Tail gas washing system and method

Abstract

The invention discloses a tail gas washing system and method, and belongs to the field of environmental protection. The system comprises a horizontal cross-flow washer, a washing filler, a demister, a filler supporting partition plate, a demister supporting partition plate, a washing liquid delivery pump, a No1-zone washing pump, a No2-zone washing pump, a No3-zone washing pump, a No4-zone washing pump, a fan and an exhaust funnel. By adopting the system and the method, the tail gas from the chemical device can be effectively washed, the technological process is short, the number of equipment is small, and production operation and maintenance are convenient. The process flow is simple, the installation is convenient, and the operation energy consumption is low.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection, and particularly to a system and method for tail gas washing. Background Art

[0002] In chemical production, tail gas is often generated. Since the tail gas contains dust and toxic and harmful components, it cannot be directly discharged. Usually, the tail gas is washed to remove the dust and toxic and harmful substances therein, and the clean non-condensable gas is discharged.

[0003] The commonly used scrubbers are as follows:

[0004] (1) Spray tower

[0005] The spray tower is a traditional scrubber. This device is easy to design and operate, with low energy consumption and pressure loss, but the washing efficiency is not high. No matter how high the tower is, only one washing concentration can be used. When the pressure of the spray liquid is increased, the washing efficiency can be improved, but the liquid entrainment and mist also increase simultaneously.

[0006] (2) Packed tower

[0007] The packed tower is more effective than the spray tower, but its disadvantage is that the bed is easy to block and not easy to clean, so it is generally not used when washing fluorides.

[0008] (3) Venturi scrubber

[0009] The Venturi scrubber has a simple structure and less investment. Since the flow rates of the gas and liquid used are very high and they are mixed at high speed in a very short time, the energy consumption of the system is very high. In addition, due to the high dispersion of the gas and liquid, a high-efficiency demisting device, usually a cyclone separator, is required to be connected behind the Venturi scrubber.

[0010] (4) Cyclone spray scrubber

[0011] The cyclone spray scrubber provides a large gas-liquid contact surface by spraying liquid into the flowing gas. The gas enters tangentially and rotates from bottom to top, and the centrifugal force generated can remove a large amount of liquid entrainment. Although the washing efficiency of this device is higher than that of a general spray tower, the disadvantages of the spray tower still exist.

[0012] The above single washing systems usually cannot meet the environmental protection requirements, and only a multi-stage washing system can achieve a high washing effect. For this reason, in actual production, the same or different devices are usually connected in series to achieve this purpose.

[0013] Therefore, in order to improve the tail gas washing efficiency, overcome the defects of the prior art, and reduce the emissions of dust and toxic and harmful substances, it is urgent to improve the existing scrubbers, washing systems and methods to achieve better washing effects and protect the environment. Summary of the Invention

[0014] The object of the present invention is to provide a tail gas washing system and method, which can effectively wash the tail gas from a chemical plant. The gas moves horizontally while the washing liquid moves vertically. Compared with a vertical washing system, it is easier to connect the washing sections in series by gradually reducing the concentration of the washing liquid in a horizontal scrubber. After being connected in series, a very high washing efficiency can be achieved.

[0015] By adopting the above system and method, only one horizontal cross-flow scrubber can effectively wash the tail gas from a chemical plant. It is a tail gas washing system and method with a short process, small floor area, low investment, and low energy consumption. The present invention aims to protect the environment and ensure that the non-condensable gas after washing meets the discharge standards.

[0016] The object of the present invention can be achieved by the following technical solutions:

[0017] A tail gas washing system, which includes a horizontal cross-flow scrubber. There are N≥2 washing sections and a demisting section in the horizontal cross-flow scrubber. Each washing section is equipped with a liquid collecting tank. The washing sections along the gas flow direction are sequentially named the 1st washing section,..., the Nth washing section;

[0018] Process water is connected to the washing pipe of the Nth washing section. The washing liquid collected in the Nth washing section enters the supporting liquid collecting tank, and the washing liquid in this liquid collecting tank is transported to the washing pipe of the (N - 1)th washing section; the washing liquid collected in the (N - 1)th washing section enters the supporting liquid collecting tank, and the washing liquid in this liquid collecting tank is transported to the washing pipe of the (N - 2)th washing section; and so on until the first washing section. The washing liquid collected in the first washing section is transported to outside the boundary.

