Sustainable preparation of high-calorific value and low-N and S energy products through the low-temperature alkali fusion of coal gasification fine ash

Adsorption performance of mineral-carbon adsorbents derived from coal gasification fine ash: Prepared via low-temperature alkali fusion method

To address the solid waste challenges associated with coal gasification fine ash, this study conducted a low-temperature alkali fusion de-ashing treatment to transform coal gasification fine ash into mineral-carbon adsorbent. The preparation process was simplified without grinding, carbonization and high-temperature (500-800 °C) activation treatment. The results demonstrate a positive linear correlation between the ash removal rate of the samples (measured during the preparation process, i.e., low-temperature alkaline fusion treatment of coal gasification fine ash) and their maximum equilibrium adsorption capacity for methylene blue. For the samples with an ash removal rate of 95.71 %, which exhibit a maximum adsorption capacity of 161.36 mg/g for methylene blue. The adsorption behavior of methylene blue on mineral-carbon adsorbent was a monolayer adsorption on the surface of homogeneous medium, involving both physical and chemical adsorption. The main adsorb rate-controlling steps for the samples with ash removal rates of 27.91-59.33 % and 95.71 % were the intra particle diffusion process and the liquid film diffusion process, respectively. The adsorption mechanism of methylene blue on the surface of mineral-carbon adsorbent involved electrostatic attraction and hydrogen bonding. The aforementioned results demonstrated the potential of coal gasification fine ash as an adsorbent material, providing new options for promoting the resource utilization and high-value applications of coal gasification fine ash.

Experimental Studies on the Combustion Characteristics of Multisource Organic Solid Waste for Collaborative Disposal Using Municipal Solid Waste Incinerators

This study investigated the evolution of furnace conditions during the heat conversion process of multisource organic solid waste. To achieve this, combustion tests involving different sludge mixing ratios, variable load operation, and multisource organic solid waste collaborative disposal were performed on a 750 t/d new municipal solid waste incineration grate furnace. The test results revealed that as the sludge mixing ratios increased from 0 to 10 and 20%, the temperature level in the furnace decreased and the fuel-type NOx emission increased. Moreover, the sludge featured poor combustion stability under low-load conditions owing to fluctuations in its calorific value and moisture content. Field tests of multisource organic solid waste revealed that after mixing waste cloth strips and papermaking waste, the temperature level in the furnace increased. Additionally, the emissivity distribution was positively correlated with the furnace flame temperature distribution, and NOx emissions also increased. The overall results indicated the feasibility of controlling the mixing rate of different organic solid wastes in the municipal solid waste incinerator within a reasonable range for cooperative incineration.

Recovery of residual carbon from coal gasification fine slag by a combined gravity separation-flotation process

Recovering inner residual carbon is important for fully utilizing coal gasification fine slag (CGFS) resources. In this study, we adopted a combined gravity-separation and flotation process to efficiently recover residual carbon by considering the characteristics of the CGFS and optimizing the operating factors of the process. CGFS is principally a mixture of residual carbon and ash, with low-density particles containing more of the former. Accordingly, residual carbon is preliminarily enriched by gravity separation, in which gas velocity (vg) and water velocity (vw) significantly impact separation efficiency, followed by feed volume (m). The residual carbon in the initial concentrate was preliminarily enriched (i.e., loss on ignition (LOI): 55.90%; combustible recovery (Ro): 72.36%) under appropriate operating conditions (i.e., vw = 0.04 m/s, vg = 3 m/s, m = 150 g). Moreover, the quality of the flotation concentrate was most influenced by collector dosage (mc), followed by aeration rate (η), frother dosage (mf), stirring speed (w), and grinding time (t) during flotation of the primary concentrate. The flotation concentrate exhibited LOI and Ro values of 90.95% and 50.34%, respectively, under the optimal flotation conditions (i.e., mc = 20 kg/t, mf = 15 kg/t, w = 2600 rad/min, η = 200 L/h, t = 360 s); it has a high residual carbon content and is an ideal raw material for preparing fuels or carbon materials.