Pressure Drop Calculation - Karman method

Pressure drop calculation based on Karman method enclosed here....

Karman worksheet attached in Public folder.

http://www.esnips.com/doc/736b0da8-db5c-4581-9cab-48b4a8e6cd74/karman_dp

Experienced - Based Rules of Chemical Engineering

Experienced based rules of chemical Engineering enclosed in a public folder.

Find the link below and make use of it.

http://www.esnips.com/doc/bae3e55b-e6eb-4cc4-8970-f5f3587ce45a/exprules

Father of Chemical Engineering

From the 1700s, sodium and potassium carbonate were in great demand in the manufacture of a wide range of products including glass, soap and textiles. A frenchman, Nicholas Le Blanc, invented a method for converting sea salt into sodium carbonate which was in widespread use by 1810. However, the process produced hazardous by-products including hydrochloric acid, nitrogen oxides, sulphur and chlorine gas, which often escaped or were released to the atmosphere where they damaged public health and the environment.

Widnes in Cheshire in the early 1800s, under the cloud of the Leblanc process the IChemE

A. J. Fresnel developed new, clean chemistry in 1811, but attempts to build large scale factories using it failed until, over 50 years later in 1863, a Belgian, Ernest Solvay applied it in what became known as the Solvay process.
The Solvay process featured an 80 foot tall high-efficiency carbonating tower, in which ammoniated brine was poured down from the top while carbon dioxide bubbled up from the bottom, producing the desired sodium carbonate. The new process operated continuously, free of hazardous by-products and with an easily purified final product. Solvay's process relied on intimate contact between the gas and liquid. Although it was not established as a profession at the time, Solvay's work is thought of as one of the first triumphs of Chemical Engineering.

The Father of Chemical Engineering

George Davis (1850-1907). Founder of the profession the IChemE

In the 1800s, the chemical industry was compartmentalised; plants were designed and run by specialists. George E Davis, adopted as the father of Chemical Engineering, identified broad features in common to all chemical factories. He was author of A Handbook of Chemical Engineering, published a famous lecture series defining Chemical Engineering in 1888 and was founder of the concept of unit operations.
Whilst Chemical Engineering took off as a distinct profession in America, in the U.K. it is only since the second world war that the value of chemical engineers has become truly appreciated. This change has been driven to a large extent by the expansion of the oil industry; the first oil refinery in the U.K., and still the largest, was built by Esso at Fawley after the war. Chemical engineers have subsequently played a key role in the growth of the petrochemical and plastics industries.

Effectively Design Heat Exchangers

Effective design of Heat exchangers not only with calculating LMTD , No of tubes , Heat Transfer Area , Overall Heat transfer coefficient and other process parameters. It is completely depend on the TEMA standards.

Plz visit the Public folder for effective design of Heat Exchangers.......

http://www.esnips.com/doc/c7de17e7-ffb1-4f87-9ca1-f0106ebda06f/Effectively-Design-Shell-and-Tube-Heat-Exchangers/nsnext

Thermodynamics-Steam Turbine

Introduction

A steam turbine is a mechanical device that converts thermal energy in pressurised steam into useful mechanical work.  The original steam engine which largely powered the industrial revolution in the UK was based on reciprocating pistons.   This has now been almost totally replaced by the steam turbine because the steam turbine has a higher thermodynamic efficiency and a lower power-to-weight ratio and the steam turbine is ideal for the very large power configurations used in power stations.   The steam turbine derives much of its better thermodynamic efficiency because of the use of multiple stages in the expansion of the steam.   This results in a closer approach to the ideal reversible process.

Steam turbines are made in a variety of sizes ranging from small 0.75 kW units used as mechanical drives for pumps, compressors and other shaft driven equipment, to 1,500,000kW turbines used to generate electricity.  Steam turbines are widely used for marine applications for vessel propulsion systems.  In recent times gas turbines , as developed for aerospace applications, are being used more and more in the field of power generation once dominated by steam turbines.

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Steam Turbine Principle

The steam energy is converted mechanical work by expansion through the turbine.   Th expansion takes place through a series of fixed blades (nozzles) and moving blades each row of fixed blades and moving blades is called a stage.   The moving blades rotate on the central turbine rotor and the fixed blades are concentrically arranged within the circular turbine casing which is substantially designed to withstand the steam pressure.

On large output turbines the duty too large for one turbine and a number of turbine casing/rotor units are combined to achieve the duty.  These are generally arranged on a common centre line (tandem mounted) but parallel systems can be used called cross compound systems.

Two Turbine Cylinders Tandem Mounted

There are two principles used for design of turbine blades the impulse blading and the reaction blading.

Impulse Blading

The impulse blading principle is that the steam is directed at the blades and the impact of the steam on the blades drives them round.  The day to day example of this principle is the pelton wheel.ref    Turbines.  

In this type of turbine the whole of the stage pressure drop takes place in the fixed blade (nozzle) and the steam jet acts on the moving blade by impinging on the blades.

Blades of an impulse turbine

Velocity diagram impulse turbine stage

z represents the blade speed , V _r represents the relative velocity, V _wa & V _wb- represents the tangential component of the absolute steam in and steam out velocities

The power developed per stage = Tangential force on blade x blade speed.

Power /stage= (V _{w a}  -  V _wb).z/1000 kW per kg/s of steam

Reaction Blading

The reaction blading principle depends on the blade diverting the steam flow and gaining kinetic energy by the reaction.   The Catherine wheel (firework) is an example of this principle.  For this turbine principle the steam pressure drop is divide between the fixed and moving blades.

Velocity diagram reaction turbine stage

z represents the blade speed , V _r represents the relative velocity, V _wa & V _wb- represents the tangential component of the absolute steam in and steam out velocities

The power developed per stage = Tangential force on blade x blade speed.

Power /stage= (V _{w a}  -  V _wb).z/1000 kW per kg/s of steam

The blade speed z is limited by the mechanical design and material constraints of the blades.

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Rankine Cycle

The Rankine cycle is a steam cycle for a steam plant operating under the best theoretical conditions for most efficient operation.  This is an ideal imaginary cycle against which all other real steam working cycles can be compared.

