PROCESS DESCRIPTION OF STARCH MANUFACTURE

           STARCH MANUFACTURE PROCESS DESCRIPTION

Maize kernels are screened and air cleaned in steeped in SO2 water for 60 to 70 hours at a temperature 50-55 ͦC to prevent bacteria growth. The softened grains are passed through coarse grinder No.1. Coarse grinding is done to separate the germ without breaking or disturbing it because otherwise if fine grinding was done germ would liberate oil and cause further process problem, in a degerminator cone is maintained at about 40 ͦC be at which all germs tend to float and rest of heavy media passes as the under flow to next operation, second coarse milling is done just to ensure the breaking of any uncrushed grain.

All the overflow of the degerminators are collected in the germ tank, and further germ is fed for germ washing, germ dewatering, germ drying, germ expelling and maize oil is collected. 

The underflow from degerminator 3 comes to pin mill feed tank and then to pin mill and then to concave screens that are 50μ and its outlet goes to primary separator (Alfa Calval) and underflow to pin mill again and collected from there to houdi tank and is fed to 75μ screens and screen underflow again goes to primary separator and overflow to stone grinder and then fed to 1 DSM of 120 mesh and remove oversize as byproduct i.e. bran obtained from three stage washing and screw pressing for dewatering.

The underflow of DSM goes to raw material tank and then to series of 3 DSM screens and any overflow left is send to filter press to recover grit or fine bran and underflow of DSM goes to stone grinder again. The underflow is collected in alpha feed tank and are then to primary separator machine which works on density difference and separates light pure yellow gluten as overflow and heavy white slurry which is mixture of both starch and traces of protein (not more than 2%) as underflow.

The overflow is settled in series of large settling tanks. The sediment obtained is thereby pumped to filter press, which gives cake which is flash, dried and converted into dry gluten.

The impure underflow starch slurry is washed in series of hydro-cyclones called as Dorr cyclones. This is counter current washing and thickening station. Total 9 stages are employed in which impure starch and water flows in opposite directions. Water as a overflow collect all the light impurities and impure water collected at the end of the first stage while starch as a underflow becomes pure and thick is collected at the 9th stage at come of 20 oBe. This starch milk is centrifuged to get wet cake, which is further flash dried to get dry starch powder and is finally packed in silos bags.

A Brief Introduction to Starch

                                     INTRODUCTION TO STARCH 

1.1 MOLECULAR STRUCTURE

Chemical formula- (C6H10O5)n

Molecular weight - 162gm/mol

Starch contains both Amylose

                                 Amylopectin

Amylose-

 -is a linear polymer of short 1,4 linked glucose chains.

 -Typically the amylase fraction is about 20-25% of starch molecules found in corn & has a molecular weight of about 250,000. The percentage of amylase in the starch is genetically determined. Genetic modification producing high amylose (50-70%).

Amylopectin-

 - is a branched polymer of the basic repeating units of 1,4 linked glucose with branches of 1,6  linked glucose. The branching occurs approximately one per twenty-five glucose units.

 -comprises about 75-80% of starch and has a molecular weight of about 50-550 million.

1.2 SOURCES OF STARCH

The main sources of starch are staple food as Maize (corn), wheat, rice, potatoes, cassava,

Arrowroot and Sago, etc.

1.3 RAW MATERIALS

-Dry maize -moisture 11-15% by weight

-Plant capacity 150 Ton per Day

-Process water- 6-8 m

-SO2 water – 160-180 grams sulfur per day

-prepared concentration nearly 3600 ppm

-Electricity – 2500 units per ton of grinding

1.4 SPECIAL STARCH PROPERTIES

COMPOSITION

Moisture – (11-15%)

Carbohydrates – (98-99%)

Protein- (0.5-0.7%)

Fiber- (0-0.5%)

Sulfated ash – (0-0.2%)

1.5 APPLICATIONS

Maize starch in its biological function, is used as an anti-agent and a chemical catalyst. The world mohas been aware of the physical properties of the maize starch for a while now, but researchersand scientists all over the world are paying a great deal of the interest to biological aspects of thecomplex carbohydrates, polymers.

