Total site methodology as a tool for planning and strategic decisions

A Total Site (TS) is defined as a set of processes (industrial plants, residential, business and agriculture units) linked through the central utility system. The utility system incorporates a number of operating units such as boilers, steam turbines, gas turbines and letdown stations. Many sites are using the TS system representation. Heat Integration at TS level has been well developed and successfully implemented. However, sites typically develop with time and even minor changes/extensions can affect TS heat recovery significantly. It is beneficial to plan their strategic development in advance, to increase or at least not to decrease the rate of heat recovery when integration of additional processes takes place. Even when this has not been done at the initial stage, the TS methodology can still be used as a tool for the strategic planning decision making. This work illustrates how the TS methodology can contribute to the strategic development and the extension planning of already existing TS. The aim is to reveal the potentials for Heat Integration, when new units or processes are considered for the inclusion in the TS. Moreover, some operating parameters (e.g. temperature or capacity) of the unit can be proposed to achieve the best possible heat recovery. The degrees of freedom for TS changes can be on two levels: (i) only adding an operating unit to the current utility system (the Total Site Profiles remain the same) or (ii) changing of the TS by including more processes (the Total Site Profiles are changed). The first group of changes includes the integration of heat engines to produce electricity utilising heat at higher temperature and returning it to the system at lower temperature, which is still acceptable for the heat recovery and simultaneously for the electricity production. The second group of changes is more complex. For evaluating these changes a plus/minus principle is developed allowing the most beneficial integration of new units to the TS. Combinations of both types of changes are also considered

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

Targeting Minimum Heat Transfer Area for Heat Recovery on Total Sites

This paper upgrades the Total Site integration methodology, when accounting for a trade-off between capital and heat recovery by selection of optimal temperature levels for intermediate utilities and therefore, decrease capital cost. Heat transfer area for recuperation in Total Site is a two-fold problem and it depends on the Sink Profile on one side and on the Source Profile on another. The resulting temperature of intermediate utility is a result of a trade-off since the heat transfer area on Source side is decreasing, when temperature of IM is decreasing, however increased on Sink side. In the opposite higher intermediate utility temperature leads to higher area on the Source side and lower on Sink side. The temperature of each intermediate utility may be varied between specified lower and upper bounds subject to serving the Sink and Source Profiles

Footprints Evaluation of China's Coal Supply Chains

This work presents the China's coal supply chains and environmental and social footprints associated with them. Those impacts are based on a life cycle of coal from cradle-to-gate. Several environmental footprints are considered, such as carbon, water, nitrogen, sulphur and other, as well as social footprints including number of accidents and radioactivity footprints. At last, several currently used footprints prevention steps are analysed within China, such as CO2 sequestration, desulphurisation and denitration

Water Availability Footprint Addressing Water Quality

The increasing issue of water quality degradation has affected the availability of water. The consideration of water quality is becoming more important for water minimisation. There is a need to integrate water quality into the current water assessment framework. This study tries to involve the water quality into the widely used water footprint assessment framework in order to quantify the water usability changes during the water use process. Based on water footprint concepts from international standard ISO 14046, water availability is further interpreted to emphasize the impact of water quality on the usability. An effective water availability footprint is defined as the quantitative and qualitative extent of a certain body of water which meets the needs of a certain purpose of water use. A water quality index is proposed to quantify the contribution of water quality on water availability, and two approaches of calculating water quality index are discussed, in order to explore the possibility of involving water quality into the water availability footprint assessment. Based on the definitions and framework, a case study is conducted to illustrate the features of this framework, and 3 outflows with different water quality are set to discuss the impact of different water quality profiles on the calculation of water availability footprint. It shows that water quality profiles can have a remarkable influence on the calculation. For the case with an outflow of F2-1, the water availability footprints with minimum water quality index, average water quality index and the volumetric water footprints as 1,600 m3, 1,277 m3, and 1,000 m3. This indicator can determine the consumptive water use and also quantify the exploitation of water quality. The involvement of water quality regarding multiple contaminants in water footprint assessment should be further investigated in future studies