On December 21, 2021, according to contract No. XXX for a visual inspection of the state of a new refractory lining of equipment for waste disposal (incinerator), the specialists of Wellons.RU LLC performed a technical inspection, the results of which are shown below.
INSINERATOR FOR HEAT DISCHARGING AND WASTE BURNING:
The incinerator is a single structure consisting of two chambers - a combustion chamber and an afterburner. The combustion chamber is equipped with a sliding roof that provides top loading with fuel (large-sized wood waste - boards, pallets, etc.) using a front loader, and is equipped with five diesel burners, two of which are located in above grate zone, three - in the undergrate zone. These burners are used to ignite the furnace and to maintain the required combustion temperature equal to 850°C. The afterburner chamber is equipped with two diesel burners, which are used to provide afterburning of combustible gases unburned in the first chamber in order to ensure compliance with emission standards. The installation of the refractory and heat-insulating lining of the furnace was carried out at the factory prior to shipment; the drying of the lining was carried out on site during the commissioning period. The removal of flue gases (combustion products) is carried out through the chimney due to natural draft.
The combustion chamber - of the furnace has a two-layer refractory lining with a total thickness of 150 mm. The working layer of the lining is made of monolithic refractory concrete (aluminosilicate), layer thickness 100 mm. Heat-insulating layer - made of fibrous heat-insulating board, layer thickness 50 mm. Inspection of the lining was carried out after the stage of drying and firing of the lining. The schedule for drying and heating the lining, as well as work on drying the lining were carried out by the specialists of the manufacturer.
According to the results of the inspection of the lining, after the drying stage, it is necessary to pay attention to the following points:
- Expansion expansion joints are provided by the design of the lining only directly in the corners of the combustion chamber, at the junction of the end and horizontal walls. That at the stage of drying the lining and heating it to 700°C, made it possible to avoid the appearance of cracks in the concrete monolithic refractory lining, but, unfortunately, not in full. You can observe the formation of an angular crack on the end wall (upper right corner of the front wall), which, with a certain degree of probability, will lead to the formation of an angular chip in the lining in this place. The absence of an expansion joint directly in the end walls, due to the small length of the walls and the presence of two corner expansion joints, may not affect the integrity of the lining.
- The absence of expansion joints in large longitudinal walls leads to the formation of internal temperature stresses in the monolithic liner, which in turn leads to the formation of numerous cracks. At the moment, the nature of the cracks (filamentary, thin) does not affect the quality of the lining. The strength of the structure as a whole is not violated, and the presence of an anchor field (anchor pitch 200x200 mm, according to the manufacturer's representatives) is an additional guarantee of maintaining the integrity of the structure.
At the moment, we do not recommend covering up thin threadlike cracks with a refractory compound (mortar, cement, concrete) as we see in the photographs presented. In the case of the progression of these cracks, their opening (an increase in the thickness of cracks over 5-6 mm for the entire thickness of the working layer of the lining) in the process of further operation, it is necessary to take certain measures to prevent their further increase, depending on nature of defects.
The formation of filamentary cracks in the working layer of the refractory is a consequence of the design of the lining proposed by the manufacturer. When installing the lining in the factory, the specialists of the plant used the formwork device in two stages - the first: installation of the formwork on the longitudinal walls and pouring concrete in one step without placing cards; in the second stage (after the concrete has set and the formwork of the first stage has been dismantled), the end wall formwork and concrete pouring in one step without the device of cards. Although, when we talk about refractory concretes on a hydraulic bond, the de-vice of cards and expansion joints using rolled heat-insulating material is one indissoluble process that ensures reliable operation and a long service life of the refractory.
The grate – is made of concrete type-setting grate segments. Due to the fact that these grates are operated in difficult conditions, the manufacture supplied an additional five grates to ensure prompt replacement in the event of an emergency failure of any grate. This spare set has been dried and fired while drying the refractory lining. The spare kit is ready for use. A through crack was formed on the side base plate (near the front end cover) during firing up and drying of the lining (or during transporta-tion). Due to the fact that the crack formed two large pieces, the load-bearing capacity of this slab did not suffer, but this slab will require replacement during fur-ther operation (warranty case).
Combustion chamber cover – lining is made of soft heat-insulating material, good condition. It is necessary to draw the attention of the operators of the plant and the loader to the inadmissibility of overloading the incineration plant, and "leveling" the bale layer due to the movement of the cover. In the case of a vertically standing board, armatura, etc. in the fuel layer, this heat-insulating lining is easily damaged.
Afterburner chamber – the lining is made using heat-insulating modules 200 mm thick, made of refractory ceramic fiberglass Cera-blanket. The working temperature of these blocks is up to 1260°C or up to 1425°C, depending on the material used. But in any case, it is sufficient to ensure the safe operation of the installation. These refractory blocks are used for lining walls, vaults and floors, burners of the afterburner. Due to the fact that in this chamber there is no possibility of physical impact on the heat-insulating lining (there is no possibility of mechanical damage to the lining by loaded waste, fuel and other materials), the use of this material (based on modular heat-insulating blocks) more than justified due to its low thermal conductivity. There are no comments on the af-terburner chamber lining. Well done.
