2065438+071October 27 17 The list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization was preliminarily sorted out for reference. Indoor emissions from biomass fuel (mainly wood) and household fuel combustion belong to Class 2A carcinogens.
Basic Introduction Chinese Name: Biomass Fuel mbth: Biomass Molding Fuel Explanation: biomass materials Burning as Fuel Process: Crushing, Mixing, Extrusion, Drying and other processes Main differences: Fossil Fuel Economic Fuel: Biomass Molding Fuel Source: Introduction of agricultural waste, livestock manure, etc., bio-combustion, bio-conversion to produce energy, biogas, ethanol, bio-diesel, hydrogen, bio-electricity, advantages Introduction Biomass energy refers to natural plants, manure and urban and rural organic waste. In addition to aesthetic value in the earth's ecological environment, biomass is a convenient and economical renewable energy for human beings. Biomass combines CO 2 with water through photosynthesis to form hydrocarbons (sugars) to build the skeleton of biomass, and in this process, solar energy is stored in the chemical bonds of structural compounds in organisms. In this process, with the proliferation of a large number of vegetation, it provides energy materials that can be used for a long time for human development and construction. When they are used, the basic elements (carbon, oxygen, hydrogen, nitrogen, etc. ) The substances that make up organisms are used by new organisms, and the energy stored in their chemical bonds is released or converted into other forms of energy. Photosynthesis Humans have discovered coal and petroleum-fossil biomass, which is the product of slow conversion of biomass (mainly sugar polymers) into lignin-like fragments. This process has gone through hundreds of millions of years, so they are generally considered as non-renewable energy. In the process of utilization of biomass and petrochemical resources, the most prominent difference of chemical bonds is the different impact on the environment: during biodegradation, most of the chemicals released by them return to the environment for biological reuse; However, petrochemical resources are buried deep underground for a long time, which can exist stably before development and utilization, and have little impact on the environment. However, when it burns, a large number of substances such as sulfur and heavy metals deposited in the petrochemical process are released, which makes it difficult for organisms to use, thus causing serious environmental pollution, such as acid rain. Therefore, compared with petrochemical energy, biomass fuel has many unique environmental values. It can reduce the pressure of climate change, soil erosion, water pollution and garbage accumulation, provide a living environment for wild animals and help to maintain better ecological health. In the carbon cycle of bio-utilization and regeneration, bio-combustion will not produce net CO 2 release, so the impact on the greenhouse effect is relatively small; There is less biological residue after fuel, and it can also be used as biological fertilizer. Table 1 lists some basic data of biological resources. Improving the utilization rate of existing resources and increasing the productivity of plants can realize the development of great biological potential. Especially the former, because of the low energy utilization rate of today's heat engine, a lot of biological potential is wasted. In order to solve this problem, the original bio-fuel is converted into other energy forms that meet modern needs, are efficient, easy to use and transport and store, such as electric energy, liquid or gas fuel, or treated solid fuel. In this way, more energy is extracted from biomass, which greatly improves the material and economic life in urban and rural areas. This has also become the core of bioenergy research. Simple biomass fuel utilization (burning wood to generate heat) Among biomass fuels, biomass molding fuel is more economical, and most of them are block fuels produced by processing straw crops, peanut shells, bark, sawdust and solid wastes (furfural residue, edible fungus residue, etc.). ). Its diameter is generally 6~8 mm, its length is 4~5 times of the diameter, and its crushing rate is less than 1.5%~2.0%. Dry water content is less than 10%~ 15%, ash content is less than 1.5%, sulfur content and chlorine content are less than 0.07%, and nitrogen content is less than 0.5%. If additives are used, they should be agricultural and forestry products, and the types and quantities used should be indicated. Direct combustion of bio-combustion is the most commonly used, direct and commercially feasible way to extract energy from biomass. From energy supply plants to agricultural residues and wastes, almost all forms of biofuels are used in combustion systems. Their combustion process is quite similar, which is generally divided into four processes: the evaporation process of water in biofuel (1) biomass, and even after several years of drying, the cellular structure of wood still contains 15% ~ 20% water; (2) The release of gas/vaporized components in biomass is not only the gas released by chimney, but also some combustible steam mixture and vaporized tar; (3) The released gas and oxygen in the air are burned at high temperature, and the pyrolysis products are ejected; (4) Residues (mainly carbon) in burning wood. In the case of complete combustion, the energy in the wood is completely released and the wood is completely reduced to ashes. The main problem of this process is low efficiency. As mentioned above, the overflowing flame and combustible gas make most of the heat useless and wasted. In the process of burning wood to make boiling water, 1m 3 dry wood contains 10G J of energy, while it takes 4 12K J of heat energy to raise the temperature of 1L water to 1℃, so it only takes less than 400K J to boil 1L water. But in fact, on a small stove, we probably need at least 50 times as much wood, that is, the efficiency is not more than 2%. The main methods to improve combustion efficiency are: (1) high enough temperature; (2) Sufficient oxygen; (3) Sufficient burning time; (4) Less energy escapes. Designing an efficient furnace or boiler provides a