[0019] In the above system: several vertically arranged washing pipes are provided at the upper part of the inner cavity of the horizontal cross-flow scrubber where the washing section is located, and multiple groups of nozzles are provided on the washing pipes;

[0020] Preferably: 1 - 10 vertically arranged washing pipes are provided at the upper part of the inner cavity of the horizontal cross-flow scrubber where the washing section is located, and 1 - 10 nozzles are provided on the washing pipes.

[0021] In the above system: washing packings are provided between any two adjacent washing sections between the 2nd washing section and the Nth washing section; a demister is provided between the Nth washing section and the demisting section.

[0022] In the above system: the setting direction of the nozzles of the washing pipes in the first washing section is opposite to the gas flow direction, and the setting direction of the nozzles of the washing pipes in the remaining washing sections is the same as the gas flow direction.

[0023] In the above system: the tail of the horizontal cross-flow scrubber is connected to an exhaust stack through a fan;

[0024] In the above system: An air inlet channel is provided at the upper part of the horizontal cross-flow scrubber. A spray head is provided in the channel, and the setting direction of the spray head is the same as the air flow direction. The washing liquid collected in the second washing area is connected to the spray head.

[0025] In the above system: The bottom liquid discharge port of the fan and the bottom liquid discharge port of the liquid collecting tank supporting the demisting area are both connected to the washing pipe of the (N - 1)th washing area.

[0026] In the above system: The bottom of each liquid collecting tank is an inclined bottom, and the angle between the inclined bottom and the horizontal plane is 90° ≥ α ≥ 0°.

[0027] A method for realizing tail gas washing by the above system, the method comprising the following steps:

[0028] (1) The tail gas from the battery limit enters the air inlet washing area of the horizontal cross-flow scrubber through the inlet to wash the tail gas in a co-current manner. The washed tail gas enters the first washing area of the horizontal cross-flow scrubber. In this washing area, the spray head washes the tail gas in a counter-current manner. Then, the spray heads in other washing areas wash the tail gas in a co-current manner until reaching the last washing area. After that, the tail gas passes through the demister (and enters the demisting area;

[0029] (2) The process water from the battery limit enters the last washing area. The washing liquid collected in the liquid collecting tank of the last washing area enters the washing liquid of the (N - 1)th washing area. The washing liquid of the (N - 1)th washing area enters the supporting liquid collecting tank, and the washing liquid in this liquid collecting tank serves as the washing liquid of the (N - 2)th washing area. This is carried out in sequence until the first washing area, and the washing liquid collected in the first washing area is transported out of the battery limit;

[0030] (3) The washed non-condensable gas from the demisting area of the horizontal cross-flow scrubber is pressurized by the fan through the non-condensable gas outlet N of the scrubber and then discharged to the exhaust stack.

[0031] In the above method: The temperature of the tail gas from the battery limit is 20°C to 100°C, the pressure is 90 to 100 kPa, the gas velocity in the horizontal cross-flow scrubber is 1 to 3 m / s, and the mass ratio of the tail gas from the battery limit to the process water is 1:2 to 2:1.

[0032] In some more specific technical solutions, the technical solution of the present invention is as follows:

[0033] A tail gas washing system, the system comprising a horizontal cross-flow scrubber, washing packing, a demister, a packing support and partition plate, a demister support and partition plate, a washing liquid transfer pump, a No1 area washing pump, a No2 area washing pump, a No3 area washing pump, a No4 area washing pump, a fan, and an exhaust stack. The tail gas pipeline from the battery limit is connected to the air inlet A of the horizontal cross-flow scrubber, the non-condensable gas outlet N of the horizontal cross-flow scrubber is connected to the inlet of the fan, and the outlet W of the fan is connected to the bottom inlet of the exhaust stack.

