(412c) Reduction of the Generated Sugarcane Stillage in Distillation through HEAT Integration

Despite the well-established benefits of ethanol as a renewable, sustainable, and fossil-free energy source, the massive and increasing volume of processed sugarcane and ethanol produced over the years has had implications. One of the major concerns today is sugarcane stillage (or vinasse), the most abundant by-product of ethanol production, which is generated at an average rate 12 times greater than that of ethanol. Highly nutritional, it has the potential to replenish most of the minerals taken by sugarcane plants during the season, however, it can also be highly pollutant if treated or disposed incorrectly, unbalancing the soil, compromising crops efficiency by overfertilization, polluting rivers and groundwater, thus characterizing a serious environmental impact and a problem for the industry. Fertigation is the most widely used method for sugarcane stillage application in Brazil, however standards like CETESB P 4.231/2015 and CONAMA 430/11 led to the need to distribute stillage throughout wider areas, demanding a larger and more expensive infrastructure, leaving 60 to 70% of the field not being fertigated. Stillage is composed almost entirely by water (circa 95% in volume) being a fraction of it removed (or not) by evaporation in the end of the process, however, as applied today, dedicated stillage reduction systems have poor cost-effectiveness and are unfeasible in most cases, making it urgent to find process optimizations capable of effectively generate less stillage. The solution proposed by this work uses pinch analysis and heat integration techniques between stripping columns in order to efficiently reduce the volume of stillage yet during stripping step, in-place, in a leaner and potentially cheaper approach. Process simulations indicated that stillage/ethanol ratio can be reduced from 12:1 v/v to 5:1 v/v, assuming a wine feed with 8% of ethanol in volume at 20°C, resulting in a 58% less stillage generated in the process. When higher concentration wines are considered, this ratio can reach up to 1.5:1 v/v, as demonstrated in the results section of this paper. This unprecedented result not only helps restore viability to fertigation by broadening its application radius, but also eliminates the need for specialized equipment for stillage concentration, thereby lowering the plant's cost and footprint.