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Design and characteristic analysis of vibration feeding system for coal-gas dust-removal medium

Design and characteristic analysis of vibration feeding system for coal-gas dust-removal medium Abstract A vibration feeder is a piece of equipment for rationing and conveying powder, particle and block materials. In order to test the regeneration performance of de-dusting medium for high-temperature coal gas, a set of de-dusting medium-feeding systems was designed quantitatively. The de-dusting medium-feeding system is used in the gasification process for cleaning coal gas. The system is mainly composed of a hopper unit, control unit and feeding unit. In order to optimize the feeding stability of the coal-gas dust-removal medium vibration feeding system, the setting and scope of the following design factors and operating factors are investigated. Specifically, it includes the influence of gate-valve-opening adjustment of the control unit on the feeding stability of a vibrating feeding system; the influence of the gap size of the dipleg of the control unit on the feeding sensitivity of the vibration system; the influence of the particle size of the de-dusting medium on the operating range of the vibrating feeding system; the influence of the digitization of the working-current indicator of electromagnetic vibrating feeders on measurement variation and the process variation of a vibration feeding system. This vibration feeding system can realize the function of precise and quantitative feeding of the de-dusting medium, which can meet the design requirements of subsequent experimental research. Graphical Abstract Open in new tabDownload slide vibrating feed system, coal-gas dust-removal medium, feeding stability, feeding sensitivity, measurement variation, process variation, gasification Introduction A vibration feeder is a piece of equipment used for the quantitative supply and transportation of powder, particles and bulk materials. According to the process development of its working principle, the feeding mode can be divided into reciprocating feeding, electromagnetic vibration feeding, motor vibration feeding and mechanical vibration feeding [1]. The structures of vibration feeders can be mainly divided into two types: the linear reciprocating method and the spiral twisting method [2]. The vibration feeder can not only continuously and uniformly ration feeding [3], but also has the advantages of a simple structure, stable operation and high energy efficiency. Therefore, vibration feeders are widely used in the screening process of coal-preparation plants [4] and the quantitative batching processes of the rubber industry, fertilizer industry [5], food processing, light industry, metallurgical manufacturing industries [6, 7], the weighing and automatic packaging processes of commodities [8, 9] and bulk powder or particle material transport or transfer processes [10, 11]. In order to test the regeneration performance of a high-temperature coal-gas dust-removal medium, a set of quantitative feeding systems was designed to precisely control the amount of coal-gas dust-removal medium [12, 13]. The vibration feeding system is used to supply the coal-gas dust-removal medium accurately for the next regeneration of equipment for a fresh coal-gas dust-removal medium, which is coupled in the process of coal gasification for clean coal gas. We established a new method to recycle the coal-gas dust-removal medium and verified its validation. The design and characteristics of the vibration feeding system can satisfy technological requirements. In view of the advantages of the vibration feeder mentioned above and the design experience [2, 14–18] and theory of the previous research [19–24], a hanging linear reciprocating type of vibration feeder was introduced as the key technical component to control the quantitative feeding of coal-gas dust-removal medium. In this study, the structure design of the coal-gas dust-removal medium-feeding system is optimized and metering the control function of the vibration feeder is modified to improve the feeding precision of the coal-gas dust-removal medium, so that the output of the coal-gas dust-removal medium can be supplied stably and accurately. 1 Material and apparatus The coal-gas dust-removal medium used in this study is metal-oxide ceramic balls with particle sizes of 3 and 6 mm, and the heap density is ~1.25 kg·m–3. The vibration feeding system of the coal-gas dust-removal medium is mainly composed of three units: holding, controlling and feeding. Its structure and size are shown in Fig. 1a. The holding unit of the coal-gas dust-removal medium is a conical vessel with a volume of ~1.2 m3 and a maximum capacity of ~1.5 tons of coal-gas dust-removal medium. The controlling unit consists of a manual DN200 square gate valve and a square sleeve with adjustable height forming different gap sizes of the discharge port, as shown in Fig. 1b. The gate-valve opening can be adjusted from 0% to 100%, which can directly cut off and restore the supply of de-dusting medium. The height adjustment of the feeding leg sleeve can control the distance between the feeding-tube bottom and the chute plane of the vibration feeder. The feeding unit is a suspended electromagnetic vibration feeder and the actual equipment is shown in Fig. 1c. Fig. 1: Open in new tabDownload slide Structure diagram of a vibration feeding system of de-dusting medium The electromagnetic actuator of the vibration feeder is driven by the XK-II silicon-controlled rectifier (SCR) power supply. The input of the power supply is 220 V/50 Hz AC and the output RMS value of the voltage is 0–90 V DC. The adjustable range of the working-condition current indicator is 0–5 A. The instruments employed in the test are five containers for particulate materials, one electronic balance for measuring the mass of particulate materials and one stopwatch for testing duration. 2 Results and analysis In order to optimize the stability of the vibration feed system of coal-gas dust-removal medium, the following design factors and operating factors were investigated: the influence of the gate-valve-opening adjustment of the control unit on the stability of the feed quantity of the vibration feeding system; the influence of the gap-size adjustment of the discharging port on the feeding sensitivity of the vibration system; the influence of the particle size of the coal-gas dust-removal medium on the operating range of the feed quantity of the vibration feeding system; the influence of the digital modification of the working-condition current indicator of the electromagnetic vibration feeder on the measurement variation and process variation of the vibration feeding system. 2.1 Influence of the gate-valve opening on the stability of the de-dusting-medium feeding To test the influence of the gate-valve opening on the coal-gas dust-removal medium-feeding stability of the vibration feeding system, the gate-valve opening was set to 100%, 50%, 35% and 20%, respectively, at the operation condition of the electromagnetic vibration-feeder current of 1.0 A for 6-mm coal-gas dust-removal medium. The duration of each working condition was 2 min and the test results are shown in Fig. 2. Fig. 2: Open in new tabDownload slide Variation of de-dusting medium feeding under different gate-valve openings in the vibration feeding system It can be seen from the test results in Fig. 2 that, as the gate-valve opening increases, the coal-gas dust-removal medium-feeding quantity decreases. Spline interpolation was performed on the average value of the coal-gas dust-removal medium flow rate, μF, under the four opening degrees of the gate valve, and the influence curve of continuous changes in the gate-valve opening on the mean value of the coal-gas dust-removal medium flow rate is obtained, as shown in Fig. 3. Fig. 3: Open in new tabDownload slide Influence of the opening of the gate valve on the stability of de-dusting medium feeding in the vibration feeding system It can be analysed from the structure of the vibration feeding system for coal-gas dust-removal medium shown in Fig. 1 that the opening of the gate valve controls the volume flow rate of the falling coal-gas dust-removal medium. In principle, the greater the opening degree of the gate valve, the greater the feeding quantity of the coal-gas dust-removal medium will be, as shown in Fig. 3, in which the coal-gas dust-removal medium-feeding quantity varies with the opening degree of the gate