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1 MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF MINING AND GEOLOGY PHAM DINH THANH GRADUATION THESIS INTRODUCTION OF THE NITROGEN PRODUCTION TECHNOLOGY IN CA MAU FERTILIZER PLANT AND CALCULATION OF THE HEAT TRANSFER AREA OF THE CONDENSER HANOI – 06/2019 ACKNOWLEDGEMENT First of all, I would like to deeply express my sincere gratitude to my supervisor, Dr Vu Van Toan for his invaluable guidances, suggestions, and assistances throughout this thesis Without his guidance, supports, especially his meaningful feedback, this thesis cannot complete on time Secondly, I also thank the Oil Refining and Petrochemical Department, Oil and gas Faculty, Hanoi University of Mining and Geology for not only the tremendous academic support, but also giving me a lot of career opportunities, scholarships for exchanging with the universities in the world And thank you to all lecturers who had assisted me during my studying time in Advanced Program Last of all, I wish to express my sincere gratitude to my family, friends for their encouragement and moral support They are the most important people in my life and I dedicate this thesis for them Sincerely Pham Dinh Thanh TABLE OF CONTENTS LIST OF THE TABLES Table 2.1 The market share of PVCFC Table 2.2 The miles stones of PVCFC Table 2.3 The main products in PVCFC Table 2.4 The target of the demineralized water Table 2.5 The targets of compressed air Table 2.6 The properties of nitrogen and oxygen Table 2.7 The standard output air BFW: LIST OF ABBREVIATIONS Boiling Feed Water CCR: Central Control Room LMTD: Log Mean Temperature Difference PVCFC: Petro Vietnam Ca Mau Fertilizer joint stock Company PFHE: Plate-Fin Heat Exchanger PIC: Pressure Indicator Control INTRODUCTION Motivation of the thesis During the past decades, Vietnam has transformed to low middle income country from one of the poorest countries Vietnam now is one of the most dynamic country in ASEAN Vietnam is also an agricultural power in the world with a total volume of agricultural exports of more than 40 billion dollars and 15 th in the world Vietnamese agricultural products are exported to 180 countries and territories [1] Therefore, the demand of the fertilizer is very big in agriculture Fertilizer is an important factor contributing to increased productivity and quality of agricultural products It helps the agricultural products to get international standards In the production of fertilizers, nitrogen (N 2) is an important component in the ammonia synthesis segment High purity N production is an essential requirement not only to provide purity N2 for the fertilizer industry but also to other industries such as stainless steels production and semiconductor manufacturing Liquid nitrogen storage is very important in the fertilizer production plant, which contributes to ensuring the supply of vapor nitrogen helps the plant operate stably Nitrogen is stored in liquid form, so calculating and designing the condenser is a very necessary problem to liquify the vapor nitrogen For the practical problems, it was decided to choose the thesis “Introduction of the nitrogen production technology in Ca Mau fertilizer plant and calculation of the heat transfer area of the condenser” The objective of the thesis In this thesis, it was focused on to make the readers realize more detail about N production technology, how its effects to overall economy and especially in the fertilizer industry Besides, this study provides a clear understanding of the factors make the change of purity N2 in distillation tower The structure of the thesis As the motivation of the thesis, it was divided into parts as below Chapter 1: Overview of nitrogen Chapter 2: The technology to produce nitrogen gas in Petro Vietnam Ca Mau fertilizer joint stock company (PVCFC) Chapter 3: Calculation of the heat transfer area of the condenser to get 32 l/h liquid nitrogen in PVCFC CHAPTER 1: OVERVIEW OF NITROGEN 1.1 Introduction of nitrogen Nitrogen is a chemical element with symbol N and atomic number is At room temperature, it is a colorless, odorless, tasteless, inert gas and exists in the form of N2 molecule Nitrogen