The theoretic cycle can be considered with reference to the figure below.  There will no losses of energy by radiation, leakage of steam, or frictional losses in the mechanical componets.  The condenser cooling will condense the steam to water with only sensible heat (saturated water).   The feed pump will add no energy to the water.   The chimney gases would be at the same pressure as the atmosphere.

Within the turbine the work done would be equal to the energy entering the turbine as steam (h1) minus the energy leaving the turbine as steam after perfect expansion (h2) this being isentropic (reversible adiabatic) i.e. (h1- h2).   The energy supplied by the steam by heat transfer from the combustion and flue gases in the furnace to the water and steam in the boiler will be the difference in the enthalpy of the steam leaving the boiler and the water entering the boiler = (h1 - h3).

Basic Rankine Cycle

The ratio output work / Input by heat transfer is the thermal efficiency of the Rankine cycle and is expressed as

Although the theoretical best efficiency for any cycle is the Carnot Cycle the Rankine cycle provides a more practical ideal cycle for the comparision of steam power cycles ( and similar cycles ).   The efficiencies of working steam plant are determined by use of the Rankine cycle by use of the relative efficiency or efficiency ratio as below:

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The various energy streams flowing in a simple steam turbine system as indicated in the diagram below.   It is clear that the working fluid is in a closed circuit apart from the free surface of the hot well.  Every time the working fluid flows at a uniform rate around the circuit it experiences a series of processes making up a thermodynamic cycle.

The complete plant is enclosed in an outer boundary and the working fluid crosses inner boundaries (control surfaces).. The inner boundaries defines a flow process.

The various identifiers represent the various energy flows per unit mass flowing along the steady-flow streams and crossing the boundaries.  This allows energy equations to be developed for the individual units and the whole plant...

When the turbine system is operating under steady state conditions the law of conservation of energy dictates that the energy per unit mass of working agent ** entering any system boundary must be equal to the rate of energy leaving the system boundary.

**It is acceptable to consider rates per unit mass or unit time whichever is most convenient

Steady Flow Energy Equations

Boiler

The energy streams entering and leaving the boiler unit are as follows:

F + A + h _d = h ₁ + G + hl _b   hence    F + A = G + h ₁ - h _d + hl _b

Turbine

The energy streams entering and leaving the boiler unit are as follows:

h ₁ = T + h ₂ + hl _t    hence   0 = T - h ₁ + h ₂ + hl _t

Condenser Unit

The energy streams entering and leaving the boiler unit are as follows:

W _i + h ₂ = W _o + h _w + hl _c   hence     W _i = W _o + h _w - h ₂ + hl _c

Feed Water System

The energy streams entering and leaving the Feed Water System are as follows:

h _w + d _e + d _f= h _d + hl _f   hence  d _e + d _f = - h _w + h _d + hl

The four equations on the right can be arranged to give the energy equation for the whole turbine system enclosed by the outer boundary

That is ..per unit mass the of working agent (water) the energy of the fuel (F) is equal to the sum of

-  the mechanical energy available from the turbine less that used to drive the pumps (T - (d _e+ d _f)

-   the energy leaving the exhaust [G - A] using the air temperature as the datum.

-  the energy gained by the water circulating through the condenser [W _o - W _i]

-   the energy gained by the atmosphere surrounding the plant Σ hl

The overall thermal efficiency of a steam turbine plant can be represented by the ratio of the net mechanical energy available to the energy within the fuel supplied.   as indicated in the expressions below...

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Turbine Vapour Cycle on T-h Diagram

Steam cycle on Temp - Enthalpy Diagram

This cycle shows the stages of operation in a turbine plant.   The enthalpy reduction in the turbine is represented by A -> B . The reversible process for an ideal isentropic (reversible adiabetic) is represented by A->B'. This enthalpy loss would be (h _g1 - h ₂ ) in the reversible case this would be (h _g1 - h _2s ).

The heat loss by heat transfer in the condenser is shown as B->C and results in a loss of enthalpy of (h ₂- h _f2) or in the idealised reversible process it is shown by B'-> C with a loss of enthalpy of (h _2s- h _f2).

The work done on the water in extracting it from the condenser and feeding it to the boiler during adiabetic compression C-> D is (h _d - h _f2 ) = length M

The energy added to the working agent by heat transfer across the heat transfer surfaces in the boiler is (h _g1 - h _d ) which is approx.( h _g1 - h _f2 )

The Rankine efficiency of the Rankine Cycle AB'CDEA is

The efficiency of the Real Cycle is

Henry's Law and Its Application

Henry's Law:

Henry's law is one of the gas law. At a constant temperature, the amount of a given gas dissolved in a given volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

An everyday example of Henry's law is given by carbonated soft drinks. Before the bottle or can is opened, the gas above the drink is almost pure carbon dioxide at a pressure slightly higher than atmospheric pressure. The drink itself contains dissolved carbon dioxide. When the bottle or can is opened, some of this gas escapes.Because the pressure above the liquid is now lower, some of the dissolved carbon dioxide comes out of solution as bubbles. If a glass of the drink is left in the open, the concentration of carbon dioxide in solution will come into equilibrium with the carbon dioxide in the air, and the drink will go "flat".

Formula and the Henry's law constant

Henry's law can be put into mathematical terms (at constant temperature) as

where p is the partial pressure of the solute in the gas above the solution, c is the concentration of the solute and k_H is a constant with the dimensions of pressure divided by concentration. The constant, known as the Henry's law constant, depends on the solute, the solvent and the temperature.

Some values for k_H for gases dissolved in water at 298 kelvins include:

oxygen (O₂)                    : 769.2 L·atm/mol

carbon dioxide (CO₂)      : 29.4 L·atm/mol

hydrogen (H₂)                  : 1282.1 L·atm/mol

An industrial example for Henry's Law is, Deaerator. A Deaerator is a device that is widely used for the removal of air and other dissolved gases from the feedwater to steam-generating boilers.

