Main characteristics of biodiesel
As we all know, diesel oil molecules are composed of about 15 carbon chains. It is found that vegetable oil molecules are generally composed of 14- 18 carbon chains, which is similar to the number of carbon chains of diesel oil molecules. Therefore, biodiesel is a new fuel made from renewable vegetable oil such as rapeseed. From the chemical composition analysis, biodiesel fuel is a kind of higher fatty acid methane, which is obtained by decomposing glyceride with unsaturated oleic acid C 18 as the main component. Compared with traditional diesel, biodiesel has the following incomparable characteristics:
1. It has excellent environmental protection characteristics. Mainly because the sulfur content in biodiesel is low, and the emission of sulfur dioxide and sulfide is low, which can be reduced by about 30% (70% when there is catalyst); Biodiesel does not contain aromatic alkanes that will pollute the environment, so the harm of tail gas to human body is lower than that of diesel. Experiments show that compared with ordinary diesel, the use of biodiesel can reduce air toxicity by 90% and cancer incidence by 94%. Due to the high oxygen content of biodiesel, the smoke emitted during combustion is less, and the carbon monoxide emission is reduced by about 10% compared with diesel (95% when there is a catalyst); Biodiesel has high biodegradability.
2. It has good low-temperature engine starting performance. The cold filtration point without additives reaches -20℃.
3. It has good lubrication performance. Fuel injection pump, engine cylinder block and connecting rod have low wear rate and long service life.
4. It has good safety performance. Biodiesel is not dangerous because of its high flash point. Therefore, the safety in transportation, storage and use is obvious.
5. It has good fuel performance. The high cetane number makes it burn better than diesel oil, and the combustion residue is slightly acidic, which prolongs the service life of catalyst and engine oil.
6. It is renewable. As a renewable energy, unlike oil reserves, its supply will not be exhausted through the efforts of agricultural and biological scientists.
7. Under the condition of not replacing the diesel engine, it can be directly added for use, and at the same time, there is no need to add additional refueling equipment, storage equipment and special technical training for personnel.
8. Mixing biodiesel and petrochemical diesel in a certain proportion can reduce fuel consumption, improve power performance and reduce tail gas pollution.
The excellent performance of biodiesel makes the exhaust emission index of the engine using biodiesel not only meet the current Euro II standard, but also meet the stricter Euro III emission standard to be promulgated and implemented in Europe. Moreover, because the carbon dioxide emitted by biodiesel combustion is far lower than the carbon dioxide absorbed during plant growth, the global warming caused by carbon dioxide emission has been improved, which is a major environmental problem that harms human beings. Therefore, biodiesel is a real green diesel.
Method for producing biodiesel
At present, biodiesel is mainly produced by chemical method, that is, animal and vegetable oils react with low-carbon alcohols such as methanol or ethanol in acidic or alkaline catalysts at high temperature (230-250℃) to generate corresponding fatty acid methyl ester or ethyl ester, and then biodiesel is obtained after washing and drying. Methanol or ethanol can be recovered in the production process, and the production equipment is the same as the general oil-making equipment, and about 10% of by-product glycerol can be produced in the production process.
At present, the main problem of biodiesel is high cost. According to statistics, 75% of the cost of biodiesel preparation is the cost of raw materials. Therefore, the key to the practical application of biodiesel is to use cheap raw materials, improve the conversion rate and reduce the cost. The United States has begun to study plants with high oil content through genetic engineering, Japan uses industrial waste oil and waste frying oil, and Europe grows oil-rich crops on land unsuitable for growing food.
However, the chemical synthesis of biodiesel has the following disadvantages: the process is complex, the alcohol must be excessive, the subsequent process must have corresponding alcohol recovery device, the energy consumption is high, the color is dark, and the unsaturated fatty acids in fat are easy to deteriorate at high temperature; The esterification product is difficult to recover and the cost is high; Waste lye is discharged in the production process.
In order to solve the above problems, people began to study the synthesis of biodiesel by biological enzyme method, that is, animal fat and low-carbon alcohol were esterified by lipase to prepare the corresponding fatty acid methyl ester and ethyl ester. Enzymatic synthesis of biodiesel has the advantages of mild conditions, low alcohol consumption and no pollution discharge. But the main problem at present is that the conversion rate of methanol and ethanol is low, generally only 40%-60%. At present, lipase is effective for esterification or transesterification of long-chain fatty alcohols, but the conversion rate of short-chain fatty alcohols (such as methanol or ethanol) is low and short-chain alcohols are toxic to enzymes, so the service life of enzymes is short. By-products glycerol and water are difficult to recover, which not only inhibits the formation of products, but also is toxic to immobilized enzyme, making the service life of immobilized enzyme short.
The production of diesel by "engineering microalgae" has opened up a new technical way for diesel production. The National Renewable Laboratory (NREL) of the United States has constructed "engineering microalgae" through modern biotechnology, that is, "engineering microcystis" of diatoms. Under laboratory conditions, the lipid content in "engineered microalgae" can be increased to more than 60%, and outdoor production can also be increased to more than 40%. Generally speaking, the oil content of microalgae is 5%-20% in nature. The increase of oil content in "engineered microalgae" is mainly due to the high expression of acetyl-CoA carboxylase (ACC) gene in microalgae cells, which plays an important role in controlling oil accumulation. At present, we are studying the selection of appropriate molecular vectors to fully express ACC gene in bacteria, yeast and plants, and further introduce the modified ACC gene into microalgae to obtain more efficient expression. Using "engineering microalgae" to produce diesel oil has important economic and ecological significance. Its advantages are: high microalgae production capacity, using seawater as natural culture medium, saving agricultural resources; It is dozens of times higher than terrestrial plants. The produced biodiesel does not contain sulfur, does not emit toxic gas when burning, and can be degraded by microorganisms when discharged into the environment without polluting the environment. Developing oil-bearing microalgae or "engineering microalgae" to produce biodiesel is a major trend.
Development Status of Biodiesel Abroad
Biodiesel was born in 1988, which was invented by Niels Company in Germany. It is a clean fuel extracted from rapeseed oil. Outstanding environmental protection and renewability have attracted great attention from developed countries, especially resource-poor countries. Encouraged by industry norms and policies, western countries have taken a series of positive measures to develop biodiesel. In order to facilitate the popularization and use, Germany, Italy and other countries have formulated technical standards for biodiesel. For example, American authority ASTM issued standards in 1996 and 2000 to improve the industrialization conditions of biodiesel, and the government actively encouraged them to give some subsidies on the price of biodiesel. For example, German farmers can get a subsidy of 1000 DM/hectare for planting rapeseed with biodiesel as raw material, and the production of biodiesel is tax-free.
The production of biodiesel from surplus rapeseed oil and soybean oil in Europe and North America has been widely used. At present, biodiesel is mainly produced by chemical method. Vegetable oil is esterified with methanol or ethanol in acidic or alkaline catalyst at 230-250℃ to generate corresponding fatty acid methyl ester or ethyl ester biodiesel. At present, the technology of synthesizing biodiesel by biological enzyme method is still under study. Compared with ordinary diesel, biodiesel is more conducive to environmental protection, making the emission of toxic organic matter in diesel exhaust only110, particulate matter 20%, and CO2 and CO only 10%. According to the Kyoto Protocol, the EU will reduce emissions by 8% between 2008 and 20 12. According to the life cycle analysis of the influence of fuel on CO2 in the whole atmosphere, the CO2 emitted by biodiesel is about 50% less than that of fossil diesel. To this end, the European Union recently issued two new directives to promote the application of biofuels in the automobile fuel market, which will further promote the development of European biodiesel industry. Compared with conventional diesel, biodiesel is more than twice as expensive. Therefore, the new directive requires EU countries to reduce the tax rate of biodiesel and stipulate the sales ratio of biodiesel in European automobile fuel.
