METHOD FOR REDUCING THE AMOUNT OF TOTAL ORGANIC CARBON (TOC) IN WATER IN A WASTEWATER STREAM FROM A STEEL MILL IN A STEEL MILL

Abstract

METHODS FOR TREATING WATER WITH ACTIVATED CARBON POWDER TO REDUCE ORGANIC MATTER CONTENT. The present methods described reduce the amount of organic matter in water, including reducing the total amount of organic carbon in the water. The method includes adding activated carbon powder to the water; mixing the activated carbon powder in the water; and separating the activated carbon powder from the water. In addition, a method for reducing the glycol content in water containing glycols, and a method for reducing the glycol content in a wastewater stream in a steel mill containing glycols are described.

Description

1 / 11 Descriptive Report of the Invention Patent for "METHOD FOR REDUCING THE AMOUNT OF TOTAL ORGANIC CARBON (TOC) IN WATER IN A WASTEWATER STREAM FROM A STEEL MILL". CROSS-REFERENCE TO RELATED REQUEST

[0001] This application claims the benefit of the Northern Provisional Application. American Union No. 62 / 987.052, filed on March 9, 2020. BACKGROUND

[0002] Many manufacturing operations can result in periodic and / or premature accidental discharges of organics or organic-modified liquids, including, for example, hydraulic fluid, heat transfer fluids, and cooling fluids.

[0003] These fluids can be used in production operations for many different purposes. For example, steel and other metals can be processed into hot strips, or rolling mills that reduce a hot slab, ingot, or housing of a cast shape into thin coils, plates, rods, or other structural forms. A typical arrangement is a roughing mill, followed by finishing benches that continuously reduce the molten product to its desired dimensions, for end use or further processing in pickling lines, chilling mills, and annealing on cut-to-length lines. The forces required to reduce a molten product to thinner shapes necessitate roller supports with significant pressure requirements (>2000 psi / 95.76 kPa). These pressures are maintained with hydraulic fluids.

[0004] From a hydraulic perspective, many industrial machines are designed to operate with fire-resistant hydraulic fluids, particularly water-glycol type hydraulic fluids, due to the extremely high operating temperatures. Water-glycol fluids generally contain glycols and about 30 to 60% by weight of water (per Petition 870240108207, dated 12 / 18 / 2024, page 8 / 42 2 / 11 example, 30-50% by weight of water, or 30-40% by weight of water). Typical glycols used in such fluids include diethylene glycol, ethylene glycol, propylene glycol, and other polyalkylene glycols, or combinations thereof. For example, water glycol fluid may contain 20-60% by weight or 30-50% by weight of diethylene glycol, and / or 5-20% by weight or 10-15% by weight of other polyalkylene glycols.

[0005] Although water is an important part of such water-glycol type fluids, its presence can also create performance problems (issues) for the fluid. Water, for example, does not exhibit the lubricating film strength of mineral oil, or various synthetic base lubricant stocks, and thus tends to limit the maximum operating pressure of the hydraulic system.

[0006] The high water solubility of glycol-type fluids can present a variety of difficulties in an industrial environment, including, for example, adequate control of the discharge of wastewater from industrial plants and facilities. Local municipalities, as well as state and federal agencies, may monitor water leaving an industrial facility for contaminants such as phenol content, FOG (fats, oils, and greases), heavy metals, and CBOD (carbonaceous biological oxygen demand) and COD (chemical oxygen demand).

[0007] As noted above, water glycol-type fluids are widely used across various industrial and hydraulic operations, and tend to be applied under high pressures, to power various components or to circulate through operating equipment, to control operating temperature. As a result, leaks or other unintentional discharges of water glycol during industrial operations are not uncommon. For example, in a steel mill, hydraulic fluid may be applied at a pressure of 119.70 to 143.64 kPa (2,500 to 3,000 psi). At these high pressures, this can result Petition 870240108207, dated 12 / 18 / 2024, page 9 / 42 3 / 11 a leak of hundreds or thousands of gallons of hydraulic fluid entering the wastewater stream.

[0008] Glycol-type fluids that find their way into a wastewater stream are typically not removed during wastewater treatment methods and tend to contribute substantially to increasing CBOD and COD levels in the effluent stream. Increased CBOD and COD levels can result in significant changes to the biodiversity of the effluent stream. Although anaerobic bacteria can survive—and perhaps thrive (grow)—in the presence of glycol water, the rest of the ecosystem will be depleted when oxygen levels are decreased. As a result, many industrial operations are faced with treatment surcharges from their wastewater treatment facilities, or allow violations due to high CBOD levels.