The removal of dissolved gases from boiler feedwater is an essential process in a steam system. The presence of dissolved oxygen in feedwater causes rapid localized corrosion in boiler tubes. Carbon dioxide will dissolve in water, resulting in low pH levels and the production of corrosive carbonic acid. Low pH levels in feedwater causes severe acid attack throughout the boiler system. While dissolved gases and low pH levels in the feedwater can be controlled or removed by the addition of chemicals, it is more economical and thermally efficient to remove these gases mechanically. This mechanical process is known as deaeration and will increase the life of a steam system dramatically. Deaeration is based on two scientific principles. The first principle can be described by Henry's Law. Henry's Law asserts that gas solubility in a solution decreases as the gas partial pressure above the solution decreases. The second scientific principle that governs deaeration is the relationship between gas solubility and temperature. Easily explained, gas solubility in a solution decreases as the temperature of the solution rises and approaches saturation temperature. A deaerator utilizes both of these natural processes to remove dissolved oxygen, carbon dioxide, and other non-condensable gases from boiler feedwater. The feedwater is sprayed in thin films into a steam atmosphere allowing it to become quickly heated to saturation. Spraying feedwater in thin films increases the surface area of the liquid in contact with the steam, which, in turn, provides more rapid oxygen removal and lower gas concentrations. This process reduces the solubility of all dissolved gases and removes it from the feedwater. The liberated gases are then vented from the deaerator. With these principles in mind, Sterling Deaerator Company employs a two-stage system of heating and deaerating feedwater. This system reduces dissolved oxygen concentration to less than 0.005 cc/liter (7 ppb), and completely eliminates the carbon dioxide concentration.

Crystallization

Find the page here to know about Crystallization process.

http://www.cheresources.com/cryst.shtml

Is anything there to replace the Heat Exchangers in Process Industry ?

Replacing of Heat Exchangers are possible in Process Industry. Any Process Industry greatly depends on heat exchangers for the recovery of energy through process fluid or utility fluid.

Why replace a heat exchanger?
Documented energy savings of up to 30% have been reported when replacing a shell-in-tube or plate and frame heat exchanger with a direct steam injection heater from Hydro-Thermal. Heat exchangers heat through a metal barrier which absorbs much of the steam's energy. Direct steam injection heaters, on the other hand, are your smart energy investment because they are more energy efficient by using all the industrial steam's energy to heat process fluids or utility water.

What is Direct Contact Steam Injection?

Direct steam injection transfers heat by precisely injecting metered amounts of steam into the process fluid, liquid or slurry. Injecting steam more rapidly and more efficiently transfers heat energy than indirect heat exchangers. Direct contact steam heating uses all of the sensible and latent energy in the steam, providing 100% thermal efficiency. Energy savings can be considerable reductions in the 20% - 30% are common.

Controlling Steam Flow

A Hydro-Thermal steam injection heater is an internally modulated mixing valve that controls both steam flow and mixing. Steam mixing is controlled by an internal stem plug that meters the amount of steam allowed to pass through the nozzle. Internal modulation eliminates the need for an external steam control valve.

Nozzle design ensures constant steam pressure and velocity at the point where steam contacts the liquid or slurry, eliminating the potential for pressure upsets and ensuring smooth heater operation. This feature provides tight temperature control to the process and extraordinary energy efficiency.

Low Maintenance Because of Self-Cleaning Design

The Hydroheater is cleaned by its own turbulent mixing action, so it does not foul or scale. Chemical clean-out is never needed for our heaters, so they save money and lower the environmental impact of harsh cleaning chemicals.  Maintenance time is also greatly reduced.
Thanks to the self-cleaning action these steam heaters have the flexibility to heat slurries containing a high concentration of solids or non-Newtonian liquids.

Compact Design

Hydroheaters and all accessories are compact and installed as part of the piping, requiring less space than heat exchangers or spargers.

Specifying a Direct Contact Steam Heater

To specify a Hydroheater, general information about the process and the fluid properties such as specific gravity, density, solids content, viscosity and whether any abrasive or corrosive products are present must be taken into consideration. Other information needed are flow rates and steam pressures.

More reasons to replace heat exchangers or spargers with a steam injection heater from Hydro-Thermal

• Less maintenance and more up time
  
• Exacting control of required process conditions and temperature
  
• Smaller foot-print
  
• Hydro-Thermal expertise, training, support services and warranty
  

Unlike heat exchangers or spargers, the Hydroheater is engineered specifically for your process conditions and unique application.

*** Application constraints are there.

Pinch Technology

While oil prices continue to climb, energy conservation remains the prime concern for many process industries. The challenge every process engineer is faced with is to seek answers to questions related to their process energy patterns.

Will see about "Pinch Technology"

Meaning of the term "Pinch Technology"

The term "Pinch Technology" was introduced by Linnhoff and Vredeveld to represent a new set of thermodynamically based methods that guarantee minimum energy levels in design of heat exchanger networks. Over the last two decades it has emerged as an unconventional development in process design and energy conservation. The term ‘Pinch Analysis’ is often used to represent the application of the tools and algorithms of Pinch Technology for studying industrial processes.

Basic Concepts of Pinch Analysis

Most industrial processes involve transfer of heat either from one process stream to another process stream (interchanging) or from a utility stream to a process stream. In the present energy crisis scenario all over the world, the target in any industrial process design is to maximize the process-to-process heat recovery and to minimize the utility (energy) requirements. To meet the goal of maximum energy recovery or minimum energy requirement (MER) an appropriate heat exchanger network (HEN) is required. The design of such a network is not an easy task considering the fact that most processes involve a large number of process and utility streams.With the advent of pinch analysis concepts, the network design has become very systematic and methodical. 

A summary of the key concepts, their significance, and the nomenclature used in pinch analysis is given below:

• Combined (Hot and Cold ) Composite Curves: Used to predict targets for

• Minimum energy (both hot and cold utility) required,

• Minimum network area required, and

• Minimum number of exchanger units required.

• DTmin and Pinch Point: The DTmin value determines how closely the hot and cold composite curves can be ‘pinched’ (or squeezed) without violating the Second Law of Thermodynamics (none of the heat exchangers can have a temperature crossover).

• Grand Composite Curve: Used to select appropriate levels of utilities (maximize cheaper utilities) to meet over all energy requirements.

• Energy and Capital Cost Targeting: Used to calculate total annual cost of utilities and capital cost of heat exchanger network.

• Total Cost Targeting: Used to determine the optimum level of heat recovery or the optimum DTmin value, by balancing energy and capital costs. Using this method, it is possible to obtain an accurate estimate (within 10 - 15%) of overall heat recovery system costs without having to design the system. The essence of the pinch approach is the speed of economic evaluation. 

