new question
I. Introduction: In a chemical engineering, a separation processes are techniques to achieve mass transfer which convert a mixture into two or more desired products. Separation processes are defined as processes that use chemical, physical or electrical forces to separate elements from a mixture. The aim of these separation processes is to obtain a desired level of purity in any process stream. There are three steps towered designing a separation processes. First, is determining the physical properties of the components. An examples of these physical properties can be concentration, solubility, specific gravity, boiling point and chemical potential. Second, is designing an initial process to determine the technical possibility of a given separation process. Last, is determining the economic possibility of a given process and determine either the process is reasonable or not. The module that used in this project gives 15 different types of separation processes. II. Discussion: Separation Process Type of Separation Description Figure Absorption Gas - Gas Different solubility of gas can be separated by using liquid in a packed column. The column size is depend on the mass transfer. Adsorption Liquid – Liquid Gas – Gas Liquid or gas feed with the component to be removed is passed through an adsorption solid bed. The basis of this separation is the different in the affinity of the components. Chemical Reaction All Phases The basis of this separation is to transform components from their complex form to one that is easier to separate or no longer needs to be separated. Condensation Gas – Gas Boiling point of various component is the basis of this process. Whereas, a gaseous mixture is cooled in a vessel until the desired components have condensed to a liquid. Crystallization Liquid – Liquid The freezing point of the components is the basis of this process. The desired components from a liquid solution is cooled in a crystallizer. Cyclone Gas – Liquid Gas - Solid Different densities of gas stream and liquid or solid particles enter the feed stream. A centrifugal force is used in this process; whereas, the solid particles will settle in the bottom and gas will exit out from the top. Distillation Liquid – Liquid The basis of this process depend on the differences in volatilities. The feed is separated using steam based on the boiling point of the mixture that need to be separated. The liquid exit from the bottom and the gas from the top. Drying Liquid – Solid Heat is used is this process. The wet solid enters a dryer and the liquid is caused to evaporate from the solid by the addition of heat. Evaporation Liquid – Liquid A miscible liquid containing nonvolatile solutions in a volatile solvent is heated. Solvent is evaporated as a gas and the concentrated solution will settle in the bottom. Extraction Liquid – Liquid This process is based on the solubility of different species. The feed mixture is mixed with immiscible solvent. The desired substance will dissolve into the solvent. Leaching Solid – Solid It is a solid-solid extraction using liquid solvent. The solute solid transfers from a mixture of solid to liquid solvent. Membranes Liquid – Liquid Liquid – Solid Gas – Gas Gas – Solid Solubility and the rates of permeation are the basses of this process. A gas or liquid feed enters membrane which allows some particles to pass through. Settling (Sedimentation) Liquid – Liquid (Immiscible) Liquid – Solid Solid – Solid Gas – Solid Gravity is the basis of this process. The feed is passed through a vessel with suitable residence time. The lighter components will float, and the denser will settle to the bottom. Stripping Liquid – Liquid This process works based on the volatility of the liquid mixture. A stripping steam is injected from the bottom of the stripping column taking the more volatile components to the top and leaving the less volatile to exit from the bottom. Vacuum Filtration Liquid – Solid A filter medium is used in this process. The pores of the filter are a way in which the liquid can pass through and the solid cannot. III. Results: Property Physical Property Data Chemical Formulas para p-C6H4-2CH3 meta m- C6H4-2CH3 Colors Colorless Colorless Formula Weights 106.17 g/mole Nuclear Changes +58 Valences Neutral Densities 0.864 g/mL 0.861 g/mL Boiling Points +138.3 °C +139.1 °C Melting Points +13.3°C -47.9 °C Particle Sizes Both Particles have the Same Size Volatility Ratio 1.02 Temperature of System 30 °C Pressure of System 1 atm Table (1): Physical Properties of Xylene Isomers (i.e. Para, and Meta) First separation process problem given by this simulator is a separation of Xylene Isomers. As we know, Xylene has three different isomers, p-xylene (para), m-xylene (meta), and o-xylene (ortho). The process of this problem is to separate p-xylene from the other isomers. In order for this process to achieve correctly, a feed stream with a purity of at least 85% p-xylene is required. There are 8 out of 15 processes are applicable to separate p-xylene from the other isomers. Four of these eight separation were approved (i.e. Adsorption, Chemical Reaction. Crystallization, and Extraction). The following reasons explain why these processes were chosen: 1- Adsorption: The solid adsorbent (i.e. zeolite) will adsorb p-xylene up to 95.5%. 