- Email: [email protected]
Hydrate formation in the cyclic process of refrigerant boiling-condensation in a water volume
International Journal of Heat and Mass Transfer 108 (2017) 1320–1323
Contents lists available at ScienceDirect
International Journal of Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ijhmt
Technical Note
Hydrate formation in the cyclic process of refrigerant boilingcondensation in a water volume A.A. Chernov a,b,⇑, D.S. Elistratov a, I.V. Mezentsev a, A.V. Meleshkin a, A.A. Pil’nik a,b a b
Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia Novosibirsk State University, Novosibirsk 630090, Russia
a r t i c l e
i n f o
Article history: Received 5 August 2016 Received in revised form 24 November 2016 Accepted 5 December 2016 Available online 19 January 2017 Keywords: Hydrate formation Liquid-gas system Boiling Condensation
a b s t r a c t Conceptually new method of hydrate production is proposed. It is based on self-organization of the refrigerant boiling-condensation process in enclosed water volume. The key feature of the method is a high hydrate production rate combined with a comparatively low power consumption allowing us to expect the high effectiveness of the technologies based on it. The set of experiments was carried out. The gas hydrate of refrigerant R134a was produced. The criteria of intensification of the hydrate formation process are formulated. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction One fundamental problem of oil and gas industry is the formation and deposition of gas hydrates in the oil and gas fields and in the systems of underground and overground equipment. Thus, in the past the most of the studies were aimed at finding new methods of prevention the hydrate formation. But now the emphasis is shifted towards the perspective of using hydrates and the process of hydrate formation in practice [1,2]. For example, one economically sound method of gas transportation in the absence of gas pipeline involves conversion of gas into gas hydrate, transporting it in the solid state under static pressure and low temperatures. Such transportation method is the most profitable for small oil-gas fields and the collateral effect can be achieved by simultaneous realization of gas and clean water remained after gas-hydrate decomposition. Another use of hydrate technologies is the gas storage (in the gas-hydrate state) near large consumer. Man-caused hydrate formation processes can also be used outside the oil and gas industry for desalination of sea water, gases separation, fog elimination, heat accumulation, creation of efficient refrigeration cycles and others. Gas hydrate technologies can also help solve global ecological problems. One promising, for the large-scale use method of greenhouse gases utilization involves gas conversion into the gas ⇑ Corresponding author at: Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia. E-mail address: [email protected] (A.A. Chernov). http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.12.035 0017-9310/Ó 2016 Elsevier Ltd. All rights reserved.
hydrate state and storing it at the ocean bottom under low temperature and high pressure. Obviously, the main factor ensuring the financial viability of such technologies is the rate of hydrate formation. As a result, we set the objective to develop a fast and cost-effective method of hydrate production. The currently existing technologies of hydrate production are based on: intensive mixing of gassaturated water, fine dispersion of water jet in gas atmosphere, vibratory and supersonic influence on a bubble medium and so on. However, the majority of above-mentioned methods can be characterized by a low hydrate production rate and as a result low efficiency of plants based on them. A lot of works were devoted to the topic of gas hydrates. The most important of them are the studies of a gas-hydrate structure, its physicochemical, thermophysical, mechanical and other properties, the general conditions needed for their formation and their growth mechanisms [3–7]. Great attention is paid to the methods of studying both natural and man-made gas hydrates [8–12]. A large number of works are devoted to experimental and mathematical modeling of the processes of formation and decomposition of gas hydrates [13–18]. Comparatively recently a new hydrate formation method caused by the shock wave impact in a bubble medium [19–23] has been proposed. It allows the formation of different gas hydrates over a short period of time. In this work we propose conceptually new hydrate production method based on the self-organization of the cyclic boilingcondensation process.
