A system for treating a dust-laden acid flue gas

Abstract

The utility model discloses a kind of treatment systems of dust-containing acid flue gas, enamel horizontal spray tower is multiple tower series connection, flue gas inlet and flue gas outlet are provided on the upper end of first and last enamel horizontal spray tower, enamel horizontal spray tower lower end is provided with liquid discharge port, the flue gas inlet of enamel horizontal spray tower is connected with pre-spray pipeline, liquid discharge port is connected to plate-and-frame filter press, alkali absorption tower and acid absorption tower lower end are each provided with flue gas inlet, top end is provided with flue gas outlet, the flue gas outlet of enamel horizontal spray tower is connected with alkali absorption tower inlet, alkali absorption tower flue gas outlet is connected with acid absorption tower inlet, the utility model is combined with on-line in situ adsorption and regeneration collaborative mechanism, through resin adsorption, the removal efficiency of acidic component is strengthened, the problem of high ammonia escape in traditional ammonia absorption technology is solved, with high denitration desulfurization efficiency (>95%), low operating cost, strong sulfur resistance, can long-period operation advantage.

Description

Technical Field

[0001] This utility model relates to the field of flue gas purification technology, and in particular to a treatment system for dust-containing acidic flue gas. Background Technology

[0002] Industrial production generates exhaust gases, which mainly contain dust and acidic gases. The acidic gases include some harmful gases containing nitrogen and sulfur compounds, which cause serious air pollution. Therefore, the treatment of industrial exhaust gases is very important.

[0003] Taking flue gas containing nitrogen oxides (NOx) as an example, commonly used flue gas denitrification methods mainly include oxidation and reduction methods. Oxidation methods involve adding an oxidant to the flue gas to convert NOx into water-soluble high-valence nitrogen oxides, followed by the addition of an alkaline neutralizing agent to form a salt. Reduction methods include SCR and SNCR, which reduce NOx in the flue gas to non-toxic and non-polluting N2 and H2O by injecting a reducing agent (such as ammonia or urea). The disadvantages are that using ammonia can lead to ammonia escape and secondary pollution, while using urea increases CO2 emissions. Both methods have relatively low denitrification efficiency and high operating costs. Therefore, there is an urgent need to find a process with high reaction efficiency, reduced operating costs, and minimized environmental harm.

[0004] When flue gas contains sulfur oxides (SOx), if the flue gas temperature is lower than the gas dew point temperature, the sulfur oxides in the flue gas will precipitate in liquid form. If the flue gas contains dust and moisture, it will form a viscous corrosive material that corrodes the flue gas pipeline and may block downstream treatment equipment. Utility Model Content

[0005] The purpose of this invention is to provide a dust-laden acidic flue gas treatment system. This system is low-temperature and highly efficient, and the weakly basic anion exchange resin in the alkali absorption tower is recyclable. This addresses the problems of low adsorption capacity, high ammonia slip, and high energy consumption in existing flue gas desulfurization and denitrification technologies, improving reaction efficiency and reducing operating costs. It is adaptable to the deacidification of flue gas containing various acids (COx, NOx, SOx, Cl-, etc.), meeting the flue gas treatment requirements of different types of industrial boilers and application scenarios.

[0006] To achieve the above objectives, this utility model adopts the following technical solution: a treatment system for dust-laden acidic flue gas, comprising a pre-spraying pipe, an enamel-lined horizontal spray tower, a plate and frame filter press, an alkali absorption tower, and an acid absorption tower. The enamel-lined horizontal spray tower is a multi-tower series connection. The first and last enamel-lined horizontal spray towers have flue gas inlets and outlets at their upper ends, and a drain outlet at their lower ends. The flue gas inlet of the enamel-lined horizontal spray tower is connected to the pre-spraying pipe, and the drain outlet is connected to the plate and frame filter press. Both the alkali absorption tower and the acid absorption tower have flue gas inlets at their lower ends and flue gas outlets at their top ends. The flue gas outlet of the enamel-lined horizontal spray tower is connected to the inlet of the alkali absorption tower, and the flue gas outlet of the alkali absorption tower is connected to the inlet of the acid absorption tower. The alkali absorption tower is filled with a weakly basic anion exchange resin layer. The weakly basic anion exchange resin is a solid alkali used to adsorb acidic gases. An ammonia water spraying device is installed above the weakly basic anion exchange resin layer for online regeneration of the weakly basic anion exchange resin.

