Research On Flue Gas Waste Heat Recovery Of Gas Turbine In Offshore Oilfield Based On Heat Pipe Technology

Gas turbine is the main energy consumption equipment of offshore oil platforms.It emits a large amount of high temperature flue gas and has great potential for waste heat recovery,but the space and load of the platforms are limited.Heat pipe has excellent heat transfer performance,light weight,and small volume.Steel-water heat pipes were produced in this paper,the boiling process of water outside the condensation section is visualized and experimentally studied.At the same time,the model of gas turbine and waste heat recovery is established by Aspen Plus software to carry out simulation research.According to the actual situation,the waste heat recovery device of heat pipe steam generator is designed and applied in engineering practice.In this paper,steel-water heat pipes with different scales are made,and visualization experiments are carried out to study the heat transfer performance of heat pipes under different working conditions.The results show that during the start-up process,with the accumulation of energy,the bubbles on the outer wall of the condensation section are generated on the heating surface and become larger with the continuous heat transfer,then fall off and rise from the wall.Fusion and splitting occur during the rise process,which strengthens the disturbance of the liquid and water boils gradually.The boiling continues for a short time after stopping heating.Then bubbles gradually become smaller with the decrease of temperature and disappear from the bottom up,and the boiling stops in the end.The heat transfer performance of heat pipe varies with heating power.Within the experimental range,with the increase of heating power,the temperature difference between the heating section and the condensation section of the heat pipe increases,and the equivalent thermal conductivity increases.The smallest was 566.51W/m·~oC at 100W and the largest was1234.92W/m·~oC at 220W.With the increase of heating temperature in heating section,the heat transfer capacity of heat pipe increases.The heat transfer capacity is 113.44W at 400~oC and 261.83W at 600~oC.The increase of heat input speeds up the temperature rise in the heating section of the heat pipe,and the working medium in the evaporation section vaporizes rapidly to the condensation section for heat release.The scouring of the liquid film in the condensation section by steam reduces the operating resistance and enhances the heat transfer performance.When the heating power is fixed,the heat transfer performance of heat pipe increases with the increase of the length of heating section.When the length of condensation section is too short,it is difficult for working substance vapor to condensate and return in time in the condensation section,resulting in poor heat transfer performance of heat pipe.In the working conditions involved in this paper,the heat pipe with the length ratio of heating section to condensation section 11:1 has better heat transfer performance.The temperature difference between upper and lower of 6m super-long heat pipe is only 13~oC at 2000 W power,and the equivalent thermal conductivity is 534203.83W/m·~oC.It has excellent isothermal and thermal conductivity.Based on Aspen Plus software,a simulation study on an offshore platform gas turbine flue gas waste heat recovery model was carried out.It is concluded that the output power of gas turbine decreases with the increase of air inlet temperature,which is consistent with the experimental value.Under ISO condition,if the flue gas temperature of gas turbine is reduced to 150 ~oC,the saturated vapor of 180 ~oC can be more than 20 t/h.If the air inlet temperature varies in the range of-30~oC-45~oC,the steam can be produced in the range of 17.8t/h-23.6t/h.Because of the small proportion of gas,the change of gas temperature is relatively small,but with the increase of gas temperature,the exhaust temperature increases correspondingly,and the recovery heat also increases slightly.With the increase of air humidity,the air flow rate also increases.The net output power,saturated steam and exhaust gas temperature of gas turbine all decrease,and the change is small.When the power generation load changes,the saturated steam output will also change due to the change of flue gas volume.Under full load,the flue gas emission temperature is 338.64~oC,but under 40%load,the final flue gas emission temperature is 109.51~oC,which is 67.66%lower than that under full load.According to the field conditions and heat demand of an offshore oil platform,the super-long heat pipe studied by experiment was used in the heat pipe steam generator,which was successfully applied on the offshore platform.In order to further recover the waste heat of flue gas,the gas turbine flue gas temperature and heat demand are divided into three levels.The cascade utilization of waste heat of gas turbine was simulated.The first stage is heat pipe heat conducting oil furnace with high temperature requirement up to 250~oC for production heating,the second stage is heat pipe steam generator with water vapor of 180 ~oC for replacement of electric dehydration heater.The third stage is a heat pipe water heater with a temperature of 75~oC.It is used for heating and reinjecting water.It can make full use of the waste heat of flue gas,and the final discharge temperature can be close to 100 ~oC.The research in this paper provides experimental research and engineering application for waste heat recovery of offshore gas turbine flue gas,and has a certain reference value for efficient cascade utilization of gas turbine flue gas.