A.A. Chernov et al. / International Journal of Heat and Mass Transfer 108 (2017) 1320–1323
2. Some information about gas hydrates Gas hydrate is a solid crystalline compound that forms under certain temperature and pressure conditions, from water (liquid water, ice or water vapor) and a low-molecular gas. Gas hydrates are categorized as the so-called clathrate compounds or compounds where gas molecules (”guest”) are trapped in the molecular cavities of the ice-like molecular structure (‘‘host”) formed by water molecules via hydrogen bonds. Gas molecules (‘‘guests”) is bonded with the structure (‘‘host”) only by Van der Waals forces without forming chemical bonds. The general formula of a gas hydrate is as follows MnH2 O, where M means the guest molecule; n—number of water molecules per one guest molecule. Number n is a variable and depends on the type of gas, pressure and temperature. One of unique properties of gas hydrates is the ability of trapping 70–300 gas volumes for one water volume. For example, 1 m3 of methane hydrate can carry 160 m3 of gas and the volume occupied by gas in a gas hydrate is less than 20%. The density of gas hydrate is typically less than the density of water and ice (for methane hydrate it is 900 kg/m3). After the increase in temperature and the decrease in pressure the hydrate decompose into gas and water absorbing great amount of heat in the process. 3. Experimental setup The experiments were done using the experimental setup (Fig. 1(a)) with the working section consisting of a parallelepiped pressure-tight chamber with the inside dimensions of 150 150 740 mm made of 15 mm thick stainless steel. The setup can withstand the pressure of up to 10 MPa. Two inspection windows (24 mm thick plexiglass) allow us to register hydrodynamic and thermophysic processes inside the chamber using high-speed photography. Detectors OWEN PD-100 and RT.50 VK1P were used to measure the pressure and temperature fields. The cooling was done through the side walls using the cooling jacket. Circulation thermostat LOIP FT-316-40 with working temperature range from 40 C to 100 C) and cooling liquid with crystallization temperature of 40 C were used. For the ambient temperature of 20 C the cooling rate was 770 W. Bottom part of
1321
the chamber was equipped with heater (up to 500 W). It was used to induce the intensive boiling of hydrating gas in the bottom part of the working section. The refrigerant R134a was used in the experiments as a hydrating gas. 4. Method description. Results The main principle of the proposed method is as follows. Working section is half filled with water. The water is cooled down to temperature 2–5 °C (temperature and pressure conditions are chosen so that hydrate formation is always possible the system). At the start of the process the gaseous refrigerant is supplied into the chamber. The refrigerant rapidly condenses at the cold walls of the chamber, streams down to the bottom of the unit and forms a liquid layer. At this stage the heater mounted into the bottom part of the working section turns on. The heating intensity is chosen so that the liquid refrigerant layer starts to actively boil. During their ascent to the colder area bubbles generated from the boiling rapidly become covered with hydrate shells. The shell has a friable and porous structure of overlapping flakes of gas hydrate. It appears that the gas always has a free access to the water at the interphase (hydrate shell offer no substantial diffusion resistance). It means that the hydrate mass growth rate in this process is not limited by diffusion (as we became used to) but is controlled by convective heat transfer at the interphase. Hydrate formation rate is high in such a process because the heat exchange processes are much faster than diffusion-driven processes. After arising to the free surface of the liquid and collapsing bubbles leave flakes of gas hydrate. As a result gas hydrate cap is growing above the liquid (Fig. 1(b)). The refrigerant remained from the formation of gas hydrate in the first cycle of the process condenses at the walls of working section in form of droplets, streams down to the bottom of the chamber and mixes with already boiling layer. Obviously, this process is a cyclic one and it continues until all refrigerant transforms into gas hydrate. Fig. 2(a) shows experimental dependencies of temperature and pressure in liquid near the heater and near the surface on time. It can be seen that in the course of the process the bottom layer temperature is higher than the equilibrium boiling point of refrigerant. But the upper layers of liquid stay cold. Change in refrigerant boil-
Fig. 1. (a) The scheme of experimental setup: 1—side wall with cooling jacket; 2—working section; 3—pressure gauge; 4—thermostat; 5—temperature detectors; 6—gas cylinder; 7—ADC & PC. (b) Gas hydrate produced during the experiment.
