Strict screening and pretreatment of raw materials
Raw material quality control
The quality of raw materials directly determines the quality and production efficiency of carbonized products. For biomass raw materials, varieties with high density and high lignin content are preferred, such as hardwood oak and pine. Carbon products made from these raw materials usually have higher fixed carbon content and calorific value. If agricultural waste is being processed, it must be ensured that there is no obvious mildew or decay, otherwise it will reduce the quality of the carbonized product and may also produce odor and harmful gases during the production process. Resolutely avoid using raw materials that are mixed with too many impurities and have too high water content. Impurities will damage the equipment, and high water content will prolong the drying time, increase energy consumption, and even affect the carbonization effect.
Crushing and screening
Crushing the raw materials to the appropriate particle size is an important step to ensure uniform carbonization. Generally speaking, it is more appropriate to control the particle size of the crushed material to 2-4cm. Screening equipment is used to remove oversized or undersized particles. Oversized particles may not be completely carbonized, while undersized particles may cause material accumulation, affect air permeability and heat transfer. Raw materials with uniform particle size can be heated evenly during the carbonization process, thereby improving the consistency of carbonization and product quality.
Drying treatment
Drying is an indispensable part of batch carbonization production. Special dryers such as drum dryers and airflow dryers are used to reduce the moisture content of the raw materials to less than 15%. During the drying process, the temperature and time are strictly controlled. The temperature is generally controlled at 100-150℃, and the time is determined according to the initial moisture content of the raw materials and the performance of the equipment, usually 1-3 hours. If the temperature is too high or the time is too long, it is easy to cause the raw materials to burn or deteriorate; if the temperature is too low or the time is too short, the drying effect is poor, which will affect the subsequent carbonization process.
Careful selection and maintenance of equipment
Carbonization equipment matching
According to the production scale, raw material characteristics and product requirements, it is crucial to accurately select the right carbonization equipment. Continuous carbonization furnaces are suitable for large-scale production due to their continuous production and high production efficiency; while earthen kilns or small intermittent carbonization furnaces have the advantages of high flexibility and low investment cost, and are more suitable for small-scale production or situations with special requirements for products. For example, the production of high-quality activated carbon may require the selection of advanced carbonization equipment that can accurately control temperature and atmosphere.
Equipment maintenance
Regularly conduct a comprehensive inspection of the carbonization furnace, including whether the furnace structure is damaged, whether the sealing performance is good, whether the heating system is operating normally, and whether the temperature control system is accurate. Repair or replace problematic parts in a timely manner to ensure that the equipment operates in the best condition. For auxiliary equipment such as conveying devices and fans, routine inspections and maintenance are also required, such as regularly adding lubricating oil to the chains of the conveying devices and cleaning the filters of the fans to ensure the stable operation of the entire production system.
Precise control of the carbonization process
Temperature control
Temperature is the core parameter of the carbonization process. The carbonization temperature of different materials varies. Generally, the carbonization temperature of biomass is between 400 and 1000℃. The intelligent temperature control system can accurately control the heating rate and insulation time according to the set program. In the heating stage, slow and uniform heating can avoid cracks or deformation of the material due to rapid heating; the insulation stage ensures that the material is fully carbonized. At the same time, pay close attention to the temperature distribution in the furnace to prevent local overheating or excessive temperature fluctuations, which will lead to uneven carbonization.
Atmosphere control
Batch carbonization production is usually carried out in anoxic or micro-oxygen environment to prevent complete combustion of raw materials. The atmosphere in the furnace is accurately controlled by adjusting the air intake, exhaust volume and gas composition. For example, in some carbonization processes, a certain proportion of nitrogen or carbon dioxide needs to be introduced into the furnace to create an inert atmosphere, promote the pyrolysis reaction, and improve the quality and yield of carbonized products.
Time control
The carbonization time varies from tens of minutes to hours depending on the type of raw materials, particle size, equipment performance and other factors. Through a large number of tests and production practices, the optimal carbonization time parameters for each raw material are explored and strictly controlled during the production process. Too short carbonization time will lead to incomplete carbonization and unqualified product quality; too long carbonization time will reduce production efficiency and increase energy consumption.
Feeding and discharging control
Ensuring continuous and uniform feeding is the key to maintaining stable production. Use automated feeding equipment, such as screw feeders, belt conveyors, etc., and equip them with precise metering devices to ensure the stability of feeding speed and amount. When discharging, the carbonized product is quickly cooled, and forced cooling methods such as air cooling and water cooling are used to prevent high-temperature products from spontaneous combustion or oxidation when in contact with air. At the same time, the discharging system is reasonably designed to ensure smooth discharging and avoid material blockage.
Strict implementation of environmental protection and safety measures
Waste gas treatment
A large amount of waste gas is generated during the batch carbonization production process, including dust, tar, and harmful gases (such as sulfur dioxide, nitrogen oxides, etc.). Install efficient waste gas purification equipment, such as cyclone separators, bag dust collectors, activated carbon adsorption devices, desulfurization and denitrification equipment, etc., to treat the waste gas in multiple stages. Cyclone separators and bag dust collectors can effectively remove dust from waste gas, activated carbon adsorption devices can adsorb harmful gases and tar, and desulfurization and denitrification equipment is used to reduce the content of sulfur oxides and nitrogen oxides in waste gas, so that the waste gas can meet the national emission standards before being discharged.
Wastewater treatment
Wastewater generated during the carbonization process needs to be collected and centrally treated. Wastewater may contain pollutants such as organic matter and heavy metals. Pollutants in wastewater are removed by precipitation, filtration, biological treatment and other methods. For example, large particles of impurities in wastewater are removed by precipitation, and fine particles are further removed by filtration. Biological treatment uses the action of microorganisms to decompose organic matter in wastewater, so that wastewater can be safely discharged after meeting the emission standards.
Safety operation specifications
Develop a complete safety operation procedure. Operators must undergo professional training and be familiar with the equipment operation methods and safety precautions. Set up obvious safety warning signs around the equipment to remind personnel to pay attention to safety. Equipped with complete fire-fighting equipment, such as fire extinguishers, fire hydrants, etc., and conduct fire drills regularly to improve employees’ emergency response capabilities. During the operation of the equipment, illegal operations are strictly prohibited to prevent the occurrence of safety accidents such as fire and explosion.
Full implementation of product quality inspection and control
Quality inspection indicators
Establish a comprehensive product quality inspection system to strictly inspect the basic indicators of carbonized products such as fixed carbon content, volatile matter, ash content, moisture, and calorific value. The fixed carbon content determines the combustion performance and calorific value of the product, the volatile matter reflects the content of volatile components in the product, the ash content affects the purity of the product and the amount of residue after combustion, and the moisture and calorific value are directly related to the use effect of the product. According to the purpose of the product, it is also necessary to test its adsorption performance, particle size distribution, mechanical strength and other special indicators. For example, activated carbon products used for adsorption have high requirements for their adsorption performance.
Process quality control
During the production process, regular quality inspections are conducted on raw materials, intermediate products and finished products to promptly identify and resolve quality problems. Raw materials are inspected to ensure that they meet production requirements; intermediate products are inspected to monitor whether the carbonization process is normal; finished products are fully inspected to ensure that product quality is qualified. A quality traceability system is established to record various data during the production process. Once a product has a quality problem, the source of the problem can be quickly traced back and corresponding measures can be taken to improve it.
The technical points of batch carbonization production cover the entire process from raw materials to products. Only by strictly controlling the technical points in each link can efficient, environmentally friendly and safe batch carbonization production be achieved, high-quality carbonization products can be produced, market demand can be met, and the sustainable development of related industries can be promoted.