Textile Industry

Maize starch has an extensive use in the Indian cotton textile industry. Out of all starches maize starch has the quality to be removed in the first wet process. It therefore can have an individual function at every stage of textile manufacture.

a) It is used as an adhesive to strengthen the wrap yarn by improving its resistance to abrasion while weaving.

b) Maize starch is immensely useful in printing to increase the consistency of the printing paste.

c) It is used as finishing of the material, to change the appearance after it has been dyed, bleached and printed.

d) Thread owes its glaze and bright shine to maize starch

e) Starch solution has very good penetration power and is used as laundry stiffening agent.

Modified starch for the textile industry sizing

During weaving process, yarn is subjected to two kinds of stresses. One is external frictional

stresses and shearing stresses and second is inner structural stresses. An inadequately sized wrap can very often hinder the productivity of even the most efficient automatic loom.

Among sized agent starch maintains its pre-eminence inspire of the development of the synthetic products, starch keeps abreast of all new changes.

Application of sizing grade starch

All staple fibers, be they cotton polyesters mixtures, spun rayon or wool, use sizing grade starches modified starches during the weaving process.

Food Industry

80% of the food diet is supplied by carbohydrates, and starch is rich in it. Food starch manufacture is separation process to obtain powdered starch, which is further used in sweeteners and modified starch products. Food starch therefore plays:

a) They are nutritive stabilizers

b) They are the processing aids used in the manufacture of food stuffs.

c) Modified starches provide uniformity in filling operations for liquid and particulate formulations.

d) The use of pre-gelatinized starches controls the spread of cold flow products in extrusions.

     Examples- gravies, sauces, puddings, chocolates, spreadable salad dressing, canning   diary,confectionary baking, packaged mix, frozen food.

  

Paper Industry

The very crispness of good quality paper depends on maize starch. Besides accounting for a smooth surface texture, stiffness and rattle it increase the paper strength so necessary for the printing.It is needed as ink penetration, sizing purposes, and as a adhesive for coating of pigmented paper.

Adhesive Industry

High strength adhesives, paper glue, wood adhesives, label adhesives, wall paper paste, etc all have a maize starch component. Gelletinized starch is used as binder agent, while a number of adhesives such as dextrin’s and modified starches are used in specific purposes.

Pharmaceutical Industry

Edible starch is being used as binding agent in tablets, etc. besides this physical function it simultaneously acts as a dispersant agent. Starch granules are very easily metabolized in the human body, so even a small amount of medicine absorbed by the granules is quickly dispersed

Crude Stabilization Process Description

Crude Stabilization Process Description

Pressurized Crude Oil coming out from BUT and HUT oil trunk lines into five streams and preheated by steam up to 45^oC before entering into High Pressure Separators operating at pressure of 3.5 kg/cm²g. The oil flows out under level control and can either be directed towards low pressure separator or can be pumped to the Dehydrator system. High pressure gas letup the HP separators under pressure control and is sent for compression.

If, the oil contains water and/or salt it can be dehydrated in the Dehydrator systems. Before entering the Dehydrators, oil is preheated first by heat exchange with dehydrated oil and then in the crude heaters up to 65°C.

The Dehydrators operate at 2.5 Kg/cm²g and at 65°C. The dehydration is accomplished by injection of demulsifies, heating and application of high voltage electro-static field in the oil-water emulsion. The gas liberated in the Degasser of the dehydrator flows under pressure control to the compressors. 

The dehydrated oil, which came from dehydrator system, flows under level control, exchange heat with feed to dehydrator and is then sent Low Pressure Separators. The produced water flows under interface level control and is sent to the Waste Treatment Plant or EPTP (Effluent Pretreatment Plant) for predisposal treatment.

Series operation of dehydrators A and B is also available. The Low Pressure Separators operate at 0.1 Kg/cm²g and 50/55°C. The oil pumped to HSVR cooler flows under level control into the two Intermediate Surge Tanks by gravity where final separation of gas is achieved.

The stabilized oil is pumped to five Main Storage Tanks. From these tanks oil is pumped into the trunk line dispatch oil to the Trombay Terminal for onward distribution to BPCL Refinery, HPCL storage or (Butcher Island Jetty) Jawahar Deep Island.

