| Natural gas is widely used in the industrial and civil applications on account of its safety,cleanliness and high calorific value.Natural gas directly extracted from gas wells,usually contains saturated water vapor.Water vapor in natural gas can cause multiple hazards to the transport and application of natural gas.When temperature decreases or pressure increases during the pipeline transportation,the saturated water vapor and smaller molecular hydrocarbons may form hydrates in the natural gas.This may lead to the reduction of pipeline transportation capacity or blockage of pipeline and valve.Water vapor may react with other acid gases such as H2S and CO2 in natural gas,which can form corrosive acids harmful to pipelines and equipment.When natural gas is used as a synthetic raw material,water vapor may lead to side reactions or inactivation and poisoning of the catalyst during the synthesis.Therefore,in order to ensure the smooth operation of the natural gas transmission system or to meet the requirements of downstream industrial production,natural gas dehydration is indispensable.At present,natural gas dehydration process via triethylene glycol(TEG)solution as an absorbent is most widely used dehydration method in the industry.This method achieves circulation of TEG solution by absorption and regeneration unit to attain continuous production.The tower(plate tower and packed tower)is a mass transfer equipment,which commonly used in the TEG dehydration process.But there are some significant problems to resolve such as low mass transfer efficiency,large equipment volume and high investment in the tower.Rotating packed bed(RPB)is a typical technology for strengthening chemical process,and has the characteristics of improving mass transfer significantly.Natural gas dehydration process can be strengthened by high gravity technology,which can be expected to improve dehydration efficiency and reduce equipment volume and investment cost.In this paper,study on the dehydration process of natural gas in the rotating packed bed was carried out.The effects of different operation conditions such as rotation speed,gas flow rate,liquid flow rate,operation pressure,purity of TEG solution,water content in the inlet gas phase on Kya and HTU were explored.At the same time,an experimental study on the regeneration process of TEG by rotating packed bed was carried out.The effects of different operation conditions on the regeneration performance of TEG and the mass transfer characteristics of the regeneration process were explored.The specific conclusions are as follows:(1)Absorption unit:The appropriate operation condition of rotation speed is 1000 rpm in the absorption unit.The contrast results between low pressure and normal pressure show that when system operation pressure is 0.3 MPa and 0.6 MPa,Kya increases by 51.08%and 96.02%respectively,and HTU reduces by 33.81%and 48.98%respectively.Under the same operation conditions,increasing the mass transfer coefficient can reduce equipment investment and improve the processing capacity of the system.Through theoretical analysis,the influence of operation pressure on mass transfer is consistent with experimental results.The absorption line is farther from the equilibrium line,and the water content in the outlet gas can continue to decrease,which can increase the dewatering depth of natural gas.(2)Regeneration unit:The rotation speed is 600 rpm,the residence time in the reboiler is 5 min,the liquid temperature is 463 K,and the stripping gas flow rate is 450 L/h,which are the optimal conditions for the entire regeneration process.When the gas-liquid ratio is 85,the rotation speed is 600 rpm,the residence time in the reboiler is 5 min,the liquid temperature is 463 K,and the purity of rich TEG is 96%,mass fraction of lean TEG can reach up to 99.98%during the experiment,which can obtain the dew point depression of 60??75? in the absorption unit of natural gas dehydration.The Aspen HYSYS V9 simulation results show that the operation conditions and regeneration performance are the same both traditional packed bed and RPB.The packing height of RPB is only 2.38 cm,and the packing volume of RPB is only 71.68 cm3.While the height of the traditional packed tower is 64 cm,the volume of the packing is 803.84 cm3.The packing volume in RPB is one-eleventh of that in packed tower.According to the above experimental results,the application of RPB in natural gas dehydration process will have vital guidance for enhancing gas-liquid mass transfer,reducing equipment volume and investment cost. |
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