valve from 0% to ~20%. However, with further opening of the degree increment of the gate valve from ~20% to 100%, the gravity of more coal-gas dust-removal medium in the silo directly acts on the chute plane of the vibration feeder under the feeding leg through the force chain of particulate matter. Due to the influence of the weight of the coal-gas dust-removal medium, the amplitude of the vibration feeder is limited and it cannot provide more feeding capacity at the same vibration frequency. Therefore, when the opening of the gate valve increases from ~20% to 100%, as shown in Fig. 3, the feeding volume of the coal-gas dust-removal medium vibration feeding system does not increase further, but slowly decreases. Similarly, the standard deviation of the coal-gas dust-removal medium-feeding quantity σF under four gate-valve openings is processed by spline interpolation and the influence curve of continuous changes in gate-valve openings on the standard deviation of the coal-gas dust-removal medium-feeding quantity is obtained, as shown in Fig. 3. In order to measure the stability of the coal-gas dust-removal medium-feed quantity, the ratio of the standard deviation of the feeding quantity to the mean of the feeding quantity σF/μF is defined as the stability of the feeding quantity. As illustrated in Fig. 3, when the gate-valve opening decreases from 100% to ~30%, the σF/μF value of the coal-gas dust-removal medium feed decreases—that is, the stability increases. However, when the gate-valve opening is further reduced from ~30%, the σF/μF value of the de-dusting medium feeding increases—that is, the stability is slightly worse. It is not difficult to understand that the larger the opening degree of the gate valve, the closer the feeding process of the coal-gas dust-removal medium is to the flow process of a continuous medium. At this point, the coal-gas dust-removal medium-feeding volume is relatively impacted by the material level in the hopper. Therefore, the standard deviation of the coal-gas dust-removal medium is larger and the stability of the coal-gas dust-removal medium is poor when the gate valve has a larger opening. On the contrary, when the valve opening is lower, the coal-gas dust-removal medium flow through the gap of the gate valve is more reflected as a discrete medium. The random fluctuation of the flow rate of the discrete medium, namely the standard deviation of the feed quantity, will be amplified by the relatively small feed quantity, which reflects the relatively poor stability. Through the influence of adjusting the gate-valve-opening degree on the stability of the feeding quantity of the de-dusting medium vibration feeding system, the preliminary determination is that a gate-valve-opening degree of 30% is more appropriate. 2.2 The influence of the gap adjustment of the discharge port on the sensitivity of the de-dusting medium-feeding amount In order to test the sensitivity of the gap adjustment of the discharging port on the volume flow rate of the de-dusting medium, the feed volume of the de-dusting medium of 6 mm under the different working current of the electromagnetic vibration feeder was analysed when the gap sizes of the discharge port were set as 3.6 and 1.0 cm, respectively. The gate-valve opening was ~30% and the duration of each working condition was 2 min. The test results are shown in Fig. 4. Fig. 4: Open in new tabDownload slide Influence of the gap of the discharge port in the vibration feeding system on the feeding range of de-dusting medium As illustrated in Fig. 4, the gap size of the discharging port in the vibration feeding system has a great influence on the feeding range and sensitivity of the coal-gas dust-removal medium. When the gap size of the feeding port decreases from 3.6 to 1.0 cm, the feeding range is reduced and the control sensitivity decreases from 3000 to 1500 kg·h–1·A–1, so the feeding volume becomes easy to control. With a decrease in the gap of the discharge port, the flow of the de-dusting medium changes from a continuous medium to a discrete medium, and the stability of the feed decreases slightly. The maximum operating current of the electromagnetic vibration feeder used in this study is 2.0 A. It is expected that the whole vibration feeding system can be controllable and adjustable in the range of 600–1200 kg·h–1. Therefore, the gap size of the discharging port is set as 1.0 cm to meet the requirements of subsequent tests. For the same size of a 6-mm diameter of coal-gas dust-removal medium materials, the curves of the flow rate as a function of the current demonstrate two shapes, depending on the different conditions of the gap size of the dipleg. It can be concluded from the experimental results that the flow rates of coal-gas dust-removal medium increase sharply during the process of improving the working current of the vibrator for two gap sizes of the dipleg. It is clear that the flow rate of the de-dusting-medium materials cannot be controlled easily during the sharp-increase section. However, a gap size of 1.0 cm is much better than that of 3.6 cm, because the flow rate is more controllable for the 1.0-cm gap size. The curve shape appears to be exponential. For the gap size of 3.6 cm, the sharp-increase section is incomplete from 0 to 1600 kg·h–1. In fact, the curve shape of the 3.6-cm gap size is also exponential with the current, although a flow rate of >1600 kg·h–1 is meaningless for this experiment. 2.3 Influence of the particle size of the de-dusting medium on the operating range of the feed quantity The coal-gas de-dusting medium is ceramic metal-oxide particulate matter with uniform particle size, the fluidity of which in the same conveying equipment is different. For the preparation of follow-up studies and experiments, the feeding quantity of the second type of coal-gas dust-removal medium with a particle size of 3 mm on the vibration feeding system was tested and the influence of the particle size of the coal-gas dust-removal medium on the operating range of the feeding quantity of the vibration feeding system was obtained, as shown in Fig. 5. Fig. 5: Open in new tabDownload slide Influence of the particle size of the de-dusting medium on the operating range of the feeding quantity of the vibration feeding system In combination with Figs 4 and 5, it can be seen that the coal-gas dust-removal medium-feeding amount of the vibration feeding system does not always increase linearly with an increase in the working current, which can be roughly divided into the starting stage, the conveying stage and the limit stage. During the vibration-initiation stage, the electromagnetic vibration feeder cannot normally initiate vibration due to the back-loading effect of the coal-gas dust-removal medium in the silo on the chute plane, and the conveying quantity of the coal-gas dust-removal medium is almost zero. When the working-condition current goes above the starting stage, the conveying amount of the de-dusting medium of the vibration feeding system approximately increases linearly with the working-condition current. Good vibration-feeding-system design should make the conveying stage as widely distributed as possible on the operating conditions, such as the operating current. The limit stage represents the design limit of the whole set of the vibration feeding system. The coal-gas dust-removal medium-feeding quantity no longer increases further with an increase in the working-condition current—that is, the conveying-quantity limit designed for the vibration feeding system should be higher than the maximum conveying quantity of the de-dusting medium required by the test. It can also be seen from Fig. 5 that, for the same set of vibration feeding systems, the limit feeding amount of the de-dusting medium with a small particle size is higher than that with a large particle size. It can be seen that the fluidity of the de-dusting medium with a small particle size is better than that with a large particle size and is closer to that of a continuous medium. 