Cradle to Gate
Identity ID
c6431a24-b7c9-48e3-b80d-2b9dcae7eaa5
Materials
Associated ID
c3b7b6ed-c604-4a9e-b76b-99a2a460635a
Included activities starts
Included activities ends
Description
This dataset represents the life cycle inventory (cradle-to-gate) of coal from the start of flotation coal preparation to the production of middlings from thermal coal, covering all activities related to coal washing. However, it excludes external aspects outside the coal preparation plant (such as raw coal mining and final use of Clean coal), as well as direct or indirect greenhouse gas emissions arising from staff transportation and daily office operations during the coal washing process. The dataset, compiled from multiple data sources in accordance with national standards such as "Cleaner Production Standard for Coal Mining and Washing Industry" (HJ 446-2008) and "Emission Standards of Pollutants for the Coal Industry", is representative of the average production level in China.
Activity Description
This dataset describes coal flotation, a process that separates coal from impurities through physical and chemical methods, particularly suitable for fine particle size coal. The specific process is as follows:
1. Raw Coal Preparation
Coal crushing and screening:
Raw coal is crushed into particles suitable for flotation, typically below 0.5 mm in size, using crushers. The crushed coal then enters screening equipment for particle size classification, ensuring uniformity in the flotation process.
2. Grinding
Grinding equipment:
Grinding equipment (such as ball mills, rod mills, etc.) is used to further grind the coal to the fineness required for flotation, typically below 0.1 mm.
3. Flotation
Flotation Reagent Addition:
Based on the differences in physicochemical properties between coal and impurities, suitable flotation reagents are selected, including collectors, frothers, and modifiers. Collectors enhance the hydrophobicity (oil affinity) of coal surfaces, facilitating their attachment to bubbles; frothers generate stable foam; modifiers adjust the pH of the slurry to enhance flotation efficiency.
Flotation Cell:
Finely ground coal powder is mixed with water to form a slurry, which, along with flotation reagents, is fed into the flotation cell. Inside the flotation cell, mechanical agitation and air injection generate numerous bubbles. Coal particles attach to these bubbles and rise to the surface of the slurry, forming a froth layer.
4. Flotation Product Processing
Froth Product Collection:
A froth layer forms on the surface of the flotation cell as bubbles carrying coal fines rise. The froth product is collected via overflow launders or mechanical scrapers. This froth product contains high-purity clean coal.
Froth Product Dewatering:
The collected froth product contains significant moisture and must be dewatered using dewatering equipment (such as thickeners, filters, or centrifuges) to reduce moisture content and improve the quality of the clean coal.
5. Tailings Management
Tailings Discharge:
Impurities and some coal fines that fail to float during the flotation process remain at the bottom of the flotation cell and are referred to as tailings. These tailings are discharged through an outlet to a tailings pond for further treatment.
Tailings Dewatering and Wastewater Treatment:
The moisture contained in the tailings requires further processing. After dewatering using thickeners or filter presses, the solid tailings are either stored or subjected to further treatment. The wastewater generated during the flotation process is treated for recycling or for discharge in compliance with environmental standards, thereby minimizing environmental pollution.
Process Description
Thermal coal refers to coal used as a power source. In a narrow sense, it specifically refers to coal used for thermal power generation. Broadly speaking, any coal used for generating power—such as for electricity generation, locomotive propulsion, or boiler combustion—is classified as thermal coal. Among thermal coal products, medium coal (zhongmei) is an intermediate material between clean coal and gangue. Its quality is inferior to clean coal, containing certain amounts of impurities such as ash and sulfur, but it is better than gangue and still possesses a certain level of calorific value. Medium coal typically contains a relatively high proportion of ash and can be used in industrial boilers where coal quality requirements are not particularly high.
Time period
2022
2026
Geography
China
Geography comment
Forming China's average data through merging data from multiple sources.
Macroeconomic value
Business-as-Usual
Data validation
Yes
Technology
Current Technology
Technology comment
Froth coal flotation is an important method for cleaning clean coal particles, achieving efficient separation of coal from impurities through steps such as crushing, grinding, reagent addition, flotation, product treatment, and tailings management. This process effectively enhances coal purity and utilization efficiency, offering strong adaptability and environmental benefits. It is widely applied in processing various types of coal, especially in the beneficiation of clean coal and slurry coal.