Hemant Pathak

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    NATIONAL FERTILIZERS LIMITED

    VIJAIPUR GUNA (M.P.)

    REPORT ON

    VOCATIONAL TRANING

    At

    (AMMONIA 1 (INSTRUMENTATION))

    SUBMITTED TO SUBMITTED BYMr. D. R. Chowdhary(Chief Manager HRD)Mr. R. P. Gupta(Asst. Manager HRD)

    Hemant Pathak B. Tech (2 nd Year)

    Electronics &Communication

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    ACKNOWLEDGEMENT

    I deeply acknowledge my sense of quietude to honorable Mr. D. R.Chowdhary (Chief Manager HRD) Mr. R. P. Gupta (Asst. Manager HRD)and staff for arranging my vocational training in their esteemed organization.

    I would also like to express my heartily thanks and indebtedness to

    Mr. B. Roy (S. R. Manager)

    Mr. R. Boipai (Manager)

    Mr. Sudesh Kumar (Dy. Manager)

    Mr. Shiv Prasad (Asst. Manager)

    Mr. Anshul Jain (Asst. Manager)

    Mr. A.K. Dwivedi (Asst. Manager)

    For their deep involvement, invaluable suggestion and continues motivationthroughout this period. I am highly obliged to them for always being there inmy needs.

    I cannot escape by giving thanks to all people directly or indirectly helpingme for the completion of my training.

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    AMMONIA PROCESS DESIGN

    Ammonia is produced from a mixture of hydrogen and nitrogen in a proportion of approximately 3:1.

    Natural gas from Gail is used as the major fuel for urea production. Hydrocarbon feed is completely desulphurized in the desulphurization

    section. The desulphurized hydrocarbon is reformed with steam and atmospheric air

    into process gas in the Primary and Secondary Reformer.

    The gas contains mainly hydrogen, nitrogen, carbon monoxide and carbondioxide. After that carbon monoxide is converted to carbon dioxide and hydrogen

    with steam to increase the yield of hydrogen. Then carbon dioxide is then absorbed in GV Section and the sent to

    ammonia synthesis chamber. The remaining carbon dioxide is then converted to methane in methanator

    using hydrogen.

    The purified synthesis gas is compressed to about 220 kg/cm2 and sent tothe ammonia synthesis loop where it is converted into ammonia. This formed ammonia is then sent to urea plant for production of urea or

    sent to ammonia storage unit after passing it from cooling tower (which hasa capacity of storing 10000MT).

    The flow diagram is shown below.

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    CH 4 CO, CO 2, H 2

    CO 2, H 2, N 2 CO, CO 2, H 2, N 2

    H 2, N 2

    Desulphurizationtank

    NaturalGas form

    GAIL

    PrimaryReformer

    Secondary

    Reformer

    GVSection

    CO to CO2Converter

    Steam

    Atmospheric

    Air

    Absorbed CO2 to UREAPLANT

    SynthesisCompressor NH3 Reactor

    Ammonia to Urea Plant orto Storage Unit

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    INSTRUMENTATION

    The Technology of using instruments to measure and control the chemical and physical properties of materials is called Instrumentation.

    It is a tool for efficient plant operation in any process industry. Efficiency meansincreased productivity, cost reduction and increased profitability of operation.When the instruments are used for the measurement and control of industrialmanufacturing conversion process is known as process instrumentation.

    The role of instruments in particularly very pivotal in a fertilizer industry.Where instruments has to keep pace with the new developments to measure ,record, analyze and control the highly complex chemical reaction, unit operationtaking place at high pressure and temperature.

    Process plant consists of hundreds or even thousands of control loops allnetworked together to produce to be offered for sale. Each of these is controlledwithin a required operating range to ensure the quality of the end product. Each of these loops receives and internally creates disturbance that detrimentally affect the

    process variables and interaction from other loops in the network providesdisturbances that influence the process variable.

    To reduce the effect of these load disturbance sensor the transmitter collectinformation about the process variable and relationship to some desired set point.

