A process for removing water-soluble salts from magnesium desulfurization by-products

Abstract

The present invention discloses a process for removing water-soluble salts from magnesium-based desulfurization by-products, which is specifically described as follows: the solid by-products of magnesium-based desulfurization are transported to a crushing system by a conveying device, and the crushed particles enter a liquid-solid mixing device. The mixing device is equipped with a dosing device and a water injection device. The dosing device adds a measured amount of slaked lime to the mixing device according to the by-product solid flow rate and the soluble salt content. The water injection device adds water to provide a reaction environment and necessary fluidity. The mixed slurry is sent to a liquid-solid separation system for liquid-solid separation treatment and is divided into a filter cake and a filtrate. The filter cake is sent to a solid waste dump for landfill disposal, and the filtrate enters a waste liquid treatment system. The filtrate enters a waste liquid concentration system and a waste liquid treatment system for further treatment. The advantages of the present invention are: low energy consumption, reuse of water resources, no waste liquid, and no dust pollution after dust prevention and control measures are taken in the transportation link.

Description

Technical Field

[0001] The patent of this invention belongs to the field of general industrial solid waste treatment technology, and specifically relates to a process method for removing water-soluble salts from magnesium desulfurization by-products. It can be applied to the process method for removing water-soluble salts from magnesium desulfurization by-products, general industrial solid waste, soil remediation and other industries. Background Art

[0002] At present, flue gas desulfurization is mainly based on wet desulfurization technology, accounting for about 85%. Among the wet desulfurization technologies, there are mainly calcium, magnesium and ammonia desulfurization technologies. Among them, the by-product of calcium desulfurization is gypsum, which is widely used and has low disposal difficulty. The by-products of ammonia desulfurization can be recycled. However, the technology for comprehensive resource recycling and utilization of the by-products of wet magnesium desulfurization is not yet mature, and there are currently few large-scale industrial applications. Therefore, the disposal of magnesium desulfurization by-products is more difficult, and generally more treatment methods are to enter the landfill for landfill disposal in accordance with the general industrial solid waste standards. Section 6.2 of the "General Industrial By-product Solid Storage and Landfill Pollution Control Standard" (GB 18599-2020) implemented on July 1, 2021, general industrial by-product solids entering Class II sites should meet the following requirements at the same time:

[0003] a) The organic matter content is less than 5% (except for coal gangue), and the determination method shall be carried out in accordance with HJ 761;

[0004] b) The total amount of water-soluble salts is less than 5%. The determination method shall be in accordance with NY / T 1121.16.

[0005] Theoretically, the total amount of water-soluble salts in the byproducts of wet magnesium desulfurization is greater than 5%. Sampling and testing have shown that the water-soluble salt content ranges from 10% to 20%, which does not meet the requirements for acceptance into general industrial solid waste landfills and cannot be directly landfilled. A specific process must be used to remove the water-soluble salts from the byproducts of magnesium desulfurization to reduce the content to less than 5% to meet landfill acceptance criteria. To address the issue of excessive water-soluble salts in magnesium desulfurization byproducts, which prevent them from entering general solid waste landfills, a process for removing water-soluble salts from magnesium desulfurization byproducts has been invented. Currently, no patent applications have been filed for the related technology. Summary of the Invention

[0006] In order to solve the problem that the soluble salt content of magnesium-based desulfurization by-products exceeds national standards and cannot be directly landfilled as general industrial by-products, the present invention provides a process route for reducing the soluble salt content of magnesium-based desulfurization by-products to below 5%, so that it meets relevant standards and can be directly landfilled.

