AU2020101311A4

AU2020101311A4 - A Reduction and Harmless Treatment Method of Steel Rolling Oily Sludge by SCWO Technology

Info

Publication number: AU2020101311A4
Application number: AU2020101311A
Authority: AU
Inventors: Liting GUO; Suqin LI; Lichong PENG; Lihua Wang
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2020-07-09
Filing date: 2020-07-09
Publication date: 2020-08-20
Anticipated expiration: 2028-07-09

Abstract

The invention relates to a reduction and harmless treatment method of steel rolling oily sludge by SCWO technologya method for reduction harmless treatment of steel rolling oily sludge by SCWO technology, which utilizes the special properties of water in SCWO state, and applies SCWO technology to harmless treatment and resource utilization of steel rolling oily sludge. Under specific pressure, temperature, time and peroxide multiple, water and sludge are infinitely miscible and react rapidly. The oily sludge of steel rolling is reduced by more than 99.68%, and the COD of effluent water is reduced from 25031mg/L to 78~80mg/L. The small molecular gas produced in the process is recycled and utilized. The volume of the residual solid product is only about 1.5% of the raw oily sludge, and the residual solid product is mainly composed of inorganic particles, of which the Fe element mainly exist in the form of magnetite and hematite, all of which have certain value of resource recovery and utilization. The results show that SCWO method can be used to disposal oily sludge from steel rolling to realize reduction, innocuity and resource utilization. Drawings of Descriptions Figure1I Figure 2 1/3

Description

Drawings of Descriptions

Figure1I

Figure 2

1/3

Descriptions

A Reduction and Harmless Treatment Method of Steel Rolling Oily Sludge by SCWO Technology

Technical Field

[0001] The invention belongs to the field of resources and environmental protection, and in particular relates to a reduction and harmless treatment method of steel rolling oily sludge by SCWO technology for steel rolling oily sludge reduction and harmless treatment by supercritical water oxidation (SCWO) treatment.

Background Technology

[0002] At present, sludge treatment technologies mainly include landfill, biology and incineration. Environmental pollution caused by landfill; biological treatment of sludge with higher oil content has a longer period and a lower removal rate. Incineration treatment of oily sludge is prone to secondary pollution and subsequent treatment is complicated. SCWO technology is widely used in municipal sludge treatment, but it has not been involved in steel rolling sludge.

Summary of the Invention

[0003] In order to solve the above problems, the invention provides a reduction and harmless treatment method of steel rolling oily sludge by SCWO technology with short treatment period and high removal rate.

[0004] The technical scheme of the invention is that a reduction and harmless treatment method of steel rolling oily sludge by SCWO technology specifically comprises the following steps:

[0005] Firstly, a certain amount of undiluted steel rolling oily sludge is put into a stirring reaction kettle and the top cover of the reaction kettle isfixed, the power switches of a temperature controller and a heater are turned on, then water in a waste water cup is pumped into the reaction kettle through a preheater by a double-plunger high-pressure pump, the water and the sludge are heated to a temperature of 400-440°C in the reaction kettle, the hydrogen peroxide in the

Descriptions

hydrogen peroxide cup is injected into the stirring reaction kettle by the double-plunger high-pressure pump at a pressure of 23-25MPa, The peroxide multiple is 100-300%, and the reaction time is 1-5min. After the reaction is finished, the liquid flowing out of the water outlet of the gas-liquid separator is collected and the COD value of the effluent is measured, and the gas is recovered at the gas phase outlet to obtain the remaining solid products for recovery and phase analysis.

[0006] Further, the gas includes carbon dioxide, water vapor, and nitrogen.

[0007] Furthermore, the volume of the residual solid product is only less than 1.5% of the

volume of oily sludge, and the residual solid product with sludge reduction of more than 98.5% is mainly composed of inorganic particles, wherein the Fe element in the solid slag phase mainly exists in the form of maghemite and hematite.

[0008] Further, the effluent COD is reduced from 25031mg/L to 78-80 mg/L.

[0009] According to the invention, the special property that water does not have in the supercritical state (the temperature and pressure of water rise to the critical point t = 374.3°Qp =

22.05MPa or more) is utilized: the water can be uniformly mixed with air, oxygen and some organic matters; if oxygen and organic matters are dissolved in the supercritical water at the same time, the organic matters can be rapidly oxidized into small molecular compounds such as carbon dioxide, water vapor, nitrogen and the like. Research results: it is found that under specific pressure, temperature, time and peroxide multiple, the oily sludge in steel rolling is reduced by about 98.5%, and the effluent COD is very small compared with the COD value as high as 25031mg/L before treatment. After the reaction, the effluent COD reaches 78-80 mg/L, the clarity is the same as tap water, and the organic matter in the oily sludge is basically completely decomposed. Therefore, SCWO technology can reduce the oily sludge in steel rolling and make it harmless in a short time. The small molecule gas generated in the process is recycled and utilized. The volume of residual solid products is only about 1.5% of the volume of oily sludge, and the residual solid products are mainly composed of inorganic particles, of which Fe elements mainly exist in the form of maghemite and hematite in the solid slag phase, which have certain resource recycling value. SCWO technology is applied to harmless treatment and

Descriptions

resource utilization of oily sludge from steel rolling to provide scientific basis and reference for engineering application of this technology.

