The RTO Dürr delivered to a Singapore facility around ten years ago consists of highly corrosion-resistant stainless steel and reliably purifies up to 25,000 normal cubic meters of exhaust-air mixtures containing solvents from the production of pharmaceutical products per hour. The required oxidation temperature in the combustion chamber was previously provided by two oil-/gas-fired combination burners. This production facility is characterized by solvent mixtures from the processes in highly varying compositions and with greatly fluctuating calorific values. The mixtures also contain various amounts of water in some cases. The customer’s request for the modernization was for all of these waste materials to be removed in the reliably operating RTO.
In the first project phase, Dürr worked out and presented the technological boundary conditions for a reliable, economical solution as part of a feasibility study. The key element of the subsequently realized design is the addition of two liquid burners, allowing all of the energy contained in the solvent-laden waste liquids to be used for operation of the exhaust-air purification system. For this purpose, the solvent-and-water mixture is injected directly into the combustion chambers of the special burners developed by Dürr and is oxidized at a temperature of around 820 degrees Celsius. The solvent-laden residual materials largely replace natural gas as the primary or auxiliary energy source during operation. Auxiliary energy is used mainly only to heat the RTO to operating temperature or to combust mixtures with very low solvent contents. Disposal costs are eliminated, because the solvent-and-water mixtures are utilized in the RTO.
In order to minimize the downtimes required for installation and commissioning, the mechanical and electrical elements for the regulation section comprising liquid fittings were largely preassembled. After installation of the additional burners, only the combustion-air duct had to be connected in addition to the module with the fittings. Modernization was completed by removing the fuel-oil section of the existing combination burners, because only gas will be used as the primary fuel from now on.
Dürr RTO systems are suitable for purifying exhaust air containing combustible and malodorous pollutants at concentrations up to around 10 grams per normal cubic meter. These plants require less primary energy compared to conventional air purification processes, because the energy contained in the hot exhaust gases is used for efficient preheating of the exhaust air. The system can be run “autothermally” above a pollutant concentration of around 1.5 grams per normal cubic meter. In other words, the energy content in the pollutants suffices to operate the plant without additional fuel. In addition to being highly economical, Dürr RTO systems feature an air purification efficiency of more than 99.8%. In addition to the pharmaceutical industry, there are many other sectors in which exhaust air can be reliably and economically purified using regenerative thermal oxidizers. Examples include the chemical, print-coating, and food industries. The use of standardized, modular, and largely preassembled components permits the realization of plants rated at 9,000 to around 100,000 normal cubic meters per hour, which can be easily expanded as needed later on.