可编程序控制器在电厂输煤系统中的应用

介绍了可编程控制器的特点和美国ＭＯＤＣＯＮ公司的ＱＵＡＮＴＵＭ系列可编程控制器在太原一电厂输煤程控系统中的应用。     

Isotropic carbon and graphite fibers from chemically modified coal-tar pitch

A precursor for a general purpose carbon fiber was prepared from coal tar pitch (CP) modified with 10 % p-benzoquinone (BQ) at 380 ?C for 3 hours. Such a modification raised the softening of the pitch from 85 ?C to 271 ?C at a yield of 43 %. The modified pitch was spun smoothly at a rate of 480 m/min into a fiber of 20 Μm diameter. The fiber was stepwise stabilized at 236 ?C (5 ?C/min) and 312 ?C (1 ?C/min) for 3 hours at each temperature. Successively,carbonization and graphitization were performed at 1,000 ?C and 2,400 ?C, respectively, for one hour. Both the carbonized and graphitized fibers exhibited tensile strength of 570 MPa. The structural parameters of carbon and graphite fibers were their orientation values of 56.2 and 58.1 %, relatively low Lc(002) of 11.24 and 25 å, and large interlayer spacing (d₀₀₂) of 3.86 and 3.49 å, respectively.     

EFFECT OF OXIDATION PERIOD ON HELIUM DENSITY, SPECIFIC ENERGY AND ACIDITY VALUES IN OXIDATION OF COAL AND CORRELATION FOR PREDICTION OF SPECIFIC ENERGY

In this paper the effect of residence time on variation in helium density, specific energy, acid equivalents, carboxyl and phenolic acidity values in the process of low temperature oxidation of Assam Coal has been highlighted. It has been observed that the progressive increase of oxidation time resulted in reduction of specific energy but caused to increase in helium density, acid equivalents, carboxyl and phenolic acidity values of oxidised product. The specific energy of oxidised coal is found to correlate linearly with helium density with correlation coefficient of 0.996.     

Use of infrared thermography for the evaluation of heat losses during coal storage

The exothermic processes during coal storage reduce the calorific value of the coal which in turn results in financial losses. An accurate and easy calculation of the losses may be an efficient tool to evaluate the effectiveness of the measures taken to reduce the spontaneous heating of coal and to predict the appearance of hot spots. This study was carried out with ‘Mezcla' coal used at Endesa power station in Andorra–Teruel (Spain). For this purpose, laboratory measurements relating to spontaneous heating properties and field measurements were carried out. Three experimental coal piles were built, a high porosity pile, a periodically compacted pile and a pile with a low angle slope in the prevailing wind direction. A method to determine the coefficient of total losses was developed and the coefficients of calorific losses and total losses were also found. Temperatures were measured by infrared thermography and by thermocouples and a good agreement between them was found. The use of a mathematical model, developed by ASINEL, allowed to calculate the heat fluxes due to spontaneous heating and a new coefficient of calorific losses, the similarity of this coefficient with the experimentally found revealed the effectiveness of this method to quantify heat emissions. The self-heating behaviour of the pile was also followed by an infrared thermographic camera which allowed the detection of heat fluxes.     

煤沥青橡胶改质筑路油的老化特征

研究了煤沥青橡胶改质筑路油在加速热老化过程中的性质变化,建立了粘度与温度及针入度与温度的关联式,与石油道路沥青相比,前者的耐老化性要比后者稳定,胶体结构也由溶-凝胶型转变为凝胶型。     

煤焦油沥青纤维的不熔化过程研究

以硫化法制得的高软化点（２５５ ℃） 煤焦油沥青为原料,通过熔融纺丝、氧化不熔化及炭化处理制备煤焦油基沥青纤维。探讨了不熔化终温对产品炭纤维抗拉强度的影响,借助于元素分析、气相色谱分析（ＧＡ）、ＤＴＡ、ＴＧ 和红外光谱分析等表征手段,对沥青纤维的不熔化过程进行了研究。结果表明：氧化终温强烈影响着炭纤维的抗拉强度;煤焦油沥青纤维在空气中的不熔化过程在低于３４０ ℃时表观上表现为恒重恒热,氧化反应主要发生于２００～３４０ ℃之间。     

工业锅炉炉膛空气动力特性的试验研究

根据工业锅炉燃烧特点及配风要求,以一台热效率比较高、环保指标比较好的１４ Ｍ Ｗ 热水锅炉为基础,利用七孔探针测试了不同炉膛形状、前后拱配合方式下的炉内空气动力场．测试结果表明：工业锅炉中,折焰墙形状、前后炉拱配合方式对炉内燃烧效率有较大影响．通过试验研究,提出了折焰墙尺寸的设计原则．这对于节约燃料,降低工业锅炉初始排尘浓度和烟气黑度,对于工业锅炉燃烧室的设计和改造具有较大实际意义     

Remediation of ash problems in pulverised coal-fired boilers

This paper reports the control methods for mitigating fouling and slagging in brown coal-fired power utilities. Two control methods were investigated, i.e. wet pretreatment of coal and the use of mineral additives. By the first technique, samples of brown coal were treated with aluminium solutions to adjust the levels of Na, Al and Cl. The effect of cleaning was tested under closely controlled conditions in the range of 1000–1400°C. At a gas temperature of 1250°C, the deposition behaviour of treated and raw coals were compared using a deposition probe maintained at temperatures of 500, 600, 700 and 800°C. The second technique involved experiments with mixtures of candidate mineral additives and sodium compounds at temperatures ranging from 1000 to 1400°C.

Experiments showed that both the methods were effective in reducing ash-related problems. Between 1000 and 1400°C, the quantity of condensable salts generated was found to depend only on the amount of sodium in coal. With the wet method, aluminium reduces the sodium level and thus fouling by ion exchange. The stickiness of sodium silicates from this coal was also shown to be reduced by aluminium. Deposition model calculations based on sticking probability also indicated that Al-treated coals result in less ash deposition on boiler surfaces. Experiments with mineral additives showed that sodium could be captured by clay minerals, particularly kaolin. For Victorian brown coal-based power station boilers, 10–20 μm kaolin making up 2–3 wt.% of the feed was estimated to effectively reduce the ash problems.     

Viscosity measurements and empirical predictions for fluxed Australian bituminous coal ashes

Recent interest in the suitability of Australian bituminous coals for use in integrated gasification-combined cycle (IGCC) technologies has provided the opportunity to determine viscosity data for a range of coal ashes slags fluxed with limestone at the tapping temperatures of entrained flow gasifiers. Experimental viscosity measurements have been made over a range of slag compositions covering the anorthite region at the 0–2.5, 2.5–5, 5–7.5 and 7.5–10 wt% FeO levels of the quaternary SiO₂–Al₂O₃–CaO–FeO system. Contour plots of viscosities at 1450°C for the four FeO ranges are presented as an example for predicting slag behaviour in entrained flow gasifiers. The viscosity measurements have also been fitted empirically using a modified Urbain treatment to give separate models for the four FeO levels. Polynomial expressions are given for the evaluation of viscosities covering the temperature range 1400–1550°C for slags within the compositional range used in the derivation.     

煤的微生物脱硫

介绍了煤中的存在形式,微生物脱硫的原理及主要的脱硫用微生物菌种,探讨了微生物脱硫和其工业应用前景。