Taking the heat off thermal processes
A commercial process in material manufacturing, thermal processing is probably one of the most energy-intensive processes. It is used in several manufacturing sectors and usually involves a number of operations that result in an advanced material, which is further used for producing the final product. Several times, however, the material itself is the final product of the manufacturing process.
The discussion, however, is not about the product achieved after thermal processing but about the process itself. As mentioned, it is one of the most energy-intensive of operations. Thus, manufacturing units are always on the lookout for ways to conserve energy to rein in costs. In today’s environment-conscious scenario, it has become crucial to keep your processes such that the carbon footprint is minimal and can be justified. It may sound like a practice that should have become a hygiene factor, but usually, it takes a considerable amount of time for the process to reach from initial investigation stage to commercial scale production.
For, if this one crucial step is considered, units can do away with, or at least minimize, the installation of new equipment for energy conservation – usually a capital-intensive investment. Experts advise that to come to a conclusion about the final thermal process and how it will work, it is important to elaborate on it at the laboratory stage, where the application is still being developed. For instance, research and studies have shown that continuous thermal processes mean better energy conservation. It also means lesser time taken to heat ancillary components.
A recently developed technology called self-heat recuperation technology is also being talked about. Here, the total process heat is recirculated within the manufacturing unit, and means significant energy saving. Decreasing the residence time is an excellent way of energy conservation. Variables such as temperature uniformity, peak temperature and mass diffusion can come in the way and have to be addressed for optimal residence time. With increasing volume, units look at larger furnace sizes, which lead to more surface area that not only needs to be heated but also loses heat – which only means more energy consumption. And when the deadlines are tight and the production cycle is stretched, several resort to batch furnaces that are known for poor efficiency; they also cycle the entire thermal mass of the heating chamber, having to reach peak temperature again and again.
The solution? A dilute-phase vertical drop reactor is more suitable in processes where the residence time is a minute or lesser. If the residence time is less than two hours, a rotary tube furnace or even a dense-phase moving bed vertical reactor is a good bet. And if the residence times are even longer, opt for tunnel furnaces.
Industry experts also warn of residence times that are not optimized and may have an adverse effect on the product quality. For instance, in powder processing, long residence times may actually lead to particles collecting together, further leading to an additional step in the manufacturing process. Coming to the material, the flow of the same also has a bearing on the kind of furnace to be used. The material can be either powder, which is free-flowing or sticky, or in any other form. A furnace has to be chosen to transfer the material so that heating, diffusion and shrinkage is uniform and the furnace volume is optimized.
The commercial volume of the product also has to be kept in mind since there are materials whose market demand can increase or decrease. Consequently, there needs to be scope for scaling up or down, which will not only ensure energy optimization but also prove to be cost-effective. There is also the question of design temperature of the furnace, which means those materials that can withstand high temperature will be treated there. It is common knowledge that the temperature rating of an insulating material increases its cost, too. Thus, different kinds of insulation are used in a furnace to control the costs. But high temperatures mean using more expensive insulation as well as decreasing the life of those that may be exposed to higher temperatures. Thus, there are several places where the water-cooling technique is used. All this needs to be considered while considering energy efficiency.
What can also make a significant difference to your commitment to conserve energy is the product quality, which has a bearing on the number of steps and the type of processing steps that will be used. Most times, the cleaner the material to be treated, the more energy efficient the processing is. Trace elements and impurities lead to side reactions, an increase in temperatures and so on, which again need to be dealt with. Of course, working on better processes saves costs, but it also has a positive impact on the environment, which is seriously threatened at the moment. Reducing carbon footprint is not only a part of a company’s corporate social responsibility, but also a sound business strategy.
