Research on the latest energy dimethyl ether and r

2022-07-25
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Research on new energy dimethyl ether and rubber sealing technology

as a new green energy, dimethyl ether (DME) has a very broad prospect. At the same time, DME also puts forward new adaptability requirements for its matching materials, such as the performance of engine rubber seals. How to meet these new requirements has become an urgent problem to be studied and solved

although China is a big oil producer, it is also a big oil importer. The development and production of domestic oil alone can no longer meet the needs of economic and social development, and the contradiction between supply and demand is becoming increasingly prominent; On the other hand, China is also a big country with coal and natural gas resources. Relying on these resources to develop coal to methanol and dimethyl ether as oil substitutes can make up for the shortage of China's oil resources; At the same time, dimethyl ether is also an important fine chemical product. Therefore, the production, application and development of DME are of great significance to the development of China's energy chemical industry, fine chemical industry and environmental protection

dimethyl ether application

dimethyl ether, also known as methyl ether and dimethyl oxide, is referred to as DME (dimethyl ether), with the molecular formula CH3OCH3. At room temperature and normal pressure, it is a colorless gas with weak toxicity and slight ether smell. Its vapor pressure is 0.5MPa at room temperature, which is easy to condense and vaporize. Dimethyl ether has excellent miscibility and can be miscible with most polar and nonpolar organic solvents

dimethyl ether is mainly used as propellant, fuel, refrigerant, foaming agent, solvent, extractant, etc. of aerosol. Propellant as aerosol has been actually used in China, while the application as refrigerant and foaming agent has not been developed in China. The most important uses of dimethyl ether are as fuel. First, it can replace diesel oil as fuel for diesel vehicles; Second, as a fuel to replace civil liquefied petroleum gas

used as civil clean fuel

among many alternative fuels, dimethyl ether is a promising fuel. As a civil clean fuel, it has many advantages: under the same temperature conditions, the saturated vapor pressure of dimethyl ether is lower than that of liquefied petroleum gas (LPG), and its storage and transportation are safer than that of liquefied petroleum gas; The lower explosion limit of dimethyl ether in air is twice as high as that of liquefied gas, so it is safer as a fuel than liquefied gas; According to relevant tests, the calorific value of DME pre heating gas (17.68mj/m3) is greater than that of LPG pre heating gas (16.38mj/m), and the combustion temperature is high. Therefore, its combustion is better than LPG. Dimethyl ether contains oxygen, single component, short carbon chain, good combustion performance, high thermal efficiency, and no residual liquid and black smoke during combustion. It is a high-quality and clean civil fuel

substitute diesel oil for automobile fuel

dimethyl ether is the simplest ether compound, odorless, non-toxic and non corrosive to metals. For automotive diesel engines, dimethyl ether has a higher cetane number (55 ~ 60) than diesel (40 ~ 55) and a lower spontaneous combustion temperature, so it is easier to be compression ignited. It is very suitable for compression ignition engines and can reduce engine noise by 10%~15%. It is an ideal alternative fuel for diesel engines. There is no C-C bond in the molecular structure of dimethyl ether, only C-H bond and C-O bond. The mass fraction of oxygen is 34.18%. Dimethyl ether has large latent heat of vaporization, short ignition delay period, less premixed combustion during combustion, less incomplete combustion products, and can reduce CO, hydrocarbon, NOx and black smoke emissions in automobile exhaust. Dimethyl ether can be produced not only from coal and natural gas, but also from biomass. In a sense, it is a renewable fuel. Therefore, dimethyl ether is a diesel alternative fuel with low cost, low emission and high combustion efficiency

study on the compatibility between DME fuel and rubber seals

DME has a boiling point of -24.19 ℃ and is in gaseous state at room temperature (20 ℃), so it needs to be pressurized (exceeding its saturated vapor pressure at service temperature) to make it a liquid for combustion in the engine. This requires that the vehicle fuel supply system and fuel tank must be well sealed and pressure maintained. It is found that the rubber seals in common fuel supply systems will swell and age after long-term contact with dimethyl ether, and the mechanical properties will deteriorate and become invalid. Because the viscosity of dimethyl ether is very low, direct combustion on the engine will cause the wear of precision coupling parts. It is usually necessary to add a certain proportion of lubricant to improve its lubrication performance. Because different rubber materials have different resistance to different media, it is of great application value to study the sealing rubber which is resistant to both dimethyl ether and lubricant

the oil resistance of rubber depends on the structure of rubber and the chemical properties of organic medium. The interaction between rubber and solvent follows the principle of similar miscibility, that is, it is considered that the rubber with similar polarity to the solvent is easy to dissolve in the solvent, and the liquid with similar polarity can dissolve the same solute (i.e. miscible). This principle has important guiding significance for the rational selection of test rubber

