A system and method for treating oil-containing floating slag by using liquid steel slag coupled with biomass

Abstract

This invention discloses a system and method for treating oily sludge using liquid steel slag coupled with biomass. The system uses a porous rotary cup granulator to granulate the liquid steel slag into uniformly sized high-temperature slag. The granulated slag is then transported to a rotary pyrolysis reactor where it directly contacts biomass and undergoes catalytic pyrolysis. The high-quality pyrolysis gas generated can be used as a chemical feedstock and fuel. The resulting biochar and solid steel slag mixture is transported to a high-temperature hydrothermal reactor for hydrothermal dehydration with the oily sludge. The gas generated from the hydrothermal reaction can be used as pyrolysis gas. The resulting hydrothermal liquid product, after filtration, yields liquid biofuel and a solid hydrothermal product consisting of hydrothermal char, biochar, and granulated steel slag. This invention utilizes the waste heat from liquid steel slag coupled with biomass energy to synergistically treat oily sludge, obtaining usable high-quality pyrolysis gas, biofuel, and hydrothermal char products with calorific value, achieving energy conservation, emission reduction, pollution reduction, and carbon reduction.

Description

Technical Field

[0001] This invention utilizes the waste heat from liquid steel slag coupled with biomass to jointly treat and utilize oily scum, belonging to the field of solid waste and hazardous waste resource treatment and utilization. In particular, it relates to a system and method for treating oily scum using liquid steel slag coupled with biomass. Background Technology

[0002] In wastewater treatment plants in the petrochemical industry, oily sludge mainly originates from the bottom sludge of oil separators, the scum from flotation tanks, and excess activated sludge, collectively referred to as "the three sludges." Due to the different sources of crude oil, the composition of oily sludge in petrochemical wastewater treatment plants is extremely complex. Oily scum accounts for the largest proportion of the "three sludges," approximately 80% of the total. Its composition is complex, containing not only common components such as asphaltene, waxes, colloids, and suspended solids, but also toxic and harmful substances such as heavy metal salts, phenols, anthracene, and pyrene. Oily scum has a high water content (90%–98%), high viscosity, and a high degree of emulsification, making water removal extremely difficult and subsequent resource recovery extremely challenging. On the other hand, dehydrated oily scum has a high calorific value, close to that of heavy oil, making it an excellent fuel after water removal and possessing extremely high resource utilization value.

[0003] The porous structure of biochar gives it strong physical adsorption capacity, making it an ideal adsorbent material. Furthermore, biochar provides a high-purity carbon-based framework in hydrothermal reactions with other materials, promoting deeper hydrothermal reactions. Despite the clean and efficient utilization advantages of biomass, its current inefficient utilization and high processing costs mean that most biomass in China is disposed of through field stockpiling or incineration. Additionally, steel slag is a major solid waste from China's steel industry, with an annual output of approximately 100 million tons, but a utilization rate of only 30%. Liquid steel slag, a major byproduct of blast furnace ironmaking, possesses a large amount of high-quality waste heat when discharged from the furnace, with a slag discharge temperature of 1400–1700℃. This waste heat is currently not well recovered and utilized. Therefore, effectively solving the problem of high-quality waste heat recovery and utilization from steel slag is key to achieving energy conservation and emission reduction in the steel industry. Steel slag itself contains metallic components such as CaO, MgO, Al2O3, and Fe3O4, which possess certain catalytic activity during biomass pyrolysis, significantly promoting the degree of biomass pyrolysis and tar decomposition, thus yielding more hydrogen-rich gas. Therefore, utilizing the high-temperature waste heat of liquid steel slag coupled with biomass pyrolysis and resource-based treatment of oily slag can not only achieve heat recovery from liquid blast furnace slag but also promote the conversion of low-grade energy from biomass and oily slag into high-grade energy, obtaining high-quality energy products through comprehensive treatment of both biomass and oily slag. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies and address the problems of inefficient recovery and utilization of waste heat from liquid steel slag, low biomass utilization rate, and difficulty in dewatering oily scum, this invention proposes a system and method for treating oily scum using liquid steel slag coupled with biomass. This system comprehensively treats and utilizes the aforementioned solid waste and hazardous waste, and while treating biomass and oily scum, it can obtain usable high-quality pyrolysis gas, biomass fuel oil, and hydrothermal char products with calorific value, thereby achieving energy conservation, emission reduction, pollution reduction, and carbon reduction.

