CN112645479A - Scaling retarding method for coal gasification black ash water system - Google Patents

Scaling retarding method for coal gasification black ash water system Download PDF

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CN112645479A
CN112645479A CN201910960466.9A CN201910960466A CN112645479A CN 112645479 A CN112645479 A CN 112645479A CN 201910960466 A CN201910960466 A CN 201910960466A CN 112645479 A CN112645479 A CN 112645479A
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contact
molybdate
tungstate
coal gasification
corrosion inhibitor
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CN112645479B (en
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谢文州
郦和生
秦会敏
楼琼慧
王洪英
张春原
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C02F1/56—Macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F2001/007—Processes including a sedimentation step
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/08—Corrosion inhibition
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents

Abstract

The invention relates to the field of industrial water treatment, in particular to a scaling retarding method for a coal gasification black ash water system. The method comprises the following steps: (1) carrying out first standing after first contact with cationic polyacrylamide to obtain a supernatant, wherein the dosage of the cationic polyacrylamide is 1-8 mg/L; (2) carrying out second contact on the supernatant and acid so that the total alkalinity of the solution obtained by the second contact is 120-180 mg/L; (3) and carrying out third contact on the solution obtained by the second contact and a corrosion inhibitor, wherein the corrosion inhibitor comprises molybdate and/or tungstate, and the adding amount of the corrosion inhibitor is 180-320 mg/L. The method can keep higher scale inhibition performance at high temperature, can effectively slow down the scaling phenomenon in the coal gasification black ash water system, and has no obvious corrosion problem, thereby obviously prolonging the running period of the device.

Description

Scaling retarding method for coal gasification black ash water system
Technical Field
The invention relates to the field of industrial water treatment, in particular to a scaling retarding method for a coal gasification black ash water system.
Background
The black ash water treatment process in the coal water slurry gasification process is an important link. The main points of the black grey water treatment are as follows: cooling black water, recovering heat, removing dissolved gas, separating slag from water and recycling water. Coarse slag discharged from the gasification furnace is fished out from a slag pool through a slag conveyor, and black water with a large amount of fine slag and dissolved harmful gas is subjected to flash evaporation to carry out slag-water separation and heat recovery. The black water after flash evaporation concentration enters a sedimentation tank, the grey water at the upper part of the sedimentation tank overflows into a grey water tank, and then is pumped into a system for recycling through a grey water pump and a feeding pump of a washing tower. The liquid-solid mixture at the lower part of the sedimentation tank passes through a filter press, ash and slag are sent out of the working section in the form of filter cakes, and the filtrate is circulated back to the sedimentation tank. To prevent the build-up of dissolved solids, a portion of the grey water is continuously discharged to a wastewater treatment section.
The black gray water has the following characteristics: (1) high suspended matter. 20mg/L-200mg/L of grey water suspended matter, more than 2000mg/L of black water suspended matter, and more than 4000mg/L in some cases; (2) the system temperature is high, and the temperature difference is large; (3) the high-temperature retention time is long. Staying at the temperature of more than 200 ℃ for about 30 min; (4) high hardness; (5) the operating pressure of the system can reach 6.5MPa, the pressure change is large, the flow rate change is also large, the pH value change is also large, the deposition and scaling tendency of each part in the system is different, and the deposition of fine slag and CaCO are difficult to control3Is performed.
Therefore, during the operation of the black and grey water system, suspended matter deposition, scaling and corrosion are easy to occur, and the long-period safe operation of the coal gasification device is influenced.
At present, the scale formation is inhibited by adding the grey water dispersing agent in China, and the research on the grey water scale inhibition dispersing agent is focused on the sulfonate copolymer and the compound of the sulfonate copolymer and phosphonate, hydrolyzed polymaleic anhydride and the like.
