Assembly site of ring cooler in NHI workshop （Reference picture）

Ring cooler, as the main equipment of pelletizing and sintering process, is a very common cooling equipment, which is widely used in the cooling of sinter and pellet. NHI has made great efforts to break through technical difficulties and continuously shorten the manufacturing cycle, so as to significantly enhance the competitiveness of products.

Technology advance promotes enterprise development

NHI owns all models of matured ring coolers, and has the capacity to design specified models of ring coolers according to Client requirements. The advantages of NHI ring cooler are：simple structure, reliable performance, easy to operate, convenient to maintenance and safe to use. It is widely used in the metallurgical industry.

The previous produced ring cooler structure owned a best sealing effect, which is conducive to energy conservation and emission reduction and waste heat recovery and utilization. The 150 square meter blast ring pellet cooler produced and manufactured by Shenyang Heavy Machinery Group （SHMG）-the predecessor of NHI,has been successfully tested in Gongchangling pelletizing plant of Anshan Steel company.This equipment makes China's pellet cooling technology into the world's advanced ranks.

Technological innovation improves the ability to tackle key problems in energy conservation and emission reduction

NHI pays attention to technological innovation. During the equipment transformation of a large steel enterprise, it is found that the old ring cooler structure is still used at the production site, which adopted the form of double-layer rubber seal structure, and dynamic and static seals are set between both sides of the trolley and the bellows. Composite rubber with heat-resistant temperature of 200℃~300℃ was adopted, with a service life of only 3 to 6 months. Frequent replacement, high cost and long time affect the production efficiency. The average air leakage rate is as high as 30% to 40%, resulting in large installed capacity of fan, serious dust pollution and low waste heat recovery efficiency. It is obviously not in line with China's current policies and the requirements of enterprises' own energy conservation, emission reduction and capacity improvement.

In order to solve this problem, NHI arranged professional designers to conduct field investigation and measurement, and formulated the transformation plan according to the actual needs and product characteristics of steel enterprises. Firstly, the trolley of the ring cooler is changed into a sector, the grate plate is an assembled structure, which is easy to replace, and the trolley assembly structure is adjusted to an upper and lower split assembly structure, which is convenient for on-site installation and disassembly. At the same time, the forms of rotary frame structure and reset roll structure are optimized to make it have better weldability, higher connection accuracy with the trolley, complete contact between the roll surface and the lower surface of the trolley, and more reasonable bearing force of the shaft. The floating mechanical seal device is selected for the lower seal, which can achieve the external maintenance of the ring cooler, and solve the difficult maintenance problems of the traditional mechanical seal of the ring cooler and the safety problems of maintenance personnel. Optimize the insulation structure of trolley breast board and cover, reduce heat loss, and ensure waste heat recovery and power generation efficiency. Based on the floating mechanical seal device, the personnel have developed a new combined seal device to effectively block the dust from entering the water tank, reduce the dredging pressure of the water seal, form a reliable liquid seal, control the air leakage rate of the whole machine between 3% and 5%, improve the on-site working environment and the waste heat recovery efficiency.

Precise arrangement to shorten the equipment transformation cycle

Equipment transformation means pressing the production pause key. How to shorten the manufacturing cycle of new products is a common topic for every equipment manufacturing enterprise.

The person in charge of planning of the production command center of NHI said:"It is mainly the pressure of the manufacturing cycle. In order to help customers minimize losses, the production plan must be well matched. However, manufacturing is a dynamic process. To minimize the variables, we need to fully grasp the actual situation of the whole production basin and go deep into the front line, otherwise the production plan can only be on paper."

As a young enterprise management team, in order to make a solid plan, the production command center of NHI led its employees to visit multiple production departments such as processing workshop, procurement department and assembly branch to understand the equipment operation, supply of production materials, assembly site and manpower. The final production cycle is 108 days, which is more than 40 days shorter than the previous manufacturing cycle. With the continuous deepening of technological transformation, NHI has ushered in a good development momentum this year. The sales revenue in the first half of the year exceeded 200 million CNY in 2020,and the sales revenue in the second quarter increased by 292.4% year-on-year, which has laid a solid foundation for Northern Heavy Industry to achieve the development goal of the whole year.