• Plus/Minus and Appropriate Placement Principles: The "Plus/Minus" Principle provides guidance regarding how a process can be modified in order to reduce associated utility needs and costs. The Appropriate Placement Principles provide insights for proper integration of key equipments like distillation columns, evaporators, furnaces, heat engines, heat pumps, etc. in order to reduce the utility requirements of the combined system.

• Total Site Analysis: This concept enables the analysis of the energy usage for an entire plant site that consists of several processes served by a central utility system.

How a Centrifugal Pump works

This is the basic requirement for chemical engineers to know about centrifugal pump operation and its principles, This will be even useful when you go for interview.

A centrifugal pump is a kinetic device. Liquid entering the pump receives kinetic energy from the rotating impeller. The centrifugal action of the impeller accelerates the liquid to a high velocity, transferring mechanical (rotational) energy to the liquid. That kinetic energy is available to the fluid to accomplish work. In most cases, the work consists of the liquid moving at some velocity through a system by overcoming resistance to flow due to friction from pipes, and physical restrictions from valves, heat exchangers and other in-line devices, as well as elevation changes between the liquid's starting location and final destination. When velocity is reduced due to resistance encountered in the system, pressure (P) increases. As resistance is encountered, the liquid expends some its energy in the form of heat, noise, and vibration in overcoming that resistance. The result is that the available energy in the liquid decreases as the distance from the pump increases. The actual energy available for work at any point in a system is a combination of the available velocity and pressure energy at that point.

Head

Head (H) is the term that is used to define the energy supplied to the liquid by the pump. It is independent of the type of liquid being pumped. Head is expressed in Feet or Meters. In the absence of any velocity, it is equal to the height of a static column of liquid that could be supported by the pressure (P) at a given point in the system. In practice, pressure is usually measured by a pressure sensing device such as a gage or pressure transducer. Head (H) is the ratio of pressure to the Density (Specific weight) of a liquid. For water at 60^oF, head (H) may be calculated, from a pressure reading, using the following equation:

This may be simplified to H = P * 2. 31. The units cancel out so that only feet remain. For a liquid with a Density other than water, divide by the specific gravity of the liquid.

Because specific gravity is an index number (dimensionless) the units remain as feet of head.

Flow Rate

Flow rate is determined by the impeller geometry and its rotational speed. Pump designers manipulate the impeller vane design to achieve an optimum throughput velocity for an impeller. The throughput velocity (ft/sec) multiplied by the usable area of the impeller inlet (ft²) yields the flow rate (ft³/sec). Every impeller has one optimum design flow rate for a given speed and diameter. This is the best efficiency point of the pump. At other flow rates there will be a mismatch between the vane angle at the pump inlet and the flow rate, resulting in increased turbulence and loss of efficiency within the pump.

Total Dynamic Head

Total Dynamic Head (TDH) is the difference in head between the pump outlet and inlet. In actual practice, readings must be corrected for piping losses, gauge location and differences in pipe diameters between the pump inlet and outlet; all unique to the specific pump/system setup.

Pump Efficiency

Pump efficiency is the ratio of hydraulic horsepower to the brake horsepower required to drive the pump. Hydraulic horsepower is the kinetic power available at the pump discharge. It is calculated by the following equation.

Brake horsepower is measured at the pump input shaft by a torque-meter coupling or similar device. The difference between brake horsepower and hydraulic horsepower is the amount of power consumed by mechanical losses, noise, heat, viscous drag, and internal recirculation.

Characteristic Curves

Curves are available from pump manufacturers that depict the ‘as new’ performance characteristics for any given pump model. These may be either generic catalog curves that represent typical values, or they may be test curves that show the actual performance of a customer’s particular pump unit. Performance curves show plots of TDH, Efficiency, BHP and, when specified, NPSHR as functions of flow rate.
The shape of a pump curve is primarily determined by the geometry of the impeller. High flow - low head pumps typically have steeper curves than low flow - high head units.
The performance of a pump when placed in a system is a function of the interaction between the pump and system as defined by their relative characteristics.

Liquefied Natural Gas

Liquefied Natural Gas is emerging technology in this decade. For Chemical Engineers, this will be the good field to learn and earn. I have added some points about LNG here.

LNG is natural gas (Predominantly methane) that has been converted into liquid form for ease of storage and transportation.
LNG takes up volume of 1/600th volume of NG. It is odorless, colorless, non - toxic, non - corrosive. Hazards include flammability, freezing and asphyxia.
The li           liquefaction process involves removal of certain components, such as dust, acid gases, helium, water, and heavy hydrocarbons, which could cause difficulty downstream. The natural gas is then condensed into a liquid at close to atmospheric pressure (Maximum Transport Pressure set around 25 kPa/3.6 psi) by cooling it to approximately −162 °C (−260 °F).
The reduction in volume makes it much more cost-efficient to transport over long distances where pipelines do not exist. Where moving natural gas by pipelines is not possible or economical, it can be transported by specially designed cryogenic ( cryogenics is the study of the production of very low temperature (below −150 °C, −238 °F or 123 K) and the behavior of materials at those temperatures. Rather than the familiar temperature scales of Fahrenheit and Celsius, cryogenicists use the Kelvin (and formerly Rankine) scales). sea vessels (LNG carriers) or cryogenic road tankers.
The energy density (Energy density is a term used for the amount of energy stored in a given system or region of space per unit volume, or per unit mass, depending on the context) of LNG is 60% of that of diesel fuel.
Flow path of LNG process:
                                                      Treatment            
  Transportaion -- Condensate removal / Dehydration ; CO2 removal / Mercury & H2S -                     Refrigeration -Liquefaction --Storage & loading -- Transportation

The density of LNG is roughly 0.41 to 0.5 kg/L, depending on temperature, pressure and composition, compared to water at 1.0 kg/L. The heat value depends on the source of gas that is used and the process that is used to liquefy the gas. The higher heating value of LNG is estimated to be 24 MJ/L at −164 degrees Celsius. This corresponds to a lower heating value of 21 MJ/L.