The gases from HP separators, Degassers and LP Separators are compressed in the Multi service Gas Compressors and sent to LPG unit combining with associated gas from the trunk line. These are 3 stages reciprocating 

Compressors, operating at suction pressures of0.05 Kg/cm²g, 3.0 Kg/cm²g and 14.0 Kg/cm²g respectively with a final discharge pressure of 51.0 Kg/cm²g. The Degassers and LP separator gases are connected to compressor 1st and HP separator gases are connected to 2nd stage suction.

Solution to Stoichiometric Equation

Solution of Stoichiometric Problem

Hello Everyone, So continuing with the last article ‘Introduction to Stoichiometry’, in this article we will learn the steps to solve a stoichiometric equation.

You should take the following steps in solving stoichiometric problems:

1. Make sure the chemical equation is correctly balanced. How do you tell if the reaction equation is balanced? Make sure the total quantities of each of the element on the left hand side equal to those on the right hand side. For example,

CH₄ + O₂  à  CO₂ + H₂O

Is not a balanced stoichiometric equation because there are four atoms of H on the reaction side (left hand side ) of the equation, but only two on the product side (right hand side) of the equation and also oxygen atom do not balance. The balanced equation is given by

CH₄ + 2O₂  à  CO₂ + 2H₂O

The coefficients in the balanced reaction equation have the unit of moles of a species reacting or produced relative to the other species reacting for the particular reaction equation. If you multiply each term in a chemical reaction equation by the same constant, say two, the absolute stoichiometric coefficient in each term doubles, but the coefficients still exist in the same relative proportions.

2. Use the proper degree of completion for the reaction. If you do not know how much reaction has occurred, you have to assume some amount, such as complete reaction.

3. Use molecular weights to convert mass to moles for the reactants and products and vice versa.

4. Use the coefficient in the chemical equation to obtain the molar amounts of products produced and reactants consumed by the reaction.

Steps 3 and 4 can be applied in a manner similar to that used in carrying out the conversion of units, which I guess you all have already read, due to its basic importance in process industry.

‘Valuable suggestions are required and if u have any question please let me know the comment section given below. ‘

Introduction to Desalting of Crude Oil

Now, in this article we will discuss about a very important topic in crude oil distillation which is 'Desalting of Crude Oil'.  

DESALTING OF CRUDE OIL

If the content in the crude oil of salt is greater than 10 lb/1000 bbl (expressed as NaCl), the crude requires desalting to lower fouling and corrosion happen due to deposition of salt on heat transfer surfaces and acids formed by decomposition of the chloride salts. Afterwards, some metals in inorganic components dissolved in water emulsified with the crude oil, which can cause deactivation of catalyst in catalytic processing units, are partially rejected in the desalting process. 

Until lately, the standard for desalting crude oils was 10 lb salt/1000 bbl (expressed as NaCl) or more, but now many companies desalt all crude oils. Shorten equipment fouling and corrosion and longer catalyst life provide justification for this additional treatment. Two-stage de salting is used if the crude oil salt content is more than 20 lb/1000 bbl and, in the situations where residua are catalytically developed, there are some crudes for which three-stage desalting is used. The salt in the crude is in the form of dissolved or suspended salt crystals in water emulsified with the crude oil. 

The main objective or principle is washing the salt from the crude oil with water. Problems occur in obtaining efficient and economical water/oil mixing, water-wetting of suspended solids, and separation of the wash water from the oil. The pH, gravity, and viscosity of the crude oil, as well as the volume of wash water used per volume of crude, affect the separation comfort and competence.

A secondary but important function of the desalting process is the removal of suspended solids from the crude oil. These are usually very fine sand, clay, and soil particles; iron oxide and iron sulphide particles from pipelines, tanks, or tankers; and other contaminants picked up in transit or production. 

Total suspended solids removal should be 60% or better with 80% removal of particles greater than 0.8 micron in size. Desalting is carried out by mixing the crude oil with from 3 to 10 volume% water at temperatures from 200 to 300°F (90 to 150°C). Both the ratio of the water to oil and the temperature of operation are functions of the density of the oil. The salts are dissolved in the wash water and the oil and water phases separated in a settling vessel either by adding chemicals to see through in breaking the emulsion or by developing a high-potential electrical field across the settling vessel to mobilize the droplets of salty water more rapidly. 

