无烟煤水煤浆燃烧特性和气化特性研究

为了提高水煤浆成浆浓度,选取一种无烟煤作为研究对象,分别利用常规研磨工艺和分级研磨工艺进行制浆实验考察其成浆性能。结果表明：利用分级研磨工艺优化粒度后,水煤浆浓度能达到67.3%,成浆性良好。选取2种工艺制得的样品进行了燃烧特性实验,发现采用分级研磨工艺制得的样品的燃点和燃烬温度有一定程度的降低,燃烬指数增大,加入助燃剂后该特性更加明显,这是由于分级研磨工艺所制水煤浆中细颗粒含量增加,反应活性变好。重点考察了不同催化剂加入量对煤样气化反应活性的影响。随着催化剂加入量的增加,气化反应活性有不同程度提高,实验样品的催化剂的最佳加入量为0.2%。     

Cracking of a mixture of mechanically treated brown coal and petroleum residue

The combined cracking of brown coal and petroleum residue was performed, and the composition of the products obtained was studied. It was found that the mechanical treatment of coal makes it possible to increase the yield of the liquid products of pyrolysis and to improve their quality.     

Combustion characteristics of coal in a mixture of oxygen and recycled flue gas

The combustion of coal in a mixture of pure O₂ and recycled flue gas is one variant of a novel combustion approach called oxy-fuel combustion. With the absence of N₂, this approach leads to a flue gas stream highly enriched in CO₂. For many applications, this flue gas stream can then be compressed and sequestered without further separation. As a result, oxy-fuel combustion is an attractive way to capture CO₂ produced from fossil fuel combustion. When coal is burned in this O₂ and CO₂ rich environment, its combustion characteristics can be very different from conventional air-fired combustion. In CETC-O, a vertical combustor research facility has been used in the past years to investigate the combustion characteristics of several different coals with this variant of oxy-fuel combustion. This included flame stability, emissions of NO_x, SO_x and trace elements, heat transfer, in-furnace flame profiles and flue gas compositions. This paper will report some of the major findings obtained from these research activities.     

Extraction of coal using supercritical water

An experimental apparatus was developed to inject coal into an autoclave containing preheated supercritical water. The supercritical water appears to act as both solvent and reactant in the conversion of coal to gases and liquids. Experiments were carried out with German brown coal, lignite and bituminous coal and with glucose at both subcritical and supercritical water densities. A significantly larger quantity of char was obtained when operating at subcritical densities and when the coal was mixed with water before heating to supercritical conditions. Smaller amounts of char were obtained as density increased and as reaction time increased.     

Sulfur transformations during supercritical water oxidation of a Chinese coal

The oxidation of coal in supercritical water was explored by using H₂O₂ as the oxidant. The sulfur-containing components in the effluents were identified. The experiments, which were conducted in a bench scale semi-continuous Supercritical Water Oxidation (SCWO) installation, indicated that the sulfur contained in coal could be gradually oxidized to sulfate in supercritical water medium. The main species containing sulfur in the effluents of coal SCWO were determined as sulfide, thiosulfate, sulfite and sulfate, in which thiosulfate and sulfate were predominant. The effects of the reaction temperature and time on the sulfur transformations during SCWO of coal were also investigated.     

Thermal decomposition features of ammonium nitrate and its boron mixture under high pressures

The kinetics of ammonium nitrate thermal decomposition was studied by the differential thermal analysis in the pressure range from atmospheric to 1.0 GPa. The decomposition under pressure was shown to obey the zero-order equation with a constant proportional to the initial HNO₃ concentration in the sample. The structural transitions in ammonium nitrate were found to affect its exothermic interaction with boron. The mechanism of this phenomenon was interpreted. The experimental data allowed to establish volume changes on melting ammonium nitrate, equal to 0.072 cm³/g.     

An experimental and modeling study of vacuum residue upgrading in supercritical water

Arabian Heavy crude oil was fractionated into distillate and vacuum residue fractions. The vacuum residue fraction was treated with supercritical water (SCW) at 450°C in a batch reactor for 15–90 min. The main products were gas, coke, and upgraded vacuum residue; the upgraded residue consisted of gasoline, diesel, and vacuum gas oil range components. The molecular composition of gas and upgraded vacuum residue was analyzed using gas chromatography (GC, GC × GC). SCW treatment converted higher carbon number aliphatics (≥C₂₁) and long‐chain (≥C₅) alkyl aromatic compounds into C₁?C₂₀ aliphatics, C₁?C₁₀ alkylaromatics, and multiringed species. The concentrations of gasoline and diesel range compounds were greater in the upgraded product, compared to the feed. A first‐order, five lump reaction network was developed to fit the yields of gas, coke, diesel, and gasoline range components obtained from SCW upgrading of vacuum residue. Distillation of crude oil followed by SCW treatment of the heavy fraction approximately doubled the yield of chemicals, gasoline, and diesel, while forming significantly less coke than conventional upgrading methods. © 2018 American Institute of Chemical Engineers AIChE J, 64: 1732–1743, 2018     