[0005] The purpose of this invention is to effectively utilize the waste heat of liquid steel slag to produce biochar while simultaneously using the liquid steel slag as a heat carrier to heat the biomass and promote its deep pyrolysis reaction to produce high-quality pyrolysis products. This solves the problem of the heat source required for biomass pyrolysis. On the other hand, the active components such as metal oxides in the steel slag can act as catalysts for the pyrolysis reaction, improving the quality of the pyrolysis gas. Furthermore, the granulated steel slag and biochar mixture obtained after the pyrolysis reaction can be used as an additive for the hydrothermal reaction of oily scum, promoting the dehydration performance of the oily scum and improving the quality of the hydrothermal liquid products. By processing biomass and oily scum, usable high-quality pyrolysis gas, biomass fuel oil, and hydrothermal char products with calorific value can be obtained, achieving energy conservation, emission reduction, pollution reduction, and carbon reduction.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A system for treating oily scum using liquid steel slag coupled with biomass includes: The system includes a liquid steel slag container, a porous rotating cup rotary granulation device, a rotary pyrolysis reactor, an oil-containing slag feeding device, a high-temperature hydrothermal reactor, a solid-liquid separation device, and a fluidized bed boiler. The outlet of the liquid steel slag container is connected to the inlet of the porous rotating cup rotary granulation device; the material outlet of the porous rotating cup rotary granulation device is connected to the material inlet of the rotary pyrolysis reactor; the material outlet of the rotary pyrolysis reactor is connected to the material inlet of the high-temperature hydrothermal reactor; the solid-liquid phase material outlet of the high-temperature hydrothermal reactor is connected to the material inlet of the solid-liquid separation device; and the solid phase outlet of the solid-liquid separation device is connected to the material inlet of the fluidized bed boiler.

[0007] The porous rotating cup granulation device is equipped with a liquid steel slag inlet and a granulated steel slag outlet; The rotary pyrolysis reactor is equipped with a biomass inlet, a granulated steel slag inlet, a pyrolysis gas outlet, and a material outlet, wherein the material outlet is connected to the material inlet of the high-temperature hydrothermal reactor. The high-temperature hydrothermal reactor is equipped with a gas inlet, a solid material inlet, a solid material outlet, and an essential oil outlet. The solid material outlet is connected to a solid-liquid separation device. The high-temperature hydrothermal reactor is equipped with temperature and pressure monitoring devices, an endoscope for stirring the reaction solution, a magnetic float, and allows for real-time observation of the reaction inside the reactor. The solid-liquid separation device can efficiently separate the products after hydrothermal reaction, and the remaining solid material is a mixture of steel slag, biochar, and oily slag hydrothermal char. Among them, the high-calorific-value biochar mixed with oily slag is directly usable. The resulting liquid product is high-quality biofuel, which can be used for subsequent processing of chemical raw materials. Fluidized bed boilers are equipped with continuous feed and discharge ports, enabling continuous production of iron-rich ash slag.

[0008] The beneficial effects of this invention are: 1) The system and method proposed in this invention effectively utilize the waste heat of high-temperature liquid steel slag to catalytically pyrolyze biomass while producing high-quality pyrolysis gas: biomass pyrolysis is carried out in a rotary reactor, and the pyrolysis products are catalytically cracked in a pelletizing reactor. This system recovers the heat from the liquid steel slag in the form of combustible gas, promoting the degree of biomass pyrolysis reaction and producing hydrogen-rich gas, biochar, and some tar products. A large amount of hydrogen-rich gas can be used as chemical raw materials and fuel gas.