The natural gas fed into the LNG plant will be treated to remove water, hydrogen sulfide, carbon dioxide and other components that will freeze (e.g., benzene) under the low temperatures needed for storage or be destructive to the liquefaction facility. LNG typically contains more than 90% methane. It also contains small amounts of ethane, propane, butane and some heavier alkanes. The purification process can be designed to give almost 100% methane. One of the very rare risks of LNG is Rapid phase transition (RPT is a phenomenon realized in liquefied natural gas (LNG) incidents in which LNG vaporizes violently when being in contact with water causing what's known as a physical explosion or cold explosion. During such explosions there is no combustion but rather a huge amount of energy is transferred in the form of heat from water to the LNG at a temperature difference of about 175 degree Celsius.) which arises from cold LNG being in contact with water

Chemical Engineers Titles

This will be useful when you search jobs in job sites. 


Chemical Engineer can be called by MANY job titles. Here are some job titles related to the Chemical Engineer:

• adhesives engineer
• biochemical engineer
• biotechnical engineer
• chemical engineer
• chemical process engineer
• industrial hygiene engineer
• industrial waste treatment engineer
• liquid fuels engineer
• petrochemical engineer
• polymer engineer
• process control engineer
• project engineer
• pulp and paper engineer
• refinery engineer
• waste treatment engineer

Single molecule's stunning image

Its really stunning image of molecule. See and feel the chemistry in 'U' .

Chemical Engineering Interview questions ???

Friends, here I have attached quite tough questions which is asked in one reputed process industry. Check out the answers for this questions you will get a great idea about basic chemical engineering. try out this!

1. Any idea on recombinant protein expression?
2. Are carbon steel storage tanks appropriate for NaOH solutions?
3. Are fin tubes necessary for steam heating a liquid?
4. Cetane no. and sulphur required in diesel fuel for euro-IV
5. Do you have recombinant protein expression experience? Explain?
6. Explain              the Deacon reaction?
7. Explain various protein purification techniques?
8. For a centrifugal pump if the pump is running and we close the discharge valve what is the effect
9. How are plate heat exchangers used in an ammonia refrigeration system?
10. how can we derive power factor equation p=vi cos phi? derivation?
11. how can we measure entropy?
12. how FOULING effectd the heat transfer rate
13. How much experience you are having in commercial software for protein design?
14. how much maximum power can be generated by 320v, 10kg-cm synchronus motor if shaft is roteted mechanically at 50 to 60 rpm?
15. how to calculat suction head in centrifugal pump?
16. How to calculate the release flowrates from pressurized gas systems?
17. How to calculate the sonic velocity of a gas stream?
18. How to determine the particle size distribution for a given bulk solid?
19. How to estimate the efficiency of a pump?
20. Is it possible to compare the resistance to chloride attack of several materials of construction?
21. Is petroleum a mixture of hydrocarbon?
22. Name of the fraction at which benzene xylene and toulene is obtained during coal tar distillation
23. Thyristor related applications
24. What are some good estimates for heat transfer coefficients for coils in tanks?
25. What are the affinity laws associated with dynamics pumps?
26. What are the effects of oils on the properties of Polyolefins?
27. what are the precautions u are taking while starting HT motors?
28. What are the steps involved in w.ine making?
29. What can cause bulk solids to stop flowing from a bin?
30. What compounds are responsible for the odours that come from wastewater treatment plants?
31. What does the catalystic converter on an automobile do?
32. What is a good estimate for the absolute roughness for epoxy lined carbon steel pipe?
33. What is are the main terms in Unit Operations? and what is its charecteristics?
34. What is difference between Overall heat transfer coeficient & individual heat transfer coefficient
35. what is load and what are the types of load?
36. what is meaning of pid how it is useing controlers
37. What is Pinch Technology?
38. what is the apt definitions for apparent power ,active power and reactive power?and explanation about different types of lamps?
39. what is the differance between Horizental and vertical heat exchanger?
40. what is the discharge pressure formula, for calculating discharge pressure?
41. What is the ignition temp. of Alluminium,Coper & Iron.
42. What is the ignititon temprecher of Diesel,Petrol & Carosion oil.
43. What is the Import Procurement Cycle ? and what are the customization steps in SAP ?
44. what is the meaning of flaring
45. What is the most common cause of solid size segregation in bulk solid systems?
46. what is the purpose of capacitor? and capacitor load means what? how does it connect?
47. What is the reason for removing silicon from aluminum?
48. What is the speed of a rotary drier
49. What is the symbol of sodium ?
50. What is the various utilities of the process plant?
51. What is unit operation?
52. What regulates, or gives a substance the viscosity it has?
53. What steps can be taken to avoid stress corrosion cracking (SCC) in steel vessels used for storing anhydrous ammonia?
54. Which is more effective , a single extraction with a large volume of solvent or several small volume extractions? Explain.
55. Which reformer efficiencywise best?
56. Which thing is responsible for making petroleum?
57. Why is post-weld heat treatment sometimes necessary for welded vessels?
58. Why is steam added into the cracker in thermal cracking
    

History of Petroleum and Its Constituents

HISTORY OF PETROLEUM

ORIGIN

Most theories concerning the origin of petroleum postulate and vegetable origin with a close relationship to coal. Theory holds that any organic matter may be converted into petroleum under suitable conditions. There is also general agreement that petroleum was formed from organic matter near shore and in marine deposit deficient in oxygen and associated with minerals converted by time and pressure into limestone, dolomites, sand stones and similar rocks. The concentration of organic matter in original deposits may not have been high but petroleum gas and liquids have migrate and gather in places favoring in retention, e.g., sealed of porous sand stones over long period of times, carbohydrates and proteins have probably destroyed by bacterial action leaving the fatty oils which more refractory to bacterial or chemical destruction.

EXPLORATION

At one time drilling for petroleum was a hit or fewer affairs and only one out of hundred wildcat wells struck oil. Geophysical and seismic work has become highly refined and when combined with high-speed computers to evaluate the vast amount of data used to locate sites. By 1962 one out of 9 wells drilled produced oil, gas or both. Today’s success rate is even better. Geologist recognized at an early date that petroleum accumulates in pools caught in the anti clinical folds of sedimentary rocks.