水煤浆添加剂及水煤浆稳定性的研究

研究了实验室中制备水煤浆的方法,选择了合适的煤种和适合成浆的煤粉粒度分布。使用了不同分子结构的高分子阴离子型表面活性剂作为添加剂制备水煤浆。研究了不同分子结构的添加剂对同种煤质的水煤浆成浆性的性能比较,选择出了合适的主添加剂。探讨了添加剂的添加量与煤的成浆性、流变性以及静态稳定性的关系。结果表明,添加剂的分子链长短、分子链上的活性基团的多少等因素以及在煤浆中的添加量对水煤浆的成浆性、黏度、质量分数、流变性以及稳定性具有显著的影响。     

中国水煤浆制备技术的发展

为了应对中国易成浆煤种(炼焦煤)储量少的现状,以神华煤等为研究对象,对其制浆工艺进行了研究。神华煤符合水煤浆对煤质的要求,但属低变质且难制浆煤种。从级配理论入手,开发出新的制浆工艺及配套专用设备和添加剂,可以利用神华煤制取高浓度水煤浆。在此基础上,利用城市污泥和造纸黑液制备生物质煤浆,提高了水煤浆的分散性,同时在工业性锅炉中的燃烧表明:负荷可在45%～100%下连续调节,燃烧效率高达98.66%。此外,分级研磨级配制浆工艺可以使水煤浆质量分数提高3%～5%,系统产能提高30%以上。     

水煤浆技术现状分析及发展方向

首先简单介绍了水煤浆的适用条件及其制备和燃烧情况。为了证明水煤浆技术的环保、经济等优越性,以东莞某100万t/a水煤浆生产厂为例,从施工准备、系统配置、厂区设置等方面介绍了其总投资情况;从原料费、人工费、电费、修理费等方面论述了其运行成本情况。以广东省某10 t/h的燃油锅炉、10 t/h燃煤链条锅炉与水煤浆锅炉为例,从发热量、硫分、锅炉效率、原料消耗量、总投资、运行成本等方面进行对比分析。最后针对水煤浆的国家标准制订提出了建议。     

Experimental investigation of high-temperature coal tar upgrading in supercritical water

The upgrading of high-temperature coal tar in supercritical water (SCW) was investigated using an autoclave reactor. The effects of temperature (673–753 K), pressure (24–38 MPa) and residence time (1–80 min) on product distribution were studied. The yields and characteristics of products in SCW were compared with those obtained in N₂. In order to study the reaction mechanism of coal tar upgrading, the experiments of model compounds were carried out in SCW at 673 K and 34 MPa for 20 min. The results indicate that the asphaltene conversion and the maltene yield are significantly higher in SCW. The H/C atom ratios of oil obtained in SCW are higher than those obtained in N₂. More valuable aromatic compounds such as naphthalene, fluorene and anthracene are obtained in SCW. The results of model compounds suggest that water in SCW could participate in coal tar upgrading and promote the formation of light products.     

褐煤制浆和配煤制浆技术

基于中国煤炭资源状况及褐煤难成浆的特点,提出采用配煤制浆的方法来提高制浆浓度。分析了国内外褐煤和配煤制浆技术的研究现状,同时介绍了国内褐煤制浆技术的发展。研究发现:现有的配煤技术多采用煤质较好的原煤和褐煤,应寻求更多的现有资源和褐煤配煤制浆来提高煤浆浓度,尤其是热值不低却未被充分利用的煤炭资源,如煤炭液化废渣、沥青等,以充分利用煤炭资源,保护环境。     

工业废水和煤液化残渣制取水煤浆的研究

对工业废水和煤液化残渣制备水煤浆的特性进行了实验研究,在选取5#添加剂和添加剂加入量为0.4%的条件下,废水煤浆浓度、黏度、析水率、流动性均符合湿法气流床加压气化生产的要求。随着废水配入比例的增加,浆体黏度逐渐增大,煤浆稳定性得到改善。随着废水稀释比例的增加,最高成浆浓度逐渐升高。利用工业废水和煤液化残渣制取水煤浆,减轻了对环保的负担。     

低挥发分煤制备气化水煤浆的可行性研究

介绍了国内外水煤浆气化技术的发展历程,研究了国家水煤浆工程技术研究中心研发的“分级研磨高浓度制浆工艺”的提浓效果及其对气化水煤浆技术发展的推动作用。选取了一种无烟煤进行成浆性试验。结果表明：在传统制浆工艺下,该煤样的制浆浓度即可达到62％,若采用分级研磨制浆工艺,可使制浆浓度提高至65％,可作为气化水煤浆的制浆用煤。进行了不同粒度条件和加入催化剂情况下煤浆的热天平试验,分析了不同试验条件下样品的失重与失重速率数据。试验证明了该煤样的气化反应活性可通过一定手段提高,结合工业实践,分析了低挥发分煤制备气化水煤浆的可行性。     

