Durable Ceramic Solves Abrasion Issue in Pneumatic Ash Conveying Pipes

Introduction

Abrasion issues in conveying pipes have long plagued various power plants and chemical factories utilizing the positive dense-phase pneumatic conveying technology. These concerns directly impact the safe and regular operation of equipment due to the challenges in high-altitude pipe maintenance, soaring labor costs, and severe dust pollution. Utilizing wear-resistant ceramics as pipe linings, leveraging the outstanding properties of AI₂O₃ ceramics such as high hardness, strong toughness, excellent abrasion resistance, light weight, and convenient replacement, has significantly addressed the problem of abrasion in pneumatic ash conveying pipes. This article delves into the technology, structure, and optimization of these ceramic-lined pipes, presenting a comprehensive solution to the prevalent abrasion issue.

Overview of Pneumatic Ash Conveying Systems: Principles and Processes

Device OverviewThe system comprises three UG-110t/5.3MPa-M secondary high-pressure coal-fired boilers with a rated evaporation capacity of 110t/h and an overheated steam pressure of 475℃. Employing II-type layout, single steam drum, natural circulation, tangential firing, balanced ventilation, and solid slag removal coal-fired boilers, water for the boilers is supplied by peripheral supporting equipment. The coal conveying system is designed in dual routes. Ash conveying, slag conveying, desulfurization, dedusting, and other auxiliary facilities are separately established, ensuring standardized emissions and meeting the steam supply needs for chemical plants.

Principles of Bag Filter Dust CollectorAll three boilers utilize bag filter dust collectors, each with 6 ash discharge points, evenly distributing the ash quantity. Additionally, 2 ash discharge points are set at each economizer. The ash removal employs a positive dense-phase pneumatic ash removal system, with a conveying distance of approximately 95m and a height elevation of around 24m.

Introduction to Pneumatic Ash Conveying TechnologyThe conveying process in the positive pressure dense-phase pneumatic system relies on several principles. Firstly, it operates based on the principles of solid-gas two-phase flow to achieve pneumatic conveying. It also utilizes static and dynamic compression in the air compression process to efficiently transport materials. The fly ash in the silo pump is significantly affected by sulfidation and exhibits a simultaneous sulfidation and conveying state. The system comprises five parts, primarily relying on conveyors with matching specifications to meet specific conveying requirements. Each conveyor operates independently and can function individually or collectively. The operational process during conveying can be divided into four stages for each cycle.

Challenges in Pneumatic Ash Conveying SystemsThe potential continuous scouring of ash conveying pipes due to the mixture of dust can lead to severe abrasion. The bends, particularly, experience relatively severe outer wear as the airflow might alter its direction on one side. Addressing the significant wear issues encountered with previously used centrifugally cast composite ceramic pipes, a switch to alumina ceramics, specifically a-Al₂O₃ with an alumina content ≥95% and sintering temperature up to 1670℃, has substantially enhanced the durability of the ceramic-lined pipes, increasing their lifespan by over five times compared to centrifugally cast composite ceramic pipes.

Structure and Performance of Wear-Resistant Ceramic-Lined Pneumatic Ash Conveying Pipes

Wear-Resistant Ceramic Liner for Pneumatic Ash Conveying PipesThe technology of lining ash conveying pipes with wear-resistant ceramics is mature. It requires the ceramics to be exceptionally hard, such as the Jingcheng brand chromium corundum ceramics, with an alumina content ≥95%, pressed dry at 100 tons and achieving a Rockwell hardness of HRA85, second only to diamond. The classification of wear-resistant ceramics depends on the Al₂O₃ content, where higher content corresponds to more stable performance.

Structure of Ceramic-Lined Pneumatic Ash Conveying PipesThe steel components in pneumatic ash conveying pipes fall into two categories: one involves welding short sections of straight pipes into a shrimp-like shape, while the other employs integral hot bending to form bent pipes. For instance, Jingcheng-brand wear-resistant ceramic pipes utilize seamless 20# steel pipes, undergo integral hot bending (non-welding shrimp joint), exhibit smooth inner and outer surfaces without burrs, and use flange connections, comprising steel pipes, adhesives, and wear-resistant ceramics as three layers. The fixing method for wear-resistant ceramics has been optimized, shifting from traditional simple organic adhesive pasting to staggered pasting, reducing the possibility of abrasion through gaps and significantly enhancing reliability.

Advantages of Ceramic-Lined Pneumatic Ash Conveying Pipes

• Abrasion Resistance: Extends lifespan by over 5 times compared to centrifugally cast ceramics and casting stones.

• Corrosion Resistance: Internal ceramics effectively mitigate the effects of acidic and alkaline corrosion.

• Tolerant to Moderate Temperatures: Operates consistently at a certain temperature, suitable for various conditions.

• Relatively Smooth Inner and Outer Walls: Facilitates free material flow, preventing material hanging or blockages.

• Easy Installation: Lighter than standard pipes, easing transportation and simplifying installation.

• Reduced Maintenance Workforce: High abrasion resistance reduces the frequency of repairs and inspections, optimizing manpower utilization.