CN116374962A - Method for preparing acid by wet oxidation desulfurization of coke oven gas - Google Patents

Abstract

The invention discloses a method for preparing acid by wet oxidation desulfurization of coke oven gas. It comprises the following steps: step one, filtering sulfur foam generated by a wet oxidation desulfurization process of coke oven gas through liquid-solid separation equipment to obtain sulfur paste; refining the sulfur paste into liquid sulfur, and concentrating the supernatant into concentrated solution; and thirdly, burning the liquid sulfur and the concentrated solution to convert the liquid sulfur and the concentrated solution into sulfur dioxide, oxidizing the sulfur dioxide into sulfur trioxide, and finally producing sulfuric acid by dry absorption. The method solves the problems that in the prior art, a large amount of desulfurization waste liquid and sulfur foam are evaporated and concentrated or the energy consumption for sulfur foam drying treatment is high, a large amount of water is taken into an incinerator to consume coal gas, and a large amount of dilute acid is generated; the problems that sulfur or salt is burnt without being brought to the back due to operation or working condition fluctuation in burning, so that a waste heat boiler is blocked or the solid content of dilute acid is increased, and the running stability of the device is reduced are also solved.

Description

A method for producing acid by wet oxidation desulfurization of coke oven gas

technical field

The invention relates to the technical field of coke oven gas desulfurization and sulfur resource recovery and utilization, in particular to a method for producing acid by wet oxidation desulfurization of coke oven gas.

Background technique

Wet oxidation desulfurization technology has the advantages of high desulfurization efficiency and recoverable elemental sulfur. It is widely used in the field of desulfurization and purification of coke oven gas. The sulfur produced contains many impurities such as salt, tar, and coal powder, and is of low quality, making it difficult to effectively treat it. The traditional salt extraction process can eliminate the discharge of desulfurization waste liquid to a certain extent, but the energy consumption of salt extraction is high, and the market acceptance of salt extraction products is not high, and the low-quality sulfur produced by the system generally directly produces sulfur paste, which basically has no market demand And application, also caused certain environmental risks to the coking plant.

Desulfurization waste liquid and sulfur paste or sulfur foam can be used as raw materials to produce concentrated sulfuric acid. The purification section of the existing desulfurization waste liquid, sulfur paste or sulfur foam acid plant will produce a large amount of dilute sulfuric acid, which mainly comes from the pretreatment section. Moisture, the moisture entering the incinerator and the SO ₃ produced during incineration in the incinerator combine to form dilute sulfuric acid, which is condensed in the purification section. The dilute sulfuric acid produced is difficult to be fully utilized in the coking system, and part of the dilute sulfuric acid must be sent to the sewage treatment plant. In addition, the incineration section is complicated, and the proportion of sulfur and desulfurization waste liquid is not properly controlled, which will lead to incomplete incineration and blockage of the waste heat boiler behind; the incineration process requires a large amount of gas consumption and high energy consumption. At present, due to the use of HPF in the gas desulfurization at the front end of the acid plant, the molar ratio of elemental sulfur and sulfur-containing salt in the sulfur foam changes very low, and the concentration of the total sulfur element also changes greatly, resulting in the sulfur flow rate in the incineration of the acid plant. Large changes in the concentration of various sulfur and sulfides will inevitably affect the stable operation of the acid plant.

For example, patent application number 201810232542.X discloses a wet oxidation desulfurization waste liquid sulfuric acid production process and its device. The pretreatment equipment is severely corroded, the amount of dilute acid is large, the energy consumption is high, and the waste heat boiler is often blocked. Patent application number 201910434387.4 discloses a process for the preparation of acid from coke oven gas desulfurization waste liquid, which uses solid crude sulfur containing salt to incinerate directly, and the waste heat boiler is easy to block, resulting in a decrease in the operation stability of the device, and the energy consumption of pretreatment will be very high. Patent application number 202011210936.9 discloses a system and method for producing acid from desulfurization waste liquid. Dilute acid is used to generate ammonium salt with ammonia water, and then returned to the incinerator. The energy consumption is high, and it cannot solve the problems of serious corrosion of pretreatment equipment and blockage of waste heat boiler. Patent Application No. 202210587365.3 discloses a zero-emission method for desulfurization waste liquid and sulfur foam acid production. It uses solid crude sulfur containing salt to incinerate directly, and the waste heat boiler is easy to block, resulting in a decrease in the operation stability of the device, and the pretreatment energy consumption will be very high. .

