Analysis Heat Exchanger Network Steam Power Plant in Using Pinch (Case Study in PT POMI Unit 3 Power Plant Paiton)

World energy usage is increasing rapidly, this increasing energy caused by many of the world community highly dependent on energy to support day-to-day life. Based on the Agency for the Assessment and Application of Technology (2018) Ministry of Energy and Mineral Resources in Indonesia Energy Outlook 2018 [1] the electricity demand continues to grow rapidly in all sectors, especially in the household and commercial sectors. It increased on average by 6.0% per year until 2050 to 7.4 times that of consumption in 2016.

Generator Steam Power (power plant) is a power generation system that uses the energy of hot steam is converted into mechanical energy and transmitted to a generator to produce electricity [2, 3]. One of electricity producers that use this type of power plant steam is PT. POMI Unit 3 Paiton Power Plant with installed capacity of 1 x 815 MW. The power generated by three turbines installed one axis, the turbine HP (High Pressure), IP (Intermediate Pressure) and LP (Low Pressure). This unit using two types of feed system water heater which consist of 12 closed feedwater heater and an open feedwater heater.

Feedwater heater is useful to raise the temperature of water in the boiler. Feedwater heater source comes from the extraction on steam turbine, but this process reduces power generation by turbine. However, it can be reducing the thermal load of the boiler [4]. Pinch analysis is used to calculate the design or in evaluating a system height exchanger Networks (HEN) such as reduced operating costs, simplify processes, improve efficiency, reduction and capital investment planning [4-9].

Steam cycle power plant in PT. POMI Unit 3 has 10 main components as in Figure 1. The study was conducted on Heat Exchangers in Feed Water Heater with heat flow in the form of Extraction Steam or residual steam turbine propulsion seen on the red color line. Table 1 is preliminary data obtained from log sheet operations and production data. The data taken is as follows:

3.1 Problem analysis table

Analysis of the Problem Table aims to determine the value of the pinch and describes the maximum amount of heat energy exchange at each interval to determine the temperature and also the lack of energy in the process of heat exchange in each of the streams of hot and cold flow.

Table 1 is the data needed for the analysis process pinch. The value of the specific heat capacity (CP) resulting from the calculation by using Eq. (2). This preliminary data is the result of the extraction of data that has not changed ΔTmin.

ΔTmin obtained from the analysis in Table 2 is by way of determining the smallest of temperature differences in the flow of hot or cold flow contained in the data used.

Table 2 shows the smallest value of ΔT is ΔTmin allowable value that is equal to 19,755℃. After determining the value of ΔTmin, will dilakuakan analysis on the problem of table.

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Figure 1. Schematic of steam power cycle power plant PT POMI Unit 3

Table 1. Initial data analysis pinch

Table 4 shows the population of the relationship between the flow or cold flow and heat flow. Results from Table Problem analysis algorithms were used to describe the cascade diagram as shown in Figure 3 is used to analyze the utility of hot and cold utility also has a function as determining the value of a pinch. Pinch value is determined by addressing energy shortage, minus the value of the Cascade diagram showing a lack of energy that is used to achieve the desired temperature

Based on Figure 2 it can be seen that the pinch is 51,0875℃. Pinch Point value lies in the utility value of 0 (zero) then pulled straight to determine the temperature that corresponds to the Problem Pinch table algorithms.

3.2 Composite curve analysis, shifted composite and grand composite

Composite curve analysis, composites and Grand Composite shifted using the data from the analysis of the problem of table.

3.2.1 Composite curves

Analysis of the composite curve in Figure 3. The curves obtained from the relationship between the temperature in the hot stream and the cold stream of the Heat Flow. Heat flow curve depicted on the red line and the cold flow curve drawn from the blue line, Value pinch it can be seen from a position adjacent stream.

3.2.2 The curve shifted composites

Analysis shifted composite curves have the same process with a composite curve, the difference lies in the shift of the curve caused by a shift in the temperature of the treatment ΔTmin so that it can be seen that the curve of the yield curve ΔTmin treatment of cold flow and heat flow into contact as shown in Figure 4.

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Figure 2. Cascade

3.2.3 Grand composite curve

Grand composite curve in Figure 6 derived from net heat flow graph with temperatures already in the pan or the temperature shifted. Grand composite curves are used to establish the utility of multiple targets. Grand composite curve also illustrates the difference between the possible heating of the heat flow to the heating required by cold flow.

Based on Figure 4 and Figure 5 knowable differences before and after analyses flow pinch. Figure 4 shows the distance between the hot and cold flow far enough when compared with Figure 5. The effect of distance between the cold flow and heat flow caused by the temperature difference is greater the distance between the flow, the greater the energy needs, loss of energy, and more little effectiveness. Heat Value Recovery when two streams of hot and cold streams are combined in Figure 4 is 380555,9744kW and in Figure 5. amounting 346,243.4772 kW. Heat Recovery value obtained from slices of the curve, while the remainder of the slices on each of the heat flow curve or cold flow is minimum energy demand.

Based on Figure 6, known that touches the curve shifted diagram Pinch Temperature is a value that is 51.0875℃, the diagram on the highest position that is equal to 34321.49717 Duty Heating kW, and the diagram on the bottom shows the Cooling Duty is equal to 34383.97676 kW.

3.3 Efficiency analysis

Analysis of the efficiency of using Eq. (5) with WNET is the turbine output value and Qin is the value of the input energy. The efficiency obtained is the efficiency of the entire power plant.

Based on Table 5 it can be seen that pinch analysis is able to reduce energy consumption in the process of electricity production in power plants PT POMI Unit 3 is equal to 34383.98 kW. Later in Table 6 and Figure 6 note that the analysis pinch able to increase the efficiency of 0.506%, and in Table 7 and Figure 7 known that pinch analysis is also able to reduce fuel consumption that is equal to 1.714 kg / s.

3.4 Grid diagram

Heat Exchanger Design Network is a procedure combining the two streams of hot and cold with mutual objectives and optimize energy transfer requiring less additional energy (either heating or cooling [12]. Diagram grid work according to the rules of analysis Pinch i.e. (Figure 8), no additional heat below Pinch utilities, no additional utility over Pinch cold, and there is no heat transfer across the pinch. If there is displacement across Pinch, then it must be set back Pinch to add some heat on the top of the Pinch and a cold load at the bottom of the Pinch.

Diagram design grid on the final results use a split or separation of flow, flow separation occurs because of lack of appropriate flow if integrated so that the necessary separation with no violation of the rules on the CP using design data from Table 3.

Based on the results of the design grid diagrams have been obtained, derived design modifications to the flow diagram of Feed Water Heater and a new Steam Extraction. Here is a flow diagram after Pinch analysis (Figure 9).

Table 3. ΔTmin problem 19,755℃

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Figure 4. The curve shifted composites

Table 4. Problem table algorithm

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Figure 5. Grand composite curve

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Figure 6. Efficiency

Table 5. Data calculation of efficiency

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Figure 8. Diagram design grid

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Figure 9. Flow diagram after pinch analysis