Either AC or DC fields may be used or potentials from 12,000 - 35,000 volts are used to promote mobilization. For single-stage desalting units 90 to 95% efficiencies are obtained and two-stage processes achieve 99% or better efficiency.

Introduction to Stoichiometry

STOICHIOMETRY

As we all know that chemical engineers in practicing their profession are differ from other engineers due to their involvement with chemistry. When chemical reaction occur, in contrast with physical change of material such as evaporation or dissolution, you want to be able to predict the mass or moles required for the reaction(s), and the mass or moles of each species remaining after the reaction has occurred.

Reaction Stoichiometry allows you to accomplish this task. The word Stoichiometry (stoi-ki-om-e-tri) derives from two Greek words: stoicheion (meaning ’element’) and metron (meaning ‘measure’). Stoichiometry provides a quantitative means of relating the amount of products produced by chemical reaction(s) to the amount of reactants.

As you already know, the chemical reaction equation provides both qualitative and quantitative information concerning chemical reactions. Specifically the chemical reaction equation provides you with information of two types:

1. It tells you that what substance are reacting (those being used up) and what substance are being produced (those being made).

2. The coefficients of a balanced equation tell you what the moles ratio are among the substances that react or are produced. (In 1803, John Dalton, an English Chemist, was able to explain much of the experimental results on chemical reactions of the day by assuming that reactions occurred with fixed ratios of element).

A chemical reaction may not occur as rapidly as the combustion of natural gas in the furnace, such as, for example, in the slow oxidation of your food, but if the reaction occurs (or would occur), it takes place as represented by a chemical reaction equation.

‘This is the theory part that we have discussed in this article. If you have any type of problem regarding stoichiometry and its concept, do let me know in the comment section below.’

In the next Article, we will discuss ‘How to solve a Stoichiometry problem.’ 

DISTILLATION- HISTORY& BASIC PRINCIPLE

INTRODUCTION TO DISTILLATION

1. The first clear evidence of distillation comes from Greek alchemists working in Alexandria in the first century AD. 

2. Distilled water has been known since 200 AD, when Alexander The Great described the process. Arabians learned the process from the people Egypt and used it extensively in their chemical experiments.

3. Clear evidence of the distillation of alcohol comes from the School of Salerno in the 12th   century. Fractional distillation was developed by Tadeo Alderotti in the 13th century.

4. In1500, German alchemist Hieronrymus Braunschweig published Liber de arte destillandi (The Book of the Art of Distillation) the first book solely dedicated to the subject of distillation, followed in 1512 by a much expanded version.

5.As Alchemy evolved into the science of chemistry, vessels called retorts became used for distillations. Later, copper alembics were invented. These were called pot stills. Today, those stills have been largely supplanted by more efficient distillation methods in most industrial processes.

6. In the early 19th century the basics of modern techniques including pre-heating and reflux were developed, particularly by the French, and then in 1830 a British Patent was issued to Aeneas Coffey for a whiskey distillation column, which worked thoroughly and may be regarded as the archetype of modern petrochemical units.

7. In 1877, Ernest Solvay was granted a United State Patent for a tray column for ammonia distillation and the same and subsequent years saw developments of this theme for oil and spirits.

With the emergence of chemical engineering as a discipline at the end of the 19th century, scientific rather than posteriori methods could be applied.

The developing industry of petroleum in the early 20th century provided the impetus for the development of accurate design methods such as the McCabe-Thiele method and the Fenske equation.

     

     Basic Principles of Distillation

  Separation of components from a liquid mixture via distillation depends on the         differences in boiling points of the individual components. Also, relying on the             concentrations of the components present, the liquid mixture will have various boiling  point characteristics. Therefore, distillation processes rely on the vapour pressure  characteristics of liquid mixtures.

  

  The vapour pressure of a liquid at a particular temperature is the equilibrium pressure   exerted by molecules leaving and entering the liquid surface.

