Simulation-Based Optimization of the Energy Consumption in the Hardening Process for Calcium Silicate Masonry Units

Abstract

Owing to a high cost pressure and the need for a reduction of carbon dioxide emissions for manufacturing calcium silicate masonry units (CS), the CS-industry strives to cut the energy consumption. The most energy consuming process step is the autoclaving. About 87% of the energy is required for this particular process step, where the green bodies are steam-hardened at 200°C.For reducing the energy consumption, most of the alternatives aim at optimizing the complete manufacturing process. In this paper, the focus is put on an optimized loading process for the autoclaves, in consideration of preceding and subsequent process steps. For this purpose, a simulation model is developed, where different strategies of loading are implemented and tested. This model can be used to find optimally scheduled assignments of production orders to the available autoclaves, based on the volume of each manufactured product.The analysis of the tested strategies shows, that it is possible to save up to almost 9 % of the required energy for autoclaving by an optimized assignment of the available autoclaves.

Efficient Method for Optimizing Calcium Silicate Masonry Unit Manufacturing Using Simulation-Based Optimization and Decomposition

“…In previous research a complete modular system for discrete event simulation (DES) models of CS plants was built, based on various CS manufacturing systems [1]. Main optimization focus using simulation for CS plants was an energy efficient autoclave loading process [3]. Due to the high energy consumption, an optimized regulation has a strong impact on the total cost of a plant.…”

“…Meanwhile the CS market has evolved into a customized market and thus requires smaller lot sizes with a frequent setup of machining tools. To decrease the setup time, the correct mix is critical and will save costs [3].…”

“…Calculate matching mixing timetable It emerges as a result of the previous paragraphs, that the hardening is the most critical process regarding energy consumption, impact on total cycle times and possible congestions (see also [2,3,6]). It was identified as a batch process disconnecting two continuous sub-processes (pressing and packaging), which exerts an influence on the whole manufacturing process as follows (with reference to the process map in Figure 1):…”

“…To further improve these stages of the production, they stated a need for further research efforts regarding the use of simulation in CS manufacturing. In another study the results demonstrated, in spite of various modelling assumptions, the suitability of simulation models to optimize the hardening process of CS [3]. Although the study already focuses on energy efficiency in CS plants, efforts should not be limited to a one-dimensional target setting.…”

Heuristical Solution for Scheduling Single Stage Parallel Machines Production of Calcium Silicate Masonry Units with Sequence-Dependent Changeover Times to Improve Energy Efficiency

“…On one hand, setup times on average reaching from 1 h to 3 h are currently not feasible for one-piece-flow, although a lot of effort has already been put into shortening setup periods, as timeconsuming tasks like changes of punch and/or die as well as associated calibration activities have to be performed. On the other hand, hardening masonry units requires high pressure, variant dependent heating curves, huge amounts of energy and time periods of multiple hours [1,2]. Currently, it is performed in autoclaves which are hermetically sealed throughout the whole hardening process of a fixed amount of masonry units.…”