[0010] The invention has the beneficial effects that due to the adoption of the technical scheme,

the steel rolling oily sludge treated by the method is reduced by about 98.5%, and the effluent COD is very small compared with the COD value as high as 25031mg/L before treatment, the effluent COD reaches about 78-80 mg/L after reaction, and the clarity is the same as tap water, so SCWO technology can realize harmless treatment of the steel rolling oily sludge in a short time. The small molecule gas generated in the process is recycled and utilized. The volume of residual solid products is only about 1.5% of the volume of oily sludge, and the residual solid products are mainly composed of inorganic particles, of which Fe elements mainly exist in the form of maghemite and hematite in the solid slag phase, which have certain resource recycling value. This shows that the SCWO method can be used to treat oily sludge from steel rolling to realize reduction and resource utilization.

Brief Description of Drawings

[0011] Fig. 1 is an SEM image of sludge that has not been treated by supercritical water oxidation.

[0012] Fig. 2 is an SEM image of sludge treated by supercritical water oxidation.

[0013] Fig. 3 is an XRD pattern of residual solids after supercritical water oxidation treatment.

[0014] Fig. 4 is a graph showing the variation of COD value of oily sludge from steel rolling with time under the conditions of temperature 440°C, pressure 25MPa and peroxide multiple 300%.

[0015] Fig. 5 is a weight loss diagram of sludge differential thermal analysis.

Detailed Description of the Preferred Embodiments

Descriptions

[0016] The technical scheme of the present invention will be further described below with reference to a specific Embodiment.

[0017] Embodiment 1:

[0018] Putting undiluted steel rolling oily sludge into a stirring reaction kettle and fixing the top cover of the reaction kettle, turning on the power switches of a temperature controller and a heater, then pumping water in a waste water cup into the reaction kettle through a preheater by a double-plunger high-pressure pump, heating the water and the sludge in the reaction kettle to a temperature of 400°C, and starting to inject hydrogen peroxide in the hydrogen peroxide cup into the stirring reaction kettle by a double-plunger high-pressure pump at a pressure of 23MPa, a peroxide multiple of 150%, and a reaction time of 1min. After the reaction is finished, the liquid flowing out of the water outlet of the gas-liquid separator is collected and the effluent COD value is measured, and the gas is recovered at the gas phase outlet to obtain the remaining solid products for recovery and phase analysis.

[0019] Embodiment 2:

[0020] Putting undiluted steel rolling oily sludge into a stirring reaction kettle and fixing the top cover of the reaction kettle, turning on the power switches of a temperature controller and a heater, then pumping water in a waste water cup into the reaction kettle through a preheater by a double-plunger high-pressure pump, heating the water and the sludge in the reaction kettle to 420°C, and starting to inject hydrogen peroxide in the hydrogen peroxide cup into the stirring reaction kettle by a double-plunger high-pressure pump, wherein the pressure is 24MPa, the peroxide multiple is 100%, and the reaction time is 2min. After the reaction is finished, the liquid flowing out of the water outlet of the gas-liquid separator is collected and the effluent COD value is measured, and the gas is recovered at the gas phase outlet to obtain the remaining solid products for recovery and phase analysis.

[0021] Embodiment 3:

[0022] The method comprises the following steps of: putting undiluted steel rolling oily sludge into a stirring reaction kettle, fixing the top cover of the reaction kettle, opening power switches

Descriptions

of a temperature controller and a heater, then pumping water in a waste water cup into the reaction kettle through a preheater by a double-plunger high-pressure pump, heating the water and the sludge to 440°C in the reaction kettle, and starting to inject hydrogen peroxide in the

hydrogen peroxide cup into the stirring reaction kettle by a double-plunger high-pressure pump at a pressure of 25MPa, a peroxide multiple of 300%, and a reaction time of 5 minutes. After the reaction is finished, the liquid flowing out of the water outlet of the gas-liquid separator is collected and the COD value of the effluent is measured. The removal rates reach 97.88% respectively. The gas is recovered at the gas phase outlet, and the remaining solid products are recovered and analyzed.