[0007] The present invention addresses the issue of excessive soluble salts in magnesium-based desulfurization byproducts. The process involves conveying the solid byproducts from the magnesium-based desulfurization process to a crushing system, which crushes the byproducts into particles no larger than 2 mm. The crushed particles then enter a liquid-solid mixing device equipped with a dosing device and a water injection system. The dosing device adds a measured amount of slaked lime to the mixing device based on the byproduct solid flow rate and soluble salt content, reacting with the dissolved portion of the byproducts to form a precipitate, thereby removing the soluble salts. The water injection device adds water to provide a reaction environment and necessary fluidity. The liquid-to-solid ratio of the injected water is adjusted between 4 and 5 based on the soluble salt content of the byproducts. After 3 minutes of mixing, most of the soluble salts in the byproducts have dissolved in the water and reacted with the slaked lime to form a precipitate, thereby reducing the soluble salt content. The resulting mixed slurry is then conveyed to a liquid-solid separation system for liquid-solid separation. After liquid-solid separation, the mixed slurry is separated into a filter cake with a water content of ≤15% and a filtrate containing ions. The filter cake is sent to the solid waste dump, ventilated and dried before being transported to landfill for disposal, and the filtrate enters the waste liquid treatment system for further treatment.

[0008] The waste liquid treatment system can be divided into two parts based on the on-site environmental protection requirements: the waste liquid concentration system and the waste liquid treatment system. If the site has a certain waste liquid treatment capacity, only the waste liquid concentration system is required. If the site does not have waste liquid treatment capacity, both the waste liquid concentration system and the waste liquid treatment system are required.

[0009] The waste liquid concentration system includes a waste liquid tank, a cyclone waste liquid concentrator, and a concentrated waste liquid tank. The filtrate from the liquid-solid separation system enters the waste liquid tank for temporary storage. It is then pumped and piped into the cyclone waste liquid concentrator for concentration. The concentration ratio is adjusted between 5-10:1 based on the ion content of the waste liquid. The concentrated waste liquid enters the concentrated waste liquid tank for further processing. The diluted waste liquid is then returned to the mixing device for reuse, reducing system water consumption and conserving resources.

[0010] The wastewater treatment system includes a filtration tank, a sedimentation tank, and a flocculation tank. The filtration tank primarily uses quartz sand as the filter medium to filter and concentrate solid particles from the wastewater. The filtered supernatant flows by gravity into the sedimentation tank. In the sedimentation tank, a precipitant is added based on the ions present in the liquid to precipitate the ions. The precipitated slurry then enters the flocculation tank, where a flocculant is added to agglomerate the precipitate into clusters for easy removal. The slurry containing the clusters is pumped and piped back to the liquid-solid separation system to complete the separation.

[0011] The present invention provides a process for removing water-soluble salts from magnesium desulfurization by-products. Currently, there is no relevant patent in China. The advantages of this process are as follows:

[0012] 1) The technology has a high degree of innovation and broad application prospects. There is currently no similar technology for this process. Since GB18599-2020 will be implemented in July 2021, this process is in high demand and has broad application prospects.

[0013] 2) Low construction and subsequent operating costs. The process is relatively simple, the equipment are all mature products in the market, the cost is low, and the chemicals required for operation are all common items in the market and the price is low.

[0014] 3) Energy saving and environmental protection: this process has low energy consumption, reuses water resources, and has no waste liquid. After taking dust prevention measures in the transportation link, there is no dust pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below with reference to the accompanying drawings and examples.

[0016] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0017] Figure 2 It is a schematic flow chart of the waste liquid treatment system of the present invention;

[0018] In the figure, 1-transportation device and crushing system, 2-liquid-solid mixing device, 3-liquid-solid separation system, 4-waste liquid concentration system, 5-waste liquid system, 6-water injection device. DETAILED DESCRIPTION

[0019] In order to more clearly describe the purpose and technical advantages of the present invention, the following is a further detailed description with reference to the accompanying drawings and specific embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] Example 1: The crushing system can select different crushing modes, including single-stage crushing, dual-stage crushing, and combined primary and fine crushing, depending on the size and hardness of the incoming material, to meet the requirement of a finished product with a particle size of no more than 2mm. The finished product is screened, and those that meet the requirements are conveyed to a mixing device via conveyor belts or other equipment. Unsatisfactory materials are returned to the crusher inlet for secondary crushing.