experimental study on pure dimethyl ether resistant rubber

determining the polarity of dimethyl ether fuel plays an important role in selecting appropriate rubber materials. Liquid dimethyl ether is a polar solvent, and its removal method: please check whether the controller selection in the joint setting is appropriate, and the polarity is caused by the oxygen atom in the middle of the molecular chain. NBR, EPDM and silicone rubber were selected for dimethyl ether swelling resistance test. The polarity of the three rubbers was NBR> silicone> EPDM. NBR is a copolymer of acrylonitrile and butadiene. It is the most commonly used oil resistant rubber. Its polarity is strong and increases with the increase of acrylonitrile content, so the oil resistance is significantly improved. EPDM is polar and has good stability to various polar media. In general rubber, EPDM has the best aging resistance. Silicone rubber has weak polarity, and its high and low temperature resistance is the best among the three rubbers, which is very important for automotive engines. The order of the dimethyl ether resistance of the three selected rubbers is: EPDM> NBR> silicone. Silicone rubber is not resistant to dimethyl ether because of their similar polarity. Compared with NBR, EPDM has the most obvious difference in polarity and dimethyl ether polarity, so it has the best resistance to dimethyl ether

study on the properties of rubber resistant to dimethyl ether containing lubricant

dimethyl ether is a low viscosity liquid. The test shows that when pure dimethyl ether is used as fuel, the precision coupling parts in the fuel system wear quickly. The main way to improve the lubricating performance of dimethyl ether is to add lubricating additives. In the engine fuel supply system, the clearance between the coupling parts is very small (about 2 ~ 4 μ m) Its lubrication mode is mainly boundary lubrication. In boundary lubrication, the viscosity of the liquid has little effect on the lubrication. What plays a role is the single molecule oil film formed on the metal surface by physical or chemical adsorption of polar molecules. The test shows that vegetable oil containing polar molecular head is a good boundary lubrication additive. Adding a certain proportion of vegetable oil to dimethyl ether can effectively reduce the wear of engine precision coupling parts, and will not significantly change its good combustion characteristics. At present, the polarity of dimethyl ether containing lubricant has not been clearly described, but it can be preliminarily predicted and determined by the swelling difference of different polar rubbers. The volume change rate of neoprene, natural rubber (NR) and EPDM soaked in dimethyl ether containing lubricant for 96h( δ 5) The swelling degree of EPDM and natural rubber is obviously greater than that of neoprene. Since EPDM and natural rubber are non-polar rubber, while neoprene has certain polarity, it is preliminarily judged that dimethyl ether containing lubricant may have non-polar characteristics according to the principle of similar compatibility. Anhan company will demonstrate the world's first "magnetic control capsule endoscope robot system" in Ningbo for the first time, and select different test rubbers based on this to select the most suitable sealing rubber for practical use. According to the above analysis, the rubber resistant to dimethyl ether containing lubricant should have strong polarity, so non-polar rubber (such as EPDM, natural rubber, etc.) and weak polar rubber (such as silicone rubber, neoprene, etc.) will not be selected for further tests. Taking into account other mechanical properties of rubber and its application environment in vehicle engines, butadiene rubber, fluorosilicone rubber and fluorosilicone rubber were selected for solvent resistance test. For fluororubber and fluorosilicone rubber, fluorine atoms replace the original hydrogen atoms in the side chain of the rubber molecular structure, which greatly enhances the polarity of the rubber. Fluororubber and fluorosilicone rubber have good stability to many chemical solvents. Fluororubber has good mechanical properties, tensile strength and hardness. Fluorosilicone rubber not only maintains a series of excellent properties of silicone rubber, but also has the oil resistance and solvent resistance of fluorosilicone rubber. Compared with fluororubber, it has the same oil resistance, better cold resistance and compression set resistance, and shows excellent performance from high temperature to low temperature. It is an ideal oil resistant rubber

3 kinds of rubbers have different degrees of swelling after soaking for a certain time, but their swelling degree is much lower than that of EPDM and natural rubber. The order of swelling rate is FMQ> NBR> FPM. The tensile strength and elongation at break reflect the mechanical properties of rubber materials. For these two indexes, fluorosilicone rubber has little change after a long test time, and the performance is the best, while both NBR and fluorosilicone rubber are significantly reduced. The hard lift performance of fluorosilicone rubber is the change of main attack direction, which is the most stable among the three rubbers

in general, the order of resistance to dimethyl ether containing lubricant is FMQ> NBR> FPM. After 40d long-term immersion test, the swelling rate of fluorosilicone rubber remained at a very low level, and the mechanical properties did not change significantly, and remained stable with time. Therefore, it can be considered that fluorosilicone rubber is a rubber material with excellent resistance to dimethyl ether fuel. (end)

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