At present, the scale formation is inhibited by adding ash water dispersing agent in China. The Changzhou Zhongnan chemical industry Co., Ltd invented a grey water scale inhibition and dispersion agent (CN102320694A) which is composed of 60% -65% of multipolymer (acrylic acid-hydroxypropyl acrylate-2-methyl-2-acrylamide propanesulfonic acid), 5% -10% of corrosion inhibitor (imidazoline derivative), 7% -10% of phosphonate (hydroxy ethylidene diphosphonic acid) and 15% -20% of water. The gray water scale inhibition and dispersion agent (CN104151476A) invented by Yixing Xingsheng Baoyi chemical company Limited, comprises the following components in percentage by weight: 10-30% of acrylic acid, 10-25% of methyl acrylate, 10-25% of ethyl acrylate, 10-20% of hydroxypropyl acrylate and 10-20% of oxygen-free demineralized water.
However, the scale inhibition effect of the existing scale inhibition and dispersion agent is not satisfactory enough, and particularly the scale inhibition effect is poor in a high-temperature section, and the problem of on-site black ash water scaling is still serious.
Disclosure of Invention
The invention aims to solve the problem that the scale inhibition effect of the existing scale inhibitor is not good enough in the prior art, and provides a scale-retarding method for a coal gasification black ash water system. The method disclosed by the invention has a good scale inhibition effect on a coal gasification black ash water system which is difficult to treat.
In order to achieve the aim, the invention provides a scale reduction method for a coal gasification black ash water system, which comprises the following steps in the black ash water treatment process:
(1) carrying out first contact on coal gasification black grey water and cationic polyacrylamide, and then carrying out first standing to obtain a supernatant, wherein the dosage of the cationic polyacrylamide relative to the coal gasification black grey water is 1-8 mg/L;
(2) carrying out second contact on the supernatant and acid so that the total alkalinity of the solution obtained by the second contact is 120-180 mg/L;
(3) and carrying out third contact on the solution obtained by the second contact and a corrosion inhibitor, wherein the corrosion inhibitor comprises molybdate and/or tungstate, and the adding amount of the corrosion inhibitor is 180-320mg/L relative to the solution obtained by the second contact.
By using the method of the invention, higher scale inhibition performance can be maintained at high temperature, the scaling phenomenon in a coal gasification black ash water system can be effectively slowed down, and no obvious corrosion problem exists, thereby obviously prolonging the period of industrial operation.
Other features and advantages of the present invention will be described in the following detailed description.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a scale reducing method for a coal gasification black ash water system, which comprises the following steps in the black ash water treatment process:
(1) carrying out first contact on coal gasification black grey water and cationic polyacrylamide, and then carrying out first standing to obtain a supernatant, wherein the dosage of the cationic polyacrylamide relative to the coal gasification black grey water is 1-8 mg/L;
(2) carrying out second contact on the supernatant and acid so that the total alkalinity of the solution obtained by the second contact is 120-180 mg/L;
(3) and carrying out third contact on the solution obtained by the second contact and a corrosion inhibitor, wherein the corrosion inhibitor comprises molybdate and/or tungstate, and the adding amount of the corrosion inhibitor is 180-320mg/L relative to the solution obtained by the second contact.
In step (1), the dosage of the cationic polyacrylamide is preferably 2-6mg/L, more preferably 3-5 mg/L. The adding amount refers to the mg of cationic polyacrylamide added relative to 1L of coal gasification black grey water.
In the present invention, the term "cationic polyacrylamide" is in accordance with the conventional concept in the art and is commercially available. Various cationic polyacrylamides are available in the art for use in the present invention, preferably the cationic polyacrylamide has a cationicity of from 20% to 70%, more preferably from 30% to 60%, even more preferably from 40% to 50%. The testing method of the cationic degree can be carried out according to the conventional mode in the field, such as GB/T31246-2014.
In the step (1), the first contact is carried out under the condition of stirring, the stirring speed is 120-180r/min, and the stirring time is 2-5 min.
In the step (1), the time of the first standing may be 8 to 15min, preferably 8 to 12 min.
In step (2), the acid is preferably one or more of sulfuric acid, hydrochloric acid, and nitric acid.
In step (2), the concentration of the acid is not particularly limited, and it is sufficient that the desired end point of the total alkalinity can be achieved.
