Application of energy management coupled with fuel switching on a hydrotreater unit

AbstractIn the last decades, saving energy and protecting environment became the most important topics for search and survey. The energy engineer for any chemical process is obliged by restrictions of “Kyoto Protocol” for limitation of carbon dioxide emissions from fuel combustion, so he does his best to reduce utility consumption and thus reduce gas emission. Proper designing of the heat exchanger network (HEN) for any process is an effective and successful method to minimize utility consumption and therefore minimize gas emission (mainly carbon gases (CO2) and sulfur gases (SOx)). Fuel switching coupled with energy targeting achieved the least gas emission. In this work we choose a hydrotreater unit of a petroleum refinery as a case study due to its effective role and its obvious consumption of utility. We applied the methodology of energy targeting through HEN design (using pinch technology) at several values of mean temperature difference (ΔTmin); where the maximum percentage of energy saving was 37% for hot and cold utility which directly leads to percentage reduction of gas emission by 29% for CO2 and 17% for SOx. Switching fuel oil to other types of fuel realized gas emission reduction percentage where the maximum reduction established was through natural gas fuel type and reached 54% for CO2 and 90% for SOx. Comparison between existing design and the optimum ΔTmin HEN led to few modifications with the least added capital cost for the hydrotreater existing design to revamp it through four scenarios; the first one depended on fuel switching to natural gas while the second one switched fuel to diesel oil, in the third scenario we applied heat integration only and the fourth one used both of heat integration and fuel switching in a parallel way

Economic evaluation and sensitivity analysis of some fuel oil upgrading processes

Seven upgrading schemes, identified as high distillate production schemes have been proposed for upgrading of 3.50 × 106 t/y atmospheric residues. The seven schemes were evaluated using the discounting cash flow method. Economic parameters such as internal rate of return, IRR, payback period, PBP and net present value, NPV have been calculated for each option. All studied schemes proved profitable with IRR ranging between 25.2 and 33.7% with option 7 having the highest NPV, IRR and payback period. Sensitivity analyses were performed on this option. The parameters investigated are: sales price (Revenue); production rate (feed weight); feed cost; utilities cost; direct and indirect costs; tax% and discount rate%. Their impact on NPV and %IRR has been evaluated. Tornado diagrams were constructed to illustrate the effect of variation of different cost parameters on NPV and IRR. The single most effective input variable is Revenue on both NPV and IRR. With two-factor sensitivity analysis, the two most important input variables for NPV and IRR are revenue and utilities. Spider charts for option 7 have been created to show how the model’s outputs depend on the percentage changes for each of the model’s input variables

Design of optimum flexible heat exchanger networks for multiperiod process

Due to the rising of energy prices, energy saving became very important. Optimum design of Heat Exchanger Networks (HEN) is a successful way to minimize energy consumption. The present work discusses the design of optimal flexible heat exchanger networks that adapt with changes in streams’ start and target temperatures and heat capacity flowrates. For a process consisting of n periods, multiperiod LP and MILP models were used to determine the target utility requirements and the heat exchanger network configuration that achieves the minimum number of units and remain flexible to ensure minimum utility requirements at each period of operation. Applying these models on a multiperiod literature problem resulted in different solutions corresponding to different iteration runs. The optimum solution that realizes the least exchangers’ cost was compared with literature results for the same problem

Commercialization potential aspects of microalgae for biofuel production: An overview

Biofuels are particularly important as an alternative fuel option for transportation. The sustainability of biofuels will depend on the development of viable, sustainable technologies that do not appear to be yet commercially viable. Successful development of algae-based biofuels and co-products industry requires the optimum combination of technical innovations in systems and processes, coupled with economic feasibility in the practical implementation and integrated scale-up for commercial production and marketing. This article discusses the importance of algae-based biofuels together with the different opinions regarding its future. Advantages and disadvantages of these types of biofuels are presented. Algal growth drives around the world with special emphasis to Egypt are outlined. The article includes a brief description of the concept of algal biorefineries. It also declares the five key strategies to help producers to reduce costs and accelerate the commercialization of algal biodiesel. The internal strengths and weaknesses, and external opportunities, and threats are manifested through the SWOT analysis for micro-algae. Strategies for enhancing algae based-fuels are outlined. New process innovations and the role of genetic engineering in meeting these strategies are briefly discussed. To improve the economics of algal biofuels the concept of employing algae for wastewater treatment is presented