Tail gas treatment optimization process for producing anhydrous calcium chloride from distilled ammonia waste liquid

Abstract

The invention discloses a tail gas treatment optimization process for producing anhydrous calcium chloride from distilled ammonia waste liquid, and relates to the technical field of tail gas treatment for producing anhydrous calcium chloride, and the tail gas treatment optimization process comprises an anhydrous calcium chloride production process and a tail gas treatment process. The hot blast stove heats the tail gas, the heated tail gas is subjected to denitration treatment through the denitration ejector, the waste gas subjected to denitration treatment is conveyed to the smoke exhaust flue through the induced draft fan, the dry-method desulfurization ejector is arranged in the smoke exhaust flue, and after the waste gas is subjected to desulfurization treatment through the dry-method desulfurization ejector in the smoke exhaust flue, the waste gas is conveyed to the hot blast stove. And the dust is removed by the bag-type dust remover and then discharged to a discharge The device has the beneficial effects that the structure is simple, the tail gas treatment efficiency is greatly improved, the qualified standard of the tail gas can be reached by adopting a small amount of desulfurization and denitrification agent in a short time, and the sulfur content in the tail gas is stable and is not influenced by the change of the sulfur content of an inlet.

Description

Technical Field

[0001] The invention relates to the technical field of tail gas treatment in the production of anhydrous calcium chloride, and in particular to an optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid. Background Art

[0002] After the ammonia waste liquid is clarified, the surface clear liquid is transported to the drying pool for natural evaporation. The effective concentration is increased by drying in multiple drying pools for natural evaporation. The concentration of the ammonia waste liquid is increased after drying. The ammonia waste liquid is pumped to the multi-effect evaporation surface condenser through a circulating pump for circulating cooling and condensation. At the same time, a part of the original liquid is added to the first-effect separation chamber by a liquid inlet pump for evaporation and concentration. At this time, sodium chloride is saturated and separated to precipitate fine sodium chloride crystals, and the waste salt is removed by high-speed centrifugation in a centrifuge; the desalted finished liquid is transported to the granulation line washing pool, and the waste heat generated when the sulfurized bed produces calcium chloride is used to increase the concentration of the finished liquid in the washing pool; anhydrous calcium chloride is obtained by spray granulation.

[0003] Waste gas is generated in the recovery of ammonia waste liquid, and the waste gas includes impurities such as water vapor, sulfide and nitrate. Since water vapor is mixed with sulfide and nitrate, the waste gas treatment is relatively cumbersome. For the waste gas generated by the anhydrous calcium chloride production process, the existing treatment is through water curtain dust removal and desulfurization with ammonia waste liquid, which requires a large amount of water and produces wastewater. The cost of tail gas treatment is high and the efficiency is not ideal. The desulfurization process desulfurizer (lime) is very easy to generate dust and other secondary environmental pollution during the desulfurization process. The tail gas is also treated by desulfurizer and denitrifier, among which the amount of desulfurizer and denitrifier used is large, and the sulfur and nitrogen contents of the treated waste gas are unstable, and the dust removal effect is not obvious. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides an optimized process for treating tail gas from the production of anhydrous calcium chloride using ammonia waste liquid to solve the above-mentioned technical problems.

[0005] The invention provides an optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid, comprising an anhydrous calcium chloride production process and a tail gas treatment process. The anhydrous calcium chloride production is to obtain anhydrous calcium chloride from ammonia waste liquid through the processes of airing, three-effect evaporation and spray granulation. The tail gas treatment process treats tail gas generated during the spray granulation. The tail gas generated by the spray granulation is transported to a hot blast furnace through a pipeline. The hot blast furnace heats the tail gas. The heated tail gas is denitrated by a denitration ejector. The denitration-treated waste gas is transported to a smoke exhaust duct through an induced draft fan. A dry desulfurization ejector is arranged in the smoke exhaust duct. After the waste gas is desulfurized by the dry desulfurization ejector in the smoke exhaust duct, it is discharged to the exhaust duct after dust removal by a bag dust collector.