[0009] To address this, industrial operations have attempted to implement methods to suppress the impact of unintentional glycol discharges. However, glycols are 100% soluble in water, and as such are difficult to remove from water streams because glycols do not float, cannot be filtered, and are generally non-reactive. To date, ultrafiltration and reverse osmosis have been the only measures believed to be effective in removing glycols from wastewater streams. However, these processes are expensive and cumbersome, requiring wastewater to be collected and diverted for biological wastewater treatment.

[0010] There is a need for a more efficient method to quickly remove glycol contaminants from wastewater streams without requiring off-site treatment. SUMMARY

[0011] According to one aspect of this invention, it has been found that activated carbon powder (PAC), previously believed to be ineffective Petition 870240108207, dated 12 / 18 / 2024, page 10 / 42 4 / 11 in the removal of glycols from water streams, can efficiently reduce contaminants associated with glycol from water streams. The water can be treated on-site (e.g., at a steel mill) without requiring the water to be collected and transferred to an off-site treatment location. This enables real-time assessment of elevated total organic carbon (TOC) treatment levels to ensure that industrial operations comply with government regulations regarding TOC levels.

[0012] In one aspect, this disclosure provides a method for reducing an amount of total organic carbon (TOC) in water containing 18.93 to 378.54 L (5 to 100 gallons) of glycol / 45.36 kg (100 lb) of TOC and more than 25 mg of TOC / L of water. The method includes adding powdered activated carbon to the water; mixing the powdered activated carbon into the water in such a manner that at least some of the glycols absorb into the powdered activated carbon; and separating the powdered activated carbon from the water. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The FIGURE is a graph illustrating the effectiveness of PAC in removing glycols (as measured by TOC), using varying concentrations of PAC in a laboratory test.

[0014] It should be noted that this figure is intended to illustrate the general characteristics of methods, with reference to certain exemplary embodiments of the invention, and in this way supplements the detailed description described below. DETAILED DESCRIPTION OF THE MODALITIES

[0015] As described herein, methods are provided for reducing the amount of organic matter in a water stream.

[0016] The amount of organic matter in a water stream can be measured using various parameters. CBOD is a measurement of oxygen depletion in water as a result of biological activity. Petition 870240108207, dated 12 / 18 / 2024, page 11 / 42 5 / 11 facilitated by the organic carbon content in the sample. Higher concentrations of organic matter provide more food for microbes, resulting in greater microbial activity and thus greater oxygen depletion. Regulatory bodies generally monitor organic contaminants in industrial wastewater by assessing CBOD. However, to monitor CBOD, the effluent must first be collected and sent to a treatment facility (which can take about 5 days), and the CBOD test itself requires a 5-day incubation period for the sample with microbes. Thus, a glycol leak may remain undetected for 10 days before the industrial facility first becomes aware of the problem.

[0017] Furthermore, due to the nature of the CBOD test, the test results have a large deviation standard, and measurements can vary as much as 80% to 160% from the actual CBOD. In order to ensure that the effluent streams are found to be in compliance with regulations, CBOD should be minimized as much as possible (preferably eliminated) in order to ensure that CBOD tests do not report violation levels of organic matter.

[0018] TOC is a related parameter for measuring organic matter, and it substantially enables immediate feedback on the amounts of organic matter in the waste stream. TOC provides a measure of the total amount of carbon in a sample, by determining the CO2 generation from an oxidation reaction. In other words, while CBOD measures oxygen demand, TOC measures the conversion of oxygen to CO2. TOC can be measured in real time, on-site, and with high precision. In a steel mill, for example, TOC levels can be monitored at different locations (e.g., caster, channel, fouling pit) on a periodic basis. To ensure immediate feedback, measurements can be Petition 870240108207, dated 12 / 18 / 2024, page 12 / 42 6 / 11 measurements taken every 5-10 minutes. Alternatively, the facility can continuously monitor TOC levels at one or more locations.

[0019] Because CBOD and TOC are related, either can be used to measure the organic content in the water stream according to the disclosed methods. However, TOC is preferable due to its ability to provide immediate feedback on glycol levels with relatively high accuracy.

[0020] In the disclosed embodiments of the methods, powdered activated carbon (PAC) is introduced into a water stream and contacted with the organic matter in the water stream in order to reduce the amount of organic matter in the water stream. The effectiveness of organic matter removal (particularly glycol) can be determined by monitoring CBOD or TOC. For simplicity, the following discussion refers to TOC monitoring, but CBOD measurements can also be used.