[0034] In the above system: The process water pipeline from the battery limit is connected to the process water inlets L1, L2, and L3 of the horizontal cross-flow scrubber; the bottom liquid discharge ports V of the fan, the bottom liquid discharge port U of the demisting zone liquid collection tank, and the bottom liquid discharge port T of the No. 5 zone liquid collection tank are connected to the inlet of the No. 4 zone scrubbing pump. The outlet of the No. 4 zone scrubbing pump is connected to the scrubbing liquid inlets J1, J2, and J3 of the No. 4 scrubbing zone; the bottom liquid discharge port S of the No. 4 zone liquid collection tank is connected to the inlet of the No. 3 zone scrubbing pump. The outlet of the No. 3 zone scrubbing pump is connected to the scrubbing liquid inlets G1, G2, and G3 of the No. 3 scrubbing zone; the bottom liquid discharge port R of the No. 3 zone liquid collection tank is connected to the inlet of the No. 2 zone scrubbing pump. The outlet of the No. 2 zone scrubbing pump is connected to the scrubbing liquid inlets E1, E2, and E3 of the No. 2 scrubbing zone; the bottom liquid discharge port Q of the No. 2 zone liquid collection tank is connected to the inlet of the No. 1 zone scrubbing pump. The outlet of the No. 1 zone scrubbing pump is connected to the scrubbing liquid inlets C1, C2, and C3 of the No. 1 scrubbing zone and the scrubbing liquid inlets B1, B2 of the inlet air scrubbing zone; the bottom liquid discharge port P of the No. 1 zone liquid collection tank is connected to the inlet of the scrubbing liquid transfer pump. The outlet of the scrubbing liquid transfer pump is connected to the scrubbing liquid transfer pipeline to the battery limit.

[0035] In the above system: The gas phase channel of the horizontal cross-flow scrubber is divided into five scrubbing zones, namely No. 1 scrubbing zone, No. 2 scrubbing zone, No. 3 scrubbing zone, No. 4 scrubbing zone, No. 5 scrubbing zone, and a demisting zone; between the No. 1 scrubbing zone and the No. 2 scrubbing zone, scrubbing packing can be selectively installed according to the tail gas working conditions. Port D is a spare port for packing installation. Between the No. 2 scrubbing zone and the No. 3 scrubbing zone, between the No. 3 scrubbing zone and the No. 4 scrubbing zone, and between the No. 4 scrubbing zone and the No. 5 scrubbing zone, scrubbing packing is installed through the packing installation ports F, H, and K. Between the No. 5 scrubbing zone and the demisting zone, a demister is installed through the demister installation port M. The bottom of the No. 1 scrubbing zone is the No. 1 zone liquid collection tank, the bottom of the No. 2 scrubbing zone is the No. 2 zone liquid collection tank, the bottom of the No. 3 scrubbing zone is the No. 3 zone liquid collection tank, the bottom of the No. 4 scrubbing zone is the No. 4 zone liquid collection tank, the bottom of the No. 5 scrubbing zone is the No. 5 zone liquid collection tank. Between the No. 1 - No. 5 liquid collection tanks, they are separated into independent spaces by packing support partition plates; the bottom of the demisting zone is the demisting zone liquid collection tank. Between the No. 5 zone liquid collection tank and the demisting zone liquid collection tank, they are separated into independent spaces by demister support partition plates.

[0036] In the above system: The bottom of each liquid collection tank is an inclined bottom, and the angle between the inclined bottom and the horizontal plane is α≥0° and α is as large as possible. The bottom of the inclined bottom is provided with liquid outlets P, Q, R, S, T, U.

[0037] In the above system: The inlet A of the horizontal cross-flow scrubber is a vertically arranged cuboid, and the length c is equal to twice the width b. The gas phase channel height a of the horizontal cross-flow scrubber is equal to the width b.

[0038] In the above system: in the horizontal cross-flow scrubber inlet scrubbing area, the distance e from the scrubbing liquid inlet B1 to the inlet side wall is equal to one-fourth of c, the distance f between the inlets B1 and B2 is equal to one-half of c, and the distance g from the inlet B2 to the inlet side wall is equal to one-fourth of c. One spray head is horizontally installed at each of the inlets B1 and B2. The spray head is located at the center line of the inlet A, and the spraying direction is the same as the gas flow direction. The shape of the scrubbing liquid curtain sprayed by each spray head is square, and the scrubbing liquid curtains sprayed by the two spray heads can cover the entire horizontal cross-section (c multiplied by d) of the inlet A.

[0039] In the above system: the distances h from the scrubbing liquid and process water inlets C1, E1, G1, J1, L1 of the horizontal cross-flow scrubber to the scrubber side wall are equal to one-sixth of b. The scrubbing liquid and process water inlets C2, E2, G2, J2, L2 are located at the center line of the scrubber. The distances k from the scrubbing liquid and process water inlets C3, E3, G3, J3, L3 to the scrubber side wall are equal to one-sixth of b. Three spray heads are installed at each scrubbing liquid inlet. The distance m from the upper spray head to the scrubber top is equal to one-sixth of a, the distance n from the middle spray head to the upper spray head is equal to one-third of a, and the distance p from the lower spray head to the middle spray head is equal to one-third of a. The spraying directions of the nine spray heads installed at the scrubbing liquid inlets C1, C2, C3 are opposite to the gas flow direction, and the spraying directions of the remaining spray heads are the same as the gas flow direction. The shape of the scrubbing liquid curtain sprayed by each spray head is square, and the scrubbing liquid curtains sprayed by the nine spray heads can cover the entire vertical gas phase channel cross-section (a multiplied by b) of the scrubber.

