Application cases of anti-wear grills in supercritical boilers

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　Grid anti-wear technology is an active anti-wear method that involves installing alloy grid plates on the surface of the water wall in both horizontal and vertical directions to form a grid-like structure. This prevents the formation of high-speed flow patterns along the wall surface, optimizes the flow field on the water wall surface, eliminates local vortices, reduces the speed at which the gas-solid flow moves along the wall, and decreases the cutting force exerted by material particles on the water wall, thereby effectively controlling wear on the water wall. 　　Examples of the use of anti-wear grids in supercritical boilers: A new materials company in Guangxi’s 3*350MW units. Three supercritical 1240T/H CFB generator sets were put into operation in 2018, serving to supply power to 400,000-ton electrolyzers as well as other large-scale smelting equipment. 　　During operation, electrolyzers have an extremely high power demand, and the power supply must not be interrupted. Once a power outage occurs, the production line stops operating; in severe cases, it can even lead to the destruction of the entire electrolyzer, resulting in losses of hundreds of millions of yuan. 　　Prolonged operation under high load conditions resulted in 13 instances of water wall wear and leakage in the three supercritical boilers within one year, causing significant losses to the company’s production. 　　Brief overview of the unit: Three 350MW supercritical CFB boilers, with a single air distribution plate per furnace and an M-shaped arrangement; balanced ventilation, primary intermediate reheating, circulation fluidized bed combustion mode, and high-temperature cooling cyclone separators.
Distribution of components on the front wall: 12 medium-temperature superheaters, 12 high-temperature superheaters, 6 high-temperature reheaters, and 5 water-cooled walls on the partition wall;
Distribution of components on the rear wall: 8 additional water-cooled walls with dual heating surfaces, in a membrane structure and arranged vertically;
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Analysis of wear in supercritical boilers
The areas prone to wear are as follows:
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1. The dense-phase region of the water-cooled walls;
2. The corners of the furnace;
3. The area around the flue openings and the swirl zones on the rear wall;
4. The area surrounding the secondary air inlets;
5. The areas at the angles between the water-cooled walls on the partition wall and those on the front and rear walls;
6. Locally protruding parts of the heating surfaces and areas near the pipes passing through the front wall, etc.;
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Harm caused by wear in supercritical boilers
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When wear and leakage occur in the furnace of a supercritical circulation fluidized bed boiler, the high steam pressure results in more severe erosion compared to boilers with lower pressure levels. 　　Its characteristics are as follows: 1. The initial explosion site causes faster erosion of the surrounding water wall; 2. The area affected by erosion is larger, the scope of impact is wider, and the pipe failure losses are more severe. 　　　　Before adopting the grid anti-wear solution, the following anti-wear measures were tried: 1. Anti-wear metal spraying; 2. Anti-wear beams made of cast materials; 3. Surface welding of alloys. Based on the actual results of their previous use, none of these methods – anti-wear beams, metal spraying, or surface welding – were able to completely solve the wear problem. 　　Given the rapid erosion and severe consequences that occur when supercritical boilers experience wear and leakage, stricter requirements are imposed on the protection of their water wall. 　　Customers need a safe and efficient anti-wear technology to ensure the safe and long-term operation of boilers. 　　Application of anti-wear grids in supercritical boilers
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In light of the characteristics of supercritical boilers, we have carried out specialized optimized designs:
1. A new type of anti-drop and anti-wear grid plate was developed to further enhance safety;
2. The construction methods for installing anti-wear grids were optimized;
3. Anti-wear solutions were designed specifically based on the structure of the furnace and its wear patterns.

Construction timeline:
July 2019: Anti-wear installation for the grid of Boiler No. 2 in the first unit;
September 2019: Anti-wear installation for the grid of Boiler No. 3 in the second unit;
October 2019: Anti-wear installation for the grid of Boiler No. 1 in the third unit.

Anti-wear effectiveness:
Based on the operational performance of the three supercritical boilers in this plant since the anti-wear modifications were carried out, none of the nearly 200,000 anti-wear plates installed in these boilers have fallen off, and the problems related to wear and leakage that previously existed have been completely resolved. 　　A comparison is shown before and after the anti-wear modification of the grid; no thinning was observed in the originally wear-prone areas. Furnace No. 2, which was modified first, has been operating under high load steadily for over 16 months now. 　　After the anti-wear modification using grills, the three boilers have been in operation to this day without any incidents of wear or leakage in the water wall, thereby significantly extending their operational lifespan. 　　The effectiveness and safety of the grid anti-wear technology have been well verified in supercritical boilers.