The alternative fuel for internal combustion engines is surviving and creeping forward in the midst of multiple pressures.
The embarrassment lies in the fact that in the face of the community’s eager desire for reducing emissions from large-scale energy-consuming internal combustion engines, a variety of technical routes for internal combustion engine alternative fuels coexist and are at the stage of scientific research and demonstration. Up to now, there is no single fuel that can completely replace petroleum to drive the rapidly increasing internal combustion engine every day.
It is precisely because of this that there is currently no alternative fuel that can be widely recognized and supported by the market and the government. This to a certain extent also delayed the development and breakthrough of technology in this field.
On April 2nd, China National Internal Combustion Engine Industry Association’s "Traditional Energy Power Plant (Internal Combustion Engine) Highly Effective Alternative Fuel Technology Symposium", researchers of various alternative fuels expressed similar similar frustrations.
Although Mr. He Guangyuan, Minister of Alcohol, and related departments, academics, and industry have promoted methanol, methanol seems to have seen the dawn of becoming the mainstay of alternative fuels for internal combustion engines in China. However, there is still room for further improvement in the production and application of methanol. Market and user acceptance will also take time.
At the same time, China is actively exploring various other clean and efficient alternative fuels.
Dimethyl ether is still difficult
At present, the research of alternative fuels is very extensive. The so-called substitute fuel refers to a fuel that can replace or partially replace the conventional fuel (gasoline, diesel, kerosene) of the internal combustion engine. There are two types of substitute fuels: First, liquid fuels, mainly alcohols (methanol, ethanol), biodiesel, etc. The second is gaseous fuel, mainly natural gas, liquefied petroleum gas, dimethyl ether and so on. As far as the actual use of alternative fuels is concerned, it is firstly required that the engine of the internal combustion engine can be used without major changes. Secondly, there should be sufficient resources for safer and more convenient production, transportation, use and storage. In addition, the use of alternative fuels will not reduce the power, economy, emissions, and durability of the engine.
Among them, dimethyl ether is one of the important technical routes.
At the seminar on April 2nd, Professor Liu Shenghua from Xi'an Jiaotong University introduced that DME is a colorless, odorless gas with excellent combustion performance, cleanness, high cetane number, and good dynamic performance. With less pollution and a little pressure, it becomes a liquid, which is very suitable as an alternative energy source for compression ignition engines. Vehicles that use this fuel can meet California's ultra-low emission standards.
It has been reported that NKK Corporation of Japan successfully developed equipment for producing dimethyl ether from low-quality coal, and completed tests with dimethyl ether as a vehicle fuel in 1998 with Sumitomo Metal Industry Co., Ltd. Gases pollute the environment, producing 20% ​​less nitrogen oxides than diesel.
Due to its excellent characteristics, dimethyl ether is also considered to be one of the ideal alternative fuels for diesel engines. According to reports, Shanghai Jiaotong University, Shanghai Automotive Industry Corporation (Group) Corporation, Shanghai Diesel Engine Co., Ltd. and Shanghai Coking Plant are jointly developing dimethyl ether fuel city buses. The goal is to establish a demonstration vehicle fleet and promote dimethyl ether fuel vehicles. Tests at the Institute of Internal Combustion Engines at Taiyuan University of Technology show that dimethyl ether as a vehicle fuel is cleaner than natural gas and liquefied gas.
Liu Shenghua believes that the production and application of dimethyl ether is one of the promising areas for China's future energy technology to achieve leapfrog development. In the recent five years, the demand for dimethyl ether in China will reach 5 to 10 million tons. As a vehicle fuel, it will help alleviate the tight supply of diesel oil in China. The market prospect is very broad.
Looking at the current status of domestic and foreign DME fuel engine research and development, Liu Shenghua pointed out that there are still many problems in the process of industrialization of DME engines.
First of all, dimethyl ether fuel is gaseous at room temperature and atmospheric pressure, and its physicochemical properties are very different from those of diesel fuel. Therefore, it is necessary to develop and optimize an engine fuel supply system suitable for dimethyl ether fuel. In addition, the dimethyl ether thermal value is only 64.7% of the diesel calorific value, the dimethyl ether liquid density is only 78.5% of the diesel density, in order to achieve the original diesel engine power, the volume of dimethyl ether supply is about 1.9 times that of diesel .