In the step (2), the amount of the acid is such that the total alkalinity of the solution obtained by the second contact is 180mg/L, preferably 140mg/L and 170 mg/L.
In the step (2), the second contact is performed under stirring, and the stirring conditions are not particularly limited, and the solution may be sufficiently mixed and the total alkalinity of the obtained solution may be stabilized.
In the step (3), the dosage of the corrosion inhibitor is preferably 200-300 mg/L. The addition amount refers to the mg amount of the corrosion inhibitor added relative to 1L of the solution obtained by the second contact.
In the step (3), the corrosion inhibitor may be only molybdate, or only tungstate, or molybdate and tungstate.
In step (3), preferably, the corrosion inhibitor is molybdate and tungstate. In order to further improve the corrosion inhibition effect, the weight ratio of the addition amount of the molybdate to the tungstate is more preferably 1 (0.6-0.9), and still more preferably 1 (0.7-0.8).
According to another particularly preferred embodiment of the invention, the corrosion inhibitor further comprises L-methionine sulfonate. In order to further improve the corrosion inhibition effect, more preferably, the molybdate, the tungstate and the L-methionine sulfonate are added in a weight ratio of 1: (0.4-0.8): (0.2-0.5), more preferably 1: (0.5-0.7): (0.3-0.4).
In the invention, the tungstate and the molybdate can be in an anhydrous state or contain crystal water, and the addition amount is calculated in an anhydrous state.
In the present invention, preferably, the molybdate is selected from one or more of anhydrous sodium molybdate, sodium molybdate dihydrate and potassium molybdate pentahydrate.
In the present invention, preferably, the tungstate is selected from one or more of anhydrous sodium tungstate, dihydrate sodium tungstate, and anhydrous potassium tungstate.
In the present invention, preferably, the L-methionine sulfonate is selected from sodium L-methionine sulfonate and/or potassium L-methionine sulfonate.
In step (3), preferably, the pressure of the third contact is 0.1 to 8 MPa. In the actual operation process, the pressure can be greatly changed, and the higher the temperature of the system is, the higher the pressure becomes, the initial pressure can be lower, but the pressure can reach more than 7MPa in some high-temperature sections. The method of the invention has better effect under various pressures.
In step (3), preferably, the temperature of the third contact is 10 to 300 ℃. In the actual operation process, the temperature can change greatly and can even reach more than 200 ℃ in some sections. Generally speaking, the existing scale inhibitors for black grey water are greatly influenced by temperature, the scale inhibition effect in a high-temperature working section is remarkably reduced, and the method can still exert good scale inhibition effect at the temperature of more than 200 ℃.
In step (3), preferably, the time of the third contact is 0.2 to 8 hours. In the actual operation process, the residence time of the materials is greatly different, and in some processes, the materials can stay for 30min at 200 ℃. In this case, it becomes particularly important to maintain the scale inhibition performance at high temperatures, and the method of the present invention has a good scale inhibition effect at high temperatures and can maintain a long residence time.
The method can treat the coal gasification black grey water with poor water quality and can achieve good scale inhibition effect. In particular, the method of the invention has a particularly significant effect on coal gasification black grey water having the following characteristics: the sum of the mass concentration and the total alkalinity of the calcium ions of the coal gasification black water is less than 1600mg/L, and the ratio of the mass concentration and the total alkalinity of the calcium ions is (0.7-1.5): 1, the suspended matters are less than 4000mg/L, and the good scale inhibition effect can be achieved.
By using the method of the invention, the scaling phenomenon in the coal gasification black ash water system can be effectively slowed down, and no obvious corrosion problem exists, so that the operation period of the device can be obviously prolonged.
The present invention will be described in detail below by way of examples.
In the following examples and comparative examples, the water quality of coal gasification black water used is shown in Table 1. In Table 1, Ca2+The concentration (mg/L) is measured by GB/T15452-2009; the total alkalinity (mg/L) is measured by GB/T15451-2006; cl-The concentration (mg/L) is determined by GB/T15453-2018; the method for measuring the concentration (SS, mg/L) of the solid suspended matter is GB 11901-89; total dissolved solids (TDS, mg/L) were determined by HJ/T51-1999.
