【Haichuan’s Best Practices】Renovation of waste heat boiler systems to recover exhaust steam – saves energy and reduces corrosion
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Recently, the Yan’an Refinery of Yanchang Petroleum Refining & Chemical Company, in collaboration with Workshop 2, successfully completed the renovation of the waste steam recovery system for the catalytic cracking waste heat boiler, with a capacity of 2 million tons per year. This improvement enabled more efficient recycling of steam resources, contributing to the refinery’s efforts in energy conservation, emission reduction, and cost control. Until now, the slurry drum, the external heat extraction drum, and the wastewater from the two boilers have all been discharged into the regular drainage expansion vessel. The large amount of steam released through the venting ports not only leads to waste of thermal energy and resources, but over time it can also cause corrosion to the equipment and process pipelines in the surrounding areas. The loud noise generated during venting, along with ice formation on the ground in cold weather, may also pose a risk to the health and safety of workers. To change this situation, Workshop 2 organized technical experts to conduct on-site inspections of the equipment. Through repeated discussions and thorough data analysis, the optimal steam recovery pathway and equipment layout were determined – specifically, three-stage coolers and atomizing nozzles were installed in front of the steam exhaust ports to fully recover this heat. The upgraded system directs the steam that would otherwise be released into the atmosphere to specific recovery devices, where it is processed to be converted into usable thermal energy, thereby achieving dual recovery of thermal energy and water resources. During the implementation of this plan, the workshop also made active use of old pipelines to design its own water coolers, and utilized nozzles from decommissioned desulfurization towers to create atomizing nozzles; this not only reduced the costs associated with the renovation but also helped to increase revenue while cutting expenses. This renovation represents another major breakthrough, following the successful implementation of zero wastewater discharge upgrades in the boiler area by Workshop 2. Next, Yanlian will continue to uphold the concept of green development, explore further opportunities for energy savings and consumption reduction, and keep advancing technological upgrades.
【HaiChuan – Insights from Other Sources】Rewiring waste heat boiler systems to recover exhaust steam saves energy and reduces corrosion https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=5675002 (Source: HaiChuan Chemicals Forum [HaiChuan Network])
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There is a large amount of heat in the boiler wastewater, and discharging it directly leads to waste of energy and resources. Recently, at the evaluation meeting on \"Waste heat recovery from high-temperature wastewater in boilers and near-zero emission technologies\" held at the **Energy Conservation Center**, the technology for waste heat recovery from high-temperature wastewater in boilers and near-zero emission technologies, independently developed by Hangzhou Wandes Environmental Protection Technology Co., Ltd., received unanimous approval from the experts in the evaluation panel. Using this technology for energy-saving upgrades of boilers not only helps to effectively conserve energy resources and reduce carbon emissions, but also minimizes the impact of boiler wastewater on the ecological environment. It achieves significant results in terms of energy savings, pollution reduction, and carbon cutdown, and can be widely applied in industries such as power generation, as well as petroleum, chemicals, metallurgy, papermaking, and textiles. At present, there are approximately 320,000 boilers in China, which consume around 2 billion tons of standard coal per year. The carbon emissions generated by these boilers account for about 40% of the country’s total carbon emissions, making them the energy-consuming devices with the highest energy consumption and carbon emissions in China. “In recent years, our country has made significant efforts to optimize the coal-fired power generation structure and promote its transformation and upgrading. It has actively sought to improve coal-fired industrial boilers as well as energy-saving and environmental protection measures, resulting in notable advancements in boiler manufacturing technologies and the level of energy-efficient and environmentally friendly operation. ”**Yan Yongzhe, deputy director of the Energy Conservation Center, said that overall, there is still significant room for improvement in terms of the system energy efficiency, carbon emissions, and pollutant emissions of some boilers; thus, the potential for saving energy, reducing carbon emissions, and cutting pollutants remains substantial. Especially in terms of waste heat utilization, the traditional approach for utilizing waste heat from boilers focuses primarily on the waste heat contained in flue gas and condensate water, with less attention paid to recovering the waste heat from the high-temperature wastewater discharged from the boilers. In fact, these wastewater streams also contain a large amount of heat; the discharge rate for large boilers is generally 1%–3%, while that for small boilers is 5%–8%. Since this wastewater is not recycled, it results in significant waste of heat and water resources. To address this challenge, the \"waste heat recovery from medium- and high-temperature wastewater in boilers and near-zero emission technology\" independently developed by Hangzhou Wandes Environmental Protection Technology Co., Ltd. has shown remarkable effectiveness. Yu Hong, the company’s technical advisor and senior engineer, explained that the \"waste heat recovery from high-temperature wastewater in boilers and near-zero emission technology\" not only enables the recycling of energy and resources derived from wastewater, thereby improving the efficiency of energy use and reducing operating costs, but it also helps to reduce the demand for steam generation at the source, thus cutting coal consumption. Furthermore, this technology can also reduce the need for make-up demineralized water and lower water consumption, thereby reducing the energy consumption associated with boiler operation and cutting carbon emissions. Jiao Jian, a director of the China Energy Research Society and head of the Committee on Energy Efficiency and Investment Assessment, explained that this technology, through innovations in four areas – process, materials, equipment, and control systems – converts boiler wastewater into high-quality steam. The recovery rate of water resources exceeds 99%, while the recovery rate of waste heat is over 95%. This enables efficient recovery of the waste heat from boiler wastewater, resulting in nearly zero emissions of such wastewater. Will the project, after its renovation, truly bring benefits to the company? Is the steam up to standard? Liu Zhongjian, General Manager of Jiangxi Yongguan Technology Development Co., Ltd., gave an answer as a representative of the users at the meeting: \"The project was officially put into operation in November 2022, and it has been operating safely and reliably for 14 months to date. A total of 46,000 tons of steam have been produced, generating revenues of 15.17108 million yuan. The quality of the steam produced is now better than that produced by the original boilers.\" ” “Before the operation of this project, the wastewater generated by Jiangxi Yongguan Boilers was discharged directly into the sewage treatment equipment, resulting in significant energy waste. ”Liu Zhongjian explained that to address this issue, the company signed an agreement with Hangzhou Wandes Environmental Protection Technology Co., Ltd. in December 2021 for an energy-saving renovation project aimed at improving the exhaust gas disposal systems of its 3 boilers with a capacity of 65 tons each. This project utilizes \"high- and medium-temperature wastewater waste heat recovery and near-zero emission technology\" to carry out technical upgrades to these systems. After the renovation of the project, a simple calculation of its overall benefits based on an annual operating time of 8,000 hours shows that the water resource recovery rate is 99.99%; 56,000 tons of wastewater can be converted into high-quality steam each year, resulting in annual water savings equivalent to 248,000 tons of fresh water. At the same time, it can reduce carbon dioxide emissions by 3,836 tons per year, sulfur dioxide emissions by 13 tons per year, nitrogen oxide emissions by 12 tons per year, and soot emissions by 24 tons per year. While maintaining the same steam supply, the project reduced energy consumption, resulting in an increase in average operational thermal efficiency of about 0.7 percentage points. The project generates an indirect energy-saving capacity of 6,287 tons of standard coal per year.