[0040] A method for realizing tail gas scrubbing by using the above system, the method comprising the following steps:

[0041] (1) Scrubbing in the inlet scrubbing area and No1 scrubbing area: The tail gas from the battery limit enters the inlet scrubbing area of the horizontal cross-flow scrubber through the inlet A. In the inlet scrubbing area, the tail gas is scrubbed in a co-current manner by the two spray heads installed at the scrubbing liquid inlets B1 and B2. The tail gas passing through the inlet scrubbing area enters the No1 scrubbing area. In the No1 scrubbing area, the tail gas is scrubbed in a counter-current manner by the nine spray heads installed at the scrubbing liquid inlets C1, C2, C3. The tail gas passing through the No1 scrubbing area enters the No2 scrubbing area. The scrubbing liquid falls into the liquid collecting tank of the No1 area and is discharged from the liquid discharge port P at the bottom of the liquid collecting tank of the No1 area to the battery limit through the scrubbing liquid transfer pump.

[0042] (2)Washing in No2, No3, and No4 washing areas: The tail gas from the No1 washing area enters the No2 washing area. In the No2 washing area, the tail gas is washed in a co-current manner with nine spray nozzles installed at the washing liquid inlets E1, E2, and E3. The tail gas passing through the No2 washing area passes through the washing packing and enters the No3 washing area. The washing liquid falls into the liquid collection tank in the No2 area and is discharged from the liquid discharge port Q at the bottom of the No2 area liquid collection tank through the No1 area washing pump to the intake air washing area and the No1 washing area; The tail gas passing through the No2 washing area enters the No3 washing area. In the No3 washing area, the tail gas is washed in a co-current manner with nine spray nozzles installed at the washing liquid inlets G1, G2, and G3. The tail gas passing through the No3 washing area passes through the washing packing and enters the No4 washing area. The washing liquid falls into the liquid collection tank in the No3 area and is discharged from the liquid discharge port R at the bottom of the No3 area liquid collection tank through the No2 area washing pump to the No2 washing area; The tail gas passing through the No3 washing area enters the No4 washing area. In the No4 washing area, the tail gas is washed in a co-current manner with nine spray nozzles installed at the washing liquid inlets J1, J2, and J3. The tail gas passing through the No4 washing area passes through the washing packing and enters the No5 washing area. The washing liquid falls into the liquid collection tank in the No4 area and is discharged from the liquid discharge port S at the bottom of the No4 area liquid collection tank through the No3 area washing pump to the No3 washing area.

[0043] (3)Washing in No5 washing area and defoaming in defoaming area: The tail gas from the No4 washing area enters the No5 washing area. In the No5 washing area, the tail gas is washed in a co-current manner with nine spray nozzles installed at the process water inlets L1, L2, and L3. The tail gas passing through the No5 washing area passes through the defoamer and enters the defoaming area. The washing liquid falls into the liquid collection tank in the No5 area and the defoaming area liquid collection tank. The washing liquid from the liquid discharge port T at the bottom of the No5 area liquid collection tank, the liquid discharge port U at the bottom of the defoaming area liquid collection tank, and the liquid discharge port V at the bottom of the fan is sent to the No4 washing area through the No4 area washing pump.

[0044] (4)Transportation and emission of non-condensable gas: The washed non-condensable gas from the defoaming area of the horizontal cross-flow scrubber enters the fan through the non-condensable gas outlet N of the scrubber and the fan inlet. After being pressurized by the fan, the non-condensable gas is discharged from the fan outlet W to the exhaust stack.

[0045] In the above method: The temperature of the tail gas from the battery limit is ≤100 °C, the pressure is ≥90 kPa, the gas velocity in the horizontal cross-flow scrubber is ≤3 m / s, and the mass ratio of the tail gas from the battery limit to the process water is ≥1:2.

[0046] More preferably: The temperature of the tail gas from the battery limit is 20 °C to 100 °C, the pressure is 90 to 100 kPa, the gas velocity in the horizontal cross-flow scrubber is 1 to 3 m / s, and the mass ratio of the tail gas from the battery limit to the process water is 1:2 to 2:1.

