Cradle to Gate
Identity ID
7837d772-6a2d-4ea5-9d75-8b019ca96454
Materials
Associated ID
f48fc3c2-a37e-4cd5-8247-45748209235c
Included activities starts
Included activities ends
Description
This dataset represents the life cycle inventory (cradle-to-gate) of middlings produced from coal preparation, covering all activities related to coal washing, but excluding external conditions 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 office operations during the coal washing process. Based on 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", the dataset was compiled from multiple data sources and is representative of the average production level in China.
Activity Description
Coal preparation refers to the process of removing gangue and other impurities from coal through various physical, chemical, or physicochemical methods, thereby improving coal quality. Below is a detailed description and introduction of the entire coal preparation production process in China:
1. Raw Coal Preparation
Coal crushing and screening:
Raw coal is first crushed by crushers into particles suitable for coal preparation. The crushed coal then enters screening equipment for particle size classification, where coal of different sizes is directed to corresponding coal preparation equipment.
The screening process can be divided into several stages to ensure optimal treatment for coal of different particle sizes.
2. Pre-selection
Tailing removal equipment:
Before formal coal washing, magnetic separators, iron removers, and other equipment are used to remove metallic impurities and large gangue pieces from raw coal.
The goal of the pre-selection stage is to reduce the impurity content entering subsequent coal washing processes, thereby improving coal washing efficiency.
3. Jig Coal Washing
Jigging Separation:
Coarse coal is separated using a jigger. The jigger utilizes the pulsating action of water to stratify coal and impurities based on density. The lighter clean coal rises to the upper layer, while the heavier gangue and impurities sink to the lower layer.
Coal enters the feed hopper of the jigger and mixes with water to form a slurry. Under the action of the jigger, the clean coal and impurities stratify. The clean coal is collected through an overflow trough or discharge device, while the impurities are discharged through the discharge outlet.
4. Heavy Medium Coal Washing
Heavy medium separation:
Medium-sized coal is separated through a heavy medium separator. In a heavy medium suspension, coal with lower density floats, while impurities with higher density sink, achieving separation of coal and impurities.
Magnetite powder or other heavy medium materials are mixed with water to prepare a heavy medium suspension of a specific density. After separation, the heavy medium suspension passes through a magnetic separator to recover the magnetite powder for recycling.
5. Flotation Coal Washing
Grinding:
Fine-sized coal needs to be further ground before entering the flotation machine to reach a particle size suitable for flotation (typically 0. Less than 1 mm).
Froth flotation:
After grinding, the fine coal powder is mixed with water to form a slurry, to which flotation reagents (such as collectors, frothers, and modifiers) are added, and then fed into flotation cells. Through mechanical agitation and air injection, bubbles are generated. 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.
6. Coking coal processing
Dewatering:
After processing by jig coal washing, heavy medium coal washing, or flotation coal washing, the clean coal contains a certain amount of moisture. It needs to be dewatered using dewatering equipment (such as dewatering screens, centrifuges, or filter presses) to reduce moisture content and improve the quality of clean coal.
Storage and transportation:
The dewatered clean coal is stored and transported. To prevent moisture absorption and spontaneous combustion during storage and transportation, protective measures should be taken, such as storing in coal sheds or enclosed stockyards.
7. Tailings Management
Tailings Discharge:
The tailings (mainly gangue and impurities) generated during jigging, dense medium separation, and flotation coal preparation processes are discharged through outlet devices and transported to the tailings management area.
Tailings Dewatering and Wastewater Treatment:
The moisture contained in the tailings requires further treatment. After dewatering using thickeners or filters, solid tailings are either stockpiled or subjected to further processing. The wastewater generated during flotation is treated for reuse in circulation or discharged in compliance with environmental standards, thereby minimizing environmental pollution.
8. Environmental Protection and Safety Measures
Environmental Protection Measures:
The coal preparation plant should implement environmental protection measures such as dust control and wastewater treatment to reduce environmental impacts. Treated wastewater can be reused or discharged in compliance with environmental standards, thereby reducing water consumption.
Safety Measures:
Establish and implement safety production regulations and systems, conduct regular safety inspections and training, equip protective devices and emergency response systems to ensure worker safety.
Process Description
Medium coal is an intermediate product separated in coal preparation plants, with ash content lower than clean coal but higher than coal gangue, and is mostly used as boiler fuel in power plants.
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
Not specified