simulated in the SuperPro Designer 5.5 software which is commonly used in

Transcription

1 7.1 Software simulation Ethanol production processes using the methods of the present study were simulated in the SuperPro Designer 5.5 software which is commonly used in pharmaceutical and biotechnology industries. Process simulation software was used to estimate data for the large scale economic analysis Simulation data input Operation modes The software offers two operation modes for production simulations: batch mode and continuous mode. The characteristics describing these two modes are identified in the corresponding dialog box shown in Figure 7.1. The operations for enzyme production using SmF method was set as batch modes instead of continuous within the software simulation. Meanwhile, as shown in the Figure 7.1, the annual operating time is set as 7,920 hours by default, which corresponds to 330 working days per year. However, the operating mode and the annual operating time can be changed at any time by using the Task: Set Mode of Operation option from the main menu. 166

2 Figure 7.1 Dialog box for selecting operation mode Material registration Materials are divided into two groups--components and mixtures--in the software. Mixtures are the mixed materials consisting of a list of ingredients (components). In contrast, components are pure raw elements, for simulation purposes. All materials used was specified within the software. In this thesis, the mixtures used to efficiently utilize the sugarcane bagasse for enzyme, ethanol and ruminant feed production include air (component ingredients: nitrogen and oxygen) and cellulase (CMCase, Cellobiase and FPase). Other components beyond the ones specified as ingredients of mixtures are as below: Acetic Acid Biomass Calcium Chloride 167

3 Calcium Oxide Carbon (Charcoal) Ethyl Alcohol Potassium Chloride Potassium Di-hydrogen Phosphate Magnesium Sulfate Sodium Hydroxide Trichoderma longibrachiatum Urea Yeast Yeast Extract Some of the mixtures and components are provided by the databank within the SuperPro Designer 5.5 software but for some components the user must create the relevant components at the beginning of the computer simulation process. Figure 7.2 gives an example dialog box for registering a new component (cellulose). Figure 7.2. Example dialog box for registering new components 168

4 7.1.2 Building simulation flowsheets Based on the experiments performed in this thesis, the first step in building a simulation flowsheet is to add equipment (procedures). For the current study, the required equipment includes: three blending tank, one belt filter, two mixer, two stirred reactor, two air filter, one microfilter, one centrifuge, one freeze dryer, one heat exchanger, one distillation coloumn and one receiver tank. The second step in building a simulation flowsheet is to add material streams, which represent inputs, intermediate products and outputs throughout the production process. Three kinds of steams--feed streams (inputs), intermediate streams and product streams (outputs), are used in this computer simulation. Connecting an unoccupied area with an inlet port of destination equipment creates feed streams. Connecting an outlet port of source equipment with an inlet port of destination equipment creates intermediate streams. Connecting an outlet port of source equipment with an unoccupied area creates product streams. The information on the streams contained in the Table 7.1 corresponds directly to the flowsheets in Figures

5 Table 7.1 Stream specifications in the processes Stream Name Source Destination S 101 INPUT* P1/V-101 S 102 INPUT P1/V-101 S 142 INPUT P1/V-101 S 103 OUTPUT** OUTPUT S 105 P1/V-101 P3/BF-101 S 104 INPUT P3/BF-101 S 143 OUTPUT OUTPUT S 106 P3/BF-101 P4/MX-101 S 107 INPUT P4/MX-101 S 108 P4/MX-101 P2/V-102 S 109 INPUT P2/V-102 S 110 INPUT P2/V-102 S 111 P2/V-102 P10/AF-101 S 112 P10/AF-101 OUTPUT S 113 P2/V-102 P5/V-103 S 117 P5/V-103 P20/V-108 S 118 P5/V-103 P6/MF-101 S 119 P6/MF-101 OUTPUT S 127 P6/MF-101 P7/DS-101 S 121 P7/DS-101 OUTPUT S 120 P7/DS-101 P9/V-104 S 123 P9/V-104 P8/FDR-101 S 124 P8/FDR-101 OUTPUT S 125 P8/FDR-101 OUTPUT S 114 P2/V-102 P11/MX-102 S 115 INPUT P11/MX

