碱渣基本性质及工程应用研究进展

Progress in the study of the basic properties and engineering applications of alkali residue

  • 摘要: 碱渣是氨碱法生产纯碱过程中产生的废渣,具有含水率、孔隙率高和粒度小等特征,因其产量高、利用率低,导致碱渣大量堆积,严重制约了制碱工业的发展,亟需推进碱渣的大规模应用. 本文全面总结了碱渣的基本性质及在工程应用方面的研究成果和最新进展. 结果表明,碱渣成分复杂,主要矿物成分为CaCO3,质量占比高达32.52%~64.00%. 碱渣为一般工业固废,其重金属含量符合环保要求,可用来改良生物脱毒底泥、淤泥、淤泥质土、膨胀土、污染土、盾构渣土、风化泥岩、煤矸石和充填体,或用于制备碱渣土和复合胶凝材料. 现有的碱渣应用方法存在碱渣消耗量低、应用场景受限、无法固化Cl、锈蚀钢筋、可能造成二次污染等弊端. 本文系统探究了连云港碱渣的基本性质,提出利用碱渣、水泥和粒化高炉矿渣(GGBS)制备碱渣轻质土(A-LS),A-LS具有强度高、密度低、耐久性优良、生产工艺简单、生产效率高和造价低等优势;28 d抗压强度为0.96~4.27 MPa,可用作路基填料;碱渣用量高达87.01~164.35 kg·m−3,可大规模消纳碱渣,实现碱渣的高值化利用.

     

    Abstract: Alkali residue is a byproduct of the ammonia-soda process used to produce soda, characterized by high production volume, low utilization efficiency, high moisture content, high porosity, and fine particle size. The primary disposal methods for alkali residue include surface stacking (e.g., constructing tailing dams) and direct discharge into water bodies such as rivers or seas. The hazards associated with surface stacking include land resource occupation, reduced agricultural yield, groundwater and air contamination, soil pollution, adverse effects on vegetation growth, ecological imbalance, and the formation of saline-alkali land. Additionally, the discharge of alkali residue into rivers or seas can lead to water pollution, threatening the sustainability of aquatic ecosystems. Sedimentation may also occur, potentially blocking river channels, reducing flow cross-sections, and significantly impairing the river’s flood discharge capacity. These challenges have resulted in a large-scale accumulation of alkali residue, severely constraining the development of the soda industry. Therefore, there is an urgent need to accelerate its large-scale application. This study provides a comprehensive review of the latest research findings on the fundamental properties and engineering applications of alkali residue. The results indicate that similar to soil, alkali residue exhibits a three-phase system, where the solid phase, composed of various mineral components, forms a skeletal structure. In contrast, the liquid and gas phases fill the pores, creating a porous medium. The properties of alkali residue can be characterized using soil indicators. Its mineral composition includes CaCO3, CaSO4, CaCl2, and NaCl, where CaCO3 and CaSO4 are insoluble salts, while CaCl2 and NaCl readily dissolve in water. The CaCO3 content ranges from 32.52% to 64.00%, while the chemical composition is dominated by CaO, accounting for 32.25% to 74.20%. Alkali residue solutions are slightly alkaline, with pH values typically ranging from 8 to 12. As a general industrial solid waste, alkali residue contains heavy metals such as copper, zinc, cadmium, lead, total chromium, and chromium, all of which meet environmental standards. Alkali residue has been explored for various engineering applications, including the remediation of bioleached heavy metal-laden sediment, sludge, clay, expansive soil, contaminated soil, shield tunneling slag, weathered mudstone, and coal gangue, as well as for backfill materials and the preparation of alkali residue-based soil and composite cementitious materials. However, current application methods suffer from low alkali residue utilization efficiency, limited application scenarios, challenges in Cl- solidification, potential steel reinforcement corrosion, and risks of secondary pollution. To address these challenges, the author systematically investigates the fundamental properties of alkali residue from Lianyungang and proposes a method for producing alkali residue-based lightweight soil (A-LS) by combining alkali residue, cement, and granulated blast furnace slag (GGBS). A-LS was utilized as a roadbed filler in the Lianyungang—Suqian expressway, demonstrating compressive strength, California bearing ratio (CBR), rebound modulus, and deflection that met design and specification requirements. The material exhibited strong road performance, high resistance to wet-dry cycling, freeze-thaw cycling, and sulfate corrosion, with a durability coefficient ranging from 0.71 to 1.51. Furthermore, A-LS offers several advantages, including high strength, low density, a simple production process, high efficiency, and low cost. With a 28-day compressive strength ranging from 0.96 to 4.27 MPa, A-LS is suitable as a subgrade filling material. The alkali residue content in A-LS ranges from 87.01 to 164.35 kg·m−3, facilitating large-scale disposal and high-value utilization of alkali residue.

     

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