elemental impurities_

1.天然气 轻烃储运的资料

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1

2 ?

3

4?

5?

AHCl?HF?

B ?HNO3

CH2S?H2S

D

6

Manufacture

Main article: Contact process

Sulfuric acid is produced from sulfur, oxygen and water via the contact process.

In the first step, sulfur is burned to produce sulfur dioxide.

(1) S(s) + O2(g) ? SO2(g)

This is then oxidised to sulfur trioxide using oxygen in the presence of a vanadium(V) oxide catalyst.

(2) 2 SO2 + O2(g) ? 2 SO3(g) (in presence of V2O5)

Finally the sulfur trioxide is treated with water (usually as -98% H2SO4 containing 2-3% water) to produce 98-99% sulfuric acid.

(3) SO3(g) + H2O(l) ? H2SO4(l)

Note that directly dissolving SO3 in water is impractical due to the highly exothermic nature of the reaction. Mists are formed instead of a liquid. Alternatively, SO3 can be absorbed into H2SO4 to produce oleum (H2S2O7), which may then be mixed with water to form sulfuric acid.

(3) H2SO4(l) + SO3 ? H2S2O7(l)

Oleum is reacted with water to form concentrated H2SO4.

(4) H2S2O7(l) + H2O(l) ? 2 H2SO4(l)

In 1993, American production of sulfuric acid amounted to 36.4 million tonnes. World production in 2001 was 165 million tonnes.

[edit]Physical properties

[edit]Forms of sulfuric acid

Although nearly 100% sulfuric acid can be made, this loses SO3 at the boiling point to produce 98.3% acid. The 98% grade is more stable in storage, and is the usual form of what is described as concentrated sulfuric acid. Other concentrations are used for different purposes. Some common concentrations are

10%, dilute sulfuric acid for laboratory use,

33.5%, battery acid (used in lead-acid batteries),

62.18%, chamber or fertilizer acid,

77.67%, tower or Glover acid,

98%, concentrated acid.

Different purities are also ailable. Technical grade H2SO4 is impure and often colored, but is suitable for making fertilizer. Pure grades such as US Pharmacopoeia (USP) grade are used for making pharmaceuticals and dyestuffs.

When high concentrations of SO3(g) are added to sulfuric acid, H2S2O7, called pyrosulfuric acid, fuming sulfuric acid or oleum or, less commonly, Nordhausen acid, is formed. Concentrations of oleum are either expressed in terms of% SO3 (called% oleum) or as% H2SO4 (the amount made if H2O were added); common concentrations are 40% oleum (109% H2SO4) and 65% oleum (114.6% H2SO4). Pure H2S2O7 is a solid with melting point 36?C.

[edit]Polarity and conductivity

Anhydrous H2SO4 is a very polar liquid, hing a dielectric constant of around 100. This is because it can dissociate by protonating itself, a process known as autoprotolysis.[2] It occurs to a high degree in sulfuric acid, more than 10 billion times the level seen in water: [citation needed]

2 H2SO4? H3SO4+ + HSO4?

This allows protons to be highly mobile in H2SO4. It also makes sulfuric acid an excellent solvent for many reactions. In fact, the equilibrium is more complex than shown above. 100% H2SO4 contains the following species at equilibrium (figures shown as mol per kg solvent): HSO4? (15.0), H3SO4+ (11.3), H3O+ (8.0), HS2O7? (4.4), H2S2O7 (3.6), H2O (0.1).

[edit]Chemical properties

[edit]Reaction with water

The hydration reaction of sulfuric acid is highly exothermic. If water is added to the concentrated sulfuric acid, it can boil and spit dangerously. One should always add the acid to the water rather than the water to the acid. This can be remembered through mnemonics such as: "Always do things as you oughta, add the acid to the water. If you think your life's too placid, add the water to the acid", "A.A.: Add Acid", or "Drop acid, not water", or "Acid to water, like A&W Root Beer" or "Put the king into the water, not the water into the king" . The necessity for this safety precaution is due to the relative densities of these two liquids. Water is less dense than sulfuric acid, meaning water will tend to float on top of this acid. The reaction is best thought of as forming hydronium ions, by

H2SO4 + H2O ? H3O+ + HSO4-,

and then

HSO4- + H2O ? H3O+ + SO42-.

Because the hydration of sulfuric acid is thermodynamically forable, sulfuric acid is an excellent dehydrating agent, and is used to prepare many dried fruits. The affinity of sulfuric acid for water is sufficiently strong that it will remove hydrogen and oxygen atoms from other compounds; for example, mixing starch (C6H12O6)n and concentrated sulfuric acid will give elemental carbon and water which is absorbed by the sulfuric acid (which becomes slightly diluted): (C6H12O6)n ? 6C + 6H2O. The effect of this can be seen when concentrated sulfuric acid is spilled on paper; the starch reacts to give a burned earance, the carbon ears much as soot would in a fire. A more dramatic reaction occurs when sulfuric acid is added to a tablespoon of white sugar; a rigid column of black, porous carbon will quickly emerge. The carbon will smell strongly of caramel.

