۱- Introduction

۲- Description of the traditional process

۳- Energy saving simulations and methods

۴- Improvement of the desolventizer operation

۵- Energy and environtal impacts of the improved process

۶- Conclusions

References

Abstract

Soybean oil is widely used as cooking oil, whereas the soybean cake is a valuable ingredient for animal food. The extraction of soybean oil is an energy-intensive process, with additional significant impact on the environment via the wastewater and hexane emissions. The research investigated different ways to minimize the energy consumption. In a traditional process, both direct (live) steam and indirect steam heating (jackets, tubular exchangers) are used to deliver the required heat duty. Direct steam injection is restricted to the first evaporator and the stripper, for a total of 620 kg/h. Indirect steam is also applied in the evaporators for a total of 6.44 MW. The desolventizing process requires a steam energy input of 8.15 MW. Integration of a heat exchanger network in the evaporation and stripping part of the process reduces the amount of direct steam usage from 620 kg/h to 270 kg/h and of the indirect heat duty from 6.44 to 5.05 MW. In the cake desolventizing part of the process, the energy requirement is reduced from 8.15 to 2.12 MW. The overall gross energy saving is hence ∼۵۰%. The improvements moreover reduce both the waste water loadings by 56.5% and the CO2 emissions by 62.5%. Hexane emissions are moreover significantly (>90%) reduced.

Introduction

Vegetable oils are commonly used for different end applications. Whereas edible vegetable oils, such as soybean, peanut, palm and sunflower oils are used in food commodities. (Alam et al., 2014), they also find applications in biodiesel or even bio-aviation fuel via transesterification and other secondary transformation processes. (Issariyakul and Dalai, 2014; Lin et al., 2009; Wang et al., 2017; Yun et al., 2013). There are also a number of oils, such as rice bran oil, palm kernel oil and sheanut butter, that are used in specific markets with added value for cosmetics and pharmaceuticals. (Cargill, n.d.) Soybeans are used worldwide for their oil and protein contents. In 2017, the world production of soybeans was 340 million ton (33.9% in America, 32.1% in Brazil, 16.2% in Argentina). The world production of soybean oil was 56 million ton. The high content of poly-unsaturated components in soya has positive effects on the human health, by e.g. reducing the blood lipids, preventing blood clots, and boosting immunity. The cultivation of soybeans moreover captures nitrogen from the air and transforms it into N-fertiliser. The main components of the soybean are proteins (36 wt%), carbohydrates (30 wt%), fat/oil (20 wt %) and water (9 wt%). The composition of the soybean oil is given in Table 1 (Carrín and Crapiste, 2008).