1322
A.A. Chernov et al. / International Journal of Heat and Mass Transfer 108 (2017) 1320–1323
Fig. 2. (a) Experimental dependences of liquid temperature T in the working section near the heater (diamonds) and near the free surface (circles) and pressure P on time t; thick solid line—the boiling curve. (b) The process in the P T Diagram; thick solid line – the boiling curve. The cyclic process of R134a boiling-condensation is schematically presented in the figure.
ing temperature is also illustrated in the figure. It is caused by the change in the pressure due to hydrate formation. Let us note that there is a good reason for temperature behaving in such a way. The process was controlled by the intensity of cooling at the walls of the working section and by the heating at the bottom of the chamber (the intensity of the former was higher than the intensity of the later as evidenced by the lowering of the temperature in the working section). It was done so that the hydrating gas participate in the aforementioned cycle at all times during the experiment. Such a cycle is shown in Fig. 2(b), clearly demonstrates the process at hand in the P T diagram. Let us not that the whole experiment during which the major portion of refrigerant turns into gas hydrate lasted around half an hour. It is significantly less than the time of hydrate formation in known industrial methods. The mass of gas hydrate produced in the experiments was 1–2 kg. Xray diffraction patterns confirm the presence of substantial fraction of hydrate in hydrate mass (which consists of gas hydrate and ice). We would like to bring your attention to the set of criteria implemented in this work that in our opinion led to the intensification of the process of gas hydrate formation. Briefly they can be listed as follows. Developed phase contact area was created. Obviously, this stimulates the process of gas hydrate formation (gas hydrate grows at the gas-water boundary). Gas hydrate formed on the phase contact area did not hinder the free access of the gas to the water (gas hydrate growth rate is limited by the heat transfer on the interphase and not by the diffusion process). Intensive (in our case convective) heat transfer was established because it determines the growth rate of gas hydrate mass. Finally, the conditions was created when the supercooling of the system relative to gas hydrate formation equilibrium curve is maximized (facilitates kinetics of gas hydrate formation and increases heat transfer).
5. Conclusions New hydrate production method is developed. It is based on self-organization of the boiling-condensation process in enclosed water volume. The method is defined by a good energy efficiency. It is shown that the intensification of hydrate formation process is caused by the forming of the developed interphase surface, the rapid cooling of the medium and the intensive mixing of liquid and gas phases. The gas hydrate of refrigerant R134a was produced. Diffraction patterns confirm the presence of substantial fraction of gas hydrate in the solid phase. The method developed
in this work can be used to create new cost-effective methods and technologies of producing gas hydrates. Acknowledgements This work was supported by the Russian Science Foundation (project # 15-19-10025). We express our gratitude to the Novosibirsk State University for giving us an access to the library. References [1] Y.F. Makogon, Hydrates of Hydrocarbons, PennWell books, 1997. [2] E. Sloan, C. Koh, Clathrate Hydrates of Natural Gases, third ed., Chemical Industries, CRC Press, 2007. [3] A. Kumar, T. Sakpal, P. Linga, R. Kumar, Enhanced carbon dioxide hydrate formation kinetics in a fixed bed reactor filled with metallic packing, Chem. Eng. Sci. 122 (2015) 78–85, http://dx.doi.org/10.1016/j.ces.2014.09.019. [4] H.P. Veluswamy, J.Y. Chen, P. Linga, Surfactant effect on the kinetics of mixed hydrogen/propane hydrate formation for hydrogen storage as clathrates, Chem. Eng. Sci.nce 126 (2015) 488–499, http://dx.doi.org/10.1016/j. ces.2014.12.052. [5] H. Hashemi, S. Babaee, A.H. Mohammadi, P. Naidoo, D. Ramjugernath, Experimental study and modeling of the kinetics of refrigerant hydrate formation, J. Chem. Thermodynam. 