Stainless Steel: New applications ensure cost savings for the industry

Although the sugarcane industry has used stainless steel in some of its equipments since the decade of 70, the expansion of its use has grown more expressively in the last 10 years thanks to the good performance of the material in the various industrial processes and Of its cost-benefit ratio, which has been shown to be very advantageous. If we evaluate the entire production process, from start to finish, of a power plant nowadays, we can observe the use of stainless steel in almost the entire line of the manufacturing, however, some new applications can bring even more gains the mills. In the industry, the manufacturing stages where there is greater wear on the equipment are at the entrance of the cane, because this contains lots of sand, and grinding. The wear can also be provoked by the characteristics of the process, predominating problems of corrosion in the fractions, microbiological corrosion, and widespread corrosion. However, the biggest injury may be the emergence of so-called "black dots" in sugar, oxides and particles unfastened from carbon steel that can compromise the quality of the product. Thus, a correct specification of stainless steel will contribute to better performance of the equipment or even for the elimination of corrosion or undesirable particles. The use of stainless steel in sugarcane mills began in applications in tubular bundles of evaporators and since then has been expanding in other areas of the mills. Currently, there is an intensive use of stainless steel in the reception of cane (lateral and bottom of the cane track, table feeder, crankshaft and table bottom) and in the extraction, mainly in intermediate table (bottom or the table 100% in stainless steels), shut donelly, Bicas and Broth tanks (gamelão), and piping of broth conduction. In the boiler part, stainless steel is used in drag talisings, track bottoms, gas washers, chimneys, pipelines, boiler bagasse dispensers etc. Distilleries can already be 100% in stainless steel. These are some examples, but there are several other applications throughout the entire production process. According to Iwao Ishizaki Neto, application Engineer at Aperam, in recent years the mills have been adopting management practices to optimize the resources, that is, to do more with less. "Since the off-season of the mills has been shortening, which requires greater reliability of equipment, availability and fewer unplanned downtime, the use of stainless steels contributes greatly to the optimization of resources, reducing the cost of Maintenance and increasing the reliability of the plant, "he explains. Willians Cintra, manager of Açotubo Sertãozinho, says that there is growth in sales of the division of stainless steels for this sector exceeding two digits per year. "The increase in the level of information in the sector, the development of new alloys in stainless steels and the need for more sustainable processes are the main reasons for this increase in consumption." Still according to Cintra, the areas of greatest demand are those that suffer abrasion in addition to the attack of Chlorides, sulfides and other chemical agents from the soil, cane or the manufacturing process. "The areas that are most demanding inox are, in addition to the entry of sugarcane, extraction of broth and steam generation, in the manufacture of sugar, in tubes for cozers, mirrors, crystallizers, agitators, elevators, condensers and in the distillery," he observes. LESS COST, MORE SERVICE LIFE Among the various types of stainless steel, the most used by the mills are: 304, 316L, 410D, 439 and 444. According to Ishizaki Neto, in the initial processes of sugar manufacturing, in which the problems of abrasion predominate, the ideal type of stainless steel to withstand this operation is the 410D, especially in humid media, where the abrasive and corrosive attacks coexist. "The chromium content present in the 410D stainless steel makes it suitable for application where moderate corrosion predominates and combined corrosion/abrasion effect, typical of this stage of the process. In the tanks too, as are environments subjected to moderate corrosion, the 410D has been presenting great performance ", adds. After the milling, in the sulfitation, the use of type 316L prevails, which must be produced under strict manufacturing procedures to withstand the conditions of high aggressiveness of the environment. In the process of treatment and vaporation of the broth and sugar production, the most common type is 444, followed by the 304. These stainless steels are used in equipment such as heaters, evaporators, vacuum cookers, crystallizers and dryers. According to Ishizaki Neto, the recommended stainless steels resist very well the aggressiveness of the medium and can be selected considering the lowest cost for the project. The characteristics and properties of stainless steels, such as low roughness of the walls, high mechanical strength and corrosion, will enable greater equipment