[edit]Other reactions of sulfuric acid

As an acid, sulfuric acid reacts with most bases to give the corresponding sulfate. For example, copper(II) sulfate. This blue salt of copper, commonly used for electroplating and as a fungicide, is prepared by the reaction of copper(II) oxide with sulfuric acid:

CuO + H2SO4 ? CuSO4 + H2O

Sulfuric acid can also be used to displace weaker acids from their salts. Reaction with sodium acetate, for example, displaces acetic acid:

H2SO4 + CH3COONa ? NaHSO4 + CH3COOH

Similarly, reacting sulfuric acid with potassium nitrate can be used to produce nitric acid and a precipitate of potassium bisulfate. When combined with nitric acid, sulfuric acid acts both as an acid and a dehydrating agent, forming the nitronium ion NO2+, which is important in nitration reactions involving electrophilic aromatic substitution. This type of reaction, where protonation occurs on an oxygen atom, is important in many organic chemistry reactions, such as Fischer esterification and dehydration of alcohols.

Sulfuric acid reacts with most metals via a single displacement reaction to produce hydrogen gas and the metal sulfate. Dilute H2SO4 attacks iron, aluminium, zinc, manganese, magnesium and nickel, but reactions with tin and copper require the acid to be hot and concentrated. Lead and tungsten, however, are resistant to sulfuric acid. The reaction with iron (shown) is typical for most of these metals, but the reaction with tin is unusual in that it produces sulfur dioxide rather than hydrogen.

Fe(s) + H2SO4(aq) ? H2(g) + FeSO4(aq)

Sn(s) + 2 H2SO4(aq) ? SnSO4(aq) + 2 H2O(l) + SO2(g)

[edit]Environmental aspects

Sulfuric acid is a constituent of acid rain, which is formed by atmospheric oxidation of sulfur dioxide in the presence of water - i.e. oxidation of sulfurous acid. Sulfur dioxide is the main byproduct produced when sulfur-containing fuels such as coal or oil are burned.

Sulfuric acid is formed naturally by the oxidation of sulphide minerals, such as iron sulfide. The resulting water can be highly acidic and is called Acid Rock Drainage (ARD). This acidic water is capable of dissolving metals present in sulfide ores, which results in brightly-colored, toxic streams. The oxidation of iron sulfide pyrite by molecular oxygen produces iron(II), or Fe2+:

FeS2 + 7/2 O2 + H2O ? Fe2+ + 2 SO42- + 2 H+.

The Fe2+ can be further oxidized to Fe3+, according to:

Fe2+ + 1/4 O2 + H+ ? Fe3+ + 1/2 H2O,

and the Fe3+ produced can be precipitated as the hydroxide or hydrous oxide. The equation for the formation of the hydroxide is

Fe3+ + 3 H2O ? Fe(OH)3 + 3 H+.

The iron(III) ion ("ferric iron", in casual nomenclature) can also oxidize pyrite. When iron(III) oxidation of pyrite occurs, the process can become rapid. pH values below zero he been measured in ARD produced by this process.

ARD can also produce sulfuric acid at a slower rate, so that the Acid Neutralization Capacity (ANC) of the aquifer can neutralize the produced acid. In such cases, the Total Dissolved solids (TDS) concentration of the water can be increased form the dissolution of minerals from the acid-neutralization reaction with the minerals.

[edit]Extraterrestrial sulfuric acid

Sulfuric acid is produced in the upper atmosphere of Venus by the sun's photochemical action on carbon dioxide, sulfur dioxide, and water vapor. Ultriolet photons of welengths less than 169 nm can photodissociate carbon dioxide into carbon monoxide and atomic oxygen. Atomic oxygen is highly reactive. When it reacts with sulfur dioxide, a trace component of the Venerian atmosphere, the result is sulfur trioxide, which can combine with water vapor, another trace component of Venus' atmosphere, to yield sulfuric acid.

CO2 ? CO + O

SO2 + O ? SO3

SO3 + H2O ? H2SO4

In the upper, cooler portions of Venus's atmosphere, sulfuric acid exists as a liquid, and thick sulfuric acid clouds completely obscure the planet's surface when viewed from above. The main cloud layer extends from 45?70 km above the planet's surface, with thinner hazes extending as low as 30 and as high as 90 km above the surface.

Infrared spectra from NASA's Galileo mission show distinct absorptions on Jupiter's moon Europa that he been attributed to one or more sulfuric acid hydrates. The interpretation of the spectra is somewhat controversial. Some planetary scientists prefer to assign the spectral features to the sulfate ion, perhaps as part of one or more minerals on Europa's surface.

