Volume 28, Issue 2-3

The chemical industry of today has expanded its focus on process to include products. The question is no longer just how to make a product, but what product to make. The new product-oriented chemical industry has three categories of products with different key characteristics. The first obvious category is commodities, where the key is their manufacturing cost. Styrene produced by Dow and styrene produced by BASF are chemically identical; the issue is who can produce larger quantities at the lowest possible price. The second and third categories of products are less familiar. The second category is molecules, exemplified by pharmaceuticals. The key to the production of pharmaceuticals is not cost, but time to market, that is, the speed of their discovery and production. These products are normally not made using dedicated equipment, but rather in whatever reactors are available. The third category includes products where value is added by a specific microstructure. The key to the success of these products is their function. For example, we do not care why our shoes shine after we have applied polish; we only care that they do shine. It is the shine – not the molecule that produces the shine – that is important. Customers will pay a premium for enhanced function. This paper will review the skill sets of chemical professionals appropriate for this altered chemical industry. While the basic skill set remains appropriate, new skills that include product design will become more central for the chemical professionals. This paper will also suggest a template by which these new products can be designed, and give examples that will aid chemical professionals in achieving this new, broader, more productive chemical enterprise.

This paper reviews the optimization and control of thermal energy storage systems. Emphasis is given to thermal storage applied to combined heat and power systems, building systems, and solar thermal power systems. The paper also discusses how applications of thermal storage can benefit the chemical industry. Optimization of the design and control of thermal storage systems improves plant performance and improves the management of transient energy loads in a variety of applications. In order to maximize the benefits of thermal storage, it is necessary to include advanced multivariate constrained controls, such as model predictive control. Thermal storage also increases system flexibility, allowing the incorporation of intermittent renewable energy sources. The flexibility of thermal storage will play an increasingly important role as utilities implement smart grid technology with time-of-use electricity pricing. Lastly, thermal energy storage improves system economics by reducing required equipment sizes, improving efficiency, and reducing equipment wear.

Inorganic membranes capable of separating carbon dioxide and nitrogen mixture offer potential applications in membrane process for postcombustion carbon dioxide capture. This article provides a concise review of carbon dioxide permeation and separation characteristics and the chemical and thermal stability of microporous carbon, silica, and zeolite membranes. Gas permeation and separation through these microporous membranes generally occur by the solution (adsorption) and diffusion mechanism. All of these membranes are permselective for carbon dioxide over nitrogen because carbon dioxide has a large solubility and mobility in membrane micropores in comparison to nitrogen. These microporous membranes exhibit good carbon dioxide permeance (up to 10 -6 mol m -2 s -1 Pa -1 ) and extremely high carbon dioxide to nitrogen selectivity (up to 500) at around room temperature. The selectivity diminishes above 200°C because the membrane selectivity is controlled by diffusion, and the diffusivity ratio for carbon dioxide to nitrogen is <2. At around room temperature, zeolite (especially Y type) membranes offer attractive properties for use in postcombustion carbon dioxide capture. New membranes such as dense mixed-conducting ceramic-carbonate dual-phase membranes show high carbon dioxide separation performance at high temperatures and may be used in precombustion processes for carbon dioxide capture.

Installation of large-scale compressed air energy storage (CAES) plants requires underground reservoirs capable of storing compressed air. In general, suitable reservoirs for CAES applications are either porous rock reservoirs or cavern reservoirs. Depending on the reservoir type, the cyclical action of air injection and subsequent withdrawal produces temperature and pressure fluctuations within the reservoir. An accurate prediction of these fluctuations is essential for the design of the reservoir and its associated turbomachinery. Being mutually dependent, the selection of the turbomachinery and reservoir characteristics must be conducted simultaneously to obtain an integrated cost-effective plant. The present review is intended to encompass the pertinent literature on the temperature and pressure variations within CAES reservoirs. The principal experimental and operational data sources are described, as well as important results of theoretical modeling efforts. Conclusions derived from those investigations and their relevance to CAES plant designs are discussed.

The population balance equation (PBE) has been used in engineering for more than four decades. However, several misconceptions and misuses can be found in the literature. The present work provides a review of the origins and the derivation of the PBE. The main focus is on the inconsistencies between the theoretical foundation and the usual practice, as well as identifying and addressing some of the issues that cause confusion and contradiction among authors.

This review aims to establish common approaches and equations used in computational fluid dynamics (CFD) analysis for gas-liquid mixing operations and investigate their strengths and weaknesses. The review concluded that with a sufficient computing strength, Eulerian-Lagrangian approaches can simulate detailed flow structures for dispersed multiphase flow with high spatial resolution. Turbulence is an important factor in fluid dynamics, and literature confirmed that k-ε is the most widely used turbulence model. However, it suffers from some inherent shortcomings that stemmed from the assumption of isotropy of turbulence and homogenous mixing, which is suitable for very high Reynolds number in unbaffled stirred vessels. In CFD simulations for gas-liquid systems in stirred vessels, bubble size distribution is the most important parameter; hence, different techniques for formulation of bubble size equations have been investigated. These techniques involve source and sink terms for coalescence or breakup and provide a framework in which the population balance method together with the coalescence and breakup models can be unified into three-dimensional CFD calculations. Different discretization schemes and solution algorithms were also reviewed to confirm that third-order solutions provide the least erroneous simulation results.