TABLE 1
Item Ca2+(mg/L) Total alkalinity (mg/L) Cl-(mg/L) SS(mg/L) TDS(mg/L) pH
Index (I) 780 730 266.8 3672 2695 8.41
In the following examples and comparative examples, example A corresponds to an operation at 55 deg.C, example B corresponds to an operation at 120 deg.C, and example C corresponds to an operation at 230 deg.C. The following examples were performed by simulation in a laboratory, since sampling could not be performed in the high temperature section in the actual system.
Example 1A
(1) Adding 3mg of cationic polyacrylamide with the cationic degree of 40% into 1L of coal gasification black water, quickly stirring for 2min at the speed of 150r/min, then standing for 10min, and taking supernatant for later use;
(2) adding a sulfuric acid solution into the supernatant obtained in the step (1) until the total alkalinity of the obtained solution is 170 mg/L;
(3) adding the solution obtained in the step (2) into a high-temperature high-pressure reaction kettle, adding potassium molybdate pentahydrate, anhydrous potassium tungstate and L-methionine potassium sulfonate, wherein the adding amount of the potassium molybdate pentahydrate is 105mg/L, the adding amount of the anhydrous potassium tungstate is 53mg/L and the adding amount of the L-methionine potassium sulfonate is 42mg/L (the adding amount of the potassium molybdate pentahydrate, the anhydrous potassium tungstate and the L-methionine potassium sulfonate is 1: 0.5: 0.4 in weight ratio, and the total amount is 200mg/L) relative to the volume of the solution obtained in the step (2).
(4) Hanging a carbon steel test piece in a reaction kettle, sealing the reaction kettle, introducing air, operating at a constant temperature of 55 ℃ for 0.5h under the initial pressure of 3.5MPa, sampling and testing Ca2+Concentration and total alkalinity, and calculating the scale inhibition rate; the test pieces were treated to calculate the corrosion rate (mm/a) of the carbon steel. The results obtained are reported in table 2.
Example 1B
The procedure is as in example 1A, with the only modification that in step (4) the operation is carried out at 120 ℃ at constant temperature.
The obtained scale inhibition ratio and the corrosion rate of the carbon steel test piece are shown in table 2.
Example 1C
The procedure is as in example 1A, with the only modification that in step (4) the operation is carried out at a constant temperature of 230 ℃.
The obtained scale inhibition ratio and the corrosion rate of the carbon steel test piece are shown in table 2.
Examples 2A to 2C
(1) Adding 5mg/L of cationic polyacrylamide with a cationic degree of 50% into 1L of coal gasification black water, rapidly stirring for 2min at a speed of 150r/min, standing for 10min, and taking supernatant for later use;
(2) adding a hydrochloric acid solution into the supernatant obtained in the step (1) until the total alkalinity of the obtained solution is 150 mg/L;
(3) adding the solution obtained in the step (2) into a high-temperature high-pressure reaction kettle, adding anhydrous sodium molybdate, sodium tungstate dihydrate and L-methionine sodium sulfonate, wherein the adding amount of the anhydrous sodium molybdate is 128mg/L, the adding amount of the sodium tungstate dihydrate is 77mg/L and the adding amount of the L-methionine sodium sulfonate is 45mg/L (the weight ratio of the adding amounts of the anhydrous sodium molybdate, the sodium tungstate dihydrate and the L-methionine sodium sulfonate is 1: 0.6: 0.35, and the sum is 250mg/L) relative to the volume of the solution obtained in the step (2).
(4) A carbon steel test piece was hung in the reaction vessel, the reaction vessel was sealed, air was introduced, the initial pressure was 3.5MPa, the reaction vessel was operated at constant temperature for 0.5h at 55 ℃ (example 2A), 120 ℃ (example 2B) and 230 ℃ (example 2C), respectively, sampling was conducted and the scale inhibition rate was calculated, and the corrosion rate (mm/a) of the carbon steel test piece was measured, and the obtained results are shown in table 2.