accounts for about 78% of the Earth's atmosphere and is part of every living organism Nitrogen can create many important compounds such as amino acids, ammonia, nitric acid and cyanide The stable chemical bonds between nitrogen atoms make it difficult for both organism and industry to convert N to useful chemical compounds, but also release a large amount of useful energy when burning, blasting or decomposing back into nitrogen gas Nitrogen is present in all living organisms, in the form of amino-acids (DNA and RNA) The human body contains about 3% nitrogen by weight, which is the fourth most common element in the body after oxygen, carbon and hydrogen The nitrogen cycle describes the movement of this element from the air into the biosphere and organic compounds, then returns to the air The physical property of nitrogen at atm, o C (Table 1.1) Table 1.1 The property of nitrogen [2] Molecular formula Molecular weight Melting point Boiling point Density N2 28 g/mol 63.15 K 77.36 K 1.25 g/L 1.2 The production and application of nitrogen in the industry 1.2.1 The production of nitrogen Nitrogen is an industrial gas produced by fractional distillation of liquid air After removing CO2 and steam The air was liquefied under the high pressure and low temperature The temperature was then gradually decreased to -196 o C, the nitrogen boils and separates from oxygen because oxygen has a higher boiling temperature (183 o C) Nitrogen gas is circulated in steel cylinders, compressed under 150 atm In the laboratory, we create the small amount of pure liquid nitrogen by heating slightly the saturated ammonium nitrite solution: NH4NO2 → N2 + 2H2O We can replace ammonium nitrite by saturated solution of sodium nitrite salt and ammonium chloride: NH4Cl + NaNO2 → N2 + NaCl + 2H2O 10 1.2.2 The application of nitrogen Nitrogen gas is produced by evaporating nitrogen liquid It widely has the application in the life and especially replace the air in some cases to avoid the oxidation - Preserve the fresh food by adding pure nitrogen inside to avoid the activity of bacteria - Put it on the top of the liquid explosive for safety - Manufacture the electronic components - In manufacture of stainless steel - Inflate the car tires, aircraft tires, reducing the problem caused by moisture and oxygen in the air Nitrogen liquid has low temperature so it is very useful in maintaining the temperature - Keep the low temperature for transporting the food - Preserving body parts as well as sperm and egg cells, samples and probiotics - Study about the cooling agents - In dermatology to remove ugly malignant skin lesions or carcinogenic potential - Liquid nitrogen can be used as a cooling source to speed CPU, GPU, or other types of hardware 1.3 The production technology of nitrogen in the industry 1.3.1 Deep cooling method for producing nitrogen In the industry, some processes need a large amount of pure oxygen and nitrogen It is collected after liquefying air and then distillate it to have nitrogen and oxygen, separately [1] Besides, we will obtain Kr, Ne, etc - Pure oxygen with 95-97% oxygen is used in the chemical industry and metallurgy - Pure oxygen with 99.5% oxygen is used in the welding and medical - Liquid oxygen is used in the missile rocket engineering - Pure nitrogen with 99.998% N2 used in synthesizing ammonia The cooling process have three types Normal cooling that use water or air to cool a system from high temperature to normal temperature This is a self-destructive process that does not consume effort 33 Figure 2.11 The technology diagram of nitrogen production unit [10] Properties of nitrogen and oxygen (Table 2.6) Table 2.6 The properties of nitrogen and oxygen Nitrogen Oxygen - Nitrogen is a colorless, odorless, - A colorless, odorless gas non-toxic gas - Molecular weight: 16 - Molecular weight: 14 - Boiling temperature: -182.96 o C o - Boiling temperature: -195.79 C - Density: 1,429 g / liter (at o C) - Density: 1,251 g/l (at o C) - Occupy 21% of air volume Based on the different properties of oxygen and nitrogen, we can use them to separate them at different boiling temperatures Standard output of nitrogen is shown in table 2.7 Table 2.7 The standard