Direct reduction process and apparatus for treating viscous sludge

Abstract

The present application relates to a kind of direct reduction process and device for processing viscous sludge, belong to metallurgical solid waste processing field, viscous sludge is transported to liquid nitrogen pulverizer by sealing feeder in the present application, sludge is scattered or ground into fine powder in liquid nitrogen pulverization and is transported to strong mixer, sludge powder is mixed with other dust removal ash, binder, coke powder etc. in the mixer and is mixed into ball press machine to press ball, green ball is dried and enters reduction furnace to carry out calcination reduction, high-temperature metallized pellet is cooled and is transported to finished product bin.The low-temperature nitrogen gas volatilized by liquid nitrogen pulverizer is used for cooling partly, and the high-temperature nitrogen gas comes out is mixed with another part of low-temperature nitrogen gas to adjust temperature.The present application replaces sludge dryer by liquid nitrogen pulverizer, saves coal gas consumption of sludge drying and pellet drying and respective construction of flue gas furnace for drying, reduces compressed air consumption for burning, high power consumption of dryer, reduces production and construction cost.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical solid waste treatment and relates to a direct reduction process and apparatus for treating viscous sludge. Background Technology

[0002] The sticky sludge from steel mills cannot be used directly due to its viscosity, often causing blockages in silos, conveying equipment, or mixing equipment. Once it adheres or hardens, repair is difficult. Traditional direct reduction processes involve drying the sticky sludge in a dryer, mixing it with other ingredients in a mixer, and then briquetting the mixture. To ensure briquetting effectiveness, water needs to be added in the mixer to adjust the moisture content. This process of dewatering the sticky sludge at the beginning and then adding water during mixing wastes a significant amount of energy. The sludge drying is merely to eliminate its stickiness for later use. Both sludge drying and the drying of the briquette require large amounts of gas, making the entire system uneconomical and increasing operating costs. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a direct reduction process and apparatus for treating sticky sludge. The low-temperature pulverization technology solves the problems of sticky sludge's stickiness and the consumption of gas in the drying process. At the same time, the nitrogen generated by the low-temperature pulverization is used for drying the green pellets after exchanging heat with the high-temperature metallized pellets, thus saving the gas consumed in drying the green pellets. This achieves multiple benefits.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A direct reduction process for treating viscous sludge includes the following steps:

[0006] The viscous sludge is transported to a liquid nitrogen pulverizer, where it is broken up or ground into fine powder. It is then quantitatively mixed with other dust, iron concentrate, binder, coke powder, etc.

[0007] The mixed materials are pressed into green pellets, which are then dried, calcined, reduced, cooled, and transported to the finished product warehouse.

[0008] A portion of the low-temperature nitrogen gas volatilized from the liquid nitrogen pulverizer is used for cooling and heat exchange with the calcined and reduced metallized pellets. The high-temperature nitrogen gas after heat exchange is mixed with another portion of low-temperature nitrogen gas and used to press and dry the green pellets.

[0009] A portion of the low-temperature nitrogen gas volatilized from the liquid nitrogen pulverizer is transported to the finished product silo for oxidation protection of the metallized pellets, while the excess nitrogen gas is directly transported to the oxygen plant to be reprocessed into liquid nitrogen.

[0010] Optionally, the gas from the dried green pellets can be transported to the oxygen plant after undergoing dust removal and drying once.

[0011] Optionally, a portion of the low-temperature nitrogen gas volatilized by the liquid nitrogen pulverizer is sent to a cooler to exchange heat with metallized pellets at 900℃~1200℃. The resulting high-temperature nitrogen gas is then mixed with another portion of the low-temperature nitrogen gas to adjust the temperature to 250℃~400℃.

[0012] Optionally, the feed rate of the liquid nitrogen pulverizer can be matched with the amount of viscous sludge that participates in the mixing after pulverization.

[0013] Optionally, the collected purified nitrogen is used in two ways: one for anti-oxidation protection of the metallized pellet product silo, another for cooling and heat exchange of the high-temperature metallized pellets, and the third for mixing with the high-temperature nitrogen after heat exchange to cool the mixture. The mixed gas is then used for drying the green pellets. The dried nitrogen and excess nitrogen are sent to an oxygen plant to be purified and cooled again to produce liquid nitrogen, thus achieving nitrogen recycling.

[0014] A direct reduction apparatus for treating viscous sludge comprises, in sequence along the material conveying direction, a liquid nitrogen pulverizer, a high-intensity mixer, a briquetting machine, a dryer, a reduction furnace, a cooler, and a silo; the liquid nitrogen mixer is supplied with nitrogen from an oxygen generator or a nitrogen plant; the nitrogen outlet of the liquid nitrogen pulverizer is connected to the cooler and the silo.