6 S 116 P11/MX-102 P20/V-108 S 126 INPUT P20/V-108 S 128 INPUT P20/V-108 S 129 P20/V-108 P17/V-107 S 130 P20/V-108 P13/HX-101 S 131 P14/C-101 P13/HX-101 S 132 P13/HX-101 P14/C-101 S 133 P13/HX-101 OUTPUT S 134 P14/C-101 OUTPUT S 135 P17/V-107 OUTPUT S 139 P17/V-107 P18/AF-102 S 147 P18/AF-102 OUTPUT *INPUT in the source column implies this stream is a feed stream; **OUTPUT in the destination column implies the stream is a product stream; Otherwise, the remaining streams are intermediate stream 171

7 7.1.3 Procedural operations Within the SuperPro Designer 5.5 software, the first step toward initialization of the equipment blending tank is to add corresponding operations (Figure 7.3). Figure 7.3 Dialog box of adding operations to equipment (Blending Tank) According to the present study, relevant procedural operations were selected from the left Available Operations column and specified in the right column. The next step was to initialize all the selected operations that have been added to the equipment. Two operations out of the six-- CHARGE - SCB and AGITATE are given as examples to illustrate the process to initialize operations. These two 172

8 examples are chosen because the first one is the typical operation dealing with a feed stream (inputs) and the second one is one of the key operations for initialization of the simulation. Figure 7.4 Menu of initializing operations for equipment Figure 7.5 Dialog box for charging of medium into equipment 173

9 After selecting Operation Data: CHARGE-SCB from the menu as shown in the Figure 7.4, the dialog box will come up and is shown in Figure 7.5. The dialog box shown in Figure 7.5 allows the user to specify the operating conditions, emission data, labour, description and scheduling, etc. for the operation. To initialize the Operating Conditions tab for the first charge operation in this example, the source of the material must be specified in the software. Click on the Composition button to access the stream data information for this feed stream (see Figure 7.6). Figure 7.6 Dialog box for the stream Charge SCB To add medium to the stream, double-click its name in the Registered Ingredients list on the left side of the above figure. For example, the amount

10 kilograms (kg) per batch in the Total Flowrates category can be specified as a starting point for SCB. After specifying the charge amount of mixture medium, click OK to return to the dialog box for the Charge-water (see Figure 7.7). Equipment setup time is set as 12 h by default. Equipment processing time is automatically calculated and equals 0.17 hrs based on a flowrate 100 kilograms per hour (kg/h) by default. There are several other tabs for the dialog box, including Volumes, Emissions, Labour, etc, Description and Scheduling. These tabs are all self-explanatory and worth visiting to adjust default parameters if necessary, before software simulations begin. Figure 7.7 Dialog box for the stream Charge SCB 175

11 7.1.4 Simulation process All the data specified as per the procedure mentioned above provide a starting point for software simulation. Given simulation inputs specified as above, the SuperPro Designer 5.5 software is capable of conducting this simulation by using the Tasks: Solve M&E Balance option from the main menu. This will cause the program to calculate the mass and energy balances for the entire flowsheet, estimate the equipment sizes, and model the equipment scheduling. However, for economic analysis purposes, it is of interest to increase or decrease the annual outputs to determine the influence of the production scale on the product unit costs, for example. In order to do that, the SuperPro Designer 5.5 software offers the option to change all the stream flowrates and equipment sizes in one step by selecting the Tasks: Adjust Throughput option from the main menu (Figure 7.8). In the dialog box shown in Figure 7.8, scale up (or down) could be realized based on either a factor or target output (per batch or per year). By choosing the scale up (or down) criteria and clicking OK in the dialog box in Figure 7.8, the software will simulate the new production process by solving new mass and energy balances for the entire flowsheet, estimating the new equipment sizes and remodel the equipment scheduling. 176

