Zhonghe Case | Xinjiang Lime Project

Achieving balanced low energy consumption, high yield, premium quality and environmental compliance is a persistent challenge for lime kiln production. Simply lowering fan airflow to cut power costs fails to deliver sustainable cost savings. Supported by field measurement data, this Xinjiang lime kiln rectification case offers valuable references for production line operation optimization.

Project Overview

The facility is an 800 t/d rotary lime kiln in Xinjiang, equipped with SR7-MQ/T burners and fueled by pulverized coal of 5500 kcal/kg. After startup, abnormal operating conditions emerged, including undercapacity, massive underburnt lime and fluctuating excessive flue gas emissions, greatly hindering production efficiency.

Abnormal Operating Conditions & Vicious Cycle

Core indicators failed to reach standards. Actual daily output was merely 600–700 tons. Temperature distribution reversed, registering 630°C at the kiln inlet and 860°C at the outlet, triggering severe underburning. Key parameters: 35-second pusher cycle, coal consumption of 6 t/h, 32Hz frequency for induced and primary air fans. SO₂ emissions fluctuated from 300–800 ppm with peaks above 1000 ppm, preventing environmental equipment acceptance. Coal air pressure swung between 16–26 kPa, destabilizing combustion. Minor parameter adjustments could not fix the fundamental issue.

Root Cause: Oxygen-deficient Calcination from Insufficient Air Supply

To reduce power expenditure, operators cut fan airflow, causing oxygen shortage inside the kiln. Without corresponding coal feed adjustment, oxygen-deficient combustion took place.Evolution chain: insufficient oxygen → incomplete coal combustion and weak flame rigidity → low front-kiln calcination temperature → underburnt limestone → reduced output and qualification rate → accumulation of unburnt substances → excess SO₂ and volatile air pressure. All anomalies arose from mismatched ratios of air, coal, temperature and capacity.

Systematic Rectification Plan

Centered on adequate air supply, optimized air-coal ratio, stable emissions and phased capacity improvement:

1. Stabilize low-load operation and gradually raise induced air volume to eliminate oxygen deficiency, ensure thorough coal combustion and break the vicious cycle.

2. Control coal consumption at 190 kg/t initially. Emission targets: SO₂ ≤20 ppm (limit:100 ppm), NOx maintained at 450–500 ppm.

3. Implement coordinated parameter regulation to boost output step by step. Dynamically adjust loads based on emissions, combustion conditions and kiln temperature, and optimize burner air distribution, coal feeding pressure and kiln speed to realize precise matching of air, coal, speed and temperature.

Rectification Outcomes

Systematic commissioning yielded prominent improvements. Peak daily output hit 980 tons. Restricted by the cooler’s load capacity, the line operates stably at the designed 800 t/d capacity. Coal consumption fell to 180 kg/t under full load, surpassing design targets. SO₂ and NOx remain within compliance limits, clearing the way for environmental equipment acceptance. Even kiln temperature eliminates underburning completely, securing a 100% product qualification rate.

Conclusion

This 800 t/d lime kiln case verifies that no absolute minimum-energy operating mode exists; the optimal solution lies in balanced working conditions. Stable compliant production relies on proper air distribution and full combustion. Balanced development of yield, quality, energy conservation and emission reduction constitutes the foundation for long-term steady rotary kiln operation.

Specializing in rotary kiln burners for 27 years, Zhonghe Electromechanical provides customized low-nitrogen combustion solutions for lime, pellet, cement, ferronickel, lithium salt and chemical industries. Backed by abundant project experience and complete maintenance services, we continuously upgrade technologies to resolve production challenges and support enterprises in energy-efficient, eco-friendly and stable production.