82 (2015) 47–52, http://dx.doi.org/ 10.1016/j.jct.2014.10.017. [6] W. Kondo, K. Ohtsuka, R. Ohmura, S. Takeya, Y.H. Mori, Clathrate-hydrate formation from a hydrocarbon gas mixture: compositional evolution of formed hydrate during an isobaric semi-batch hydrate-forming operation, Appl. Energy 113 (2014) 864–871, http://dx.doi.org/10.1016/j. apenergy.2013.08.033. [7] P. Linga, N. Daraboina, J.A. Ripmeester, P. Englezos, Enhanced rate of gas hydrate formation in a fixed bed column filled with sand compared to a stirred vessel, Chem. Eng. Sci. 68 (1) (2012) 617–623, http://dx.doi.org/10.1016/j. ces.2011.10.030. [8] H. Ganji, M. Manteghian, K.S. zadeh, M. Omidkhah, H.R. Mofrad, Effect of different surfactants on methane hydrate formation rate, stability and storage capacity, Fuel 86 (3) (2007) 434–441, http://dx.doi.org/10.1016/ j.fuel.2006.07.032. [9] N. Ando, Y. Kuwabara, Y.H. Mori, Surfactant effects on hydrate formation in an unstirred gas/liquid system: An experimental study using methane and micelle-forming surfactants, Chem. Eng. Sci. 73 (2012) 79–85, http://dx.doi. org/10.1016/j.ces.2012.01.038. [10] S. Misyura, The influence of porosity and structural parameters on different kinds of gas hydrate dissociation, Sci. Rep. 6 (2016) 30324, http://dx.doi.org/ 10.1038/srep30324, 10 pages. [11] F. Rossi, M. Filipponi, B. Castellani, Investigation on a novel reactor for gas hydrate production, Appl. Energy 99 (2012) 167–172, http://dx.doi.org/ 10.1016/j.apenergy.2012.05.005. [12] B. Lucia, B. Castellani, F. Rossi, F. Cotana, E. Morini, A. Nicolini, M. Filipponi, Experimental investigations on scaled-up methane hydrate production with surfactant promotion: Energy considerations, J. Petroleum Sci. Eng. 120 (2014) 187–193, http://dx.doi.org/10.1016/j.petrol.2014.06.015. [13] M. Faizullin, A. Vinogradov, V. Koverda, Formation of clathrate hydrates under crystallization of gas-saturated amorphous ice, Int. J. Heat Mass Transfer 65 (2013) 649–654, http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.06.023.
A.A. Chernov et al. / International Journal of Heat and Mass Transfer 108 (2017) 1320–1323 [14] M.Z. Faizullin, A.V. Vinogradov, V.P. Koverda, Hydrate formation in layers of gas-saturated amorphous ice, Chem. Eng. Sci. 130 (2015) 135–143, http://dx. doi.org/10.1016/j.ces.2015.03.032. [15] V.S. Shagapov, M.K. Khasanov, I.K. Gimaltdinov, M.V. Stolpovsky, The features of gas hydrate dissociation in porous media at warm gas injection, Thermophys. Aeromech. 20 (3) (2013) 339–346, http://dx.doi.org/10.1134/ S0869864313030104. [16] V. Shagapov, N. Musakaev, M. Khasanov, Formation of gas hydrates in a porous medium during an injection of cold gas, Int. J. Heat Mass Transfer 84 (2015) 1030–1039, http://dx.doi.org/10.1016/j.ijheatmasstransfer.2015.01.105. [17] V. Nakoryakov, S. Misyura, The features of self-preservation for hydrate systems with methane, Chem. Eng. Sci. 104 (2013) 1–9, http://dx.doi.org/ 10.1016/j.ces.2013.08.049. [18] B. Castellani, F. Rossi, M. Filipponi, A. Nicolini, Hydrate-based removal of carbon dioxide and hydrogen sulphide from biogas mixtures: Experimental investigation and energy evaluations, Biomass Bioenergy 70 (2014) 330–338, http://dx.doi.org/10.1016/j.biombioe.2014.08.026.
1323
[19] V.E. Nakoryakov, V.E. Dontsov, A.A. Chernov, Gas hydrate formation in a gasliquid mixture behind a shock wave, Doklady Phys. 51 (11) (2006) 621–624, http://dx.doi.org/10.1134/S1028335806110127. [20] V.E. Dontsov, V.E. Nakoryakov, A.A. Chernov, Shock waves in water with freon12 bubbles and formation of gas hydrates, J. Appl. Mech. Tech. Phys. 48 (3) (2007) 346–360, http://dx.doi.org/10.1007/s10808-007-0044-5. [21] V. Dontsov, A. Chernov, Dilution and hydrate forming process in shock waves, Int. J. Heat Mass Transfer 52 (21–22) (2009) 4919–4928, http://dx.doi.org/ 10.1016/j.ijheatmasstransfer.2009.04.030. [22] V.E. Dontsov, A.A. Chernov, Dissolution and hydrate-formation processes behind the shock wave in a gas-liquid mixture, Doklady Phys. 54 (4) (2009) 215–219, http://dx.doi.org/10.1134/S1028335809040144. [23] A. Chernov, V. Dontsov, The processes of dissolution and hydrate forming behind the shock wave in the gasliquid medium with gas mixture bubbles, Int. J. Heat Mass Transfer 54 (19–20) (2011) 4307–4316, http://dx.doi.org/ 10.1016/j.ijheatmasstransfer.2011.05.014.