output air Temperature Pressure Purity Pressure design Temperature design Maximum nitrogen gas flow Normal flow of nitrogen gas Maximum liquid product 25 o C 0.7 MPa (min) 99.99% volume 1.1 MPa 75 o C 520 m3/h 420 m3/h 32 l/h 34 The main equipment of the nitrogen production unit Adsorption equipment TEPSA E31101 A/B: Figure 2.12 The adsorption equipment Adsorption process consists of adsorption device and regeneration device is attached with continuous heating equipment The adsorbent is loaded into the tower mainly of active aluminum volume 186 kg, molecular sieve 611 kg volume to absorb water, CO2, hydrocarbons, C2H2 (is shown in the figure 2.12) The concentration of CO2 in the product gas must not exceed 1ppm, high concentration steam of CO2 will cause the solid in the pipe difficult to treat Adsorption process: Open air valve KV0157A to allow gas to enter adsorption device T31101A with flow 1106.22 Nm3/h, pressure 8.27 bar, temperature 38.5 o C Heating equipment E31101A and vent valves are closed Air flow into the adsorbed tower of water, CO2, acetylene the lower temperature of the adsorption tower at this time is 58.83 35 o C After 43 minutes, the gas is adsorbed out at a temperature of 51.2 o C, pressure 8.24 bar and CO2 concentration does not exceed ppm Then the gas is transferred to the heat exchanger E31102 with a temperature of 44.42 o C and flow of 1106.22 Nm3/h Regeneration process includes regeneration steps: - Reducing pressure: Open vent valve KV159B of regeneration device T31101B about 1.5 minutes for the pressure of T31101B to reduce and reduce the temperature - Heating: Start the heating system for about 13 minutes for the device to increase the temperature for T31101B - Cooling: The flow of regenerated gas from E31102, with medium pressure and low temperature will enter to cool T31101B in about 23.4 minutes At this time the temperature of T31101B is 64.6 o C - Pressure: The pressure in the regenerative tank is low, it needs to be pressurized to achieve the necessary pressure for adsorption Valve HV 0108 is opened, the air flow in the adsorption tower will pressure the gas flow in the regeneration tower for devices to achieve the required pressure in about minutes - Parallel running: After the regeneration process of two towers, it is necessary to run parallel 0.1 minutes before opening the air inlet valve to the heat exchanger The adsorption-release cycle is continued Heat exchanger E31102 and turbine expander Turbine expander The technological diagram for turbine expander is shown in figure 2.13 It includes oil pumps (1 work, break) and oil tank, turbine including gears between the shaft and gear is 0.1-0.4 mm, filter equipment, device for exchange the temperature of oil and freshwater Oil pump have a role of reducing the speed of expander when the expander overspeed and seal gas (instrument air) is to insulate gas inside and outside oil Desired expander is designed with speed expander > 54000 rpm, To input (TI 0127) is -162 o C, To output (TI 0129) is -187.05 o C, Pin (PI 0130) is -3.96 bar, Pout (PI 0191) is -0.29 bar, opening valve HS 0173 100%, T o oil in the tank is 46.2 o C, temperature of oil after exchanging heat with freshwater is 40 o C, seal gas is instrument air Operating process: 36 Open seal gas for the turbine system, start oil pump for 30 minutes, when the air system is full, increase to 20% capacity expander, gradually speed up expander with pressure instrument control (PIC0136) When the expanding device cool down, expander is decreased the speed with oil pump system (including pumps with work, break based on the program) The oil after decreasing the speed will be passed through the main heat exchanger between the oil and freshwater to reduce To, To the output after cooling is 40 o C And then, it will be transferred to the filter device to filter the dirt and be transferred to the turbine system to reduce the temperature of gas input Oil emitted from the turbine with a maximum of 46.2 o C will return to the oil tank system and be pumped back in cycles The output gas will be defrosted before being transferred to the heat exchanger E31102 During the cooling air process, close the valves