Examples 3A to 3C
(1) Adding 4mg/L of cationic polyacrylamide with a cationic degree of 50% into 1L of coal gasification black water, rapidly stirring for 2min at a speed of 150r/min, standing for 10min, and taking supernatant for later use;
(2) adding a nitric acid solution into the supernatant obtained in the step (1) until the total alkalinity of the obtained solution is 140 mg/L;
(3) and (3) adding the solution obtained in the step (2) into a high-temperature high-pressure reaction kettle, adding sodium molybdate dihydrate, sodium tungstate dihydrate and sodium L-methionine sulfonate, wherein the adding amount of the sodium molybdate dihydrate is 150mg/L, the adding amount of the sodium tungstate dihydrate is 105mg/L and the adding amount of the sodium L-methionine sulfonate is 45mg/L (the adding amount of the sodium molybdate dihydrate, the sodium tungstate dihydrate and the sodium L-methionine sulfonate is 1: 0.7: 0.3 in weight ratio, and the total amount is 300 mg/L).
(4) A carbon steel test piece was hung in the reaction vessel, the reaction vessel was sealed, air was introduced, the initial pressure was 3.5MPa, the reaction vessel was operated at constant temperature for 0.5h at 55 ℃ (example 3A), 120 ℃ (example 3B) and 230 ℃ (example 3C), respectively, sampling was conducted and the scale inhibition rate was calculated, and the corrosion rate (mm/a) of the carbon steel test piece was measured, and the obtained results are shown in table 2.
Examples 4A to 4C
The method is carried out according to the manner of the examples 2A-2C, and the adding proportion (the total amount is unchanged) of the anhydrous sodium molybdate, the sodium tungstate dihydrate and the L-methionine sodium sulfonate is changed, specifically, the adding amount of the anhydrous sodium molybdate is 132mg/L, the adding amount of the sodium tungstate dihydrate is 53mg/L, and the adding amount of the L-methionine sodium sulfonate is 65mg/L (the adding amount of the anhydrous sodium molybdate, the sodium tungstate dihydrate and the L-methionine sodium sulfonate is 1: 0.4: 0.5 by weight).
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 4A), 120 deg.C (example 4B) and 230 deg.C (example 4C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 5A to 5C
The method is carried out according to the manner of the example 2A-2C, and the adding proportion (the total amount is unchanged) of the anhydrous sodium molybdate, the sodium tungstate dihydrate and the L-methionine sodium sulfonate is changed, specifically, the adding amount of the anhydrous sodium molybdate is 125mg/L, the adding amount of the sodium tungstate dihydrate is 100mg/L, and the adding amount of the L-methionine sodium sulfonate is 25mg/L (the adding amount of the anhydrous sodium molybdate, the sodium tungstate dihydrate and the L-methionine sodium sulfonate is 1: 0.8: 0.2 by weight).
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 5A), 120 deg.C (example 5B) and 230 deg.C (example 5C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 6A to 6C
The procedure of examples 2A-2C was followed, with the only modification that step (3) was changed to: adding the solution obtained in the step (2) into a high-temperature high-pressure reaction kettle, adding potassium molybdate pentahydrate and sodium tungstate dihydrate, wherein the adding amount of the potassium molybdate pentahydrate is 143mg/L and the adding amount of the sodium tungstate dihydrate is 107mg/L (the adding amount of the potassium molybdate pentahydrate and the sodium tungstate dihydrate is 1: 0.75 by weight, and the total adding amount is 250mg/L) relative to the volume of the solution obtained in the step (2).
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 6A), 120 deg.C (example 6B) and 230 deg.C (example 6C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 7A to 7C
The procedure of examples 2A-2C was followed, with the only modification that step (3) was changed to: and (3) adding the solution obtained in the step (2) into a high-temperature high-pressure reaction kettle, and adding anhydrous sodium molybdate, wherein the adding amount of the anhydrous sodium molybdate is 250mg/L relative to the volume of the solution obtained in the step (2).