[0006] The equipment of the exhaust gas treatment optimization process includes a hot blast furnace, a desulfurization ejector, an induced draft fan, an exhaust duct, a dry desulfurization ejector and a bag-type dust collector. The desulfurization ejector is arranged on the inner wall of the furnace of the hot blast furnace. The hot blast furnace is connected to the induced draft fan through a smoke duct. The induced draft fan is connected to the bag-type dust collector through the exhaust duct. The dry desulfurization ejector is arranged in the exhaust duct. The rear end of the bag-type dust collector is connected to the exhaust duct.

[0007] The dry desulfurization injector is spirally extended and arranged in the smoke exhaust duct for desulfurization treatment; the SNCR denitrification injector is spirally extended and arranged in the furnace of the hot blast furnace for denitrification treatment; a plurality of the dry desulfurization injectors and a plurality of the SNCR denitrification injectors are spirally extended and arranged, the spraying is uniform, the denitrification and desulfurization are rapid, the material consumption will be greatly reduced, and the desulfurization and denitrification efficiency is higher.

[0008] The dry desulfurization injector uses sodium bicarbonate as a desulfurization agent; the SNCR denitrification injector uses urea solution as a denitrification agent.

[0009] The sodium bicarbonate desulfurizer is sprayed into the dry desulfurization injector after being ground. The sodium bicarbonate fine powder is sprayed into the reactor to react rapidly with pollutants in the flue gas to generate active sodium carbonate with high specific surface area and high porosity. The active sodium carbonate reacts with SO2 in the flue gas and other acidic gases in the flue gas.

[0010] The main reactions are as follows:

[0011]

[0012] Na2CO3+2HCl→2NaCl+H2O+CO2

[0013] Na2CO3+2HF→2NaF+H2O+CO2

[0014] The property of sodium bicarbonate to be converted into "active sodium carbonate" makes it a good acid neutralizer (HCl, SO2, HF, etc.) and absorbent for heavy metals, dioxins and furans.

[0015] The sodium bicarbonate desulfurizer has a purity greater than 98%, a particle size of 0.1-2 mm, a humidity less than 1%, and a reaction temperature greater than 140°C.

[0016] The urea denitrification agent has a nitrogen content greater than 46%, a ratio concentration of 8%, and a reaction temperature between 800°C and 1200°C.

[0017] The bag dust collector is a negative pressure bag dust collector.

[0018] The injection amount of the desulfurizer is adjusted according to the SO2 concentration in the flue gas, and is synchronously adjusted in combination with the SO2 concentration fluctuation caused by the regular operation of the hot blast furnace.

[0019] Denitrification principle: Denitrification is simply to atomize urea solution and spray it into the furnace to remove nitric oxide and nitrogen dioxide from the flue gas and turn it into nitrogen that is harmless to the air.

[0020] SNCR denitrification process: SNCR technology, namely selective non-catalytic reduction technology, is one of the main flue gas denitrification technologies at present. In the narrow temperature range of 800-1250℃ in the furnace, without the action of catalyst, amino reducing agents such as NH3 or urea can selectively reduce NOx in the flue gas, and basically do not react with O2 in the flue gas. Based on this, SNCR flue gas denitrification technology was developed. In the range of 800-1250℃, the main reactions of NH3 or urea reducing NOx are:

[0021] Urea as reducing agent

[0022]

[0023] Different reducing agents have different reaction temperature ranges, which are within the range of 800-1250℃, and this temperature range is called the temperature window. When the reaction temperature is too high, the decomposition of ammonia will reduce the NOx reduction rate. On the other hand, when the reaction temperature is too low, the escape of ammonia will increase, which will also reduce the NOx reduction rate. The key to the SNCR process technology is that the reducing agent injection system must spray the reducing agent into the most effective temperature window area in the furnace as much as possible, that is, to ensure that the injected reducing agent is well mixed with the flue gas at a suitable temperature as much as possible, so that on the one hand, the utilization rate of the reducing agent can be improved, and on the other hand, the ammonia escape can be controlled to obtain a smaller value.

[0024] Composition of denitrification equipment: This set of denitrification equipment includes urea solution preparation system (mixing tank), denitrification metering pump station system (metering pump, pressure gauge, pipe valve, base, electric control box) denitrification spray gun (nozzle, gun rod, protective sleeve, mixer, quick connector, quick release clip, etc.).

