Cradle to Gate
Identity ID
c8621cb0-2f47-4989-9ff5-cfdc25411845
Materials
Associated ID
ea8b2d07-283e-48a7-9afe-27f4b2f97a0f
Included activities starts
Included activities ends
Description
This dataset represents a life cycle inventory (cradle-to-gate) of middlings produced through combined jigging and flotation coal preparation, covering all activities related to coal washing, but excluding conditions outside the coal preparation plant (e.g., raw coal mining, use of clean coal), as well as direct or indirect greenhouse gas emissions from personnel commuting and daily office operations during the coal preparation process. Based on national standards such as "Cleaner Production Standards 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 Shandong.
Activity Description
This dataset describes the combined coal preparation process of jigging and flotation, which integrates both jigging and flotation methods. It is primarily used to process coal of varying particle sizes and qualities to achieve optimal separation efficiency. Below is a detailed description and introduction of the entire production process of the combined jigging and flotation coal preparation:
1. Raw Coal Preparation
Coal Crushing and Screening:
Raw coal is first crushed by crushers into particles suitable for jigging and flotation. Generally, coarse-sized coal (above 50 mm) undergoes jigging separation, while fine-sized coal (0.5–50 mm) and slimes (below 0. are then subjected to flotation separation. The crushed coal is classified by size using screening equipment, and coal of different sizes is sent to the corresponding coal preparation equipment. Jigging Separation
Preparation of Jig Machine:
Coarse and medium-sized coal is separated through jigs. The jig utilizes pulsating water action to stratify coal from impurities based on density. Lighter clean coal rises to the upper layer, while denser 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, clean coal and impurities separate into layers. Clean coal is collected via overflow channels or discharge devices, while impurities are discharged through outlet ports.
3. Flotation Separation
Grinding:
The medium and fine coal particles need further grinding before entering the flotation machine to achieve a suitable particle size for flotation (typically below 0.1 mm).
Flotation Reagent Addition:
The ground coal powder is mixed with water to form a slurry, and flotation reagents (such as collectors, frothers, and modifiers) are added before being 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. Coking coal processing
Dewatering:
After jigging and flotation coal preparation, the coking coal contains a certain amount of moisture and needs to be dewatered using dewatering equipment (such as dewatering screens, centrifuges, or filter presses) to reduce moisture content and improve the quality of coking coal.
Storage and transportation:
Dewatered coking coal is stored and transported. To prevent moisture absorption and spontaneous combustion during storage and transportation, protective measures must be taken, such as storing in coal sheds or enclosed stockyards.
5. Tailings processing
Tailings disposal:
5. Tailings Management
Tailings Discharge:
The tailings generated during the jigging and flotation processes (mainly gangue and impurities) are discharged through discharge devices and transported to the tailings management area.
Tailings Dewatering and Wastewater Treatment:
The moisture contained in the tailings needs further processing. After dewatering using thickening or filtration equipment, the solid tailings are either stockpiled or subjected to further processing. The wastewater generated during the flotation process is treated for recycling or discharged in compliance with environmental standards, minimizing environmental pollution.
Process Description
Shandong Province's power coal is mainly lignite. After coal washing, washed lump coal has a total moisture content of less than 20%, ash content of 12–16%, volatile matter of 43–44%, total sulfur of 0.5%, and a net calorific value on an as-received basis (Qnet,ar) of 4128–5520 kcal/kg; washed mixed coal has a total moisture content of less than 21%, ash content of 14–28%, volatile matter of 44–53%, and total sulfur of 0.6–0.9%. 8%, and the net calorific value on an as-received basis (Qnet,ar) ranges from 3514 to 5018 kcal/kg. Among thermal coal, middlings are a product intermediate between clean coal and gangue. Their quality is inferior to clean coal, containing certain amounts of ash, sulfur, and other impurities, yet better than gangue, still possessing a certain level of calorific value. Middlings typically contain a relatively high proportion of ash and can be used in industrial boilers and other applications where coal quality requirements are not particularly stringent.
Time period
2022
2026
Geography
China,Shandong
Geography comment
Forming Shandong's average data through merging data from multiple sources
Macroeconomic value
Business-as-Usual
Data validation
Yes
Technology
Current Technology
Technology comment
Jigging and flotation combined coal washing is an efficient and flexible coal preparation process that effectively handles coal of different particle sizes and qualities by combining jigging and flotation methods. Its production process includes coal crushing and screening, jigging separation, grinding, flotation separation, clean coal processing, and tailings management. This process significantly improves coal purity and utilization efficiency, offering high processing capacity, high separation efficiency, and environmental friendliness, and is widely applied in coal preparation plants.