Cradle to Gate
Identity ID
d882e3bf-3fe5-43dd-865d-d76f7d3e4f22
Materials
Associated ID
fc910caf-a519-47ef-bb24-3987da35ffad
Included activities starts
Included activities ends
Description
This dataset represents a life cycle inventory (cradle-to-gate) for the production of middlings from coal preparation processes, covering all coal washing-related activities. It excludes conditions external to the coal preparation plant (such as raw coal mining and utilization of Clean coal), as well as direct or indirect greenhouse gas emissions resulting from staff commuting and routine office operations during the coal washing process. Based on national standards including the "Cleaner Production Standard for the Coal Mining and Preparation Industry" (HJ 446-2008) and the "Emission Standards of Pollutants for the Coal Industry", the dataset is compiled from multiple data sources and reflects the average production level in China.
Activity Description
Coal preparation refers to the process of removing shale and other impurities from coal through various physical, chemical, or physicochemical methods to improve coal quality. The following 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 into particles suitable for coal preparation by crushers. The crushed coal then enters screening equipment for particle size classification, directing coal of different sizes to corresponding coal preparation equipment.
The screening process can be divided into several stages to ensure that coal of different sizes receives optimal treatment. Pre-selection
Impurity removal equipment:
Before formal coal beneficiation, magnetic separators, iron removers, and other equipment are used to remove metal impurities and large gangue pieces from raw coal.
The goal of the pre-selection stage is to reduce the impurity content entering subsequent coal beneficiation processes and to improve coal beneficiation efficiency.
3. Jig Coal Washing
Jigging Separation:
Coarse coal is separated using a jigging machine. The jig utilizes the pulsating action of water to stratify coal and impurities based on density. The lower-density clean coal rises to the upper layer, while higher-density gangue and impurities sink to the lower layer.
Coal enters the feed hopper of the jig and is mixed with water to form a slurry. Under the action of the jig, clean coal and impurities are stratified. The clean coal is collected via an overflow chute or discharge device, while the impurities are discharged through the discharge outlet. Dense Medium Coal Preparation
Dense medium separation:
Medium-sized coal is separated using a dense medium separator. In a dense medium suspension, coal with lower density floats, while impurities with higher density sink, achieving separation between coal and impurities.
Magnetite powder or other dense medium materials are mixed with water to form a suspension of specified density. After separation, the dense medium suspension is processed through a magnetic separator to recover the magnetite powder for recycling.
5. Flotation Coal Preparation
Grinding:
Fine-sized coal must be further ground to achieve a particle size suitable for flotation (typically 0. particles smaller than 1 mm).
Froth flotation sorting:
The ground coal powder is mixed with water to form a slurry, into 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 then collected to obtain high-purity clean coal. Coking coal processing
Dewatering:
After coal preparation processes such as jiggering, heavy medium separation, and flotation, the resulting clean coal contains a certain amount of moisture. It is therefore necessary to dewater the coal using dewatering equipment (e.g., dewatering screens, centrifuges, or filter presses) to reduce moisture content and improve the quality of the clean coal.
Storage and transportation:
The dewatered clean coal must be properly stored and transported. To prevent moisture absorption and spontaneous combustion during storage and transportation, protective measures should be implemented, such as storing the coal in coal sheds or enclosed stockyards. Tailings Management
Tailings Disposal:
Tailings (mainly gangue and impurities) generated during the coal beneficiation processes such as jigging, heavy medium separation, and flotation are discharged through discharge equipment and transported to the tailings management area.
Tailings Dewatering and Wastewater Treatment:
The moisture contained in the tailings must be further treated. After dewatering using thickeners or filters, solid tailings are either stored or subjected to further processing. Wastewater generated during the flotation process is treated for recycling or discharged in compliance with environmental regulations, thereby minimizing environmental pollution.
8. Environmental Protection and Safety Measures
Environmental Protection Measures:
Coal preparation plants should implement environmental protection measures such as dust control and wastewater treatment to minimize environmental impact. Treated wastewater can be reused or discharged in compliance with regulatory standards, thereby reducing water consumption.
Safety Measures:
Establish and enforce safety production regulations, conduct regular safety inspections and training, and equip facilities with protective devices and emergency response systems to ensure worker safety.
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
Not specified