Cement, Energy and Environment

dissipated heat power rises to 10.6 kW per kg/s. Water use and water savings are big and increasing issues in many countries. Therefore, when considering this topic and with regard to sustainability, the ABB ORC power plant uses specifically– designed, high-end dry condensers to avoid water consumption . Due to the appropriate design, the condensers can be operated with low specific electricity consumption at small temperature differences between the condensing organic vapour and the ambient air - in other words: the condensation temperature is not much higher than ambient and the difference to the wet cooling tower is small. Electrical parts and control The electrical power is fed into the plant's grid from the generator at an appropriate voltage level, usually medium voltage. The electrical container centralizes breakers, safety equipment and the necessary control devices. Where necessary (specifically with the fluid pump) variable speed drives are installed to match the, operation of the ABB ORC power plant ideally to the operating conditions of the cement plant. Design The main modules are designed as standard modules, which form the ABB ORC power plant. This means the power plant can easily be adapted to every waste heat source by only altering the intermediate cycle to the respective industry plant. The conversion module is designed for unchanged operating process conditions. Moreover the power plant is designed to only use a small surface area, due to a very compact construction. Figure 6 shows the compact ABB ORC power plant: at the bottom level all the components that need observation or maintenance (electro- mechanical components as turbine, pumps, generator, valves etc.) are installed. The middle floor level contains all the static components: process heat exchangers, piping. The top of the steel frame carries the condensers. Specialities In cement plants The highly variable Figure 6. Layout of the ABB ORC power plant. conditions of the cement plant (temperatures, flow rates, drying requirements etc.) make it necessary to accurately examine the operating conditions, ideally over one year. This is particularly easy when an expert system is installed that records the respective production data of the plant. The precise examination of the cement plant leads to an optimum design of the ABB ORC power plant and thus avoids too big an installation (unnecessarily economically expensive) or a too small power plant (loss precious electricity from waste heat). The waste heat sources in cement plants make a great demand on the engineering of the heat extraction part of the power plant. Specifically the high dust load of the waste gas after the preheater tower places high requirements on the design of the heat exchangers. Waste heat sources Prehester The dust load of the preheater gas lies in the order of magnitude of 50 -100g/Nm 3 • Additionally, eventual condensing components must be considered. As the temperature of the waste gas cannot be reduced to a very low level (temperature requirements of the raw mill) the danger of condensation Is, In normal cases, negligible. The dust Issue Is taken Into consideration by heat exchanger design. The exchanger Is a bare tube type with geometry designed accordingly. Past experience (the longest used heat exchanger of that type has been In operation since 1991 on the heavy dust side In a cement plant) has shown that this type of heat exchanger with stands the high dust load In the waste 31