[0025] Urea solution preparation system: The advantages of urea solution as a denitrification reducing agent are clean, sanitary and safe. In winter, it is usually prepared at a concentration of 10%. In summer, it can be prepared at a higher concentration of 15-20%, and the flow of the metering pump can be reduced accordingly. In the case of a relatively large load on the hot air furnace, a higher concentration can be prepared. Urea can be made of agricultural urea granules, and it is better to choose high-quality urea with a standard nitrogen content. Urea granules absorb a lot of heat when dissolving, so when preparing urea solution, try to use hot water or pass steam to prevent urea solution from crystallizing and blocking the pipeline or spray gun at low temperatures. Softened water or demineralized water should be used to prepare urea solution to prevent crystallization and scaling from clogging the nozzle. The liquid level of the mixing tank and storage tank should be checked frequently, and the preparation should be timely to prevent the transfer pump and metering pump from running without water. After the urea transfer pump has pumped the solution from the mixing tank, an appropriate amount of clean water should be added to the mixing tank and continued to pump it into the storage tank. The purpose is to clean the transfer pump and prevent urea from crystallizing in the pump's mechanical seal.

[0026] Denitrification metering system: The denitrification metering system is the core equipment of SNCR denitrification. Its main function is to accurately measure the flow rate of urea solution. The urea solution delivery booster pump provides pressure for the pipeline system to meet the lift requirements. The pressure is usually set to 0.4-0.5MPa.

[0027] DeNOx distribution module: The distribution module is mainly used to provide urea solution and compressed air for the deNOx spray gun, and to adjust and maintain uniform flow and pressure; each group of distribution modules is divided into two parts: urea solution and compressed air, and a main switch (first-level adjustment of pressure and flow) is set respectively. The urea solution distribution group also includes a ball valve regulating valve and a stainless steel pressure gauge; the compressed air distribution group is equipped with a compressed air regulating valve (with its own pressure gauge); the ball valve and compressed air regulation belong to the second-level regulation; the pressure of urea solution is usually adjusted to 0.3-0.5MPa, and the pressure of compressed air is usually adjusted to 0.3-0.5MPa; each group of distribution modules in each furnace must maintain the same pressure; if abnormal pressure occurs, check whether each valve or spray gun is blocked; the joints of the distribution modules are quick joints, and they must be checked regularly for looseness, dripping, and air leakage, and tightened in time.

[0028] Denitrification spray gun: The denitrification spray gun is the core component of SNCR denitrification; the spray gun is a dual-fluid spray gun, the compressed air inlet is at the end of the gun, and the urea solution inlet is in the direction perpendicular to the gun barrel. Usually, it is necessary to ensure that the inlet of the urea solution is vertically upward (so as to ensure that the fan-shaped mist sprayed from the nozzle is horizontal); the nozzle of the spray gun is made of 310SS, which is resistant to high temperature and friction. The nozzle is usually 2-5 cm away from the furnace wall. When installing, remember that it cannot be retracted into the furnace wall or coke, and it cannot be extended into the furnace too long; there is a positioning screw on the spray gun to determine the depth of the spray gun insertion. It must be kept tightened and cannot be loosened at will; the spray gun is an easy-to-remove quick clamp. In order to keep the spray fan horizontal, adjust the urea inlet vertically upward and tighten the clamp in time; when the spray gun is not in use, loosen the quick check street in time, open the clamp, and take out the spray gun. Prevent the spray gun from dry burning in the furnace; when the urea solution pressure exceeds the set pressure, take out the spray gun, check whether the urea solution inlet of the nozzle and the mixer is blocked, and use a needle to clean out impurities and dirt; the spray gun should be taken out at least once a week to check the atomization situation, observe whether there is coking, damage, blockage and other phenomena that affect the atomization effect, and deal with them in time.

[0029] Denitrification process operation flow: turn on the main power switch; fill the mixing tank with water, add urea, and start the mixing motor; dissolve the urea and let it stand for 1-2 hours to make sure that the urea is completely dissolved and no particles remain; start the transfer pump and pump the urea solution into the storage tank; prepare another mixing tank and pump it into the storage tank; turn on the compressed air switch and the compressed air switches on the distribution module (note that the compressed air must be turned on first); make sure that the pump station inlet is unobstructed, make sure that the urea solution switch on the distribution module is turned on, and start the delivery booster pump; observe and adjust the pressure of the urea solution and compressed air to the set value; when it is determined that the atomization effect of each spray gun is ideal, insert the spray gun into the furnace; when the denitrification system is out of use, first turn off the metering pump, use up the residual urea solution in the pipeline, and then turn off the compressed air; take out the spray gun.