[0047] Advantages of the present invention:

[0048] With the system and method of the present invention, the gas moves horizontally while the washing liquid moves vertically, so a higher liquid-gas ratio can be used and the packing is fully rinsed, which is an effective method to prevent blockage.

[0049] Compared with the vertical washing system, the horizontal scrubber is easier to connect the washing sections in series by gradually reducing the concentration of the washing liquid. After being connected in series, a very high washing efficiency can be achieved, and it is one of the very satisfactory washing systems currently available for phosphoric acid, phosphate fertilizer and compound fertilizer production plants. In the tail gas washing of the phosphoric acid plant, the washing efficiencies of F and SiO2 in the tail gas both exceed 99.8%.

[0050] No washing packing is installed in the inlet gas washing area and the No1 washing area to wash the dust in the tail gas. A spare packing installation port D is provided to selectively install washing packing according to the tail gas conditions. The washing packing in the packing installation ports F, H, K and the demister in the demister installation port M can be washed and replaced regularly.

[0051] Nine spray heads with a square-shaped washing liquid curtain are installed in each washing section, so that the washing liquid is more evenly distributed and the washing space is shortened.

[0052] The inlet of the scrubber is rectangular, which is convenient for gas distribution and washing; the gas phase channel of the scrubber is square, which is convenient for tail gas washing and the installation, washing and replacement of washing packing and demister.

[0053] The scrubber can be installed on the ground, which is convenient for installation, overhaul and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is the process flow schematic diagram in the present invention

[0055] Figure 2 is the front view of the horizontal cross-flow scrubber in the present invention

[0056] Figure 3 is the top view of the horizontal cross-flow scrubber in the present invention

[0057] Figure 4 is the detailed view in the Z direction in the present invention

[0058] Among them, the horizontal cross-flow scrubber 1, the washing packing 1-1, the demister 1-2, the packing support and partition plate 1-3, the demister support and partition plate 1-4, the washing liquid delivery pump 2, the No1 area washing pump 3, the No2 area washing pump 4, the No3 area washing pump 5, the No4 area washing pump 6, the fan 7, the exhaust stack 8. DETAILED DESCRIPTION OF THE INVENTION

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. The following will detail the embodiments of the present invention. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation of the present invention.

[0060] The following will further illustrate the present invention with reference to the accompanying drawings and specific embodiments.

[0061] As Figures 1 to 4 , a tail gas washing system, the system includes a horizontal cross-flow scrubber 1, washing packing 1-1, a demister 1-2, a packing support partition plate 1-3, a demister support partition plate 1-4, a washing liquid transfer pump 2, a No1 area washing pump 3, a No2 area washing pump 4, a No3 area washing pump 5, a No4 area washing pump 6, a fan 7, and an exhaust stack 8. The tail gas pipeline from the battery limit is connected to the air inlet A of the horizontal cross-flow scrubber 1. The non-condensable gas outlet N of the horizontal cross-flow scrubber 1 is connected to the inlet of the fan 7. The outlet W of the fan 7 is connected to the bottom inlet of the exhaust stack 8.

[0062] The process water pipeline from the battery limit is connected to the process water inlets L1, L2, and L3 of the horizontal cross-flow scrubber 1; the bottom drain port V of the fan 7, the bottom drain port U of the demisting zone liquid collection tank, and the bottom drain port T of the No. 5 zone liquid collection tank are connected to the inlet of the No. 4 zone scrubbing pump 6. The outlet of the No. 4 zone scrubbing pump 6 is connected to the scrubbing liquid inlets J1, J2, and J3 of the No. 4 scrubbing zone; the bottom drain port S of the No. 4 zone liquid collection tank is connected to the inlet of the No. 3 zone scrubbing pump 5. The outlet of the No. 3 zone scrubbing pump 5 is connected to the scrubbing liquid inlets G1, G2, and G3 of the No. 3 scrubbing zone; the bottom drain port R of the No. 3 zone liquid collection tank is connected to the inlet of the No. 2 zone scrubbing pump 4. The outlet of the No. 2 zone scrubbing pump 4 is connected to the scrubbing liquid inlets E1, E2, and E3 of the No. 2 scrubbing zone; the bottom drain port Q of the No. 2 zone liquid collection tank is connected to the inlet of the No. 1 zone scrubbing pump 3. The outlet of the No. 1 zone scrubbing pump 3 is connected to the scrubbing liquid inlets C1, C2, and C3 of the No. 1 scrubbing zone and the scrubbing liquid inlets B1, B2 of the inlet air scrubbing zone; the bottom drain port P of the No. 1 zone liquid collection tank is connected to the inlet of the scrubbing liquid transfer pump 2. The outlet of the scrubbing liquid transfer pump 2 is connected to the scrubbing liquid transfer pipeline going to the battery limit.