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 7A), 120 deg.C (example 7B) and 230 deg.C (example 7C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 8A to 8C
The procedure of examples 2A-2C was followed, with the only modification that step (3) was changed to: and (3) adding the solution obtained in the step (2) into a high-temperature high-pressure reaction kettle, and adding anhydrous sodium tungstate, wherein the adding amount of the anhydrous sodium tungstate is 250mg/L relative to the volume of the solution obtained in the step (2).
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 8A), 120 deg.C (example 8B) and 230 deg.C (example 8C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 9A to 9C
The procedure is as in examples 2A-2C, with the only modification that, in step (2), the total alkalinity of the resulting solution is adjusted to 120 mg/L.
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 9A), 120 deg.C (example 9B) and 230 deg.C (example 9C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 10A to 10C
The procedure is as in examples 2A-2C, with the only modification that, in step (2), the total alkalinity of the resulting solution is adjusted to 180 mg/L.
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 10A), 120 deg.C (example 10B) and 230 deg.C (example 10C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 11A to 11C
The method is carried out in the manner of example 2A-2C, with the only change that the adding proportion of the anhydrous sodium molybdate, the sodium tungstate dihydrate and the L-methionine sodium sulfonate is kept unchanged, the total adding amount is changed to be 180mg/L, specifically, the adding amount of the anhydrous sodium molybdate is 92mg/L, the adding amount of the sodium tungstate dihydrate is 55mg/L, and the adding amount of the L-methionine sodium sulfonate is 33mg/L (the adding amount of the anhydrous sodium molybdate, the sodium tungstate dihydrate and the L-methionine sodium sulfonate is 1: 0.6: 0.35 by weight).
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 11A), 120 deg.C (example 11B) and 230 deg.C (example 11C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 12A to 12C
The method is carried out in the manner of example 2A-2C, with the only change that the adding proportion of the anhydrous sodium molybdate, the sodium tungstate dihydrate and the L-methionine sodium sulfonate is kept unchanged, the total adding amount is changed to 320mg/L, specifically, the adding amount of the anhydrous sodium molybdate is 164mg/L, the adding amount of the sodium tungstate dihydrate is 98mg/L, and the adding amount of the L-methionine sodium sulfonate is 58mg/L (the adding amount of the anhydrous sodium molybdate, the sodium tungstate dihydrate and the L-methionine sodium sulfonate is 1: 0.6: 0.35 by weight).
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 12A), 120 deg.C (example 12B) and 230 deg.C (example 12C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 13A to 13C
The procedure is as in examples 2A-2C, with the only modification that the cationic polyacrylamide is added at a concentration of 1 mg/L.
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 13A), 120 deg.C (example 13B) and 230 deg.C (example 13C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 14A to 14C
The procedure is as in examples 2A-2C, with the only modification that the cationic polyacrylamide is added at a concentration of 8 mg/L.
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 14A), 120 deg.C (example 14B) and 230 deg.C (example 14C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 15A to 15C
The procedure of examples 2A-2C was followed, with the only change that the cationic polyacrylamide had a degree of cationicity of 20%.
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 15A), 120 deg.C (example 15B) and 230 deg.C (example 15C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Examples 16A to 16C
The procedure of examples 2A-2C was followed, with the only change that the cationic polyacrylamide had a degree of cationicity of 70%.
The results are shown in Table 2, which were obtained by running the test pieces at constant temperature of 55 deg.C (example 16A), 120 deg.C (example 16B) and 230 deg.C (example 16C) for 0.5h, sampling and calculating the scale inhibition rate, and testing the corrosion rate (mm/a) of the carbon steel test piece.
Comparative examples 1A to 1C
The grey water scale inhibition and dispersion agent of Hezhou, Zhongnan chemical industry Co., Ltd is commercially available with the mark number of HS-09 and is marked as D1. The procedure is as in examples 2A-2C, except that step (2) is not performed, step (3) is changed to: adding the solution obtained in the step (1) into a high-temperature high-pressure reaction kettle, and adding 300mg/L of grey water scale inhibition and dispersion agent D1.
The sample was taken and the scale inhibition rate was calculated, and the corrosion rate (mm/a) of the test carbon steel coupon was measured, and the obtained results are shown in Table 2.