12 Figure 7.8 Dialog box for Process Throughput Adjustment All the data specified above provide a starting point for simulation of proposed study. Given simulation inputs specified above, the SuperPro Designer 5.5 software is capable of conducting this simulation by using the Tasks: Solve M&E Balance option from the main menu. This will cause the program to calculate the mass and energy balances for the entire flowsheet, estimate the equipment sizes, and model the equipment scheduling. In the dialog box shown in Figure 7.9, scale up (or down) could be realized based on either a factor or target output (per batch or per year). By choosing the scale up (or down) criteria and clicking OK in the dialog box in Figure 7.9, the software will simulate the new production process by solving new mass and energy balances for the entire flowsheet, estimating the new equipment sizes and remodel the equipment scheduling. 177

13 Figure 7.9 Dialog box for Process Throughput Adjustment The present study could be divided into two major parts (i) enzyme production and (ii) ethanol production. As a starting point, the cellulase enzyme production scale from the main fermentor is assumed to be 1 kilograms (kg) per batch. Zhang and Lynd (2003) reported that the cellulase enzyme represented 20% of the mass of cellulolytic microorganism, which implies 5 kg of T. longibrachiatum (5 =1 20%) will be produced. Based on information obtained from Strobel et al., (2004), the cellulose-microbe mass transfer coefficient is assumed to be 10:1, which implies in order to produce 1 kg of cellulase, 5 kg of microbe, 50 kg of cellulose must be consumed. Every 50 kg of cellulose corresponds to 125 kg of SCB (40% cellulose). Thus, for every 125 kg of SCB consumed, the final product will be 5 kg 178

14 of new T. longibrachiatum. Following equation represents this simplified fermentation process and provides a basis for economic analysis in this thesis. SCB (125 kg) T. longibrachiatum (5 kg) + Cellulase Enzyme (1 kg) + FEP (119 kg) The FEP was further used for the ethanol production. Thus, for production of ethanol, the feedstock available, after enzyme production and detoxification of FEP, is 119 kg. As per our study, 6.14% ethanol production could be achieved at optimized conditions: ph 5.0, incubation period 72 h, inoculums size 10 ml/l, and substrate concentration 40 g/100 ml. The size of inoculum in ethanol fermentation is of great importance in completing the fermentation process. Further increase in inoculums size did not result in the considerable enhancement of ethanol production. In order to achieve maximum ethanol production, kg of yeast would be required. Following equation is simplified representation of the ethanol fermentation process SCB (119 kg) Saccharomyces cerevisiae (2.975 kg) + Ethanol (18.30 L) + FEP (97.73 kg) The whole fermentation end product of the equation is considered as animal feed. Thus, at final stage kg of ruminant protein could be produced. The equipment occupancy chart also exhibits that the process is completed in two different stages (Figure 7.10) 179

15 V-101 BF-101 MX-101 V-102 V-103 Equipment MF-101 MX-102 V-108 HX-101 DS-101 V-104 FDR-101 Figure 7.10 Equipment occupancy chart 180

16 Figure 7.11 Flowsheet of the proposed study 181

17 7.2 Economic evaluation Economic analyses are conducted to examine the unit costs of the present experimental plant, as measured by dollars per kilogram ($/kg) and the profitability, as measured by two profitability indicators: payback period and net present value (NPV) at 7%. These two objectives are realized by identifying equipment costs and economic parameters used as input into the simulation software. Economic items (such as direct fixed capital costs, operating costs and annual net cash flows) are calculated based on these inputs. For objective one, unit costs are specified by the software simulation output. For objective two, two profitability indicators--payback period and net present value are calculated, using the data for both production costs and sale revenues Data sources In order to conduct economic analysis, input data must be specified. As discussed, five groups of input data are of interest in this thesis: (1) properties of components and mixtures and their corresponding economic data; (2) feed stream data; (3) equipment cost data; (4) data for economic parameters such as project life and discount rates; and (5) data for other technical parameters, including setup time, processing time, temperatures, flowrates, among others. The data is either obtained from the procedural operation descriptions or obtained directly from the default values in the simulation software. 182