of the defrost process (or they will be closed by themselves) After the cooling air in the heat exchanger, it will be returned to TEPSA for adsorption (note: the cooling speed of turbine does not exceed 28 o C/h) Figure 2.13 The structure of turbine expander Heat exchanger E31102 is a cooling device that cool the compressed air from TEPSA by two streams of emission gas from turbine expander and a flow of gas from the distillation tower E31103 After the gas is cooled by E31102, the outflow 37 gas will be sent to the distillation tower to separate nitrogen The waste air flow from the distillation tower passes through the cooling device and is vented out of the environment through the UV0118 valve The nitrogen gas flow after being distilled at the tower will be returned to E31102 for cooling and transferred to the header system High pressure distillation tower C31101 and condensing device E31103 Technological diagram Distillation column contains high pressure column for distillate air and the condenser E31103 to produce the liquid nitrogen is shown in figure 2.14 Figure 2.14 The distillation tower Operating process: Gas flow from E31102 heat exchanger goes into high-pressure distillation device C31101 (with the temperature of -160 o C, pressure over 8-8.5 bar) Oxygen gas with boiling temperature -183 o Cwill be stopped first and go to the bottom of the tower C31101 (maintaining the pressure of 7.8-8.5 bar), nitrogen gas will go up on the top of the distillation column (with a pressure of 7.8-8.5 bar, the temperature is less than -183 o C) At this time the gas will be divided into lines, line will return to device E31102 to be cooled and supplied to the header with flow 420 38 Nm3/h, temperature 25 o C, pressure 0.7 bar, line will is fed into a condenserreboiler device to condense and then returned to the distillation tower by a pipe At device E31103 (pressure maintained at bottom of 3.9-4.5 bar, dew point temperature -73 o C), gas with high concentration of oxygen flow from distillation tower (pressure of 7.8-8.5 bar) will be led through Joule Thompson valve to reduce pressure (current gas will be decreased the pressure by valves up to 3.9-4.5 bar) and lead back to condense nitrogen, acetylene and unabsorbed hydrocarbons will form the drops, it will be transferred to the device E31102 then release to the environment by the vent Nitrogen gas flow after being condensed will return to the distillation tower, part of the mixture of nitrogen and oxygen gas will evaporate to near the top of the distillation column and will meet cold nitrogen line from E31103 which will cause nitrogen condensation and transfer to the tank T31201 The tank of nitrogen will be separated line to discharge the discharge of 336 Nm 3/h (80% of the design) in combination with the liquid oxygen line at the bottom of the tower, the air with high concentration of oxygen drain flow through the device E31104 to discharge vent, maintain the pressure productivity Nitrogen liquid storage tank unit It contains liquid nitrogen storage tank T31202 and devices (E31201 and E31202) for evaporating liquid nitrogen into gas It is shown in figure 2.15 Equipment: - Evaporator E31201 to increase pressure: When the pressure in the liquid nitrogen tank does not meet the requirements, liquid nitrogen flow will pass through the evaporator E31201 device to maintain the pressure for liquid nitrogen tank pressure - Evaporator E31202: When the demand for nitrogen is high, the evaporator will take liquid nitrogen from the tank through E31202 to supply nitrogen evaporator to the header - Nitrogen tank T31202 (volume of 25 m 3, pressure remain 7.6 bar, temperature lower than -196 o C) use to store liquid nitrogen, when nitrogen production produces exceed, vent discharge nitrogen gas will discharge nitrogen out of environment to maintain a level of 95% -100% of liquid nitrogen in the tank 39 Figure 2.15 The nitrogen storage tank Common problems and remedies: - Nitrogen pressure decreases: Because of high consumption of N consumers, there is not enough to supply We need to evaporate the liquid N in the tank by the device E31202 to provide enough for consumers - Low inlet gas pressure: Because