Dimethyl Ether What is dimethyl ether? Dimethyl ether is also called methoxymethane, dme gas or Dimethylaether, is an organic compound, a colorless and odorous flammable gas in the standard state, and its chemical formula is C2H6O or CH3-O-CH3. Relative vapor density (air is 1) 1.62, explosion range: 3.4鈥?7.0% (V/V), ignition temperature: 350掳C, dimethyl ether is easily soluble in water, alcohol and ether. DME is inert, non-corrosive, non-carcinogenic, and almost non-toxic. Dimethyl ether does not form peroxides on long-term exposure to air. It is a colorless gas under normal pressure and has a characteristic odor of ethers. As a substitute for freon, dimethyl ether is rapidly increasing in use in the aerosol and refrigerant industries. Dimethyl ether contains oxygen atoms, high thermal efficiency, complete combustion, clean tail gas without black smoke, and is an environmentally friendly fuel. With the rising price of petroleum and the environmental protection issues of vehicle and civil fuels, dimethyl ether, as a clean and environmentally friendly fuel, has attracted increasing attention from all walks of life. DME may become an important fuel in the near future. The price of petroleum products has been rising year after year, while the cost of coal-based dimethyl ether is low. DME will completely replace liquefied petroleum gas and partially replace diesel. Dimethyl ether fuel properties: (1) DME is an environmentally friendly non-pollutant, soluble in water and degradable. DME molecules are soluble in water, and can be degraded and soluble in water in the troposphere: rain and snow can absorb DME from the atmosphere, and it will not remain in the atmosphere forever. Degradation: In the atmosphere, large molecules become smaller molecules, long carbon chains become shorter carbon chains, and finally decompose into carbon dioxide and water. (2) DME has high combustion efficiency and low oxygen demand. Oxygen atoms are contained in the molecule of dimethyl ether, and the amount of air required for combustion is small: CH3OCH3+3O2=3H20+2CO2, the oxygen demand per kg of dimethyl ether is 1.46Nm3 Liquefied petroleum gas: C3H8+5O2=4H20+3CO2, the oxygen demand per kg of liquefied petroleum gas is 2.55Nm3 (3) DME is a clean fuel - clean, no black smoke. DME fuel has simple components and contains oxygen atoms, requires low air mixing, complete combustion, clean and no black smoke. (4) The economic benefits of dimethyl ether blending are the most obvious - the substitution ratio of blending is 1:1. When blending with liquefied gas, when the ratio does not exceed 25%, the substitution ratio with liquefied gas is 1:1. Reason: less oxygen demand, high thermal efficiency, when burning completely as fuel alone, the substitution ratio with liquefied petroleum gas is about 1.3:1. (5) At present, it is more reasonable to blend dimethyl ether - burner selection. When blending with liquefied gas, if the proportion of dimethyl ether does not exceed 25%, the liquefied gas burner can be used; when it is used as fuel alone, the natural gas burner can be used; it is best to use a special burner. Reason: The difference between oxygen demand and Wobbe index Wobbe index: Calorific value per unit volume/(relative specific gravity) 1/2 (6) DME has simple requirements for transportation and sealing鈥攕ealing materials. When blending with liquefied gas, the ratio does not exceed 25%, and the seals and hoses of liquefied gas storage, transportation, and burner can be used; when used as fuel alone, oil-resistant rubber (such as nitrile rubber) cannot be used for seals and hoses , seals and hoses need to be replaced. It can be changed to polytetrafluoroethylene, etc., and the O-ring can be changed to special rubber. 聽 What is the difference between dimethyl ether, diesel and liquefied petroleum gas? Physical PropertiesUnitDimethyl EtherDiesel FuelLiquefied Petroleum Gas Molecular Formula聽Ch3och3CxhyC3h8~ 4h10 Molecular Weight聽47190~22044~56 Boiling Point鈩?/p> 锛?4.9180~360锛?2.1 Liquid DensityG/Cm30.6680.840.501 Stoichiometric Air/Fuel RatioKg/ Kg9.014.612.72 Octane Number聽55~6040~55聽 Latent Heat Of VaporizationKj/Kg460(-20鈩?270聽 Low Calorific ValueMj/Kg28.4342.546.36 Ignition Point鈩?/p> 235250470 Liquid Viscosity聽0.154.4~5.4聽 Carbon Content Percentage%52.28681.8 Hydrogen Percentage%13.01418.2~17.9 Oxygen Percentage%34.800 Gas Pressure At 20掳CBar5.108.4 聽 It can be seen from the table that the properties of dimethyl ether are very similar to liquefied petroleum gas (LPG), and it is liquid at a lower pressure (5.1bar), so the infrastructure of liquefied petroleum gas can be used for DME completely, and oil tanks can be used for long-distance transportation , Oil tank trucks, can also be transported by low-pressure pipelines, or distributed to users with 15kg tanks. 聽 Dimethyl ether production process: At present, the production methods of DME at home and abroad mainly include one-step synthesis gas method and methanol method (two-step method). The methanol method is further divided into a methanol gas phase method and a methanol liquid phase method. The industrialization technology of the one-step process of syngas is not yet mature. 聽 The reasons are: 鈶?The existing technology has not been tested by the device; 鈶?Even according to the existing technology, its production cost is higher than that of the methanol gas phase method. 聽 One step method: The one-step synthesis gas method takes synthesis gas (CO + H2) as the raw material, and the methanol synthesis reaction and methanol dehydration reaction are completed in one reactor, accompanied by the CO shift reaction. The reaction formula is as follows: 2CO+4H2 = 2CH3OH CO+H2O =CO2 +H2 2CH3OH =CH3OCH3 +H2O Total reaction: 3CO + 3H2 =H3COCH3 +CO2 聽 The main feature of the one-step synthesis gas method lies in the advantages of the reaction, the methanol synthesis reaction and the methanol dehydration reaction are completed in one reactor. The reaction equilibrium constant is large, and the one-way conversion rate of synthesis gas is high, reaching 40.0% ~75.0%. Since the methanol generated by the reaction immediately undergoes dehydration reaction to generate dimethyl ether, the weakness of the low conversion rate of the synthetic methanol reaction is overcome. 聽 Two-step method: 1. Methanol liquid phase method Methanol dehydration reaction is carried out in liquid phase, under normal pressure or slight positive pressure, at 130掳C. Its chemical reaction formula is as follows: 2CH3OH =H3COCH3 +H2O The methanol liquid phase method is developed from the sulfuric acid method, and the production of dimethyl ether by the sulfuric acid method is the first half of the production process in the production process of dimethyl sulfate by the sulfuric acid method. Methanol dehydration reaction is carried out in liquid phase, under normal pressure or slight positive pressure, at 130掳C. Methanol enters the reactor after preheating, and undergoes dehydration reaction under the catalysis of inorganic acid. By heating, the dimethyl ether, water and phase equilibrium methanol produced by the reaction are vaporized and sent out of the reactor. The reaction product is condensed and separated, and the uncondensed gas phase is compressed and liquefied to obtain the product dimethyl ether. The condensate is separated by rectification, water is discharged from the tower kettle, and methanol is returned as raw material. 聽 2. Methanol gas phase method The chemical reaction formula of methanol dehydration reaction is as follows. Main reaction: 2CH3OH =H3COCH3 +H2O Main side reactions: CH3OH =CO + 2H2 H3COCH3 =CH4 +H2 +CO CO +H2O =CO2 +H2 Gas-phase catalytic dehydration of methanol is the most widely used industrial production method of dimethyl ether at home and abroad. It is characterized by mature and reliable technology, low investment, flexible product adjustment, simple process and low productio