燃煤锅炉碱性废物及其脱硫能力的研究

A Study on Alkaline Waste of Coal-burning Boilers and the FGD Possibility

通过对燃煤锅炉排放碱性废物及其可利用形式的分析,指出其含量受煤种、水质、燃烧方式、灰渣处理方式等多因素影响。实测了一台4t/h链条炉的排污水、离子树脂反洗水,设计了飞灰碱性溶出率的条件试验,并从理论上计算了碱性废物烟气脱硫的可能性。为便于比较,采用了将脱硫能力折合为单位蒸吨脱除率的表示方法。研究结果表明,在试验条件下单位蒸吨锅炉碱性废物可脱除0.415kg的SO2,占总排放量1.275kg的32.56%。其中排污水、反洗水和飞灰分别占8.63%、23.06%和0.87%。反洗水虽有脱硫能力,但成分复杂,可对水循环系统产生腐蚀,实际中尚未利用。飞灰脱硫能力低,因试验煤种钙镁氧化物含量仅为6.5%,在PH值为2.61时达到13.23%平衡溶出率。试验结果表明:飞灰碱性物质溶出率与PH值,搅拌时间有关。PH值低,溶出率大,搅拌时间长,溶出率高。飞灰的脱硫能力主要取决于煤灰的碱性氧化物含量。对碱性含量不高的飞灰,碱性溶出率少,利用其进行烟气脱硫的能力非常有限。这一点不同于钙镁含量高的褐煤和某些低硫煤。

This paper pointed out that the quantity of alkaline waste of coal-burning boilers is affected by coal types, supply water quantity, combustion forms, ash and slag disposal methods and other relative factors through analyzing waste sources and their utilizability. A 4 t/h chain boiler's time drainage and the backwashing water from the ion resin intenerating pot have been sampled and measured. The conditioned tests for extraction of the alkali in fly ash have been done. The possibility for FGD has been calculated theoretically. In order to compare the results, the SO2 removal rate per ton vapor has been used to show the FGD possibility. The results showed that the boiler's alkaline waste could neutralize 0.415 kg SO2, taking up 32% of total emission 1.275 kg SO2 per ton vapor. Drainage, backwashing and ash alkali were taken up 8.63%, 23.06% and 0.87% respectively. Although the backwashing water has certain Calcium and Magnesium ions, it has not been used in FGD due to its complex components with high concentration salts and /or acids, the corrosion may be introduced if the water goes into the FGD liquid recycle system. The FGD possibility of the fly ash was very low because the tested coal only with 6.5% Calcium and Magnesium oxidizers, 2.59% Iron oxidizer and 16.53% Aluminium oxidizer. The balance extraction rate was only 13.23% when the fly ash was under the 2.61 PH value. The conditioned tests results showed that the extraction rate of fly ash alkali was affected by PH value and the stirring time. The lower the PH value, the higher the extraction rate. The longer the stir time, the higher the extraction rate too. The FGD possibility is mainly depended on the contents of metal oxidizers, such as Calcium, Magnesium, Potassium, Sodium and others. For those types of coal like the tested, which contain only a little of alkaline components, the total extracted alkali is less and the FGD possibility is very limited. This is very different from the brown coal and some low sulfur coal that contain high content of metal oxidizers.