[0021] Activated carbon is a highly porous, high surface area adsorption material with a largely amorphous structure. It is composed primarily of carbon atoms linked by random cross-links. The randomized linkage creates a highly porous structure with numerous fissures, cracks, and voids between the carbon layers, resulting in a very large internal surface area.

[0022] Activated carbon may be in the form of powdered activated carbon (PAC), such as powder having a particle size of 80 mesh (177 µm) or smaller. For example, PAC may have a particle size of 100 mesh (149 µm) or smaller, 140 mesh (105 µm) or smaller, 200 mesh (74 µm) or smaller, 230 mesh (62 µm) or smaller, 270 mesh (53 µm) or smaller, or 325 mesh (44 µm) or smaller. PAC may be defined by a certain percentage of particles passing through a given mesh size (e.g., at least 65%), Petition 870240108207, dated 12 / 18 / 2024, p. 13 / 42 7 / 11 70%, 75%, 80%, 85%, 90%, 95%, 99%), or it can be defined by a series of mesh sizes (for example, the PAC in which 99% of the particles pass through 100 meshes, 95% pass through 200 meshes, and 90% pass through 325 meshes).

[0023] PAC particles may have an average pore size of, for example, 50 nm or less, such as 2 to 50 nm, 5 to 40 nm, 7.5 to 30 nm, or 10 to 20 nm. In addition, PAC particles may have an iodine value of 600 to 1100, or even more than 1100 (e.g., 1100-1500). The iodine value is an indicator of porosity and is defined, according to ASTM D4607-94, as milligrams of iodine absorbed per 1.0 g of carbon, when the iodine concentration of the filtrate is 0.02 mol / L.

[0024] The apparent density of PAC can vary from 352.41 to 560.61 kg / m3 (22 to 35 lb / ft3), as well as 400.46 to 496.58 kg / m3 (25 to 31 lb / ft3). For example, PAC can have an apparent density of 464.54 kg / m3 (29 lb / ft3).

[0025] In embodiments of the invention, PAC can be injected into the water stream, either in powder form or as a fluid paste. For example, PAC can be mixed with water in a batch tank to form a fluid paste containing 1.2 to 1200 g of PAC per liter of water (0.01 to 10 lbs of PAC per gallon of water). For example, the concentration of PAC in the fluid paste can be 3 to 600 g of PAC per liter of water (0.025 to 5 lbs of PAC per gallon of water), 6 to 240 g of PAC per liter of water (0.05 to 2 lbs of PAC per gallon of water), or 12 to 120 g of PAC per liter of water (0.1 to 1 lb of PAC per gallon of water). The fluid paste can be kept in the tank, i.e., pre-made or formed continuously and as needed. PAC can then be injected into the system (as a powder or as a fluid paste) in response to detected high levels of TOC. This process of injecting PAC in response to a TOC threshold (e.g., 20 or 30 ppm), Petition 870240108207, dated 12 / 18 / 2024, p. 14 / 42 8 / 11 can be automated or performed manually.

[0026] The effective dosage of PAC will depend on the levels of TOC. Treatment and dosage levels vary depending on the system configuration and allowable CBOD limitations. Depending on system dynamics, the feed rate can be between 3 and 6 kg of PAC per liter (25 and 50 lbs of PAC per gallon) of glycol. A total treatment amount of 4,536 to 453.6 kg (10 to 1,000 lbs) of PAC can be injected into the water stream for every 453.6 g (1 lb) of TOC introduced into the water stream. For example, 22.68 to 362.88 kg (50 to 800 lbs) of PAC, 90.72 to 181.44 kg (200 to 400 lbs) of PAC, 102.06 to 158.76 kg (225 to 350 lbs) of PAC, or 113.40 to 136.08 kg (250 to 300 lbs) of PAC can be added for every 454 g (1 lb) of COT. Depending on the TOC levels and the effluent flow rate, the PAC feed rate can be 2.27 to 9.07 kg / min (5 to 20 lb / min), 3.40 to 6.80 kg / min (7.5 to 15 lb / min), or 4.54 to 5.44 kg / min (10 to 12 lb / min).

