Technical analysis of the boiler s work process

Transcription

1 Technical analysis of the boiler s work process XHEVAT BERISHA BEDRI DRAGUSHA University of Prishtina Faculty of Mechanical Engineering Prishtina - Kodra e Diellit pn. KOSOVO xhevatberisha@uni-pr.edu, bedridragusha@gmail.com Abstract: This paper analyzes the technical parameters of the boiler used for the production of polystyrene. The boiler has previously been built for burning solid fuel, coal, with low heat caloric value (LHV) Hu = 8000kJ/Kg. After the reconstruction, the boiler was adapted to burn liquid fuel, oil respectively. This polystyrene production device uses oil as fuel which has low heat caloric value Hu = 42,000 kj / kg. The average working temperature when using oil is t m = 15 o C. In addition, measurements are made in order to determine the amount of oil spent for realizing the production of saturated vapor with pressure p=8bar and temperature t = 125 o C. Key-Words: - Boiler, Polystyrene, Steam, Electricity, Oil, Coal 1 Introduction Kosovo polystyrene factory is built for the manufacture of polystyrene products, with different sizes and thicknesses, for the construction sector and other technical needs. This Update attempts to place the technology in context, beginning with an account of expandable polystyrene and how its evolution has responded to the demands of the market [1]. The styropor can be used as insulation material (houses and helms), but also as packaging material. Furthermore it is also handy as light foundation material, in road and construction sites or as an underground for floors (vibration absorption) [2]. There are also markets like food packaging and in horticulture, where the lightness and rigidity of EPS allows delicate products or plants to be handled without risk of damage. The long life and water resistance of EPS are important for different applications. It is also very useable in the casting process where molten metal is poured onto the foam which decomposes and leaves a precise cavity, for the metal to fill. Mounted equipment is ideal for high volume shape molding and medium volume block molding. Technical data for pre-expander are: outside dimension (LxWxH) 6.5x2.4x4.6m; weight 4t; expansion chamber diameter 1.1m; expansion chamber volume 1.6m 3 ; required volume height 5m; usable volume 1.2m 3. It also worth to mention that the machinery used for processing of EPS has developed to match the properties of the material, and is quite different from the one used for more conventional plastics processing [2]. The most relevant achievements in this sector are related to thermoplastic starch polymers resulting from processing native starch by chemical, thermal and mechanical means, and to its complexity to other co-polymers. The resulting materials show properties ranging from the flexibility of polyethylene to the rigidity of polystyrene, and can be soluble or insoluble in water as well as insensitive to humidity. Such properties explain the leading position of starchbased materials in the biodegradable polymer field [3]. 2. The technical parameters of the parameters 2.1 The technical parameters according to the manufacturer of machines According to the producer of the equipments, the technical data are as follows: Electricity consumption is 150kW, tension 480V, frequency 60Hz. The equipment uses the saturated steam (cleaned of oil and air), where the consumed steam is 1100kG/h at pressure 8-10bar. Consumption of fuel (oil) is lit/h. No mineralized water and water for cooling with following data: water expense 2000lit/h, water pressure 2bar, temperature of cold water 25 o C, pressure of cold water 4-5bar, value of ph for cold water 6.5-8pH, Hardness of water for cooling 10 o dh max (dh-degrees hardness) which is due to calcium and magnesium dissolved in water. ISBN:

2 Compressed air for the technological needs with following data: air amount about 4.2 m 3 /h, working pressure 6bar, the due temperature -40 o C and no mineralized water pressure 2bar. 2.2 The technical parameters according to the manufacturer of polystyrene Technical representatives of polystyrene factory have presented these technical data - the demand for thermal energy they are using equipment and machinery installed in the new department: Steam technology with technical parameters: o o Pressure of fresh steam 6-8bar Temperature of fresh steam 125 C Fresh steam produced by boiler which was installed in1995 and is built for burning solid fuel - coal with burning low heat value 8000 kj / kg. However, during 2000 the boiler was modified to produce steam using liquid fuel diesel these parameters: Burner with capacity kw with characteristics: o Consume of fuel oil (70-120)kg/h o Oil viscosity 1,5 E. According to technical data presented by the producers, for the time of use and carrying out production may occur following conclusions [4]: Effectively work time in one shift is 7[h] Oil consumption during one month is about 36 tons/month And based on the technical parameters for technological steam (saturated steam) present in the requirements of equipment manufacturers are: saturated steam with consumption 1100kg/h and pressure 8-10bar. The consumption of fuel (oil) is 25-80l/h. Based on the technical analysis realized which is given by the consumer (machines) block machines forms spends this amount of steam: D 2 = D 1 D 3 = kg/h (1) Where: D [ / 1 kg h] - Consumer of steam technology Preexpander D [ 2 kg / h ] - Consumer of steam technology Block Forma D [ kg/ h 3 ] - Consumer of steam technology equipment GTV Technical analysis and measurements 3.1 Specific Fuel Consumption The specific consumption of fuel oil, for steam production with amount of 1100 kg/h, according to previously defined parameters, is: 1. Specific oil consumption by equipment manufacturers d LD-HW = lt/h 2. Specific oil consumption by producer of polystyrene d LD-KP = 90,00 lt/h 3. Specific oil consumption according measurements d LD-LAB = 84,20 lt/h Figure 1 presents the specific fuel consumption for the three cases mentioned above [4]. 2.3 The technical parameters according to the producer of the machine Saturated steam consumption is given as follows: Average steam consumption kg/h Maximum steam consumption peak time 900kg/h Steam pressure 1.2bar ISBN:

3 Fig.1. Fuel consumption as measured d[l/h] 3.2 The time required to achieve the stationary state Measurements are made according to the criteria listed below: To realize the measurement of time needed to achieve the pressure and temperature of saturated steam (stationary state), which means to stop (turning off) the work of burner; Measurements should be carried out at the state cold of the work medium - water and unladed condition of the boiler; Measurements should be carried out three days with the condition that outside temperatures are the same (approximately). The measurement results: 1. First measurement I st, Time to reach stationary state t 1 =2h and 10min 2. Second measurement II d, Time to reach stationary state t 2 =2 h and 22 min. 3. Third measurement III d Time to reach stationary state t 3 =2 h and 15 min. The average time to reach stationary state is t mes = 2 h e 16min. Figure 2 depicts the time required for stationary state burner. Fig.2. Time required for stationary state burner Technical-economic analysis was performed based on energy balance and fuel consumption according to the following criteria: Criteria 1: Thermal energy produced from boiler Criteria 2: The amount of thermal energy by boiler producer, and Criteria 3: Technical-Economical analysis according to the producer Boiler is reconstructed to use oil as fuel, with low heat value HuN= kj/kg and efficiency of boilers for fuel oil is η= The below listed data will be taken into account for analysis and comparison, because the boiler of polystyrene factory has been constructed to use coal as fuel and then reconstructed to burn oil. Boiler was constructed to use a coal as fuel with low heat value H uth =8.000 kj/kg and boiler efficiency for solid fuel is η= Also it is used as criteria for comparison of results taken in to account the technical parameters of boiler which uses heavy oil as burning fuel. Low heat value of heavy oil fuel is H um = kj/kg and boiler efficiency is η= Technical-economic analysis will be conducted according to the equation on the fuel consumption to the amount of water vapor produced by the energy balance [5]: ISBN:

4 The amount of heat needed for the production of technological steam [6] Di i (2) Q = ( )[ kw] T s w η 2 = D KP =1,1 t/h=0.306 kg/s η 3 = D KP =1,1 t/h=0.306 kg/s The amount of heat obtained by burning fuel [6] Q B η H [ k W] (3) LD = LD K uld According to the equation (2) and (3) will be obtained the necessary amount of fuel for production technological steam [6]: D( is iw) BLD = [ kg / s] (4) η K HuLD Where are: QN [ kw ] - The needed amount of heat for steam production, Q [ ] LD kw - The obtained amount of heat by burning fuel, B [ / LD kg s ] - Fuel consumption, DkG [ / s] - Amount of produced steam H [ uld kj / kg] - Low heat fuel ηk [ ] - Efficiency of boiler is [ kj / kg] - Enthalpy of saturated steam for water iw [ kj / kg] - Enthalpy of feed water to boiler. Fig. 4. Efficiency and production of steam in boiler η 1 = D KP =0,278 kg/s =1,002 t/h η 2 = D KP =0,308 kg/s =1,110 t/h In Figure 3 and for is depict the efficiency and production of steam in boiler for different efficiency parameters. The gained performance values tell us that the boiler does not have the claimed production and that it does not work with the parameters (pressure and temperature of fresh steam saturated) declared by the technical personnel of factory which produces the polyestere. 4. Conclusion Based on technical-economic analysis conducted by taking into account the technical data presented (technical documentation, paperwork, situations, etc.) from polystyrene factory from manufacturer of mechanical equipment and on the measurements, the following conclusions are given: Fig. 3. Efficiency and production of steam in boiler η 1 = D KP =1,6 t/h=0.444 kg/s Taking into account the basic destination of boiler and according to the made analysis, it can be concluded as follows that this boiler does not meet the needs of produced steam to ISBN:

5 its technological needs, based on thermal calculations (energy balance). Also the boiler efficiency is low. This can be seen in the figures [3] and [4]. References [1]Xhevat Berisha, Techniacla-Economics Analysis, KosovaPlast Hani i Elezit, Plant for the Production of Thermal Insulation Materials, Prishtine, Kosovo, [2] Robin Britton, Update on Mouldable Particle Foam Technology, ismithers A Smithers Group Company, 2009 [3] David K. Platt, Biodegradable Polymers Market Report, Smithers Rapra Limited Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK, 2006 [4] Xhevat Berisha Analysis and synthesis of thermal network work regimes PhD thesis, Faculty of Mechanical Engineering, Prishtine, Kosovo, 2005 [5] H.Recknagel, E.Sprenger, E-R. Schramek: Taschenbuch für Heizung und Klimatechnik, INTERKLIMA,V.Banja 2005/06 [6] W. Linzer, Waermetechnische Anlagen, Institut fuer Technische Waermelehre, TU Wien, Auflage 1995 ISBN: