Fault Analysis and Innovation in Slag Discharge System of 440-t/h CFB Boiler

CFB boilers have been widely used in China in recent years with their perfect performances in coal adaptability, load variation capability and lower pollutant emission. The No.3 135-MW CFB unit in Lianzhou Power Plant is the f irst 440-t/h series CFB unit in Guangdong Province. It f inished 72-hour trial operation in Feb. 2004 and was transferred to trial operation. During the trial operation and the next commercial operation, there were some problems happened in the boiler slag discharging system, seriously affecting the safe and reliable operation and the loading capability. After innovation, these problems have been completely solved. Hopefully the solutions may be used for reference to the units with similar problems.

Characteristics of Phosphorus Adsorption with Boiler Slag and Process Optimization

[Objective] This study aimed to investigate the characteristics of phosphorus adsorption on boiler slag and optimize the adsorption process. [Method] Boiler slag was used as an adsorbent in the single-grade adsorption process to dispose the rural domestic sewage. During the course, phosphorus adsorption kinetics and thermodynamics, adsorption operating curve and the minimum boiler slag dosage were analyzed and calculated. [Result] Langmuir adsorption isotherm could be applied to describe the absorption of phosphorus with boiler slag, and the absorption kinetics was confirmed with the pseudo second-order equation. The maximum absorption quantity and the initial absorption rate increased with the rise of temperature, reaching up to 0.159 1 mg/g and 0.169 8 mg/(g·min) respectively at 40 ℃. Thermodynamic variables ΔG0<0 and ΔH0>0 indicated that the entire process was a spontaneous endothermic reaction, and high temperature would facilitate the reaction of absorption. In the single grade adsorption, the minimum adsorbent dosage decreased as the temperature rose; at 40 ℃ the optimum mass ratio of boiler slag to wastewater was 3.31 kg/m3. [Conclusion] The adsorption process with boiler slag as adsorbent is an economical and effective approach for treating rural domestic sewage.

Extraction of Aluminum and Iron from Boiler Slag by Sulfuric Acid

This paper presents a new method of recycling aluminum and iron in boiler slag derived from plants that use coal as fuel. The new method integrates efficient extraction and reuse of the leached pellets together. An elemental analysis of aqueous solutions leached by sulfuric acid was determined by EDTA-Naz-ZnCl2 titration method. The components and microstructures of the samples were examined by means of XRF, XRD and SEM. An aluminum extraction efficiency of 86.50% was achieved when the sintered pellets were leached using 4 mol · L^- 1 H2SO4 at solid/ liquid [m（g）/V（mL）] ratio of 1 ： 5 at 80 ℃ for 24 h. An iron extraction efficiency of 94.60% was achieved in the same conditions for the maximum extraction efficiency of Al. The extraction efficiencies of Al and Fe increased with an increase in temperature, leaching time and acidity. The concentration of alumina and iron hydroxide in the final product was determined to be 99.12% and 92.20% respectively. This product of alumina would be used directly for the production of metallic aluminum.

Extraction of Metals from Boiler Slag by Sintering

A new method of recycling aluminum and iron in boiler slag derived from plants that use coal as fuel was presented. The new method can integrate efficient extraction and reuse of the leached pellets together. An elemental analysis of aqueous solutions leached by sulfuric acid was conducted by the EDTA-Na2-ZnCl2 titration method, and the components and microstructures of the samples were examined by means of XRF, XRD and SEM. An aluminum extraction efficiency of 86.50% was achieved when the sintered pellets were leached using 4 mol·L-1 H2SO4 with solid/liquid ratio（m/V） of 1∶5 at 80 ℃ for 24 h. An iron extraction efficiency of 94.60% was achieved under the same condition for the maximum extraction efficiency of Al. The extraction efficiency of Al and Fe increased with temperature, leaching time and acidity. The concentration of alumina and iron hydroxide in the final product was determined to be 99.12% and 92.20% respectively. This product of alumina would be used directly for the production of metallic aluminum.