煤化學(xué)復(fù)習(xí)重點

1、Main points for coal chemistry. Blank-filling 1. Lignin and cellulose are considered to be the major organic precursors to coal although there is little evidence to support this theory. 2. The microscopic constituents of coals are called macerals. The macerals are actually identified microscopically

2、 by their form and reflectivity, and are divisible into three groups based appearance and physical characteristicsvitrinite, exinite, and inertinite are each further subdivided on the basis of individual maceral form. 3. The ashing technique is commonly to make a coal completely combusted at quite a

3、 high temperature by using a special devicea muffle furnace, then to weigh the residue, i.e., the ash, and to use the ash content as an indication to the minerals in the coal. 4.The proximate analysis of coal may be considered as the determination of the overall composition of a coal sample and is,

4、in reality, the determination of moisture content, volatile matter content, ash content, and (by difference) fixed carbon content. 5. Fixed carbon is a measure of the solid combustible material in coal after the expulsion of volatile matter; fixed carbon plus ash represent the approximate yield of c

5、oke from coal. The fixed carbon value is determined (ASTM D3172) by subtracting from 100 the resultant summation of moisture, volatile matter, and ash with all percentages on the same moisture reference base.6. The makeup of the organic portion of plants consists of carbohydrates, lignin, proteins a

6、nd lipoids. 7. Coal is a kind of sedimentary organic rock originating from ancient plant remains undergone complicatedly biochemical and physicochemical changes under certain climatic, biological, environmental and geological conditions.8. A piece of humic coal can be identified as bright coals (ant

7、hraxylon) or dull coals (attritus). The former have been further subdivided into vitrain and clarain while the later are subdivided into fusain and durain. Each of these lithotypes has individual characteristics that are easily distinguishable. 9. A variety of minerals have been reported to be prese

8、nt in coals，involving Clay minerals, Quartz minerals, Carbonate minerals, and Sulfur minerals. Mineral matter in coal can be evaluated by using ashing techniques, ash analysis and direct mineral analysis. 10. The two major sapropelitic coals are cannel coal and boghead coal ( the latter is also well

9、 known as torbanite). 11. The macerals are actually identified microscopically by their form and reflectivity，and are divisible into three groups based appearance and physical characteristics( Table 3-3). The three main groupsvitrinite (sometimes called huminite in subbitumious coals), exinite (some

10、times called liptinite), and inertinite are each further subdivided on the basis of individual maceral form. Explanation of terms of coal chemistry 1. Coal petrographyCoal petrography is, in essence, an investigation with subsequent identification of the macrostructures and microstructures that are

11、the physical structure of coal. 2. Ultimate analysis of coal Ultimate analysis is an absolute measure of the elemental composition of coal, expresses the composition of coal in percentages of carbon, hydrogen, nitrogen, sulfur, oxygen, and ash. 3. The calorific value of coal The calorific value of c

12、oal is a direct indication of the energy value of the coal and this particular property is considered to be one of the most important means by which a coal can be evaluated. 4. Ash technique to detect the ash content of coal This technique is commonly to make a coal completely combusted (燃燒) at quit

13、e a high temperature by using a special device (a muffle furnace), then to weigh (稱量) the residue (殘渣), i.e., the ash (灰分), and to use the ash content as an indication to the minerals in the coal. . Comprehensive understanding 1. Please briefly describe the coal forming process from the ancient high

14、er plant remains to the substance we know as coal today, according to the following schematic graph.PlantsPeatsapropelPeatification LignitesapropeliccoalBituminous AnthraciteStone-like coalDiagenisis/ lignificationMetamorphismcoalificationBituminizationanthracizationsaproficationDiagenisis or lignif

15、icationcoalificationCoal was formed from partially decomposed (已降解的，已腐爛的）(and subsequently (后來，隨后） metamorphosed (變質(zhì)，變形）) plant debris (碎片，殘?。?which collected in regions where waterlogged (浸滿水的，澇的） or swampy (沼澤的，濕地的） conditions prevailed (流行，盛行，占優(yōu)勢）. These conditions prevented complete decay (腐爛，降解

16、） of the debris as it accumulated and eventually(最后的） led to the material now as coal. In general terms, the debris consisted of trees, ferns（蕨類植物）, rushes （燈芯草，灌木）, lycopods （石松屬植物）, and several thousand plant species that have been identified in coal beds, but it appears that none of the species i

17、dentified in many different coals originated in brackish-water （鹽水） locales （區(qū)域）. Similar types of plant remains may be found in all types (ranks （煤階）) of coal， but, of course, the relative amounts （相對含量） vary considerably （相當(dāng)?shù)兀浅５兀? On this basis （由此）, it is not surprising that coal differs markedl

