📋 Tender Overview
Innovative green chemistry and engineering practices are helping businesses improve the sustainability of their manufacturing while offering substantial cost reductions. In addition to using renewable resources in their processes sebacic acid producers can also reduce solvent use and optimize wastewater quality. This is exactly what one of the worlds largest manufacturers of this chemical achieved thanks to the technologies and expert support provided by Sulzer Chemtech.Widely used for the production of a broad range of industrial products such as plasticizers candles lubricants hydraulic fluids and resins sebacic acid has been in high demand over recent years. Currently its synthesis mostly relies on castor oil which is a bio-based renewable raw material as the substance is extracted from Ricinus communis seeds. This green aspect is one of the main reasons why sebacic acid production dominates castor oils industrial use particularly in China - the second largest producer of this oil.One of the most common synthetic routes to obtain sebacic acid involves the hydrolyzation of castor oil to obtain ricinoleic acid which then undergoes an alkali fusioncracking in the presence of phenol and sodium hydroxide NaOH. Once sebacic acid is purified the resulting wastewater contains large quantities of the initial phenolic compound used.Being a contaminant phenols should be removed from wastewater and properly disposed of. If the concentration of the organic compound is particularly high the effluents are recalcitrant to conventional biological treatments in wastewater facilities. Therefore it is important for production facilities to conduct phenol extraction activities prior to discharging the effluents. Furthermore manufacturers should also look at methods to recover or recycle phenol in their processes.A revolutionary phenol recovery systemThis was the goal of a leading sebacic acid producer in China which wanted to reduce the volume of phenol in its wastewater from 1000 ppm to 300 ppm while reusing the chemical multiple times for alkali fusioncracking. The company aimed to reduce its environmental footprint as well as lowering its costs for consumables as less virgin phenol would be required. To deliver a suitable wastewater purificationphenol recovery system the manufacturer contacted Sulzer the leader in separation and mixing technology.Thanks to its extensive experience in processing technology the companys team was able to develop an innovative liquid-liquid extraction solution to address the needs of the sebacic acid manufacturer. This relies on ricinoleic acid as a key solvent to remove phenol from wastewater. The extracted compound would then be suitable for reuse in the alkali fusioncracking stage creating a sustainable circular process. By doing so the producer would also reduce the costs associated with solvent use as well as energy usage and equipment needed for solvent recovery maximizing the environmental and financial benefits.The equipment selected to conduct the liquid-liquid extraction was the Khni agitated column ECR which is ideal to efficiently separate phenol as well as offering a cost-effective and compact setup. In addition the column supports continuous processing maximizing throughput and energy efficiency.The ECR is composed of a series of agitated compartments that disperse fine droplets of ricinoleic acid within the wastewater feed. As a result phenol is isolated by the solvent from the liquid mixture. More precisely turbine agitators installed in each compartment create a torus-shaped rotary flow pattern and mix the liquid phases radially. In addition perforated plates between each stage reduce back-mixing enhancing the systems separation performance.Fine-tuning innovationTo make sure the solution would remove high volumes of phenol from the wastewater Sulzer and the manufacturer conducted a number of tests and preliminary investigations. Firstly a laboratory shake test to assess the feasibility of the method as well as determining liquid-liquid equilibrium data at different pH. This investigation highlighted that a higher pH would result in a lower content of phenol extracted while alkaline conditions would maximize the volume of recovered phenol.Subsequently on-site pilot-scale tests were conducted to fine-tune the solution to optimize the hydrodynamic behavior of the dispersed and continuous phases. Similarly the team could assess the flooding boundary rotation limit as well as the expected maximum capacity and separation threshold. During this investigation the main challenge was handling the material which is particularly viscous. To overcome this issue Sulzers experts decided to heat the feed material prior to its ingress into the ECR lowering the viscosity.As a result of these tests the optimum design of the ECR was defined. The resulting 30 m 98.4 ft high column with a diameter of 2.4 m 7.9 ft was delivered to the customer. Sulzers specialists subsequently managed and supervised the erection and installation of the system as well as providing key assistance during start-up.The column can process up to 77000 liters of wastewater per hour and is even more effective than initially requested as it can deliver phenol concentrations of 200 ppm well below the original request of 300 ppm. The solution also provides high flexibility as the plant can successfully operate with capacities ranging from 50 to 120.
