Chemical Process Engineering & Simulation

Problem Statement And Given Data: Given the following data and information, it is required to design a forced circulation crystallizer of the type shown in Figure 1 operating under vacuum. Figure 1 Forced circulation (FC) evaporation crystallizer.   Feed (an aqueous solution) rate, Qi = 15 m 3 /h, feed concentration, Ci = 200 kg/m 3 solution; feed temperature = 55 o C; average density of the solution = 1100 kg/m 3 and average specific heat = 0.90 kcal/kg. o C; operating pressure = 100 mm Hg (660 mm Hg vacuum); boiling point elevation of the saturated solution = 13 o C; saturation concentration at the crystallization temperature = 250 kg/m 3 ; magma density allowed, M T = 350 kg crystal/m 3 solution; crystal growth rate determined experimentally under the conditions of the crystallizer, G = 4.67 x 10 -8 m/s; crystal density = 1700 kg/m 3 ; desired dominant crystal size L D = 0.8 mm; heat of vaporization of water at the temperature of the crystallizer = 570 kca...

Crystallizer Design Procedure:         The following steps are outlined for the design of a crystallizer of the Forced Circulation (FC) type. Although these calculations are limited to that style, the procedure has general application to other types of equipment. Choose the type of crystallizer that best meets the requirements for (a) product size , (b) product quality , (c) process economics , and (d) scale of operation. See Table 1 for a list of the general characteristics of crystallization equipment. Make a material balance , heat balance , and flow sheet .  Decide what retention time is required to make the required product, (a) by experience, and (b) from growth and nucleation rate data. Size the body on the basis of the controlling volume required for crystal retention with due consideration for the minimum cross-section required for vapor (evaporation) release. Size the heat-transfer surface (for evaporative types) a...

Guidelines For Crystallizer Selection: This is part one of a two-part feature that examines the fundamentals and discusses crystallization equipment selection and design. Part one focuses on the basics, providing guidance for crystallization equipment selection. Part two will focus on the crystallizer design procedure. The guidelines for crystallizer selection and operation in various chemical industry processes are discussed below. Information Required For Evaluation:         Before a potential crystallizer application can be properly evaluated, it is necessary to have certain basic information regarding the material to be crystallized and its mother liquor. Typical solubility curves are shown in Figure 1. Is the material a hydrated or anhydrous material? What is the solubility of the compound in water or any other solvents under consideration and how does this change with temperature and pH? Are there other compounds in the...

Process Intensification: Process Intensification (PI) has been defined as “a philosophy of plant design and construction whereby a given performance is achieved in very much smaller equipment - typically with a volume reduction of two or three orders of magnitude” [2]. These reductions in size can come from using smaller individual pieces of equipment or by cutting the number of unit operations or pieces of equipment used in the process. A volume reduction of a factor of two or more (not necessarily two orders of magnitude) was considered by [3] to be drastic enough to be labelled PI and this work broadened the definition of PI to include a dramatic increase in production capacity within a given volume, a significant decrease in energy consumption per ton of product, or large decreases in waste or by-product formation. The concept of Process Intensification (PI) was developed within ICI in the late 1970’s when Colin Ramshaw began to look into various ways of reducing the size...