  

     Below are some important points about vapour pressure:     

1. Energy input raises vapour pressure

2. Vapour pressure is related to boiling

3. A liquid is said to ‘boil’ when its vapour pressure equals the surrounding pressure

4. The ease with which a liquid boils depends on its volatility

5. Liquids with high vapour pressures (volatile liquids) will boil at lower temperatures

6. The vapour pressure and hence the boiling point of a liquid mixture depends on the relative amounts of the components in the mixture

7. Distillation occurs because of the differences in the volatility of the components in the liquid mixture

    

     The distillation equipment to achieve the desired aims will generally consist of:

     1. Heating system to evaporate the solvent;

     2. Condensers and coolers;

     3. Fractionating column

     4. Storage both as part of the plant as a still kettle and to hold residue, products and          feed.

Petrochemical Feed Stocks

Feed stocks for petrochemicals

The petrochemical industry in our country had a strong set back at the time of start as there was no proper coupling with growing petroleum industry. 

Even today, to feed our refineries more oil is produced 34 M²t a from ONGC & OIL fields and 45 M² M³ of gas per day and the accompanying gas has no proper utility thus more than 30% of gas being flared. The realization of saving hydrocarbon, though late, has been resulted in creation of a separate wing, Gas Authority of India, to transport the gas. 

Natural gas being one of the best feed gas for Petrochemicals, the technology is expounded in that direction. Besides the field gases like Natural gas, Associated gas, Lean gas, the other gas comprise of refinery gases. 

The refinery gases are obtained from stabilizers, atmospheric columns, and from process unit like crackers, cokers.

The total raw materials scene as usefully utilized in petrochemical industry is listed below;

1. Gases comprising Associated gas, Lean gas, Refinery off gas, Natural gas LPG, Condensate gases.

2. Light liquid Fractions, Natural gas liquid, Naphtha, wild gasoline, Kerosene (Gas oil ranges), reformates.

3. Heavy Liquids

4. Kerosene, Extracts, Residuum, Low Sulphur Heavy Stocks, Fuel Oil etc.

All the above fractions are used selectively for different chemicals and everyone require certain type of purification. The maximum purification required may be perhaps in the case of gases, as the gases are obtained either from a fields or from a process. 

The gas components in most of the cases may be same, but the concentration are purity vary. The utility of a gas mainly lies in the method of purification and degree of purification.

   

Optimization Algorithms- Bounding & Fibonacci Search

As far as these search are concerned, you can't just have solution of equation so simple than this.

So, here is the Algorithm for two of the best method use in Optimization

Bounding Phase Method

Algorithm

Step 1: Choose an initial guess x ⁽⁰⁾ and an increment Δ. Set k = 0.

Step 2: If f(x ⁽⁰⁾ - IΔI) > f(x ⁽⁰⁾ + IΔI), then Δ is positive;

Else if f (x ⁽⁰⁾ - IΔI) < f(x ⁽⁰⁾) < f(x ⁽⁰⁾ + IΔI), then Δ is negative;

Else go to Step 1.

            Step 3: Set x ^(k+1) = x ^(k) + 2^k Δ.

            Step 4: if f (x ^(k+1)) < f(x ^(k)), set k = k+1 and go to step 3;

Else the minimum lies in the interval (x ^(k-1) , x ^(k+1)) and

Terminate.

Fibonacci search method

Algorithm

Step 1: Choose a lower bound a and an upper bound b. Set L= b – a. Assume the desired number of function evaluations to be n. Set k = 2.

Step 2: Compute L_k^* = (F_n-k+1 / F _n+1) L. Set x₁ = a + L_k^* and x₂ = b - L_k^*.

Step 3: Compute one of f(x₁) or f(x₂), which was not evaluated earlier. Use the fundamental region elimination rule to eliminate a region. Set new a and b.

Step 4: is k = n? If no, set k = k + 1 and go to step 2;

Else Terminate.

Recycling of Hydrocarbons(Waste) in Catalytic Cracking

RECYCLING OF HYDROCARBONS IN CATALYTIC CRACKING

Abstract: The possibility of the chemical recycling of waste hydrocarbon fractions, e.g. waste polymers or waste lubricating oils in catalytic cracking was verified in the MAT laboratory test. Linear 1-olefins were used as model compounds simulating products of thermal pre-cracking of waste polyolefins into liquid fraction suitable for admixing to HVGO as standard FCC feed, and products of semi-pilot plant thermal/catalytic cracking of industrial PP wastes were used as possible real feed. Filtered used automotive oil was tested as possible feed to catalytic cracking to chemical recycling. 