18、y （顯著地） in composition from one particular seam are not uncommon, due not only to the wide variety of plant debris that could have formed the precursors （母體，前體） but also to the many different chemical reactions that can occur during the maturation （成熟） process. Thus, once plant debris has accumulate

19、d under the “correct” conditions, the formation of peat（泥炭） gradually occurs （發(fā)生，出現(xiàn)）. Peat is not actually classified as coal but it is, nevertheless （仍然，不過）, believed to be that material which is formed as the initial step in the process. However, to become coal, peat must progress （前進，進展，經(jīng)歷） throu

20、gh what is loosely termed “coalification” （煤化作用） process. The coalification process is, in essence （本質(zhì)）, the progressive （漸進的，累進的） change in the plant debris as it becomes transformed from peat to lignite （褐煤） and then through the higher ranks （高階） of coal （such as subbituminous （次煙煤） and bituminous

21、 （煙煤） coals） to anthracite （無煙煤）. The degree of coalification generally determines the rank of the coal, but the process is not a series of straightforward （簡單的，直截了當(dāng)?shù)模?chemical changes. For example, the metamorphism （變質(zhì)作用） of the plant debris not only relies on （depend on） geological time （地質(zhì)年代） but

22、 also on temperature and pressure.Thus, when the organic debris (which may be identified as peat) is buried beneath （在之下） overburden （過載，重壓）, various physicochemical （物理化學(xué)的） processes occur as part of the metamorphosis （變質(zhì)，變形）. The major influences are believed to be the resulting （由此引起的） heat and p

23、ressure developed because of the overlying （上面堆垛的） sedimentary cover (overburden). This leads to changes in the constituents （成分，組成） of the debris such as an increase in the carbon content, alteration （改變） of the functional groups （官能團）, alteration of the various molecular structures ultimately （fin

24、ally） resulting in the loss of water , oxygen, and hydrogen with the increased resistance （阻力，阻抗，電阻） to solvents, heat, and oxidation. All theories about the formation of coal require that the original plant debris eliminate （去除，減少，消除） oxygen and hydrogen continuously under the prevailing （優(yōu)勢的） cond

25、itions, ultimately leading to a product containing approximately （大約） 90% w/w carbon, i. e., anthracite （無煙煤）. In order for the maturation （成熟） to proceed, chemical principles （原理，法則） require that oxidation reactions be completely inhibited （禁止）. However, in the early stages （早期階段） of calcification,

26、 microorganisms （微生物） may play an important role and, somewhat paradoxically （看似矛盾而實際地）, they may interact with the plant material under aerobic （需氧的） conditions as well as under anaerobic （厭氧的） conditions. However, in the early stages （早期階段） of calcification, microorganisms （微生物） may play an import

27、ant role and, somewhat paradoxically （看似矛盾而實際地）, they may interact with the plant material under aerobic （需氧的） conditions as well as under anaerobic （厭氧的） conditions. The formation of coal under the slow conditions generally referred to （指的是） as geological time （地質(zhì)時期） may , nevertheless （不過，仍然）, be

28、regarded as （被認為是） occurring in the absence of （缺少的） oxygen, thereby （因此） promoting （促進，提高，提升） the formation of highly carbonaceous （碳質(zhì)的，高碳的） molecules through losses of oxygen and hydrogen from the original organic molecules. 2. Please briefly describe Two-phase structural model of coal. The organi

29、c matter of coal is composed of two relevant phases: macromolecular and micromolecular phases. three-dimensional net of macromolecular skeletons Coal is not composed of any unitary structure, rather, three-dimensional skeleton network of aromatic rings (macromolecular phase) and some small molecular

30、 compounds (micromolecular matters), among which the small molecules interact with the macromolecules and be fixed on the skeletons, or interacted themselves to form larger clusters and then be trapped inside the skeletons. Complex intermolecular actions occur between two phases in coal. Coal organi

31、c matters are rich in aromatic ring structures (and always aliphatic rings as well). Coal macromolecules take these rings as structural units, and are polymerized by linkages of (CH2)n、O and S . The size and condensation degree of aromatic ring unit in coal increase with metamorphic grade of coal, w

32、hile the number of linkages reduce. The small molecular phase of coal is also quite a complex organic system, and aliphatic, alicyclic and aromatic hydrocarbons as well as heteroaromatics and other polar compounds are involved.3. Please briefly describe the main changes of coal decomposition along w

33、ith different temperature stages. （Totally 15）Below 100- the formation of low molecular weight species: water absorbed methane and carbon dioxide 100-200- more than 50% of the carboxylic acid functions can lose carbon dioxide 200-370- coals lose a variety of lower molecular weight organic species (m

