What energy-saving measures and equipment do steel mills have?

Improvement and suggestion on water saving and environmental protection of equipment in Angang No.2 Steelmaking Plant

Angang equipment maintenance cooperation center steelmaking work area north task work area

In view of the large industrial water consumption and the internal process characteristics of the system, it is feasible to save energy and protect the environment by recycling again, adding cooling facilities and filtering again. The actual production shows that the water consumption after transformation is 40% lower than that before transformation, which is beneficial to realize the energy saving and emission reduction of industrial water in Anyang Iron and Steel Group.

Key words: sealing performance of new drug pump with cooling tower shaft seal device in zero emission system

0. preface

Under the guidance of Scientific Outlook on Development of Angang, Angang has been advancing towards the goal of building a harmonious society and building a resource-saving and environment-friendly enterprise, so as to achieve the maximum economic and social benefits with as little resource consumption and cost as possible, that is, "less input, more output" and realize the harmonious unity of economic, social and environmental benefits. Scientific and technical personnel and on-site operators collect on-site technical data, create new water-saving technologies and measures, save water resources and reduce industrial wastewater discharge.

Trial operation of zero emission system

Two sets of filtration systems were used in the water treatment pump station of No.2 Steelmaking Plant 1 and No.2 Continuous Caster 1997, respectively. This single process not only consumes a lot of industrial water, but also pollutes the environment with overflow water. In 2007, a new pumping station named "Zero Discharge Pumping Station" was built in the Second Steelmaking Plant in order to realize zero discharge of sewage, little or no new water input and reduce environmental pollution. The pump station introduced two domestic advanced vacuum pumps and a filter, and the indirect system and direct system of the first water treatment pump station and the second water treatment pump station were reformed. After mixed collection, the overflow water from these two systems is sent to the zero discharge system, filtered again and reused, and then enters the production circulating water system, realizing the full recovery and reuse of industrial wastewater. According to the daily record data, the indirect water tank of a water treatment pumping station is replenished 18 to 24 times a day, and the water consumption is about 1000 to 1200 cubic meters, accounting for half of the water consumption of the whole system. After the zero emission system runs, the indirect water tank does not need to replenish water every day, which greatly reduces the cost. In the zero-emission system, scientists and technicians adopted a closed-loop system and an automatic backflow valve device, and the opening and closing of the backflow valve was completely controlled by the water level, thus reducing the labor intensity of workers. This kind of "small area circulation" which integrates five systems, that is, a method of circulating water in one area, makes full use of water resources, realizes multi-purpose of one water and obviously reduces water consumption. The total daily water consumption used to be 4000 cubic meters per hour, but now it is 2400 cubic meters per hour. However, this system cannot run continuously, and only intermittent operation can ensure the quality of cooling water. The detailed process flow chart is shown in figure 1.

More cooling towers

According to the statistics of the Iron and Steel Federation, the degree of water consumption in the production process is ironmaking, steelmaking, steel rolling coking and sintering in turn. The most water-consuming link in steelmaking plant is billet cooling water. Cooling is the biggest water consumption link in billet cooling water treatment. With the aggravation of greenhouse effect and the continuous improvement of output, the original cooling equipment for continuous casting operation in the Second Steelmaking Plant has gradually failed to meet various production indicators, especially the temperature of cooling water for crystallizer. In summer, workers mainly rely on monitoring the temperature of cooling water to manually open and close valves and replenish water to two water tanks to cool down, which not only increases the workload of workers, but also wastes related costs such as medicines, fresh water and spare parts. Through the daily monitoring and recording of cooling water index, a new cooling tower is set on one side of the original four cooling towers, and the control mode of the new cooling tower is the same as that of the old cooling tower.