[0009] 2) The system and method proposed in this invention, in a high-temperature hydrothermal reactor, greatly improve the dehydration efficiency of oily scum in the hydrothermal process due to the use of liquid steel slag as a catalyst and biochar as a carbon source to provide a carbon skeleton. Compared with the dehydration rate of oily scum alone in hydrothermal process, the dehydration rate is increased by 20% to 25%.

[0010] 3) The system and method proposed in this invention, in which steel slag, biochar and reducing atmosphere in high-temperature hydrothermal reactor can promote the cracking of long-chain oil molecules in tar and oily slag into short chains, the bio-oil obtained in the hydrothermal process has extremely low oxygen content, the quality of the oil phase is improved, and it can be directly used as biofuel, realizing the efficient utilization of waste heat of liquid steel slag and converting it into high-quality bioenergy.

[0011] 4) In the system and method proposed in this invention, the gases generated during the hydrothermal process mainly consist of CO, H2, and C. x H y (Hydrocarbons) provide a strong reducing atmosphere, and the iron-containing phase in the steel slag is partially reduced to metallic iron, which is conducive to the efficient recycling of iron resources. The steel slag, biochar, and oily slag carbon obtained after the hydrothermal reaction are burned in a fluidized bed reactor to obtain heat. This heat can be used for heating and power generation, and the iron-rich ash slag after combustion can be used as building materials and raw materials for iron recycling.

[0012] 5) The system and method proposed in this invention can effectively treat oily slag in a harmless and efficient manner, while also making good use of the residual heat and catalytic reforming performance of steel slag. It also produces high-grade energy gas and biofuel, and can comprehensively treat and utilize liquid steel slag, biomass and oily slag, thereby enhancing the efficiency of resource treatment and utilization of solid waste and hazardous waste. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a system and method for treating oily scum using liquid steel slag coupled with biomass, according to the present invention. Detailed Implementation

[0014] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0015] Example 1: 1) Liquid steel slag at 1600℃ is poured from the smelting furnace into a liquid steel slag container. The liquid steel slag flows into a porous rotating cup granulation device through the container outlet. At the same time, air (20℃) is introduced for cooling. The temperature of the granulated steel slag in the granulation chamber wall and slag collection device is about 1000℃. The air is heated to 150℃ through heat exchange.

[0016] 2) Poplar sawdust and granulated steel slag 1 are continuously fed into a rotary pyrolysis reactor at a mass ratio of 1:3 for direct contact pyrolysis reaction. Granulated steel slag 1 produced in step 1) serves as a catalyst and simultaneously undergoes catalytic pyrolysis reaction with poplar sawdust using its own heat. The mass ratio of H2 in the generated cracked gas is 60%. At the material outlet of the rotary pyrolysis reactor, the temperature of granulated steel slag 2 and biochar is approximately 50°C.

[0017] 3) Add the mixture of granulated steel slag II and poplar wood biochar and oily scum to a high-temperature hydrothermal reactor at a mass ratio of 1:50. Set the hydrothermal reaction temperature of the high-temperature hydrothermal reactor to 300℃, the reaction time to 60min, and the rotation speed of the magnetic rotor to 300rpm.

[0018] 4) The solid-liquid phase mixture was transported to a solid-liquid device to obtain steel slag III, poplar wood biochar, oil residue char and high-quality biofuel.

[0019] 5) A device for recovering and storing pyrolysis gas generated in a rotary pyrolysis reactor and hydrothermal gas generated in a high-temperature hydrothermal reactor is used to obtain high-quality energy gas. The hydrothermal gas product can be used for the production of chemical raw materials or directly as fuel gas.

[0020] 6) The granulated steel slag, poplar wood biochar, and high-calorific-value oily slag hydrothermal char obtained after filtration are fed into a fluidized bed reactor for power generation and heating; at the same time, the product iron-rich ash slag is obtained, which can be used as building materials and raw materials for iron recycling.