[edit]History of sulfuric acid

John Dalton's 1808 sulfuric acid molecule shown a central sulfur atom bonded to three oxygen atoms.The discovery of sulfuric acid is credited to 8th century alchemist Jabir ibn Hayyan. The acid was later studied by 9th century physician and alchemist Ibn Zakariya al-Razi (Rhases), who oained the substance by dry distillation of minerals including iron(II) sulfate heptahydrate, FeSO4 ? 7H2O, and copper(II) sulfate pentahydrate, CuSO4 ? 5H2O. When heated, these compounds decompose to iron(II) oxide and copper(II) oxide, respectively, giving off water and sulfur trioxide, which combine to produce a dilute solution of sulfuric acid. This method was popularized in Europe through translations of Arabic and Persian treatises, as well as books by European alchemists, such as the 13th-century German Albertus Magnus.

Sulfuric acid was known to medieval European alchemists as oil of vitriol, spirit of vitriol, or simply vitriol, among other names. The word vitriol derives from the Latin vitreus, 'glass', referring to the glassy earance of the sulfate salts, which also carried the name vitriol. Salts called by this name included copper(II) sulfate (blue vitriol, or rarely Roman vitriol), zinc sulfate (white vitriol), iron(II) sulfate (green vitriol), iron(III) sulfate (vitriol of Mars), and cobalt(II) sulfate (red vitriol).

Vitriol was widely considered the most important alchemical substance, intended to be used as a philosopher's stone. Highly purified vitriol was used as a medium for reacting other substances. This was largely because the acid does not react with gold, production of which was often the final goal of alchemical processes. The importance of vitriol to alchemy is highlighted in the alchemical motto, Visita Interiora Terrae Rectificando Invenies Occultum Lapidem which is a backronym meaning ('Visit the interior of the earth and rectifying (i.e. purifying) you will find the hidden/secret stone'), found in L\'Azoth des Philosophes by the 15th Century alchemist Basilius Valentinus, .

In the 17th century, the German-Dutch chemist Johann Glauber prepared sulfuric acid by burning sulfur together with saltpeter (potassium nitrate, KNO3), in the presence of steam. As saltpeter decomposes, it oxidizes the sulfur to SO3, which combines with water to produce sulfuric acid. In 1736, Joshua Ward, a London pharmacist, used this method to begin the first large-scale production of sulfuric acid.

In 1746 in Birmingham, John Roebuck adapted this method to produce sulfuric acid in lead-lined chambers, which were stronger, less expensive, and could be made larger than the previously used glass containers. This lead chamber process allowed the effective industrialization of sulfuric acid production. After several refinements, this method remained the standard for sulfuric acid production for almost two centuries.

Sulfuric acid created by John Roebuck's process only roached a 35?40% concentration. Later refinements to the lead-chamber process by French chemist Joseph-Louis Gay-Lussac and British chemist John Glover improved the yield to 78%. However, the manufacture of some dyes and other chemical processes require a more concentrated product. Throughout the 18th century, this could only be made by dry distilling minerals in a technique similar to the original alchemical processes. Pyrite (iron disulfide, FeS2) was heated in air to yield iron (II) sulfate, FeSO4, which was oxidized by further heating in air to form iron(III) sulfate, Fe2(SO4)3, which, when heated to 480 ?C, decomposed to iron(III) oxide and sulfur trioxide, which could be passed through water to yield sulfuric acid in any concentration. However, the expense of this process prevented the large-scale use of concentrated sulfuric acid.

In 1831, British vinegar merchant Peregrine Phillips patented the contact process, which was a far more economical process for producing sulfur trioxide and concentrated sulfuric acid. Today, nearly all of the world's sulfuric acid is produced using this method.

[edit]Uses

Sulphuric acid production in 2000Sulfuric acid is a very important commodity chemical, and indeed, a nation's sulfuric acid production is a good indicator of its industrial strength.[3] The major use (60% of total production worldwide) for sulfuric acid is in the "wet method" for the production of phosphoric acid, used for manufacture of phosphate fertilizers as well as trisodium phosphate for detergents. In this method, phosphate rock is used, and more than 100 million tonnes are processed annually. This raw material is shown below as fluorapatite, though the exact composition may vary. This is treated with 93% sulfuric acid to produce calcium sulfate, hydrogen fluoride (HF) and phosphoric acid. The HF is removed as hydrofluoric acid. The overall process can be represented as:

Ca5F(PO4)3 + 5 H2SO4 + 10 H2O ? 5 CaSO4?2 H2O + HF + 3 H3PO4.

