On February 12, 2018 Wellons.RU LLC fulfilled the project for the complete replacement of anti-corrosion refractory protection of sulfur flow equipment: sulfur furnace, gas cleaning first and second stages scrubbers, gas duct between scrubbers. The work was performed under the EPC contract, including engineering, selection, and supply of materials, refractory works.
For this project new refractory acid-resistant materials were used, including monolithic acid-resistant refractories.
Within this project Wellons.RU LLC experts operatively restored drawings of 1959–1961 years which were practically lost. The drawings were digitalized and the new ones were developed for this project of the sulfur flow equipment refractory replacement. The whole package of technical documentation was delivered in *.dwg format to the plant specialists for further use. Part of the working drawings for this project is presented in the section ENGINEERING on the company web-site.
Due to the low resistance of the refractory on the sulfur flow equipment (low quality of materials, poor refractory structure, etc.), our company faced the task to provide a ready-made process solution with modern, high-quality acid-resistant refractory materials.
The main criterion of materials selection for this project is acid resistance, which is regulated by GOST 474-90 “Acid-resistant brick”. Accordingly, for this project, all materials of the working layer must have minimum 97.5 % acid resistance, determined according to GOST 473.1-81 “Chemically resistant and heat resistant ceramic wares”. In cooperation with the specialists of Borovicheskiy combinat ogneuporov (Borovichi Refractory Plant, AO “BKO”) at the plant’s own R&D laboratory, numerous researches were conducted on the possible use of new equipment refractory materials used with strong acid impact.
Basing on the tests results, we focused on the following basic materials of the working layer, which showed the best result, both for acid resistance and strength characteristics:
It should be noted that the necessary volume and assortment of refractory materials for this project was produced and delivered to the site exactly as scheduled.
All the works related to the installation of anti-corrosion refractory were directly supervised by Wellons.RU LLC specialists. Specialists of OOO SMU-1 LLC, subcontracted by AO Solikamskbumprom within our EPC contract, installed the refractory and performed necessary auxiliary works.
All the main types of work are described below in the relevant sections. You can see it also in our brief video in the section SULFUR FLOW — REFRACTORY on company web-site.
Refractory monolithic concrete was used for highly engineered units of sulfur furnace:
The refractory concrete was installed on previously cleaned surface with installation of AISI 310S heat-resistant steel anchors and 5 mm thick fire-resistant board.
The use of a monolithic refractory in these zones allowed to increase the structure strength and to avoid additional complicated work and errors when using traditional pre-formed refractories (bricks), such as: adjustment of brick by chipping, grinding, filling of masonry looseness in transition areas with complex surfaces (observation windows, furnace housing, etc.).
The use of refractory concrete in the transition section of the sulfur furnace and the 1st stage scrubber completely solves the refractory strength issue in this section. This is achieved by installation of anchors and unloading supports which take the load of the scrubber refractory vertical section, reducing the refractory pressure on the transition section arc.
The refractory of the furnace horizontal cylindrical part is made of shaped refractory bricks of various sizes to ensure the maximum correct refractory circumference. The refractory is an annular masonry with a masonry mortar. The used masonry mortar was prepared using liquid silica glass with hardener (refractory for the 2/3 furnace circumference bottom). To ensure the necessary strength of the masonry in the upper part of the furnace (at 1/3 of the furnace circumference), a specially designed removable formwork was used, as well as a special high-temperature air-hardening adhesive. The use of this adhesive guarantees maximum strength of the masonry joint, fast setting and strength of the arch structure after the formwork removal. The use of this adhesive minimize possible errors in the refractory of critical components such as an arched construction.
The sulfur furnace refractory thickness is 230 mm, the furnace length is 6,800 mm, its diameter is 1,900 mm. The total furnace refractory weight is 22,200 kg.
More details on the sulfur furnace refractory are presented in the video SULFUR FURNACE — REFRACTORY on company web-site (REFRACTORY section).
Sulfur flow equipment is used for sulfuric acid production, with additional safety requirements for this equipment. One of the requirements of anti-corrosion protection is the additional layer of sheet lead which prevents the acid direct interaction with scrubber steel shell in the event of refractory destruction.
The scrubber bed and vertical part shells were coated with lead sheets before the refractory works. For the 1st stage scrubber the height of 3 mm sheet lead coating was 400 mm.
Due to the fact that the temperature of the gas flow in the lower part of the 1st stage scrubber can reach 1,250–1,300 °C, the project provides two-layer refractory consisting of a working and insulating layers along the entire height of the scrubber.
