Heat pump integration for total site waste heat recovery

Total Site Heat Integration (TSHI) promotes energy recovery between processes to enhance overall energy efficiency of an industrial complex. Various industrial waste heat utilisation technologies have been studied to improve the energy efficiency of energy system. Vapour compression as an open loop heat pump system has good potential to be used to upgrade the waste heat to useful heat in Total Site systems. Vapour compression systems upgrade low grade waste heat by supplying a low quantity of high pressure steam (thermocompressor) or mechanical work (mechanical-compressor) to generate higher pressure steam, as is common with evaporation systems. The vapour compression system recovers the latent heat content of the industrial waste heat, which reduces cooling demand, decreasing the demand for high quality steam and reducing boiler load. This paper introduces an effective Total Site targeting methodology to integrate open cycle heat pump systems, i.e. vapour compression technologies, into an integrated industrial energy system for enhancing overall site energy efficiency. Industrial waste heat and high quality steam demand are able to be reduced simultaneously though this integration. The energy reduction and cost-benefit of thermo-compressor and mechanical-compressor installations are compared through a literature case study. The case study showed a deficit of heat at the MPS and a surplus of heat the LPS, which was identified as a candidate for compression according to the appropriate placement principle for heat pumps. For the case study, a four-stage mechanical vapour compression system and two-stage thermal vapour compression system resulted in an energy cost reductions of 343,859 USD/y and 168,829 USD/y

Organic rankine cycle and steam turbine for intermediate temperature waste heat recovery in total site integration

The utilization of waste heat for heat recovery technologies in process sites has been widely known in improving the site energy saving and energy efficiency. The Total Site Heat Integration (TSHI) methodologies have been established over time to assist the integration of heat recovery technologies in process sites with a centralized utility system, which is also known as Total Site (TS). One of the earliest application of TSHI concept in waste heat recovery was through steam turbine using the popular Willan’s line approximation. The TSHI methodologies later were extended to integrate with wide range of heat recovery technologies in many literatures, whereby Organic Rankine Cycle (ORC) has been reported to be the one of the beneficial options for heat recovery. In general, the medium to high temperature waste heat is recovered via condensing/backpressure steam turbine, whereas ORC is targeted for recovering the low temperature waste heat. However, it is known that condensing turbine is also abled to generate power by condensing low grade steam to sub-ambient pressure, which is comparable with ORC integration. In this work, the integration of ORC and condensing turbine was considered for a multiple-process system to recover intermediate temperature waste heat through utility system. This study presented a numerical methodology to investigate the performance analysis of integration of ORC and condensing turbine in process sites for recovering waste heat from a centralized utility system. A modified retrofit case study was used to demonstrate the effectiveness application of the proposed methodology. The performances of ORC and condensing steam turbine were evaluated with the plant total utility costing as the objective function. The turbine integration was found to be more beneficial in the modified case study with lower utility cost involved. However, the capital cost has not been considered in the analysis

Assisted heat transfer and shaft work targets for increased total site heat integration

Total Site Heat Integration (TSHI) provides a valuable framework for practical integration of multiple energy users. Previous studies have introduced the idea of utilising process heat recovery pockets to assist TSHI. However, these methods are shown to be effective for only some Total Site (TS) problems. As a result, this paper presents a new method for calculating assisted heat transfer and shaft work targets for an example TS problem. Analysis results show that assisted heat transfer increases TSHI only when a process heat recovery pocket spans the TS Pinch Region. The maximum assisted TSHI can be targeted by comparing each heat recovery pocket to the Site Utility Grand Composite Curve (SUGCC) using background/foreground analysis. Where heat recovery pockets span two steam pressure levels away from the TS Pinch Region (usually above), the example shows the potential for assisted shaft work production. In this case, the source segment of the heat recovery pocket generates steam (e.g. MPS), which replaces steam that would otherwise have been extracted from a steam turbine. The sink segment of the heat recovery pocket consumes lower pressure steam (e.g. LPS), which is extracted from the turbine. If a heat recovery pocket falls outside these two situations (assuming direct inter-process integration is disallowed), the entire pocket should be recovered internal to a process

Surveillance of Broad-Spectrum Antibiotic Prescription in Singaporean Hospitals: A 5-Year Longitudinal Study

10.1371/journal.pone.0028751PLoS ONE612

Water-Energy Nexus Cascade Analysis (WENCA) for simultaneous water-energy system optimisation

This paper presents a new numerical method called the Water-Energy Nexus Cascade Analysis (WENCA), developed based on the principal of Pinch Analysis. Water and energy are both valuable resources that are majorly used in industrial processes. Both water and energy are interdependent where increasing water demand will increase the energy demand and vice versa. In this paper, WENCA is introduced to simultaneously optimise both water and energy system that is interdependent. The methodology applies Cascade Analysis to individually optimise both system. As both systems are interdependent, altering one of the system will result in a change to the other system. An iterative method is then introduced to converge the analysis to obtain the optimal result for both systems. A case study comprising of both electricity and water demand of 6,875 kWh and 3,000 m3 from a residential area with 1,000 unit of houses is applied in this work. The electricity demand is met using fuel cell where hydrogen is produced through coal gasification (which utilised water as it raw material), a water treatment plant (WTP) is also introduced for water treatment to fulfil the water demands. The optimal result reveals that the WTP capacity is 3,200.73 m3, its corresponding water storage tank capacity is 175 m3, hydrogen power plant is 9 MW and its corresponding energy storage capacity is 4.13 MW