Sulfuric acid is used in large quantities by the iron and steelmaking industry to remove oxidation, rust and scale from rolled sheet and billets prior to sale to the automobile and white-goods industry. Used acid is often recycled using a Spent Acid Regeneration (SAR) plant. These plants combust spent acid with natural gas, refinery gas, fuel oil or other fuel sources. This combustion process produces gaseous sulfur dioxide (SO2) and sulfur trioxide (SO3) which are then used to manufacture "new" sulfuric acid. SAR plants are common additions to metal smelting plants, oil refineries, and other industries where sulfuric acid is consumed in bulk, as operating a SAR plant is much cheaper than the recurring costs of spent acid disposal and new acid purchases.

Ammonium sulfate, an important nitrogen fertilizer, is most commonly produced as a byproduct from coking plants supplying the iron and steel making plants. Reacting the ammonia produced in the thermal decomposition of coal with waste sulfuric acid allows the ammonia to be crystallized out as a salt (often brown because of iron contamination) and sold into the agro-chemicals industry.

Another important use for sulfuric acid is for the manufacture of aluminum sulfate, also known as paper maker's alum. This can react with small amounts of soap on paper pulp fibers to give gelatinous aluminum carboxylates, which help to coagulate the pulp fibers into a hard paper surface. It is also used for making aluminum hydroxide, which is used at water treatment plants to filter out impurities, as well as to improve the taste of the water. Aluminum sulfate is made by reacting bauxite with sulfuric acid:

Al2O3 + 3 H2SO4 ? Al2(SO4)3 + 3 H2O.

Sulfuric acid is used for a variety of other purposes in the chemical industry. For example, it is the usual acid catalyst for the conversion of cyclohexanoneoxime to caprolactam, used for making nylon. It is used for making hydrochloric acid from salt via the Mannheim process. Much H2SO4 is used in petroleum refining, for example as a catalyst for the reaction of isobutane with isobutylene to give isooctane, a compound that raises the octane rating of gasoline (petrol). Sulfuric acid is also important in the manufacture of dyestuffs solutions and is the "acid" in lead-acid (car) batteries.

Sulfuric acid is also used as a general dehydrating agent in its concentrated form. See Reaction with water.

[edit]Sulfur-iodine cycle

The sulfur-iodine cycle is a series of thermo-chemical processes used to oain hydrogen. It consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen.

2 H2SO4 ? 2 SO2 + 2 H2O + O2 (830?C)

I2 + SO2 + 2 H2O ? 2 HI + H2SO4 (120?C)

2 HI ? I2 + H2 (320?C)

The sulfur and iodine compounds are recovered and reused, hence the consideration of the process as a cycle. This process is endothermic and must occur at high temperatures, so energy in the form of heat has to be supplied.

The sulfur-iodine cycle has been proposed as a way to supply hydrogen for a hydrogen-based economy. It does not require hydrocarbons like current methods of steam reforming.

The sulfur-iodine cycle is currently being researched as a feasible method of oaining hydrogen, but the concentrated, corrosive acid at high temperatures poses currently insurmountable safety hazards if the process were built on large-scale.

Wikipedia

天然气 轻烃储运的资料

摘 要 运用 X 射线衍射分析( XRD) 、带能谱仪的扫描电镜( SEM-EDX) 和光学显微镜等技术，首次在鄂尔多斯盆地东北缘准格尔矿区6 号巨厚煤层中发现了超常富集的勃姆石及其特殊的矿物组合，勃姆石含量可高达13. 1%，与勃姆石伴生的矿物有磷锶铝石、锆石、金红石、菱铁矿、方铅矿、硒铅矿和硒方铅矿。重矿物的组合特征与华北地区本溪组铝土矿中的重矿物组合特征相似，高含量的勃姆石主要来源于聚煤盆地北偏东方向本溪组风化壳铝土矿，三水铝石以胶体溶液的形式从铝土矿中被短距离带入泥炭沼泽中，在泥炭聚积阶段和成岩作用早期经压实作用脱水凝聚而形成勃姆石。

任德贻煤岩学和煤地球化学论文选辑

煤中矿物是煤的重要组成部分。从成因角度来看，煤中矿物的成分和特征，既反映聚煤环境的地质背景，有时又反映煤层形成后所经历的各种地质作用过程，有助于阐明煤层的成因、煤化作用、区域地质历史演化等基本理论问题( Ward，2002) 。从煤的利用角度看，煤中矿物含量直接影响煤发热量的高低和煤的加工利用特性( 韩德馨，1996) ，也是在炼焦冶金过程中造成磨损、腐蚀、污染的主要来源。另外，煤中大部分微量有害元素的含量、存在形式及其对环境的污染也与煤中矿物有关( Vassilev et al. ，1994) ，矿物是煤中微量元素的主要载体( 唐修义等，2004) 。Gupta 等( 1999) 认为，煤利用过程中大部分问题是煤中矿物引起的，而不是煤中的有机显微组分。另一方面，煤中所富集的达到工业品位要求的稀有元素、放射性元素是伴生的有用矿产，有的矿物在煤炭利用加工过程中能起催化作用，提高了煤的经济技术价值。因此，对煤中矿物的成分、含量、成因和赋存状态的研究，具有重要的理论和现实意义。