[0021] Example 2: Liquid-solid mixing equipment can be configured in a variety of ways to accommodate different waste flow rates and soluble salt contents. Spiral sand washers, drum sand washers, tanks with agitators, and other equipment can all meet diverse requirements. The mixing equipment used must incorporate appropriate corrosion and wear protection measures to ensure long-term, stable operation. During the initial trial run, dissolution testing should be conducted promptly, and mixing time and intensity should be adjusted to ensure that soluble salt levels meet national standards.

[0022] Example 3: The equipment for the liquid-solid separation system is selected based on the viscosity and crystal particle size of the byproduct solid slurry. Depending on the viscosity and crystal particle size, various liquid-solid separation methods can be used to separate the mixed slurry into solids and liquids, including vibrating screens, belt liquid-solid separators, disc liquid-solid separators, and centrifugal liquid-solid separators. When the viscosity is low and the particles are large, vibrating screens are preferred. For medium viscosities, belt liquid-solid separators and disc liquid-solid separators can be used. For high viscosities and small particles, a centrifugal liquid-solid separator or filter press is required to ensure effective liquid-solid separation.

[0023] Example 4: The waste liquid treatment system is selectively configured based on the types of soluble salts in the byproduct solids. If the waste contains a relatively simple set of soluble salts and contains no toxic or hazardous substances, the waste liquid treatment system can be eliminated. The filtrate after liquid-solid separation can be directly returned to the mixing system for continued recycling. The ions therein will gradually precipitate as they continue to concentrate and enrich, without the need for special treatment. This method is the simplest, most convenient, and lowest cost. If the filtrate contains complex ionic composition or contains special ions, targeted measures must be taken to render them harmless.

Claims

1. A process for removing water-soluble salts from magnesium desulfurization by-products, comprising a crushing system, a mixing device, a liquid-solid separation The separation system, waste liquid concentration system and waste liquid treatment system have the following process: the solid by-product of magnesium desulfurization is sent to the crushing system by the conveying device, the crushing system crushes the by-product solid, and the particles with a particle size of no more than 2mm enter the liquid-solid mixing device, the mixing device is equipped with a dosing device and a water injection device, the dosing device adds a measured amount of slaked lime into the mixing device according to the by-product solid flow rate and soluble salt content to remove the soluble salt in the by-product, the water injection device adds water to provide a reaction environment and necessary fluidity, the mass ratio of the injected water to the by-product solid is 4-5:1, the mixed slurry is stirred for 3 minutes and then sent to the liquid-solid separation system by a slurry pump for liquid-solid separation treatment, the mixed slurry is separated into filter cake and filtrate after liquid-solid separation; the water content of the filter cake is ≤15% and the soluble salt content is ≤5%, the filter cake is sent to the solid waste stockpile and can be transported to the landfill for disposal after ventilation and drying, and the filtrate enters the waste liquid concentration system and The waste liquid treatment system is further processed; the waste liquid concentration system includes a waste liquid tank, a cyclone waste liquid concentrator and a concentrated waste liquid tank. The filtrate enters the waste liquid tank from the liquid-solid separation system for temporary storage and is sent to the cyclone waste liquid concentrator by a pump and a pipeline for concentration. The concentration ratio is adjusted between 5-10:1 according to the ion content in the waste liquid. The concentrated waste liquid enters the concentrated waste liquid tank for further treatment, and the diluted waste liquid is returned to the mixing device for reuse; the waste liquid treatment system includes a filter tank, a sedimentation tank and a flocculation tank. The filter tank uses quartz sand as a filter medium to filter solid particles in the concentrated waste liquid. The supernatant after filtration enters the sedimentation tank by gravity. In the sedimentation tank, a precipitation agent is added according to the ions contained in the liquid to precipitate the ions; the slurry after precipitation enters the flocculation tank, and a flocculant is added in the flocculation tank to make the precipitate condense into agglomerates; the slurry containing agglomerates is transported back to the liquid-solid separation system by a pump and a pipeline to complete the liquid-solid separation.

2. The process for removing water-soluble salts from magnesium desulfurization by-products according to claim 1, characterized in that: The mixing time of the mixed slurry in the mixing device is 3 minutes.

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