| The exploitation and utilization of coalbed gas is an important factor to improve the utilization rate of coal resources and solve the gas disaster and gas pollution.As a clean and efficient energy,gas has a great impact on the rapid growth of energy demand.With the development of gas development and utilization technology,microwave has been put forward in the field of gas development and utilization,such as coal seam penetration and gas desorption.In order to study the effect of microwave on coal pore structure and the influence of gas adsorption capacity and mechanism,find the inner mechanism of them,this paper selects different kinds of coal as the research object,and analyzes the characteristic of microwave devices and the applicability of equipment about specific surface area measurement.Then,the five coal samples are treated aforehand with different microwave power and time of microwave equipment and specific surface area of coal sample are measured by equipment of specific surface area measurement.Finally,low pressure nitrogen adsorptionexperiments were carried out in simple adsorption the platform to build their own.Through the comparative analysis of experimental data,we find out the relationship between the change of specific surface area and the adsorption characteristics of coal samples,and comprehensively discuss the mechanism of the effect of microwave on pore structure and adsorption capacity of coal.(1)For the microwave equipment used in the experiment,power and time are the main factors affecting temperature variation of coal in microwave equipment.At the same time,the higher the microwave power,the faster the heating of coal;under the same power condition,the temperature change of the coal sample with time is divided into "three stage" of rapid heating,slow heating,stable,but the dividing temperature range or microwave power have a great relationship.(2)The specific surface area measuring instrument used in the experiment is based on the principle of dynamic method,and the measurement range is limited.Through repeated tests,it is found that the equipment has a certain requirement for the particle size of the experimental coal.For low rank coal,accuracy of measurement is better when particle size of coal is less than 60 mesh;for high rank coal,accuracy of measurement is better when particle size of coal is less than 160 mesh.(3)By measuring specific surface area of different coal samples in different factors of microwave power,reaction time,water content,it is found that the change of specific surface area of coal is different and the changing rules ofdifferent coal are not the same.With the increase of the microwave power and time,the specific surface area change rate of high rank coal is large,low rank coal surface area change rate shows a downward trend.The change regulation has a great relationship with different coal rank components and its structure.(4)A simple low-pressure nitrogen adsorption device was used to measure the adsorption capacity of treated coal samples for nitrogen.It was found that the influence of microwave on the adsorption capacity of coal samples would be quite different from coal samples.The experimental results show that the high rank with the power increased by the adsorption capacity increased slightly,while the low rank coal will obviously decrease;does not assume the regularity change of coal adsorption capacity with the increase of all the time,but generally will increase.(5)There is a certain synergy between the change of the specific surface of coal samples and the change of adsorption capacity under the effect of microwave.The influence of microwave on the structure and adsorption capacity of coal can be attributed to the low temperature spillover of water,volatile matter,high temperature pyrolysis of organic matter and thermal collapse of coal matrix. |
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