一、煤中发现的矿物

煤中矿物主要有石英、黏土矿物( 主要是高岭石、伊利石、伊利石/蒙脱石混层矿物) 、碳酸盐矿物( 菱铁矿、方解石、白云石) 、硫化物矿物( 如黄铁矿) ( Ward，18，2002; Harvey et al. ，1986; Palmer et al. ，1996) 。国内外学者对煤中矿物，特别是这 4 大类矿物的赋存特征和地质成因进行了较为广泛的研究( Martinez-Tarazona et al. ，1992; Patterson et al. ，1994; 黄文辉等，1999; Hower et al. ，2001; Ward，2002; Dai et al. ，2003) ，并运用低温灰化、X 射线衍射、带能谱仪的扫描电镜等方法发现了煤中许多痕量矿物，如独居石、锆石、纤磷钙铝石、水绿矾、胶磷矿、铬铅矿等( Querol et al. ，19; Rao et al. ，19; Ward，1989; Dill et al. ，1999; Vassilevet al. ，1998; Li et al. ，2001; 丁振华等，2002) 。根据 Finkelman( 1981) 的资料，煤中已鉴定出的矿物达 125 种以上; Bou?ka 等( 2000) 认为煤中可能存在 145 种矿物; 唐修义等( 2004) 汇总了国内外文献报道，列出了煤中可以鉴定出的 201 种晶体矿物。

根据前人的研究资料，煤中发现的氢氧化物矿物有: 褐铁矿、铝土矿、针铁矿、纤铁矿、硬水铝石、三水铝石、勃姆石、黑锌锰矿、水镁石，羟钙石。其中褐铁矿、铝土矿、针铁矿在煤中常见，对其成因也有较多的研究( Dill et al. ，1999) ; 纤铁矿在煤中较少见，主要存在于泥炭中( Bou?ka et al. ，19) ; 硬水铝石在煤中含量较低，主要存在于有火山灰层夹矸的煤层中，且主要在火山灰层夹矸中( Burger et al. ，11) ; 三水铝石在煤中少见( Bou?ka et al. ，2000) ; 勃姆石、黑锌锰矿、水镁石和羟钙石等矿物在煤中偶见或罕见( Ward，18; Bou?ka etal. ，2000; 唐修义等，2004) 。

值得关注的是，虽然勃姆石可以存在于某些煤系地层的黏土岩夹矸中，并对其进行了一些研究工作( Maoyuan et al. ，1994; 梁绍暹等，19; 刘钦甫等，19) ，但是对煤中勃姆石的赋存、成因在国内外尚未见公开报道的资料，其主要原因就是它在煤中较为罕见。Bou?ka等( 2000) 认为勃姆石在煤中是非常稀少的; Ward( 17，，2002) 认为在个别煤中可以存在痕量的勃姆石，但高含量的勃姆石在煤中是非同寻常的。Goodarzi 等( 1985) 、Harvey 等( 1986) 、Patterson 等( 1994) 、Vassilev( 1994) 等分别对加拿大、澳大利亚、美国、保加利亚的煤中矿物进行了研究，未发现勃姆石。Tatsuo 等( 1993，1996) ，Tatsuo( 1998) 在日本北海道的石狩湾煤田古近纪煤的低温灰化产物中发现了含量很少的勃姆石( 在所集的 85 个煤样品中，仅 8 个样品的低温灰化产物中有勃姆石，并且其最高含量仅占低温灰化产物中矿物总量的 2. 5%) 。除此之外，国内外对煤中勃姆石的研究再无公开报道。

二、地质背景和实验方法

准格尔煤田地处鄂尔多斯盆地的东北缘，煤田南北长 65km，东西宽 26km，面积1700km2，已探明的煤炭地质储量为 268 亿吨。它是鄂尔多斯盆地煤层最富集的地带，也是沉积相变最明显的地带，石灰岩在煤田内全部尖灭，逐渐相变为陆源碎屑岩。准格尔煤田的含煤岩系包括上石炭统本溪组、太原组和下二叠统山西组，含煤岩系总厚 110 ～160 m，煤系地层的底板为中奥陶统石灰岩，其上覆地层为下石盒子组、上石盒子组、石千峰组、刘家沟组等非含煤地层。该区主煤层6 号煤位于太原组的顶部，厚度一般在2. 7 ～35 m 之间，平均厚度为 30m，最厚可达 50 m，是在三角洲沉积体系的背景下形成的一巨厚煤层( 刘钦甫等，19) 。