2.4 Measurement variation and process variation of a vibration feeding system The core of the vibration feeding system is the electromagnetic vibration feeder. During the regeneration process, it is directly driven by its power-supply equipment—an SCR power-supply module, so as to directly control the de-dusting medium-feeding amount. As a finished product with good packaging, with the SCR power supply applied to the actual test process, it is inevitable to have design defects, so the cost of the test measurement brings difficulties for precision assurance. As the XK-II SCR power supply was used in this study, the maximum working-condition current and current-indicator range are seriously mismatched, and the mechanical-pointer current-indicator reading is not accurate enough, resulting in the loss of precision control of the coal-gas dust-removal medium feed. For this reason, the current display of the SCR power supply is digitally modified to improve the control accuracy of the coal-gas dust-removal medium feeding, and the test results before and after the modification are analysed by measuring tools. The comparison results are shown in Fig. 6. Fig. 6: Open in new tabDownload slide Influence of the digital modification of the SCR current indicator on the measurement variation and process variation of the vibration feeding system of de-dusting medium It can be seen from Fig. 6 that digital transformation of the current indicator of the SCR power supply of the electromagnetic vibration feeder improves the measurement accuracy significantly, and both the repetitive value (EV) and the reproducibility value (AV) have been decreased according to the analysis results. It shows that the error of the measurement system is improved obviously. In this study, the influence of the design factor and the operation factor of the vibration feeding system on the coal-gas dust-removal medium-feeding amount is evaluated based on the test results of the digital modification of the SCR power-supply current indicator. 3 Conclusions This paper focuses on the design of the vibration feeding system for coal-gas dust-removal medium. The influence of the design factors and operation factors of the vibration feeding system on the precise control of the coal-gas dust-removal medium feeding was investigated. The opening degree of the gate valve in the vibration feeding system can not only affect the quantity of the coal-gas dust-removal medium, but also affects the stability of the coal-gas dust-removal medium feeding. When the opening degree is greater, the quantity of material stored in the silo has a remarkable effect on the stability of the coal-gas dust-removal medium feeding. When the gate valve is approximately closed, the particle properties and characteristics of the coal-gas dust-removal medium flow pattern are more obvious, which makes the random fluctuation in the case of a low feed volume more obvious and the stability of the feed volume is damaged. It can be concluded from the experiments of this research that the gate valve is optimized at ~30% open. The gap adjustment of the discharge port in the vibration-feeder system affects the sensitivity of the working current of the vibration feeder to the amount of coal-gas dust-removal medium. A larger gap in the feeding port makes the working current of the vibrating feeder control the feeding quantity of the de-dusting medium in an uneasy way and the feeding quantity easily changed. The gap size of the discharge port should be designed to meet the adjustment range of the coal-gas dust-removal medium-feeding quantity evenly distributed in the adjustable range of the working current of the electromagnetic vibration feeder. Generally, it should not exceed twice the particle size. The particle size of the de-dusting medium affects the working-current-regulation range of the electromagnetic vibration feeder. The larger the particle size, the wider the adjustable range of the operating current; the smaller the particle size, the narrower the adjustable range of the operating current. The experiments show that the 6- and 3-mm coal-gas dust-removal medium particles used in this study meet the requirements of the adjustable feeding range for subsequent experimental studies. The digital reconstruction of the working-condition current indicator of the electromagnetic vibration feeder can obviously reduce the measurement variation and process variation of the whole set of vibration feeding systems, and improve the repeatability and reproducibility of the whole set of vibration feeding systems for coal-gas dust-removal medium. In summary, the vibration feeding system can realize the function of precise and quantitative feeding for coal-gas dust-removal medium, which can meet the design requirements of subsequent experimental research. Conflict of Interest None declared. References [1] Yin Z , Zhang L, Tian H. Study and development of vibratory feeder . Metallurgical Equipment, 2010 , 5 : 49 – 54 . Google Scholar OpenURL Placeholder Text WorldCat [2] Wang Y , Zhou H. 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For commercial re-use, please contact journals.permissions@oup.com © The Author(s) 2020. Published by Oxford University Press on behalf of National Institute of Clean-and-Low-Carbon Energy http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Clean Energy Oxford University Press

Design and characteristic analysis of vibration feeding system for coal-gas dust-removal medium

Clean Energy , Volume 4 (4) – Dec 31, 2020

Design and characteristic analysis of vibration feeding system for coal-gas dust-removal medium

Clean Energy , Volume 4 (4) – Dec 31, 2020

Abstract

Abstract A vibration feeder is a piece of equipment for rationing and conveying powder, particle and block materials. In order to test the regeneration performance of de-dusting medium for high-temperature coal gas, a set of de-dusting medium-feeding systems was designed quantitatively. The de-dusting medium-feeding system is used in the gasification process for cleaning coal gas. The system is mainly composed of a hopper unit, control unit and feeding unit. In order to optimize the feeding stability of the coal-gas dust-removal medium vibration feeding system, the setting and scope of the following design factors and operating factors are investigated. Specifically, it includes the influence of gate-valve-opening adjustment of the control unit on the feeding stability of a vibrating feeding system; the influence of the gap size of the dipleg of the control unit on the feeding sensitivity of the vibration system; the influence of the particle size of the de-dusting medium on the operating range of the vibrating feeding system; the influence of the digitization of the working-current indicator of electromagnetic vibrating feeders on measurement variation and the process variation of a vibration feeding system. This vibration feeding system can realize the function of precise and quantitative feeding of the de-dusting medium, which can meet the design requirements of subsequent experimental research. Graphical Abstract Open in new tabDownload slide vibrating feed system, coal-gas dust-removal medium, feeding stability, feeding sensitivity, measurement variation, process variation, gasification Introduction A vibration feeder is a piece of equipment used for the quantitative supply and transportation of powder, particles and bulk materials. According to the process development of its working principle, the feeding mode can be divided into reciprocating feeding, electromagnetic vibration feeding, motor vibration feeding and mechanical vibration feeding [1]. The structures of vibration feeders can be mainly divided into two types: the linear reciprocating method and the spiral twisting method [2]. The vibration feeder can not only continuously and uniformly ration feeding [3], but also has the advantages of a simple structure, stable operation and high energy efficiency. Therefore, vibration feeders are widely used in the screening process of coal-preparation plants [4] and the quantitative batching processes of the rubber industry, fertilizer industry [5], food processing, light industry, metallurgical manufacturing industries [6, 7], the weighing and automatic packaging processes of commodities [8, 9] and bulk powder or particle material transport or transfer processes [10, 11]. In order to test the regeneration performance of a high-temperature coal-gas dust-removal medium, a set of quantitative feeding systems was designed to precisely control the amount of coal-gas dust-removal medium [12, 13]. The vibration feeding system is used to supply the coal-gas dust-removal medium accurately for the next regeneration of equipment for a fresh coal-gas dust-removal medium, which is coupled in the process of coal gasification for clean coal gas. We established a new method to recycle the coal-gas dust-removal medium and verified its validation. The design and characteristics of the vibration feeding system can satisfy technological requirements. In view of the advantages of the vibration feeder mentioned above and the design experience [2, 14–18] and theory of the previous research [19–24], a hanging linear reciprocating type of vibration feeder was introduced as the key technical component to control the quantitative feeding of coal-gas dust-removal medium. In this study, the structure design of the coal-gas dust-removal medium-feeding system is optimized and metering the control function of the vibration feeder is modified to improve the feeding precision of the coal-gas dust-removal medium, so that the output of the coal-gas dust-removal medium can be supplied stably and accurately. 