[0023] Embodiment 4:

[0024] The undiluted steel rolling oily sludge is put into a stirring reaction kettle and the top cover of the reaction kettle is fixed, the power switches of the temperature controller and the heater are turned on, then the water in the waste water cup is pumped into the reaction kettle through the preheater by the double plunger high pressure pump, the water and the sludge are heated to 430°C in the reaction kettle, the double plunger high pressure pump starts to inject the

hydrogen peroxide in the hydrogen peroxide cup into the stirring reaction kettle, the pressure is MPa, the peroxide multiple is 180%, and the reaction time is 3.5min. After the reaction is finished, the liquid flowing out of the water outlet of the gas-liquid separator is collected and the COD value of the effluent is measured, and the removal rates reach 97.88% respectively. The gas is recovered at the gas phase outlet, and the remaining solid products are recovered and analyzed for phase.

[0025] Embodiment 5:

[0026] Putting undiluted steel rolling oily sludge into a stirring reaction kettle and fixing the top cover of the reaction kettle, turning on the power switches of a temperature controller and a heater, then pumping water in a waste water cup into the reaction kettle through a preheater by a double-plunger high-pressure pump, heating the water and the sludge in the reaction kettle to 410°C, and starting to inject hydrogen peroxide in the hydrogen peroxide cup into the stirring

reaction kettle by a double-plunger high-pressure pump at a pressure of 23MPa, a peroxide

Descriptions

multiple of 200%, and a reaction time of 4min. After the reaction is finished, the liquid flowing out of the water outlet of the gas-liquid separator is collected and the COD value of the effluent is measured, and the removal rates reach 97.88% respectively. The gas is recovered at the gas phase outlet, and the remaining solid products are recovered and analyzed for phase.

[0027] As shown in figs. 1- 2: fig. 1 is an SEM image of sludge before reaction, and fig. 2 is an SEM image of sludge after reaction; the surface of oily sludge before treatment is flocculent and viscous. The remaining solids after treatment are basically loose small particles with a size of less than 25[m, mainly silt and metal salts, which do not flow out with the reaction liquid, achieving good separation and stabilization of metal ions, and obvious removal effect of organic matters. The effluent is clear and transparent, the stench disappears, and harmless treatment is realized. Using supercritical water oxidation technology to treat oily sludge from steel rolling not only can realize harmless treatment, but also has very significant effect on sludge reduction. The volume of residual solid products is only about 1.5% of the volume of oily sludge, which achieves the purpose of reduction. Compared with landfill and fertilizer production, pathogenic microorganisms, parasites and malodorous odor existing in sludge disappear, and dioxin toxic substances generated in incineration process do not exist. The residual solid iron content treated by SCWO technology is high. As shown in Figure 3, the residual solid mainly consists of maghemite, calcium sulfate, silicon dioxide, hematite, sodium phosphohydrogenite and sphalerite, etc. Among them, Fe element mainly exists in the form of maghemite and hematite in the solid slag phase, which has the potential of resource utilization and can be further purified to realize resource utilization. In a word, SCWO method not only has the advantages of fast reaction, simple operation and environmental friendliness, but also achieves reduction, harmlessness and resource utilization.

[0028] Analysis of the residual solid components after treatment is as follows:

[0029] Table 1 Composition of Residual Solids

[0030] Component Fe2O3 S03 SiO2 Na20 CaO ZnO A1203 P205 MgO Content(%) 33.23 22.87 13.52 9.44 7.76 4.37 3.44 1.81 1.14

Descriptions

[0031] The iron content is high and has the value of resource utilization.

Claims

1. The invention relates to a reduction and harmless treatment method of oily sludge from steel rolling by SCWO technology, which is characterized in that the scheme specifically comprises the following steps:

Firstly, a certain amount of undiluted steel rolling oily sludge is put into a stirring reaction kettle and the top cover of the reaction kettle is fixed, the power switches of a temperature controller and a heater are turned on, then water in a waste water cup is pumped into the reaction kettle through a preheater by a double-plunger high-pressure pump, the water and the sludge are heated to 400-440 °Cin the reaction kettle, the hydrogen peroxide in the hydrogen peroxide cup is

injected into the stirring reaction kettle by the double-plunger high-pressure pump, and the pressure is increased to 23-25MPa. The peroxide multiple is 100-300%, and the reaction time is 1-5min. After the reaction is finished, the liquid flowing out of the water outlet of the gas-liquid separator is collected and the COD value of the effluent is measured, and the gas is recovered at the gas phase outlet to obtain the remaining solid products for recovery and phase analysis.

2. The method according to claim 1, characterized in that the volume of the residual solid product is only less than 1.5% of the volume of oily sludge, and the residual solid product with sludge reduction of more than 98.5% is mainly composed of inorganic particles, wherein the Fe element is mainly present in the solid slag phase in the form of maghemite and hematite.

3. The method according to claim 1, characterized in that the effluent COD is reduced from 25031mg/L to 78-80 mg/L.