Seismic analysis can determine the presence of domes and deposits at a considerable depth below the surface. The top of the arch of an anticline or dome is compressed and has greater density than the surrounding rocks. Creating small seismic waves and measuring the reflected waves at intervals in space and time makes possible accurate gravimetric the finding of new field is a most serious and expensive undertaking. At scientifically selected sites, wells have been drilled deeper than 6500 m to meet gas or oil.

CONSTITUENTS OF PETROLEUM

          
Crude petroleum is made up of thousands of different chemical substances including gases, liquids and solids and ranging from methane to asphalt. Most constituents are hydrocarbons but there are significant amounts of compounds containing nitrogen (0-0.5%), sulfur ( 0-6% ) and oxygen ( 0-3.5% ).

ALIPHATICS OR OPEN CHAIN HYDROCARBONS

n-paraffin series or alkanes C_nH_2n+2

This series comprises a larger fraction of most crude than any other. Mo0st straight run gasoline is predominantly n-paraffins. These materials have poor anti-knock properties.

(E.g., n-heptane knocks badly)

iso-paraffin series or iso-alkanes C_nH_2n+2

These branched chain materials perform better in internal combustion engines than n-paraffins and hence considered more desirable. They may be formed by catalytic reforming alkylation, polymerization, and isomerization only small amounts exist in crudes.

 (E.g., 2 and 3 methyl pentane)

Olefin or alkene series C_nH_2n

This series is actually absent in crudes but refining processes such as cracking (making smaller molecules from larger ones) produce them these relatively unstable molecules improve the anti-knock properties of gasoline, although not as effective on storage they polymerize and oxidize this tendency to react, however, makes them useful for forming compounds (petro-chemicals) . (E.g., ethene, propene, butene)

PROCESS OF REFINING

Refining is a low cost operation compared to most chemical processing. Refining involves two major branches.

They are:

ü Separation process

ü Conversion process

Particularly in the field of conversion, there are literally hundreds of processes. Among them they are alkylation, polymerization, and isomerization, reforming, hydrogenation, de-hydrogenation.

Refineries where originally batch units with cylindrical under fired shell stills operated at topping units pumping oil continually through heaters known as pipe or tube stills and separating the constituents in continues fractionating columns. They separate many fractions between gas and asphalt. Primary separation followed by various conversion processes designed to optimize yields of more profitable and salable products the maximum yield is gasoline.

ENERGY CHANGES

                For many years, energy expense for refining has been the most important manipulatable cost. Conservation of heat has been the object of concentrated study. Since the sharp increase the cost of energy, this study has been intensified. The great needs of the growing petroleum industry led to the careful study of fluid flow, heat transfer, and the properties of petroleum fractions.

SEPARATION PROCESSES

          The unit operations used in the petroleum refining is the simple, usual once, but the interconnections and interaction may be complex. Most major units are commonly referred to as stills. Crude still consists of heat exchangers, a furnace, a fractionating tower, steam strippers, condensers, coolers and auxiliaries. These are usually working tanks for temporary storage tanks at the unit. For the refinery as the whole boiler house and usually electrical generating system are added. Control room with instruments to measure, record, and control thus keeping track of material which permits heat and material balances.

The following unit operations are extensively used in separating section

FLUID FLOW

The fluid flow is an operation that must not permit any unexpected failure because fire and explosion may ensure.

HEAT TRANSFER 

          Heat transfer coefficients change daily as fouling occurs. Cooling towers become less effective with time.

DISTILLATION

          When side streams withdrawn, they contain undesirable light volatiles, which are usually removed in small auxiliary steam stripping. Tower contacting material, at one time all packing or bubble caps, now consist of variety of tower packing and special trays design to reduce pressure drop while increasing vapor - liquid contact.

ABSORPTION

          It is generally used to separate high-boilers from wet gases. Gases, which are expelled from gas storage tanks as a result of solar, heating, are also sent to absorption plant for recovery. Steam stripping is generally used to recover the light hydrocarbons and restore the absorption capacity of the gas oil.

ADSORPTION

          It is used for recovery of heavy metals from gases. Adsorbents such as activated charcoal and molecular sieves are used. Molecular sieves can select the materials recovered by molecular shapes as well as molecular weights; this can be very useful. Energy can be saved by using a pressure swing absorption process wherein the material is released from the adsorbent by changing the system pressure.

FILTRATION

          It is used to remove wax precipitated from wax-containing distillates. If the cold cake is allowed to warm slowly, the low melting oils drain (Sweat out) from the cake and further purify it.

CRYSTALISATION

          Before filtration, waxes must be crystallized to suitably sized crystals by cooling and stirring. Waxes undesirable in lubes are removed and become the microcrystalline waxes of commerce. For most purposes this operation is both slow and expensive.

EXTRACTION

          It is removal of a component by selectively dissolving it in a liquid. This procedure is very important in preparing high quality lube oil. Then low viscosity index waxes; color bodies and sulfur compounds are removed in this way.

CONVERSION PROCESSES

          The following are the examples of the more important basic reactions, which are

CRACKING or PYROLYSIS

          The breaking down of large hydrocarbon molecules into smaller molecules by heat or catalytic reactions. Zeolites catalysts are common. Other types are also used.

POLYMERIZATION

          The linking of similar molecules, the joining together of light olefins

ALKYLATION

          The union of an olefin with an aromatic or paraffinic hydrocarbon.

Unsaturated +Iso-saturated à saturated branched chain                              e.g., catalytic alkylation

HYDROGENATION

          The addition of hydrogen to an olefin.

HYDROCRACKING

                   C ₇H₁₅ C₁₅ H₃₀.C₇ H ₃₀+H₂O ==> C₇H₁₆+C₇H₁₆+C₇H₃₂ 

 ISOMERIZATION

          Alteration of the arrangement of the action in molecule without changing the number of atoms.

REFORMING or AROMATIZATION

          The conversion of naphtha to obtain the products of higher octane number similar to cracking but more volatile charge stocks is used.  Catalysts usually contain rhenium, platinum or chromium.

ESTERIFICATION AND HYDRATION

C₂H₄+H₂SO₄ == > C₂H₅O.HO.SO₂+ ( C₂H₅O)_{2  .} SO₂

C₂H₅O.HO.SO₂+ ( C₂H₅)2O.SO₂+H₂O=== > H₂SO₄      (DILL)+C₂H₅OH+C₂H₅OC₂H₅

PRODUCTS OF DISTILLATION

Distillation of the crude oil yields number of products of varying boiling ranges. These fractions are processed to suitable utilities.