[0027] In the case of a hydraulic fluid leak, glycol levels can range from 18.93 to 378.54 liters (5 to 100 gallons) of glycol / 45.36 kg (100 lb) of TOC (e.g., 75.71 to 189.27 liters (20 to 50 gallons) of glycol / 45.36 kg (100 lb) of TOC, or 113.56 to 151.42 liters (30 to 40 gallons) of glycol / 45.36 kg (100 lb) of TOC). The amount of fluid leaking into the system can depend on various factors, such as flow rate, and how long the leak progresses before being detected. For example, a leak could introduce 22.68 kg, 45.36 kg, 50 kg, 68.04 kg, 136.08 kg, 340.20 kg (50 lb, 100 lb, 150 lb, 300 lb, 750 lb), or more of TOC into the system. TOC levels at the time of treatment initiation may be lower if detected earlier (e.g., 30 or 50 mg TOC / L water), or they may be higher, such as 100 mg / L, 150 mg / L, 200 mg / L, 500 mg / L, or higher.

[0028] The average COT levels after 24 hours of treatment should ideally be lower than 25 mg / L, and preferably. Petition 870240108207, dated 12 / 18 / 2024, page 15 / 42 9 / 11 lower than 20 mg / L, or lower than 15 mg / L. Treatment may result in complete removal of TOC, or a decrease in the average amount of TOC during the course of 24 hours. For example, the detected amount may decrease by 50%, 60%, 80%, 90%, 95% or 99% during the course of treatment (e.g., within 24 hours of starting treatment).

[0029] The total amount of PAC treatment added relative to the glycol spilled into the system can be up to 11.98 kg of PAC / liter of glycol (100 lb of PAC / gallon of glycol), for example from 0.60 kg to 11.98 kg of PAC / liter of glycol (5 to 100 lb of PAC / gallon of glycol), from 2.40 kg to 10.78 kg of PAC / liter of glycol (20 to 90 lb of PAC / gallon of glycol), from 5.99 kg to 9.59 kg of PAC / liter of glycol (50 to 80 lb of PAC / gallon of glycol), or from 7.79 kg to 8.99 kg of PAC / liter of glycol (65 to 75 lb of PAC / gallon of glycol). For example, the amount of PAC introduced could be approximately 8.39 kg of PAC / liter of glycol (70 lb of PAC / gallon of glycol).

[0030] In some respects, in order to ensure sufficient interaction between the PAC and the glycols, the PAC may be left to mix with water containing organic matter (TOC) for a certain amount of time before being separated, such as for 1-5 minutes. For example, the PAC may be mixed in a stream of water containing organic matter (where the turbulent flow effectively mixes the PAC in the water stream) for at least 3 minutes, at least 5 minutes, at least 10 minutes, at least 30 minutes, or at least 60 minutes before being left to settle. Or the PAC may be mechanically mixed with water containing organic matter in a tank for any of these mixing times.

[0031] In the case of a steel plant, PAC can be added to the channel leading to the scale pit or other clarification systems. The PAC is sufficiently mixed with the wastewater. Petition 870240108207, dated 12 / 18 / 2024, page 16 / 42 10 / 11 in the channel, or other piping before the scale separation system, where it then settles along with the adsorbed glycols. In this case, mixing time refers to the amount of time the PAC spends in the channel, mixing chamber, or piping before reaching the scale pit or other devices where it is left to settle. The settled PAC / glycols are removed from the scale pit, settling tank, dissolved air flotation (DAF) device, or other separation device, along with the steel scale, and the clarified water can be recirculated.

[0032] PACs / glycols may remain in the fouling, which can be removed and recycled or disposed of by normal handling processes. EXAMPLE

[0033] The following test was performed to demonstrate the effectiveness of the disclosed methods, and particularly to confirm the effect of various PAC concentrations in the treatment of COT.

[0034] A control solution containing 108 ppm TOC (~318 ppm glycol) in water. The glycol product used was FR WG 300-D from American Chemical Technologies, Inc., and included 35-45 wt% diethylene glycol, 30-40 wt% water, 10-15 wt% polyalkylene glycol, 0-1 wt% morpholine, and 0-1 wt% diethanolamine. Test samples were prepared from the control solution by adding varying amounts of PAC, ranging from 1,000 ppm (0.1 wt%) to 10,000 ppm (1 wt%) PAC, and mixing the samples for 3-5 minutes. The samples were left to settle for approximately 20 minutes, and 50 mL of water were decanted from the top of each sample and analyzed using a Teledyne TOC analyzer. A minimal amount of PAC was included in the 50 mL aliquots due to settling; however, it is believed that any incidental amounts of PAC present in the samples did not affect the analysis. Petition 870240108207, dated 12 / 18 / 2024, page 17 / 42 11 / 11 of COT.

