Application of Pinch Technology and Analysis

Application of Pinch Technology and Analysis INTRODUCTION: The term Pinch Technology was introduced by Linnhoff and Vredeveld to represent a new set of thermodynamically based methods that guarantee optimum energy requirements in design of heat exchanger networks. The application of Pinch technology to study industrial process is called Pinch Analysis. Applying first and second Laws of thermodynamics is essential in Pinch Analysis method. The first law of thermodynamics enables us to use the energy equations in order to calculate the enthalpy change in the streams passing through heat exchangers and the second law decides the direction of heat flow because according to second law heat may only flow in the direction from hot to cold regions but there conditions in heat transfer in heat exchanger like: 1) No temperature crossover should be done: since in a heat exchanger, a hot stream cant be cool down below the cold stream inlet temperature nor the cold stream can be heated up above the hot stream temperature. 2) In reality the hot stream can be cooled down to a temperature defined by the temperature approach of the heat exchanger. The temperature approach is the minimum allowable temperature difference (DTmin) in the stream temperature profiles. The temperature level at which DTmin is observed in the process is referred to as pinch point. Pinch Analysis There are 8 steps in pinch analysis which are: Steps of Pinch Analysis Identification of the Hot, Cold and Utility Streams in the Process Thermal Data Extraction for Process Utility Streams Selection of Initial DTmin value Construction of Composite Curves and Grand Composite Curve Estimation of Minimum Energy Cost Targets Estimation of Heat Exchanger Network ( HEN ) Capital Cost Targets Estimation of Optimum DTmin Value by Energy-Capital Trade Off Design of Heat Exchanger Network 1. Identification of the Hot, Cold and Utility Streams in the Process * Hot Streams: Hot streams that are required to be cooled down. * Cold Streams: Cold streams that are required to be heated up. * Utility Streams are used to heat or cool process streams, when heat exchange between process streams is not practical or economic. 2. Thermal Data Extraction for Process Utility Streams For each hot, cold and utility stream identified, the following thermal data is extracted: * Supply temperature (TS oC) : the temperature at which the stream is available. * Target temperature (TT oC) : the temperature the stream must be taken to. * Heat capacity flow rate (CP kW/ oC) : the product of flow rate (m) in kg/sec and specific heat (Cp kJ/kg 0C). CP = m x Cp * Enthalpy Change (dH) associated with a stream passing through the exchanger is given by the First Law of Thermodynamics: First Law energy equation: d H = Q  ± W In a heat exchanger, no mechanical work is being performed: W = 0 (zero) The above equation simplifies to: d H = Q, where Q represents the heat supply or demand associated with the stream. It is given by the relationship: Q= CP x (TS TT). Enthalpy Change, dH = CP x (TS TT) 3. Selection of Initial DTmin value As discussed before and according to second law of thermodynamics no temperature crossover can be done. Thus the temperature of the hot and cold streams at any point in the exchanger must always have a minimum temperature difference (DTmin). In mathematical terms, at any point in the exchanger Hot stream Temp. ( TH ) ( TC ) Cold stream Temp. >= DTmin For a given value of Q, if smaller values of DTmin are chosen, the area requirements rise. If a higher value of DTmin is selected the heat exchange between the exchangers will decrease and the use of utilities will increase. Thus, the selection of DTmin value has an imprtants and significant implications for both capital and energy costs. This table shows a typical DTmin of some industrial processes: No Industrial Sector Experience DTmin Values 1 Oil Refining 20-40 °C 2 Petrochemical 10-20 °C 3 Chemical 10-20 °C 4 Low Temperature Processes 3-5 °C 4. Construction of Composite Curves and Grand Composite Curve * COMPOSITE CURVES: Composite curves consist of temperature (T) enthalpy (H) profiles of heat availability in the process (the hot composite curve) and heat demands in the process (the cold composite curve) together in a graphical representation. To construct the composite curve, a stream with a constant heat capacity (CP) is represented on a T H diagram by a straight line running from stream supply temperature to stream target temperature. When there are a number of hot and cold streams, the construction of hot and cold composite curves simply involves the addition of the enthalpy changes of the streams in the respective temperature intervals. For heat exchange to occur, the hot stream cooling curve must lie above the cold stream-heating curve. This point of minimum temperature difference represents a bottleneck in heat recovery and is commonly referred to as the Pinch which is DTmin. Increasing the DTmin value results in shifting the curves horizontally apart resulting in lower process to process heat exchange and higher utility requirements. In summary, the composite curves provide overall energy targets but do not clearly indicate how much energy must be supplied by different utility levels. The utility mix is determined by the Grand Composite Curve. GRAND COMPOSITE CURVE (GCC): In selecting utilities to be used, determining utility temperatures, and deciding on utility requirements the Composite curve doesnt provide so much information, thats why Grand Composite Curve (GCC) is used. The GCC (Figure 3) shows the variation of heat supply and demand within the process.Using this diagramthe designer canfind which utilities are to be used. The aim