2- Chemical Reaction: The amphorous silica-alumina catalyst will convert the m-xylene to p-xylene up to 95%. 3- Crystallization: Difference in melting point of these isomers. 4- Extraction: A mixture of HF-BF3 can be added into the process mixture which allows 99% of the m-xylene to settle into a more basic phase. The other four separation processes that are applicable but not approved are Distillation, Stripping, Membranes and Settling. Whereas, the reason that distillation and stripping were not approved because of the low relative volatility (i.e. 1.02) [2] of para and meta isomers. Membranes were not approved because of the particles size, and settling because of the identical density between para (0.864 g/mL) and meta (0.861 g/mL). Property Physical Property Data Chemical Formulas TCP 2,4,6-C13C6H2OH H2O Colors Colorless Colorless Particle Shapes Ring Bent Formula Weights 197.45 g/mole 18 g/mole Nuclear Changes +98 +9 Valences Neutral Neutral Densities 1.49 g/ml 1 g/ml Boiling Points +246 °C +100 °C Melting Points +69.5 °C 0.0 °C Particle Sizes TCP is Much Larger than H2O Volatility Ration 1.3 Temperature of System 25 °C Pressure of System 1 atm Table (2): Physical Properties of TCP and Water The second separation process problem is a Removal of Organic Materials from Wastewater. The goal of this separation is to separate water from the hazardous pollutant Trichlorophenol (TCP). The concentration of TCP must drop 50% to be below the Environmental Protection Agency (EPA). There are nine processes technique out of 15 are applicable; five were approved from these nine processes. 1- Adsorption: A carbon adsorption uses as a unit to remove TCP. 2- Chemical Reaction: Ozonation is a technique uses to oxidize the TCP to an acidic compound which is less toxic. 3- Crystallization: Differences in freezing points between water and TCP. 4- Membranes: Reverse Osmosis membrane will help lowering the concentration of TCP. 5- Stripping: Air uses to remove TCP. The other four Separation processes that are applicable but were not approved are Distillation, Evaporation, Extraction, and Settling. The relative volatility ratio (1.3) [2] between water and TCP is the reason that distillation was not approved. TCP needs long process to removed it from water; therefore, evaporation cannot be used. Last, extraction and settling were not approved because of the similar densities of water (1 g/mL) and TCP (1.49 g/mL). Physical Physical Property Data Component IPA Oxygen Nitrogen Chemical Formulas C3H7OH O2 N2 Colors Colorless Particle Shapes Tetrahedral Linear Formula weights 60.11 g/mole 32 g/mole 14 g/mole Nuclear Changes +30 +16 +7 Valences Natural Densities 0.70 g/L 1.14 g/L Boiling Points 82.4 °C -199.0 °C -195.8 °C Melting Points -89.3 °C -218.0 °C -209.9 °C Particle Sizes All Particles have the Same Size Volatility Ratio 1.02 Temperature of System 25 °C Pressure of System 1 atm Table (3): Physical Properties of IPA and Air Third and last separation process problem is Tray Dryer Solvent Recovery. This process has a mixture of solid crystal components with a liquid solvent (i.e. Isopropanol (IPA)). The problem asked to find some appropriate methods to separate IPA from the air after the crystals dried. This is a type of a gas-gas separation process, and the EPA standard of IPA in air is 90% control of each day emissions. There are five methods that applicable for this separation. Four out of these five were approved. 1- Absorption: liquid phase may be added which allows to remove the IPA. 2- Adsorption: A carbon adsorption column can be used which help remove IPA from the Air. 3- Chemical Reaction: Since IPA is a hydrocarbon component, a combustion reaction can be used to burn it. 4- Condensation: Difference in boiling point between air and IPA allows IPA to condense out first. The only method that is applicable but was not approved is membranes. The reason behind that might be because of the equal sizes of IPA and air.