The biodiesel industry in western countries has developed rapidly. In recent years, western countries have increased their investment in the commercialization of biodiesel, which has increased the investment scale of biodiesel and increased the number of projects started. The United States, Canada, Brazil, Japan, Australia, India and other countries are actively developing this industry. At present, there are four biodiesel production plants in the United States with a total production capacity of 300,000 tons/year. The EU countries mainly use rape as raw material, and the output of biodiesel in 200 1 year has exceeded 1 10,000 tons. In 2000, Germany's biodiesel reached 450,000 tons. In June 2006, Germany also invested 50 million marks in Hyde area to build a biodiesel factory with an annual output of 654.38+10,000 tons. There are seven biodiesel production plants in France with a total capacity of 400,000 tons/year. The use standard is to add 5% biodiesel to ordinary diesel, and the tax rate of biodiesel is zero. Italy has nine biodiesel production plants with a total production capacity of 330,000 tons/year, and the biodiesel tax rate is zero. Austria has three biodiesel production plants with a total production capacity of 55,000 tons/year, and the tax rate is 4.6% of that of petroleum diesel. Belgium has two biodiesel production plants with a total capacity of 240,000 tons/year. Japan's biodiesel production capacity has also reached 400,000 tons/year.
Development Status of Biodiesel in China
Our government has formulated some policies and measures to solve the problems of energy saving, substitution and environmental protection, and some scholars and experts have devoted themselves to the research and advocacy of biodiesel. Although the research and development of biodiesel in China started late, it has developed rapidly, and some scientific research achievements have reached the international advanced level. The research content involves the distribution, selection, cultivation, genetic improvement, processing technology and equipment of oil plants. At present, all aspects of research have achieved initial results, which will undoubtedly contribute to the further research and development of biodiesel in China. It can be predicted that in 2-3 years, China's research in this field will make a breakthrough and reach the practical level.
Academician Min Enze, a famous scholar, clearly put forward the topic of developing clean-fuel biodiesel for the first time in the book Green Chemistry and Chemical Engineering: the former Ministry of Machinery Industry and the former sinopec group allocated special funds in the 1980s, and the project was undertaken by Shanghai Internal Combustion Engine Research Institute and Yishan Agricultural Machinery in Guiwai for 10 year, and invited Zhan, an expert from China Petrochemical Research Institute, to do a lot of basic experiments and explorations; Mr. Shi Delu from China Agricultural Engineering Research and Design Institute also conducted experiments on biodiesel in 1985. The Sino-European cooperative research project undertaken by Liaoning Energy Research Institute also involves biodiesel; China University of Science and Technology, Henan Polytechnic University and Army Institute of Chemistry have also conducted research on biodiesel to varying degrees.
The systematic research began with the key scientific research project of Chinese Academy of Sciences during the Eighth Five-Year Plan period: "Research and application technology of oil plants", and completed the investigation of oil plant resources and the research of cultivation technology in Jinsha River basin, and established a 30-hectare Jatropha curcas cultivation demonstration film. Since the early 1990s, Changsha Institute of New Technology and Hunan Academy of Forestry have conducted cooperative research on energy plants and biodiesel for 65,438+00 years. During the Eighth Five-Year Plan period, the technology of preparing methyl ester fuel oil from bark oil and its combustion characteristics were studied. During the Ninth Five-Year Plan period, the national key scientific research project "Vegetable oil energy utilization technology" was completed.
During the period of 1999-2002, Hunan Academy of Forestry undertook and presided over the introduction of foreign advanced forestry technology (948 Project) by the State Forestry Administration, that is, "the introduction of energy tree species Lvwangshu and its utilization technology", and introduced excellent clones of energy tree species eucalyptus Tim-calli from South Africa, the United States and Brazil. Developed the milk extraction equipment of green Yushu; The composition and fuel characteristics of elm latex were studied. The catalytic cracking of elm latex achieved phased results.
However, compared with foreign countries, there is still a considerable gap in the development of biodiesel in China, which has remained in the primary research stage for a long time and failed to form the industrialization of biodiesel: the government has not yet issued a set of policies and measures to support, preferential and encourage biodiesel, let alone formulated a unified standard for biodiesel and implemented an industrialization development strategy. Therefore, after China's entry into WTO, it is more urgent to speed up the industrialization of efficient and clean biodiesel under the background of how to face the dual pressures of rapid economic development and environmental protection.
Prospect of biodiesel industrialization in China
In 2003, driven by the sustained and rapid growth of the national economy, China's oil market demand grew strongly, and the total demand for refined oil increased by double digits, reaching 1 1.4%, an increase of 7.4 percentage points over the previous year, which promoted the substantial growth of oil imports and made China a big oil consumer and importer. There is a shortage of resources in the oil market, and prices have risen in an all-round way. According to the statistics of China Logistics Information Center, the cumulative average price of petroleum and its products in China in 2003 increased by 1 1.8% compared with the previous year. The preliminary analysis shows that the supply and demand situation of China oil market in 2004 is basically similar to that in 2003, and it will continue to maintain the pattern of strong consumer demand and basic balance between supply and demand, but it does not rule out the local and structural supply shortage caused by factors such as seasons and transportation. It is estimated that the consumption of crude oil in China in 2004 will be 270 million tons, and the net import may exceed 654.38 billion tons.
China is a net importer of oil, and its oil reserves are very limited. A large amount of imported oil poses a threat to China's energy security. Therefore, improving the quality of oil products is more practical for China. Biodiesel has three advantages: renewable, clean and safe. Experts believe that biodiesel is of great strategic significance to the adjustment of agricultural structure, energy security and comprehensive management of ecological environment in China. At present, automobile diesel has become a development direction of automobile industry. According to experts' prediction, by 20 10, the world demand for diesel will increase from 38% to 45%, and the supply of diesel is seriously insufficient, which provides a broad development space for rapeseed to produce biodiesel. The development of biodiesel industry can also promote the rural, economic and social development of China. If we develop oil crops to produce biodiesel, we can find a way to transform agricultural and forestry products into industrial products, which will help adjust the agricultural structure and increase farmers' income.
The balance between supply and demand of diesel oil will also be the focus of the development of China oil market for a long time to come. Insiders pointed out that by 2005, with the increase of China's primary processing capacity, there will be some export space for gasoline and kerosene, while the supply gap of diesel oil is still large. It is predicted that by 20 10, the demand for diesel will exceed10 million tons, an increase of 24% over 2005. By 20 15 years, the market demand will reach about 65438+300 million tons. In recent years, although refining and chemical enterprises have continuously improved the diesel-steam ratio through continuous technical transformation, they still cannot meet the requirements of diesel-steam consumption. At present, the production ratio of diesel and steam is about 1.8, while the consumption ratio of diesel and steam in the market is above 2.0, and the consumption ratio of diesel and steam in Yunnan, Guangxi, Guizhou and other provinces is even above 2.5. With the acceleration of the western development process and the start of major infrastructure projects in the national economy, the contradiction between diesel and gasoline ratio is more prominent than before. Therefore, the development of biodiesel is not only in line with the direction of adjusting the oil structure and improving the ratio of diesel to gasoline in the petrochemical industry, but also has far-reaching significance.
At present, China's biodiesel technology has made great achievements: Hainan Zhenghe Bioenergy Company, Sichuan Gushan Grease Chemical Company and Fujian Zhuoyue New Energy Development Company have all developed technologies with independent intellectual property rights, and successively built production facilities with a scale of over 10,000 tons, which indicates that biodiesel, a high-tech industry, has been born in China.
The person in charge of China Academy of Engineering introduced that China's "Tenth Five-Year Plan" proposed the development of various petroleum substitutes, and identified the development of bio-liquid fuel as the national industrial development direction. Biodiesel industry has been supported by the leaders of the State Council, the State Planning Commission, the State Economic and Trade Commission, the Ministry of Science and Technology and other government departments, and has been included in the relevant national plans.
China is rich in raw material resources for the development of biodiesel. China has a vast territory, a large geographical span, different distribution of water and heat resources, and rich and diverse energy plant resources. The main families are Euphorbiaceae, Lauraceae, Myrtaceae, Apocynaceae, Compositae, Leguminosae, Cornaceae, hyacinthus orientalis and Rosaceae. At present, the development and utilization of biodiesel in China is still in its infancy. In order to reduce the cost of biodiesel as a whole and make it play a greater role in the transformation of China's energy structure, only by developing in the direction of base and scale, implementing intensive management and forming industrialization can we take the road of biodiesel development in line with China's national conditions. With the deepening of reform and opening-up, in the process of global economic integration, under the favorable situation of China's accession to the WTO, China's economic level will be further improved, and its demand for energy will increase. As long as the research results of biodiesel are transformed into productivity and industrialized, its application in diesel engines, diesel power plants, air conditioning equipment, rural fuels and so on will be very broad.
Information source: Information Center of Beijing Yanshan Petrochemical Company Research Institute.