the system uses a lot of compressed air, start adding a backup compressor to increase the pressure - Unstable O2 concentration: Because consumers use unstable nitrogen leading to the effect of nitrogen flow and pressure coming out, need to stabilize the consumption of nitrogen from unit 40 CHAPTER 3: CALCULATION OF THE HEAT TRANSFER AREA OF THE CONDENSER FOR PRODUCING 32 L/H LIQUID NITROGEN IN NITROGEN PRODUCTION UNIT 3.1 The introduction and construction of condenser – plate fin heat exchanger Plate fin heat exchanger (PFHE) is a type of heat exchanger that used in the chemical industry such as natural gas liquefaction, cryogenic air serperation, ammonia production, offshore processing, nuclear engineering, syngas production, aircraft cooling of bleed air and carbin air It consists fins (corrugated sheets) seperated by the layer of plates that assemble to transfer heat between fluids There are a lot of fins that make it possible to optimize the design But two basic forms that usually use in the industry are plain- fin and louvered-fin types If we design the PFHE, we need to require the specification of heat duty, allowable drop pressure and certain aspect of heat exchanger geometry For PFHE, each stream has difference heat transfer surface There are many manners to design PFHE but the common way to design is use the pressure drop with many correlations that find out in the book [11] such as Magahanic, Weiting Joshi and Webb correlations In nitrogen production unit in PVCFC, plate- fin heat exchanger is used to condense vapor nitrogen to liquid nitrogen with the flow 32 l/h for storing liquid nitrogen in the nitrogen storage tank with the volume 25 m3 that help the plant operate stably Figure 3.1 The construction of plate fin heat exchanger and cross flow arrangement Nowadays, there are a lot of alloys that can manufacture the plate-fin heat exchanger such as aluminium alloy plate fin heat exchangers thata have been used in the aircraft industry for more than 60 years, recently used in the cryogenic 41 seperation plants Stainless steels have been used in the aircraft over 30 years and chemical plants 3.2 Material balance and data for the calculation For the lower pressure column, it contains condenser for condensing vapor nitrogen to liquid nitrogen using the gas from the bottom of the distillation column and decrease the T and P by Joule Thompson valve In PVCFC, we have the data for the air feed into the distillation column 1106 Nm /h, and the products that we obtain 420 Nm 3/h vapor nitrogen that supply to header, 7.4 Nm3/h waste air (non-adsorbed hydrocarbon) and 32 l/h liquid nitrogen that produce in the condenser To condense the vapor nitrogen to liquid, we need to use the same amount of air in the LP column to exchange the temperature to condense vapor nitrogen We convert 32 l/h to 0.032 Nm 3/h (1 l/h = 0.001 m3/h) liquid nitrogen and Nm3/h = 0.28 kg/s And so, we have liquid nitrogen flow rate 0.032*0.28= 8.96*(kg/s) and the flow rate of air is also 8.96*(kg/s) The properties of two fluids in PVCFC are listed on the table 3.1 The properties Hot fluid (nitrogen) Cold fluid (air) Tin 96 K 74.5 K Tout 77 K 94 K The flow rate 8.96 kg/s 8.96 kg/s P(inlet) bar bar Allowable pressure drops 0.1 bar 0.1 bar Density(ρ) [12] 9.95 kg/m 100 kg/m3 Specific heat (Cp) [12] 1000 J/kg*K 1300 J/kg*K Viscosity (µ) [12] 0.01827 N*s/m 0.0178 N*s/m2 Prandtl number (Pr) 0.74767 0.75 Table 3.1 The properties of two fluids in both sides Where Prandtl number is calculated by the formula Cp*µ/k 3.3 Calculating the heat transfer area of plate fin heat exchanger for condensing vapor nitrogen to produce 32 l/h nitrogen liquid 3.3.1 The steps for the calculation based on the Magahanic correlation Table 3.2 The steps for calculating the plate fin heat exchanger [13] Step Detail Establish the heat transfer data spectification Assumption the data, calculate and choose the material for design Determine Colburn (j) and Friction factor (f) factor 42 Calculate the convective film factor Calculate fin efficiency and overall surface efficiency Calculate overall heat transfer coefficient, length of plate fin heat exchanger, diameter Calculate the pressure