- Email: [email protected]
Simulation of Reaction in a Fluidized Bed Incinerator with Mixing Ratio of Double Based Propellant and Water
Mario R. Eden, Marianthi Ierapetritou and Gavin P. Towler (Editors) Proceedings of the 13th International Symposium on Process Systems Engineering – PSE 2018 July 1-5, 2018, San Diego, California, USA © 2018 Elsevier B.V. All rights reserved. https://doi.org/10.1016/B978-0-444-64241-7.50328-1
Simulation of Reaction in a Fluidized Bed Incinerator with Mixing Ratio of Double Based Propellant and Water Jiheon Leea*, Raymoon Hwang a, Hyunsoo Kim b, Jungsoo Park b, Min Oh c, Il Moon a a
Yonsei University, Seoul 03722, Republic of Korea Agency of Defence Development, Daejeon, Republic of Korea c Hanbat University, Daejeon, Republic of Korea [email protected] b
Abstract Recently, there have been various studies how to incinerate explosive waste safely due to environmental problems and safety problems. Explosive waste requires a new incineration mechanism, because of the pollution gas generated during the conventional treatment process, such as rotary kiln or outdoor exploration. This study focuses on the fluidized bed incinerator technology which can burn the target material using only a small amount of air at a relatively low temperature condition. In this study, we simulated the process of burning Double Based Propellant (DBP) mixed with water in the incinerator safely. The fluidized bed incinerator was modeled as a cylinder with a diameter of 0.5 m and a height of 2.0 m, and a case study was carried out by changing the mixing ratio of the injected slurry. As a result, we confirmed the optimal mixing ratio with water for burning DBP without explosion, and confirmed that DBP combustion and decomposition reaction occurring inside the incinerator can be safely simulated. Based on this, it is considered that the design of the actual incinerator will provide a new direction for research on the explosive waste treatment process in Korea in the future. Keywords: Fluidized bed, Double based propellant, water composition, simulation.
1. Introduction Methods of disposing of explosive wastes, such as ammunition and propellants, have been used for incineration or for exploitation in the open air. However, it has various problems such as environmental problems caused by combustion gases and safety problems of processing facilities. In Korea, about 3,000 tons of explosive waste are generated annually, and 9,700 tons of waste propellant is being loaded untreated due to lack of proper treatment facilities. In the past, research on the incineration process using a rotary kiln has been carried out, but the safety problem has not been solved and the incineration process using a fluidized bed incinerator has been proposed. The treatment process using the fluidized bed incinerator has a higher rate of complete combustion than the conventional method and the combustion gas emission is remarkably low, and the efficiency of operation is also high due to the characteristics of the fluidized bed. Also, by utilizing the effect of mixing with the charged particles in the reactor, the heat energy generated during combustion is efficiently dispersed, thereby reducing the possibility of high temperature or overpressure. In this study, the optimum conditions of
2000
J. Lee et al.
the flow phenomenon and mixing effect in the incinerator were determined through the previous study of the cold model of the fluidized bed reactor. Based on this, the process of burning the waste propellant in the incinerator was designed, and the computational fluid dynamics program was used to simulate and analyze the particle behavior, the internal temperature change, and the gas component change.