efficiency, lower maintenance cost, longer service life and better quality of sugar. "The carbon steel, widely used in cooling towers, has a very high corrosion rate, making the inox competitive and more suitable for this application. In the distilleries, both 444 and 316L can be applied, but the 444 has a lower price, "he says. Stainless Steel tubes have great advantages in heat exchange processes (evaporators), providing energy savings. This is possible thanks to the lower wall thickness of the stainless steel tubes (between 1.0 and 1.5 mm) due to its superior corrosion resistance. In addition, a larger driving area and a greater ease of cleaning are guaranteed, which, in turn, implies, once again, lower maintenance costs and fewer downtime. "An important example is the gas washers and chimneys in stainless steel 410D. This equipment, when manufactured in carbon steel, has a useful life, on average, from three to four harvests, not counting the interventions/maintenance that are more onerous for each crop. Now, when they are manufactured in stainless steel, they can last up to 10 harvests without maintenance and with very small thickness losses, almost negligible, as is the case of some sugarcane units that we have observed. We also have examples of tubular beam of evaporators with 15 years of use, "says Ishizaki Neto. Cintra adds that due to the high resistance to oxidation and abrasion of stainless steels, especially after the release of stainless steel 410D – which already has a new version 410M, even more resistant to abrasion-, the sugarcane industry ensures that its Equipment have greater durability. "In addition to the lower need for maintenance stoppages, which causes great impact on the profitability of these companies, another significant gain is in quality. Stainless steels have a sanitary feature, that is, they are easy to clean materials, do not release residues and have very low reactive grade with the liquids processed ", stresses. NEW APPLICATIONS: INDUSTRY AND AGRICULTURE Nowadays, stainless steels are used more in the areas of the plant that have contact with products or in processes with heat exchange and in corrosive and abrasive processes. However, Cintra says that the stainless material has great flexibility and can bring returns in several areas of the industry as in boilers, pre-Air Lines, evaporators and agricultural. "I believe in the use of stainless steel in fermentation dorns. Stainless steel can provide lighter dornas and facilitate cleaning. In the agricultural part I believe that the stainless steel could contribute a lot in the parts of the harvester and transhipments of sugarcane that suffer a lot with wear/abrasion ", he notes. The use of stainless steel in cane track talisles, one of the most recent applications, for example, if compared to carbon steels, has the durability three times greater than the applications in carbon steel (Figure 1). "In general, all stainless steel applications in the mills are economically viable, but in sugarcane track cleats it is very viable. We are already working together with a partner in the development of conveyor chains between mills and we have computed excellent results in the second crop in field tests ", reveals the application engineer of Aperam. "We believe that there is a large space to be conquered by stainless steels. After 2008 the investments in plants fell significantly, with this, many groups did not modernize their lines and still have a large part of their processes formed by lagged equipment with predominant use of carbon steel ", he says. For Ishizaki Neto There are two areas in which the mills can have excellent results: fermentation and agricultural. "I believe in the use of stainless steel in fermentation dorns. Stainless steel can provide lighter dornas and facilitate cleaning. In the agricultural part I believe that the stainless steel could contribute a lot in the parts of the harvester and transhipments of sugarcane that suffer a lot with wear/abrasion ", he notes. The use of stainless steel in cane track talisles, one of the most recent applications, for example, if compared to carbon steels, has the durability three times greater than the applications in carbon steel (Figure 1). "In general, all stainless steel applications in the mills are economically viable, but in sugarcane track cleats it is very viable. We are already working together with a partner in the development of conveyor chains between mills and we have computed excellent results in the second crop in field tests ", reveals the application engineer of Aperam. In addition to the financial difficulties of the units, the level of resources in the plants for maintenance or is maintained or is reduced, requiring the managers to use the resources available in the best possible way to put the plant to operate. Investing in stainless steel requires a greater contribution of capital and this still makes a little difficult the decision of the plants for the use of this material. However, according to Ishizaki Neto, many are changing the...