Comparative examples 2A-2C
A grey water scale inhibition and dispersion agent of Yixing Xinguang Baoyi chemical Co., Ltd is commercially available, and the mark is XGM-9 which is recorded as D2. The procedure is as in examples 2A-2C, except that step (2) is not performed, step (3) is changed to: adding the solution obtained in the step (1) into a high-temperature high-pressure reaction kettle, and adding 300mg/L of grey water scale inhibition and dispersion agent D2.
The sample was taken and the scale inhibition rate was calculated, and the corrosion rate (mm/a) of the test carbon steel coupon was measured, and the obtained results are shown in Table 2.
TABLE 2
Figure BDA0002228740850000131
As can be seen from Table 2, the method of the present invention has a scale inhibition rate of 90% or more, even 100% at 55 deg.C, and still has a high scale inhibition rate at 120 deg.C and 230 deg.C. In the comparative example, the scale inhibitor which is commercially available can achieve a good scale inhibition effect at 55 ℃, but the scale inhibition rate is remarkably reduced under the high-temperature working conditions of 120 ℃ and 230 ℃. The comparison among the embodiments shows that the specific parameters and the coordination thereof in the method of the invention can generate obvious influence on the scale inhibition effect, and the scale inhibition effect can be further improved and the corrosion phenomenon can be controlled by optimizing the specific parameters.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (10)

1. A scale reducing method for a coal gasification black ash water system comprises the following steps in the black ash water treatment process:
(1) carrying out first contact on coal gasification black grey water and cationic polyacrylamide, and then carrying out first standing to obtain a supernatant, wherein the dosage of the cationic polyacrylamide relative to the coal gasification black grey water is 1-8 mg/L;
(2) carrying out second contact on the supernatant and acid so that the total alkalinity of the solution obtained by the second contact is 120-180 mg/L;
(3) and carrying out third contact on the solution obtained by the second contact and a corrosion inhibitor, wherein the corrosion inhibitor comprises molybdate and/or tungstate, and the adding amount of the corrosion inhibitor is 180-320mg/L relative to the solution obtained by the second contact.
2. The fouling mitigation method of claim 1, wherein in step (1), the cationic polyacrylamide is added in an amount of 2-6 mg/L.
3. A fouling mitigation method according to claim 1 or 2, wherein said cationic polyacrylamide has a cationicity of 20-70%, more preferably 30-60%.
4. The method for mitigating fouling as set forth in claim 1, wherein in step (3), the amount of added corrosion inhibitor is 200-300 mg/L.
5. The fouling mitigation method of claim 1 or 4, wherein the corrosion inhibitor is a molybdate and a tungstate;
preferably, the weight ratio of the addition amount of the molybdate to the tungstate is 1 (0.6-0.9), and more preferably 1 (0.7-0.8).
6. The scale mitigation method of claim 1 or 4, wherein the molybdate is selected from one or more of anhydrous sodium molybdate, sodium molybdate dihydrate and potassium molybdate pentahydrate;
preferably, the tungstate is selected from one or more of anhydrous sodium tungstate, dihydrate sodium tungstate and anhydrous potassium tungstate.
7. The fouling mitigation method of claim 1 or 4, wherein the corrosion inhibitor further comprises L-methionine sulfonate;
preferably, the L-methionine sulfonate is selected from sodium L-methionine sulfonate and/or potassium L-methionine sulfonate.
8. The fouling mitigation method of claim 7, wherein the molybdate, tungstate and L-methionine sulfonate are added in a weight ratio of 1: (0.4-0.8): (0.2-0.5).
9. The fouling mitigation method of claim 1, wherein in step (3), the pressure of the third contact is 0.1-8MPa, the temperature of the third contact is 10-300 ℃, and the time of the third contact is 0.2-8 h.
10. The scale-slowing method according to claim 1, wherein the sum of the mass concentration and the total alkalinity of the coal gasification black water is less than 1600mg/L, and the ratio of the mass concentration and the total alkalinity of the calcium ions is (0.7-1.5): 1, the suspended substance is less than 4000 mg/L.
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