34、ay aliphatic compounds, and some of the aromatic species ) which are believed to arise from moieties that are “l(fā)oosely bound” to the more thermally stable part of the coal structure. proper 350- cracking temperature 370; 700- methane (indicative of the thermal destruction of the coal structure), pol

35、ycyclic aromatics, phenols, and nitrogen compounds are produced.For bituminous coals, the decomposition increases markedly above 400 and reaches a maximum in the range 700-900Please briefly describe Products from coal pyrolysis.Combustible Gases: hydrogen, methane, and carbon monoxide as well as les

36、ser amounts of hydrocarbonsTarry products: small molecular volatile matters such as hydrocarbons, aromatics and their derivatives Coke: char residue which consists of carbon and mineral matter 4. Please briefly describe coal pyrolysis and the main products of coal pyrolysis. The pyrolysis of coal is

37、 generally defined as the widespread thermal decomposition of coal in the absence of air or other added substances. The thermal decomposition of coal on a commercial scale is often more commonly referred to as carbonization and is more usually achieved by the use of temperatures up to 1500. The rapi

38、d heating of coal in an inert atmosphere is referred to as flash pyrolysis whereas in a hydrogencontaining atmosphere the process becomes flash hydropyrolysis. Combustible Gases: hydrogen, methane, and carbon monoxide as well as lesser amounts of hydrocarbonsTarry products: small molecular volatile

39、matters such as hydrocarbons, aromatics and their derivatives Coke: char residue which consists of carbon and mineral matter 5. Precursors of coalThe makeup of the organic portion of plants consists of carbohydrates, lignin, proteins and lipoids. The constituents （組成，組分） of the organic portion of th

40、e original plants, which ultimately （最終，最后） transformed （轉(zhuǎn)化） into coal, has great influence on （對有極大影響） the finished coal structure and its composition. So it is necessary to make complete understanding of the constituents of the organic portion of plants. Lignin （木質(zhì)素） and cellulose （纖維素） are consid

41、ered to be the major organic precursors （母體） to coal All the organic constituents in plants, which not soluble in the organic solvents such as ethers, benzene, chloroform, etc., fall within lipoid. They are: Oils and fats; Waxes; Resins; Cutins, Seberins, sporins.Proteins are believed to be the main

42、 contributors of the organic nitrogen-containing comounds.Carbohydrate，namely saccharide or sugar, is quite a broad type of constituents of plant, and was believed to have made a lot of contribution to coal formation. . Talks1. Talk about Coal reserves in the world and China Coal is the most abundan

43、t fossil fuel in the world. Coal reserves are also more widely distributed throughout the world. Main countries of coal: China, the U.S.A., Russia, India, AustraliaChina contains more than 126,000 million short tons of recoverable coal reserves, third behind only the United States and Russia. These

44、recoverable reserves are nearly equally divided between hard coal and lignite deposits (i.e., 68,500 and 57,700 million short tons, respectively). Coalfields are scattered throughout China： with the largest deposits being found in western China, stretching from north to south with most of the reserv

45、es in the northern part, specifically in the Inner Mongolia, Shanxi, and Shaanxi provinces. Significant anthracite deposits are found in the Shanxi and Guizhou provinces. Bituminous coal deposits occur in the Heilongjiang, Shanxi, Jiangxi, Shandong, Henan, Anhui, and Guizhou provinces. China is the

46、worlds largest coal producer; most of the coal is used internally for industry and electricity generation. The hard-coal rank appears to increase slightly northward from the Yangtze River, while locally seam quality is very variable。2. Talk about Coal reserves in China Coal is the most abundant foss

47、il fuel in the world. Coal reserves are also more widely distributed throughout the world. Main countries of coal: China, the U.S.A., Russia, India, AustraliaChina contains more than 126,000 million short tons of recoverable coal reserves, third behind only the United States and Russia. These recove

48、rable reserves are nearly equally divided between hard coal and lignite deposits (i.e., 68,500 and 57,700 million short tons, respectively). Coalfields are scattered throughout China： with the largest deposits being found in western China, stretching from north to south with most of the reserves in

49、the northern part, specifically in the Inner Mongolia, Shanxi, and Shaanxi provinces. Significant anthracite deposits are found in the Shanxi and Guizhou provinces. Bituminous coal deposits occur in the Heilongjiang, Shanxi, Jiangxi, Shandong, Henan, Anhui, and Guizhou provinces. China is the worlds largest coal producer; most of the coal is used internally for industry and electricity generation. The hard-coal rank appears to increase slightly northward fro