18 Estimation of Equipment Costs Assuming new equipment is similar to a base item where cost data (C 0 ) is available, SuperPro Designer 5.5 software predicts equipment purchase costs (EPC) by using a power relationship for equipment capacities. Equation 5.1 explains the equipment cost estimation process, where Q and Q o are the new and base equipment capacities, respectively, and a is the exponent of the power law function given by the software or specified by the user. By default, this exponent is set as 0.6 for estimating new equipment cost (Peters et al., 2003). (Q) a EPC = C Q 0 Within the SuperPro Designer 5.5 software, in order to estimate equipment costs based on its capacity ( Q ), the user can either choose a built-in model, where data are provided by the software, or choose a User defined-model, where base equipment data ( C 0, Q o and a) must be entered into the software by the user. 183

19 Table 7.2 : Major equipment specification and FOB cost (2015 prices) Quantity/ Stand-by Description Unit Cost ( $ ) Cost ( $ ) V-101 Blending Tank Volume = L Diameter = 0.36 m BF-101 Belt Filter Belt Width = 0.06 m MX-101 Mixer Rated Throughput = kg/h V-103 Blending Tank Volume = L Diameter = 0.85 m MF-101 Microfilter Membrane Area = m^2 DS-101 Disk-Stack Centrifuge Sigma Factor = m^2 FDR-101 Freeze Dryer Tray Area = 0.12 m2 Capacity = 4.59 kg H2O/cycle V-104 Blending Tank Volume = 7.24 L Diameter = 0.15 m AF-101 Air Filter Rated Throughput = 0.00 m^3/s MX-101 Mixer Rated Throughput = kg/h HX-101 Heat Exchanger Area = 0.00 m^

20 C-101 Distillation Column Number of Stages = 14 V-107 Stirred Reactor Volume = L Diameter = 0.62 m V-102 Stirred Reactor Volume = L Diameter = 1.19 m AF-102 Air Filter Rated Throughput = 0.00 m^3/s V-108 Fermentor Volume = L Diameter = 0.32 m All Listed Equipment Unlisted Equipment (0.25 All Listed Equipment) Total equipment purchase cost Economic parameters Three groups of economic parameters was specified: (1) economic parameters for the entire project (Figure 7.12); (2) capital cost parameters and (3) operating cost parameters. All economic parameters are chosen by the default data within the software. The specification process is realized by choosing the Economic Evaluation Parameters from edit button of the main menu in the simulation software. The dialog box for the Time Valuation tab is shown in Figure In this thesis, all parameter values are specified by their default values within the simulation software. 185

21 Figure 7.12 Dialog box: economic parameters for entire project Unit cost analysis In order to calculate unit costs, direct fixed capital (DFC) and operating costs was calculated Direct fixed capital cost calculation The direct fixed capital costs calculation is the basis for further economic analyses such as the operating cost analysis (used to determine the unit costs) and cash flow analysis (used to determine the profitability). Based on the specification of major equipment costs, direct fixed capital (DFC) costs are estimated in Table 7.3. Following equation was used to calculate the DFC costs, which consist of Total plant direct costs (TPDC), Total plant indirect costs (TPIC) and other costs (OC): DFC =TPDC +TPIC +OC 186

22 Table 7.3. Direct fixed capital costs estimates (2015 price in $) Sl. No. Item Cost ($) A. Total plant direct cost (TPDC) Equipment Purchase Cost Installation Process Piping Instrumentation Insulation Electricals Buildings Yard Improvement Auxiliary Facilities B Total plant indirect cost (TPIC) Engineering Construction C. Other costs (OC) Contractor's fee Contingency DIRECT FIXED CAPITAL (DFC)