A standard FCC catalyst was used in microactivity test at 525°C, introduction time of 40 s and catalyst/feed ratio of 4.76 g/g. No negative effect in coking was observed as consequence of olefinic fraction adding to hydrogenated VGO feed. Similarly, the use of thermally/catalytically precracked fraction in pilot-plant treatment of industrial polypropylene wastes showed good possibility of chemical recycling of waste polyolefines in FCC process into gases and gasoline fraction. Catalytic cracking of used automotive oil increased conversion to gases and gasoline with little increase of Gas Factor after longer use of this oil. Results showed good possibility for chemical recycling of waste polymers and waste lubricating oils in FCC technology into gases and gasoline. Keywords: waste plastics;

CHEMICAL RECYCLING OF WASTE HYDROCARBONS:

Waste hydrocarbons represent a serious problem in everyday life. The greatest quantities of waste hydrocarbons are mainly waste plastics and also used lubricating oils. Both these wastes come from crude oil and even if both could be used for energy production by incineration, the best way for they treatment should be the material or chemical recycling. Polymer wasted could be regarded as potential source of chemicals and energy. Different methods of polymer wastes recycling are developed [1,2]. One of the most attractive ways is chemical recycling that converts waste polymers into basic monomers or petrochemicals. About 60-70% of waste polymeric materials are composed of PE and PP that cannot be easily converted into monomers. 

For chemical recycling of waste polymers a thermal or catalytic method could be applied, by which the long alkyl chains of polymers are broken into a mixture of lighter hydrocarbons [3-20]. One of the most appropriate chemical recycling of used polyolefins is fluid catalytic cracking process that could convert waste polyolefines directly into fractions of light olefins and motor fuels. The main problem is the state of waste polyolefines – they are available in form of greater or smaller pieces or in powder – all as solids which could not be simply added to FCC feed – hydrogenated WGO. The best way to introduce the polyolefin feed to FCC process is admixing of thermally depolymerizated polymers in liquid state to the base FCC feed – hydrogenated vacuum gas oil. 

The research in this waste plastics, used oils, catalytic cracking field is focused to use of solid acid catalysts as natural or synthetic zeolites. To the main types of reactors used for the laboratory catalytic depolymerization belong batch reactor [4-6] but examples from flow-type reactors are known [7-9]. Many experiments were carried-out in thermobalances (TGA) with mixtures of about 10 wt. % of catalyst with plastics The best possibility gives laboratoty simulation of fluidized-bed reactors [3, 17-19] of MAT-tests. As heterogeneous catalysts, different mesoporous acid catalysts as conventional amorphous alumosilicates [4] and different microporous molecular sieves – zeolites of types USY [6,7,12,15,16], ZSM-5, [4-7,10-15,19] BEA [10], MOR [10] as well as mesoporous molecular sieves of MCM-41 type [8,13,14,19,20], and commercial FCC catalysts [3,15-18] were tested. 

Generally, the catalytic depolymerization is carried out over acid catalysts in atmosphere of nitrogen or other inert gas. Consequently, the cracking products are strongly non-saturated, and catalysts are deactivated because of coking. Catalytically pre-cracked polyolefines contain mainly linear and branched unsaturated and alkane molecules and aromatics. The olefins in feed represent the main different between such feed for FCC and standard feed for FCC, represented by HVGO. The paper deals with the study of the treatment of liquid and solid waste hydrocarbons – mainly waste plastics and waste lubricating oils – in catalytic cracking processes of treatment of petroleum fractions- FCC mainly to fraction of gases and motor fuels – gasoline. 2.

EXPERIMENT: In the present work the influence of additives of model compounds, representing examples of thermally depolymerizated polyethylene, were studied. As model compounds were used 1-olefines C6–C24 pure and in 10% additives to standard FCC feed – hydrogenated vacuum gas oil. Tests were carried-out in Micro-Activity Test (MAT) at 525°C. The treatment of long 1-olefins increases the total micro-activity values - conversion to gases and gasoline. As industrial example of pre-cracked polymer wastes, liquid product of thermal decomposition of polypropylene wastes in Blowdec process [21] was studied. As feed representing waste oils was tested used lubricating oil from diesel engine in bus.