[0007] In one preferred embodiment, the enamel-lined horizontal spray towers are arranged in series of 2 to 4 towers, with the axes of all the spray towers aligned on the same straight line.

[0008] In a preferred embodiment, the weakly basic anion exchange resin is a macroporous resin containing primary amine groups or polyamine functional groups, with a specific surface area of ​​100-500 m². 2 / g, with a pore size distribution of 5-40nm.

[0009] In a preferred embodiment, the acid absorption tower is equipped with a phosphoric acid spraying device.

[0010] Compared with the prior art, the advantages and positive effects of this utility model are as follows:

[0011] This invention utilizes a multi-tower, series-connected enamel-lined horizontal spray tower, filled with spray water. This allows high-temperature flue gas to come into contact with the cold cooling water throughout the flue gas flow path, resulting in rapid cooling and preparing the conditions for subsequent alkali absorption. Furthermore, using water as the cooling medium prevents dust carried by the flue gas from contaminating it, allowing it to flow with the water into the plate and frame for liquid-solid separation. When used in a catalyst production system, the solids are not contaminated by metal ions and can be recycled back to the upstream production system.

[0012] This novel alkali absorption tower uses a weakly basic anion exchange resin for alkali absorption. Compared to traditional SCR technology (requiring 300-400℃), the weakly basic anion exchange resin can operate at medium and low temperatures (down to 30℃), saving energy consumed in high-temperature reactions. It also exhibits high selectivity, with superior adsorption and reaction selectivity for NOx (or acidic components such as SOx) compared to traditional adsorbents (such as activated carbon). Denitrification and desulfurization efficiencies can reach over 95%. The weakly basic anion exchange resin contains -NH2 functional groups, and its bonding with acidic components is mainly through ionic or hydrogen bonds, facilitating the desorption of reaction products. The specific surface area can reach 100-500 m². 2 / g, which is beneficial for the physical adsorption of gas molecules, has a macroporous or mesoporous structure that can increase the adsorption capacity, reduces the amount of ammonia water used by 40%, and has high mechanical strength, long service life, and the adsorbent can be recycled more than 10 times (regeneration rate >90%).

[0013] 3. In another aspect, this invention uses ammonia as a regeneration reagent, which can also provide an alkaline environment for NOX (or acidic components such as SOX), making them easily soluble in water to form anions containing N, S, etc. These anions may undergo coordination reactions with the lone pair electrons of the amine groups in the weakly basic anion exchange resin to form stable complexes, thereby increasing the adsorption capacity. The alkaline environment can promote the adsorption of these acidic components and increase their contact opportunities on the resin surface. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the system of this utility model;

[0015] Legend:

[0016] 1. Pre-spraying pipeline; 2. Enameled horizontal spray tower; 3. Weakly basic anion exchange resin layer; 4. Ammonia spraying device; 5. Alkali absorption tower; 6. Acid absorption tower; 7. Acid absorption tower storage tank; 8. Alkali absorption tower storage tank; 9. Plate and frame filter press; 10. Basket filter. Detailed Implementation

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0018] Please see Figure 1This utility model provides a technical solution: a treatment system for dust-laden acidic flue gas, including a pre-spraying pipe, an enamel-lined horizontal spray tower, a plate and frame filter press, an alkali absorption tower, and an acid absorption tower. The enamel-lined horizontal spray towers are multiple towers connected in series. A flue gas inlet is provided at the upper end of the first enamel-lined horizontal spray tower, and a flue gas outlet is provided at the upper end of the last enamel-lined horizontal spray tower. A drain outlet is provided at the lower end of the enamel-lined horizontal spray tower. The flue gas inlet of the first enamel-lined horizontal spray tower is connected to the pre-spraying pipe, and the drain outlet is connected to the plate and frame filter press. Both the alkali absorption tower and the acid absorption tower have flue gas inlets at the lower end and flue gas outlets at the top. The flue gas outlet of the enamel-lined horizontal spray tower is connected to the inlet of the alkali absorption tower, and the flue gas outlet of the alkali absorption tower is connected to the inlet of the acid absorption tower. The alkaline spray tower is filled with a layer of weakly basic anion exchange resin. The weakly basic anion exchange resin is alkaline and is used to adsorb acidic gases. An ammonia spray device is installed above the weakly basic anion exchange resin layer for online regeneration of the weakly basic anion exchange resin.