[0021] Example 2: 1) Liquid steel slag at 1700℃ is poured from the smelting furnace into a liquid steel slag container. The liquid steel slag flows into a porous rotating cup granulation device through the container outlet. At the same time, air (20℃) is introduced for cooling. The temperature of the granulated steel slag in the granulation chamber wall and slag collection device is about 1100℃. The air is heated to 100℃ through heat exchange.

[0022] 2) Corn stalks and granulated steel slag II are continuously fed into a rotary pyrolysis reactor at a mass ratio of 1:4 for direct contact pyrolysis. Granulated steel slag I produced in step 1) serves as a catalyst and simultaneously undergoes catalytic pyrolysis with corn stalks using its own heat. The H2 mass ratio in the generated cracked gas is 70%. At the material outlet of the rotary pyrolysis reactor, the temperature of granulated steel slag II and biochar is approximately 70°C.

[0023] 3) Add the mixture of granulated steel slag II, corn straw biochar and oily scum to a high-temperature hydrothermal reactor at a mass ratio of 1:50. Set the hydrothermal reaction temperature of the high-temperature hydrothermal reactor to 400℃, the reaction time to 120min, and the rotation speed of the magnetic rotor to 500rpm.

[0024] 4) The solid-liquid phase mixture was transported to a solid-liquid device to obtain steel slag III, corn straw biochar, oil residue char and high-quality biofuel.

[0025] 5) A device for recovering and storing pyrolysis gas generated in a rotary pyrolysis reactor and hydrothermal gas generated in a high-temperature hydrothermal reactor is used to obtain high-quality energy gas. The hydrothermal gas product can be used for the production of chemical raw materials or directly as fuel gas.

[0026] 6) The granulated steel slag, corn stalk biochar, and high-calorific-value oily slag hydrothermal char obtained after filtration are fed into a fluidized bed reactor for power generation and heating; at the same time, the product iron-rich ash slag is obtained, which can be used as a raw material for building materials or iron recycling.

Claims

1. A method for treating oil-containing floating sludge using liquid steel slag coupled with biomass, characterized by, Includes the following steps: (1) Liquid steel slag at 1500~1700℃ is poured from the smelting furnace into a liquid steel slag container. The liquid steel slag flows into the porous rotating cup rotary granulation device through the container outlet. The rotation speed of the porous rotating cup is adjustable from 800 to 2000 rpm. When the molten slag is accelerated to the set speed, the liquid high-temperature molten slag flies out tangentially along the edge of the rotating cup opening under the action of centrifugal force. It is completely solidified and granulated before hitting the granulation chamber wall and the slag collection device, thus obtaining granulated steel slag with uniform particle size. (2) In step (1), ambient temperature air is continuously introduced into the porous rotating cup granulation device for cooling. The air is blown in from the bottom of the granulation chamber and after heat exchange with the steel slag, granulated steel slag with a temperature of 900~1100℃ is obtained. The air is heated to 100~150℃ by heat exchange and then blown out from the top of the granulation chamber. The heated air is used as boiler oxidation gas. (3) The granulated steel slag I and biomass obtained in step (2) are respectively transported to a rotary pyrolysis reactor by their respective conveying devices for direct contact pyrolysis reaction. Steel slag I uses its own heat to undergo catalytic pyrolysis reaction with biomass, and after the reaction, a large amount of hydrogen-rich high-quality pyrolysis gas, as well as liquid tar and solid products are produced; among them, the pyrolysis solid products include granulated steel slag II and biochar. (4) The granulated steel slag I obtained in step (2) has a catalytic metal element as a pyrolysis catalyst. The temperature of the rotary reactor is determined by the temperature of the granulated steel slag I. The rotation speed of the rotary reactor is in the range of 5~40 r / min. The outlet temperature of the solid material in the rotary pyrolysis reactor is 40~70℃. The solid material contains granulated steel slag II and biochar. The mass ratio of biomass to granulated steel slag in the rotary reactor is 1: (1.5~3). (5) The liquid tar, granulated steel slag II and biochar solid products generated in step (3) are respectively transported to a high-temperature hydrothermal reactor and undergo hydrothermal dehydration reaction with oily slag. Under the catalytic action of biomass carbon-based skeleton and steel slag, the liquid tar is decomposed, and the oil-water structure in the oily slag is destroyed. After sufficient dehydration and conversion, oily slag char is obtained. After the hydrothermal reaction is completed, when the temperature inside the reactor drops to below 30°C, the hydrothermal products are transported to a solid-liquid separation device for solid-liquid separation. (6) The hydrothermal gas generated in the high-temperature hydrothermal reactor in step (5) is collected and stored with the hydrogen-rich gas in the fluidized bed in step (3). The hydrothermal gas product is used for the production of chemical raw materials or directly used as fuel. The mass ratio of the mixture of granulated steel slag and biochar to oily scum in the high-temperature hydrothermal reactor is 1: (30~50). The reaction conditions in the high-temperature hydrothermal reactor are: temperature 300~500℃, pressure 3~30Mpa, residence time 30~180min; (7) The solid material obtained by the solid-liquid separation device in step (5) includes steel slag, biochar and oil residue carbon, among which biochar and oil residue carbon have high calorific value. Due to the high temperature environment in the reactor and the catalytic and strong adsorption of steel slag and biochar, the oily scum is completely decomposed and transformed. Therefore, the hydrothermal liquid phase product obtained by separation is clear and free of impurities. After dehydration treatment, it is used as biofuel. (8) The solid product obtained in step (7) is transported to a fluidized bed boiler for use as fuel. The heat released during combustion is used for heating and power generation. The product after combustion is iron-rich ash slag, which is used as raw material for iron recovery or building material.

