Cradle to Gate
Identity ID
68725410-101f-4e9a-a275-6180ebbcf5cf
Materials
Associated ID
ea8b2d07-283e-48a7-9afe-27f4b2f97a0f
Included activities starts
Included activities ends
Description
This dataset represents the life cycle inventory (cradle-to-gate) of the middlings of steam coal produced through a combined coal preparation process involving jigging and flotation, covering all activities associated with coal washing, but excluding conditions external to the coal preparation plant (e.g., raw coal mining, utilization of Clean coal), as well as direct or indirect greenhouse gas emissions from employee commuting and daily office operations during the coal preparation process. The dataset, compiled from multiple data sources in accordance with national standards such as the "Cleaner Production Standards for the Coal Mining and Washing Industry" (HJ 446-2008) and the "Emission Standards of Pollutants for the Coal Industry", is representative of the average production level in Shanxi.
Activity Description
This dataset describes combined jigging and froth flotation coal preparation, a process that integrates both jigging and froth flotation methods, primarily used for treating coals of different sizes and qualities to achieve optimal separation efficiency. Below is a detailed description and introduction of the entire production process of 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) will undergo 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 particle size using screening equipment, and coal of different particle sizes is sent to the corresponding coal beneficiation equipment. 2. Jigging Separation
Jig Preparation:
Coarse and medium-sized coal is separated using a jig. The jig utilizes pulsating 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.
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 are stratified; the clean coal is collected through an overflow chute or discharge device, while impurities are discharged through a tailings outlet. Flotation Separation
Grinding:
Coarse and fine coal particles need further grinding before entering the flotation machine to achieve a suitable size for flotation (typically below 0.1 mm).
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. This froth layer is collected to obtain high-purity clean coal. Coking coal processing
Dewatering:
After jigging coal preparation and froth flotation coal preparation, the clean 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 clean coal.
Storage and transportation:
After dewatering, the clean coal is stored and transported. To prevent moisture absorption and spontaneous combustion during storage and transportation, protective measures are required, such as using coal sheds or sealed stockyards for storage. Tailings Management
Tailings Disposal:
The tailings generated during jigging and flotation processes (primarily gangue and impurities) are discharged via discharge devices to a designated tailings management area.
Tailings Dewatering and Wastewater Treatment:
The moisture contained in the tailings is further treated through thickeners or filters for dewatering. The solid tailings are then stockpiled or subjected to further processing. Wastewater generated during the flotation process is treated for recycling or discharged in compliance with environmental standards, thereby minimizing environmental pollution.
Process Description
Shanxi Province's steam coal is widely distributed in the Taiyuan Formation, Shanxi Formation, and Datong Formation. The Taiyuan and Shanxi Formations are primarily anthracite and lean coal, while the Datong Formation is mainly weakly caking coal. The Taiyuan Formation has ash content ranging from 12.62% to 28.52%, volatile matter from 6.5% to 14.79%, maximum thickness of vitrinite layer at 0 mm, total sulfur in raw coal from 1.2% to 6.65%, and net calorific value on an as-received basis (Qnet,ar) between 8136 and 8749 kcal/kg. The Shanxi Formation has ash content ranging from 8% to 35%, volatile matter in raw coal from 6.4% to 16.6%, maximum thickness of vitrinite layer from 0 to 12 mm, and total sulfur in raw coal from 0.2% to. 92%, with Qnet,ar (as-received net calorific value) ranging from 8350 to 8577 kcal/kg. Datong coal group: raw coal ash content 8.56–16.13%, refined coal volatile matter 29.73–35.52%, maximum thickness of the vitrinite layer 0 mm, total sulfur content in raw coal 0.49–1. 93%, with a net calorific value (Qnet,ar) of 7705~7946 kcal/kg. Among thermal coal, middlings are a byproduct intermediate between clean coal and gangue. Their quality is inferior to clean coal, containing certain amounts of impurities such as ash and sulfur, yet better than gangue, still possessing a certain level of calorific value. Middlings typically have a relatively high ash content and can be used in industrial boilers and other applications where coal quality requirements are not particularly high.
Time period
2022
2026
Geography
China,Shanxi
Geography comment
Forming Shanxi'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.