23 Annual operating cost calculation Annual operating costs were calculated and equal the sum of the following items as specified within the software: (1) Raw materials; (2) Labour-Dependent; (3) Facility- Dependent; (4) Laboratory/QC/QA (QC=Quality Control; QA=Quality Analysis); (5) Waste treatment disposal; and (6) Utilities. The cost of consumables was negligible hence it was not considered during the calculations. Eight different raw materials are examined in the process for this thesis and economic evaluation purposes. Two different utilities were examined in the production process viz., electricity and heat transfer agents such as steam, cooling water, and chilled water. The electricity costs were calculated as $7780 per year. The cost of heat transfer agents viz., steam ($4.2 / 1000kg), cooling water ($0.1/1000kg) and chilled water ($0.4/1000kg) was calculated to be $69, $173 and $15173, respectively. The total labour cost (TLC) is calculated as the sum of the labour demand per type (LDT) multiplied by the labour rate per type (LRT). That is: TLC = LDT LRT In this software, the default single labour rate is set as $69.00 per hour. The total labour hours required is calculated and equals hours annually. So, the total annual labour cost is $

24 The facility-dependent costs (FDC) accounts for depreciation (DEP) of direct fixed capital (DFC) costs, equipment maintenance (MAI), insurance (INS), local taxes (LT), and the possibly other overhead-type of factory expenses (FE). Equation 5.4 is used to calculate the FDC. FDC =DEP +MAI +INS + LT + FE The depreciation (DEP) item is calculated using a straight-line depreciation method, considering a salvage value fraction (f) of the direct fixed capital (DFC), which is assumed 5% in this analysis by default. The depreciation period (n) is set to ten years by default. Equation 5.5 is used to calculate depreciation: DFC (1-f) DEC = n The factor method is used in the estimation of the equipment maintenance (MAI), insurance (INS), local taxes (LT), and other overhead-type of factory expenses (FE) respectively, based on the direct fixed capital (DFC). Laboratory/QC/QA accounts for the costs of off-line analysis and quality control costs. In this thesis, it is estimated by default as 15% of total labour costs. The waste generated during the process is divided in solid and liquid waste materials. The default calculation of the waste material resulted as $19000 for solid waste treatment and $2000 for liquid waste treatment. 189

25 Once the above cost components were calculated, then total operating costs were derived as listed in Table 7.4. The annual operating cost was found to be $ Table 7.4 Total operating cost Cost item Cost ($) Raw Materials 2000 Labour-Dependent Facility-Dependent Laboratory/QC/QA Waste Treatment/Disposal Utilities Total Profitability analysis Reduced unit costs information is valuable for economists, engineers and researchers because they are concerned with the long-run industry sustainability. However, potential may be more concerned with the profitability of their investment. Profitability is typically measured by such indicators as payback period, net present value (NPV) and internal rate of return (IRR). The payback period is a simple indicator measuring how long it takes to 190

26 recover the initial investment in the simulated production plants. The projects with the quickest payback are considered as potential investment opportunities. The payback period is calculated as the quotient of the total capital investment divided by the net profit as shown in following equation: Total capital investment Payback period = Net profit Shown in the Table 7.5, the payback period is calculated and equals 8.13 years, which implies that it takes more than eight years to recover the initial investment for the enzyme, ethanol and animal feed production plant using the current study. This number can be compared with corresponding payback period values of alternative projects facing potential investors. The gross margin of the project was 15.61% at 1231% return on investment. 191

27 Table 7.5 Cash flow and profitability indicators ($1000) Year Capital Investment Sales Revenues Operating Cost Gross Profit Depreciation Taxable Income Taxes Pay Back Period 8.13 years Gross Margin 15.61% Return on investment 12.31% Depreciation Method Straight-Line DFC Salvage Fraction