There are a number of advantages accruing from manufacturing chemicals using continuous processing techniques compared to a batch based process. Many of these arise from “process intensification” factors related to smaller reactors operating in under steady state conditions.
Added to these are advantages arising from the improved chemistry control which often results in higher yields and/or less impurities that would need to be removed. The table below summarises the potential manufacturing cost improvements that can result from continuous processing.
Click image to view table.
This table is based on some analysis of the generic cost elements for a typical fine chemical. The impact of process intensification and continuous processing is different for these different cost elements and also does vary from process to process. The generic improvements are based on the following observations:
- Raw materials – improvements arise from increased yields as the process can be run under conditions that maximise the conversion without risking competitive or consecutive reactions. With better heat transfer, the amount of solvent required can be reduced in cases where the solvent quantity is used to constrain the rate of reaction or absorb the heat of reaction.
- Utilities – by using significantly smaller continuous reactors, the peak loading on the heating/cooling utilities is lowered and less energy is wasted heating up and cooling down at the start and end of each processing cycle. In addition, the facility can be smaller and this reduces the HVAC required to maintain the operating conditions throughout the facility.
- Plant labour – once running, continuous processes operate at steady state so there is less need for intervention by plant operators other than keeping a steady supply of starting materials and managing the flow of product.
- Capital cost – being much smaller, the capital cost of building a continuous plant can be significantly less that than the equivalent batch production plant.
- Plant overhead – continuous processing at steady state results in a much more consistent profile of the quality of the product. This eliminates a significant amount of in-process and release quality control. With less solvent usage and fewer impurities to remove, the waste stream from a continuous process is less than that of the equivalent batch process and this reduces the cost of waste disposal.
- Research and Development Costs, Marketing & Sales Costs, General Overheads – these costs are largely independent of whether batch or continuous processing is employed.
Based on the potential cost improvements arising from process intensification for each of these cost elements, it can be shown that a continuous process can be anywhere from 20-50% less that the equivalent batch process.