[0035] The results are summarized in the FIGURE. As shown, TOC levels decrease with increasing amounts of PAC. However, it becomes increasingly difficult to mitigate TOC levels below 30 ppm of TOC. This demonstrates that PAC must be dosed carefully in order to ensure that TOC levels remain below regulated limits (which may require less than 20 or 30 ppm of TOC).

[0036] As shown in the Example, it was surprisingly found that PAC is effective in reducing TOC (and CBOD) when properly allowed to mix with water containing organic matter. Using the disclosed methods, water can be treated on-site (e.g., at a steel mill or airport de-icing runoff) without requiring the water to be collected and transferred to an off-site treatment location. This enables real-time assessment and treatment of elevated amounts of organic matter (measured as TOC or CBOD) to ensure that industrial operations meet environmental regulations.

[0037] Although the invention has been described in conjunction with specific exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Consequently, exemplary embodiments of the invention as described herein are intended to be illustrative, not limiting. Changes can be made without departing from the spirit and scope of the invention. Petition 870240108207, dated 12 / 18 / 2024, page 18 / 42

Claims

1 / 3 CLAIMS 1. A method for reducing the amount of total organic carbon (TOC) in water in a wastewater stream from a steel mill, the water containing 18.93 to 378.54 L (5 to 100 gallons) of glycol / 45.36 kg (100 lb) of TOC and more than 25 mg of TOC / L of water, characterized in that it comprises: measuring the amount of TOC in the wastewater stream from a steel mill; and when the measured amount of TOC is greater than a predetermined limit: adding powdered activated carbon to the wastewater stream from a steel mill in an amount based on the measured amount of TOC in the wastewater stream from a steel mill; mixing the powdered activated carbon into the wastewater stream from a steel mill in such a way that at least some of the glycols absorb the powdered activated carbon; To separate the powdered activated carbon from the wastewater stream of a steel mill, and dispose of the powdered activated carbon along with the scale.

2. Method according to claim 1, characterized in that the powdered activated carbon is added to the water in the form of a fluid paste, comprising from 1.12 to 1198 g (0.01 to 10 lbs) of powdered activated carbon per liter (gallon) of water.

3. Method according to claim 1, characterized in that powdered activated carbon is added to the water, in an amount in the range of 50.4 to 1762 kg of powdered activated carbon per 1 kg of TOC (50 to 800 lbs of powdered activated carbon per 1 lb of TOC) in the water stream.

4. Method according to claim 1, characterized in that the activated carbon powder has an iodine value of at least 1100.

5. Method according to claim 1, characterized in that the activated carbon powder has an apparent density in the range of 352 g / L to 561 g / L (22 lb / ft3 to 35 lb / ft3).

6. Method according to claim 1, characterized in that the amount of TOC in the water is reduced by at least 50% within 24 hours, from when the powdered activated carbon is first added to the water.

7. Method according to claim 1, characterized in that the method is carried out until the amount of TOC in the water is reduced to 20 mg TOC / L in the water or less.

8. Method according to claim 1, characterized in that the glycols comprise polyalkylene glycols.

9. Method according to claim 1, characterized in that the glycols comprise at least one glycol selected from the group consisting of diethylene glycol, ethylene glycol and propylene glycol.

10. Method according to claim 1, characterized in that the water contains the glycols as a result of a glycol spill.

11. Method according to claim 10, characterized in that powdered activated carbon is added to the water in an amount in the range of 0.60 to 11.99 kg of powdered activated carbon per liter of glycol (5 to 100 lbs of powdered activated carbon per gallon of glycol) poured into the water.

12. Method according to claim 10, characterized in that powdered activated carbon is added to the water in an amount in the range of 2.40 to 10.78 kg of powdered activated carbon per liter of glycol (20 to 90 lbs of powdered activated carbon per gallon of glycol) poured into the water. Petition 870240108207, dated 12 / 18 / 2024, p. 20 / 42 3 / 3 13. Method according to claim 10, characterized in that powdered activated carbon is added to the water in an amount in the range of 5.99 to 9.59 kg of powdered activated carbon per liter of glycol (50 to 80 lbs of powdered activated carbon per gallon of glycol) poured into the water.

14. Method according to claim 10, characterized in that: the method further comprises measuring an amount of total organic carbon (TOC) in wastewater, and powdered activated carbon is added to the water when the measured amount of TOC is greater than a predetermined limit.

15. Method according to claim 14, characterized in that the predetermined limit is 30 mg of TOC / L water. Petition 870240108207, dated 12 / 18 / 2024, page 21 / 42

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