China is a country with relatively scarce water resources. The random discharge of wastewater from concrete mixing plants will cause a lot of waste of water resources. At the same time, it will cause serious pollution to soil and groundwater resources and cause damage to the natural environment.
The recycling of wastewater from the concrete mixing plant not only has good economic benefits for the enterprise, but also has good social benefits.
Alkaline sewage treatment methods and products of mixing plants
The alkaline sewage of the mixing plant is neutralized with carbon dioxide. During the treatment process, the free hydroxide ions (OH-) in the sewage react with carbon dioxide to generate neutral water.
The treated reclaimed water can be used for concrete mixing water, car washing water, watering flowers, fish farming or direct discharge.
After the reaction of Ca2+, Mg2+ and carbon dioxide, calcium carbonate (CaCO3) and magnesium carbonate (MgCO3) which are insoluble in water are formed. CaCO3 and MgCO3 are stable in nature and will not pollute the environment, and can be recycled as fine chemicals. Filling, turning waste into treasure
The carbon dioxide reacts with calcium hydroxide and magnesium hydroxide in the sewage of the mixing station to generate CaCO3 and MgCO3 insolubles. Effectively reduce the content of free calcium oxide and magnesium oxide, thereby improving the quality of cement
The alkaline sewage of the mixing plant after carbon dioxide treatment meets the "GB 8978-1996 Comprehensive Wastewater Discharge Standard" and "JGJ63-2006 Concrete Water Standard"
Using carbon dioxide to comprehensively treat the alkaline wastewater of the mixing plant can save costs and increase profits for the enterprise
The price of carbon dioxide is 1.2-1.5 yuan/kg, and the comprehensive carbon dioxide consumption of the reclaimed water system is 1.12kg/m3. The cost of carbon dioxide consumed by the reclaimed water system is 1.34-1.68 yuan/m3, the equipment power consumption is about 0.3 yuan/m3, and the overall cost is 1.64-1.96 yuan/m3. The price of industrial water is 4.5-7 yuan/m3, and the median value is 5.5 yuan/m3. Treatment of sewage per cubic meter can save costs 3.54-3.86 yuan/m3.
The production of each cubic meter of concrete requires about 0.18 cubic meters of mixing water, which produces about 0.05 cubic meters of sewage. The intuitive benefit analysis assumes that the average daily production capacity of the mixing plant is 3000 m3 of concrete, which can produce 150 m3/d of sewage. Then, the cost of saving water per day after reclaimed water treatment is 531-579 yuan/d, and the cost of saving water every year is 159-173,000 yuan/y (calculated by 300d). And the higher the concrete production capacity, the more water saving costs.
When the water for washing the site and rainwater are collected into the sewage tank, the alkaline concentration of the sewage is reduced, the actual consumption of carbon dioxide is reduced, and the material cost of reclaimed water treatment is reduced. When the sewage achieves a large amount of continuous neutralization treatment, the utilization rate of carbon dioxide can be improved, so that the amount of carbon dioxide is reduced and the cost is reduced.
Increases revenue while saving energy and reducing emissions, reducing sewage damage to the natural environment
Carbon dioxide is one of the main gases that cause the greenhouse effect. Through the process of using carbon dioxide to neutralize alkaline sewage, carbon dioxide can be converted in the form of carbonate, and it can be recycled and reused to truly achieve "emission reduction". Play a role in promoting sustainable development. The carbon dioxide we use comes from the concentration and recovery of waste gas from chemical companies, which has a positive impact on the recycling of carbon dioxide.
As people pay more and more attention to environmental protection, safety and economic considerations, the use of carbon dioxide for alkaline wastewater neutralization treatment in mixing plants has attracted more and more attention. It can not only avoid the disadvantages of mineral acid neutralization, but also achieve Fully automated operation. This process has the advantages of safety, environmental protection, high efficiency, energy saving, economy and simple operation, and it will definitely become the trend of industry development