| Coal is closely related to people’s lives,and the proportion of coal consumption has risen sharply in recent years.The mine ventilation system is an indispensable link in the construction and production process of coal mines.The mine return air generated by this ventilation system is uninterrupted throughout the year and the air volume is huge.The return air temperature of most mines is maintained above 15℃.In recent years,the state has actively encouraged multi-energy complementary and comprehensive cascade utilization of terminal energy.How to use the heat of mine return air has always been a hot research topic for scholars engaged in the field of coal energy and environmental protection.Among them,spray heat exchange heat recovery-heat pump heating technology is It is one of the main ways to utilize the waste heat of the mine return air.The main research work on this heat transfer method is as follows:Firstly,7 different technical routes of mine return air waste heat utilization are analyzed and researched,and it is found that the use of mine return air waste heat for heating has the lowest energy consumption.Among them,spray heat exchange technology has a wide range of applications,high heat exchange efficiency,and energy saving.It is about 75%of the heat supplied by traditional electric boilers;the direct steam heat exchange technology is only suitable for small mines with little heat load;the heat pipe heat exchange technology has the lowest relative energy consumption,and is suitable for a pair of air inlet and return air shafts Mines without large building heating loads.Secondly,according to the available potential,the waste heat resources of the mine return air are divided into four grades.Among them,the first-level waste heat resources should be used first.Direct heat exchange and other technologies are used to obtain heat;secondary waste heat resources should be utilized as much as possible,and technologies such as direct steam heat exchange,partition heat exchange,and high-efficiency air inlet-return air direct heat exchange should be used to obtain heat;third-stage waste heat resources can be Depending on the situation,it is appropriate to use technologies such as direct steam heat exchange and partition heat exchange to obtain heat;the fourth-level waste heat resources should not be used.Through analysis and calculation,it is shown that the energy saving potential of mine return air waste heat utilization is huge,the energy saving after utilization of unit air volume is 3.5～5.8 times of the conventional energy consumption per unit demand.The colder the region,the greater the potential for energy savings.Thirdly,the internal droplet motion and heat transfer characteristics of the spray heat exchange device were studied,and the actual spray heat exchanger was designed and numerical simulation studied.The water droplets in the spray heat exchanger are subject to the combined effect of viscous resistance and differential pressure resistance,and the spray water droplets will quickly reach the finishing speed at a certain initial speed and then move at a uniform speed.When the rest of the conditions remain unchanged,as the particle size increases,the resistance becomes an upward trend,and the combined force and acceleration form a downward trend.The heat transfer efficiency under the same water-to-gas ratio increases with the increase of air flow rate,and the heat exchange efficiency increases with the increase of the relative movement speed of water droplets at the same spray particle size.The results show that when the basic size of the spray heat exchanger is fixed,the correlation between the heat exchange efficiency and the air flow rate and the water-to-air ratio is greater,and the particle size of the spray water droplets has been timed,the impact of the water droplet flow rate on the heat transfer efficiency is small,and the water-to-air ratio is about 1,which has a higher heat exchange efficiency.The calculation expression of the sprinkler heat exchange efficiency is given,and the study shows that the lower the return air temperature after the heat exchange,the higher the heat exchange effect.During the heat exchange process of the mine return air spray heat exchanger,a large amount of water vapor in the return air will be precipitated,and the lower the spray water temperature,the greater the amount of water precipitated.Then,the paper proposes a new calculation and selection method for the main/backup heat source of the sprinkler heat exchange system,that is,the average value between the extreme minimum temperature average and the heating temperature is used to calculate the heat main heat source load for vertical/inclined well antifreeze,the heating temperature is used to calculate the heat main heat source load for antifreeze of the flat/special intake well,and the difference between the extreme load specified in the specification and the calculated main heat source load is the heat backup heat source load for the wellbore freeze protection,and the selection of the main heat source is carried out on this basis.Through this method,not only can the system configuration be more reasonable,the operating energy consumption is reduced,and the reliability of the system can be improved.For the spray heat exchange system,the water ring type cold and heat combined supply process design scheme is proposed,and through the optimized design calculation selection method and process flow,the load of the main heat source equipment of the system can be reduced by more than 10%,and the overall energy efficiency of the system can be improved by 15%.Finally,combined with the actual operation of the return air waste heat utilization project of Kou zi dong Mine,the calculation selection method and process flow design scheme of the spray heat exchange system proposed in this study were verified,and the actual operation results showed that the energy efficiency of the two bath hot water units was increased by 37%compared with the first mode of operation alone,the COP was increased by 60%compared with the original mode,the energy efficiency of the cooler EER was increased by 0.9,and the energy efficiency was increased by 15%.This fully proves the practicality and reliability of the proposed solution of this paper,and the energy-saving effect is remarkable. |
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