NATURAL GAS

          Contains mainly varying proportions of methane. It may be accompanied by other dry gas fractions like ethane and propane.

GASOLINE

          Following the gas, it is the next fraction. It is a volatile fraction and is known as Motor Spirit. The boiling points ranges from 37­­­­ ⁰c to 180 ⁰c. Gasoline is a finished product, while raw fractions are known as naphtha.

          There are 40 types of gasoline products produced by refineries. Automobile industry and the rest exclusively consume 90% of them by aviation industry.

ADDITIVES

          Different types of additives are blended into gasoline to give uninterrupted and smooth service:

ü Anti-icings &detergents

ü Corrosion and oxidation inhibitors

ü Combustion aids

ü Anti-knocks

ü Colors and dyes

AVIATION TURBINE FUELS

          Modern jet engines use fuel similar to the kerosene. It is a most flexible fuel in its boiling ranges.

AVIATION GASOLINE

          Gasoline containing all the additives is generally meant for motor gasoline.

NAPHTHA

These fractions are highly volatile and fall in the boiling range of motor spirit. These are mostly used as travel.

KEROSENE

          Kerosene is the general name applied to the group of refined petroleum fractions. Employed as fuel and illuminant. All these fractions have approximate boiling range   150 ⁰c to 250 ⁰c . These are uniform low distillates, low in viscosity, with a good degree of refinement to be fairly stable, light in color and free from smoky, ill smelling substances.

DIESEL FUEL

          Diesel oil is the fraction in the boiling range of 250 ⁰c to –320 ⁰c and fall under gas oil fractions. They are basically divided into two classes

ü Low speed diesel

ü High-speed diesel

LUBE OIL

          The principle source of lubricating oil is the fraction that is left after lighter components namely gasoline, kerosene, diesel oil, during crude distillation. Generally lubes have a boiling point above 350 ⁰c and these are obtained as main products from vacuum distillation units.

TRANSFORMER OIL

          These oils are used in electrical industry mainly for insulating and cooling purpose additionally these oils protect the equipment form moisture compared to vegetable or coal distillate oils, petroleum oils, are found to be more suitable because of high viscosity, thermal stability and hydrophobic nature.

BITUMEN

          Bitumen is the residual product obtained from crude distillation unit. It is essentially solid at room temperature and has got very high viscosity.

HISTORY OF PETROLEUM

ORIGIN

Most theories concerning the origin of petroleum postulate and vegetable origin with a close relationship to coal. Theory holds that any organic matter may be converted into petroleum under suitable conditions. There is also general agreement that petroleum was formed from organic matter near shore and in marine deposit deficient in oxygen and associated with minerals converted by time and pressure into limestone, dolomites, sand stones and similar rocks. The concentration of organic matter in original deposits may not have been high but petroleum gas and liquids have migrate and gather in places favoring in retention, e.g., sealed of porous sand stones over long period of times, carbohydrates and proteins have probably destroyed by bacterial action leaving the fatty oils which more refractory to bacterial or chemical destruction.

EXPLORATION

At one time drilling for petroleum was a hit or fewer affairs and only one out of hundred wildcat wells struck oil. Geophysical and seismic work has become highly refined and when combined with high-speed computers to evaluate the vast amount of data used to locate sites. By 1962 one out of 9 wells drilled produced oil, gas or both. Today’s success rate is even better. Geologist recognized at an early date that petroleum accumulates in pools caught in the anti clinical folds of sedimentary rocks.

Seismic analysis can determine the presence of domes and deposits at a considerable depth below the surface. The top of the arch of an anticline or dome is compressed and has greater density than the surrounding rocks. Creating small seismic waves and measuring the reflected waves at intervals in space and time makes possible accurate gravimetric the finding of new field is a most serious and expensive undertaking. At scientifically selected sites, wells have been drilled deeper than 6500 m to meet gas or oil.

CONSTITUENTS OF PETROLEUM

          Crude petroleum is made up of thousands of different chemical substances including gases, liquids and solids and ranging from methane to asphalt. Most constituents are hydrocarbons but there are significant amounts of compounds containing nitrogen (0-0.5%), sulfur ( 0-6% ) and oxygen          ( 0-3.5% ).

ALIPHATICS OR OPEN CHAIN HYDROCARBONS

n-paraffin series or alkanes C_nH_2n+2

This series comprises a larger fraction of most crude than any other. Mo0st straight run gasoline is predominantly n-paraffins. These materials have poor anti-knock properties.

(E.g., n-heptane knocks badly)

iso-paraffin series or iso-alkanes C_nH_2n+2

These branched chain materials perform better in internal combustion engines than n-paraffins and hence considered more desirable. They may be formed by catalytic reforming alkylation, polymerization, and isomerization only small amounts exist in crudes.

 (E.g., 2 and 3 methyl pentane)

Olefin or alkene series C_nH_2n

This series is actually absent in crudes but refining processes such as cracking (making smaller molecules from larger ones) produce them these relatively unstable molecules improve the anti-knock properties of gasoline, although not as effective on storage they polymerize and oxidize this tendency to react, however, makes them useful for forming compounds (petro-chemicals) . (E.g., ethene, propene, butene)

PROCESS OF REFINING

Refining is a low cost operation compared to most chemical processing. Refining involves two major branches.

They are:

ü Separation process

ü Conversion process

Particularly in the field of conversion, there are literally hundreds of processes. Among them they are alkylation, polymerization, and isomerization, reforming, hydrogenation, de-hydrogenation.

Refineries where originally batch units with cylindrical under fired shell stills operated at topping units pumping oil continually through heaters known as pipe or tube stills and separating the constituents in continues fractionating columns. They separate many fractions between gas and asphalt. Primary separation followed by various conversion processes designed to optimize yields of more profitable and salable products the maximum yield is gasoline.

ENERGY CHANGES

                For many years, energy expense for refining has been the most important manipulatable cost. Conservation of heat has been the object of concentrated study. Since the sharp increase the cost of energy, this study has been intensified. The great needs of the growing petroleum industry led to the careful study of fluid flow, heat transfer, and the properties of petroleum fractions.