神府煤水煤浆管道输送试验研究

为获得神府煤水煤浆最佳管道输送参数,进行了水煤浆流变性试验,确定了水煤浆临界剪切速率。通过水煤浆剪切速率和剪切应力的关系确定神府煤水煤浆流变性模型,拟合出适于神府煤水煤浆流变性的数学方程。在不同管道直径和水煤浆浓度下,研究了水煤浆平均速率对管道压力损失的影响,得到了最佳水煤浆管道输送参数。结果表明:神府煤水煤浆临界剪切速率为40.74 s-1,水煤浆拟合后的流变方程符合宾汉塑性体模型,适宜泵送和管道输送。低浓度、低黏度的水煤浆更适合管道输送。在水煤浆平均流速相同的条件下,管道直径越小,管道压力损失越大。管道直径为200~300 mm时,神府煤水煤浆在管道输送中的压力损失在工业应用合理范围内,适宜管道输送。     

水煤浆添加剂的研究进展

随着世界原油资源的日渐减少及燃煤污染的日趋严重，水煤浆作为一种新型的环保型煤基流体燃料日益受到人们的重视。从70年代至今，国内外学都研究过多种添加剂，目前制浆用添加剂主要分为阴离子表面活性和非离子表面活性剂两大类，但高效、价廉、适用性广的添加剂为数并不多。     

Liquefaction of rice straw in sub- and supercritical 1,4-dioxane–water mixture

The critical liquefaction of rice straw in sub- and supercritical 1,4-dioxane–water mixture was investigated in a 500 mL autoclave at temperature of 260–340 °C, resistance time of 0–20 min, and volume ratios 0–100 vol.% (1,4-dioxane:mixture). The yields of oil and PA + A (preasphaltene and asphaltene) were in the range of 29.64–57.30 wt.% and 6.42–22.68 wt.%, depending on the temperature, resistance time and volume ratio. The synergistic capability of 1,4-dioxane–water mixture could allow the great decomposition of the tubular structure of lignocelluloses. It was shown by the results that the “oxygen-transfer” reaction, deoxygenation and decarboxylation may occur in the liquefaction of rice straw with 1,4-dioxane–water mixture, while deoxygenation and decarboxylation may be the main reaction. The oil and PA + A fractions obtained at different volume ratios were analyzed by FTIR and GC–MS to investigate the effect of the ratios on the type of the compounds in the liquid products. It is shown that the nucleophilic and hydrolytic functions of water might be weaken at the higher ratio of 1,4-dioxane runs, resulting the lower amount of phenolic, acidic, hydrocarbon and ester derivatives in the oil and PA + A fractions.     

Brown coal conversion under the action of supercritical water

A test bench was developed and the conversion of the organic matter of coal (OMC) in supercritical water (SCW) was studied under conditions of a continuous supply of a water-coal suspension to a vertical flow reactor at 390–760°C and a pressure of 30 MPa. From 44 to 63% OMC was released as liquid and gaseous products from coal particles (from the water-coal supension) during the time of fall to the reactor. This stage was referred to as the dynamic conversion of coal. The particles passed through the stage of the dynamic conversion of coal did not agglomerate in the reactor in the subsequent process of batch conversion in a coal layer at T = 550–760°C. The volatile products of the overall process of the dynamic and batch conversion of coal included saturated hydrocarbons (CH₄ and C₂H₆), aromatic hydrocarbons (C₆H₆, C₇H₈, and C₈H₁₀), synthesis gas (H₂ and CO), and CO₂. At T < 600°C, CO₂ and CO were the degradation products of oxygen-containing OMC fragments, whereas they also resulted from the decomposition of water molecules at higher temperatures in accordance with the reaction (C) + H₂O = CO + H₂. The mechanisms were considered, and the parameters responsible for the dynamic conversion of coal were calculated.     

Anomalies in the burning of ammonium perchlorate and ammonium nitrate

Conclusions We have considered possible mechanisms of retardation of the chemical reactions when ammonium nitrate and perchlorate burn and have shown that one such mechanism is retardation by the water formed during combustion.We have studied the effect of the additives silica, liquid silicone, calcium stearate, etc. on the burning of ammonium perchlorate and ammonium nitrate catalyzed with chromium oxide in order to establish the causes of the anomalies observed during their combustion.We have shown that over a certain pressure range adding silica eliminates the observed anomalies (fall in burning rate with increase in pressure and pulsating combustion), whereas the addition of calcium stearate intensifies them.Depending on the pressure interval and the conditions under which combustion proceeds, the same additive may play the role of an inert admixture, a catalyst, or an inhibitor, which is apparently associated with changes in the leading reactions in differentpressure intervals.The author warmly thanks V. K. Bobolev for his assistance.Fizika Goreniya i Vzryva, Vol. 4, No. 3, pp. 314–322, 1968