[0015] Optionally, the nitrogen outlet of the cooler and the nitrogen outlet of the liquid nitrogen pulverizer are both connected to the dryer via a mixing and temperature control device.

[0016] Optionally, the reduction furnace is connected to a waste heat boiler.

[0017] Optionally, it also includes a sealed screw feeder under the silo for conveying material into the liquid nitrogen pulverizer.

[0018] Optionally, an induced draft fan is provided between the temperature control device and the dryer.

[0019] The beneficial effects of this invention are as follows:

[0020] Cryogenic pulverization typically uses liquid nitrogen as a cold source. Liquid nitrogen is produced through air separation and is usually a byproduct of oxygen production in steel plants. It has a large output and relatively low cost. Liquid nitrogen can be directly fed into the pulverizer, where the material is cooled to a brittle state and then pulverized mechanically using steel balls, rotating impellers, or scrapers. For sticky sludge, cryogenic liquid nitrogen pulverization allows for rapid transport to a mixer before thawing, resolving its stickiness issue. The vaporized nitrogen can then be fully utilized in the system, directly saving on gas consumption for drying the sludge and pressed raw pellets.

[0021] This invention replaces the sludge dryer with a liquid nitrogen pulverizer, saving on gas consumption for sludge drying and pellet drying, as well as the construction of separate flue gas furnaces for drying, reducing compressed air consumption for combustion, and lowering the high power consumption of the dryer, thereby reducing production and construction costs.

[0022] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0024] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0025] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0027] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0028] Please see Figure 1A direct reduction process for treating sticky sludge includes the following steps: the sticky sludge is fed into a liquid nitrogen pulverizer via a sealed feeder, where it is broken up or ground into fine powder. The powder is then fed into a high-intensity mixer via the sealed feeder. The sludge powder is mixed with other dust, iron concentrate, binder, coke powder, etc., which are fed into the mixer. The mixed material is then fed into a briquetting machine for briquetting. The briquetting green pellets are dried and then fed into a reduction furnace for calcination and reduction. The high-temperature metallized pellets are cooled in a cooler and then transported to a finished product silo. A portion of the low-temperature nitrogen gas volatilized from the liquid nitrogen pulverizer is sent to the cooler for heat exchange with metallized pellets at 900℃~1200℃. The resulting high-temperature nitrogen gas is mixed with another portion of low-temperature nitrogen gas and the temperature is adjusted to 250℃~400℃. It is then conveyed to the green pellet dryer by an induced draft fan for green pellet drying. The dried gas is then sent to the oxygen plant after passing through dust removal and drying once. A portion of the low-temperature nitrogen gas from the pulverizer is also sent to the finished product silo for oxidation protection of the metallized pellets. Excess nitrogen gas is directly sent to the oxygen plant to regenerate liquid nitrogen.

[0029] The sludge is conveyed to a liquid nitrogen pulverizer via a sealed conveyor. The pulverizer has a liquid nitrogen inlet, and the vaporized nitrogen gas in the pulverizer is dried and dust-removed before being output by a fan. The pulverized material enters a sealed intermediate tank or silo and is output via a sealed conveyor. The tank or silo contains a pipeline for further gas collection.

[0030] The material pulverized by the liquid nitrogen pulverizer directly enters the buffer hopper of the mixer. The feed rate of the liquid nitrogen pulverizer is matched with the amount of viscous sludge entering the mixer after pulverization. The viscous sludge pulverized by liquid nitrogen is mixed with other dust, iron concentrate, reducing agent and binder in the mixer. After mixing, the material is briquetting, dried and then sent to the reduction furnace for roasting and reduction to produce metallized pellets.

[0031] The collected purified nitrogen is used in two ways: one for anti-oxidation protection of the metallized pellet product silo, and another for cooling and heat exchange of the high-temperature metallized pellets. The third is mixed with the high-temperature nitrogen after heat exchange to cool the mixture to 250°C to 400°C. This mixed gas is then used for drying the green pellets. The dried nitrogen and excess nitrogen are sent to an oxygen plant to be purified and cooled again to produce liquid nitrogen, thus achieving nitrogen recycling.

[0032] The following specific embodiment further illustrates this method, which provides a direct reduction process for treating steelmaking OG sludge in steel enterprises, including the following steps:

[0033] 1. OG sludge is grabbed into the feeding hopper by the grab bucket feeder and then conveyed to the liquid nitrogen pulverizer by the sealed screw feeder under the silo. The sludge is broken up or ground into fine powder in the liquid nitrogen pulverizer and then conveyed to the high-intensity mixer by the sealed feeder.

[0034] 2. The crushed sludge powder is mixed with other dust, iron concentrate, binder, coke powder and other materials conveyed to the mixer. The mixed materials are then fed into the briquetting machine for briquetting. The pressed green briquettes are dried and then fed into the reduction furnace for calcination and reduction. The high-temperature metallized briquettes are cooled in the cooler and then transported to the finished product warehouse.

