On December 6, the China Iron and Steel Association(CISA) organized an evaluation meeting on scientific and technological achievements through on-site video. The scientific and technological achievements of "Development and Application of Direct Waste Heat Recovery Technology for High Temperature Solid Bulk Materials" completed by Beijing Jianlong Heavy Industry Group Co., Ltd., Panshi Jianlong Iron and Steel Co., Ltd., Sichuan Chuanguo Boiler Company Limited, Tsinghua University and China Special Equipment Inspection and Research Institute are evaluated.

After comprehensive evaluation by the experts of the evaluation committee, it is agreed that the overall technology of the project has reached the international advanced level, and the solid-solid heat exchange technology has reached the international leading level!

Development and Application of Direct Waste Heat Recovery Technology for High Temperature Solid Bulk Materials

Project Background

According to statistics, China's metallurgy, building materials and other industries produce more than 4.5 billion tons of high-temperature solid bulk materials every year, and the waste heat exceeds 100 million tons of standard coal. At present, the waste heat of a large number of calcined raw materials and industrial slag in the process industry accounts for more than 60%. In 2020, the pellet output of the metallurgical industry alone will reach 200 million tons, the sinter output will reach 1 billion tons, and the recoverable waste heat will be close to 22 million tons of standard coal. It is of great significance to realize the efficient recovery and utilization of these huge waste heat resources for metallurgical and other industries to achieve the goal of carbon peaking and carbon neutrality.

At present, gas-solid secondary heat exchange technology is mainly used in waste heat recovery of high-temperature solid bulk materials at home and abroad, that is, after introducing intermediate gas medium for heat exchange, it exchanges heat with water to produce steam. In this technology, the irreversible energy loss of gas secondary heat exchange is large, the efficiency of waste heat recovery is low, and the self-consumption of electricity is high because of the combination of two systems.

For this reason, Jianlong Group, in conjunction with relevant research institutes, has independently innovated and developed high-temperature solid bulk waste heat direct recovery technology and equipment, which has been successfully applied to the waste heat recovery of pulverized coal pyrolysis semi-coke and shaft furnace pellets.

Project Highlights

The mechanism of solid direct heat transfer based on the coupling of contact heat conduction, gas film convection heat transfer and radiation heat transfer was revealed, the efficient heat transfer method between high temperature solid bulk and pipe wall was put forward, the heating surface structure of recovery device suitable for direct waste heat recovery of solid bulk was developed, and the integration of high temperature solid bulk cooling and waste heat recovery was developed. The recovery rate of waste heat reaches more than 80%.

Under the gravity condition, the downward flow of high temperature solid bulk material in the dense tube bundle of the heating surface and the wear mechanism of the tube wall were revealed, and the method to prevent the blockage of high temperature solid bulk material particles in the tube bundle of the heating surface and the wear prevention of the tube wall was found, which realized that the measured wear loss of pellet material on the heating surface tube was less than 0. 035 mm/year, and met the need of long life application of the heat exchange device.

A boiler suitable for direct recovery of waste heat from high-temperature solid bulk materials has been developed, as well as matching devices such as long-distance and large-inclination thermal insulation transfer, thermal screening and thermal crushing, forming a direct recovery technology of waste heat from high-temperature solid bulk materials, integrating and developing a complete set of equipment, and the power consumption rate of the system is less than 10%.

The project has applied for 21 patents, including 1 authorized invention patent, 11 authorized utility model patents, 9 accepted invention patents, 1 responsible for formulating group standards and 6 published papers. At present, it has been successfully applied to Hebei Longcheng pulverized coal pyrolysis semi-coke production line and Panshi Jianlong pellet waste heat recovery, and the energy consumption per ton pellet process is better than the advanced value level.

Based on the current demand for semi-coke from pulverized coal pyrolysis in China and the output of shaft furnace pellets and sintering, the direct recovery technology of waste heat from high-temperature solid bulk materials can save 3.3 million tons of standard coal and reduce carbon dioxide emissions by 8.227 million tons annually, resulting in benefits of about 3.96 billion yuan, with significant economic, social and environmental benefits and broad prospects for promotion.

In the next step, Jianlong Group plans to extend the technology to the waste heat recovery of high-temperature materials such as sinter, power plant boiler slag and various industrial roasting mineral materials, as well as the energy storage and heat exchange of high-temperature solid materials, so as to further promote the efficient utilization of green energy and contribute to the green and low-carbon development of the industry!

12月6日，中国钢铁工业协会通过现场结合视频的方式组织召开科技成果评价会，对北京建龙重工集团有限公司、磐石建龙钢铁有限公司、四川川锅锅炉有限责任公司、清华大学、中国特种设备检测研究院等单位完成的《高温固体散料余热直接回收技术开发及应用》科技成果进行评价。

经评价委员会专家综合评定，一致认为该项目整体技术达到了国际先进水平，其中固固换热技术达到了国际领先水平！

高温固体散料余热直接回收技术开发及应用

项目背景

据统计，我国冶金、建材等行业每年产生45亿吨以上的高温固体散料，余热量超过1亿吨标准煤，目前流程工业中大量煅烧原料、工业炉渣等余热占比达到60%以上。2020年，冶金行业仅球团产量就达2亿吨、烧结矿产量达10亿吨，可回收利用的余热接近2200万吨标准煤。实现对这些数量巨大的余热资源的高效回收利用，对冶金等行业实现碳达峰、碳中和目标意义重大。

目前，国内外高温固体散料余热回收主要采用气固二次换热技术，即引入中间气体介质进行换热后，再与水换热产生蒸汽。该项技术气体二次换热的不可逆能量损耗大，余热回收效率低，且由两套系统组合，自耗电量高。

为此，建龙集团联合相关科研院所针对固体散料余热直接回收技术问题进行攻关，自主创新研发了高温固体散料余热直接回收技术及装备，并成功应用于粉煤热解兰炭和竖炉球团余热回收。

项目亮点

揭示了基于接触导热、气膜对流传热和辐射换热耦合的固体直接换热的机理，提出了实现高温固体散料与管壁的高效换热方法，开发了适用于固体散料余热直接回收的回收装置受热面结构，研制了高温固体散料冷却与余热回收一体化耦合技术装置，余热回收率达到80%以上。

揭示了重力条件下，高温固体散料在受热面密集管束间的下行流动，及对管壁的磨损机理，找到了防止高温固体散料颗粒在受热面管束内阻塞及管壁防磨的方法，实现了球团物料对受热面管实测磨损量＜0.035mm/年，满足换热装置的工程长寿命应用需要。 

开发了适用于高温固体散料余热直接回收的锅炉，以及与之匹配的长距离大倾角保温转运、热筛分、热破碎等装置，形成了高温固体散料余热直接回收技术，集成开发了成套装备，系统自耗电率小于10%。

该项目共申请专利21项，其中授权发明专利1项，授权实用新型专利11 项，受理发明专利9项；负责制定团体标准1项，发表论文6篇。目前已成功应用于河北龙成粉煤热解兰炭生产线和磐石建龙球团余热回收，吨球团矿工序能耗优于先进值水平。

以目前国内粉煤热解兰炭需求量、竖炉球团产量和烧结产量计算，利用高温固体散料余热直接回收技术，每年可以节约标准煤330万吨、减排二氧化碳822.7万吨，产生效益约39.6亿元，经济、社会、环境效益显著，推广前景广阔。