Cradle to Gate
Identity ID
4e88b3fc-eae3-42d2-a04c-94d668df2dcd
Materials
Associated ID
b69dac8d-5883-479f-9b4e-1abd0e805bb8
Included activities starts
Included activities ends
Description
This dataset represents the life cycle inventory (cradle-to-gate) of the entire process of producing middlings coal as a by-product of power coal through combined coal preparation technologies, including heavy middlings separation, jigging, and flotation. It covers all activities associated with coal washing, but excludes external factors beyond the coal preparation plant (e.g., raw coal mining, utilization of Clean coal), as well as direct or indirect greenhouse gas emissions from personnel commuting and daily operations during the coal washing process. The dataset is compiled based on Chinese national standards such as "Cleaner Production Standard for the Coal Mining and Washing Industry" (HJ 446-2008) and "Emission Standards of Pollutants for the Coal Industry", integrating data from multiple sources to represent the average production level in China.
Activity Description
This dataset describes three efficient coal preparation processes: dense medium coal separation, jig coal separation, and flotation coal separation. When used in combination, these methods can better handle coal of different particle sizes and qualities, thereby improving coal separation efficiency. Below is a detailed description and introduction of the entire production process of the integrated dense medium, jig, and flotation coal preparation:
1. Raw Coal Preparation
Coal Crushing and Screening:
Raw coal is crushed by crushers into particles suitable for dense medium separation, jigging, and flotation. Typically, coarse-sized coal (>50 mm) undergoes jig separation, medium-sized coal (0.5–50 mm) is processed by dense medium separation, and fine-sized coal (<0. 5 mm) coal are subjected to flotation separation. The crushed coal is classified by particle size through screening equipment, and coal of different particle sizes is sent to corresponding coal preparation equipment. 2. Heavy Medium Separation
Preparation of heavy medium suspension:
Mix magnetite powder or other heavy medium materials with water to prepare a heavy medium suspension of a specific density. The density of the suspension is adjusted according to the density difference between coal and impurities.
Coal separation:
Medium-sized coal is separated using a heavy medium separator. In the heavy medium suspension, coal with lower density floats, while impurities with higher density sink, thereby achieving separation of coal and impurities.
The light product (clean coal) and heavy product (impurities) are discharged through separate outlets.
Recovery of heavy medium:
The heavy medium suspension is processed through a magnetic separator after separation to recover the magnetite powder for recycling. The recycled dense medium material is reintroduced into the preparation stage.
3. Jigging Separation
Jig Preparation:
Coarse-sized coal is separated in a jig, where pulsating water is used to stratify coal and impurities based on density. The lighter clean coal rises to the upper layer, while the heavier gangue and impurities settle to the lower layer.
Separation Process:
Coal enters the feed hopper of the jig and mixes with water to form a slurry. Under the action of the jig, the clean coal and impurities are stratified. The clean coal is collected via an overflow trough or discharge device, while the impurities are discharged through a tailings outlet.
4. Flotation separation
Grinding:
The medium and fine coal particles need to be further ground to achieve a suitable size for flotation (typically below 0.1 mm) before entering the flotation machine.
Flotation reagent addition:
The ground coal powder is mixed with water to form a slurry. After adding flotation reagents (such as collectors, frothers, and modifiers), it is fed into the flotation cell.
Flotation process:
Inside the flotation cell, bubbles are generated through mechanical agitation and air injection. Coal particles attach to the bubbles and rise to the surface of the slurry, forming a froth layer. The froth layer is collected to obtain high-purity clean coal. Coal Preparation
Dewatering Treatment:
After coal preparation methods such as dense medium separation, jigging, and froth flotation, the cleaned coal still contains a certain amount of moisture. It must undergo dewatering treatment using dewatering equipment (e.g., dewatering screens, centrifuges, or filter presses) to reduce moisture content and improve the quality of the cleaned coal.
Storage and Transportation:
The dewatered cleaned coal is stored and transported. To prevent moisture absorption and spontaneous combustion during storage and transportation, protective measures must be implemented, such as storing coal in coal sheds or enclosed stockyards. Tailings Management
Tailings Discharge:
The tailings generated during the dense medium separation, jigs, and flotation coal preparation processes (mainly gangue and impurities) are discharged through discharge equipment and transported to the tailings management area.
Tailings Dewatering and Wastewater Treatment:
The moisture in the tailings requires further processing. After dewatering using thickeners or filters, the solid tailings are stored or subjected to further treatment. The wastewater generated during the flotation process is treated for recycling or discharged in compliance with environmental standards to minimize 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
The combined coal preparation process using dense medium separation, jigging, and flotation is an efficient and flexible coal beneficiation technology. By integrating dense medium separation, jigging, and flotation, it can effectively process coal of different particle sizes and qualities. The production process includes coal crushing and screening, dense medium separation, jigging separation, flotation separation, clean coal treatment, and tailings management. This technology significantly enhances coal purity and utilization efficiency, offering high processing capacity, high separation efficiency, and environmental friendliness, making it widely used in coal preparation plants.