Contents lists available at ScienceDirect
International Journal of Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ijhmt
Technical Note
Hydrate formation in the cyclic process of refrigerant boilingcondensation in a water volume A.A. Chernov a,b,⇑, D.S. Elistratov a, I.V. Mezentsev a, A.V. Meleshkin a, A.A. Pil’nik a,b a b
Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia Novosibirsk State University, Novosibirsk 630090, Russia
a r t i c l e
i n f o
Article history: Received 5 August 2016 Received in revised form 24 November 2016 Accepted 5 December 2016 Available online 19 January 2017 Keywords: Hydrate formation Liquid-gas system Boiling Condensation
a b s t r a c t Conceptually new method of hydrate production is proposed. It is based on self-organization of the refrigerant boiling-condensation process in enclosed water volume. The key feature of the method is a high hydrate production rate combined with a comparatively low power consumption allowing us to expect the high effectiveness of the technologies based on it. The set of experiments was carried out. The gas hydrate of refrigerant R134a was produced. The criteria of intensification of the hydrate formation process are formulated. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction One fundamental problem of oil and gas industry is the formation and deposition of gas hydrates in the oil and gas fields and in the systems of underground and overground equipment. Thus, in the past the most of the studies were aimed at finding new methods of prevention the hydrate formation. But now the emphasis is shifted towards the perspective of using hydrates and the process of hydrate formation in practice [1,2]. For example, one economically sound method of gas transportation in the absence of gas pipeline involves conversion of gas into gas hydrate, transporting it in the solid state under static pressure and low temperatures. Such transportation method is the most profitable for small oil-gas fields and the collateral effect can be achieved by simultaneous realization of gas and clean water remained after gas-hydrate decomposition. Another use of hydrate technologies is the gas storage (in the gas-hydrate state) near large consumer. Man-caused hydrate formation processes can also be used outside the oil and gas industry for desalination of sea water, gases separation, fog elimination, heat accumulation, creation of efficient refrigeration cycles and others. Gas hydrate technologies can also help solve global ecological problems. One promising, for the large-scale use method of greenhouse gases utilization involves gas conversion into the gas ⇑ Corresponding author at: Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia. E-mail address: [email protected] (A.A. Chernov). http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.12.035 0017-9310/Ó 2016 Elsevier Ltd. All rights reserved.
hydrate state and storing it at the ocean bottom under low temperature and high pressure. Obviously, the main factor ensuring the financial viability of such technologies is the rate of hydrate formation. As a result, we set the objective to develop a fast and cost-effective method of hydrate production. The currently existing technologies of hydrate production are based on: intensive mixing of gassaturated water, fine dispersion of water jet in gas atmosphere, vibratory and supersonic influence on a bubble medium and so on. However, the majority of above-mentioned methods can be characterized by a low hydrate production rate and as a result low efficiency of plants based on them. A lot of works were devoted to the topic of gas hydrates. The most important of them are the studies of a gas-hydrate structure, its physicochemical, thermophysical, mechanical and other properties, the general conditions needed for their formation and their growth mechanisms [3–7]. Great attention is paid to the methods of studying both natural and man-made gas hydrates [8–12]. A large number of works are devoted to experimental and mathematical modeling of the processes of formation and decomposition of gas hydrates [13–18]. Comparatively recently a new hydrate formation method caused by the shock wave impact in a bubble medium [19–23] has been proposed. It allows the formation of different gas hydrates over a short period of time. In this work we propose conceptually new hydrate production method based on the self-organization of the cyclic boilingcondensation process.