is to maximize the use of the cheaper utility levels and minimize the use of the expensive utility levels. Low-pressure steam and cooling water are preferred instead of high-pressure steam and refrigeration, respectively. To construct GCC the information required comes directly from the Problem Table Algorithm. The method involves shifting (along the temperature [Y] axis) of the hot composite curve down by  ½ DTmin and that of cold composite curve up by  ½ DTmin. The vertical axis on the shifted composite curves shows processinterval temperature. In other words, the curves are shifted by subtracting part of the allowable temperature approach from the hot stream temperatures and adding the remaining part of the allowable temperature approach to the cold stream temperatures. The result is a scale based upon process temperature having an allowance for temperature approach (DTmin). The Grand Composite Curve is then constructed from the enthalpy (horizontal) differences between the shifted composite curves at different temperatures. On the GCC, the horizontal distance separating the curve from the vertical axis at the top of the temperature scale shows the overall hot utility consumption of t he process. The utility can be divided into many temperatures. The GCC indicates that we can supply the hot utility over two temperature levels TH1 (HP steam) and TH2 (LP steam). Recall that, when placing utilities in the GCC, intervals, and not actual utility temperatures, should be used. The total minimum hot utility requirement remains the same: QHmin = H1 (HP steam) + H2 (LP steam). Similarly, QCmin = C1 (Refrigerant) +C2 (CW). The points TH2 and TC2 where the H2 and C2 levels touch the grand composite curve are called the Utility Pinches. The shaded green pockets represent the process-to-process heat exchange. 5. Estimation of Minimum Energy Cost Targets Once the DTmin is chosen, minimum hot and cold utility requirements can be evaluated from the composite curves. If the unit cost of each utility is known, the total energy cost can be calculated using the energy equation given below. 6. Estimation of Heat Exchanger Network (HEN) Capital Cost Targets The capital cost of a heat exchanger network is dependent upon three factors: 1. The number of exchangers. 2. The overall network area. 3. The distribution of area between the exchangers. * AREA TARGETING: To calculate the HEN minimum total area Amin ,divide the composite curve into a set of adjoining enthalpy intervals such that within each interval, the hot and cold composite curves do not change slope. The total area of the HEN (Amin) is given by the formula below, where i denotes the ith enthalpy and interval j denotes the jth stream and dTLM denotes LMTD in the ith interval. NUMBER OF UNITS TARGETING: For the minimum number of heat exchanger units (Nmin) required for MER (minimum energy requirement or maximum energy recovery). The minimum number of units (NminMER) is the sum of the targets evaluated both above and below the pinch separately. NminMER=[Nh+Nc+Nu-1]AP +[Nh+Nc+Nu-1]BP Where : Nh = Number of hot streams Nc=Number of cold streams Nu = Number of utility streams AP / BP : Above / Below Pinch HEN TOTAL CAPITAL COST TARGETING: HEN capital cost (CHEN) is the capital cost is annualized using an annualization factor that takes into account interest payments on borrowed capital. The equation used for calculating the total capital cost and exchanger cost law is given below. C($) HEN=[Nmin{a+b(Amin/Nmin)c}]AP +[Nmin{a+b(Amin/Nmin)c}]BP Where a, b, and c are constants in exchanger cost law For the Exchanger Cost Equation shown above, typical values for a carbon steel shell and tube exchanger would be a = 16,000, b = 3,200, and c = 0.7. 7. Estimation of Optimum DTmin Value by Energy-Capital Trade Off To select an optimum DTmin value, plot the total annual cost which is the sum of total annual energy and capital cost versus values of DTmin. After plotting three important key features can be concluede: 1. If DTmin increases, the energy costs will increase but capital costs will decrease. 2. If DTmin decreases,t he energy costs will decrease but capital costs will increase. 3. Theoptimum DTmin is where the total annual cost of energy and capital costs is minimized. 8. Design of Heat Exchanger Network In designing the heat exchanger network it is essential to know which hot stream match which cold stream. Every match brings one stream to it target temperature. As mentioned before the pinch point divides the network into two separate regions, and each region is designed separeatley.When the heat recovery is maximized the remaining thermal needs must be supplied by the utilities. The graphical method of representing flow streams and heat recovery matches is called a grid diagram . All the cold (blue lines) and hot (red line) streams are represented by horizontal lines. The entrance and exit temperatures are shown at either end. The vertical line in the middle represents the pinch temperature. The circles represent heat exchangers. Unconnected circles represent exchangers using utility heating and cooling. To design the network and construct the grid diagram we use the CP Inequality Rule which states that the heat capacity flow-rate (CP) of the stream leaving the pinch needs to be greater than the CP of stream approaching the pinch, or CPout à ¢Ã¢â‚¬ °Ã‚ ¥ CPin So above the pinch: CPhot à ¢Ã¢â‚¬ °Ã‚ ¤ CPcold And Below the pinch: CPhot à ¢Ã¢â‚¬ °Ã‚ ¥ CPcold After making all the possible matches above and under the pinch separately, the two designs are then brought together and usually refined to further minimize the capital cost. After the network has been designed according to the pinch rules, it can be further subjected to energy optimization.

