1. Project Background & Overview

The comprehensive utilization of bulk solid waste represents a critical pillar in the national strategy for sustainable resource management and circular economy development. With China’s solid waste generation reaching unprecedented volumes, the effective treatment and resource recovery of construction debris, industrial slag, and municipal refuse has become an environmental imperative. During the 14th Five-Year Plan period, the nation has elevated comprehensive solid waste utilization to a strategic priority, mandating that disposal rates reach specified targets while minimizing landfill dependency.

The enterprise featured in this case study operates a large-scale facility dedicated to the resource recovery of construction and demolition waste. Their primary business encompasses the production of recycled aggregate concrete, eco-friendly bricks, and road base materials derived from processed construction debris. Established in 2005, the company has evolved into a comprehensive solid waste management enterprise with diversified operations spanning mining rehabilitation, tailings processing, industrial byproduct recycling, and renewable building material manufacturing.

With annual processing capacity exceeding 3 million cubic meters of construction waste, the facility generates substantial quantities of exhaust gases containing particulate matter, sulfur oxides, and nitrogen oxides during the crushing, screening, calcination, and material handling operations. The existing dust collection systems proved inadequate for meeting the increasingly stringent emission standards mandated by environmental protection authorities, necessitating a comprehensive upgrade to integrated multi-pollutant control technology.

2. Pollution Source Analysis & Emission Characteristics

Comprehensive characterization of the facility’s emission profile was conducted through systematic monitoring and analysis. The primary pollution sources identified include raw material crushing and screening operations, rotary kiln calcination processes, material conveying and storage systems, and finished product packaging lines. The exhaust gas stream exhibits complex composition with high particulate loading, elevated moisture content, and significant temperature variations.

The environmental impact assessment for this project identified 24 distinct pollution factors requiring control measures. The following table presents the comprehensive emission inventory and baseline parameters:

Table 2-1: Environmental Pollution Factor Analysis

3. Treatment Solution & Engineering Design

The comprehensive treatment solution for this project was developed through rigorous technical evaluation and process optimization. The total project investment of 32 million RMB encompasses the construction of three primary production lines: one construction waste crushing and screening line with annual capacity of 600,000 cubic meters, one recycled aggregate washing and classification line processing 400,000 cubic meters annually, and one eco-friendly brick manufacturing line with annual output of 150 million standard bricks.

3.1 Process Flow Design

The exhaust gas treatment system employs a multi-stage integrated approach combining high-efficiency dust removal, wet flue gas desulfurization, and selective catalytic reduction (SCR) denitrification technologies. The process flow sequence is as follows:

3.2 Design Principles & Technical Requirements

The engineering design adheres to the following fundamental principles ensuring reliable, efficient, and sustainable operation:

3.3 Equipment Selection & Configuration

The major equipment specifications were determined through detailed technical calculations and vendor qualification assessments. The following table summarizes the key equipment parameters:

Table 3-1: Main Equipment Specifications

4. Operational Performance Analysis

4.1 Energy Consumption Analysis

The operational energy consumption was systematically monitored over a 24-month period following commissioning. The comprehensive energy audit reveals the following consumption patterns:

Table 4-1: Energy Consumption Analysis

The total annual electricity consumption for the environmental protection system reaches approximately 5.16 million kWh, with the induced draft fan and slurry circulation pumps representing the primary energy consumers. Operating at 24 hours per day, 330 days annually, the system maintains consistent treatment performance with power consumption of approximately 158 kWh per hour of operation.

4.2 Operating Cost Analysis

The economic viability of the treatment system was evaluated through detailed operating cost analysis. The following table presents the comprehensive cost breakdown:

Table 4-2: Operating Cost Analysis

The comprehensive annual operating cost totals approximately 8.06 million RMB, equating to 24.4 RMB per ton of processed construction waste. The ammonia consumption for SCR denitrification represents the largest single operating expense at 206 million RMB annually, followed by electricity consumption at 348 million RMB.

4.3 Emission Compliance Monitoring

Continuous emission monitoring systems (CEMS) were installed at the stack outlet to verify compliance with regulatory standards. The following table presents the emission monitoring data:

Table 4-3: Emission Monitoring Data

5. Technical Performance & Achieved Results

5.1 Dust Removal Performance

The high-efficiency bag filter system demonstrated exceptional performance, consistently achieving outlet dust concentrations below 10 mg/m³ against an inlet loading of 1,000 mg/m³. The PTFE membrane fiberglass filter bags with pulse-jet cleaning system maintained stable pressure differential between 1,200-1,500 Pa throughout the monitoring period. The dust removal efficiency stabilized at 99.2%, significantly exceeding the design guarantee of 99%.

5.2 Desulfurization Performance

The limestone-gypsum wet flue gas desulfurization system achieved SO&sub2; removal efficiency of 96.8%, reducing inlet concentration from 120 mg/m³ to consistent outlet levels of 38-45 mg/m³. The system produced approximately 25 tons of commercial-grade gypsum daily as a valuable byproduct, generating additional revenue streams that partially offset operating costs. The liquid-to-gas ratio was optimized at 18 L/m³, balancing removal efficiency against pumping energy consumption.

5.3 Denitrification Performance

The SCR system utilizing V&sub2;O&sub5;-WO&sub3;/TiO&sub2; catalyst achieved NOx reduction efficiency of 82.5%, with outlet concentrations consistently maintained below 80 mg/m³. The ammonia slip was controlled below 3 ppm, preventing secondary pollution and minimizing ammonia consumption. Advanced NOx treatment solutions like this SCR configuration represent the most reliable approach for meeting stringent nitrogen oxide emission standards in solid waste processing applications.

6. Operational Risk Assessment & Mitigation Strategies

6.1 Identified Risk Factors

Through two years of continuous operation, several risk factors requiring ongoing attention were identified:

6.2 Mitigation Measures

The following countermeasures have been implemented to address identified risks:

7. Lessons Learned & Best Practices

7.1 Design Phase Insights

The project construction period extended to 8 months, slightly exceeding the initial 6-month schedule due to foundation reinforcement requirements and equipment delivery delays. Key design-phase lessons include:

7.2 Operational Excellence

Operational data over 24 months reveals several best practices for maintaining optimal system performance:

7.3 Economic Optimization

Post-commissioning optimization efforts reduced unit treatment costs from the initial 28 RMB/ton to the current 24.4 RMB/ton through:

8. Conclusion & Recommendations

This case study demonstrates the successful application of integrated multi-pollutant control technology in a large-scale solid waste processing facility. The combination of high-efficiency dust removal, wet flue gas desulfurization, and SCR denitrification achieved consistent compliance with stringent emission standards while maintaining economic viability.

The total investment of 32 million RMB and annual operating cost of 8.06 million RMB represent a significant but necessary commitment for environmental stewardship. The achieved emission levels—particulate matter at 8.5 mg/m³, SO&sub2; at 45 mg/m³, and NOx at 72 mg/m³—demonstrate that modern RTO and desulfurization systems can reliably meet the most demanding regulatory requirements in challenging industrial applications.

For facilities planning similar upgrades, the following recommendations are offered based on this operational experience: