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What is a double-chamber lime kiln?
Dec 16,2024
The double-chamber lime kiln is a common lime production equipment, also known as a double-chamber lime kiln furnace. It is an energy-saving and environmentally friendly lime kiln furnace, mainly composed of two kiln chambers connected by a passage, allowing for heat exchange between the two chambers. One chamber is for calcination, while the other chamber stores heat, exchanging every 10-15 minutes, resulting in high-quality lime with high activity.
Structure of the double-chamber kiln
The double-chamber kiln consists of two adjacent circular kiln chambers, each with an independent combustion chamber. During production, limestone and combustion materials enter the kiln chamber from the top, where they react at high temperatures to produce lime and lime ash. The lime and lime ash are discharged from the bottom, while limestone and combustion materials enter from the top. This structure allows for a continuous production process in the kiln chamber and improves production efficiency.
Calcination process of the double-chamber kiln
The double-chamber kiln uses two chambers for calcining lime, where chamber A and chamber B are interconnected at the bottom of the calcination zone, allowing materials to flow down through both chambers.
During the calcination in chamber A, combustion air and fuel flow in the same direction as the materials, allowing the hot flame to contact the cooler materials that absorb heat. Conversely, the cooler combustion gases contact the gradually calcined materials to achieve uniform calcination conditions and high thermal efficiency. The products of combustion and the CO2 released from the materials enter chamber B through the connecting passage. At this time, chamber B acts as a heat storage chamber, where limestone absorbs heat from the exhaust gases while cooling the gases to a lower temperature, storing heat in the materials for use in heating the combustion air before it participates in combustion during the next cycle. In this scenario, chamber A serves as the combustion chamber, reflecting the co-flow characteristics; chamber B reflects the heat storage characteristics. The next cycle will interchange, with chamber A becoming the heat storage chamber and chamber B becoming the combustion chamber. This cycle allows for continuous calcination of limestone.
Types of fuel
1. Coal: Coal is a common type of fuel that can also be used for combustion in the double-chamber lime kiln. Different types of coal have different calorific values and combustion properties, allowing for the selection of various types of coal as needed.
2. Natural gas: Natural gas is a clean and convenient type of fuel that can also be used for combustion in the double-chamber lime kiln. Natural gas has a high calorific value, produces less exhaust gas during combustion, and has a lower environmental impact.
Production scale and product outline
1. Production scale
A new 600 TPD double-chamber kiln production line will be established. The production capacity of quicklime is 180,000 tons/year for lump lime (≥10mm) and 20,000 tons/year for powder lime (≤3mm).
2. Product quality
The quality of the calcined lime product meets the requirements of YB/T042-2004, with the main indicators: the physicochemical indicators of active lime are shown in Table 2-1:
Table 2-1
Note: Activity refers to taking 50g of active lime, titrating with 4N HCl, and the titration value after 10 minutes.
The quality of limestone meets the PS520 standard in YB/T5279-2005.
3. Energy consumption indicators
The thermal consumption per unit product is ≤850 Kcal/Kg of lime.
4. Exhaust gas emission concentration
The atmospheric pollutant emissions from the lime kiln should meet the "Emission Standards for Atmospheric Pollutants from Industrial Furnaces and Kilns" (DB13/1640-2012).
Advantages of the double-chamber kiln
The double-chamber lime kiln is a traditional lime kiln, and its advantages mainly include the following aspects:
1. Simple kiln structure: The structure of the double-chamber lime kiln is relatively simple, making it easy to manufacture and maintain, without the need for complex technology and equipment, suitable for use in economically disadvantaged areas.
2. Stable calcination effect: The calcination effect of the double-chamber lime kiln is relatively stable, making it less likely to experience uneven calcination or poor lime quality, ensuring the quality of lime.
3. Wide range of fuel usage: The double-chamber lime kiln can use various types of fuel, such as firewood, straw, coal, etc., allowing for the selection of suitable fuel based on local resource availability and economic conditions.
4. Environmentally friendly and energy-saving: Compared to some modern lime kilns, the double-chamber lime kiln has lower flue gas emissions, resulting in relatively less environmental pollution. Additionally, due to its simple structure, it has a higher thermal energy utilization rate, making it relatively energy-efficient.
5. Strong flexibility: The operation of the double-chamber lime kiln is relatively simple, allowing for flexible adjustments and changes based on production needs, adapting to different production requirements. Overall, the double-chamber lime kiln has advantages such as simple operation, stable calcination effect, wide range of fuel usage, and being environmentally friendly and energy-saving, making it suitable for areas with limited technical capabilities and poorer economic conditions.
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