按照 GB 482-1995 和 MT 262-91 的样规范和矿区煤层开的实际情况，对准格尔矿区黑岱沟矿6 号煤层煤样进行了分层样品的集。样品的编号、厚度及特征如图 1 所示。煤层自上而下的编号为 ZG6-1、ZG6-2、ZG6-3、ZG6-4、ZG6-5、ZG6-6 和 ZG6-7。用 X 射线衍射分析( XRD) 对该煤层进行了矿物组成研究，用带能谱仪的扫描电镜( SEM-EDX) 和 MPV-Ⅲ显微镜光度计对矿物的形貌特征进行观察。按照 GB 8899-88 对煤的显微组分和矿物进行了定量统计，测试结果的单位为体积百分数( vol. %) ，两次测试结果的允许差小于4. 5% 。

图 1 研究区 6 号煤层柱状及分层矿物组成

三、勃姆石及其特殊矿物组合的发现和赋存特征

在矿物组成上，准格尔 6 号煤层 d 剖面自上而下明显分成 4 段，第 1 段由 ZG6-1 组成，第 2 段由 ZG6-2、ZG6-3 和 ZG6-4 组成，第 3 段由 ZG6-5 组成，第 4 段由 ZG6-6 和 ZG6-7 组成。这 4 段的矿物组成有很大差别( 图 1) 。自上而下的特征如下:

( 1) X 射线衍射分析( 图 2a) 和光学显微镜下测定 ZG6-1 分层的矿物组成以石英为主，含量高达 16. 4%( 表 1) ，呈分散状( 图版Ⅰ-1) ，石英造成煤的矿化现象比较严重( 图版Ⅰ-2) 。从石英形态特征来看，其边缘棱角明显，粒度均匀，大多为 5 ～ 10μm ( 图版Ⅰ-3) ，主要分布在基质镜质体中，也存在于同生黏土矿物中，在均质镜质体中也有分布。黏土矿物( 主要是高岭石) 的含量为5. 5%( 表1) 。该分层的石英和黏土矿物的 SEM-EDX 测试结果如表2 所示。

表 1 准格尔煤田 6 煤层的煤岩组成

注: bdl 为低于检测极限。

图 2 研究区 6 号煤层分层样品的 XRD 图

( 2) ZG6-2、ZG6-3、ZG6-4 的组成以超常富集的勃姆石为主，其含量分别为 11. 9% 、13. 1% 和 11% ( 图 2b、c、d; 表 1) ，如此高含量的勃姆石存在于煤中，在国内外尚无报道。另外，这 3 个分层中高岭石含量分别为 4. 3%、3. 6%和 4. 4%。勃姆石在该煤层中呈隐晶状产出，其赋存状态多样，但主要以团块状分布于基质镜质体中，有的以单独的团块状或不规则的团块状出现( 图版Ⅰ-4 ～6) ，有的以连续的团块状或串珠状出现，也有的充填在成煤植物的胞腔中( 图版Ⅰ-7) 。呈团块状分布的勃姆石的粒度差别很大，为 1 ～ 300μm。在偏光显微镜下，勃姆石与黏土矿物的区别主要是: 勃姆石致密，而黏土矿物比较松散( 图版Ⅰ-8) ，勃姆石的反射色比黏土矿物浅，并且勃姆石的突起较高( 图版Ⅰ-6) ，黏土矿物不显突起( 图版Ⅰ-8) 。在这些勃姆石富集的煤层中，与勃姆石伴生的矿物组合也较特殊，这些矿物包括金红石、磷锶铝石、锆石、菱铁矿、方铅矿、硒铅矿和硒方铅矿。在 ZG6-2 中，有较高含量的金红石( 1. 6%) ，金红石以单晶或膝状双晶形式出现，并有环带结构的现象( 图版Ⅱ-1，2) 。在ZG6-2 和 ZG6-3 中有磷锶铝石，磷锶铝石主要充填在丝质体的胞腔中，呈圆粒状出现，粒度为1 ～2μm( 图版Ⅰ-7，图版Ⅱ-3) 。在 ZG6-3 中有方铅矿、硒铅矿和硒方铅矿，这3 种矿物呈浑圆状产出( 图版Ⅱ-4) ，其内部结构比较特殊，有许多孔洞，似明显的菌藻类等低等生物矿化的迹象( 图版Ⅱ-5) 。在 ZG6-2 和 ZG6-3 中，有锆石，其破碎的痕迹表明来源于物源区( 图版Ⅱ-6，7) 。此外，在勃姆石富集的层位还有少量的菱铁矿( 图版Ⅱ-8) 。由于金红石、磷锶铝石、锆石和菱铁矿的含量不高，X 射线衍射分析未能检测出，主要是通过偏光显微镜和带能谱仪的扫描电镜( SEM-EDX) 所观察的晶体形态和物质成分加以鉴定。

