MER Group: Brief Introduction to the Working Principle of Twin-Shaft Kiln
The core structure of a twin-shaft kiln consists of two interconnected vertical shafts (Shaft A and Shaft B), with an overall vertical layout that occupies a small footprint. The bottoms of the two shafts are connected via a channel, and a reversing device is installed at the top to realize periodic switching of their functions. The middle part of the kiln is the calcining zone, the bottom is equipped with a discharge device, and the top is fitted with feeding and flue gas exhaust equipment. Its design core lies in achieving efficient heat utilization through "alternate calcination and waste heat recovery," with a thermal efficiency of over 80%.
The working principle is based on the logic of "synergy between two shafts and periodic reversal," and the specific process is divided into two alternating cycles (each cycle typically lasts 8-12 minutes):
First Stage (Shaft A for Calcination, Shaft B for Preheating/Cooling):
Fuel is injected and burned through the burner at the lower part of Shaft A, generating high-temperature flue gas of 1200-1300℃. The high-temperature flue gas flows upward along Shaft A, calcining and preheating the limestone added from the top, enabling the limestone to gradually complete the decomposition reaction. Subsequently, the high-temperature flue gas enters the lower part of Shaft B through the connecting channel at the top of the two shafts, continuing to preheat the limestone in Shaft B to achieve the first recovery of flue gas waste heat. Meanwhile, cold air enters from the top of Shaft B, flows downward to cool the calcined quicklime in Shaft B. The cold air absorbs the sensible heat of the quicklime and is heated into hot air, which is sent to Shaft A as combustion air through the bottom channel, realizing the second recovery of sensible heat. At the end of this stage, the calcined quicklime in Shaft A is discharged from the bottom, and the materials in Shaft B are fully preheated.
Second Stage (Shaft B for Calcination, Shaft A for Preheating/Cooling):
The functions of the two shafts are switched via the reversing device. Fuel is now injected and burned from the lower part of Shaft B, and the high-temperature flue gas flows upward along Shaft B to calcine the materials, then enters Shaft A to preheat the newly added limestone. Cold air enters from the top of Shaft A, cools the calcined quicklime in Shaft A, and the heated hot air serves as combustion air for Shaft B. Through such periodic alternation, the two shafts continuously cycle the functions of "calcination - preheating/cooling" to achieve continuous production. Throughout the process, the flue gas heat and sensible heat of quicklime are fully recovered and utilized, significantly reducing the unit product heat consumption.
