Pursuant to the contract, the specialists of Wellons.RU LLC, together with the construction and installation company SMU-1 under the direction of Andrei B. Gaberman, carried out the restoration of the refractory lining of the boiler cells and the lining from October 11 to October 18, 2016 boiler combustion zones (convective part). Due to the fact that the destruction of the refractory is of a similar nature for each furnace, the repair results are shown to restore the most pronounced defects of the refractory lining.
According to the recommendations of Wellons, Inc., for the installation of refractory lining of boiler furnaces, LLC Wellons.RU selected and supplied the following refractory materials:
All materials are checked for integrity of the package, the appearance is checked, the contents of the packages are checked. There are no comments or any deviations from the technical conditions, as well as any visible damage or violation of the integrity of the packaging of materials. All materials delivered to the site are suitable for the reconstruction of the refractory lining of the Wellons boiler.
Plastic refractory materials passed preliminary tests for stackability, plasticity, which confirmed the possibility of using these materials when carrying out lining works without a special formwork device. Specialists of SMU-1 were familiarized with these results, and trained in the methods of laying these materials directly in the furnaces and on the bottom of the boiler.
Boiler furnace: inspection of the boiler fires at Wellons showed that the condition of the refractory lining in all furnaces has more or less uniform wear. The maximum wear of the lining is observed in furnaces No. 1.2, and the minimum in furnaces No. 5.6. The main wear is the fuel chute, the lower part of the furnace in the area of the grates and the neck of the furnace. All the gutters at the time of repair had large destruction of the lower zone at the exit from the furnace wall. In furnaces No. 1-4 there is a maximum destruction of the upper zone of the neck of the furnace. There are pronounced cracks with an opening of up to 150 mm. in width, depth up to 150-170 mm (actually rupture of the refractory and its extrusion into the combustion chamber of the boiler). On the walls of the boiler furnaces there are also deep open cracks that require repair.
Repair of the fuel chute: CALDE ™ PLAST PM 70 plastic refractory was used for repair. Before laying this material, all pieces of the old refractory, which were actually separated from the main layer through cracks, were removed. Most of the refractory material of the gutter was absent, the existing pieces were held at the expense of friction and gravity, and with a small effort easily collapsed. The surface of the gutter was cleaned to a “living” layer. To ensure the binding of a new plastic refractory, anchors made of stainless steel bar were used. Anchors were installed in the main body of the refractory of the furnace wall, in previously drilled holes with a diameter of 14 mm., Depth up to 50-60 mm. The design of the anchors, their size was selected so that the layer thickness of the newly laid refractory was 30-40 mm higher than the height of the anchor. This event allows for a good fixing of concrete, and also prevents the anchor from direct exposure to high temperature, prolonging their service life and concrete in general. The installation of anchors in a checkerboard pattern, directing the mustache of the anchors perpendicular to each other, avoids the installation of a large number of anchors and reduces the internal stress in concrete formed due to different thermal expansion of steel and refractory. The use of plastic refractory makes it easy enough to restore a complex area by mating various surfaces, which is almost impossible to accomplish using the traditional laying method - casting into the formwork (high labor costs, low quality of laying).
Repair of the lower furnace belt (fuel combustion zone): the example shows the principle of restoring the refractory lining on the wall of the boiler furnace. This principle is suitable for any zone of the furnace, with pronounced defects: deep chips, local surface wear, deep wide open cracks. As you can see in the above photographs, the section with a defect in the lining (deep cleavage at the temperature seam) is pre-prepared - a fragment of the old refractory is made with fairly clear defined boundaries. The depth of the "hole" should be at least 100-120 mm. - this will ensure an unsecured laying of the plastic refractory and will provide strong adhesion of the newly laid concrete with the existing lining. Due to the lack of thermal shrinkage of the refractory used, this material will hold tight by filling in irregularities in the old lining. In these areas, we put the new WELL-PLAST P82 refractory material in terms of performance not inferior to CALDE ™ PLAST PM 70, but in Al2O3 content significantly exceeding the specified material. We are sure that the WELL-PLAST P82 material will prove itself from the best side. We consider it appropriate to conduct this industrial test, as the expected cost of this material will be 25-30% lower than its foreign counterparts. This difference is very significant, especially when carrying out large volumes of work, for example, associated with the complete replacement of refractory in furnaces. You can familiarize yourself with the stages of laying this type of material (plastic refractory monolithic refractory) in detail by watching the small film “LAYING WELL-PLAST R82” on our website.
