which we shall be unfolding in the next few paragraphs.

What does “Set on Fire ” exactly mean ?

For any substance to be set on fire or in common language - burn , 

Three main conditions are required :

a) Substance to be burn

b) Ignition Temperature

c) Oxidizing Medium( Oxygen) 

                    

                                      PicCredit : wright.nasa.gov

In our case , hydrogen is the substance to be set on fire or burnt.

Every substance has a particular temperature above which it reacts with air and undergoes combustion . This temperature is known as ignition temperature. 

It may be high for metals like 1315 ⁰C for Iron and 35 ⁰C for red phosphorus. For hydrogen, it is 585 ⁰C. which means if a test tube containing a mixture of air and hydrogen is heated to a temperature of 585 ⁰C , then it will react and undergo combustion. 

                             

                             PicCredit : physicscatalyst.com

We are constantly talking about air/oxygen and hydrogen mixture for combustion.

In every combustion process ,oxygen present in air reacts with the substance to be burnt to set the fire or combustion.

If we cannot ensure proper supply of oxygen ,the combustion process will not proceed.

At the furnace or oven , everyone of you would have noticed that we blow air towards the burning substance . When burning, every substance produces gases or smoke .These smokes are nothing but oxides of that material ( like CO₂ or CO while burning coal) .These gases act as a blanket on the material burning and stop the inflow of fresh oxygen or air. So, we blow air to remove these gases which act as a blanket and provide a path for fresh supply of oxygen. 

Now , we have covered the basic principle of combustion . Now , we shall be learning about the combustion process of hydrogen .

How does Hydrogen Burn ?

Before moving forward , Think about :

Why do we get heat when we feel cool when sweat is evaporated from our body surface and feel hot during combustion of any fuel like coal ? 

During hydrogen burning , hydrogen reacts with oxygen present in air when heated up to 585⁰ C (ignition temperature) and sets on fire. This reaction is an exothermic process which means heat energy is released during the process .On the other hand, evaporation of water absorbs heat from the surface and lowers the temperature. Such a process is called an endothermic process.

Hydrogen and oxygen molecules react and form water along with heat energy. 

                             

                                             PicCredit :flexbooks.ck.org

Water is an oxide of hydrogen which is produced on combustion of hydrogen  just like CO₂ which is produced on combustion of carbon/coal.

Water and CO₂ both are oxides which cannot be burnt any further in normal conditions and act as a blanket to prevent fresh air. So ,they are used as fire-extinguishing mediums.

Hydrogen has the highest calorific value which means it releases a large amount of heat during the combustion process. It is a highly flammable gas as it can catch fire easily.

                              

                                             Pic Credit : researchgate.net

Now comes the main question :

Why does Hydrogen Pop when set on fire ?

In the last segment, we get to know that a large amount of heat is released when hydrogen is set on fire.

This heat energy increases the temperature of gases and the molecules in particles start moving faster because the kinetic energy of gases increases with increase in temperature of gas. This fast movement causes large expansion of gas in very less or almost negligible amount of time. The molecules fastly try to move out of the test tube and collide with each other causing a mini collision breaking the sound barrier. The pop sound comes as a result of this mini- collision .

            

                     PicCredit: lebanon-express.com

It should be interesting to note that this pop sound comes out when hydrogen is set on fire in a test tube because the heated gas molecules suddenly expands and gets insufficient space due to which they try to  come out  of the small mouth  of the tube causing an explosion .

                             

                                  Pic Credit : teleskola.mt

On the other hand, if hydrogen is heated in open air , the heated molecules will have all directions to move outwards  and does not cause a high pressure zone as in case of tube. The molecules will get sufficient space to expand due to which collision or explosion does not take place .

Applications : 

So far we have learnt about the underlying principle and process involved in Hydrogen popping when set on fire.

Now ,try to think of a few applications of this article in practical life .

1. Presence of hydrogen gas is detected by burning a candle near the hydrogen source like reaction of a metal (Mg)  with an acid (HCl)  . A popping sound will indicate the presence of hydrogen.

                                        

                                            PicCredit : nygh.sg

2. Helium is used in place of hydrogen in gas balloons because Helium is inert gas and does not react with air to cause explosion . 

3. Even while filling hydrogen , we prevent air entering the balloon because air consists of oxygen and can become an oxidizing medium for hydrogen. Without presence of oxygen, burning cannot take place.