(Português BR) Biodiesel

In a biodiesel plant, efficient phase separation plays a key role in guaranteeing product quality in the post-transesterification stages, from biodiesel refining to glycerol recovery. After the transesterification reaction, the resulting mixture comprises two immiscible phases. The heavier phase consists of glycerol, while the lighter phase is made up of biodiesel, both contaminated with excess alcohol, water and catalyst residues. Phase separation is also present in the biodiesel refining stage, after washing the biodiesel with acidulated water, where it is necessary to separate the biodiesel from the water. In the glycerin recovery stage, in order to obtain blond glycerin, it is essential to extract the olein formed after the glycerin water neutralization process.

Obtaining high reaction yields and the final purification of the product and by-product depend fundamentally on the efficiency of the separation between the ester and glycerin phases. Among the separation methods used, decantation in horizontal vessels stands out as the most economical, due to the low solubility and density difference between the phases.

The use of PlatePack in decanters at a biodiesel plant optimizes the vessel by considerably reducing its size. The parallel plates of this device promote laminarization of the flow and reduce the settling path, facilitating coalescence and separation. The adoption of PlatePack helps to guarantee the removal of impurities, ensuring that the biodiesel meets the desired specifications in terms of purity, physical and chemical characteristics. In addition, the solution not only contributes to the reduction of product losses, resulting in an increase in the overall efficiency of the process, but also stands out for the efficient recovery of by-products, such as glycerol, which can be economically beneficial for the economic viability of the biodiesel plant.

The purification stage in the biodiesel production process begins after decanting the transesterification reaction. Among the most common methods used for this purification is washing with acidified water. The aim of this unit operation is to remove contaminants such as free glycerin, soaps, solid salt residues, excess alcohol and catalyst, in order to obtain a high quality, pure biodiesel. During liquid-liquid extraction, the contaminants in the biodiesel are transferred to the phase with which they have a chemical affinity (water), resulting in the formation of a solute-rich liquid phase. This process can be facilitated by using random packing, which provides a greater surface area of contact between the liquid phases, facilitating mass transfer. This type of filling creates a longer flow path for the dispersed phase, increasing the

contact time between the phases and resulting in greater solute transfer efficiency. In addition, random filling also helps prevent droplets from coalescing, thus avoiding loss of contact area. To guarantee this phenomenon, it is necessary for one phase to be dispersed in the other, allowing the dispersed phase to travel through the continuous phase in the form of droplets. In this context, Clark Solutions offers a complete portfolio of solutions, as well as providing an adequate passage area for the continuous phase, preventing it from accelerating and thus preventing droplet shear.

After separating the phases, it is necessary to eliminate excess methanol, water, catalyst residues and other impurities from the biodiesel to ensure that it meets the specifications. On the other hand, there is the opportunity to recover and purify the glycerol, which contributes significantly to the profitability of the process due to the high added value of this by-product. One of the purification stages involves the stripping operation, which aims to remove unwanted components such as excess methanol and water and other impurities from both biodiesel and glycerol. In the stripper, vapors rise through the column and interact with the liquid to be treated in countercurrent. The internals comprise a MaxiFlow CC liquid distributor and MaxiPac structured packing, which improve separation efficiency. The MaxiFlow CC ensures uniform distribution of the liquid over the filling bed through the high density of irrigation points, which is essential for the good performance of structured fillings. In turn, the MaxiPac structured filling has a geometry with intersections that creates points that facilitate the flow of liquid and gas and a large surface area available, which allows for efficient mass transfer. In addition, Clark Solutions’ MaxiChevron mist eliminator is ideal for handling viscous fluids with dirt content, such as biodiesel and glycerin. The presence of this eliminator at the top of the column is applied to collect the entrained liquid generated by the strong contact between the liquid and gaseous phases in the mass transfer medium, reducing product losses and protecting the performance of the operation.

In the transesterification process for biodiesel production, alcohol, usually excess methanol, is used as a reagent for the reaction to convert triglycerides into methyl esters. It is then necessary to remove the unreacted methanol during the purification of both the biodiesel and the glycerin. The methanol removed in the purification stages has a high water content, but it can be recovered for reuse in the transesterification reaction by means of a rectification operation. In addition, in this same unit operation it is possible to obtain a bottom product composed of water with traces of methanol, which can also be reused in the process. The efficiency of this process is significantly improved by using a system that incorporates a liquid distributor and structured filling. The process begins with an adequate and uniform distribution of the liquid over the filled bed, with the distributor’s role being to provide the irrigation points necessary for the structured fillings to perform properly. The MaxiPac structured bed has a geometry that facilitates the flow of liquid and gas, as well as providing a large surface area. This configuration allows for greater contact between the fluids, which results in an increase in mass transfer efficiency. This operation is similar to the stripper, however, it differs in that it has reflux, which increases the purity of the top product, requiring greater column capacity. In this way, the HC (High Capacity) MaxiPac is suitable for processes that require higher liquid flow rates, without a substantial difference in mass transfer efficiency.

The drying phase consists of the final concentration of the glycerin, since small amounts of water, methanol and impurities may still remain in the product that were not removed in the previous stages. For this purpose, evaporators are used to ensure that the product specifications are met. To optimize the use of energy, multiple-effect evaporators are used. The aim of these devices is to concentrate the solute (glycerin) by forced vaporization of the solvent. For this to happen, heat is supplied and the water is evaporated. This process results in the release of vapor bubbles, which drag small liquid particles as they are released from the liquid surface. Therefore, the presence of MaxiChevron type eliminators is essential for eliminating product losses. In addition, this eliminator is ideal for handling viscous fluids with dirt content, such as biodiesel and glycerin. Using a system with MaxiChevron not only reduces product losses, but also minimizes the maintenance costs associated with them, thus protecting the operation’s performance.