[0019] The pre-spraying pipeline sprays water onto the outer wall of the pipeline to initially cool the high-temperature flue gas, reducing the flue gas temperature from over 300℃ to 120-170℃, thus preventing the high temperature of the flue gas from impacting the pipeline and downstream tower.

[0020] The enamel-lined horizontal spray towers consist of 2 to 4 units connected in series, with all towers aligned on the same axis. Each tower contains PTFE spray pipes and ceramic packing. When high-temperature flue gas flows in, water spray removes dust and small amounts of sulfides. Because the flue gas is in contact with cold water throughout its flow path, it cools rapidly, reaching temperatures below 90°C. Furthermore, the sprayed flue gas passes through a demister at the outlet to remove small droplets, controlling the humidity range to 20%–40%.

[0021] The enamel-lined horizontal spray tower can be equipped with an ammonia spray device for treating acidic flue gas with different concentrations. High-concentration acidic flue gas is controlled to pH 6.5 by ammonia spray (a portion of the acidic flue gas is pre-treated).

[0022] The weakly basic anion exchange resin packed in the alkali absorption tower is a macroporous resin containing primary amine groups or polyamine functional groups, with a specific surface area of ​​100-500 m². 2 / g, with a pore size distribution of 5-40nm;

[0023] Flue gas enters from the lower inlet of the alkali absorption tower. During its ascent, acidic gases in the flue gas are adsorbed by the weakly basic anion exchange resin, and then react with the sprayed ammonia water to form ammonium salts. These desorbed gases then flow downwards, forming an ammonium salt absorbent at the bottom of the tower. Common acidic components such as NOx are also adsorbed by the weakly basic anion exchange resin, and then react with the sprayed ammonia water. This desorption process also flows downwards, forming an ammonium nitrate and ammonium nitrite absorbent at the bottom of the absorption tower. This absorbent comes into countercurrent contact with the re-entering flue gas and the absorbent, causing the temperature to drop to 30-70℃. This is the optimal temperature for the weakly basic anion exchange resin to adsorb nitrogen dioxide.

[0024] In addition, when the NO concentration in the flue gas is too high, an ozone oxidation unit can be installed at the front end of the alkali absorption tower to oxidize some of the NO into NO2, thereby improving the treatment effect of acidic gases.

[0025] The acid absorption tower is equipped with a phosphoric acid spraying device. The flue gas passing through the alkali absorption tower is introduced into the acid absorption tower to remove excess ammonia carried out by the alkali absorption tower.

[0026] The factory flue gas duct is connected to the pre-spray duct and then to the flue gas inlet at the top of the enamel horizontal spray tower. The enamel horizontal spray tower consists of three towers connected in series. The flue gas inlet is located at the top of the first enamel horizontal spray tower, and the flue gas outlet is located at the top of the third enamel horizontal spray tower. Each of the three enamel horizontal spray towers has a drain outlet at its bottom, which is connected to a mud conveying pump, a basket filter, and a plate and frame filter press. The flue gas outlet of the enamel horizontal spray tower is connected to the flue gas inlet at the bottom of the alkali absorption tower. The upper part of the alkali absorption tower is equipped with a corrugated grid filled with structured packing material and a weakly basic anion exchange resin layer. An ammonia spray device is installed above the resin layer. The top of the alkali absorption tower has a flue gas outlet, and the bottom has a drain outlet connected to the alkali absorption tower's storage tank. The flue gas outlet is connected to the acid absorption tower, which is equipped with a phosphoric acid spray device.