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for producing acid by wet oxidative desulfurization of coke oven gas, so as to solve the problems in the prior art: the evaporation and concentration of a large amount of desulfurization waste liquid and sulfur foam or the high energy consumption of sulfur foam drying treatment , a large amount of water is brought into the incinerator to consume gas, and a large amount of dilute acid is produced at the same time; the ratio of sulfur, salt, and water to the concentrated material of sulfur foam changes, resulting in the incineration of sulfur or salt due to fluctuations in operation or working conditions. If it is brought into the back as much as possible, the waste heat boiler will be blocked or the solid content of dilute acid will increase, and the operation stability of the device will decrease. In order to overcome the deficiencies of the prior art, the invention provides a method for producing acid by wet oxidation desulfurization of coke oven gas.

To achieve the above object, the technical solution of the present invention comprises the following steps:

Step 1. Filtrating the sulfur foam produced by the wet oxidation desulfurization process of coke oven gas through liquid-solid separation equipment to obtain sulfur paste;

Step 2, refining the sulfur paste into liquid sulfur, and concentrating the supernatant produced at the same time into a concentrate;

Step 3: Incinerate liquid sulfur and concentrated liquid to convert it to sulfur dioxide, oxidize sulfur dioxide to sulfur trioxide, and finally dry-absorb to produce sulfuric acid.

The preferred technical solution of the present invention is: the wet oxidative desulfurization process is a complex iron oxidative desulfurization method; the second step is to make sulfur slurry from sulfur paste, and then transport the sulfur slurry to a sulfur melting kettle for sulfur melting Refining, the supernatant separated from the upper end of the sulfur melting kettle is evaporated and concentrated into a concentrated liquid, and the liquid sulfur is separated from the lower end of the sulfur melting kettle; the solid content of sulfur in the liquid sulfur in the second step is 5-25% wt; The liquid sulfur temperature in the sulfur melting kettle is controlled at 140°C-160°C; the salt content in the supernatant concentrated liquid is 50-60%wt of the concentrated liquid mass.

The preferred technical scheme of the present invention is: the incineration temperature of step 3 is 900°C-1050°C, and _the SO in the flue gas after incineration The mass percentage content is 10%-12.5%; After heating, the temperature drops to 320°C-350°C, and then cools down to 200°C-230°C by exchanging heat with the added air; the third step includes performing four-stage vanadium-based catalytic conversion of SO ₂ flue gas, and the purified SO _2. The flue gas, after being dried, is preheated to 420°C and enters the first-stage conversion. SO ₂ is oxidized to SO ₃ . After heat exchange to 170°C, it enters the first absorption; the gas after the first absorption enters the four-stage conversion after heat exchange to 420°C, and after the reaction, it enters the second absorption after heat exchange to 165°C; the dry absorption The moisture in the flue gas is absorbed by 94%wtH ₂ SO ₄ circulation to make the moisture content less than 0.1g/Nm3, and 98%wtH ₂ SO ₄ is used to absorb SO ₃ and convert it into sulfuric acid, and the 94% sulfuric acid produced after drying is sent to For the first absorption and the second absorption, the corresponding 98% sulfuric acid is returned from the absorption to the drying equipment; the third step includes tail gas absorption, and the tail gas absorption is to use waste ammonia to circulate and absorb sulfur oxides in the tail gas , add hydrogen peroxide to ensure that ammonium sulfite generates ammonium sulfate solution, and the exhaust gas after absorption is discharged after electrostatic demisting.

Compared with prior art, the beneficial effect of the present invention is:

(1) The present invention provides a method for making acid by wet oxidation and desulfurization of coke oven gas, which uses sulfur paste to prepare high solid content material to melt sulfur to obtain liquid sulfur, and can remove solid impurities such as coke slag entering the desulfurization system Separated to avoid clogging of rear nozzles or waste heat boiler etc.

(2) Refined liquid sulfur is used for incineration in the acid production process, which increases the concentration of elemental sulfur in the incineration material and reduces the production of dilute acid in the flue gas purification process.