( 3) ZG6-5 的矿物组成以高岭石为主，含量为 11. 4% ，含少量勃姆石( 3. 3% ) 及痕量的黄铁矿。

( 4) ZG6-6 和 ZG6-7 的矿物以高岭石为主，含量分别为 22% 和 19. 5% ，有痕量的黄铁矿、石英和方解石，未见勃姆石( 图 2e、f) 。

四、勃姆石及其伴生矿物成因初探

勃姆石是硅酸盐岩石的风化产物，常与三水铝石、硬水铝石、高岭石、迪开石、玉髓、铵云母等矿物共生，此外，还可能是低温热液产物，与泡沸石共生( Kondakov et al. ，15; Hrinko，1986; 梁绍暹等，19; Banerji，1998; 程东等，2001) 。但在勃姆石富集的煤层中，除高岭石外，没有发现上述共生矿物，也没有发现任何低温热液矿物或热液活动的证据。

根据王双明等( 1996) 的研究表明，在准格尔煤田 6 号煤层的形成初期( 对应的煤层编号为 ZG6-7 和 ZG6-6) ，准格尔煤田北偏西方向地势高，而南偏东地势低，陆源碎屑物质主要来自北西方向的阴山古陆广泛分布的中元古代钾长花岗岩，因此在 ZG6-7 和 ZG6-6 分层中所形成的矿物和鄂尔多斯盆地其他地区煤的矿物组成差别不大，以陆缘碎屑的黏土矿物为主。在煤层形成的中期( 相对应的煤层编号为 ZG6-5、ZG6-4、ZG6-3 和 ZG6-2) ，煤田的北东部开始隆起，并有本溪组铝土矿出露，煤田处于北偏西的阴山古陆和北偏东本溪组隆起的低洼地区，聚煤作用持续进行，古河流的方向为北偏东( 王双明等，1996) ，表明陆源碎屑主要来自北偏东的隆起。根据石炭纪石灰岩氧、碳同位素值代表的环境意义，得出石炭纪石灰岩是在正常海相环境中形成的，并计算出太原组形成期古水温平均为 29 ～ 32℃，说明当时该地区气候为炎热( 刘焕杰等，1991; 程东等，2001) 。根据林万智( ) 和程东等( 2001) 对该区石炭纪古地磁研究推测，准格尔煤田晚石炭世的古纬度在北纬 14°左右。这种热带湿热气候有利于本溪组风化壳三水铝石的形成( 程东等，2001) 。三水铝石为氧化的开放环境的产物。三水铝石以及少量的黏土矿物在水流的作用下，以胶体的形式经过短距离的搬运到准格尔泥炭沼泽中。根据王双明等( 1996) 的研究，准格尔煤田距离风化壳仅为50km 左右。随着泥炭的持续聚积，到对应的煤层为 ZG6-1 时，北偏东方向的本溪组隆起下降，陆源碎屑的供给又转变为北偏西方向的阴山古陆的中元古代钾长花岗岩，除在 ZG6-1分层中的大量石英外，主要为黏土矿物。在泥炭聚积和成岩作用早期阶段，ZG6-5、ZG6-4、ZG6-3 和 ZG6-2 分层中三水铝石胶体溶液在上覆沉积物的压实作用下，发生脱水作用形成勃姆石。从勃姆石的赋存形态来看，大部分勃姆石呈絮凝状，也反映了它的胶体成因的特点。刘长龄等( 1985) 认为，勃姆石形成主要与成岩阶段的弱酸性与弱氧化至弱还原的介质环境有关，勃姆石在泥炭沼泽中更易形成。山西河曲本溪组铝土矿富含勃姆石，山西和河南铝土矿的重矿物组成有锆石、金红石、方铅矿等，和富勃姆石煤层中的重矿物组合相似( 刘长龄等，1985) ，也是 6 号煤层中勃姆石来源于本溪组铝土矿的佐证。6 号煤中高含量勃姆石的形成与含煤岩系高岭岩中的勃姆石或勃姆石岩的形成不同，刘钦甫等( 19) 的研究表明，含煤岩系高岭岩中的勃姆石或勃姆石岩中勃姆石的形成主要是高岭石在介质的酸度( pH < 5) 增大时脱硅形成的，并且具有高岭石的象。而在该煤层中的勃姆石没有交代高岭石的现象。

表2 勃姆石及其伴生矿物的SEM-EDX 测试结果

注: Min 为最小值; Max 为最大值; AM 为算术均值; bdl 为低于检测极限。

研究区晚古生代煤中高含量勃姆石的出现并不是一个简单、孤立的地质，它独特的赋存状态、成因、伴生矿物组合关系与其周围的地质体、煤层的形成演化、煤层形成时的古地理和古气候具有不可分割的联系。