guarantee for this. In the past ten years, great progress has been made in boiler design to meet the needs of higher efficiency and less emissions (dust and carbon monoxide). Especially, great progress has been made in the design of combustion chamber, air supply for combustion and automatic control process of combustion. For manual boilers, the efficiency of gas turbine is increased from 50% to 75% ~ 90%, while for automatic boilers, it is increased from 60% to 85% ~ 92%. However, boilers are not easy to be used for long-term storage because all kinds of original biofuels are easy to degrade. And because of their relatively low energy density, long-distance transportation is also extremely uneconomical. Furthermore, although the boiler has made some progress in the utilization rate of heat energy, the overall energy utilization rate is still very low. Therefore, obtaining energy from biomass in other forms, improving energy utilization rate and meeting long-distance energy supply and reserve have become research hotspots since 1980s. Biogas production and use by biotransformation is the earliest process to provide energy by biotransformation. Biogas is the main component of methane (CH 4), which is formed by methane-producing bacteria decomposing and transforming organic matter under anaerobic conditions. Methane-producing bacteria are strictly anaerobic because their cells do not contain catalase and superoxide dismutase-oxygen has a lethal effect on them. In addition, they have special requirements for the types of carbon sources, and the available substrates can be divided into three categories: biogas (1) contains 1 ~ 6 short-chain fatty acids; (2) n-butanol or isobutanol containing 1 ~ 5 carbon atoms; (3) Three gases: hydrogen, carbon monoxide and carbon dioxide. Because of this special substrate requirement, technical and economic problems are put forward for the large-scale production of methane. Ethanol ethanol is the most important alcohol fuel. As an energy source, ethanol has many excellent characteristics, such as a wide range of fermentation substrates, including almost all kinds of original biological materials; Excellent combustion characteristics; The fuel has no residue and high octane number; Pollution-free fuels beneficial to the environment, especially lead-free, carbon dioxide, carbon monoxide, sulfur dioxide, particulates and other hydrocarbons; It can be directly mixed with petroleum and natural gas (ethanol accounts for 20% ~ 30% under the best conditions) as the liquid fuel of internal combustion engine, thus improving the fuel performance and reducing the discharge of three wastes. The fermentation process of ethanol is very similar to brewing, which generally involves the following four steps: (1) the growth, harvesting and transportation of ethanol-producing plants; (2) pretreatment, which transforms the original biological material into a substrate suitable for the fermentation process; (3) the substrate is converted into ethanol in the fermentation process and separated and extracted; (4) Treating fermentation waste residue, reducing pollution and recycling by-products. It can be used as raw material for ethanol fermentation and has a wide range of uses. In recent years, using lignocellulose as carbon source and fermentation system has become a research hotspot [7]. Lignocellulose is a low-cost renewable natural resource widely existing in nature, and its main components are polysaccharides (mainly cellulose and hemicellulose) and lignin. Polysaccharide can be used as a raw material for alcohol production, but it must be hydrolyzed by acid and enzyme into sugar before it can be directly used by cells. This process is a key step to reduce the cost of alcohol manufacturing industry. Lignin can not be biotransformed into ethanol, but it can be used as boiler fuel or biological fertilizer together with other fermentation residues. Ethanol fermentation The traditional ethanol fermentation process is to use yeast, especially Saccharomyces cerevisiae, to degrade glucose into pyruvate through EMP, and then decarboxylate pyruvate decarboxylase to reduce ethanol dehydrogenase to produce ethanol. At present, it is common to integrate pyruvate decarboxylase and alcohol dehydrogenase genes of Zymomonas mobilis into Escherichia coli by genetic engineering technology to produce ethanol. In the past few decades, the technology and efficiency of ethanol fermentation have improved rapidly, and new technologies and processes have emerged continuously, and the production scale has become larger and larger. Today, an average of 20 billion gallons of ethanol is produced by fermentation in the United States every year, which provides more than 1% of the total automobile fuel in the United States. Latin America, especially Brazil, is the largest ethanol fermentation area in the world. In Brazil, since 1975 national alcohol plan (ProAlcool), Brazil has produced nearly 90 billion liters of ethanol through sugarcane fermentation, and a large number of petrochemical energy sources have been replaced by ethanol, saving huge expenses for petrochemical energy imports. Biodiesel Biodiesel refers to fatty acid methyl ester produced by transesterification of vegetable oil with methanol, which is a clean biofuel. Due to the defects of ethanol in diesel engine (immiscible with diesel oil, unable to ignite directly, etc.). ) and the excellent combustion characteristics of biodiesel itself, biodiesel is also a hot spot in biofuel research today. There are generally the following methods to produce biodiesel: biodiesel (1) vegetable oil enzymatic method, that is, transesterification of waste edible oil with lipase to produce biodiesel. Recently, it was reported that the production efficiency was greatly improved and the service life of the enzyme was greatly prolonged by using immobilized enzyme technology and adding methanol in stages during the reaction. (2) Production of diesel oil by bagasse fermentation. (3) Control the level of oil accumulation, so that the acetyl-CoA carboxylase gene can be efficiently expressed in microalgae cells, thus producing diesel oil by cultivating microalgae. Hydrogen is another important energy source in 2 1 century. At present, hydrogen