(3) Using liquid sulfur incineration, the sulfur content of liquid sulfur is relatively fixed, which reduces the fluctuation of the amount of elemental sulfur in the incineration process, and can avoid fluctuations in operation and working conditions, which will cause the material to be not fully incinerated and brought into the subsequent process to affect the stable operation of the device, such as waste heat boilers clogging etc.

(4) For coke oven gas purification, the complex iron method is selected as the energy head to suppress the increase of auxiliary salts. The sulfur yield of the complex iron desulfurization method reaches 99%, which sharply reduces the proportion of auxiliary salts incinerated in acid production. Liquid sulfur is used for incineration, and no need Consuming coke oven gas to provide heat, greatly saving energy consumption.

Description of drawings

Fig. 1 Schematic flow chart of wet oxidative desulfurization of coke oven gas for producing acid.

Fig. 2 Schematic diagram of coke oven gas complex iron desulfurization and acid production process.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Figure 1, the coke oven gas wet oxidative desulfurization resource-based acid production method includes, in turn, a wet oxidative desulfurization unit that purifies sulfur-containing coke oven gas and converts hydrogen sulfide into elemental sulfur; The sulfur paste refining unit for refining the sulfur paste from solid separation into liquid sulfur and supernatant liquid concentrate, the incineration unit for incinerating liquid sulfur and supernatant liquid concentrate into SO ₂ flue gas, and the high temperature SO ₂ flue gas after incineration The heat recovery in the flue gas produces steam, the flue gas purification unit that removes the harmful components in the SO ₂ flue gas that are harmful to the subsequent conversion and generates dilute acid, and converts the purified and dried SO ₂ flue gas into SO ₃ under the catalysis of the vanadium catalyst The flue gas conversion unit, the dry absorption unit that absorbs the converted SO ₃ into sulfuric acid with concentrated sulfuric acid, and the tail gas absorption unit that absorbs waste ammonia water into ammonium sulfate solution.

Coke oven gas wet oxidative desulfurization unit, sequentially includes alkaline aqueous solution containing desulfurization catalyst lean liquid gas-liquid contact to transfer hydrogen sulfide in coke oven gas to desulfurization solution to be purified, sulfur foam and sulfur foam are formed in the rich liquid regeneration process Foam liquid-solid separation into sulfur paste. Different desulfurization catalysts are used in wet oxidation desulfurization, including PDS process, HPF process, improved ADA process, naphthoquinone disulfonic acid process, and complex iron process. Although the catalysts are different, the process routes are basically the same, and the absorption and regeneration equipment are also the same. The main reason is that the sulfur yield of the catalyst is different, and the sulfur yield of the complex iron method can reach up to 99%.

Sulfur paste refining unit includes sulfur paste and desulfurization liquid or supernatant to make sulfur slurry with elemental sulfur content of 5-25%wt, sulfur melting kettle liquid sulfur part control temperature 140-160℃ sulfur slurry melting sulfur, sulfur melting kettle The upper supernatant is concentrated so that the mixed salt content is 50-60%wt of the concentrated liquid mass.

The incineration unit is to incinerate the liquid sulfur and concentrated liquid from the refining of sulfur paste. The incineration temperature is 900°C-1050°C, and the SO ₂ content in the flue gas after incineration is 10%-12.5%. The boiler produces steam, the temperature drops to 300°C-350°C, and then it exchanges heat with the air that is incinerated to cool down to 200°C-230°C.

The cooled flue gas enters the purification unit, and the SO ₂ flue gas passes through the dilute acid cycle gas-liquid contact washing, the dilute acid cycle gas-liquid contact cooling and the electric demister in sequence; the cycle dilute acid is sprayed into the washing and atomized, and the SO ₂ The flue gas is in contact with the atomized dilute acid, and the _SO2 flue gas is humidified by evaporation of water. During cooling, dilute acid circulates in countercurrent contact, washes and purifies, removes impurities and steam, and then enters electric mist removal to remove acid mist and dust. The SO ₂ flue gas after electrostatic demisting is sprayed and dried with 94%wt sulfuric acid to reduce the moisture in the flue gas to below 0.1g/Nm3.