Scrubber bed has two layers. The working layer is 230 mm thick, it is made of monolithic chemically resistant refractory concrete with the Z-shaped expansion joints (preventing the sulfur gas penetration through the joints), with the bed slope to the drain hole. 70 mm thick insulation layer is made using insulating refractory concrete. The total thickness of the 1st stage scrubber bed refractory is 300 mm.
Scrubber bottom wall refractory to the pinch throat (scrubber diaphragm) — two-layer refractory: 300 mm thick working layer of acid-resistant brick, and 50 mm thick insulating layer. The total thickness of the 1st stage scrubber bottom refractory is 350 mm. Shaped bricks of various sizes (double-sided radial brick) in accordance with GOST 21436-2004, as well as insulating tiles in accordance with GOST 8691-73 were used for refractory. The total height of the 1st stage scrubber bottom refractory is 3,250 mm.
Scrubber throat/diaphragm installation. A monolithic refractory was used for tapered throat of variable cross-section (1,200 mm / 600 mm) with centered 1,600 mm diameter hole. Due to the large mass of the throat (21,600 kg), a number of unloading supports are installed, ensuring that the load is transferred to the scrubber shell housing (lower row of supports) directly from the throat mass. And also for the load reduction upper row of supports is installed directly on the monolithic refractory of the throat from the refractory of the scrubber vertical part (the supports are made of 12X18H10T heat-resistant steel). To ensure the strength of the throat structure, the anchors made of AISI 310S heat-resistant steel of the following sizes are installed: 60х4х800 mm, 60х4х650 mm.
For the scrubber upper wall refractory from the level +4,250 mm to +15,355 mm shaped bricks (double-sided radial brick) were used, but of a smaller thickness. The working layer thickness is 200 mm, the insulation layer — 50 mm, the total refractory thickness is 250 mm. A number of unloading supports are provided at certain height of the masonry (~ 3,500 mm) to reduce the refractory load on the lower rows of bricks, ensuring the load transferring to the scrubber housing walls.
Scrubber cover refractory — at 15,355 mm level the 300 mm thick scrubber roof was installed using chemically resistant refractory concrete. Technology of monolithic refractory installation: pre-installed SS anchors; mounted self-supporting formwork; concrete supply using pump via the holes of the scrubber cover steel housing. To ensure the necessary temperature conditions, namely positive temperature (+10...15 °C), both inside the scrubber and outside, temporary enclosure for the construction work was installed with air heater.
The positive temperature during the refractory works is a mandatory requirement for these works in winter. Thus air heaters of the required power were installed.
As a masonry mortar for pre-formed refractories, an aqueous mortar based on liquid silica glass with hardener was used.
More details on the 1st stage scrubber refractory are in the video 1ST STAGE SCRUBBER — BED AND TRANSITION AREA, and also 1ST STAGE SCRUBBER — REFRACTORY on company web-site.
1st stage scrubber characteristics: internal diameter — 3,800 mm, height — 15,655 mm. The total mass of the 1st stage scrubber refractory is 130,924 kg.
The scrubber bed and vertical part shells were coated with lead sheets before the refractory works. For the 2nd stage scrubber the height of 3 mm sheet lead coating was 1,000 mm.
Due to the fact that the temperature of the gas flow in the 2nd stage scrubber is not high (the max. inlet temperature is 300 °C), the project provides the single-layer chemically resistant refractory of one working layer for entire scrubber height.
The scrubber bed is single-layer. The concreting was two-stage. At the first stage a 140 mm thick concrete layer was installed on the 5 mm blanket asbestos. After this, the formwork was assembled with square housings for vertical load-bearing grate blocks. At the second stage the final 140 mm thick concrete layer was installed. The total thickness of the bed protective refractory is 280 mm.
Grates zone. From the bed level to the grate level +3,665 mm, one 300 mm thick layer of chemically resistant brick was installed. All pre-formed refractory was installed with a masonry mortar based on acid-resistant and chemically resistant powder. An aqueous solution of diabase powder with liquid silica glass and hardener was used. Shaped bricks of various sizes (double-sided radial brick) in accordance with GOST 21436-2004 were used for refractory.