At the same time, due to differences in engine fuel injection and combustion systems and conventional diesel engines caused by physicochemical properties of dimethyl ether, studies including engine intake and combustion system matching, pressurization and performance matching will greatly affect the dimethyl ether engine Overall performance.
Secondly, the low viscosity of dimethyl ether (1/20 of diesel oil) makes it easy to leak dimethyl ether in the high-pressure fuel supply system, and it is also easy to cause early wear of parts. Although dimethyl ether is not corrosive to metals, it has corrosive effect on ordinary rubber and plastics. For engine parts wear, leakage and reliability-related issues caused by DME fuel, engine-related system sealing, lubrication, and material compatibility, as well as the optimal design and finalization of related components are the focus and difficulty of this study.
Other experts also pointed out that, from a practical point of view, the feasibility of replacing DME with diesel is not entirely dependent on the technical aspects, and its economy, ie price, is also a key factor. This economy is affected by many factors, such as crude oil prices, coal or natural gas prices, fiscal policies, and supporting facilities.
Biodiesel calls for "new energy" treatment
So, will biodiesel flare up?
Tsinghua University professor Wang Jianwei stated at the seminar on April 2 that biodiesel is one of the most possible large-scale applications of alternative fuels for vehicles following natural gas and ethanol. To achieve the goal of replacing energy in China by 2020, biodiesel applications must be considered as soon as possible.
According to him, biodiesel also has the characteristics of high cetane number, low sulfur content, no aromatics, high flash point, and good lubricity. It is an ideal alternative fuel for internal combustion engines.
Wang Jianwei said that in recent years, China has actively promoted the development of biodiesel. He said that the "Eleventh Five-Year Plan" 863 Plan, "Biodiesel Vehicle Adaptability Study" and other issues (2007 ~ 2008) have been completed. The National Development and Reform Commission plans to produce 200,000 tons of biodiesel in 2010 and 2 million tons in 2020. At the same time, the National Biodiesel Standard (B100) was promulgated and implemented in May 2008, and the national standard for blended fuel (BD5) will be promulgated soon.
In recent years, biodiesel has experienced a period of rapid expansion. Statistics show that in 2009, China's biodiesel production capacity has reached 1.5 million tons (a slight increase from 2008) and the output is 300,000 tons (it is the same as in 2008). However, since 2007, China has established the basic principle of “not competing with the people for grain and oil†and called for a stop of the technical route for producing biodiesel from edible oil.
Wang Jianqi pointed out that unlike the United States and Europe, which use high-quality edible oils (soybean oil and rapeseed oil) as raw materials, China currently uses inferior-quality waste oil (extracted oil angle, waste restaurant oil) as the main raw material, and will mainly consider adopting small- Wild seed oil such as tung oil (Jatropha) produces biodiesel.
At the same time, he explained that the “Biodiesel production standards and engine adaptability for vehicles†project jointly researched by CNOOC and Tsinghua University was completed in November 2009. At the same time, CNOOC started to promote the use of BD5 diesel fuel in Hainan Province in early 2010.
Wang Jianrong admitted that some researchers believe that biodiesel may generate dozens of unconventional emissions such as formaldehyde and benzopyrene during combustion. Among them, formaldehyde, benzopyrene and many other substances are carcinogenic and teratogenic substances that can cause various chronic diseases and gene mutations. But so far, due to testing difficulties, the unconventional emissions of biodiesel are still lacking data and it is necessary to study in detail.
Finally, he pointed out that the current bottleneck of biodiesel is insufficient resources and the price is too high. However, he said that it cannot be “fearing†and should actively adopt “open source†(full use of waste oil, waste oil, planting wild plants, genetically modified crops), and “encourage†(biodiesel duty-free or preferential treatment) measures to give Diesel "new energy" treatment.
Preliminary tests on unconventional emissions of biodiesel have shown that the vast majority of unconventional emissions have a low concentration and do not constitute a hazard; among them, formaldehyde, acetaldehyde, and toluene are all lower than the level of diesel emissions.
Wang Jiantao appealed that in the current situation of insufficient resources, it is also necessary to actively carry out “demonstration operations†in local areas and accumulate experience; once resources and opportunities in the international market emerge, they can be quickly applied on a large scale.
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