Since the oxidation of sulfur dioxide to sulfur trioxide is a reversible exothermic reaction, in order to increase the conversion rate as much as possible, the flue gas conversion unit and the flue gas dry absorption unit are connected in series alternately, and the dried SO ₂ flue gas is converted into SO ₃ under the action of a vanadium catalyst , and then spray 98% concentrated sulfuric acid to absorb SO ₃ to generate sulfuric acid and then enter the acid tank. The dried SO ₂ flue gas is first preheated to 420°C and enters the first-stage conversion. Under the action of the vanadium catalyst, SO ₂ is oxidized to SO3, and the heat is exchanged to 450°C. After entering the second-stage conversion reaction, the heat is exchanged to 430°C. Enter the three-stage transformation to continue the reaction. The reformed gas is heat-exchanged to 170°C for the first absorption; the gas after the first absorption is heat-exchanged to 420°C, and after entering the fourth-stage transformation, it is heat-exchanged to 165°C. secondary absorption. The tail gas treatment unit uses ammonia water to circulate and absorb the process tail gas sent from the second suction, and the SO ₂ , SO ₃ and sulfuric acid mist in the tail gas react with NH ₃ to form (NH ₄ ) ₂ SO ₃ and (NH ₄ ) ₂ SO ₄ absorption , and oxidize sulfite to sulfate with hydrogen peroxide.

With 170000Nm ³ /h coke oven gas, hydrogen sulfide content 6g/Nm ³ , wet oxidative desulfurization adopts HPF method, sulfur yield is 50%, 50% of sulfur is converted into secondary salt, and sulfur paste is made with a solid content of 5%wt 556kg/h of liquid sulfur is obtained after the sulfur slurry is melted, and the elemental sulfur content is 95%wt; the three-salt content in the desulfurization liquid is 250g/L, and 5 cubic meters of desulfurization waste liquid is produced per hour, which is vacuum concentrated at 90°C to a total salt concentration of 50 %wt, about 2 cubic meters per hour. Compared with the current spraying incineration process, the dilute acid in the purification process will be significantly reduced. More importantly, the fluctuation of elemental sulfur entering the incineration process per unit time will not be too large, ensuring the stability of the acid plant .

Example 2

As shown in Figure 2, the coke oven gas complex iron desulfurization resource-based acid production method, the complex iron desulfurization unit sequentially includes the sulfur-containing coke oven gas contacting the complex iron desulfurization poor solution to convert hydrogen sulfide into elemental sulfur Absorption, the absorbed complexed iron-rich liquid is in parallel contact with regeneration air to regenerate complexed ferrous iron into complexed iron and form sulfur foam regeneration, separate sulfur foam from liquid to solid to obtain sulfur paste and return to the system filtrate for sulfur foam filtration . The complexing iron-sulfur paste refining unit includes mixing sulfur paste and desulfurization liquid in turn to make sulfur paste pulping with a solid content of 25%wt sulfur paste, and the sulfur paste enters the sulfur melting process and is layered into a liquid sulfur layer (controlled at 140-160°C ) and the molten sulfur of the supernatant liquid layer, liquid sulfur buffering and storage, and vacuum concentration of the supernatant to a total salt content of 50-60% wt; the incineration unit burns the liquid sulfur and the supernatant liquid concentrate into _SO Gas, the incineration temperature is 900°C-1050°C, the SO ₂ content in the flue gas after incineration is 10%-12.5%; the waste heat recovery unit uses the heat generated by incineration to generate steam through the waste heat boiler, and the temperature drops to 300°C-350°C. The air entering the incineration is cooled to 200°C-230°C by heat exchange.

A flue gas purification unit that removes harmful components in the SO ₂ flue gas that are harmful to the subsequent conversion and produces dilute acid, a flue gas conversion unit that converts the purified and dried SO ₂ flue gas into SO ₃ under the catalysis of a vanadium catalyst, and converts The converted SO ₃ is absorbed by concentrated sulfuric acid and converted into a dry absorption unit for sulfuric acid, and the tail gas absorption unit for waste ammonia water is converted into an ammonium sulfate solution.

