This chapter studies the tray types and their distinguishing features. The particular tray selection and its design can materially affect the performance of a given distillation, absorption, or stripping system. Each tray should be designed to give as efficient a contact between the vapor and liquid as possible, within reasonable economic limits. It is impractical in most cases to change the design of each tray to fit calculated conditions. Therefore, the same tray design is usually used throughout the column. Determining the number of theoretical and actual trays in a distillation column is only part of the design necessary to ensure optimum system performance. The interpretation of distillation, absorption, or stripping requirements into a mechanical vessel with internal components requires use of theoretical and empirical data.

Crude oil distillation is a large energy consumer and a large waste generator, so refiners need to balance the economics of processing crude oil to viable fractions. The thermodynamics of multicomponent distillation applies to petroleum, synthetic crude oil, and other complex mixtures. Various advanced integrated and distributed distillation methods can be employed to minimize waste and thus optimize performance oil. The scale of petroleum fractionation/distillation is generally large, involving atmospheric distillation of crude oil, vacuum distillation of bottoms residue, main fractionation of gaseous effluent from catalytic cracking, and main distillation of effluent from thermal coking of various petroleum fractions. They use heavy equipment, which consumes large quantities of energy. The primary raw material for all petroleum processes is crude oil, a naturally occurring liquid produced from wells drilled into the earth. The well depth and techniques used to produce the oil vary widely around the world, as does the nature and chemical composition of the crude oil itself.

Packed towers are used increasingly in a variety of applications in the chemical process industries. The reasons for this are an increase in the availability of design information, the evolution of higher-capacity and higher efficiency mass transfer packings, and improvements in distributors and support plates. Today, packings can be considered for most services where high numbers of theoretical stages are required for mass transfer. Many of the mechanical aspects of tower construction and assembly have an influence on the design and interpretation of tower performance. Every effort should be made to increase the effectiveness of contact between the process streams and to reduce losses by entrainment or wall effects whilst minimizing pressure drop. At the same time the design must be consistent with the economics dictated by the process and type of construction. Most of the fractionating columns in gas-processing plants that were previously equipped with trays can now be filled with packings. Packings, such as slotted rings in metal and plastic saddles, offer large improvements in capacity for absorption and heat transfer applications.

This chapter reviews the vapor–liquid equilibria of some representative mixtures, conditions of bubble of liquid mixtures, and dew points of gaseous mixtures. It also studies the Smoker's equation for estimating the number of plates in a binary mixture, petroleum fractionation, gas processing, dehydration, reactive distillation, the computation of multicomponent recovery, and minimum trays in distillation columns troubleshooting. Computer programs and Honeywell UniSim simulation software are used to illustrate various examples in this chapter. An important unit operation in the chemical process industries is to separate a mixture into its components. This is termed diffusional or mass transfer. A typical chemical plant consists of both reaction and separation units. The raw materials are first purified in a separating unit and then fed to the reactor. A factor representing the efficiency with which raw materials are converted to products is the selectivity. The main techniques used for separations are distillation, absorption, liquid–liquid extraction, drying, leaching, crystallization, and gas adsorption. These processes account for 40% to 70% of both the capital and operating costs in the CPI since they significantly affect energy consumption, product costs, and manufacturing profits.

This chapter discusses several distillation methods such as homogeneous azeotropic distillation, hetrogeneous azeotropic distillation, and reactive distillation. These techniques rely on the differences between the vapor and liquid compositions, as does ordinary distillation, but an additional mechanism is used to alter the behavior of key components. Homogeneous azeotropic distillation is a technique for separating a mixture by adding an entrainer, which then forms a homogeneous minimum or maximum boiling azeotrope with one or more feed components. Where the components of the mixture are not miscible in all proportions with each other, and form two separate phases at some ratios, the azeotrope is heterogeneous. For heterogeneous azeotropes, the vapor-phase composition is equal to the overall composition of two or more liquid phases. Reactive distillation is a process where a chemical reaction occurs in the still, as it is the integration of reaction and distillation into a single unit where the products can be removed to drive a reversible reaction to completion. Separation of the product from the reaction mixture does not require a separate distillation unit, thus saving energy and materials. This technique is especially favorable for systems where equilibrium reactions occur, such as esterification and ester hydrolysis reactions, but undesirable when one of the desired products decomposes. The chapter also studies certain case studies such as manufacture of methyl acetate and reactive distillation of methyl acetate

Many operations in the chemical process industries (CPI) are dependent to a great extent on effective mixing of fluids. While mixing refers to any operation used to change a non-uniform system into a uniform one (i.e., the random distribution into and through one another, of two or more initially separated phases), agitation implies forcing a fluid by mechanical means to flow in a circulatory or other pattern inside a vessel. Mixing is an integral part of a chemical or physical process such as blending, dissolving, dispersion, suspension, emulsification, heat transfer, and chemical reactions. Mixing of fluids is necessary in many chemical processes. It may include mixing of liquid with liquid, gas with liquid, or solids with liquid. Agitation of these fluid masses does not necessarily imply any significant amount of actual intimate and homogeneous distribution of the fluids or particles, and for this reason mixing requires a definition of degree and/or purpose to properly define the desired state of the system. Table 7-1 summarizes the principal purposes for agitating fluids.

Practically every process operation requires the separation of entrained material or two immiscible phases in a process. This may be either as a step in the purification of one stream, or a principal process operation [ 1 ]. These separations may be as follows: 1. liquid particles from vapor or gas

The subject of process safety is so broad in scope that this chapter must be limited to the application, design, rating, and specifications for process overpressure-relieving devices for flammable vapors and dusts; process explosions, runaway chemical reactions and external fires on equipment; and the venting or flaring of emergency or excess discharge of gases to a vent flare stack. The subject of fire protection cannot be adequately covered; however, the engineer is referred to texts dealing with the subject in a thorough manner [ 1. ; 2. ; 3. ; 4. ; 5. ; 5. ].

Pumping of liquids is almost universal in chemical and petrochemical processes. The many different materials being processed require close attention to selection of materials of construction of the various pump parts, shaft sealing, and the hydraulics of the individual problems. A wide variety of pumps types have been developed to satisfy the many special conditions found in chemical plant systems; however, since all of these cannot be discussed here, the omission of some does not mean that they may not be suitable for a service. In general, the final pump selection and performance details are recommended by the manufacturers to meet the conditions specified by the process design engineer. It is important that the designer of the process system be completely familiar with the action of each pump offered for a service in order that such items as control instruments and valves may be properly evaluated in the full knowledge of the system.