Examining the generalizability of research findings from archival data

This initiative examined systematically the extent to which a large set of archival research findings generalizes across contexts. We repeated the key analyses for 29 original strategic management effects in the same context (direct reproduction) as well as in 52 novel time periods and geographies; 45% of the reproductions returned results matching the original reports together with 55% of tests in different spans of years and 40% of tests in novel geographies. Some original findings were associated with multiple new tests. Reproducibility was the best predictor of generalizability—for the findings that proved directly reproducible, 84% emerged in other available time periods and 57% emerged in other geographies. Overall, only limited empirical evidence emerged for context sensitivity. In a forecasting survey, independent scientists were able to anticipate which effects would find support in tests in new samples

A numerical analysis for total site sensitivity

Total Site Heat Integration (TSHI) is an established method for analysis and mapping of heat sources and sinks of multiple processes linked via a centralised utility system. The TSHI method is very beneficial for analysing a total site's sensitivity to plant maintenance shutdown and production changes that affect integrated heat sources and sinks. This paper presents the Total Site Sensitivity Table (TSST) as a systematic approach for exploring the effects of plant shutdown or production changes. TSST can be used hand in hand with TSHI graphical approaches (Grand Composite Curve, Total Site Profile and Site Composite Curve) or numerical approach (Total Site Problem Table Algorithm). The graphical approach provides better insights while the numerical approach provides faster, easier and accurate calculations. Both approaches have its advantages and disadvantages and it is up to the engineers which approach they prefer or complement. The use of TSST allows a design engineer to clearly see the sensitivity of Total Site (TS) towards operational changes. The best setting for different operation condition in total site context can be selected by exploiting this tool. The worst case scenario can also be explored for the integrated TS system through the use of TSST. This information is useful for exploring the individual plant operational flexibility. Decision for having a backup heat exchanger network according to TSST would increase the energy saving for various TS operating conditions. TSST can be used to consider various 'what if' scenarios. They allow the determination of the optimum size of utility generation system and backup piping needed to be designed, external utilities that need to be bought and stored. Application of this technique on a case study demonstrates with the assistance of TS-PTA, TSST clearly pinpoint the effects of plant shutdown or production changes on heat distribution and utility generation systems of a Total Site

A numerical tool for integrating renewable energy into total sites with variable supply and demand

Total Site Heat Integration (TSHI) of multiple plants on a total site has recently been extended to include variable supply and demand of renewable energy. A graphics- based targeting procedure based on Time Slices (TSLs) was proposed recently to handle this variability. It has been based on the construction of Composite Curves (CCs), Grand Composite Curve (GCC) and the Total Site Profiles for each time interval. However, a dedicated numerical algorithm can offer more useful features. This paper introduces a numerical algorithm to efficiently address large-scale TSHI problems involving variable supply and demand. The tool is an extension of the Total Site Problem Table Algorithm (TS-PTA) published recently. Due to its numerical nature, it locates the stream origins conceptually and precisely and it can be embedded into larger algorithms. TS-PTA allows rapid and precise determination of the Total Site targets utilities and heat storage, while still preserving the ability to show the curves used by the graphical methodology (e.g. GCC and Site CC, which are better for visualisation). Heat storage facilities are used in solving variable supply and demand problem. Total Site Heat Storage Cascade (TS-HSC) is introduced in this work for analysing heat excess in certain TSL that can be cascaded to the next TSL during start-up and operation. This novel tool also could be used for estimating the heat storage capacity required. The procedure is illustrated on a previously published case study, confirming the advantages of TS-PTA to the graphics-based targeting methodology

The relationships between academic motivation and academic performance of first-year chemical engineering students

Academic motivation is linked to benefits in terms of learning effectiveness. This study investigated motivation of pursuing an engineering degree among first year chemical process engineering students. Forty-six students (n=46) who were in their first week of study completed a self-administered online questionnaire, that is the Academic Motivation Scale (AMS). The results showed that students had higher intrinsic motivation, higher extrinsic motivation and lower amotivation upon enrolling into the degree. Next, students' academic performance in the first semester was collected. Correlations between motivation and academic performance were studied. The results indicate that extrinsic motivation is correlated significantly with academic performance. Recommendations were made to improve teaching and learning effectiveness, using the Self-Determination Theory perspective

Investigating the reliability and usefulness of self- and peer assessments of a capstone design project

There is increasing use of self- and peer assessments to assess behaviours of students working on group projects. This study aimed to explore the reliability and usefulness of self- and peer assessments during a capstone design project. A sample of 61 final-year undergraduate students aged 23 to 25 years old who were enrolled in Bachelor Degree of Chemical Process Engineering participated in the study. Students worked in groups of 5 to 6 members for 28 weeks to complete the project. Training was provided, and progress was monitored. Self- and peer assessments were conducted during the 6th, 14th and 22nd weeks. In each assessment, students rated their own behaviours and those of their peers using identical Likert scale questionnaires, and they also wrote feedback to themselves and their peers. Quantitative findings reported that, in the 6th week, students ranked themselves (mean = 3.98) significantly lower than how they ranked their peers (mean = 4.16). In the 14th week, students still ranked themselves (mean = 4.14) lower than how they ranked their peers (mean = 4.20). Last, in the 22nd week, students ranked themselves (mean = 4.24) equivalent to how they ranked their peers (mean = 4.24). For qualitative findings, feedback written to peers in the 22nd weeks was compared to self-assessment feedback from that week. Self- and peer observations on one’s strengths and areas for improvement seem to converge both quantitatively and qualitatively towards the end of the project. It is also noted that both self- and peer assessment scores increased between the first and third assessments. The findings imply that students’ behaviours improved while working on the capstone project. In conclusion, self- and peer assessments could be reliable and useful for chemical engineering students, and training students in how to conduct these assessments is essential to ensure successful implementation. Future qualitative research could identify how and why students gradually change their behaviours in long-term, team-based projects