The newly-built cooling tower can effectively control the water temperature of indirect cooling water within the production index. If no new cooling tower is built, the only way to replenish water and cool down is to waste not only new water, but also drugs. More seriously, when water is replenished to a certain extent, the water tank will overflow, and industrial water containing a lot of drugs will seriously pollute groundwater and the environment. First of all, from the perspective of long-term sustainable development, building a cooling tower is an investment and a long-term benefit; Secondly, Anshan is a city with a serious shortage of water resources and an industrial city with a population of one million. The water consumption of Angang accounts for more than two-thirds of the city's total water consumption, and a large amount of industrial water discharged is a threat to precious and limited groundwater resources. 80% of diseases and 50% of children's diseases in the world are related to drinking water pollution. For the sake of our living environment, the development of industry would rather sacrifice money than the source of life for future generations-water.

3. Improve the sealing performance of the shaft seal device of the pump mainly used in production.

Water treatment pumping stations are mostly horizontal centrifugal pumps, and their shaft seals are sealed with packing. Before 2007, the water leakage of all-soft packing seal was large and the maintenance could not be controlled. In 2007, the combination of soft packing and new sealing packing greatly improved the sealing performance of shaft seal device. Because the new sealing packing (muddy mixed packing) has no leakage, only the soft packing has leakage, and the dripping water of the shaft seal has been controlled within the standard range of 20-30 drops. The sealing structure of muddy mixed packing is shown in Figure 2. Both ends of the packing cavity are filled with soft packing rings for fixing the intermediate packing, and a muddy mixed packing (CMS2000) is filled between the two soft packing rings. Muddy mixed packing is a new type of sealing packing, which is composed of synthetic fiber, high purity graphite or polymer silicone grease, PTFE and organic sealant, forming a mud-like substance without specification restrictions. The packing rotates synchronously with the shaft, which reduces the water leakage between the shaft and the packing, and the sealing is reliable: after the improvement, the packing does not need to be cleaned and cooled, and the industrial water consumption is also reduced. As shown in figure 2.

4. Replace the medicine pump with a new one.

From 1980s to 2005, vertical medicine pump has been the main equipment of water treatment pumping station. 24 hours a day, the medicine is added to the medicine jar by hand at intervals, and then the medicine is transferred to the corresponding water tank or sink by hand at intervals. The disadvantages of this medicine pump are uneven dosing and unstable concentration of traditional Chinese medicine in water. After running for a period of time, the pipeline is easy to be blocked and the maintenance rate is high. Once the medicine pump fails, it is necessary to manually add medicine to the water tank or sink regularly, so that the amount of medicine in the cooling water is uneven. Sometimes when the water in the sink or pitcher runs out, the dose of medicine even reaches zero. In order to restore the concentration of chemicals, it is sometimes necessary to manually clean and overflow the water tank, which wastes a lot of industrial water. Since 2006, all drug pumps have been equipped with plug-type drug pumps with corrosion-resistant plastic casings. This kind of drug pump has very low maintenance failure rate, good sealing performance and uniform and lasting drug injection.

In actual production, the above four aspects are only part of the water-saving and environmental protection transformation of equipment. After my personal investigation, except for the zero emission system, other aspects fully meet the production requirements. So I have come to the conclusion that the zero-emission system needs to be improved. Now I would like to make three suggestions:

A double-layer filter screen can be installed on the pipeline in front of the filter, or a filter of the same model can be installed. After laboratory tests, the turbidity of water after zero discharge filtration is high, mainly suspended solids, indicating that the existing filter can not meet the filtration requirements, and another filter needs to be added for re-filtration.

A dosing system should be introduced into the zero emission system to ensure water quality. The water in the zero-emission system mainly comes from the overflow water from the indirect pond and the direct pond, and impurities will inevitably enter during the collection process, so it is necessary to improve the water quality by adding chemicals.

Increase the backwashing times of the filter. At present, the site can only be backwashed three times for various reasons, so it is necessary to increase the backwashing times to make the filtered water clearer.

References:

(1) Seal Design Manual, edited by Fu Ping and Chang Degong, Beijing, Chemical Industry Press, April 2009.

(2) Pump Maintenance Manual, edited by Tao, Chemical Industry Press, July 2009.

(3) Practical Manual of Water Treatment Equipment, edited by Song Xiangling, Sinopec Press, July 2008.