煤气化是将煤转化为合成气的过程，是实现煤炭清洁利用的核心技术之一。随着煤气化技术的推广应用，大量的固体废弃物煤气化细渣随之产生，因其具有高碳含量、高烧失率的特点，不能直接作建筑材料使用。煤气化灰渣中含有丰富的铝、硅和碳资源，如果能够对煤气化细渣中的这些资源进行分质利用，将不仅解决废弃物对环境产生的危害，还可以获得更多的能量，及满足社会对铝硅资源的需求。总之，实现煤气化细渣的高附加值利用对于环保、经济和社会等方面都将产生积极的作用。本文以神华神木化学有限公司的煤气化细渣为原料，针对其碳含量高、活性低特性，首先按照粒径不同对煤气化细渣进行分级，将其中的无机组分进行富集。然后通过具有高温和强化传质传热的水热过程提取煤气化细渣中的铝元素，富铝离子的酸浸液用于制备高铝含量的聚合氯化铝。剩余的酸浸渣以硅元素为主，通过补加造孔剂、粘结剂压制成型后烧制多孔陶瓷。主要研究内容及结果如下：

（1）对不同粒径的煤气化细渣进行分级获得本文的原料。煤气化细渣的粒径不同，其所含的碳组分与无机组分的含量有较大差异。本文通过对不同粒径煤气化细渣进行分析发现，粒径在0.075-0.125 mm范围内的煤气化细渣其无机组分含量最高，达到70.8%，而粒径小于0.045 mm范围内的煤气化细渣含碳量最高，因此选用0.075-0.125 mm粒径范围的煤气化细渣为提硅提铝的原料。

（2）以富无机组分的煤气化细渣为原料，通过强化传质传热的水热过程提取煤气化细渣中的铝元素。实验结果表明，过高的酸浓度会形成硅酸盐沉淀抑制铝元素提取，最优的盐酸浓度为20%，最优的反应温度和时间为120℃和150 min。SEM、XRD和FTIR表征表明，煤气化细渣在酸浸后，其在铝、铁和钙等元素被溶解在酸液中，煤气化细渣表面由光滑变得粗糙多孔，内部孔隙结构也明显增多。

（3）以富铝元素的酸浸液为原料，在油浴锅恒温条件下加入铝酸钙粉聚合制备聚合氯化铝，铝酸钙加入量、聚合温度和时间均对产物具有一定影响。加入铝酸钙后，其所含的铝会溶解到液相中参与反应，增加产物的盐基度，但盐基度过高会降低产品的稳定性，因此不能过量。XRD和FTIR证明产物中没有检测到氯化铝的衍射峰，溶液中的铝离子聚合形成非晶态聚合氯化铝。

（4）以提铝后的酸浸残渣为原料，通过补加粘结剂、造孔剂压制成型后烧制多孔陶瓷。经探讨发现，糊精、聚乙烯醇、羧甲基纤维素三种粘结剂对多孔陶瓷的物相没有太大影响，但糊精作为粘结剂，其孔隙率和抗压强度较好；淀粉作为造孔剂所制多孔陶瓷其内部孔隙分布均匀，孔洞数量较多，而碳酸钙和石墨作造孔剂孔隙相对杂乱，且孔径大小不均匀；加入适量淀粉可以增大陶瓷孔径和增大孔隙数量，过多会显著降低抗压强度，不利于实际应用。XRD与SEM结合证明产物中含有莫来石、方石英和堇青石，均为多孔陶瓷的主要矿相。

总之，本文通过粉碎筛分获得富无机组分，再通过水热提铝得到富铝酸浸液，再采用中和和聚合反应得到聚合氯化铝，最后将酸浸后的富硅残渣应用于多孔陶瓷制备，基本上实现了煤气化细渣富无机组分的全部利用。对制备过程中的结构变化，影响机制和工艺优化进行了深入探讨，为煤气化细渣的高附加值利用奠定了理论和实验基础。