2. Simulation scheme and condition 2.1 Design of fluidized bed The fluidized bed incinerator simulated in this study was selected based on previous studies to determine optimal fluidization conditions. [1] The fluidized-bed incinerator shown in Figure 1 is designed as a cylinder with a height of 2.0 m and a diameter of 0.5 m and a fluidization of 440 K is introduced at a speed of 0.5 m / s under the incinerator. Inside, sand particles with a diameter of 260 μm were charged to 30% of the height of the incinerator. After fluidization reaches a steady state, slurry particles are injected at the side of 1.1 m in height and burned. The slurry is a mixture of water and Double based propellant (DBP) at a ratio of 1: 1 for the stability of process and reaction, and its size is 3 mm in diameter. DBP is a mixture of Nitrocellulose 52% and Nitroglycerin 48%. [8] 2.2 Double based propellant combustion reaction DBP has a total of seven reaction mechanisms until complete decomposition. When water evaporates as heat is applied, conditions are set for DBP to ignite, and degradation occurs from the surface, resulting in gas generation and combustion in a chain. The two reactions occurring in the condensed phase are the degradation and gasification reactions of DBP, respectively [9] In the gas phase, there are two secondary reactions to NO2, a reaction to NO-carbon, and three secondary reactions to aldehyde and NO. Table 1: Thermochemical parameters of double based propellant
Figure 1: Schemes of fluidized bed incinerator
ݐ݈݈݊ܽ݁ݎܲ݀݁ݏܾ݈ܾܽ݁ݑܦ՜ ʹǤͶͻܱܰଶ ʹǤ͵ܪܥଶ ܱ ͳǤʹሺܱܪܥሻଶ ͲǤͳ ܱܥ ݉݅݊݁ݑ݀݅ݏ݁ݎݎ (1)
Fluidized Bed Incinerator with Double Based Propellant and Water
2001
ܱܰଶ ͲǤͷܪܥଶ ܱ ͲǤͳሺܱܪܥሻଶ ՜ ܱܰ ͲǤ͵ͺ ܱܥ ͲǤͷܱܥଶ ͲǤͷܪଶ ܱ ͲǤʹʹܪଶ (2) ܱܰଶ ͲǤͷܪܥଶ ܱ ͲǤͳሺܱܪܥሻଶ ՜ ܱܰ ͲǤ͵ͺ ܱܥ ͲǤͷܱܥଶ ͲǤͷܪଶ ܱ ͲǤʹʹܪଶ (3) ܪܥଶ ܱ ܪܥଶ ܱ ՜ ܱܥ ͲǤͷܥଶ ܪସ ܪଶ ܱ
(4)
ሺܱܪܥሻଶ ሺܱܪܥሻଶ ՜ Ͷ ܱܥ ʹܪଶ
(5)
ܱܰ ͲǤͳ ܱܥ ͲǤͳʹܥଶ ܪସ ͲǤͳʹܪଶ ՜ ͲǤͷܰଶ ͲǤͶܱܥଶ ͲǤ͵ܪଶ ܱ
(6)
ܥ ܱܰ ՜ ܱܥ ܱܰଶ
(7)
Eq.(2) and Eq.(3) are the same reaction but different reactions occurring in the condensed phase and gas phase, respectively. The reaction heat of the DBP decomposition reaction in the condensed phase is about 1,100 cal/g [2, 3, 4, 5, 6, 7, 8]. The units are the same in kg/m3·s. The thermochemical parameters of the reactions are shown in Table 1. All values were calculated in previous studies or calculated using the measured values. [8] 2.3 Fluidization condition
Figure 2: Sequence of slurry injection
Figure 3: Fludization and mixing effect of fluidized bed incinerator
Before injecting DBP to make safe combustion conditions, the inside of the reactor must reach a steady state where flow phenomenon occurs. Figure 2 shows that all the sand particles are mixed and flow phenomenon occurs actively after 15 seconds. [1]
J. Lee et al.
2002
3. Simulation result and analysis 3.1. Particle movement analysis Figure 3 simulates the inside of the reactor when the slurry is injected. After the slurry is injected, the water evaporates as it drops, and its size gradually decreases. Thereafter, the reaction occurs instantaneously between the sand particles. This can be confirmed by the fact that the sand particles are spread around the slurry. Thus, it was confirmed that the sand particles absorb the gas generation impact caused by combustion and protect the inner wall of the reactor. And the disappearance time of the particles is 0.28 seconds after the first injection, which is a very short time. Therefore, DBP decomposition reaction is very fast reaction. 3.2. Temperature profile In Figure 4, temperature changes were observed in the reactor from 15.28 seconds when the slurry particles disappeared, and temperature changes were irregular spherical hot spots. In each case, the temperature of the hot spot was 901, 964, 1003K for each case, and then the gas exited over the incinerator as heat energy was dispersed. It takes about 0.7 seconds for gas to escape to the incinerator. As the water ratio increased, the temperature of the hot spot decreased.