Coke oven gas wet oxidative desulfurization unit, sequentially includes alkaline aqueous solution containing desulfurization catalyst lean liquid gas-liquid contact to transfer hydrogen sulfide in coke oven gas to desulfurization solution to be purified, sulfur foam and sulfur foam are formed in the rich liquid regeneration process Foam liquid-solid separation into sulfur paste. Different desulfurization catalysts are used in wet oxidation desulfurization, including PDS process, HPF process, improved ADA process, naphthoquinone disulfonic acid process, and complex iron process. Although the catalysts are different, the process routes are basically the same, and the absorption and regeneration equipment are also the same. The main reason is that the sulfur yield of the catalyst is different, and the sulfur yield of the complex iron method can reach up to 99%.

Sulfur paste refining unit includes sulfur paste and desulfurization liquid or supernatant to make sulfur slurry with elemental sulfur content of 5-25%wt, sulfur melting kettle liquid sulfur part control temperature 140-160℃ sulfur slurry melting sulfur, sulfur melting kettle The upper supernatant is concentrated so that the mixed salt content is 50-60%wt of the concentrated liquid mass.

The incineration unit is to incinerate the liquid sulfur and concentrated liquid from the refining of sulfur paste. The incineration temperature is 900°C-1050°C, and the SO ₂ content in the flue gas after incineration is 10%-12.5%. The boiler produces steam, the temperature drops to 300°C-350°C, and then it exchanges heat with the air that is incinerated to cool down to 200°C-230°C.

The cooled flue gas enters the purification unit, and the SO2 flue gas is sequentially passed through the dilute acid cycle gas-liquid contact washing, the dilute acid cycle gas-liquid contact cooling and the electric demister; the cycle dilute acid is sprayed into the washing and atomized, and the _SO2 fume The gas is in contact with the atomized dilute acid, and the SO ₂ flue gas is humidified by water evaporation. During cooling, dilute acid circulates in countercurrent contact, washes and purifies, removes impurities and steam, and then enters electric mist removal to remove acid mist and dust. The SO ₂ flue gas after electrostatic demisting is sprayed and dried with 94%wt sulfuric acid to reduce the moisture in the flue gas to below 0.1g/Nm3.

Since the oxidation of sulfur dioxide to sulfur trioxide is a reversible exothermic reaction, in order to increase the conversion rate as much as possible, the flue gas conversion unit and the flue gas dry suction unit are connected in series alternately, and the dried SO2 flue gas is converted into SO ₃ under the action of a vanadium catalyst. Then spray 98% concentrated sulfuric acid to absorb SO3 to generate sulfuric acid and then enter the acid tank. The dried SO ₂ flue gas is first preheated to 420°C and enters the first-stage conversion. Under the action of the vanadium catalyst, SO ₂ is oxidized to SO ₃ , and the heat is exchanged to 450°C. After entering the second-stage conversion reaction, the heat is exchanged to 430°C , enter the three-stage transformation to continue the reaction, the reformed gas is heat-exchanged to 170°C for the first absorption; the gas after the first absorption is heat-exchanged to 420°C, enters the four-stage transformation and then heat-exchanges to 165°C, Second absorption.

With 170000Nm ³ /h coke oven gas, hydrogen sulfide content 6g/Nm ³ , wet oxidation desulfurization adopts GLT complex iron method, sulfur yield is 99%, 1% sulfur is converted into auxiliary salt, sulfur paste elemental sulfur content is 65% wt (others are desulfurization liquid, tar coke residue, etc.), the sulfur paste is made into a sulfur slurry with a solid content of 25%wt to obtain 1000kg/h liquid sulfur after melting sulfur, the elemental sulfur content is 95%wt, and the iron content is 0.014%wt. Contains ammonium thiosulfate, the content of ammonium thiocyanate is 0.83%wt, the content of ammonium sulfate is 0.50%wt, and the rest is hydrocarbon components; at the same time, 2.41 m3/hour of molten sulfur supernatant is produced, and the iron content is 1.2g/L. The total content of auxiliary salt is 250g/L, and it is concentrated in vacuum at 90°C to a total salt concentration of 60%wt, about 0.73 cubic meters per hour. Therefore, the raw material for acid incineration is mainly liquid sulfur. Compared with the current shotcrete incineration process, not only does it not need to consume coke oven gas for auxiliary combustion (saving 860 square meters of coke oven gas per hour, equivalent to 528 kg of standard coal), but also can produce The amount of steam generated by about 140.8 kg of standard coal can significantly reduce the energy consumption per ton of coke (equivalent to saving 668.8 kg of standard coal per hour), the amount of dilute acid in the process is extremely low, and more importantly, the elemental sulfur entering the incineration process per unit time is basically fixed , and the sulfur melting process separates various coke residues to ensure the stable operation of the acid plant. When the enterprise does not need sulfuric acid, it can directly produce 95%wt sulfur as the product.