A.A. Chernov et al. / International Journal of Heat and Mass Transfer 108 (2017) 1320–1323
2. Some information about gas hydrates Gas hydrate is a solid crystalline compound that forms under certain temperature and pressure conditions, from water (liquid water, ice or water vapor) and a low-molecular gas. Gas hydrates are categorized as the so-called clathrate compounds or compounds where gas molecules (”guest”) are trapped in the molecular cavities of the ice-like molecular structure (‘‘host”) formed by water molecules via hydrogen bonds. Gas molecules (‘‘guests”) is bonded with the structure (‘‘host”) only by Van der Waals forces without forming chemical bonds. The general formula of a gas hydrate is as follows MnH2 O, where M means the guest molecule; n—number of water molecules per one guest molecule. Number n is a variable and depends on the type of gas, pressure and temperature. One of unique properties of gas hydrates is the ability of trapping 70–300 gas volumes for one water volume. For example, 1 m3 of methane hydrate can carry 160 m3 of gas and the volume occupied by gas in a gas hydrate is less than 20%. The density of gas hydrate is typically less than the density of water and ice (for methane hydrate it is 900 kg/m3). After the increase in temperature and the decrease in pressure the hydrate decompose into gas and water absorbing great amount of heat in the process. 3. Experimental setup The experiments were done using the experimental setup (Fig. 1(a)) with the working section consisting of a parallelepiped pressure-tight chamber with the inside dimensions of 150 150 740 mm made of 15 mm thick stainless steel. The setup can withstand the pressure of up to 10 MPa. Two inspection windows (24 mm thick plexiglass) allow us to register hydrodynamic and thermophysic processes inside the chamber using high-speed photography. Detectors OWEN PD-100 and RT.50 VK1P were used to measure the pressure and temperature fields. The cooling was done through the side walls using the cooling jacket. Circulation thermostat LOIP FT-316-40 with working temperature range from 40 C to 100 C) and cooling liquid with crystallization temperature of 40 C were used. For the ambient temperature of 20 C the cooling rate was 770 W. Bottom part of
1321
the chamber was equipped with heater (up to 500 W). It was used to induce the intensive boiling of hydrating gas in the bottom part of the working section. The refrigerant R134a was used in the experiments as a hydrating gas. 4. Method description. Results The main principle of the proposed method is as follows. Working section is half filled with water. The water is cooled down to temperature 2–5 °C (temperature and pressure conditions are chosen so that hydrate formation is always possible the system). At the start of the process the gaseous refrigerant is supplied into the chamber. The refrigerant rapidly condenses at the cold walls of the chamber, streams down to the bottom of the unit and forms a liquid layer. At this stage the heater mounted into the bottom part of the working section turns on. The heating intensity is chosen so that the liquid refrigerant layer starts to actively boil. During their ascent to the colder area bubbles generated from the boiling rapidly become covered with hydrate shells. The shell has a friable and porous structure of overlapping flakes of gas hydrate. It appears that the gas always has a free access to the water at the interphase (hydrate shell offer no substantial diffusion resistance). It means that the hydrate mass growth rate in this process is not limited by diffusion (as we became used to) but is controlled by convective heat transfer at the interphase. Hydrate formation rate is high in such a process because the heat exchange processes are much faster than diffusion-driven processes. After arising to the free surface of the liquid and collapsing bubbles leave flakes of gas hydrate. As a result gas hydrate cap is growing above the liquid (Fig. 1(b)). The refrigerant remained from the formation of gas hydrate in the first cycle of the process condenses at the walls of working section in form of droplets, streams down to the bottom of the chamber and mixes with already boiling layer. Obviously, this process is a cyclic one and it continues until all refrigerant transforms into gas hydrate. Fig. 2(a) shows experimental dependencies of temperature and pressure in liquid near the heater and near the surface on time. It can be seen that in the course of the process the bottom layer temperature is higher than the equilibrium boiling point of refrigerant. But the upper layers of liquid stay cold. Change in refrigerant boil-
Fig. 1. (a) The scheme of experimental setup: 1—side wall with cooling jacket; 2—working section; 3—pressure gauge; 4—thermostat; 5—temperature detectors; 6—gas cylinder; 7—ADC & PC. (b) Gas hydrate produced during the experiment.
1322
A.A. Chernov et al. / International Journal of Heat and Mass Transfer 108 (2017) 1320–1323
Fig. 2. (a) Experimental dependences of liquid temperature T in the working section near the heater (diamonds) and near the free surface (circles) and pressure P on time t; thick solid line—the boiling curve. (b) The process in the P T Diagram; thick solid line – the boiling curve. The cyclic process of R134a boiling-condensation is schematically presented in the figure.