Figure 4: Hot spot profile, (a)5:5, (b)6:4, (c)7:3 (DBP:Water)
Fluidized Bed Incinerator with Double Based Propellant and Water
2003
Figure 5 Flow rates of NO by time. (a)5:5, (b)6:4, (c)7:3
3.3 Flue gas analysis Figure 5 shows the fluctuation of air flow at the time of reaction. This is because the reaction occurs rapidly and a large amount of gas is generated in a short time and the air is pushed up irregularly to the top. As a result of the analysis of the components, the chemical species generated at the time of disappearance of the hot spot starts to escape to the upper part of the reactor. Only N2, O2, H2O and CO2 should be observed at the upper part of the incinerator if complete combustion actually occurs. However, since incomplete combustion products such as NOx and aldehyde are observed, it can be seen that the gas is pushed up before complete combustion occurs. Also, as the water ratio decreases, the incomplete combustion products decrease, because the rate at which the reactants burn is faster.
4. Conclustion In this study, CFD is used to explain the mechanism of the combustion of pulsed propellant without explosion in a fluidized bed incinerator. The maximum temperature of the generated hot spot was about 1000 K. As the water ratio increased, the temperature of the hot spot was lowered and the reaction rate was slowed down. The results of all cases are within the range that does not affect the physical properties of the reactor or packed particles. It was found that the feed ratio (water: DBP), the superficial velocity, and the size of the sand particles were found to have a great influence on the design of the operation condition, and energy optimization for this need to be further performed. As a result of the simulation, some of the gas produced after the reaction escapes to the top of the incinerator without being completely combusted, which can be treated by designing an additional downstream separation purification process. If the simulated fluidized bed incinerator model is designed according to the actual process size, it can process 2,100 tons of waste propellant per year. These studies are
2004
J. Lee et al.
expected to contribute greatly to the disposal of accumulated pulmonary propellants in Korea.
5. Acknowledgement This study was supported by CEMRC and Agency of Defence Development.
References [1] Jiheon Lee, et al. “Calculation of Optimum Operating Conditions by Cold Model Simulation of Fluidized Bed Reactor Incinerator in Explosive Waste Incineration Process,” Theories and Applications of Chemical Engineering, 22 (1), p.727,April 2016. [2] T.S. Roh, Tseng, Yang,. "Effects of Acoustic Oscillations on Flame Dynamics of Homogeneous Propellants in Rocket Motors," Journal of Propulsion and Power Vol. 11, No. 4, July 1995. [3] Song, Y. H., Beer, J. M., and Sarofim, A. F., “Reduction of Nitric Oxide by Coal Char at Temperatures of 1250-1750K,“ Combustion Science and Technology. Vol. 25, pp.237-240, 1981. [4] Lengelle, G., Bizot, A., Duterque, J., and Trubert, J. F., “Steady-State Burning of Homogeneous Propellants,“ Fundamentals of Solid-Propellant Combustion, edited by K. K. Kuo and M. Summerfield, Vol. 90, Progress in Astronautics and Aeronautics, AIAA, New York, pp.361-407, 1984. [5] Bizot, A., and Beckstead, M. W., “A model for Double-Base Propellant Combustion,“ Proceedings of the 22nd Symposium on Combustion, The combustion Inst., Pittsburgh, PA, pp. 1827-1834, 1988. [6] Faddoul, F., Most, J. M., and Joulain, P., “ Combustion Kinetic of a Homogeneous Double Base Propellant,“ Dynamics of Deflagrations and Reactive System-Flames, edited by A. L. Kuhl, Vol. 131, Progress in Astronautics and Aeronautics, AIAA, Washington, DC, pp. 275-296, 1989. [7] Lengelle, G., Duterque, J., Godon, J. C., and Trubert, J. F., “Solid Propellant Steady Combustion: Physical Aspects,“ AGARD Lecture Series 180, 1991. [8] Kubota. N., “Determination of Plateau Burning Effect of Catalyzed Double-Base Propellant,“ Proceedings of the 17th Symposium on Combustion,, The Combustion Inst., Pittsburgh, PA, pp. 1435-1441, 1979 [9] Aoki, I., and Kubota, N., “Combustion Wave Structures of High and Low-Energy Double-Base Propellants,“ AIAA Journal, Vol. 20,pp.100-105, 1982