Due to the fact that the 2nd stage scrubber is the last stage of gas flow cleaning with direct accumulation of sulfuric acid and its required concentration (pH ~ 4–4.5), special attention was paid to the high quality filling of the joints with masonry mortar. The thickness of the joints is 2–3 mm, the joints are completely filled. Also, special attention was paid to filling of the rear joint adjacent to the scrubber steel shell. Due to imperfect shells geometry, the thickness of the rear joint could reach 10–15 mm or more. In any case, the full filling of the joint adjacent to housing with acid-resistant masonry mortar on the basis of diabase powder performs the anti-corrosion protection of the steel scrubber housing.
For additional protection of the sulfuric acid accumulation zone to the 1,200 mm acid storage level, the 100 mm thick protective layer was installed using chemically resistant concrete. After that, the surface of the protective layer and the bed surface were treated with an acid-resistant mortar based on a diabase powder. We believe that the performed works ensure reliable, trouble-free operation of this section and the entire scrubber 2nd stage protective refractory as a whole.
The 2nd stage scrubber bed and grates zone protection refractory works are presented in the video 2ND STAGE SCRUBBER — BED AND И GRATES ZONE on company web-site.
The grate is mounted with large-block units produced by custom order from acid-resistant material. The grate is a two-store structure of vertical (300x300x940 mm) and horizontal (300x400x700 mm) blocks, above which the grates are mounted directly — 130x400x1000 mm transverse blocks. The purpose of the grate is to ensure the free passage of the gas flow and to provide the load-bearing capacity of the grate for a large number of Raschig rings. The critical unit, which required individual engineering, as well as the development of a special technology for the production and firing of large-block products at the manufacturing factory. The complexity of the design, the large weight of large-block units (from 120 to 270 kg) required the use of a special technology for blocks handling into the scrubber, as well as their installation and grate assembling in general.
The total number of blocks in the grate is 205 pcs., the total weight is 35,130 kg.
Scrubber wall refractory. For the single-layer refractory, from the upper level of the grate to the scrubber cover, from +4,800 mm level to +21,000 mm level, the shaped bricks (double-sided radial brick) were used. The thickness of the working layer brick is 200 mm. A number of unloading supports are provided with certain masonry vertical interval (~ 3,000 mm) to reduce the refractory load on the lower rows of bricks, guaranteeing the load transferring to the scrubber housing walls.
Scrubber cover refractory — at 21,100 mm level the 300 mm thick scrubber roof was installed using chemically resistant refractory concrete. The technology of monolithic refractory installation (anchor, formwork, temperature regime) is similar to the 1st stage scrubber cover installation procedure, described in the corresponding section.
In addition to the described refractory works for the 1st and 2nd stages scrubbers, in each scrubber there were installed mounting and inspection hatches, transitional sections of the gas duct connection, etc., using monolithic, chemically resistant concrete. In detail, the work described above is presented in the video 2ND STAGE SCRUBBER — GRATES AND REFRACTORY on company web-site.
2nd stage scrubber characteristics: internal diameter — 4,500 mm, height — 21,400 mm. The total mass of the 1st stage scrubber refractory is 172,860 kg.
Due to the fact that the gas duct between the scrubbers at the time of the start of the refractory works was not mounted on the sulfur flow equipment, it was decided to perform the refractory works step-by-step in order to reduce the equipment repair time in general.
Gas duct elbows — the refractory of the upper and lower gas duct elbow was performed at zero level with previously installed anchor field. The 120 mm thick monolithic, chemically resistant refractory was used. After refractory works, the elbows were mounted on the appropriate scrubbers and connected by a vertical part of the gas duct. After the installation of the elbows, the scrubbers’ refractory transition sections and elbows were covered with monolithic refractory.
For the vertical section of the gas duct there were used shaped bricks of different size (double-side neck brick) according to GOST 8691-73. Refractory is single-layer, 114 mm thick. A number of unloading supports are provided with certain masonry vertical interval (~ 2,350 mm) to reduce the refractory load on the lower rows of bricks, ensuring the load transferring to the scrubber housing walls. All brick was installed with a masonry mortar based on acid-resistant and chemically resistant powder. An aqueous solution of diabase powder with liquid silica glass and hardener was used.
In detail, the work described above is presented in the video GAS DUCT — REFRACTORY on company web-site.
Characteristics of the gas duct between 1st and 2nd stages scrubbers: internal diameter — 1,610 mm, cylindrical part height — 9,415 mm. The total gas duct weight is 17,815 kg.
This project was successfully performed by Wellons.RU LLC in a short time and with high quality. The key factors of this project successful implementation are following:
