Cristina Fernandes

Wine tartaric stabilization by electrodialysis and its assessment by the saturation temperature

Abstract This investigation of electrodialysis is carried to assess the potassium hydrogen tartrate (KHT) removal for wine tartaric stabilization. The tartaric stability is assessed through the wine saturation temperature. The extent of KHT removal is varied depending on the duration of the electrodialysis up to 24%. The removal of the cations K + , Na + , Ca 2+ and Mg 2+ and of the anions corresponding to tartaric, malic, and lactic acids was monitored. The experiments were performed in a pilot scale electrodialyser with 28 dm 2 of membrane area. Wine saturation temperatures varied linearly with the deionization. For the white wine, a saturation temperature of 14.8 °C and stability up to 0 °C was achieved for a deionization of 14.5% and tartaric acid removal of 10.9%. The lactic and malic acids contents were kept almost constant and the calcium content reduced by 39%. The red wine displayed, without any treatment, a low saturation temperature of 9.2 °C associated to a stable wine.

White wine clarification by micro/ultrafiltration: effect of removed colloids in tartaric stability

Abstract A white wine was clarified by tangential microfiltration (MF) and ultrafiltration (UF). The permeation experiments were carried out in a Dow Lab-unit M20 with a membrane area of 0.036 m 2 . Two membranes were tested, one of MF with a pore size of 1.0 μm and another of UF with a molecular weight cut-off (MWCO) of 100 kDa. They are both made of a fluor polymer and supplied by DSS-Denmark. The operating conditions (pressure and circulation flow rate) were optimised for both membranes. The MF and UF clarification experiments were performed at the same optimal conditions of 1×10 5 Pa transmembrane pressure and 554 l h −1 circulation flowrate. The results were compared in terms of permeate productivity, particle and polysaccharide removal. The polysaccharides were precipitated from the raw wine, the UF permeate and the UF concentrate. Potassium hydrogen tartrate crystallisation induction times were measured at 0°C using hydroalcoholic solutions with and without these polysaccharides. MF and UF presented similar permeate productivities and particle removal. The UF membrane proved to be easier to clean. Polysaccharide removal was low with both membranes: 10% for MF and 16% for UF. The polysaccharides retained by UF did not alter significantly the potassium hydrogen tartrate crystallisation induction times. These induction times are similar for the model solution with the polysaccharides from the raw wine and the UF clarified wine.

A Cost-Based Strategy to Design Multiple Shell and Tube Heat Exchangers

Process Integration has been applied in several industrial processes mainly using standard shell and tube heat exchangers (1-1 or 1-2). The flow arrangement in 1-2 multiple shell and tube heat exchangers involves part counter-current flow and part co-current flow. This fact is accounted for in the design by introducing a F T correction factor into the 1-1 heat exchanger design equation. To avoid some steep regions in the feasible space of heat exchangers design some authors introduce other parameters like Xp or G. Until now it was not possible to have an overall map to give some guidelines of how to choose between the several Xp approaches established in the literature. This paper summarizes the current existing criteria in a general design algorithm (DeAl 12 ) to show a path for the calculations of the main design variables of the heat exchanger. Also a new strategy design algorithm (StratDeAl 12 ) is introduced in this paper to allow the best choice between the existing Xp approaches based on the heat exchanger cost minimisation. Several examples illustrate the advantage of using the developed algorithm and the deviations obtained in the heat exchanger cost if a wrong approach was chosen.

Process integration of a dynamic industrial system

Abstract The aim of this study is to obtain a dynamic modelling and simulation of a Portuguese industrial integrated system composed of three different processes. This work includes the analysis of the optimal integration of the different units, and the study of the effect of some operational and atmospheric conditions on the system to maximize its global thermal efficiency. The cogeneration system was modelled and analysed using the GateCycle 5.34.0.r software. It was concluded that the electric and the thermal power obtained strongly depend on air and economizer cooling water temperatures. The whole integrated process (cogeneration, plate exchangers and salt production unit) is simulated and exploited through gPROMS 2.1.1 . The best start-up conditions were established. The minimum number of ponds required strongly depends on atmospheric conditions, but it can never be less than three in order to obey the operational defined temperature intervals. The scheduling of the evaporation ponds to be put into operation is also investigated in order to enhance the salt production and to optimise the salt harvesting. The simulation indicates that it is better to have the minimum number of ponds working (higher temperatures inside the ponds) and to have a “turbo” pond that receives a larger quantity of heated brine than the others. It was also studied the effect of different atmospheric conditions, and the number of ponds in service required to overcome the more adverse atmospheric conditions. The global process efficiency (thermal and electric power over natural gas consumption) is approximately 92%. However, the effective global thermal efficiency of the whole integrated site (accounting for the existing losses into the open air of the evaporation process) is in the range of 75– 80%, depending on the atmospheric and operational conditions considered.

Phex: a computational tool for plate heat exchanges design problems

This paper presents a computational tool (PHEx) developed in Excel VBA for solving sizing and rating design problems involving Chevron type plate heat exchangers (PHE) with 1-pass-1-pass configuration. The rating methodology procedure used in the program is outlined, and a case study is presented with the purpose to show how the program can be used to develop sensitivity analysis to several dimensional parameters of PHE and to observe their effect on transferred heat and pressure drop.

Influence of brine spray system on the thermal salt recrystallisation process by dynamic simulation

Abstract A distributed dynamic model was built using gPROMS 2.3.7 language for an integrated Process including a cogeneration system, a plate heat exchangers set and a salt recrystallization process. It was analyzed the effect of a simulated spray system model on the integrated process, by comparing the global performance of the system with and without sprays. Due to air drift issues, quasi-random time daily profiles for the allowed operation of the spray system (on-off working time periods) were created. Using three distinctive atmospheric scenarios, several ponds spray distributions schemes were analysed. A sensibility analysis of the salt production was considered by changing the brine flow rate fraction entering in the ponds through taps and by sprays.