Simulation of Reaction in a Fluidized Bed Incinerator with Mixing Ratio of Double Based Propellant and Water Jiheon Leea*, Raymoon Hwang a, Hyunsoo Kim b, Jungsoo Park b, Min Oh c, Il Moon a a
Yonsei University, Seoul 03722, Republic of Korea Agency of Defence Development, Daejeon, Republic of Korea c Hanbat University, Daejeon, Republic of Korea [email protected] b
Abstract Recently, there have been various studies how to incinerate explosive waste safely due to environmental problems and safety problems. Explosive waste requires a new incineration mechanism, because of the pollution gas generated during the conventional treatment process, such as rotary kiln or outdoor exploration. This study focuses on the fluidized bed incinerator technology which can burn the target material using only a small amount of air at a relatively low temperature condition. In this study, we simulated the process of burning Double Based Propellant (DBP) mixed with water in the incinerator safely. The fluidized bed incinerator was modeled as a cylinder with a diameter of 0.5 m and a height of 2.0 m, and a case study was carried out by changing the mixing ratio of the injected slurry. As a result, we confirmed the optimal mixing ratio with water for burning DBP without explosion, and confirmed that DBP combustion and decomposition reaction occurring inside the incinerator can be safely simulated. Based on this, it is considered that the design of the actual incinerator will provide a new direction for research on the explosive waste treatment process in Korea in the future. Keywords: Fluidized bed, Double based propellant, water composition, simulation.
1. Introduction Methods of disposing of explosive wastes, such as ammunition and propellants, have been used for incineration or for exploitation in the open air. However, it has various problems such as environmental problems caused by combustion gases and safety problems of processing facilities. In Korea, about 3,000 tons of explosive waste are generated annually, and 9,700 tons of waste propellant is being loaded untreated due to lack of proper treatment facilities. In the past, research on the incineration process using a rotary kiln has been carried out, but the safety problem has not been solved and the incineration process using a fluidized bed incinerator has been proposed. The treatment process using the fluidized bed incinerator has a higher rate of complete combustion than the conventional method and the combustion gas emission is remarkably low, and the efficiency of operation is also high due to the characteristics of the fluidized bed. Also, by utilizing the effect of mixing with the charged particles in the reactor, the heat energy generated during combustion is efficiently dispersed, thereby reducing the possibility of high temperature or overpressure. In this study, the optimum conditions of
2000
J. Lee et al.
the flow phenomenon and mixing effect in the incinerator were determined through the previous study of the cold model of the fluidized bed reactor. Based on this, the process of burning the waste propellant in the incinerator was designed, and the computational fluid dynamics program was used to simulate and analyze the particle behavior, the internal temperature change, and the gas component change.