drop Summary of the results 3.3.2 The calculation of the heat transfer area based on the Magahanic correlation Heat transfer data spectification The parameter of fin are shown in the figure 3.3 Figure 3.2 The geometry of the fin surface Because the flow rate of vapor nitrogen is condensed is very small And so, based on the Magahanic correlation, we choose fin thickness (t) 0.2 mm, fin frequency(f) 714.25 fin per meter, fin length(l) 1.5 mm, fin height(h) 9.3 mm, The fin spacing(s) = – fin thickness = 1.2 mm Plate thickness(b)= fin height + fin thickness = 9.3 + 0.2 = 9.5 mm Free flow area(Aff) = ( fin spacing – fin thickness )* fin height = 9.6*10-6 m2 The frontal area(A)=( fin height + fin thickness)*( fin spacing + fin thickness )= 0.133*10-4 m2 43 Heat transfer area(As) = 2*h*l + 2*f*l + 2*h*t = 35.22 mm2 Fin area(Af) = 2*h*l + 2*h*t = 31.62 mm2 Equivalent diameter (D eq) = = 1.58 mm Fin area/ total surface area(Af/As) = 0.8977 Frontal area ratio (ϭ) = 9.3/13.3 = 0.69924 and α= = 7.75, δ= = 1.25, v= = 0.166 Assumption the material for fin is Al, the conductivity of the fin is 150 W/m.K End of plate thickness is (mm), end of the bar thickness is (mm) Assumption for the layers Table 3.3 The assumption data for the layers Wall temperature Width (w) No of layer Area between the plate (A=W*b*n) Free flow area (Aff=A*ϭ) Hot fluid (nitrogen) 200K 0.5 m 0.0237 m2 0.0166 m2 Cold fluid (air) 200K 0.5 m 0.019 m2 0.0133 m2 From the data in Table 3.1 and Table 3.3, we can calculate the convective heat exchanger coefficient Firstly, we calculate the heat load on the nitrogen vapor Because this is not counter-current flow, so we don’t need to calculate the mean temperature and the formula to calculate heat load: Q= m*Cp*(Tin-Tout) for nitrogen = 8.96*10-3*21*1000 = 188.16 (W) ∆T1= Tin (nitrogen)-Tout (air)= 96K – 94K = K ∆T2= 77K –74.5K = 2.5 K And so, we have ∆Tlm = = 2.24 We also have the formula to calculate the value of Q = U *A*∆Tlm => U*A = = 84 We want to find out the value of A (heat transfer area), we need to find the value of U (the overall heat transfer coefficient) Secondly, we need to estimate the value of U base on the given data Bulk temperature = = 87.5 (K) for hot fluid and for cold fluid = = 80.5 (K) Mean film temperature = For hot fluid = (87.5+200)/2 = 143.75 K For cold fluid = (80.5+200)/2 = 140.25 K The core mass velocity is calculated based on the formula G = For hot fluid = = 0.56 (kg/m2*s) 44 For cold fluid = = 0.67 (kg/m2*s) Calculate the Reynold no (Re) = For the hot fluid Re = = 48.43 For the cold fluid Re = = 59.5 The formula to calculate the Reynold number for j (Colburn factor) and f (Friction factor) for the Magahanic correlation is Ref = 648.25*)-0.06 *0.1 *-0.196 = 832.874 and Rej = 1568.58*(h/s)-0.217*(l/s)-1.433*(t/s)0.217 = 1077.7 Since the Reynold number for the j factor is the greater than f factor And so, the f and j factor are estimated by the formula below (for all hot and cold fluids) The formula to calculate the f factor = 0.32*Re-0.2869*(h/s)0.221*(l/s)-0.185*(t/s)-0.023 For hot fluid f(h) = 0.165 and f(c) = 0.156 And j factor is calculated by this formula j = 0.18*Re-0.42*)-0.288*-0.184*-0.05 For hot fluid j(h) = 0.0667 and j(c) = 0.061 To calculate the fin parameter, we need to estimate the heat transfer coefficient (h) h = (j factor*specific heat*core mass velocity)/ (Pr number)2/3 [14] For hot fluid h(hot) = = 45.35 For cold fluid h(cold) = = 64.36 With the values of h, thermal conductivity of Al, fin thickness, we can calculate the value of fin parameter M = , for hot fluid = = 54.98 mm and cold fluid = = 65.5 mm Calculate the fin efficiency nf = (with M is the fin parameter, l f is the length of the fin) With M*lf = (b is the plate thickness M is fin parameter) For hot fluid, M*lf = = 0.261, for cold fluid = = 0.32 The fin efficiency of hot fluid nf = = 0.978, for cold fluid = = 0.96 Calculate the overall fin efficiency No = 1- *(1-nf) (with Af/As is the ratio of fin area/ total surface area, nf is the fin efficiency) No (hot fluid) = 1- 0.8977*(1-0.978) = 0.98 and No (cold fluid) = 1- 0.8977*(1-0.96) = 0.96 Calculate the overall thermal resistance = + + ( with , No is the overall efficiency