SEPARATION PROCESSES

          The unit operations used in the petroleum refining is the simple, usual once, but the interconnections and interaction may be complex. Most major units are commonly referred to as stills. Crude still consists of heat exchangers, a furnace, a fractionating tower, steam strippers, condensers, coolers and auxiliaries. These are usually working tanks for temporary storage tanks at the unit. For the refinery as the whole boiler house and usually electrical generating system are added. Control room with instruments to measure, record, and control thus keeping track of material which permits heat and material balances.

The following unit operations are extensively used in separating section

FLUID FLOW

The fluid flow is an operation that must not permit any unexpected failure because fire and explosion may ensure.

HEAT TRANSFER 

          Heat transfer coefficients change daily as fouling occurs. Cooling towers become less effective with time.

DISTILLATION

          When side streams withdrawn, they contain undesirable light volatiles, which are usually removed in small auxiliary steam stripping. Tower contacting material, at one time all packing or bubble caps, now consist of variety of tower packing and special trays design to reduce pressure drop while increasing vapor - liquid contact.

ABSORPTION

          It is generally used to separate high-boilers from wet gases. Gases, which are expelled from gas storage tanks as a result of solar, heating, are also sent to absorption plant for recovery. Steam stripping is generally used to recover the light hydrocarbons and restore the absorption capacity of the gas oil.

ADSORPTION

          It is used for recovery of heavy metals from gases. Adsorbents such as activated charcoal and molecular sieves are used. Molecular sieves can select the materials recovered by molecular shapes as well as molecular weights; this can be very useful. Energy can be saved by using a pressure swing absorption process wherein the material is released from the adsorbent by changing the system pressure.

FILTRATION

          It is used to remove wax precipitated from wax-containing distillates. If the cold cake is allowed to warm slowly, the low melting oils drain (Sweat out) from the cake and further purify it.

CRYSTALISATION

          Before filtration, waxes must be crystallized to suitably sized crystals by cooling and stirring. Waxes undesirable in lubes are removed and become the microcrystalline waxes of commerce. For most purposes this operation is both slow and expensive.

EXTRACTION

          It is removal of a component by selectively dissolving it in a liquid. This procedure is very important in preparing high quality lube oil. Then low viscosity index waxes; color bodies and sulfur compounds are removed in this way.

CONVERSION PROCESSES

          The following are the examples of the more important basic reactions, which are

CRACKING or PYROLYSIS

          The breaking down of large hydrocarbon molecules into smaller molecules by heat or catalytic reactions. Zeolites catalysts are common. Other types are also used.

POLYMERIZATION

          The linking of similar molecules, the joining together of light olefins

ALKYLATION

          The union of an olefin with an aromatic or paraffinic hydrocarbon.

Unsaturated +Iso-saturated à saturated branched chain                              e.g., catalytic alkylation

HYDROGENATION

          The addition of hydrogen to an olefin.

HYDROCRACKING

                   C ₇H₁₅ C₁₅ H₃₀.C₇ H ₃₀+H₂O ==> C₇H₁₆+C₇H₁₆+C₇H₃₂ 

 ISOMERIZATION

          Alteration of the arrangement of the action in molecule without changing the number of atoms.

REFORMING or AROMATIZATION

          The conversion of naphtha to obtain the products of higher octane number similar to cracking but more volatile charge stocks is used.  Catalysts usually contain rhenium, platinum or chromium.

ESTERIFICATION AND HYDRATION

C₂H₄+H₂SO₄ == > C₂H₅O.HO.SO₂+ ( C₂H₅O)_{2  .} SO₂

C₂H₅O.HO.SO₂+ ( C₂H₅)2O.SO₂+H₂O=== > H₂SO₄      (DILL)+C₂H₅OH+C₂H₅OC₂H₅

PRODUCTS OF DISTILLATION

Distillation of the crude oil yields number of products of varying boiling ranges. These fractions are processed to suitable utilities.

NATURAL GAS

          Contains mainly varying proportions of methane. It may be accompanied by other dry gas fractions like ethane and propane.

GASOLINE

          Following the gas, it is the next fraction. It is a volatile fraction and is known as Motor Spirit. The boiling points ranges from 37­­­­ ⁰c to 180 ⁰c. Gasoline is a finished product, while raw fractions are known as naphtha.

          There are 40 types of gasoline products produced by refineries. Automobile industry and the rest exclusively consume 90% of them by aviation industry.

ADDITIVES

          Different types of additives are blended into gasoline to give uninterrupted and smooth service:

ü Anti-icings &detergents

ü Corrosion and oxidation inhibitors

ü Combustion aids

ü Anti-knocks

ü Colors and dyes

AVIATION TURBINE FUELS

          Modern jet engines use fuel similar to the kerosene. It is a most flexible fuel in its boiling ranges.

AVIATION GASOLINE

          Gasoline containing all the additives is generally meant for motor gasoline.

NAPHTHA

These fractions are highly volatile and fall in the boiling range of motor spirit. These are mostly used as travel.

KEROSENE

          Kerosene is the general name applied to the group of refined petroleum fractions. Employed as fuel and illuminant. All these fractions have approximate boiling range   150 ⁰c to 250 ⁰c . These are uniform low distillates, low in viscosity, with a good degree of refinement to be fairly stable, light in color and free from smoky, ill smelling substances.

DIESEL FUEL

          Diesel oil is the fraction in the boiling range of 250 ⁰c to –320 ⁰c and fall under gas oil fractions. They are basically divided into two classes

ü Low speed diesel

ü High-speed diesel

LUBE OIL

          The principle source of lubricating oil is the fraction that is left after lighter components namely gasoline, kerosene, diesel oil, during crude distillation. Generally lubes have a boiling point above 350 ⁰c and these are obtained as main products from vacuum distillation units.

TRANSFORMER OIL

          These oils are used in electrical industry mainly for insulating and cooling purpose additionally these oils protect the equipment form moisture compared to vegetable or coal distillate oils, petroleum oils, are found to be more suitable because of high viscosity, thermal stability and hydrophobic nature.

BITUMEN

          Bitumen is the residual product obtained from crude distillation unit. It is essentially solid at room temperature and has got very high viscosity.