ing temperature is also illustrated in the figure. It is caused by the change in the pressure due to hydrate formation. Let us note that there is a good reason for temperature behaving in such a way. The process was controlled by the intensity of cooling at the walls of the working section and by the heating at the bottom of the chamber (the intensity of the former was higher than the intensity of the later as evidenced by the lowering of the temperature in the working section). It was done so that the hydrating gas participate in the aforementioned cycle at all times during the experiment. Such a cycle is shown in Fig. 2(b), clearly demonstrates the process at hand in the P T diagram. Let us not that the whole experiment during which the major portion of refrigerant turns into gas hydrate lasted around half an hour. It is significantly less than the time of hydrate formation in known industrial methods. The mass of gas hydrate produced in the experiments was 1–2 kg. Xray diffraction patterns confirm the presence of substantial fraction of hydrate in hydrate mass (which consists of gas hydrate and ice). We would like to bring your attention to the set of criteria implemented in this work that in our opinion led to the intensification of the process of gas hydrate formation. Briefly they can be listed as follows. Developed phase contact area was created. Obviously, this stimulates the process of gas hydrate formation (gas hydrate grows at the gas-water boundary). Gas hydrate formed on the phase contact area did not hinder the free access of the gas to the water (gas hydrate growth rate is limited by the heat transfer on the interphase and not by the diffusion process). Intensive (in our case convective) heat transfer was established because it determines the growth rate of gas hydrate mass. Finally, the conditions was created when the supercooling of the system relative to gas hydrate formation equilibrium curve is maximized (facilitates kinetics of gas hydrate formation and increases heat transfer).
5. Conclusions New hydrate production method is developed. It is based on self-organization of the boiling-condensation process in enclosed water volume. The method is defined by a good energy efficiency. It is shown that the intensification of hydrate formation process is caused by the forming of the developed interphase surface, the rapid cooling of the medium and the intensive mixing of liquid and gas phases. The gas hydrate of refrigerant R134a was produced. Diffraction patterns confirm the presence of substantial fraction of gas hydrate in the solid phase. The method developed
in this work can be used to create new cost-effective methods and technologies of producing gas hydrates. Acknowledgements This work was supported by the Russian Science Foundation (project # 15-19-10025). We express our gratitude to the Novosibirsk State University for giving us an access to the library. References [1] Y.F. Makogon, Hydrates of Hydrocarbons, PennWell books, 1997. [2] E. Sloan, C. Koh, Clathrate Hydrates of Natural Gases, third ed., Chemical Industries, CRC Press, 2007. [3] A. Kumar, T. Sakpal, P. Linga, R. Kumar, Enhanced carbon dioxide hydrate formation kinetics in a fixed bed reactor filled with metallic packing, Chem. Eng. Sci. 122 (2015) 78–85, http://dx.doi.org/10.1016/j.ces.2014.09.019. [4] H.P. Veluswamy, J.Y. Chen, P. Linga, Surfactant effect on the kinetics of mixed hydrogen/propane hydrate formation for hydrogen storage as clathrates, Chem. Eng. Sci.nce 126 (2015) 488–499, http://dx.doi.org/10.1016/j. ces.2014.12.052. [5] H. Hashemi, S. Babaee, A.H. Mohammadi, P. Naidoo, D. Ramjugernath, Experimental study and modeling of the kinetics of refrigerant hydrate formation, J. Chem. Thermodynam. 