1 Material and apparatus The coal-gas dust-removal medium used in this study is metal-oxide ceramic balls with particle sizes of 3 and 6 mm, and the heap density is ~1.25 kg·m–3. The vibration feeding system of the coal-gas dust-removal medium is mainly composed of three units: holding, controlling and feeding. Its structure and size are shown in Fig. 1a. The holding unit of the coal-gas dust-removal medium is a conical vessel with a volume of ~1.2 m3 and a maximum capacity of ~1.5 tons of coal-gas dust-removal medium. The controlling unit consists of a manual DN200 square gate valve and a square sleeve with adjustable height forming different gap sizes of the discharge port, as shown in Fig. 1b. The gate-valve opening can be adjusted from 0% to 100%, which can directly cut off and restore the supply of de-dusting medium. The height adjustment of the feeding leg sleeve can control the distance between the feeding-tube bottom and the chute plane of the vibration feeder. The feeding unit is a suspended electromagnetic vibration feeder and the actual equipment is shown in Fig. 1c. Fig. 1: Open in new tabDownload slide Structure diagram of a vibration feeding system of de-dusting medium The electromagnetic actuator of the vibration feeder is driven by the XK-II silicon-controlled rectifier (SCR) power supply. The input of the power supply is 220 V/50 Hz AC and the output RMS value of the voltage is 0–90 V DC. The adjustable range of the working-condition current indicator is 0–5 A. The instruments employed in the test are five containers for particulate materials, one electronic balance for measuring the mass of particulate materials and one stopwatch for testing duration. 2 Results and analysis In order to optimize the stability of the vibration feed system of coal-gas dust-removal medium, the following design factors and operating factors were investigated: the influence of the gate-valve-opening adjustment of the control unit on the stability of the feed quantity of the vibration feeding system; the influence of the gap-size adjustment of the discharging port on the feeding sensitivity of the vibration system; the influence of the particle size of the coal-gas dust-removal medium on the operating range of the feed quantity of the vibration feeding system; the influence of the digital modification of the working-condition current indicator of the electromagnetic vibration feeder on the measurement variation and process variation of the vibration feeding system. 2.1 Influence of the gate-valve opening on the stability of the de-dusting-medium feeding To test the influence of the gate-valve opening on the coal-gas dust-removal medium-feeding stability of the vibration feeding system, the gate-valve opening was set to 100%, 50%, 35% and 20%, respectively, at the operation condition of the electromagnetic vibration-feeder current of 1.0 A for 6-mm coal-gas dust-removal medium. The duration of each working condition was 2 min and the test results are shown in Fig. 2. Fig. 2: Open in new tabDownload slide Variation of de-dusting medium feeding under different gate-valve openings in the vibration feeding system It can be seen from the test results in Fig. 2 that, as the gate-valve opening increases, the coal-gas dust-removal medium-feeding quantity decreases. Spline interpolation was performed on the average value of the coal-gas dust-removal medium flow rate, μF, under the four opening degrees of the gate valve, and the influence curve of continuous changes in the gate-valve opening on the mean value of the coal-gas dust-removal medium flow rate is obtained, as shown in Fig. 3. Fig. 3: Open in new tabDownload slide Influence of the opening of the gate valve on the stability of de-dusting medium feeding in the vibration feeding system It can be analysed from the structure of the vibration feeding system for coal-gas dust-removal medium shown in Fig. 1 that the opening of the gate valve controls the volume flow rate of the falling coal-gas dust-removal medium. In principle, the greater the opening degree of the gate valve, the greater the feeding quantity of the coal-gas dust-removal medium will be, as shown in Fig. 3, in which the coal-gas dust-removal medium-feeding quantity varies with the opening degree of the gate valve from 0% to ~20%. However, with further opening of the degree increment of the gate valve from ~20% to 100%, the gravity of more coal-gas dust-removal medium in the silo directly acts on the chute plane of the vibration feeder under the feeding leg through the force chain of particulate matter. Due to the influence of the weight of the coal-gas dust-removal medium, the amplitude of the vibration feeder is limited and it cannot provide more feeding capacity at the same vibration frequency. Therefore, when the opening of the gate valve increases from ~20% to 100%, as shown in Fig. 3, the feeding volume of the coal-gas dust-removal medium vibration feeding system does not increase further, but slowly decreases. Similarly, the standard deviation of the coal-gas dust-removal medium-feeding quantity σF under four gate-valve openings is processed by spline interpolation and the influence curve of continuous changes in gate-valve openings on the standard deviation of the coal-gas dust-removal medium-feeding quantity is obtained, as shown in Fig. 3. In order to measure the stability of the coal-gas dust-removal medium-feed quantity, the ratio of the standard deviation of the feeding quantity to the mean of the feeding quantity σF/μF is defined as the stability of the feeding quantity. As illustrated in Fig. 3, when the gate-valve opening decreases from 100% to ~30%, the σF/μF value of the coal-gas dust-removal medium feed decreases—that is, the stability increases. However, when the gate-valve opening is further reduced from ~30%, the σF/μF value of the de-dusting medium feeding increases—that is, the stability is slightly worse. It is not difficult to understand that the larger the opening degree of the gate valve, the closer the feeding process of the coal-gas dust-removal medium is to the flow process of a continuous medium. At this point, the coal-gas dust-removal medium-feeding volume is relatively impacted by the material level in the hopper. Therefore, the standard deviation of the coal-gas dust-removal medium is larger and the stability of the coal-gas dust-removal medium is poor when the gate valve has a larger opening. On the contrary, when the valve opening is lower, the coal-gas dust-removal medium flow through the gap of the gate valve is more reflected as a discrete medium. The random fluctuation of the flow rate of the discrete medium, namely the standard deviation of the feed quantity, will be amplified by the relatively small feed quantity, which reflects the relatively poor stability. Through the influence of adjusting the gate-valve-opening degree on the stability of the feeding quantity of the de-dusting medium vibration feeding system, the preliminary determination is that a gate-valve-opening degree of 30% is more appropriate. 