关 键 词：煤气化细渣；水热法；聚合氯化铝；多孔陶瓷；孔隙率

研究类型：应用基础研究

Coal gasification is a process of converting coal into syngas, which is one of the core technologies to realize clean utilization of coal. With the popularization and application of coal gasification technology, a large number of solid waste coal gasification fine slag is produced. Because of its characteristics of high carbon content and high fever loss rate, it can not be directly used as building materials. Coal gasification ash contains rich aluminum, silicon and carbon resources. If these resources in coal gasification fine slag can be used in a qualitative way, it will not only solve the harm caused by waste to the environment, but also obtain more energy and meet the social demand for aluminum and silicon resources. In conclusion, the realization of high value-added utilization of coal gasification fine slag will have a positive effect on environmental protection, economy and society. In this paper, the fine slag of coal gasification from Shenhua Shenmu Chemical Co., Ltd. is used as raw material. In view of its characteristics of high carbon content and low activity, the fine slag of coal gasification is firstly graded according to different particle sizes, and the inorganic components in it are enriched. Then, aluminum was extracted from coal gasification fine slag by hydrothermal process with high temperature and enhanced mass and heat transfer. The acid leaching solution rich in aluminum ions was used to prepare polyaluminum chloride with high aluminum content. The remaining acid leaching slag is mainly silicon element, and the porous ceramics are fired after being pressed by adding pore-making agent and binder. The main research contents and results are as follows:

(1) The raw materials of this paper are obtained by classifying fine coal gasification slag of different particle sizes. The content of carbon and inorganic components in coal gasification fine slag varies greatly with different particle size. In this paper, through the analysis of coal gasification fine slag with different particle sizes, it is found that the inorganic component content of coal gasification fine slag with particle size between 0.075 and 0.125 mm is the highest, reaching 70.8%, while the carbon content of coal gasification fine slag with particle size less than 0.045 mm is the highest. Therefore, coal gasification fine slag with particle size range of 0.075-0.125 mm was selected as the raw material for silicon and aluminum extraction.

(2) Aluminum was extracted from coal gasification fine slag rich in inorganic components by hydrothermal process which enhanced mass and heat transfer. Experimental results show that excessive acid concentration can form silicate precipitation and inhibit aluminum extraction. The optimal concentration of hydrochloric acid is 20%, and the optimal reaction temperature and time are 120℃ and 150 min. SEM, XRD and FTIR characterization show that after acid leaching, the elements such as aluminum, iron and calcium are dissolved in the acid solution. The surface of the fine coal gasification slag changes from smooth to rough and porous, and the internal pore structure also increases significantly.

(3) Polyaluminum chloride was prepared from aluminum-rich acid leaching solution by adding calcium aluminate powder under constant temperature in oil bath. The amount of calcium aluminate, polymerization temperature and time all had certain effects on the product. After adding calcium aluminate, the aluminum contained in it will dissolve into the liquid phase to participate in the reaction, increasing the basicity of the product, but too high basicity will reduce the stability of the product, so it can not be excessive. XRD and FTIR proved that no diffraction peak of aluminum chloride was detected in the product, and the aluminum ions in the solution were polymerized to form amorphous polyaluminum chloride.

(4) Taking the acid leaching residue after aluminum extraction as raw material, the porous ceramics were fired by adding binder and pore-forming agent. It was found through experiment that dextrin, polyvinyl alcohol and carboxymethyl cellulose had no significant effect on the phase of porous ceramics, but dextrin as a binder had better porosity and compressive strength. The porous ceramics made of starch as pore-making agent have uniform pore distribution and a large number of pores, while the pores of calcium carbonate and graphite as pore-making agents are relatively disorderly and the pore size is not uniform. Adding proper amount of starch can increase pore size and pore number of ceramic, too much starch will significantly reduce the compressive strength, which is not conducive to practical application. XRD and SEM show that the products contain mullite, quadrite and cordierite, which are the main mineral phases of porous ceramics.

In short, in this paper, the inorganic rich components were obtained by grinding and sieving, then aluminum-rich acid leaching solution was obtained by hydrothermal extraction of aluminum, and then poly aluminum chloride was obtained by neutralization and polymerization reaction. Finally, the silicon-rich residue after acid leaching was applied to the preparation of porous ceramics, which basically realized the full utilization of inorganic rich components of coal gasification fine slag. The structural changes, influencing mechanism and process optimization in the preparation process are discussed, which lays a theoretical and experimental foundation for the high value-added utilization of fine slag of coal gasification.

Key words:

Coal Gasification Fine Slag; Hydrothermal Process; Polyaluminum Chloride; Porous Ceramics; Porosity

Thesis    :

Applied basic research

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