Feeds: A) Hydrogenated Vacuum Gas Oil (HVGO) As feed for MAT was used a standard refinery feed for FCC from refinery - hydrogenated vacuum gas oil (HVGO). Its basic properties are summarized as

Properties of hydrogenated vacuum gas oil (HVGO): viscosity at 50°C- 43.41 mm2 /s, density (20°C)- 906 kg/m3,viscosity at 100°C-8.436 mm2 /s,melting point 40°C ,sulphur 0.033 wt. % ,nitrogen 1002 ppm wt. 10% vol,nickel 0.01 ppm wt,30% vol. vanadium ,0.07 ppm wt,50% vol. sodium 0.01 ppm wt. 70% vol. iron 0.22ppm wt. 90% vol. 541°C ED 555°C

Pure LAO - Linear alpha-olefins (Spolana Neratovice, Czech republic) with the carbon chain of 6, 8, 10, 12, 14, 16, 18, 20-24, were used as model compounds of the polyolefins thermal depolymerization. The purity of LAO was 98.4 % wt. C) Mixture of 10 wt. % of individual LAO in HVGO was prepared by mechanical mixing of HVGO and LAO at temperature of 50°.

Generally, the catalytic depolymerization is carried out over acid catalysts in atmosphere of nitrogen or other inert gas. Consequently, the cracking products are strongly non-saturated, and catalysts are deactivated because of coking. Catalytically pre-cracked polyolefines contain mainly linear and branched unsaturated and alkane molecules and aromatics. The olefins in feed represent the main different between such feed for FCC and standard feed for FCC, represented by HVGO. 

The paper deals with the study of the treatment of liquid and solid waste hydrocarbons – mainly waste plastics and waste lubricating oils – in catalytic cracking processes of treatment of petroleum fractions- FCC mainly to fraction of gases and motor fuels – gasoline. 2 mg/kg Mg 238 mg/kg Fe 61.1 mg/kg Al 25.8 mg/kg 2.2. Catalytic test For laboratory catalytic cracking tests of above-mentioned feeds was used microactivity test (MAT) according to ASTM D-3907-92 [22]. Reaction conditions in MAT: Temperature: 525°C Catalyst weight: 4.00 ±0.005 g Introduction time: 40 s Catalyst/Feed: 4.76 g/g Total flow of nitrogen: 30 ml/min 2.3. Catalyst As cracking catalyst, a commercial equilibrated FCC catalyst from refinery was used with acidity value by TPDA of 0.150 mmol of acid center/gram and surface area of 140 m2 /g. The main characteristics of used FCC catalyst are in Table 4, its SEM picture is in Figure 1. Before MAT tests, 4 g of catalyst was calcined at 560 °C for 3 hrs.

Cooling Tower Performance and Assessment

Now, after discussing about Components of Cooling Tower in the last Blog. Now, we will discuss about it's performance and performance assessment.

Cooling tower performance

The important parameters from point of determining the performance of cooling towers are illustrated in figure given below

                                                    Fig  Cooling tower performance chart

i)        “Range” is the difference between the cooling tower water inlet and outlet temperature.

ii)       “Approach” is the difference between the cooling tower outlet cold water temperature and ambient wet bulb temperature. Although, both range and approach should be monitored, the `Approach’ is a better indicator of cooling tower performance. (see Figure ).

iii)     Cooling tower effectiveness (in percentage) is the ratio of range, to the ideal range, i.e., difference between cooling water inlet temperature and ambient wet bulb temperature, or in other words it is = Range / (Range + Approach).

iv)      Cooling capacity is the heat rejected in kCal/hr or TR, given as product of mass flow rate of water, specific heat and temperature difference.

v)       Evaporation loss is the water quantity evaporated for cooling duty and, theoretically, for every 10,00,000 kCal heat rejected, evaporation quantity works out to 1.8 m³. An empirical relation used often is:

        Circulation Rate (m³/hr) * Temp. Difference in ^oC

Evaporation Loss = ----------------------------------------------------------- m³/hr

                                                   675

vi)       Cycle of concentration is the ratio of dissolved solid in circulating water to make up water

vii)     Blow down losses depend upon cycles of concentration and the evaporation losses and is given by relation:

Blow Down = Evaporation Loss / (C.O.C. – 1)

viii)     Liquid/Gas (L/G) ratio, of a cooling tower is the ratio between the water and the air mass flow rates. Against design values, seasonal variations require adjustment and tuning of water and air flow rates to get the best cooling tower effectiveness through measures like water box loading changes, blade angle adjustments.

Thermodynamics also dictate that the heat removed from the water must be equal to the heat absorbed by the surrounding air:

where: L/G = liquid to gas mass flow ratio (kg/kg) T₁ = hot water temperature (⁰C) T₂ = cold water temperature (⁰C) h₂ = enthalpy of air-water vapor mixture at exhaust wet-bulb temperature

(same units as above) h₁ = enthalpy of air-water vapor mixture at inlet wet-bulb temperature (same units as above)

Factors Affecting Cooling Tower Performance

There are some factors which affects the performance of cooling given as below.

Capacity

Heat dissipation (in kCal/hour) and circulated flow rate (m³/hr) are not sufficient to understand cooling tower performance. Other factors, which we will see, must be stated along with flow rate m³/hr. For example, a cooling tower sized to cool 4540 m³/hr through a 13.9^oC range might be larger than a cooling tower to cool 4540 m³/hr through 19.5^oC range.

Range

Range is determined not by the cooling tower, but by the process it is serving. The range at the exchanger is determined entirely by the heat load and the water circulation rate through the exchanger and on to the cooling water.

Range ^oC = Heat Load in kcals/hour / Water Circulation Rate in LPH

Thus, Range is a function of the heat load and the flow circulated through the system.

Cooling towers are usually specified to cool a certain flow rate from one temperature to another temperature at a certain wet bulb temperature. For example, the cooling tower

Cold Water Temperature 32.2^oC – Wet Bulb Temperature (26.7^oC) = Approach (5.5^oC)

As a generalization, the closer the approach to the wet bulb, the more expensive the cooling tower due to increased size. Usually a 2.8^oC approach to the design wet bulb is the coldest water temperature that cooling tower manufacturers will guarantee. If flow rate, range, approach and wet bulb had to be ranked in the order of their importance in sizing a tower, approach would be first with flow rate closely following the range and wet bulb would be of lesser importance.

Performance Assessment of Cooling Towers

In operational performance assessment, the typical measurements and observations involved are:

·        Cooling tower design data and curves to be referred as the basis.

·        Intake air WBT and DBT at each cell at ground level using a whirling pyschrometer.

·        Exhaust air WBT and DBT at each cell using a whirling psychrometer

·        CW inlet temperature at risers or top of tower, using accurate mercury in glass or a digital thermometer.

·        CW outlet temperature at full bottom, using accurate mercury in glass or a digital thermometer.

·        CW outlet temperature at full bottom, using accurate mercury in glass or a digital thermometer.

·        Process data on heat exchangers, loads on line or power plant control room readings as relevant.

·        CW flow measurement, either direct or inferred from pump motor KW and pump head and flow characteristics.

·        CT fan motor amps, volts.

·        TDS of cooling water.

·        Rated cycles of concentration at the site conditions.

·        Observations on nozzle flows, drift eliminators, condition of fills, splash bars etc.

Control of tower air flow can be done by varying methods: starting and stopping (On-Off) of fans, use of two or three speed fan motors, use of automatically adjustable pitch fans, use of variable speed fans.

On-Off fan operation of single speed fans provides the least effective control. Two speed fans provide better control with further improvement shown with three speed fans. Automatic adjustable pitch fans and variable speed fans can provide even closer control of tower cold water temperature. In multi cell towers, fans in adjacent cells may be running at different speeds or some may be on and others off depending upon the tower load and required water temperature. Depending upon the method of air volume control selected, control strategies can be determined to minimize fan energy while achieving the desired control volume of the Cold water temperature.