[0030] The beneficial effects of the present invention are: simple structure, greatly improved exhaust gas treatment efficiency, and the ability to meet exhaust gas standards in a short period of time using a small amount of desulfurization and denitrification agents, and the sulfur content in the exhaust gas is stable and is not affected by changes in imported sulfur content, and the dust removal efficiency is significantly improved, so that the exhaust gas is discharged up to standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a diagram of the optimized process equipment for tail gas treatment of the present invention;

[0032] Figure 2 The process flow chart of producing anhydrous calcium chloride of the present invention;

[0033] Figure 3 This is a graph of existing process detection data of Example 2 of the present invention;

[0034] Figure 4This is a diagram of the optimized process detection data of Example 2 of the present invention;

[0035] In the figure: 1. hot air furnace; 2. desulfurization ejector; 3. induced draft fan; 4. exhaust flue; 5. dry desulfurization ejector; 6. bag filter; 7. exhaust flue. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figure 1-2 As shown, the present invention provides an optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid, including an anhydrous calcium chloride production process and a tail gas treatment process. The anhydrous calcium chloride production is to air the ammonia waste liquid through an airing pool to obtain a calcium chloride solution, and then to perform triple-effect evaporation, centrifuge to remove salt and obtain a concentrated calcium chloride solution. The concentrated calcium chloride solution is subjected to a spray granulation process to obtain anhydrous spherical calcium chloride. Waste gas is generated during the production process, and the waste gas contains sulfide and nitrate, which cannot be discharged directly and needs to be treated by a tail gas treatment process.

[0039] The equipment of the exhaust gas treatment optimization process includes a hot blast furnace, a desulfurization ejector, an induced draft fan, an exhaust duct, a dry desulfurization ejector and a bag-type dust collector. The desulfurization ejector is arranged on the inner wall of the furnace of the hot blast furnace. The hot blast furnace is connected to the induced draft fan through a smoke duct. The induced draft fan is connected to the bag-type dust collector through the exhaust duct. The dry desulfurization ejector is arranged in the exhaust duct. The rear end of the bag-type dust collector is connected to the exhaust duct.

[0040] The tail gas treatment process treats the tail gas generated during the spray granulation. The tail gas generated by the spray granulation is transported to a hot blast furnace through a pipeline. The hot blast furnace heats the tail gas. The heated tail gas is denitrated by an SNCR denitrification injector. The exhaust gas after the denitrification treatment is transported to an exhaust duct through an induced draft fan. A dry desulfurization injector is provided in the exhaust duct. After the exhaust gas passes through the dry desulfurization injector in the exhaust duct for desulfurization treatment, it is dedusted by a bag filter and then discharged to the exhaust duct.

[0041] The dry desulfurization injector is spirally extended and arranged in the smoke exhaust duct for desulfurization treatment; the SNCR denitrification injector is spirally extended and arranged in the furnace of the hot blast furnace for denitrification treatment; a plurality of the dry desulfurization injectors and a plurality of the SNCR denitrification injectors are spirally extended and arranged, the spraying is uniform, the denitrification and desulfurization are rapid, the material consumption will be greatly reduced, and the desulfurization and denitrification efficiency is higher.

[0042] The dry desulfurization injector uses sodium bicarbonate as a desulfurization agent; the SNCR denitrification injector uses urea solution as a denitrification agent.

[0043] The sodium bicarbonate desulfurizer is sprayed into the dry desulfurization injector after being ground. The fine sodium bicarbonate powder is sprayed into the hot flue gas of the dry desulfurization injector and reacts rapidly to generate active sodium carbonate with a high specific surface area and high porosity. The active sodium carbonate reacts with SO2 in the flue gas and reacts with other acid gases in the flue gas.