2.2 The influence of the gap adjustment of the discharge port on the sensitivity of the de-dusting medium-feeding amount In order to test the sensitivity of the gap adjustment of the discharging port on the volume flow rate of the de-dusting medium, the feed volume of the de-dusting medium of 6 mm under the different working current of the electromagnetic vibration feeder was analysed when the gap sizes of the discharge port were set as 3.6 and 1.0 cm, respectively. The gate-valve opening was ~30% and the duration of each working condition was 2 min. The test results are shown in Fig. 4. Fig. 4: Open in new tabDownload slide Influence of the gap of the discharge port in the vibration feeding system on the feeding range of de-dusting medium As illustrated in Fig. 4, the gap size of the discharging port in the vibration feeding system has a great influence on the feeding range and sensitivity of the coal-gas dust-removal medium. When the gap size of the feeding port decreases from 3.6 to 1.0 cm, the feeding range is reduced and the control sensitivity decreases from 3000 to 1500 kg·h–1·A–1, so the feeding volume becomes easy to control. With a decrease in the gap of the discharge port, the flow of the de-dusting medium changes from a continuous medium to a discrete medium, and the stability of the feed decreases slightly. The maximum operating current of the electromagnetic vibration feeder used in this study is 2.0 A. It is expected that the whole vibration feeding system can be controllable and adjustable in the range of 600–1200 kg·h–1. Therefore, the gap size of the discharging port is set as 1.0 cm to meet the requirements of subsequent tests. For the same size of a 6-mm diameter of coal-gas dust-removal medium materials, the curves of the flow rate as a function of the current demonstrate two shapes, depending on the different conditions of the gap size of the dipleg. It can be concluded from the experimental results that the flow rates of coal-gas dust-removal medium increase sharply during the process of improving the working current of the vibrator for two gap sizes of the dipleg. It is clear that the flow rate of the de-dusting-medium materials cannot be controlled easily during the sharp-increase section. However, a gap size of 1.0 cm is much better than that of 3.6 cm, because the flow rate is more controllable for the 1.0-cm gap size. The curve shape appears to be exponential. For the gap size of 3.6 cm, the sharp-increase section is incomplete from 0 to 1600 kg·h–1. In fact, the curve shape of the 3.6-cm gap size is also exponential with the current, although a flow rate of >1600 kg·h–1 is meaningless for this experiment. 2.3 Influence of the particle size of the de-dusting medium on the operating range of the feed quantity The coal-gas de-dusting medium is ceramic metal-oxide particulate matter with uniform particle size, the fluidity of which in the same conveying equipment is different. For the preparation of follow-up studies and experiments, the feeding quantity of the second type of coal-gas dust-removal medium with a particle size of 3 mm on the vibration feeding system was tested and the influence of the particle size of the coal-gas dust-removal medium on the operating range of the feeding quantity of the vibration feeding system was obtained, as shown in Fig. 5. Fig. 5: Open in new tabDownload slide Influence of the particle size of the de-dusting medium on the operating range of the feeding quantity of the vibration feeding system In combination with Figs 4 and 5, it can be seen that the coal-gas dust-removal medium-feeding amount of the vibration feeding system does not always increase linearly with an increase in the working current, which can be roughly divided into the starting stage, the conveying stage and the limit stage. During the vibration-initiation stage, the electromagnetic vibration feeder cannot normally initiate vibration due to the back-loading effect of the coal-gas dust-removal medium in the silo on the chute plane, and the conveying quantity of the coal-gas dust-removal medium is almost zero. When the working-condition current goes above the starting stage, the conveying amount of the de-dusting medium of the vibration feeding system approximately increases linearly with the working-condition current. Good vibration-feeding-system design should make the conveying stage as widely distributed as possible on the operating conditions, such as the operating current. The limit stage represents the design limit of the whole set of the vibration feeding system. The coal-gas dust-removal medium-feeding quantity no longer increases further with an increase in the working-condition current—that is, the conveying-quantity limit designed for the vibration feeding system should be higher than the maximum conveying quantity of the de-dusting medium required by the test. It can also be seen from Fig. 5 that, for the same set of vibration feeding systems, the limit feeding amount of the de-dusting medium with a small particle size is higher than that with a large particle size. It can be seen that the fluidity of the de-dusting medium with a small particle size is better than that with a large particle size and is closer to that of a continuous medium. 2.4 Measurement variation and process variation of a vibration feeding system The core of the vibration feeding system is the electromagnetic vibration feeder. During the regeneration process, it is directly driven by its power-supply equipment—an SCR power-supply module, so as to directly control the de-dusting medium-feeding amount. As a finished product with good packaging, with the SCR power supply applied to the actual test process, it is inevitable to have design defects, so the cost of the test measurement brings difficulties for precision assurance. As the XK-II SCR power supply was used in this study, the maximum working-condition current and current-indicator range are seriously mismatched, and the mechanical-pointer current-indicator reading is not accurate enough, resulting in the loss of precision control of the coal-gas dust-removal medium feed. For this reason, the current display of the SCR power supply is digitally modified to improve the control accuracy of the coal-gas dust-removal medium feeding, and the test results before and after the modification are analysed by measuring tools. The comparison results are shown in Fig. 6. Fig. 6: Open in new tabDownload slide Influence of the digital modification of the SCR current indicator on the measurement variation and process variation of the vibration feeding system of de-dusting medium It can be seen from Fig. 6 that digital transformation of the current indicator of the SCR power supply of the electromagnetic vibration feeder improves the measurement accuracy significantly, and both the repetitive value (EV) and the reproducibility value (AV) have been decreased according to the analysis results. It shows that the error of the measurement system is improved obviously. In this study, the influence of the design factor and the operation factor of the vibration feeding system on the coal-gas dust-removal medium-feeding amount is evaluated based on the test results of the digital modification of the SCR power-supply current indicator. 3 Conclusions This paper focuses on the design of the vibration feeding system for coal-gas dust-removal medium. The influence of the design factors and operation factors of the vibration feeding system on the precise control of the coal-gas dust-removal medium feeding was investigated. The opening degree of the gate valve in the vibration feeding system can not only affect the quantity of the coal-gas dust-removal medium, but also affects the stability of the coal-gas dust-removal medium feeding. When the opening degree is greater, the quantity of material stored in the silo has a remarkable effect on the stability of the coal-gas dust-removal medium feeding. When the gate valve is approximately closed, the particle properties and characteristics of the coal-gas dust-removal medium flow pattern are more obvious, which makes the random fluctuation in the case of a low feed volume more obvious and the stability of the feed volume is damaged. It can be concluded from the experiments of this research that the gate valve is optimized at ~30% open. The gap adjustment of the discharge port in the vibration-feeder system affects the sensitivity of the working current of the vibration feeder to the amount of coal-gas dust-removal medium. A larger gap in the feeding port makes the working current of the vibrating feeder control the feeding quantity of the de-dusting medium in an uneasy way and the feeding quantity easily changed. The gap size of the discharge port should be designed to meet the adjustment range of the coal-gas dust-removal medium-feeding quantity evenly distributed in the adjustable range of the working current of the electromagnetic vibration feeder. Generally, it should not exceed twice the particle size. The particle size of the de-dusting medium affects the working-current-regulation range of the electromagnetic vibration feeder. The larger the particle size, the wider the adjustable range of the operating current; the smaller the particle size, the narrower the adjustable range of the operating current. The experiments show that the 6- and 3-mm coal-gas dust-removal medium particles used in this study meet the requirements of the adjustable feeding range for subsequent experimental studies. The digital reconstruction of the working-condition current indicator of the electromagnetic vibration feeder can obviously reduce the measurement variation and process variation of the whole set of vibration feeding systems, and improve the repeatability and reproducibility of the whole set of vibration feeding systems for coal-gas dust-removal medium. In summary, the vibration feeding system can realize the function of precise and quantitative feeding for coal-gas dust-removal medium, which can meet the design requirements of subsequent experimental research. Conflict of Interest None declared. References [1] Yin Z , Zhang L, Tian H. Study and development of vibratory feeder . Metallurgical Equipment, 2010 , 5 : 49 – 54 . Google Scholar OpenURL Placeholder Text WorldCat [2] Wang Y , Zhou H. 