[0027] The working process of this system is as follows:

[0028] (1) Initial cooling: The flue gas is rapidly cooled through the pre-spray pipe, with the temperature dropping from 350℃ to 160℃;

[0029] (2) Cooling: The flue gas enters the enamel horizontal spray tower from the flue gas inlet and is further cooled to below 90°C;

[0030] (3) Solid-liquid separation: After being sprayed by the horizontal spray tower, the liquid carrying some dust flows out from the lower end of the enameled horizontal spray tower through the mud pump connected to the lower end of the drain. The liquid is then transported through the basket filter and enters the plate and frame filter press. The plate and frame filter press is used to separate the solid and liquid. The resulting filter cake is reused, and the liquid is transported to the storage tank.

[0031] (4) The flue gas after passing through the horizontal spray tower enters the alkali absorption tower. The absorption section of the alkali absorption tower is filled with active weakly basic anion exchange resin modules. The modules are 1m high, and there are 2 modules in total, spaced at a certain distance, placed parallel to each other from top to bottom in the absorption tower. The surface area of ​​the weakly basic anion exchange resin is 420m². 2 / g, with a pore size distribution of 5-40nm, acidic components in flue gas are selectively adsorbed by a weakly basic anion exchange resin. The flue gas temperature is 50℃ and the volume hourly space velocity is 1200h-1. The adsorption of acidic components is achieved through the amine groups on the resin surface.

[0032] (5) While the alkali absorption tower absorbs acidic flue gas, ammonia water with a concentration of 10wt% is sprayed into the weakly basic anion exchange resin layer after the adsorption of acidic components to regenerate the weakly basic anion exchange resin. When the main acidic component in the flue gas is NOx, the molar ratio of ammonia added to adsorbed NOx is 1:1.

[0033] (6) Acid absorption tower: The flue gas passing through the alkali absorption tower is introduced into the acid absorption tower, and phosphoric acid is sprayed from the top of the tower to remove excess ammonia from the alkali absorption tower.

[0034] The overall system outlet parameters show a denitrification efficiency of ≥95% and an NH3 escape rate of ≤8mg (within the chemical lifespan).

[0035] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present utility model without departing from the technical solution of the present utility model shall still fall within the protection scope of the technical solution of the present utility model.

Claims

1. A treatment system for dust-laden acidic flue gas, comprising a pre-spraying pipeline, an enamel-lined horizontal spray tower, a plate and frame filter press, an alkali absorption tower, and an acid absorption tower, characterized in that: The enamel-lined horizontal spray tower is a multi-tower series configuration. The first and last enamel-lined horizontal spray towers have flue gas inlets and outlets at their upper ends, and a drain outlet at their lower ends. The flue gas inlets of the enamel-lined horizontal spray towers are connected to the pre-spraying pipeline, and the drain outlets are connected to the plate and frame filter press. Both the alkali absorption tower and the acid absorption tower have flue gas inlets at their lower ends and flue gas outlets at their top ends. The flue gas outlet of the enamel-lined horizontal spray tower is connected to the inlet of the alkali absorption tower, and the flue gas outlet of the alkali absorption tower is connected to the inlet of the acid absorption tower. The alkali absorption tower is filled with a layer of weakly basic anion exchange resin, which is a solid alkali used to adsorb acidic gases. An ammonia water spray device is installed above the weakly basic anion exchange resin layer for online regeneration of the weakly basic anion exchange resin.

2. The dust-laden acidic flue gas treatment system according to claim 1, characterized in that: The enamel-lined horizontal spray towers consist of 2 to 4 units connected in series, with the axes of all spray towers aligned on the same straight line.

3. The dust-laden acidic flue gas treatment system according to claim 1, characterized in that: The weakly basic anion exchange resin is a macroporous resin containing primary amine groups or polyamine functional groups, with a specific surface area of ​​100-500 m². 2 / g, with a pore size distribution of 5-40nm.

4. The dust-laden acidic flue gas treatment system according to claim 1, characterized in that: The acid absorption tower is equipped with a phosphoric acid spraying device.

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