2. Simulation scheme and condition 2.1 Design of fluidized bed The fluidized bed incinerator simulated in this study was selected based on previous studies to determine optimal fluidization conditions. [1] The fluidized-bed incinerator shown in Figure 1 is designed as a cylinder with a height of 2.0 m and a diameter of 0.5 m and a fluidization of 440 K is introduced at a speed of 0.5 m / s under the incinerator. Inside, sand particles with a diameter of 260 μm were charged to 30% of the height of the incinerator. After fluidization reaches a steady state, slurry particles are injected at the side of 1.1 m in height and burned. The slurry is a mixture of water and Double based propellant (DBP) at a ratio of 1: 1 for the stability of process and reaction, and its size is 3 mm in diameter. DBP is a mixture of Nitrocellulose 52% and Nitroglycerin 48%. [8] 2.2 Double based propellant combustion reaction DBP has a total of seven reaction mechanisms until complete decomposition. When water evaporates as heat is applied, conditions are set for DBP to ignite, and degradation occurs from the surface, resulting in gas generation and combustion in a chain. The two reactions occurring in the condensed phase are the degradation and gasification reactions of DBP, respectively [9] In the gas phase, there are two secondary reactions to NO2, a reaction to NO-carbon, and three secondary reactions to aldehyde and NO. Table 1: Thermochemical parameters of double based propellant
Figure 1: Schemes of fluidized bed incinerator
ݐ݈݈݊ܽ݁ݎܲ݀݁ݏܾ݈ܾܽ݁ݑܦ՜ ʹǤͶͻܱܰଶ ʹǤ͵ܪܥଶ ܱ ͳǤʹሺܱܪܥሻଶ ͲǤͳ ܱܥ ݉݅݊݁ݑ݀݅ݏ݁ݎݎ (1)
Fluidized Bed Incinerator with Double Based Propellant and Water
2001
ܱܰଶ ͲǤͷܪܥଶ ܱ ͲǤͳሺܱܪܥሻଶ ՜ ܱܰ ͲǤ͵ͺ ܱܥ ͲǤͷܱܥଶ ͲǤͷܪଶ ܱ ͲǤʹʹܪଶ (2) ܱܰଶ ͲǤͷܪܥଶ ܱ ͲǤͳሺܱܪܥሻଶ ՜ ܱܰ ͲǤ͵ͺ ܱܥ ͲǤͷܱܥଶ ͲǤͷܪଶ ܱ ͲǤʹʹܪଶ (3) ܪܥଶ ܱ ܪܥଶ ܱ ՜ ܱܥ ͲǤͷܥଶ ܪସ ܪଶ ܱ
(4)
ሺܱܪܥሻଶ ሺܱܪܥሻଶ ՜ Ͷ ܱܥ ʹܪଶ
(5)
ܱܰ ͲǤͳ ܱܥ ͲǤͳʹܥଶ ܪସ ͲǤͳʹܪଶ ՜ ͲǤͷܰଶ ͲǤͶܱܥଶ ͲǤ͵ܪଶ ܱ
(6)
ܥ ܱܰ ՜ ܱܥ ܱܰଶ
(7)
Eq.(2) and Eq.(3) are the same reaction but different reactions occurring in the condensed phase and gas phase, respectively. The reaction heat of the DBP decomposition reaction in the condensed phase is about 1,100 cal/g [2, 3, 4, 5, 6, 7, 8]. The units are the same in kg/m3·s. The thermochemical parameters of the reactions are shown in Table 1. All values were calculated in previous studies or calculated using the measured values. [8] 2.3 Fluidization condition
Figure 2: Sequence of slurry injection
Figure 3: Fludization and mixing effect of fluidized bed incinerator
Before injecting DBP to make safe combustion conditions, the inside of the reactor must reach a steady state where flow phenomenon occurs. Figure 2 shows that all the sand particles are mixed and flow phenomenon occurs actively after 15 seconds. [1]
J. Lee et al.
2002
3. Simulation result and analysis 3.1. Particle movement analysis Figure 3 simulates the inside of the reactor when the slurry is injected. After the slurry is injected, the water evaporates as it drops, and its size gradually decreases. Thereafter, the reaction occurs instantaneously between the sand particles. This can be confirmed by the fact that the sand particles are spread around the slurry. Thus, it was confirmed that the sand particles absorb the gas generation impact caused by combustion and protect the inner wall of the reactor. And the disappearance time of the particles is 0.28 seconds after the first injection, which is a very short time. Therefore, DBP decomposition reaction is very fast reaction. 3.2. Temperature profile In Figure 4, temperature changes were observed in the reactor from 15.28 seconds when the slurry particles disappeared, and temperature changes were irregular spherical hot spots. In each case, the temperature of the hot spot was 901, 964, 1003K for each case, and then the gas exited over the incinerator as heat energy was dispersed. It takes about 0.7 seconds for gas to escape to the incinerator. As the water ratio increased, the temperature of the hot spot decreased.
