The paper presents a Process Integration application for waste heat utilisation from exhaust gas streams with partial condensation. It is based on the hot composite curve construction representing the gaseous mixture cooling with accounting for the condensable vapour part's gas–liquid equilibrium. With cold composite curve for streams requiring heating, the Pinch Point is determined. On this basis, the heat exchanger network (HEN) structure for utilised heat integration into the factory's energy system is developed. It accounts for the possible splitting of two-phase flow on gas and liquid streams and plate heat exchanger (PHE) type selection for specific positions in HEN. The method is illustrated by a case study of heat utilisation from exhaust gases after superheated steam tobacco drying and flue gases from natural gas-fired boiler. Heat transfer areas of PHEs in HEN are optimised with the total annualised cost as an objective function. The received solution's payback period is less than four months, with a substantial saving of energy, up to 10.9 TJ/y. It also leads to the reduction of CO₂ emissions up to 600 t/y. About 3830 t/y of steam is not discharged to the atmosphere and as the water returned to the production process.

Graphic abstract

To manuscript “Integration of Low-Grade Heat from Exhaust Gases into Energy System of the Enterprise”

中文翻译：

---

将废气中的低级热量整合到企业的能源系统中

本文提出了一种过程集成应用程序，用于部分冷凝的废气流中的余热利用。它基于热复合曲线构造，代表混合气体的冷却，并考虑了可冷凝蒸气部分的气液平衡。利用需要加热的物流的冷复合曲线，确定收缩点。在此基础上，开发了用于将热量整合到工厂能源系统中的热交换器网络（HEN）结构。它考虑了可能在气流和液体流上分流的两相流，以及针对HEN中特定位置的板式换热器（PHE）类型选择。通过对过热蒸汽烟草干燥后的废气和天然气锅炉的烟气进行热利用的案例研究说明了该方法。以年度总成本为目标函数，对HEN中的PHE的传热面积进行了优化。收到的解决方案的投资回收期不到4个月，大大节省了能源，每年最多可节省10.9 TJ。这也导致二氧化碳的减少₂排放量高达600吨/年。每年约有3830吨的蒸汽没有排放到大气中，而水又返回到生产过程中。

图形摘要

撰写论文“将废气中的低品位热量整合到企业的能源系统中”