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Summary: In the textile industry, reactive dyeing requires large volumes of hot water, which increases cost and energy consumption. Although the waste heat of the exhaust gas from the stentering process can be recovered to reduce cost and energy consumption, fiber dust and oil mist inside the exhaust gas cause problems such as fouling and clogged pores. Hence, a novel waste heat and oil recovery system in the finishing treatment of the textile process is proposed for cleaner production with economic improvement. The proposed system comprises the following steps: (a) The exhaust gas is split by the electrostatic precipitator (ESP) at a certain ratio through optimization as its exhaust gas throughput is a key deciding variable for cost and profit. (b) A mathematical model of the overall cost, including profits from oil recovery and energy savings attributed to waste heat recovery, total capital investment, and total product cost attributed to the additional ESP installation, is designed to identify an optimal split ratio. (c) Fiber dust and oil mist are removed from the exhaust gas split at the optimal ratio using the ESP and then recycled as regenerated oil. Waste heat is recovered from the treated gas after the fiber dust and oil mist are recovered as regenerated oil through the heat exchange in the air to water heat exchanger; this recovered heat is supplied to the dyeing process to minimize the energy required for heating the water. (d) Finally, VOCs and the remaining pollutants are removed by activated carbon adsorption from the low‐temperature‐treated gas after the waste heat is recovered. These processes recover waste heat and oil and achieve process stability and efficiency improvements because of the removal of oil mist, fiber dust, and VOCs. As a result, the overall cost can be reduced by 10.2% based on the recovered waste heat and oil, and the fiber dusts, odor, and VOCs are removed by 95%, 89.86%, and 96.28%, respectively. [ABSTRACT FROM AUTHOR]

In this work, alternative evaporation processes for PLA production were designed with economic assessment. The suggested processes are the multiple-effect evaporation (MEE) process and thermal vapor recompression (TVR)-assisted evaporation process. First, the MEE process can efficiently reuse waste heat by additional column installation, thereby reducing the steam energy consumption. The proposed MEE process involves five columns, and after the evaporation in each column, the waste heat of the emitted vapor is reused to heat steam in the reboiler of the next column. Second, the suggested TVR-assisted evaporation process utilizes an additional steam ejector and recovers waste heat from the emitted vapor by increasing the pressure using high-pressure driving steam at the steam ejector. Each alternative process was modeled to predict the steam energy consumption, and to determine the cost-optimal process; the total annualized cost (TAC) of each alternative process was calculated as evaluation criteria. In the simulation results, the alternative processes using MEE and TVR reduced the steam consumption by 71.36% and 89.97%, respectively, compared to the conventional process. As a result of economic assessment, the cost-optimal process is the alternative process using TVR and the TAC can be decreased by approximately 90%. [ABSTRACT FROM AUTHOR]

Reactive dyeing is primarily used in the textile industry to achieve a high level of productivity for high-quality products. This method requires heating a large amount of freshwater for dyeing and cooling for the biological treatment of discharged wastewater. If the heat of the wastewater discharged from the textile industry is recovered, energy used for heating freshwater and cooling wastewater can be significantly reduced. However, the energy efficiency of this industry remains low, owing to the limited use of waste heat. Hence, this study suggested a cost-optimal heat exchanger network (HEN) in a heat pump-assisted textile industry wastewater heat recovery system with maximizing energy efficiency simultaneously. A novel two-step approach was suggested to develop the optimal HEN in heat pump-assisted textile industry wastewater heat recovery system. In the first step, the system was designed to integrate the heat exchanger and heat pump to recover waste heat effectively. In the second step, the HEN in the newly developed system was retrofitted using super-targeted pinch analysis to minimize cost and maximize energy efficiency simultaneously. As a result, the proposed wastewater heat recovery system reduced the total annualized cost by up to 43.07% as compared to the conventional textile industry lacking a wastewater heat recovery system. These findings may facilitate economic and environmental improvements in the textile industry. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO 2) is a pollutant that is mainly emitted in thermal coal-fired power plants, and it causes air pollution, which is required to be removed since it adversely affects the atmosphere environment. This study presents a novel approach to remove SO 2 using carbonate melt by designing a flue gas desulfurization (FGD) process that uses a carbonate melt desulfurization (CMD) subsystem to remove >99.9 wt% of SO 2 and a carbonate melt regeneration (CMR) subsystem that recovers ~99 wt% of the melt. To reduce the operating costs of the proposed process, a heat-exchanger network was developed to use the waste heat that existed in the process. The levelized cost of the proposed FGD process using carbonate melt was determined as US$ 761/ton SO 2 removed and is therefore cost-competitive with other SO 2 removal technologies. Sensitivity analysis indicates that coal price is the main driver of levelized cost. [ABSTRACT FROM AUTHOR]

Stenters used for drying during the dyeing process, waste considerable thermal energy through exhaust gas. This energy waste is one of the major bottlenecks to improving the sustainability of the textile dyeing field. To find the most efficient recovery of the waste heat from the stenters for supplying various energy sources and reducing energy consumption within overall textile system, this study compares three heat recovery systems: (Case- 1) air preheating, (Case-2) hot-water generation, and (Case-3) power generation. Energy, exergy, and economic analyses indicated that all cases demonstrated superior results those obtained using the base case. In terms of energy consumption, Case-1 demonstrated a 60.8 % reduction achieved through decreased fuel consumption. In particular, the economic analysis indicated that Case-1 was the most favorable option because it possesses the lowest operating costs by significantly reducing fuel consumption for air preheating. Additionally, the simple configuration of the process and the use of a small heat exchanger contribute to a lower capital cost. Thus, Case-1 could the most efficiently recover and utilize the heat wasted from the stenter at a relatively low investment cost among proposed systems. This demonstrated the potential for energy and cost savings within the textile industry. [Display omitted] • Heat recovery systems in the stenter reduce the use of electricity, steam and fuel. • Case 1 has low expense due to low coolant use, simple design and fuel reduction. • Low hot water demand in the dyeing process made case 2 less economical than case 1. • This study indicates the potential for greater energy savings in textile industry. [ABSTRACT FROM AUTHOR]