2. The method for treating oil-containing scum with liquid steel slag coupled with biomass according to claim 1, characterized in that, The design diameter of the porous rotating cup granulation device is 700~900mm, the height is 400~600mm, and the aperture of the rotating cup is 3~8mm.

3. The method for treating oily scum using liquid steel slag coupled with biomass according to claim 1, characterized in that, The original oily scum had a water content of 90-98% and a hydrothermal dehydration rate of 50-80%.

4. A system for treating oily scum using liquid steel slag coupled with biomass, employing the method described in claim 1, characterized in that... include: The system includes a liquid steel slag container, a porous rotating cup rotary granulation device, a rotary pyrolysis reactor, an oil-containing slag feeding device, a high-temperature hydrothermal reactor, a solid-liquid separation device, and a fluidized bed boiler. The outlet of the liquid steel slag container is connected to the inlet of the porous rotating cup rotary granulation device; the material outlet of the porous rotating cup rotary granulation device is connected to the material inlet of the rotary pyrolysis reactor; the material outlet of the rotary pyrolysis reactor is connected to the material inlet of the high-temperature hydrothermal reactor; the solid-liquid phase material outlet of the high-temperature hydrothermal reactor is connected to the material inlet of the solid-liquid separation device; and the solid phase outlet of the solid-liquid separation device is connected to the material inlet of the fluidized bed boiler.

5. A system for treating oily scum using liquid steel slag coupled with biomass, as described in claim 4, is characterized in that... The rotary pyrolysis reactor contains a biomass inlet, a steel slag inlet, a material outlet, and a gas outlet, achieving a complete pyrolysis reaction during rotation.

6. A system for treating oily scum using liquid steel slag coupled with biomass, as described in claim 4, is characterized in that... The high-temperature hydrothermal reactor is equipped with a feed inlet for conveying materials, a solid material outlet, a refined oil outlet, a heating device for regulating temperature, a pressure monitoring device, an endoscope inside the reactor, a magnetic float, and a pressure relief valve.

7. A system for treating oily scum using liquid steel slag coupled with biomass, as described in claim 4, is characterized in that... The solid-liquid separation device efficiently separates the products after the hydrothermal reaction, obtaining a mixture of steel slag, biochar, and oily slag hydrothermal char. The high-calorific-value biochar mixed with oily slag is directly usable. The resulting liquid product is high-quality biofuel, which is used for subsequent processing of chemical raw materials.

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