Technical Paper


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Graph 3: Development of plants and capacities in the UK - Source: Ecoprog Why refractories lining in WtE Plants


The current trend for more compact installation and the need for higher energy throughput result in more severe operating conditions; including severe


temperature fluctuations, higher operating temperatures and


higher variety of chemically aggressive substances. Consequently, safe and efficient operation of WtE boilers requires the use of high performance refractories to protect the metallic membranes from corrosion. In WtE


Application and Products Charge Zone


plants, the combustion chamber is an essential part of the system. The chamber is formed with metallic tubes, arranged vertically and welded together in continuous section (a wall membrane). The water circulating in the tubes recovers part of the heat generated from the burning waste. The energy recovery in the form of steam and/or electricity is then used for the local communities in which the facilities operate. Considering the high temperatures generated in the burning of the waste and the corrosive nature of the flue-gas, refractories are generally applied over the metal boiler tubes to protect them from the harsh environment.


Alumina Brick/Refrax 20 Brick Inlet Roof


Combustion Area


Refrax® ProGun 80/ProGun 70 Refrax® ProPlast 80/ProGun 70


Special tiles in Refrax® PLUS using Refrax® Promor mortar expansion joints fibre mastic/CF paper


Grate Lining


Special Bricks in Refrax® PLUS or Refrax® TOP


Alumina Ramming – Alfrax AFR 700 SiC Ramming – Refrax ProRam 80/ ProRam 70


using Refrax® Promor mortar Burner Outlet


1st Pass


Special tiles in Refrax PLUS using Refrax Promor mortar expansion joints in Fibrefrax/CF paper


Superheater


Tubes – Special Shieids in Super cast Refrax and super Refrax 20 using Carbofrax 3445AT mortar


Superheater


Anchors/connections – Alfrax AFR7O0 Ramming


Header/Collector


Refrax ProGun 80 Gunning/Trowel mix Or


Repairs/Patching in tube areas 3,4,6,6 Refrax ProGun 80/ProGun 70 – suitable for trowelling and casting as


Refrax ProPlast 60/ProPlast 70 – Plastic/Ram mix Figure 2: Refractory segmentation in WtE units - Source: Saint-Gobain 18 ENGINEER THE REFRACTORIES


Refrax ProPlast 60/ProPlast 70 Ash Hopper


Alfrax CK abrasion resistant Trowel mix


Typical system and SiC materials for tube wall protection


The current generation of Saint-Gobain advanced refractory protection consists of refractory tiles systems attached to the boiler tubes walls and backed by a self-flowing refractory castable or mortars. The backing castable has generally high silicon carbide content (60-80%) to increase the thermal conductivity, thus complementing the high conductivity of the tile system to ensure an efficient thermal transfer from the combustion chamber to the boiler tubes.


Besides being an excellent path for thermal


transfer, the added advantage of the back-cast tile system is that in the event of damage or failure of the tile, the cement behind provides an additional tube wall protection until appropriate repairs. In addition to this safety function, the T-Clip Pro system installed with conductive castable results in lower tile temperatures (below 800°C) [2], [7] therefore limiting the corrosion mechanisms and ash accumulation on their surface. (Figure 4 and Figure 5).


January 2019 Issue


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