Repair of small cracks in the wall of the refractory (up to 15-25 mm in the width of the crack): to seal open cracks with a small opening, the two-component refractory mixture CALDE ™ PATCH PT 86 2CP is used. This mixture, when properly mixed, has high ductility, has good adhesive ability, which makes it easy to penetrate deep into cracks and, due to almost zero thermal shrinkage, hold tightly and sinter with old refractory material, thereby preventing crack development and refractory fracture.
We recommend having a small supply of this material (packaging 25 kg. Paper bags), which will allow, if necessary, to quickly prepare the finished mixture, and make a seal of “open” cracks.
Repair of large, deep cracks in the wall of the refractory (opening width up to 100-150 mm.): The photo shows that the transitional part of the neck of the furnace into the combustion chamber (convective part of the boiler) is practically detached from the boiler wall. In some cases, these “cracks” are end-to-end, i.e. visible metal construction of the furnace and boiler sheathing. These defects must be repaired and brought into compliance with the technical regulations for the maintenance of the thermal unit.
The main refractory material CALDE ™ PLAST PM 70 is used to seal and repair large cracks in the boiler furnaces. Outside the furnaces, to solve similar problems, a material with a lower content of aluminum oxide CALDE ™ PLAST PF 55 CO can be used.
Sealing of burner holes in the front wall of the boiler: due to the fact that almost from the beginning of the operation of the boiler, gas burners were not used in the technological process, together with the specialists of the plant, it was decided to lay these burner holes in order to stop the air supply necessary for cooling gas burners . The cooling air volume was significant (opening of air gates up to 10%) and had a negative effect on the operation of the boiler, reduced the temperature of the gas flow in the convective part of the boiler, thereby reducing the efficiency of the boiler as a whole.
After carrying out measures to bookmark these burner devices, we look forward to increasing the efficiency of the boiler, which can be estimated experimentally during operation.
Refractory plastic concrete of the brand CALDE ™ PLAST PF 55 CO was used for laying burners using a supporting, supporting structure and anchor products. This material is delivered ready for use and does not require additional work on the formwork device, the material is laid by the method of stuffing with a hand mallet or by pneumatic ramming.
In the attached photographs you can see the partition device as a whole. For the manufacture of anchors, a stainless steel bar was used. Restoration of precipitated refractory tiles, open cracks and joints was carried out.
Repair of collectors of water screens: during the operation of the boiler on the collectors of the front and side screens, partial destruction of the refractory concrete installed earlier occurred. Moreover, the destruction of the refractory on the collector of the frontal screen amounted to about 60%, including the upper row of the masonry retaining wall. On the side screens, destruction in several places, with a total volume of up to 50% of previously laid concrete. Work on the restoration of the lining of the collectors included:
Repair of the hearth of the boiler, the necks of the furnaces: preliminary inspection results showed great wear on the necks of the furnaces, especially on more loaded furnaces No. 1-4. The necks of the furnaces No. 5.6 are in satisfactory condition. The places of contact between the neck of the furnace and the surface of the hearth of the boiler also have defects, a “torn” structure — a large number of chips, a rise in refractory bricks, and a rise in the upper zone of the furnace (neck) as a result of the formation of deep cracks with an opening of up to 150 mm. (the situation is described in the paragraph for repairing large cracks).
The attached photos show examples of restored fireboxes. On the example of firebox No. 4, it can be seen that some of the fireboxes underwent significant restoration repair until the laying of new concrete on the missing sectors of the necks and bottom of the boiler. On all furnaces, as well as on the surfaces of the interface with the bottom of the boiler, work was carried out to repair deep cracks, chips, and refractory was restored to prevent further destruction of the lining during operation of the boiler. As refractory material in these areas, the plastic refractory material CALDE ™ PLAST PF 55 CO was used.
After the reconstruction works of the refractory lining of the boiler furnaces, as well as the lining of the convective part of the boiler (boiler bottom), we can conclude that the refractory lining of the boiler is in good condition. Unfortunately, there are a number of measures that are not covered by this repair, which over time need to be implemented, such as:
It is advisable to carry out these works (the first three points) together to ensure high-quality repair of lining replacement, which will allow refractory fireboxes and the boiler as a whole to comply with all requirements of the rules for technical operation of the boiler plant. To minimize the risk of refractory failure, as well as repair costs, these measures can be carried out in stages, for example, one, two fire chambers per year. The need to replace the lining will be the subject of analysis of the condition of the lining of the boiler by specialists of Wellons.RU OJSC during the shutdown of 2017-2018. (free for the plant).
We strongly recommend using heat-resistant concrete with a heat-insulating layer as a refractory for restoring the boiler hearth. The use of monolithic refractory will make it possible to avoid permanent repairs on the boiler hearth, from geometry violations, etc., as well as to ensure the maximum service life of the refractory lining.