82 (2015) 47–52, http://dx.doi.org/ 10.1016/j.jct.2014.10.017. [6] W. Kondo, K. Ohtsuka, R. Ohmura, S. Takeya, Y.H. Mori, Clathrate-hydrate formation from a hydrocarbon gas mixture: compositional evolution of formed hydrate during an isobaric semi-batch hydrate-forming operation, Appl. Energy 113 (2014) 864–871, http://dx.doi.org/10.1016/j. apenergy.2013.08.033. [7] P. Linga, N. Daraboina, J.A. Ripmeester, P. Englezos, Enhanced rate of gas hydrate formation in a fixed bed column filled with sand compared to a stirred vessel, Chem. Eng. Sci. 68 (1) (2012) 617–623, http://dx.doi.org/10.1016/j. ces.2011.10.030. [8] H. Ganji, M. Manteghian, K.S. zadeh, M. Omidkhah, H.R. Mofrad, Effect of different surfactants on methane hydrate formation rate, stability and storage capacity, Fuel 86 (3) (2007) 434–441, http://dx.doi.org/10.1016/ j.fuel.2006.07.032. [9] N. Ando, Y. Kuwabara, Y.H. Mori, Surfactant effects on hydrate formation in an unstirred gas/liquid system: An experimental study using methane and micelle-forming surfactants, Chem. Eng. Sci. 73 (2012) 79–85, http://dx.doi. org/10.1016/j.ces.2012.01.038. [10] S. Misyura, The influence of porosity and structural parameters on different kinds of gas hydrate dissociation, Sci. Rep. 6 (2016) 30324, http://dx.doi.org/ 10.1038/srep30324, 10 pages. [11] F. Rossi, M. Filipponi, B. Castellani, Investigation on a novel reactor for gas hydrate production, Appl. Energy 99 (2012) 167–172, http://dx.doi.org/ 10.1016/j.apenergy.2012.05.005. [12] B. Lucia, B. Castellani, F. Rossi, F. Cotana, E. Morini, A. Nicolini, M. Filipponi, Experimental investigations on scaled-up methane hydrate production with surfactant promotion: Energy considerations, J. Petroleum Sci. Eng. 120 (2014) 187–193, http://dx.doi.org/10.1016/j.petrol.2014.06.015. [13] M. Faizullin, A. Vinogradov, V. Koverda, Formation of clathrate hydrates under crystallization of gas-saturated amorphous ice, Int. J. Heat Mass Transfer 65 (2013) 649–654, http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.06.023.
A.A. Chernov et al. / International Journal of Heat and Mass Transfer 108 (2017) 1320–1323 [14] M.Z. Faizullin, A.V. Vinogradov, V.P. Koverda, Hydrate formation in layers of gas-saturated amorphous ice, Chem. Eng. Sci. 130 (2015) 135–143, http://dx. doi.org/10.1016/j.ces.2015.03.032. [15] V.S. Shagapov, M.K. Khasanov, I.K. Gimaltdinov, M.V. Stolpovsky, The features of gas hydrate dissociation in porous media at warm gas injection, Thermophys. Aeromech. 20 (3) (2013) 339–346, http://dx.doi.org/10.1134/ S0869864313030104. [16] V. Shagapov, N. Musakaev, M. Khasanov, Formation of gas hydrates in a porous medium during an injection of cold gas, Int. J. Heat Mass Transfer 84 (2015) 1030–1039, http://dx.doi.org/10.1016/j.ijheatmasstransfer.2015.01.105. [17] V. Nakoryakov, S. Misyura, The features of self-preservation for hydrate systems with methane, Chem. Eng. Sci. 104 (2013) 1–9, http://dx.doi.org/ 10.1016/j.ces.2013.08.049. [18] B. Castellani, F. Rossi, M. Filipponi, A. Nicolini, Hydrate-based removal of carbon dioxide and hydrogen sulphide from biogas mixtures: Experimental investigation and energy evaluations, Biomass Bioenergy 70 (2014) 330–338, http://dx.doi.org/10.1016/j.biombioe.2014.08.026.
1323
[19] V.E. Nakoryakov, V.E. Dontsov, A.A. Chernov, Gas hydrate formation in a gasliquid mixture behind a shock wave, Doklady Phys. 51 (11) (2006) 621–624, http://dx.doi.org/10.1134/S1028335806110127. [20] V.E. Dontsov, V.E. Nakoryakov, A.A. Chernov, Shock waves in water with freon12 bubbles and formation of gas hydrates, J. Appl. Mech. Tech. Phys. 48 (3) (2007) 346–360, http://dx.doi.org/10.1007/s10808-007-0044-5. [21] V. Dontsov, A. Chernov, Dilution and hydrate forming process in shock waves, Int. J. Heat Mass Transfer 52 (21–22) (2009) 4919–4928, http://dx.doi.org/ 10.1016/j.ijheatmasstransfer.2009.04.030. [22] V.E. Dontsov, A.A. Chernov, Dissolution and hydrate-formation processes behind the shock wave in a gas-liquid mixture, Doklady Phys. 54 (4) (2009) 215–219, http://dx.doi.org/10.1134/S1028335809040144. [23] A. Chernov, V. Dontsov, The processes of dissolution and hydrate forming behind the shock wave in the gasliquid medium with gas mixture bubbles, Int. J. Heat Mass Transfer 54 (19–20) (2011) 4307–4316, http://dx.doi.org/ 10.1016/j.ijheatmasstransfer.2011.05.014.