Claims (8)

1. A method for making acid by wet oxidation desulfurization of coke oven gas, comprising the steps of: Step 1. Filtrating the sulfur foam produced by the wet oxidation desulfurization process of coke oven gas through liquid-solid separation equipment to obtain sulfur paste; Step 2, refining the sulfur paste into liquid sulfur, and concentrating the supernatant produced at the same time into a concentrate; Step 3: Incinerate liquid sulfur and concentrated liquid to convert it to sulfur dioxide, oxidize sulfur dioxide to sulfur trioxide, and finally dry-absorb to produce sulfuric acid. 2. A method for making acid by wet oxidative desulfurization of coke oven gas according to claim 1, characterized in that: said wet oxidative desulfurization process is complex iron oxidative desulfurization. 3. A method for making acid by wet oxidative desulfurization of coke oven gas according to claim 1, characterized in that: the second step is to make sulfur slurry from sulfur paste, and then transport the sulfur slurry to the sulfur melting kettle Sulfur melting is refined, the supernatant separated from the upper end of the sulfur melting kettle is evaporated and concentrated into a concentrated liquid, and liquid sulfur is separated from the lower end of the sulfur melting kettle. 4. A kind of method for coke oven gas wet oxidation desulfurization acid production according to claim 1, is characterized in that: the solid content rate of sulfur in the liquid sulfur in the described step 2 is 5-25%wt; The liquid sulfur temperature in the sulfur melting kettle is controlled at 140°C-160°C; the salt content in the supernatant concentrated liquid is 50-60%wt of the concentrated liquid mass. 5. A method for producing acid by wet oxidative desulfurization of coke oven gas according to claim 1, characterized in that: the incineration temperature of step 3 is 900°C-1050°C, and the mass of SO in the flue gas after incineration is ₁₀₀ %. The SO 2 content is 10%-12.5%; the SO ₂ flue gas produced by incineration is heated by the waste heat boiler, and the temperature drops to 320°C-350°C, and then it exchanges heat with the added air and cools down to 200°C-230°C. 6. The method for making acid by wet oxidative desulfurization of coke oven gas according to claim 1 or 5, characterized in that: said step 3 comprises carrying out SO ₂ flue gas to 4 stages of vanadium-based catalytic conversion, after purification The SO2 flue gas, after being dried, is preheated to 420°C and enters the first-stage conversion. SO ₂ is oxidized to SO ₃ . The gas is heat-exchanged to 170°C and enters the first absorption; the gas after the first absorption is heat-exchanged to 420°C and enters the four-stage conversion, and after the reaction, it is heat-exchanged to 165°C and enters the second absorption. 7. The method for making acid by wet oxidative desulfurization of coke oven gas according to claim 1, characterized in that: the dry suction is to use 94%wtH2SO4 to circulate and absorb the moisture in the flue gas so that the moisture content is lower than 0.1g/Nm3, use 98% _wtH2SO4 to circulate and absorb _SO3 into sulfuric acid, and the 94% sulfuric acid produced after drying will be sent to the first absorption and the second absorption, and at the same _time , the corresponding 98% sulfuric acid will be returned to the drying equipment from the absorption %sulfuric acid. 8. The method for making acid by wet oxidation desulfurization of coke oven gas according to claim 1, characterized in that: said step 3 includes tail gas absorption, and said tail gas absorption is to use waste ammonia water circulation to absorb the waste in the tail gas For sulfur oxides, hydrogen peroxide is added to ensure that ammonium sulfite generates ammonium sulfate solution, and the exhaust gas after absorption is discharged after electrostatic demisting.

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