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Vibration conveying—analysis and design: a review . Mech Mach Theory, 1979 , 14 : 89 – 97 . Google Scholar Crossref Search ADS WorldCat [13] Yeong M , De Vries W. A methodology for part feeder design . CIRP Annals, 1994 , 43 : 19 – 22 . Google Scholar Crossref Search ADS WorldCat [14] Lu J . Research on the design of electromagnetic vibration quantitative feeding system . Manufacture Engineering Design, 2019 , 5 : 83 – 84 + 87 . Google Scholar OpenURL Placeholder Text WorldCat [15] You S . Overview of vibration feeder design . Science Information, 2007 , 5 : 64 . Google Scholar OpenURL Placeholder Text WorldCat [16] Yue W , Su Y, Shao W. Combined application of vibrating feeder and valve in bulk material system . Modern Mining, 2012 , 27 : 140 – 142 . Google Scholar OpenURL Placeholder Text WorldCat [17] Yang Z , Liu Y, Mu Z. Development of adjustable outlet of vibrating feeder . Mining Processing Equipment, 2007 , 8 : 82 – 84 . Google Scholar OpenURL Placeholder Text WorldCat [18] Ma X , Wang L, Zhu D. Structural improvement of electromagnetic vibration feeder frame . Mining Processing Equipment, 2013 , 41 : 139 – 140 . Google Scholar OpenURL Placeholder Text WorldCat [19] Bhattachar SN , Hedden DB, Olsofsky AM, et al. Evaluation of the vibratory feeder method for assessment of powder flow properties . Int J Pharm, 2004 , 269 : 385 – 392 . Google Scholar Crossref Search ADS WorldCat [20] Buzzoni M , Battarra M, Mucchi E, et al. Motion analysis of a linear vibration feeder: dynamic modeling and experimental verification . Mech Mach Theory, 2017 , 114 : 98 – 110 . Google Scholar Crossref Search ADS WorldCat [21] Chandravanshi M , Mukhopadhyay A. Dynamic analysis of vibration feeder and their effect on feed particle speed on conveying surface . Measurement, 2017 , 101 : 145 – 156 . Google Scholar Crossref Search ADS WorldCat [22] Despotović Ž , Urukalo D, Lei M, et al. Mathematical modeling of resonant linear vibration conveyor with electromagnetic excitation: simulations and experimental results . Appl Math Model, 2017 , 41 : 1 – 24 . Google Scholar Crossref Search ADS WorldCat [23] Lim G . On the conveying velocity of a vibration feeder . Computers Structures, 1997 , 62 : 197 – 203 . Google Scholar Crossref Search ADS WorldCat [24] Pahor-Filho E , Pereira M, De Stéfani M. A vibrating feeder tray improves bullfrog production . Aquacult Eng, 2015 , 68 : 6 – 9 . Google Scholar Crossref Search ADS WorldCat © The Author(s) 2020. Published by Oxford University Press on behalf of National Institute of Clean-and-Low-Carbon Energy This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com © The Author(s) 2020. Published by Oxford University Press on behalf of National Institute of Clean-and-Low-Carbon Energy

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Copyright © 2022 National Institute of Clean-and-Low-Carbon Energy
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Abstract

Abstract A vibration feeder is a piece of equipment for rationing and conveying powder, particle and block materials. In order to test the regeneration performance of de-dusting medium for high-temperature coal gas, a set of de-dusting medium-feeding systems was designed quantitatively. The de-dusting medium-feeding system is used in the gasification process for cleaning coal gas. The system is mainly composed of a hopper unit, control unit and feeding unit. In order to optimize the feeding stability of the coal-gas dust-removal medium vibration feeding system, the setting and scope of the following design factors and operating factors are investigated. Specifically, it includes the influence of gate-valve-opening adjustment of the control unit on the feeding stability of a vibrating feeding system; the influence of the gap size of the dipleg of the control unit on the feeding sensitivity of the vibration system; the influence of the particle size of the de-dusting medium on the operating range of the vibrating feeding system; the influence of the digitization of the working-current indicator of electromagnetic vibrating feeders on measurement variation and the process variation of a vibration feeding system. This vibration feeding system can realize the function of precise and quantitative feeding of the de-dusting medium, which can meet the design requirements of subsequent experimental research. Graphical Abstract Open in new tabDownload slide vibrating feed system, coal-gas dust-removal medium, feeding stability, feeding sensitivity, measurement variation, process variation, gasification Introduction A vibration feeder is a piece of equipment used for the quantitative supply and transportation of powder, particles and bulk materials. According to the process development of its working principle, the feeding mode can be divided into reciprocating feeding, electromagnetic vibration feeding, motor vibration feeding and mechanical vibration feeding [1]. The structures of vibration feeders can be mainly divided into two types: the linear reciprocating method and the spiral twisting method [2]. The vibration feeder can not only continuously and uniformly ration feeding [3], but also has the advantages of a simple structure, stable operation and high energy efficiency. Therefore, vibration feeders are widely used in the screening process of coal-preparation plants [4] and the quantitative batching processes of the rubber industry, fertilizer industry [5], food processing, light industry, metallurgical manufacturing industries [6, 7], the weighing and automatic packaging processes of commodities [8, 9] and bulk powder or particle material transport or transfer processes [10, 11]. In order to test the regeneration performance of a high-temperature coal-gas dust-removal medium, a set of quantitative feeding systems was designed to precisely control the amount of coal-gas dust-removal medium [12, 13]. The vibration feeding system is used to supply the coal-gas dust-removal medium accurately for the next regeneration of equipment for a fresh coal-gas dust-removal medium, which is coupled in the process of coal gasification for clean coal gas. We established a new method to recycle the coal-gas dust-removal medium and verified its validation. The design and characteristics of the vibration feeding system can satisfy technological requirements. In view of the advantages of the vibration feeder mentioned above and the design experience [2, 14–18] and theory of the previous research [19–24], a hanging linear reciprocating type of vibration feeder was introduced as the key technical component to control the quantitative feeding of coal-gas dust-removal medium. In this study, the structure design of the coal-gas dust-removal medium-feeding system is optimized and metering the control function of the vibration feeder is modified to improve the feeding precision of the coal-gas dust-removal medium, so that the output of the coal-gas dust-removal medium can be supplied stably and accurately. 