致谢: 感谢中国科学院地质与地球物理研究所曾荣树研究员和中国石油大学( 北京) 钟宁宁教授给予的悉心指导和大力帮助。

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图版说明

图版Ⅰ

1. ZG6-1 中的石英( SEM ) 。

2. ZG6-1 中的石英，矿化现象严重( 油浸，反射单偏光，320 × ) 。

3. ZG6-1 中的石英，棱角明显，粒度均匀( SEM ) 。

4. ZG6-2 中规则的团块状勃姆石( SEM ) 。

5. ZG6-2 中不规则团块状勃姆石( SEM ) 。

6. ZG6-3 中不规则团块状勃姆石，突起高( 油浸，反射单偏光，320 × ) 。

7. ZG6-3 中充填于丝质体胞腔的勃姆石和磷锶铝石( SEM ) 。

8. ZG6-5 中黏土矿物，不显突起( 油浸，反射单偏光，320 × ) 。

图版Ⅱ

1. ZG6-2 中的金红石晶体( 油浸，反射单偏光，320 × ) 。

2. ZG6-2 中金红石的膝状双晶( SEM ) 。

3. ZG6-3 中充填于胞腔的磷锶铝石( SEM ) 。

4. ZG6-3 中呈浑圆状产出的硒方铅矿( SEM ) 。

5. ZG6-3 中硒铅矿的内部结构( SEM ) 。

6. ZG6-2 中的锆石( SEM ) 。

7. ZG6-3 中的锆石( SEM ) 。

8. ZG6-3 中的菱铁矿( SEM ) 。

代世峰等: 鄂尔多斯盆地东北缘准格尔煤田煤中超常富集勃姆石的发现

图版Ⅰ

任德贻煤岩学和煤地球化学论文选辑

代世峰等: 鄂尔多斯盆地东北缘准格尔煤田煤中超常富集勃姆石的发现

图版Ⅱ

任德贻煤岩学和煤地球化学论文选辑

A discovery of extremely-enriched boehmite from coal in the Junger coalfield，the northeastern Ordos Basin.

DAI Shifeng1，2，REN Deyi1，2，LI Shengsheng2，Chen Lin CHOU3

( 1. Key Laboratory of Coal Resources of CUMT，Beijing，100083; 2. Department of Resources and Earth Science， China University of Mining and Technology，Beijing，100083; 3. Illinois State Geological Survey，IL61820，USA)

Abstract: The authors found an extremely-enriched boehmite and its associated minerals for the first time in the super-thick No. 6 coal seam from the Junger Coalfield in the northeastern Ordos Basin by using technologies including the X-ray diffraction analysis ( XRD ) ，scanning electron microscope equipped w ith an energy dispersive X-ray spectrometer，and optical micro- scope. The content of boehmite is as high as 13. 1% ，and the associated minerals are goyazite， zircon，rutile，goethite，galena，clausthalite，and selenio-galena. The hey minerals assem- blage is similar to that in the bauxite of the Benxi Formation from North China. The high boehmite in coal is mainly from w eathering crust bauxite of the Benxi Formation from the north- eastern coal-accumulation basin. The gibbsite colloidstone solution w as removed from bauxite to the peat mire，and boehmite w as formed via compaction and dehydration of gibbsite colloid- stone solution in the period of peat accumulation and early period of diagenesis.

Key words: coal; boehmite; Late Paleozoic period; Junger Coalfield

( 本文由代世峰、任德贻、李生盛合著，原载《地质学报》，2006 年第 80 卷第 2 期)

天然气（Natural Gas）是一种主要由甲烷组成的气态化石燃料。它主要存在于油田和天然气田，也有少量出于煤层。

当非化石的有机物质经过厌氧腐烂时，会产生富含甲烷的气体，这种气体就被称作生物气（沼气）。生物气的来源地包括森林和草地间的沼泽、垃圾填埋场、下水道中的淤泥、粪肥，由细菌的厌氧分解而产生。生物气还包括胃肠涨气（例如：屁），胃肠气最通常来自于牛羊等家畜。

当甲烷散逸到大气层中时，它将是一种直接促使全球变暖愈演愈烈的温室气体。这种飘散的甲烷，就会被视作一种污染物，而不是一种有用的能源。然而，在大气中的甲烷一旦与臭氧发生氧化反应，就会变成二氧化碳和水，因此排放甲烷所导致的温室效应相对短暂。而且就燃烧而言，天然气要比煤这类石炭纪燃料产生的二氧化碳要少得多。甲烷的重要生物形式来源是白蚁、反刍动物（如牛羊）和人类对土地的耕种。据估计，这三者的散发量分别是每年15、75和100百万吨（年散发总量约为1亿吨）。