Pinch Analysis

The rising cost of energy and environmental concerns have led the brewing industry to search for techniques of reducing energy consumption in brewery operations. In this paper, pinch analysis was applied to a typical Ugandan based brewery process to target for the energy requirements of the process. Hint software was used for the analysis. At the chosen ΔTmin of 10˚C, the minimum cooling and heating utility requirements of the brewery studied were determined as being 4862.21 kW and 8294.21 kW respectively, with a pinch temperature at 68˚C. It was observed that using the technique, 1806.59 kW of energy could be recovered through process to process heat exchange which presented an energy saving potential of 21.5%. It is recommended that results from this study could be used in the design or retrofit of a heat ex-changer network of a brewery for improved energy efficiency. Considerations can also be made for other values of ΔTmin.

The combined sugar and ethanol production process from sugar cane is a paradigmatic application for energy integration strategies because of the high number of hot and cold streams involved, the external hot utility requirement at two temperature levels for juice evaporation and crystallization, and the
electricity demand for juice extraction by milling. These conditions make it convenient to combine the sugar-cane process with a CHP system fuelled by bagasse, the main by-product from juice extraction. The strategies, tools and expertise on energy integration developed separately by the research teams authoring this paper are applied here jointly to optimize the synthesis and the design parameters of the
process and of the total site starting from the basic idea of dissociating the heat exchanger network design problem from the total site synthesis problem. At first the minimization of the external heat requirement for the process alone is pursued and results show that a one third reduction can be achieved
by optimal heat integration. Then the use of the by-product bagasse for on-site power generation is considered and two bagasse-fuelled CHP systems are optimized along with some parts of the sugar and ethanol production process in order to obtain maximum total site net power. Results show a variety of
interesting scenarios of combined sugar, ethanol and electricity production plants with considerably high electricity output.

The results of the preliminary energy audit in the yeast and ethyl alcohol plant reviled the huge amount of thermal losses, primary caused by waste heat in exhausted process streams. Since the production of yeast and ethyl alcohol is performed by the both, continuous and discontinuous, process operations, the process design problem, necessary to accomplish the efficient waste heat recovery, is considered as the complex heat integration problem. The optimal process streams parameters due to different thermodynamic and economic criteria are obtained by the batch pinch analysis, based on the time slice model. These parameters are used for the design of heat exchanger networks; some with and other without heat storages. Design solutions increase the utilization of waste heat and considerably improve the plant's energy efficiency for a relatively short payback period.

Heat and mass such as water and solvents are two key utilities in process industry. Simultaneous reduction of both utilities can reduce plant capital as well as operating costs. Though there are mathematical modeling techniques that can produce global optimal solutions, graphical methods are often preferred to provide insights through visualization. This paper presents a new graphical approach named superimposed mass and energy curves (SMEC) for simultaneous mass and heat reduction applicable to both mass transfer-based and non-mass transfer-based systems. Source and demand allocation curves and heat surplus diagram are superimposed on a plot of flowrate versus mass load/temperature to guide design towards the minimum utility targets. This method provides a useful visualization tool on the simultaneous effects of mass and energy reduction. Application of the graphical procedure on case studies involving water and ammonia solvents achieved the minimum mass consumption and near optimal energy usage.► Current graphical techniques deal with heat and mass reduction either independently or sequentially. A new superimposed mass and energy curves (SMEC) have been introduced to simultaneously target and design the minimum heat and mass recovery network. ► The SMEC is a plot of source and demand composite curves superimposed on the new Energy Match Diagram (EMD) plot introduced in this work. ► The graphical SMEC technique is applicable to both mass transfer-based and non-mass transfer based systems, to both flowrate-deficit case and mass load-deficit cases, and to complex design problems involving multiple pinches. ► Application of the graphical technique on two case studies results in minimum mass consumption and near optimum energy usage. ► The new SMEC graphical technique is superior in terms of providing design insights through visualization, as well as in terms of versatility.

Extractive distillation is an alternative for alcohol dehydration processes that has shown to be more effective than azeotropic distillation and, in close proximity, to be very competitive against the process that uses molecular sieves. Glycols have shown be the most effective solvents in extractive distillation, mainly ethylene glycol and glycerol. In this work, an extractive distillation column was simulated with

In this paper, linear programming formulations, complemented by concept based pinch analysis results, are developed to target the minimum energy requirements in a heat integrated fixed flow rate water allocation networks. These formulations can be applied for the cases of heat integration through isothermal and non-isothermal mixing in water allocation networks involving single as well as multiple contaminants. The earlier reported approaches are based on linear programming formulation for the case of isothermal mixing and either mixed integer non-linear programming or discontinuous non-linear programming formulations for the case of non-isothermal mixing. It has been observed that the earlier reported methodologies produce sub-optimal results for the case of non-isothermal mixing. However, the proposed methodologies produce the optimum results because of the rigorously proved linear formulation. Utility requirements for isothermal as well as for non-isothermal mixing cases are compared over a range of minimum approach temperatures, to evaluate the energy performance using illustrative examples.► Linear programming formulations to target the minimum energy requirements in a heat integrated water allocation networks. ► Linear programming formulations are based on rigorously proved mathematical results. ► These formulations can be applied for the cases of heat integration through isothermal. ► Non-isothermal mixing in water allocation networks involving single as well as multiple contaminants. ► Formulation for heat mixing via non-isothermal mixing in water part networks are also mixed integer non-linear programming.

Demand for bioethanol has grown considerably over the last years. Even though Brazil has been producing ethanol from sugarcane on a large scale for decades, this industry is characterized by low energy efficiency, using a large fraction of the bagasse produced as fuel in the cogeneration system to supply the process energy requirements. The possibility of selling surplus electricity to the grid or using surplus bagasse as raw material of other processes has motivated investments on more efficient cogeneration systems and process thermal integration. In this work simulations of an autonomous distillery were carried out, along with utilities demand optimization using Pinch Analysis concepts. Different cogeneration systems were
analyzed: a traditional Rankine Cycle, with steam of high temperature and pressure (80 bar, 510
C) and back pressure and condensing steam turbines configuration, and a BIGCC (Biomass Integrated Gasification Combined Cycle), comprised bya gas turbine set operating with biomass gas produced in a gasifier that uses sugarcane bagasse as raw material. Thermoeconomic analyses determining exergy-based costs of electricity and ethanol for both cases were carried out. The main objective is to show the impact that these process improvements can produce in industrial systems, compared to the current situation.