1 Material and apparatus The coal-gas dust-removal medium used in this study is metal-oxide ceramic balls with particle sizes of 3 and 6 mm, and the heap density is ~1.25 kg·m–3. The vibration feeding system of the coal-gas dust-removal medium is mainly composed of three units: holding, controlling and feeding. Its structure and size are shown in Fig. 1a. The holding unit of the coal-gas dust-removal medium is a conical vessel with a volume of ~1.2 m3 and a maximum capacity of ~1.5 tons of coal-gas dust-removal medium. The controlling unit consists of a manual DN200 square gate valve and a square sleeve with adjustable height forming different gap sizes of the discharge port, as shown in Fig. 1b. The gate-valve opening can be adjusted from 0% to 100%, which can directly cut off and restore the supply of de-dusting medium. The height adjustment of the feeding leg sleeve can control the distance between the feeding-tube bottom and the chute plane of the vibration feeder. The feeding unit is a suspended electromagnetic vibration feeder and the actual equipment is shown in Fig. 1c. Fig. 1: Open in new tabDownload slide Structure diagram of a vibration feeding system of de-dusting medium The electromagnetic actuator of the vibration feeder is driven by the XK-II silicon-controlled rectifier (SCR) power supply. The input of the power supply is 220 V/50 Hz AC and the output RMS value of the voltage is 0–90 V DC. The adjustable range of the working-condition current indicator is 0–5 A. The instruments employed in the test are five containers for particulate materials, one electronic balance for measuring the mass of particulate materials and one stopwatch for testing duration. 2 Results and analysis In order to optimize the stability of the vibration feed system of coal-gas dust-removal medium, the following design factors and operating factors were investigated: the influence of the gate-valve-opening adjustment of the control unit on the stability of the feed quantity of the vibration feeding system; the influence of the gap-size adjustment of the discharging port on the feeding sensitivity of the vibration system; the influence of the particle size of the coal-gas dust-removal medium on the operating range of the feed quantity of the vibration feeding system; the influence of the digital modification of the working-condition current indicator of the electromagnetic vibration feeder on the measurement variation and process variation of the vibration feeding system. 2.1 Influence of the gate-valve opening on the stability of the de-dusting-medium feeding To test the influence of the gate-valve opening on the coal-gas dust-removal medium-feeding stability of the vibration feeding system, the gate-valve opening was set to 100%, 50%, 35% and 20%, respectively, at the operation condition of the electromagnetic vibration-feeder current of 1.0 A for 6-mm coal-gas dust-removal medium. The duration of each working condition was 2 min and the test results are shown in Fig. 2. Fig. 2: Open in new tabDownload slide Variation of de-dusting medium feeding under different gate-valve openings in the vibration feeding system It can be seen from the test results in Fig. 2 that, as the gate-valve opening increases, the coal-gas dust-removal medium-feeding quantity decreases. Spline interpolation was performed on the average value of the coal-gas dust-removal medium flow rate, μF, under the four opening degrees of the gate valve, and the influence curve of continuous changes in the gate-valve opening on the mean value of the coal-gas dust-removal medium flow rate is obtained, as shown in Fig. 3. Fig. 3: Open in new tabDownload slide Influence of the opening of the gate valve on the stability of de-dusting medium feeding in the vibration feeding system It can be analysed from the structure of the vibration feeding system for coal-gas dust-removal medium shown in Fig. 1 that the opening of the gate valve controls the volume flow rate of the falling coal-gas dust-removal medium. In principle, the greater the opening degree of the gate valve, the greater the feeding quantity of the coal-gas dust-removal medium will be, as shown in Fig. 3, in which the coal-gas dust-removal medium-feeding quantity varies with the opening degree of the gate valve from 0% to ~20%. However, with further opening of the degree increment of the gate valve from ~20% to 100%, the gravity of more coal-gas dust-removal medium in the silo directly acts on the chute plane of the vibration feeder under the feeding leg through the force chain of particulate matter. Due to the influence of the weight of the coal-gas dust-removal medium, the amplitude of the vibration feeder is limited and it cannot provide more feeding capacity at the same vibration frequency. Therefore, when the opening of the gate valve increases from ~20% to 100%, as shown in Fig. 3, the feeding volume of the coal-gas dust-removal medium vibration feeding system does not increase further, but slowly decreases. Similarly, the standard deviation of the coal-gas dust-removal medium-feeding quantity σF under four gate-valve openings is processed by spline interpolation and the influence curve of continuous changes in gate-valve openings on the standard deviation of the coal-gas dust-removal medium-feeding quantity is obtained, as shown in Fig. 3. In order to measure the stability of the coal-gas dust-removal medium-feed quantity, the ratio of the standard deviation of the feeding quantity to the mean of the feeding quantity σF/μF is defined as the stability of the feeding quantity. As illustrated in Fig. 3, when the gate-valve opening decreases from 100% to ~30%, the σF/μF value of the coal-gas dust-removal medium feed decreases—that is, the stability increases. However, when the gate-valve opening is further reduced from ~30%, the σF/μF value of the de-dusting medium feeding increases—that is, the stability is slightly worse. It is not difficult to understand that the larger the opening degree of the gate valve, the closer the feeding process of the coal-gas dust-removal medium is to the flow process of a continuous medium. At this point, the coal-gas dust-removal medium-feeding volume is relatively impacted by the material level in the hopper. Therefore, the standard deviation of the coal-gas dust-removal medium is larger and the stability of the coal-gas dust-removal medium is poor when the gate valve has a larger opening. On the contrary, when the valve opening is lower, the coal-gas dust-removal medium flow through the gap of the gate valve is more reflected as a discrete medium. The random fluctuation of the flow rate of the discrete medium, namely the standard deviation of the feed quantity, will be amplified by the relatively small feed quantity, which reflects the relatively poor stability. Through the influence of adjusting the gate-valve-opening degree on the stability of the feeding quantity of the de-dusting medium vibration feeding system, the preliminary determination is that a gate-valve-opening degree of 30% is more appropriate. 2.2 The influence of the gap adjustment of the discharge port on the sensitivity of the de-dusting medium-feeding amount In order to test the sensitivity of the gap adjustment of the discharging port on the volume flow rate of the de-dusting medium, the feed volume of the de-dusting medium of 6 mm under the different working current of the electromagnetic vibration feeder was analysed when the gap sizes of the discharge port were set as 3.6 and 1.0 cm, respectively. The gate-valve opening was ~30% and the duration of each working condition was 2 min. The test results are shown in Fig. 4. Fig. 4: Open in new tabDownload slide Influence of the gap of the discharge port in the vibration feeding system on the feeding range of de-dusting medium As illustrated in Fig. 4, the gap size of the discharging port in the vibration feeding system has a great influence on the feeding range and sensitivity of the coal-gas dust-removal medium. When the gap size of the feeding port decreases from 3.6 to 1.0 cm, the feeding range is reduced and the control sensitivity decreases from 3000 to 1500 kg·h–1·A–1, so the feeding volume becomes easy to control. With a decrease in the gap of the discharge port, the flow of the de-dusting medium changes from a continuous medium to a discrete medium, and the stability of the feed decreases slightly. The maximum operating current of the electromagnetic vibration feeder used in this study is 2.0 A. It is expected that the whole vibration feeding system can be controllable and adjustable in the range of 600–1200 kg·h–1. Therefore, the gap size of the discharging port is set as 1.0 cm to meet the requirements of subsequent tests. For the same size of a 6-mm diameter of coal-gas dust-removal medium materials, the curves of the flow rate as a function of the current demonstrate two shapes, depending on the different conditions of the gap size of the dipleg. It can be concluded from the experimental results that the flow rates of coal-gas dust-removal medium increase sharply during the process of improving the working current of the vibrator for two gap sizes of the dipleg. It is clear that the flow rate of the de-dusting-medium materials cannot be controlled easily during the sharp-increase section. However, a gap size of 1.0 cm is much better than that of 3.6 cm, because the flow rate is more controllable for the 1.0-cm gap size. The curve shape appears to be exponential. For the gap size of 3.6 cm, the sharp-increase section is incomplete from 0 to 1600 kg·h–1. In fact, the curve shape of the 3.6-cm gap size is also exponential with the current, although a flow rate of >1600 kg·h–1 is meaningless for this experiment. 