A Career in Electrical Engineering Essays -- Papers

A Career in Electrical Engineering Choosing the right career can mean the difference between being satisfied and being disappointed with my life. Many factors can influence the career that I may have for the rest of my life. A decision that I am going to make at the young age of nineteen will have a major impact on the next ten years if not the rest of my life. In order to make the best decision possible for my future I have decided, if not forced, to research a career of interest to me. The two major career choices I have been interested in for the past few years have been engineering and teaching. I have already done researched teaching so I decided to research engineering. There are many different types of engineering so I decided to pick the one most interesting to me. Electrical engineering is the career field I have selected to investigate. Engineering is something my parents have urged me to consider. Since a young kid I have been interested in building things. I use to tell my parents I wanted to be an inventor and build a time machine. Legos were my favorite toy growing up, and I have always been exceptionally good in math. Since my freshmen year in high school I have been interested in becoming a teacher, but during my freshmen year in college I was becoming more and more aware of the amount of money lower level teachers made. Many people were recommending engineering as a possible career option so I decided to look into it. Since I have always found electricity to be cool I decided to learn more about electrical engineering as a future career field. The Dictionary of Occupational Titles code for electrical engineering is 003.061-010, while the Guide for Occupational Exploration code is 05.01.01. There is anot... ... edge as an electrical engineer or whatever occupation I choose to enter. I feel very satisfied with the information I obtained. At times I was bored in this class being the only male, and having to listen to a bunch of females whine over stuff I didn’t care about. With regards to electrical engineering I leaned that electrical engineering is boring, and does not seem like an occupation I would enjoy. The people I talked to about engineering were happy with their jobs but were also nerds. I think I should really consider teaching as a possible career choice. Therefore, I am not certain about the career choices I have made. I think I will try to major in math and become a math teacher; I can always change my major if I am not happy with how things are going. I have learned that my happiness will be increased with better career satisfaction versus monetary gain.

Financial Analysis Project

Your task is to provide a written report discussing the financial position of the companies. Calculation of ratios should be included in an appendix to the report. In other words, in addition to the mechanical process of determining the ratios the report must include a written comparative analysis of the financial information: from year to year, between the companies and an overall comment on the financial session of the companies.The financial analysis project will be marked considering the following: Company selection [provide a brief description of each company] Liquidity analysis Solvency analysis Profitability analysis Activity analysis Overall comparative analysis Organization/flow/quality of writing Professionalism Please provide references to the corporate Web sites where copies of the financial statements may be found. Each analysis should have appropriate appendices showing your calculations and your work. Please ensure that your solution can be easily traced back to the Or lando financial statements.Thus, your entire analysis should be no more than 1000 words not Including any attached appendices and no more than 10 different ratios. Financial Analysis Project By strengthens are in the same industry [e. G. , Imperial Oil & Petrol-Canada, or Salesman & Big Rock]. Each other and between periods, indicating which company is in the best financial * Organization/flow/quality of writing easily traced back to the original financial statements. Thus, your entire analysis should be no more than 1000 words not including any attached appendices and no

Single Parenting - 2462 Words

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