    This simple process control loop consists of these elements:-

    1. Sensing2. Measurement3. Controlling element

    4. Final control element

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    MEASUREMENT

    Measurements have got to be one of the most important equipment in any processing plant. Any decision made on what the plant should do is based on what

    the measurement tell us.It is the integrated approach of application of knowledge, skill, standard practicesto keep all the equipments / Instruments in healthy condition with their reliability,accuracy, for efficient & trouble free optimum operation of the plant

    In the context of process control, all controller decision is similarly passedon measurement. This section is going to deal with the instrument equipmentnormal used to measure and provide signals. We will look at the measurement of these process parameters.

    Pressure Flow Level Temperature Vibration

    PRESSURE

    General Theory

    Pressure is probably one of the most commonly measured variables in the process plant. It includes the measurement of steam pressure; feed water pressure,condenser pressure, process fluids, lubricating oil pressure and many more.Pressure is actually the measurement of force acting on area of surface. We couldrepresent this as:

    The units of measurement are either in pounds per square inch (PSI) in Britishunits or Pascals (Pa) in metric. As one PSI is approximately 7000 Pa, we often usekPa and MPa as units of pressure.

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    Pressure Measurement

    The object of pressure sensing is to produce a dial indication, control operation or a standard (4 - 20 mA) electronic signal that represents the pressure in a process.

    Common Pressure Detectors

    Bourdon Tubes

    Bourdon tubes are circular-shaped tubeswith oval cross sections. The pressure of the medium acts on the inside of the tube.The outward pressure on the oval crosssection forces it to become rounded.

    Because of the curvature of the tube ring,the bourdon tube then bends as indicated inthe direction of the arrow.

    Due to their robust construction, bourdonare often used in harsh environments andhigh pressures, but can also be used for very low pressures; the response timehowever, is slower than the bellows or diaphragm.

    Differential Pressure Transmitters

    Most pressure transmitters are built around the pressure capsule concept. They are usually capableof measuring differential pressure (that is, thedifference between a high pressure input and a low

    pressure input) and therefore, are usually called DPtransmitters or DP cells. Figure illustrates a typicalDP transmitter. A differential pressure capsule is

    mounted inside housing. One end of a force bar isconnected to the capsule assembly so that themotion of the capsule can be transmitted to outsidethe housing. A sealing mechanism is used where the force bar penetrates thehousing and also acts as the pivot point for the force bar. Provision is made in thehousing for high- pressure fluid to be applied on one side of the capsule and low-

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    pressure fluid on the other. Any difference in pressure will cause the capsule todeflect and create motion in the force bar. The top end of the force bar is thenconnected to a position detector, which via an electronic system will produce a 4 -20 ma signal that is proportional to the force bar movement.

    DP Transmitter Application

    A DP transmitter is used to measure the gas pressure (in gauge scale) inside avessel. In this case, the low-pressure side of the transmitter is vented toatmosphere and the high-pressure side is connected to the vessel through anisolating valve. Theisolating valve facilitatesthe removal of thetransmitter. The output of the DP transmitter isproportional to the gaugepressure of the gas, i.e., 4mA when pressure is 20kPa and 20 mA whenpressure is 30 kPa.

    STRAIN GAUGES

    The strain gauge is a device that can be affixed to the surface of an object todetect the force applied to the object. One form of the strain gauge is a metalwire of very small diameter that is attached to the surface of a device beingmonitored.

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    For a metal, the electrical resistance will increase as the length of the metalincreases or as the cross sectional diameter decreases. When force is applied asindicated in Figure 8, the overall length of the wire tends to increase while thecross-sectional area decreases. The amount of increase in resistance isproportional to the force that produced the change in length and area. Theoutput of the strain gauge is a change in resistance that can be measured by theinput circuit of an amplifier. The change in the process pressure will cause aresistive change in the strain gauges, which is then used to produce a 4-20 mAsignal.

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    FLOW MEASUREMENT

    There are various methods used to measure the flow rate of steam, water,lubricants, air, etc., in a nuclear generating station. However, in this module will

    look at the most common, namely the DP cell type flow detector. Also in thissection we will discuss the application of a square root extractor and cut-off relayplus the possible sources of errors in flow measurements and different failuremodes that can occur.

    Flow Detectors

    Orifice Plate

    The orifice plate is the mostcommon form of restrictionthat