2.3 Influence of the particle size of the de-dusting medium on the operating range of the feed quantity The coal-gas de-dusting medium is ceramic metal-oxide particulate matter with uniform particle size, the fluidity of which in the same conveying equipment is different. For the preparation of follow-up studies and experiments, the feeding quantity of the second type of coal-gas dust-removal medium with a particle size of 3 mm on the vibration feeding system was tested and the influence of the particle size of the coal-gas dust-removal medium on the operating range of the feeding quantity of the vibration feeding system was obtained, as shown in Fig. 5. Fig. 5: Open in new tabDownload slide Influence of the particle size of the de-dusting medium on the operating range of the feeding quantity of the vibration feeding system In combination with Figs 4 and 5, it can be seen that the coal-gas dust-removal medium-feeding amount of the vibration feeding system does not always increase linearly with an increase in the working current, which can be roughly divided into the starting stage, the conveying stage and the limit stage. During the vibration-initiation stage, the electromagnetic vibration feeder cannot normally initiate vibration due to the back-loading effect of the coal-gas dust-removal medium in the silo on the chute plane, and the conveying quantity of the coal-gas dust-removal medium is almost zero. When the working-condition current goes above the starting stage, the conveying amount of the de-dusting medium of the vibration feeding system approximately increases linearly with the working-condition current. Good vibration-feeding-system design should make the conveying stage as widely distributed as possible on the operating conditions, such as the operating current. The limit stage represents the design limit of the whole set of the vibration feeding system. The coal-gas dust-removal medium-feeding quantity no longer increases further with an increase in the working-condition current—that is, the conveying-quantity limit designed for the vibration feeding system should be higher than the maximum conveying quantity of the de-dusting medium required by the test. It can also be seen from Fig. 5 that, for the same set of vibration feeding systems, the limit feeding amount of the de-dusting medium with a small particle size is higher than that with a large particle size. It can be seen that the fluidity of the de-dusting medium with a small particle size is better than that with a large particle size and is closer to that of a continuous medium. 2.4 Measurement variation and process variation of a vibration feeding system The core of the vibration feeding system is the electromagnetic vibration feeder. During the regeneration process, it is directly driven by its power-supply equipment—an SCR power-supply module, so as to directly control the de-dusting medium-feeding amount. As a finished product with good packaging, with the SCR power supply applied to the actual test process, it is inevitable to have design defects, so the cost of the test measurement brings difficulties for precision assurance. As the XK-II SCR power supply was used in this study, the maximum working-condition current and current-indicator range are seriously mismatched, and the mechanical-pointer current-indicator reading is not accurate enough, resulting in the loss of precision control of the coal-gas dust-removal medium feed. For this reason, the current display of the SCR power supply is digitally modified to improve the control accuracy of the coal-gas dust-removal medium feeding, and the test results before and after the modification are analysed by measuring tools. The comparison results are shown in Fig. 6. Fig. 6: Open in new tabDownload slide Influence of the digital modification of the SCR current indicator on the measurement variation and process variation of the vibration feeding system of de-dusting medium It can be seen from Fig. 6 that digital transformation of the current indicator of the SCR power supply of the electromagnetic vibration feeder improves the measurement accuracy significantly, and both the repetitive value (EV) and the reproducibility value (AV) have been decreased according to the analysis results. It shows that the error of the measurement system is improved obviously. In this study, the influence of the design factor and the operation factor of the vibration feeding system on the coal-gas dust-removal medium-feeding amount is evaluated based on the test results of the digital modification of the SCR power-supply current indicator. 3 Conclusions This paper focuses on the design of the vibration feeding system for coal-gas dust-removal medium. The influence of the design factors and operation factors of the vibration feeding system on the precise control of the coal-gas dust-removal medium feeding was investigated. The opening degree of the gate valve in the vibration feeding system can not only affect the quantity of the coal-gas dust-removal medium, but also affects the stability of the coal-gas dust-removal medium feeding. When the opening degree is greater, the quantity of material stored in the silo has a remarkable effect on the stability of the coal-gas dust-removal medium feeding. When the gate valve is approximately closed, the particle properties and characteristics of the coal-gas dust-removal medium flow pattern are more obvious, which makes the random fluctuation in the case of a low feed volume more obvious and the stability of the feed volume is damaged. It can be concluded from the experiments of this research that the gate valve is optimized at ~30% open. The gap adjustment of the discharge port in the vibration-feeder system affects the sensitivity of the working current of the vibration feeder to the amount of coal-gas dust-removal medium. A larger gap in the feeding port makes the working current of the vibrating feeder control the feeding quantity of the de-dusting medium in an uneasy way and the feeding quantity easily changed. The gap size of the discharge port should be designed to meet the adjustment range of the coal-gas dust-removal medium-feeding quantity evenly distributed in the adjustable range of the working current of the electromagnetic vibration feeder. Generally, it should not exceed twice the particle size. The particle size of the de-dusting medium affects the working-current-regulation range of the electromagnetic vibration feeder. The larger the particle size, the wider the adjustable range of the operating current; the smaller the particle size, the narrower the adjustable range of the operating current. The experiments show that the 6- and 3-mm coal-gas dust-removal medium particles used in this study meet the requirements of the adjustable feeding range for subsequent experimental studies. The digital reconstruction of the working-condition current indicator of the electromagnetic vibration feeder can obviously reduce the measurement variation and process variation of the whole set of vibration feeding systems, and improve the repeatability and reproducibility of the whole set of vibration feeding systems for coal-gas dust-removal medium. In summary, the vibration feeding system can realize the function of precise and quantitative feeding for coal-gas dust-removal medium, which can meet the design requirements of subsequent experimental research. Conflict of Interest None declared. References [1] Yin Z , Zhang L, Tian H. Study and development of vibratory feeder . Metallurgical Equipment, 2010 , 5 : 49 – 54 . Google Scholar OpenURL Placeholder Text WorldCat [2] Wang Y , Zhou H. 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For commercial re-use, please contact journals.permissions@oup.com © The Author(s) 2020. Published by Oxford University Press on behalf of National Institute of Clean-and-Low-Carbon Energy

Journal

Clean EnergyOxford University Press

Published: Dec 31, 2020

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