| High-sulfur fuel oil is used in the Iraqi Huashide oil-fired power station as boiler fuel,which leads to serious boiler corrosion and sulfur emissions far exceeding the standard,threatening the normal operation of power generation.In view of the existing problems,the properties of fuel oil in the power station were analyzed,and the reasons for boiler corrosion and nozzle clogging were obtained.On this basis,several composite organic acid magnesium corrosion inhibitors were developed,and their application properties and mechanism were studied.Based on the problems of serious low-temperature corrosion in the furnace and nozzle clogging,the properties of fuel oil and nozzle clogging were analyzed.The results show that power station fuel belongs to high-viscosity and high-sulfur fuel,and the fuel contains high sulfur and vanadium.On the one hand,the presence of vanadium leads to high-temperature corrosion,on the other hand,it catalyzes the conversion of sulfur dioxide into sulfur trioxide,which leads to an increase in the dew point of flue gas and intensifies low-temperature corrosion.The content of resins and asphaltenes in the nozzle plug is as high as 50%,and the rest is coke and a small amount of silica,calcium carbonate and other substances.The high content of resins and asphaltenes in fuel oil,poor fluidity and atomization,and insufficient combustion are the main reasons of nozzle clogging.Using stearic acid,palmitic acid,oleic acid and naphthenic acid as raw materials,four types of organic acid magnesium corrosion inhibitors were designed and synthesized,and their application properties were studied.The results show that the optimal synthesis route of organic acid magnesium corrosion inhibitors is shown below.The molar ratio of magnesium oxide to organic acid is 1:1,the neutralization reaction is reacted at 55℃for 1 h（magnesium palmitate for 1.5 h）,the over-basing reaction is reacted at the same temperature for 1 h,and the carbonation reaction is reacted at 65℃for 3 h.The quality yield of the products is close to95%,and the base number is around 300 mg KOH·g-1.The characterization shows that the nano-scale magnesium carbonate particles is coated with magnesium organic acid.Among them,the magnesium naphthenate corrosion inhibitor shows the best low-temperature corrosion inhibition performance and cheap price,so it is selected as the main agent in combination with the dispersant.To improve the combustion performance,an emulsifier with an HLB value of 3-6 is used as an auxiliary agent.The addition of the emulsifier and appropriate amount of water can make the fuel form W/O emulsion with a particle size of fewer than 9μm and reduce the viscosity of the fuel.When the main agent in the fuel is 1300μg·g-1 and the emulsifier is 750μg·g-1,the sulfur trioxide content in the flue gas is reduced by 72.4%,and the steel sheet corrosion rate is reduced by 21.6%,which can effectively inhibit low and high-temperature corrosion.The mechanism of organic acid magnesium corrosion inhibitors was studied.The results show that the synthesized products contain nano-scale magnesium carbonate particles,which can form a stable colloidal system under the encapsulation of magnesium organic acid micelles.Therefore,it is beneficial to exert the synergistic effect of inorganic-organic magnesium salt.On the one hand,it increases the dissolution and dispersion performance of additives in the fuel,and on the other hand,it continuously decomposes to produce magnesium oxide as the fuel burns.The combination of magnesium oxide and vanadium formed by fuel combustion to form high melting point compounds with a melting point of about 850℃,which directly inhibits high-temperature corrosion.The reduction of vanadium pentoxide weakens the process of catalyzing the conversion of sulfur dioxide to sulfur trioxide,significantly reducing the sulfur trioxide content in the flue gas,and reducing the flue gas dew point by 11.2℃,thereby inhibiting low-temperature corrosion. |
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