[0035] 3. A portion of the nitrogen gas volatilized from the liquid nitrogen pulverizer is sent to the cooler for heat exchange with the metallized pellets at 900℃~1200℃. The high-temperature nitrogen gas is then mixed with another portion of low-temperature nitrogen gas and the temperature is adjusted to 250℃~400℃. It is then conveyed to the green pellet dryer by an induced draft fan for green pellet drying. The dried gas is then sent to the oxygen plant after passing through dust removal and drying once. A portion of the low-temperature nitrogen gas from the pulverizer is also sent to the finished product silo for oxidation protection of the metallized pellets. The excess nitrogen gas is directly sent to the oxygen plant to regenerate liquid nitrogen.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. The cooling medium used in the low-temperature pulverization technology described in the present invention and its application after gasification, although the present invention has been described in detail with reference to preferred embodiments, should be understood by those skilled in the art. For example, using dry ice medium to perform low-temperature pulverization of viscous sludge, using gasified CO2 to cool high-temperature metallized pellets, and using high-temperature CO2 to dry green pellets can be used to make equivalent substitutions to the technical solutions of the present invention, but without departing from the spirit and scope of the technical solutions of the present invention, and all such substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A direct reduction process for treating viscous sludge, characterized in that, Includes the following steps: The viscous sludge is transported to a liquid nitrogen pulverizer, where it is broken up or ground into fine powder. It is then quantitatively mixed with dust, iron concentrate, binder, and coke powder. The mixed materials are pressed into green pellets, which are then dried, calcined, reduced, cooled, and transported to the finished product warehouse. A portion of the low-temperature nitrogen gas volatilized from the liquid nitrogen pulverizer is used for cooling and heat exchange with the calcined and reduced metallized pellets. The high-temperature nitrogen gas after heat exchange is mixed with another portion of low-temperature nitrogen gas and used to press and dry the green pellets. A portion of the low-temperature nitrogen gas volatilized from the liquid nitrogen pulverizer is transported to the finished product silo for oxidation protection of the metallized pellets, while the excess nitrogen gas is directly transported to the oxygen plant to regenerate liquid nitrogen. In this process, a portion of the low-temperature nitrogen gas volatilized from the liquid nitrogen pulverizer is sent to the cooler to exchange heat with the metallized pellets at 900℃~1200℃. The high-temperature nitrogen gas that comes out is mixed with another portion of the low-temperature nitrogen gas to adjust the temperature to 250℃~400℃.

2. The direct reduction process for treating viscous sludge according to claim 1, characterized in that, The gas from the dried green pellets is transported to the oxygen plant after undergoing dust removal and drying once.

3. The direct reduction process for treating viscous sludge according to claim 1, characterized in that, The feed rate of the liquid nitrogen pulverizer is matched with the amount of viscous sludge that participates in the mixing after pulverization.

4. The direct reduction process for treating viscous sludge according to claim 1, characterized in that, The collected purified nitrogen is used in two ways: one for anti-oxidation protection of the metallized pellet product silo, another for cooling and heat exchange of the high-temperature metallized pellets, and the third for mixing with the high-temperature nitrogen after heat exchange to cool the mixture. This mixed gas is then used for drying the green pellets. The dried nitrogen and excess nitrogen are sent to an oxygen plant to be purified and cooled again to produce liquid nitrogen, thus achieving nitrogen recycling.

5. A direct reduction apparatus for treating viscous sludge, characterized in that: This direct reduction apparatus is suitable for the direct reduction process according to any one of claims 1 to 4; The direct reduction device is arranged in sequence along the material conveying direction as a liquid nitrogen pulverizer, a high-intensity mixer, a briquetting machine, a dryer, a reduction furnace, a cooler, and a silo; The liquid nitrogen pulverizer is supplied with nitrogen from an oxygen generator or a nitrogen plant. The nitrogen outlet of the liquid nitrogen pulverizer is connected to the cooler and the hopper.

6. The direct reduction apparatus for treating viscous sludge according to claim 5, characterized in that: The nitrogen outlets of the cooler and the liquid nitrogen pulverizer are both connected to the dryer via a mixing and temperature control device.

7. The direct reduction apparatus for treating viscous sludge according to claim 5, characterized in that: The reduction furnace is connected to a waste heat boiler.

8. The direct reduction apparatus for treating viscous sludge according to claim 5, characterized in that: It also includes a sealed screw feeder for conveying materials into a liquid nitrogen pulverizer.

9. The direct reduction apparatus for treating viscous sludge according to claim 6, characterized in that: An induced draft fan is installed between the mixing and temperature regulating device and the dryer.

Images