of the fin, K is the thermal conductivity of Al, a is the exponent in heat transfer correlation) 45 Ao/Aw is the ratio of total area per separating wall area = = 8.3857 (m 2/m3) (f is the fin frequency, t is the fin thickness, Af/As = 0.8977) We will have = + + = 0.0625 And so, overall heat transfer coefficient U o = 16 (W/m2*K) With the value of U*A= 84 => the value of A = 5.25 m2 Required heat transfer area/ length = 4Aff /Deq = 7.735 The length of heat exchanger = = 0.678 m Calculate the pressure drop p/L = (ρ is the density of the fluid, G is the core mass velocity, D is the equilibrium diameter, f is the f factor) For hot fluid, p/L = = 30 (N/m3) For cold fluid, p/L = = 49 (N/m3) Summary for the calculation Table 3.4 The summary of the results for the calculation Dimension Core length of heat exchanger Core width Heat exchanger area Overall heat transfer coefficient Overall efficiency Fin efficiency j factor f factor Value 0.678 m 0.5 m 5.25 m2 16 (W/m2*K) Hot fluid: 98%, cold fluid: 96.4% Hot fluid: 97.8%, cold fluid: 96% Hot fluid: 0.0667, cold fluid: 0.061 Hot fluid: 0.165, cold fluid: 0.156 We don’t have the data about the design of the condenser in PVCFC, so we can’t compare the data that we calculated with the design in the PVCFC But I think new algorithm calculated here is correct because all the formula is taken in heat transfer design hanbook 46 CONCLUSION The thesis was set out to know the process for producing the nitrogen gas and liquid as well as the technology and the devices for the most factories using in the nitrogen production Throughout the thesis, we have obtained the results that listed as below: • Learned the nitrogen production technology in PVCFC The quality of nitrogen vapor output is 99%; - The process and devices for producing nitrogen; - Incidents often occur in the nitrogen production unit in PVCFC such as turbine expander is broken that took to the unit stop working, concentration of O is unstable that make the pressure, concentration, and flow rate of nitrogen is not stable • Calculated the condenser which produce 32 l/h liquid nitrogen; - - Width: 0.5 m, Length: 0.678m and heat transfer area 5.25 m2; Overall efficiency for hot fluid: 98%, cold fluid: 96.4% 47 REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] https://en.nhandan.org.vn/business/item/6889902-vietnam-s-agriculturalexport-value-ranked-15th-in-the-world-deputy-minister.html,accessed 5/2019 https://sciencing.com/physical-properties-nitrogen-gas-2719.html,accessed 5/2019 PVCFC, GTDT HE THONG SAN XUAT KHI NEN, KHI DIEU KHIEN, KHI NITO (6/2015), Ca Mau, page 10 Pham Dinh Thanh, Internship report about the production of compressed, instrument air and nitrogen in PVCFC (12/2018), Ca Mau, page 4-8 http://www.pvcfc.com.vn/en-US/pvcfc-grows-steadily, accessed 5/2019 PVCFC, GTDT HE THONG SAN XUAT NUOC DEMI (30/6/2015), Ca Mau, page 12 PVCFC, GTDT HE THONG NOI HOI PHU TRO (6/2015), Ca Mau, page 22-30 PVCFC, GTDT HE THONG PHAN PHOI KHI NHIEN LIEU (6/2015), Ca Mau page 8-9, 12 PVCFC, TONG QUAN XUONG PHU TRO (2018), Ca Mau page 81 PVCFC, TONG QUAN XUONG PHU TRO (2018), Ca Mau page 86 G.T Polley, M.H Panjeh Shahi, M Picon- Nunez, Rapid design algorithms for shell- and- tube and compact heat exchanger, Trans IChemE 69, (Part A) (1991) 435-444 Robert H Perry, Don W Green, Perry’s Chemical Engineer’s Handbook, USA 1999, page 2-217, 2-218 T KUPPAN, Heat Exchanger Design handbook, The Ohio state University Columbus, Ohio, USA, 1999, page 211-213 T KUPPAN, Heat Exchanger Design handbook, The Ohio state University Columbus, Ohio, USA, 1999, page 211 ... moral support They are the most important people in my life and I dedicate this thesis for them Sincerely Pham Dinh Thanh TABLE OF CONTENTS LIST OF THE TABLES Table 2.1 The market share of PVCFC... the thesis “Introduction of the nitrogen production technology in Ca Mau fertilizer plant and calculation of the heat transfer area of the condenser” The objective of the thesis In this thesis, ... before synthetized gas enters the ammonia synthesis to avoid the poisoning of the synthesis of NH CH4 is formed have a role of an inert gas in the ammonia synthesis cycle, used catalyst is nickel-PK