distillation equipment

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This post was last edited by leteblink on 2010-5-28 at 12:06.
**Distilling Equipment**
**Definition**
Distillation is a separation process based on the relative volatility of the materials to be separated and on a change in phase of the original mixture. In the simplest example, a volatile component of a liquid mixture is vaporized by the application of heat, leaving a relatively nonvolatile component as a liquid residue. With slight exceptions, distillation differs from evaporation and drying in the means provided for saving the volatile component, in the degree of difficulty of separation, and in the completeness of the operation when more than one volatile component is to be separated from each other. Generally, distillation applies to liquid mixtures; notable exceptions include destructive distillation of wood and coal, where liquid fractions are separated from a solid. Modern chemical engineering treats distillation as a unit operation to which several principles and design methods can be applied, regardless of the materials being processed or the industry involved. The trend in equipment design is away from specialized designs for different industries toward designs tailored to the specific needs of a particular process.

**Scope**
Distilling equipment comes in many types, arrangements, and sizes to suit the conditions of the mixture being processed and the products desired. The choice of equipment type depends on the physical properties of the material to be distilled, the degree of separation required, and the scale of the operation. The size of the components in the distillation system is determined through engineering design, using established methods outlined in handbooks and textbooks, with input from the extensive experience of manufacturers of distilling equipment. This chapter aims to guide the selection of equipment based on type and arrangement, but it omits the detailed explanations required for thorough design instructions.

**Theory**
Calculations related to distillation, used to determine the degree of separation and the size of the equipment needed, are based on vapor-liquid equilibrium data, heat and mass balances, allowable vapor velocities, separation rates, and heat transfer rates. These calculations are simplest for batch distillation of a single volatile component from a nonvolatile residue. They become more complex as the number of components increases, whether in batch or continuous processes. Although it is assumed that the reader is not seeking detailed guidance on equipment design, it is still important for them to understand the information necessary to carry out a complete design. The first requirement is physical data for each component across the range of temperatures and pressures involved in the process, including: (1) Specific gravity of the liquid; (2) Specific volume of the vapor; (3) Solubility of each component in the others and in water, if open steam is used; (4) Specific heat of the liquid and vapor; (5) Latent heat of vaporization; (6) Viscosity of the liquid and vapor; (7) Surface tension (at least approximate values for estimating entrainment); (8) Thermal conductivity of the liquid and vapor (for heat transfer calculations); (9) Foaming characteristics; (10) Corrosion rates on potential materials used in construction.

**Classification of Distilling Equipment**
Distilling equipment can be broadly classified into equipment for batch operations and equipment for continuous operations. The characteristics of such equipment are primarily determined by the difficulty of the separation task at hand. Simple separations are achieved through “simple distillation,” while more difficult separations require “fractionation.” A classification of distilling equipment is shown in Fig.4.1 (where is this figure? – leteblink). The conditions under which distilling equipment is designed vary widely. Temperatures can range from those of liquid nitrogen (used for low-temperature gas separation) to 700–800 °F in certain petroleum refining processes. Pressures can range from low vacuum to 1000 psi, and throughput can range from a few gallons per hour to 50,000 gallons per hour. The types of separations involved can range from the easy separation of hexane from practically nonvolatile vegetable oils to the challenging separation of heavy water from normal water (with a boiling point difference of 2.5 °F). Thank you to the original poster for sharing this information; such content might also be found in professional English-language books. Interested friends can find relevant information in the data section. -leteblink