Feasibility Study On Blending Hydrogen Into Natural Gas Distribution Networks

With the depletion of fossil fuels,renewable energy is becoming a research hotspot because of its clean,environmental protection and sustainable utilization.The production of renewable energy,such as solar energy,wind energy and hydropower,is unstable.When resources are abundant and terminal consumption is low,it can not be absorbed and has to be abandoned.One of the solutions to renewable energy consumption is to convert excess power into hydrogen as fuel for storage and use,which not only improves the cleanliness of energy but also guarantees the stability of energy utilization.But at present,most of the current end users are designed to serve natural gas and liquefied petroleum gas.As a direct fuel supply,hydrogen needs to replace gas appliances and require the laying of hydrogen pipeline,which leads to high cost.Due to the vigorous development stage of natural gas,the number of natural gas pipeline built in the world is huge and its transportation and carrying capacity are huge.So it is a better transition scheme to use hydrogen into the existing natural gas pipeline network.In order to study the feasibility of mixing and using natural gas and hydrogen,this paper carries out a theoretical,experimental and Simulation Analysis on the safety of the transmission and distribution system,the stability of the burning tool and the transmission capacity of the pipe network.The main contents and conclusions are as follows:(1)Analysis of interchangeability for hydrogen in natural gas.The interchangeability is determined by Wobbe index,combustion potential,A.G.A index and Weaver index,and the safety analysis is carried out with explosive limit calculation and diffusion.The results show that when the volume fraction of hydrogen mixed with methane is less than 24%,the mixing gas and reference gas have interchangeability.(2)Designing a standpipe experiment to verify the stratification of natural gas hydrogen mixture after standing at standpipe.The numerical changes of the ratio of methane to hydrogen at different heights in the riser were measured.The experimental results show that the difference of the ratio is very small,indicating that the mixing gas in the riser could not be stratified under the experimental conditions.(3)The combustion test is designed to test the stability and thermal performance of natural gas cooker in the presence of hydrogen.The combustion characteristics of hydrogen volume fraction of 5%,10%,15% and 20% of methane mixed under the working condition of 1kPa,2kPa and 3kPa were compared.The effects of hydrogen doping on heat load,thermal efficiency of stove,primary air coefficient and composition of flue gas were analyzed.The experimental data show that the methane-hydrogen mixing gas that meets the interchangeability requirement can be stable combustion on the 12 T natural gas cooker.(4)Based on the existing data of the JiangJin J area network,the topology model is established,and the energy flow model is used to simulate the steady / transient hydraulic simulation of the natural gas pipe network under the hydrogen mixing condition.The results show that the greater the percentage of hydrogen mixing and the greater the gas consumption,the greater the pressure drop of node pressure is when compared with that without mixing.