[0044] The property of sodium bicarbonate to be converted into "activated sodium carbonate" makes it a good acid neutralizer (HCl, SO2, HF, etc.) and absorbent for heavy metals, dioxins and furans.

[0045] The sodium bicarbonate desulfurizer has a purity greater than 98%, a particle size of 0.1-2 mm, a humidity less than 1%, and a reaction temperature greater than 140°C.

[0046] The urea denitrification agent has a nitrogen content greater than 46%, a ratio concentration of 8%, and a reaction temperature between 800°C and 1200°C.

[0047] The bag dust collector is a negative pressure bag dust collector.

[0048] The injection amount of the desulfurizing agent is adjusted according to the SO2 concentration in the flue gas, and is synchronously adjusted in combination with the SO2 concentration fluctuation caused by the regular operation of the hot blast furnace.

[0049] Example 2

[0050] like Figure 3 As shown, the monitoring data were obtained by testing with qualified online monitoring instruments before the transformation, among which the content of sulfur dioxide and nitrogen oxides in smoke was high, and the emission content was large; according to the emission limits of atmospheric pollutants for combustion devices stipulated in GB 41616-2022, the emission limit of sulfur dioxide is 200 mg / m3; the emission limit of nitrogen oxides is 200 mg / m3; the particulate matter limit is 30 mg / m3; all of them did not meet the standards before the improvement.

[0051] like Figure 4As shown in the figure, after the tail gas treatment process is modified, the exhaust gas is heated by a hot blast furnace, and then denitrified in the furnace by an SNCR denitrification injector, and then transported to the exhaust flue by an induced draft fan through the front flue. The exhaust flue is equipped with a spiral extension dry desulfurization injector. After desulfurization, it is discharged to the discharge port after dust removal by a negative pressure bag filter. The modified data is detected by an online monitoring instrument that has passed the quality inspection. According to the emission limits of atmospheric pollutants for combustion devices specified in GB 41616-2022, the emission limit of sulfur dioxide is 200 mg / m3; the emission limit of nitrogen oxides is 200 mg / m3; the limit of particulate matter is 30 mg / m3; all meet the emission standards.

Claims

1. An optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid, comprising an anhydrous calcium chloride production process and a tail gas treatment process, wherein the anhydrous calcium chloride production is to obtain anhydrous calcium chloride from ammonia waste liquid through airing, three-effect evaporation, and spray granulation processes, wherein the tail gas treatment process treats the tail gas generated during the spray granulation, the tail gas generated by the spray granulation is transported to a hot blast furnace through a pipeline, the hot blast furnace heats the tail gas, the heated tail gas is denitrated by a denitrification ejector, the denitrified exhaust gas is transported to a smoke exhaust duct through an induced draft fan, a dry desulfurization ejector is arranged in the smoke exhaust duct, the exhaust gas is desulfurized by the dry desulfurization ejector in the smoke exhaust duct, and then discharged to the exhaust duct after dust removal by a bag filter.

2. The optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid according to claim 1, characterized in that: The dry desulfurization injector is spirally extended and arranged in the smoke exhaust duct for desulfurization treatment; the denitrification injector is spirally extended and arranged in the furnace of the hot blast furnace for denitrification treatment; a plurality of the dry desulfurization injectors and a plurality of the denitrification injectors are spirally extended and arranged.

3. The optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid according to claim 2, characterized in that: The dry desulfurization injector uses sodium bicarbonate as a desulfurization agent; the SNCR denitrification injector uses urea solution as a denitrification agent.

4. The optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid according to claim 3, characterized in that: The sodium bicarbonate desulfurizer has a purity of more than 98%, a particle size of 0.1-2 mm, and a humidity of less than 1%.

5. The optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid according to claim 3, characterized in that: The urea denitrification agent contains nitrogen greater than 46% and has a ratio concentration of 8%.

6. The optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid according to claim 1, characterized in that: The bag dust collector is a pulse bag dust collector.

7. The optimized tail gas treatment process for producing anhydrous calcium chloride from ammonia waste liquid according to claim 3, characterized in that: The injection amount of the desulfurizing agent is adjusted according to the SO2 concentration in the flue gas, and is synchronously adjusted in combination with the SO2 concentration fluctuation caused by the regular operation of the hot blast furnace.

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