Figure 4: Hot spot profile, (a)5:5, (b)6:4, (c)7:3 (DBP:Water)
Fluidized Bed Incinerator with Double Based Propellant and Water
2003
Figure 5 Flow rates of NO by time. (a)5:5, (b)6:4, (c)7:3
3.3 Flue gas analysis Figure 5 shows the fluctuation of air flow at the time of reaction. This is because the reaction occurs rapidly and a large amount of gas is generated in a short time and the air is pushed up irregularly to the top. As a result of the analysis of the components, the chemical species generated at the time of disappearance of the hot spot starts to escape to the upper part of the reactor. Only N2, O2, H2O and CO2 should be observed at the upper part of the incinerator if complete combustion actually occurs. However, since incomplete combustion products such as NOx and aldehyde are observed, it can be seen that the gas is pushed up before complete combustion occurs. Also, as the water ratio decreases, the incomplete combustion products decrease, because the rate at which the reactants burn is faster.
4. Conclustion In this study, CFD is used to explain the mechanism of the combustion of pulsed propellant without explosion in a fluidized bed incinerator. The maximum temperature of the generated hot spot was about 1000 K. As the water ratio increased, the temperature of the hot spot was lowered and the reaction rate was slowed down. The results of all cases are within the range that does not affect the physical properties of the reactor or packed particles. It was found that the feed ratio (water: DBP), the superficial velocity, and the size of the sand particles were found to have a great influence on the design of the operation condition, and energy optimization for this need to be further performed. As a result of the simulation, some of the gas produced after the reaction escapes to the top of the incinerator without being completely combusted, which can be treated by designing an additional downstream separation purification process. If the simulated fluidized bed incinerator model is designed according to the actual process size, it can process 2,100 tons of waste propellant per year. These studies are
2004
J. Lee et al.
expected to contribute greatly to the disposal of accumulated pulmonary propellants in Korea.
5. Acknowledgement This study was supported by CEMRC and Agency of Defence Development.
References [1] Jiheon Lee, et al. “Calculation of Optimum Operating Conditions by Cold Model Simulation of Fluidized Bed Reactor Incinerator in Explosive Waste Incineration Process,” Theories and Applications of Chemical Engineering, 22 (1), p.727,April 2016. [2] T.S. Roh, Tseng, Yang,. "Effects of Acoustic Oscillations on Flame Dynamics of Homogeneous Propellants in Rocket Motors," Journal of Propulsion and Power Vol. 11, No. 4, July 1995. [3] Song, Y. H., Beer, J. M., and Sarofim, A. F., “Reduction of Nitric Oxide by Coal Char at Temperatures of 1250-1750K,“ Combustion Science and Technology. Vol. 25, pp.237-240, 1981. [4] Lengelle, G., Bizot, A., Duterque, J., and Trubert, J. F., “Steady-State Burning of Homogeneous Propellants,“ Fundamentals of Solid-Propellant Combustion, edited by K. K. Kuo and M. Summerfield, Vol. 90, Progress in Astronautics and Aeronautics, AIAA, New York, pp.361-407, 1984. [5] Bizot, A., and Beckstead, M. W., “A model for Double-Base Propellant Combustion,“ Proceedings of the 22nd Symposium on Combustion, The combustion Inst., Pittsburgh, PA, pp. 1827-1834, 1988. [6] Faddoul, F., Most, J. M., and Joulain, P., “ Combustion Kinetic of a Homogeneous Double Base Propellant,“ Dynamics of Deflagrations and Reactive System-Flames, edited by A. L. Kuhl, Vol. 131, Progress in Astronautics and Aeronautics, AIAA, Washington, DC, pp. 275-296, 1989. [7] Lengelle, G., Duterque, J., Godon, J. C., and Trubert, J. F., “Solid Propellant Steady Combustion: Physical Aspects,“ AGARD Lecture Series 180, 1991. [8] Kubota. N., “Determination of Plateau Burning Effect of Catalyzed Double-Base Propellant,“ Proceedings of the 17th Symposium on Combustion,, The Combustion Inst., Pittsburgh, PA, pp. 1435-1441, 1979 [9] Aoki, I., and Kubota, N., “Combustion Wave Structures of High and Low-Energy Double-Base Propellants,“ AIAA Journal, Vol. 20,pp.100-105, 1982