Overall, the sustainable longevity and the energy efficiency of the entire bioethanol produc tion plant are our main priorities,” says Mika Jokinen, Director of Operations of St1. By working closely with their customer, the experts from the Process Technology business unit of Sulzer Chemtech were well aware of these requirements. They put their extensive know-how and full understanding of inherent system limitations as well as all information on relevant feed streams into the game. Different process simulation tools were applied to adapt various plant concepts, resulting in an optimized process solution which could be offered to St1 with a guaranteed process performance based on the specific raw materials to be applied in the process. The Finnish energy company St1 Biofuels Oy produces bioethanol transportation fuels from waste and industrial process residues, thus introducing new methods of efficient waste management. In this way, the company uses organic raw materials that do not compete with the food chain. St1 recently acquired an existing fermentation plant in Finland and, as a first step, planned the upgrade to new processes to produce bioethanol from grain-processing residue. The bioethanol product is subsequently blended into the existing gasoline network of St1. What St1 needed for this upgrade was a technology for the recovery of the bioethanol from the fermentation broth, and they found a strong and experienced partner in Sulzer Process Technology. Sulzer is a leading supplier of distillation column internals for bioethanol, biobutanol, and biodiesel plants and is market leader in this field in the USA. Sulzer has an outstanding position, particularly in bioethanol distillation, due to its extensive experience in fouling applications (mash columns). For advanced biofuels production, Sulzer Process Technology has delivered complete process plant solutions including liquid-liquid extraction, distillation (including reactive distillation), and membrane separation units to many countries around the world.
Unique heat integration
Based on its accumulated expertise in providing solutions for demanding industrial separations and its wide range of thermal-separation technologies, Sulzer has developed heat-integrated process solutions for advanced biofuel distillation and dehydration. Sulzer’s heat integration concept for these applications is unique in optimally combining distillation and vapor permeation technologies. This hybrid combination substantially reduces overall energy consumption, as both technologies are utilized at their highest efficiency. Sulzer analyzed the requirements of St1 and proposed a skid-based solution which is most suitable based on the plant’s capacity. In addition, Sulzer’s process design for the heat-integrated bioethanol distillation process addressed all customer requirements, including energy efficiency, delivery time, skid size, and cost. The decentralized waste-toenergy concept of St1 requires a highly economical production. Low capital investment in combination with low operational cost are essential parameters. The complete, preassembled skid as ordered by St1 comprised a mash column connected directly downstream to a heatintegrated rectification column, as core equipment.
Biofuels are derived from biomass based on plant or animal material. Commonly used biofuels today are bioethanol, biodiesel, and biogas. Biofuels offer an alternative to scarce non-renewable resources like crude oil. First generation biofuels are most commonly derived from sugar or starch crops (bioethanol) or vegetable oil seeds (biodiesel). Second generation biofuels are derived from cellulosic non-food sources such as wood and switch grass, waste products from forestry, agriculture, households or paper production. The use of waste feedstock results in a high sustainability potential and greenhouse gas savings, i.e., a small ecological footprint. For more information on Sulzer solutions for biofuels, please visit: www.sulzer.com/biofuels
Efficient distillation process
Sulzer’s distillation process is based on proven experience for first and second generation bioethanol plants and process designs for numerous other applications. The comprehensive application knowhow for its thermal-separation technologies enabled Sulzer to provide St1 a plant with a guaranteed process performance. In Sulzer’s process concept, the bioethanol is concentrated up to only 90 wt% in the distillation section, which substantially reduces the energy demand in the rectification by 30–50% from that of conventional rectification design concepts. In the mash/beer column, Sulzer VG AF™ trays are used 1. These trays from the VGPlus tray family are especially designed for fouling services.
In combination with the optimized process design parameters (adapted operating temperature, high turbulence in the evaporators), plant availability is considerably extended before cleaning becomes necessary. In the rectification tower, Kühni slit trays are applied. In similar applications, Sulzer’s structured packing like the MellapakPlus family has also proven to be an excellent technology for process intensification in these towers.