Preferential Trade Agreements and the Optimal Liberalisation of Agricultural Trade

Recent years have seen a rapid growth in the number of preferential trade agreements (PTAs) between developed and developing economies. Typically however many of these PTAs only incorporate a partial liberalisation of food and agricultural trade by developed economies. This paper reports the results from simulations conducted using a global comparative static model CGE model that has been calibrated with data from the GTAP database (version 5). Using the EU RSA FTA as an example the results indicate that the optimal degree of food trade liberalisation by the EU is less than 100 percent, and declines appreciably after the optimum. Qualitatively similar results emerge for South Africa. However, the welfare gains for South Africa increase rapidly with the increasing liberalisation of EU food and agricultural trade, while the welfare gains for the EU increase slowly with the increasing liberalisation of South African food trade. These results indicate that bilateral trade negotiations between developing and developed countries may involve a complex bargaining process, wherein the payoffs from different strategies are neither necessarily intuitively obvious nor are they necessarily consistent with the full liberalisation of food trade by developed economies

A derivative method for minimising total cost in heat exchanger networks through optimal area allocation

This paper presents a novel Cost Derivative Method (CDM) for finding the optimal area allocation for a defined Heat Exchanger Network (HEN) structure and stream data, without any stream splits to achieve minimum total cost. Using the Pinch Design Method (PDM) to determine the HEN structure, the approach attempts to add, remove and shift area to exchangers where economic benefits are returned. From the derivation of the method, it is found that the slope of the ε-NTU relationship for the specific heat exchanger type, in combination with the difference in exchanger inlet temperatures and the overall heat transfer coefficient, are critical to calculating the extra overall duty each incremental area element returns. The approach is able to account for differences in film coefficients, heat exchanger types, flow arrangements, exchanger cost functions, and utility pricing. Incorporated into the method is the newly defined “utility cost savings flow-on” factor, θ, which evaluates downstream effects on utility use and cost that are caused by changing the area of one exchanger. To illustrate the method, the CDM is applied to the distillation example of Gundersen (2000). After applying the new CDM, the total annual cost was reduced by 7.1 % mainly due to 24 % less HEN area for similar heat recovery. Area reduction resulted from one exchanger having a minimum approach temperature (ΔTmin) of 7.7 °C while the other recovery exchangers had larger ΔTmin values. The optimum ΔTmin for the PDM was 12.5 °C. The CDM solution was found to give a comparable minimum total area and cost to two recently published programming HEN synthesis solutions for the same problem without requiring the increased network complexity through multiple stream splits

Total site targeting with stream specific minimum temperature difference

The paper focuses on extending traditional Total Site Integration methodology to produce more meaningful utility and heat recovery targets for the process design. The traditional methodology leads to inadequate results due to inaccurate estimation of the overall Total Site heat recovery targets. The new methodology is a further development of a recently extended traditional pinch methodology. The previous extension was on the introduction of using an individual minimum temperature difference (δTmin) for different processes so that the δTmin is more representative of the specific process. Further this paper deals with stream specific δT min inside each process by setting different δT contribution (δTcont) and also using different δTcont between the process streams and the utility systems. The paper describes the further extended methodology called stream specific targeting methodology. A case study applying data from a real diary factory is used to show the differences between the traditional, process specific and stream specific total site targeting methodologies. The extended methodology gives more meaningful results at the end of the targeting with this avoiding the over or under estimated heat exchanger areas in the process design

Carbon Emissions Pinch Analysis (CEPA) for emissions reduction in the New Zealand electricity sector

Carbon Emissions Pinch Analysis (CEPA) is a recent extension of traditional thermal and mass pinch analysis to the area of emissions targeting and planning on a macro-scale (i.e. economy wide). This paper presents an extension to the current methodology that accounts for increased demand and a carbon pinch analysis of the New Zealand electricity industry while illustrating some of the issues with realising meaningful emissions reductions. The current large proportion of renewable generation (67% in 2007) complicates extensive reduction of carbon emissions from electricity generation. The largest growth in renewable generation is expected to come from geothermal generation followed by wind and hydro. A four fold increase in geothermal generation capacity is needed in addition to large amounts of new wind generation to reduce emissions to around 1990 levels and also meet projected demand. The expected expansion of geothermal generation in New Zealand raises issues of GHG emissions from the geothermal fields. The emissions factors between fields can vary by almost two orders of magnitude making predictions of total emissions highly site specific

Ensuring cost-effective heat exchanger network design for non-continuous processes

The variation in stream conditions over time inevitably adds significant complexity to the task of integrating non-continuous processes. The Time Averaging Method (TAM), where stream conditions are simply averaged across the entire time cycle, leads to unrealistic energy targets for direct heat recovery and consequently to Heat Exchanger Network (HEN) designs that are in fact suboptimal. This realisation led to the development of the Time Slice Method (TSM) that instead considers each time interval separately, and can be used to reach accurate targets and to design the appropriate HEN to maximise heat recovery. However, in practise the HENs often require excessive exchanger surface area, which renders them unfeasible when capital costs are taken in to account. An extension of the TSM that reduces the required overall exchanger surface area and systematically distributes it across the stream matches is proposed. The methodology is summarised with the help of a simple case study and further improvement opportunities are discusse

WinGEMS modelling and pinch analysis of a paper machine for utility reduction

A multi-ply paper machine process model was developed using WinGEMS and the stream data produced was used to conduct a pinch analysis. The product stream was excluded from the analysis and the composite curves display the enthalpy contained only in the inputs and outputs to the various sections of the paper machine. The pinch point for the overall paper machine was 55.9 C while the minimum hot utility target was 170 MW. Occurrences of cross pinch heat transfer were identified and discussed. Heat recovery options for heating of the fresh water showers, using waste heat streams were investigated. Steam savings of over 14 MW could be achieved by recovering heat from two waste streams that currently go directly to drain with no heat recovery taking place. The use of pinch analysis for utilities targeting under non-continuous conditions was examined. Finally, the feasibility of integrating non-conventional technologies, such as heat storage, is discussed