Flexibility analysis and design of heat exchanger network for syngas-to-methanol process

The heat exchanger network (HEN) in a syngas-to-methanol process was designed and optimized based on pinch technology under stable operating conditions to balance the energy consumption and economic gain. In actual industrial processes, fluctuations in production inevitably affect the stable operation of HENs. A flexibility analysis of the HEN was carried out to minimize such disturbances using the downstream paths method. The results show that two-third of the downstream paths cannot meet flexibility requirements, indicating that the HEN does not have enough flexibility to accommodate the disturbances in actual production. A flexible HEN was then designed with the method of dividing and subsequent merging of streams, which led to 13.89% and 20.82% reductions in energy consumption and total cost, respectively. Owing to the sufficient area margin and additional alternative heat exchangers, the flexible HEN was able to resist interference and maintain production stability and safety, with the total cost increasing by just 4.08%.

OPTIMAL DESIGN OF HEAT EXCHANGER NETWORK IN OIL REFINERIES

The performance of the heat exchanger network (HEN) in a plant is an important aspect of energy conservation. “Pinch” technology and mathematical programming techniques offer an effective and practical method for designing the HEN for new and retrofit projects. The fluid catalytic cracking (FCC) is a dominant process in oil refineries and there has been a sustained effort to improve the efficiency and yield of the unit over the years. HEN optimal design in FCC process is an essential element in reducing the cost and improving the process as a whole. The objective of this work is to introduce a systematic procedure for designing optimal and flexible FCC-HEN that incorporates variations in feed flow rates and specs and on same time considers different schedules imposed on the process. Keywords: heat exchangers, fluid catalytic cracking, design of network, oil refinery, heat recovery systems

Heat integration applied on low thermal energy system: Building complex case study

The tertiary-building sector is one of the most important energy consumers in the Morocco, especially thermal energy. Its intensive use of energy is highly related to the building’s inefficient processes. The Moroccan strategy for energy efficiency aims mainly to save 12% of energy consumption by 2020 and 15% by 2030, which reinforce the appearance of many energy saving alternatives ranging from sensitization and construction laws to engineering applications. The present paper addresses the problem of the building complex energy efficiency in order to improve its performance thermally. The proposed approach in this work is based on the pinch technology which is a technique widely used to integrate and optimize the energy of thermal systems and which has demonstrated its successfulness for industrial process. The simulation results reveals that the potential thermal energy saving reaches 21.16%, with heat exchange network design initially proposed to clearly show the potential recovered. Based on the composite curves (CCs), the problem table algorithm (PTA) and the grand composite curve (GCC), the pinch point temperature is turned out to be 15°C with 316,99 kW of hot utility. The obtained results reveal that the proposed pinch technology perform its effectiveness not only in the industrial sector but also in the building-tertiary.

Pinch Technology Approach to Freshwater and Wastewater Minimisation in Brewing Operations

The rise in the cost of production of beer due to increasing demand for freshwater and high cost of treating wastewater, motivate research interests in resource management in beer production. This study determines and reduces the concentration of the contaminants in the wastewater samples collected from a brewery in Nigeria, to reduce freshwater demand and to save the cost of operation through wastewater reuse using pinch technology. The wastewater samples were analysed for the concentration of Chemical Oxygen Demand using standard procedures. The Total Dissolved Solids were measured using pH-EC-TDS metre. Water Cascade Analysis was used to evaluate the minimum freshwater demand and wastewater generated to design the maximum wastewater recovery network for minimum freshwater demand in the process. The results showed that for 41.54 t/hr of both the freshwater and wastewater used in the brewery operations, the Chemical Oxygen Demand concentration ranged between 0 – 74,775 ppm and the Total Dissolved Solids concentration ranged from 0 – 2,008 ppm. However, with the application of Water Cascade Analysis, the freshwater and wastewater flow rates reduced to 19.88 t/hr based on Chemical Oxygen Demand concentration and 21.54 t/hr based on Total Dissolved Solids concentration. The freshwater saving per annum based on the concentrations of Chemical Oxygen Demand and Total Dissolved Solids were ₦346,560,000:00 ($962,666.67) and ₦319,840,000:00 ($888,444.44), respectively. The study concluded that the application of Pinch Technology to brewery operation is viable because of its capacity to reduce freshwater demand and wastewater generation.

Cost Reduction of Fluid Catalytic Cracking Unit in Kaduna Refining and Petrochemical Company using Pinch Technology

Pinch technology is one of the most powerful methodologies of process integration that allows industries to increase their profitability through reductions in energy, water and raw materials consumption. In this study, reduction in the total annual cost of heat exchanger network (HEN) of Fluid Catalytic Cracking (FCC) unit in Kaduna Refining and Petrochemical Company (KRPC), Kaduna was determined. With the help of pinch technology, the reduction was achieved by first determining optimum minimum temperature difference by trading off energy cost and capital cost targets as a function of minimum temperature difference. Thereafter, the total annual cost obtained at the optimum minimum temperature difference was compared with total annual cost of existing design. The results of the analysis showed that the optimum minimum temperature difference was 12℃, the total annual costs of the existing design and the optimum-minimum-temperature-difference based cost were $8.7 and $7.1 Million respectively. This amounted to percentage reduction in the total annual cost of 18.4% which means that about $1.6 Million would been saved annually using the optimum minimum temperature difference to design the HEN of the FCC unit. Keywords: Pinch technology, FCC unit, Cost targeting, Area targeting, Trade-off