is mainly produced in petrochemical industry, but due to its high energy consumption, high cost and environmental pollution, the biological hydrogen production process has become a research hotspot. Biological hydrogen production mainly depends on photolysis of water from cyanobacteria and green algae or anaerobic fermentation, but the high cost of these processes and the difficulty in storage and transportation of hydrogen as energy make it too early to put hydrogen into practical use. Biological hydrogen production In addition, in the traditional petrochemical industry, it is not uncommon to report that microbial fermentation is applied to modern oil recovery technology to improve crude oil recovery, and it has been widely used in some oil fields, such as Shengli Oilfield. This also shows that even in the traditional petrochemical energy, there is a shadow of bioenergy production. Bioelectricity is a process of converting chemical energy in biomass into electric energy, which is mainly divided into traditional combustion power generation and biological battery. Traditional combustion power generation, as mentioned above, can be subdivided into two forms: biomass (1) generates steam by burning biomass in a boiler, and then generates electricity with steam; (2) Biomass gasification products are burned to generate electricity. Different from biological batteries, the process of making electricity is a process of directly converting chemical energy into electrical energy through biocatalysis under mild conditions. Traditional bio-power generation is to burn biomass in a boiler to generate high-density steam, and then the steam drives a turbine to generate electricity. Today, this technology has developed well, and a wide range of combustible materials can be used. However, due to its relatively low energy utilization rate and low operating efficiency (and their improvement potential is extremely limited in the long run) and high steam pressure (>: 1200atm), the further development of this technology is limited. Biogas gasification is a new method to obtain electricity from biomass. Biomass is not directly burned, but about 65%-70% of the energy contained in biomass is used in the process of first converting into combustible steam. The produced gas, like natural gas, can be used for power generation and automobile driving, and is widely used in industry. It can be said that this new technology has great development potential. There are two main power generation mechanisms of bio-batteries: (1) In the reactor, raw materials are converted into fuel products, such as H 2, which are oxidized in series power generation equipment, as shown in figure1a; Or combine microbial fermentation with electricity generation, and the metabolites of microorganisms directly transfer electrons with oxides (O _ 2 or H _ 2O _ 2) through the electron transfer medium on the electrode to generate electricity, as shown in figure1b. (2) utilize oxidoreductase immobilized on that electrode to oxidize and reduce specific fuel substance and oxidized substrates, thereby generating electricity. The basic principle of this process is shown in Figure 2. Because most oxidoreductases can't transfer electrons directly with conductive carriers, a series of electron transfer mediators have been developed. Recently, some new functional electrodes covering single or multi-layer biocatalysts have been reported. The combination of a single membrane electrode with biological activity not only ensures the biocatalysis rate, but also greatly accelerates the interface electron transfer rate and reduces the internal resistance of the battery, thus ensuring the development of miniaturization and stability of the biological battery. Small size, portability, high efficiency, stability and long life are the development directions of bio-batteries. Ideally, plug-in batteries can use natural fuel substances (such as glucose). ) to efficiently and continuously generate electric energy for medical diagnosis and other purposes, such as supporting the long-term normal operation of pacemakers and probes in the body. Advantages of electrode oxidoreductase With the increase of fossil energy prices, the utilization value of biomass energy is getting higher and higher. In addition to traditional firewood, straw and bagasse, high-yield plants specially used as fuel have also been successfully cultivated. As boiler fuel, replacing coal or oil with wood waste or plant fuel not only saves non-renewable fossil energy and energy consumption cost of enterprises, but also causes less pollution to the environment because wood waste contains almost no sulfur. It has the following advantages: biomass fuel (1) has a large calorific value, about 3900-4800 kcal/kg, and the calorific value after carbonization is as high as 7000-8000 kcal/kg. (2) Biomass fuel has high purity and does not contain other impurities that do not generate heat. Its carbon content is 75-85%, ash content is 3-6% and moisture content is 1-3%. (3) It absolutely does not contain impurities such as coal gangue and stones that do not generate heat but consume heat, which will directly reduce the cost for enterprises. (4) Biomass fuel does not contain sulfur and phosphorus, and does not corrode boilers, which can prolong the service life of boilers and benefit enterprises greatly. (5) Because biomass fuel does not contain sulfur and phosphorus, it does not produce sulfur dioxide and phosphorus pentoxide when burning, so it will not cause acid rain and pollute the atmosphere and environment. (6) Biomass fuel is clean and convenient to feed, which reduces the labor intensity of workers and greatly improves the working environment. Enterprises will reduce labor costs. (7) After the biomass fuel is burned, there is very little ash, which greatly reduces the cinder stacking area and reduces the slag discharge cost. (8) The ash from burning biomass fuel is a kind of high-grade and high-quality organic potash fertilizer, which can be recycled to create profits. (9) Biomass fuel is a renewable energy given by nature, and it is a deep-water bomb in response to the call of the central government to build a conservation-oriented society and industry to feed agriculture.