[0063] The inlet A of the horizontal cross-flow scrubber 1 is a vertically arranged rectangle, and the length c is equal to twice the width d. The gas phase channel height a of the horizontal cross-flow scrubber 1 is equal to the width b. The gas phase channel of the horizontal cross-flow scrubber 1 is divided into five scrubbing zones, namely the No. 1 scrubbing zone, the No. 2 scrubbing zone, the No. 3 scrubbing zone, the No. 4 scrubbing zone, the No. 5 scrubbing zone, and a demisting zone; between the No. 1 scrubbing zone and the No. 2 scrubbing zone, scrubbing packing 1-1 can be selectively installed according to the tail gas working conditions, and the D port is a spare port for packing installation. Between the No. 2 scrubbing zone and the No. 3 scrubbing zone, between the No. 3 scrubbing zone and the No. 4 scrubbing zone, and between the No. 4 scrubbing zone and the No. 5 scrubbing zone, scrubbing packing 1-1 is installed through the packing installation ports F, H, and K. Between the No. 5 scrubbing zone and the demisting zone, a demister 1-2 is installed through the demister installation port M. The bottom of the No. 1 scrubbing zone is the No. 1 zone liquid collection tank, the bottom of the No. 2 scrubbing zone is the No. 2 zone liquid collection tank, the bottom of the No. 3 scrubbing zone is the No. 3 zone liquid collection tank, the bottom of the No. 4 scrubbing zone is the No. 4 zone liquid collection tank, the bottom of the No. 5 scrubbing zone is the No. 5 zone liquid collection tank. The No. 1 to No. 5 liquid collection tanks are separated by the packing support partition plate 1-3 into independent spaces; the bottom of the demisting zone is the demisting zone liquid collection tank, and the No. 5 zone liquid collection tank and the demisting zone liquid collection tank are separated by the demister support partition plate 1-4 into independent spaces. The bottom of each liquid collection tank is an inclined bottom, and the angle between the inclined bottom and the horizontal plane is α = 30°. The bottom of the inclined bottom is provided with liquid outlets P, Q, R, S, T, and U.

[0064] In the horizontal cross-flow scrubber 1, the distance e from the washing liquid inlet B1 to the inlet side wall in the inlet washing area is equal to one-fourth of c, the distance f between the inlets B1 and B2 is equal to one-half of c, and the distance g from the inlet B2 to the inlet side wall is equal to one-fourth of c. One spray head is horizontally installed at each of the inlets B1 and B2. The spray heads are located on the center line of the inlet A, and the spraying direction is the same as the gas flow direction. The shape of the washing liquid curtain sprayed by each spray head is square, and the washing liquid curtains sprayed by the two spray heads can cover the entire horizontal cross-section (c multiplied by d) of the inlet A.

[0065] In the horizontal cross-flow scrubber 1, the distance h from the washing liquid and process water inlets C1, E1, G1, J1, L1 to the scrubber side wall is equal to one-sixth of b. The washing liquid and process water inlets C2, E2, G2, J2, L2 are located at the center line of the scrubber. The distance k from the washing liquid and process water inlets C3, E3, G3, J3, L3 to the scrubber side wall is equal to one-sixth of b. Three spray heads are installed at each washing liquid inlet. The distance m from the upper spray head to the top of the scrubber is equal to one-sixth of a, the distance n from the middle spray head to the upper spray head is equal to one-third of a, and the distance p from the lower spray head to the middle spray head is equal to one-third of a. The spraying directions of the nine spray heads installed at the washing liquid inlets C1, C2, C3 are opposite to the gas flow direction, and the spraying directions of the remaining spray heads are the same as the gas flow direction. The shape of the washing liquid curtain sprayed by each spray head is square, and the washing liquid curtains sprayed by the nine spray heads can cover the entire vertical gas phase channel cross-section (a multiplied by b) of the scrubber.

[0066] The method for realizing tail gas washing by using the above system includes the following steps. There is more than one kind of washable tail gas. Taking the tail gas of a phosphoric acid production device as an example:

[0067] (1) Washing in the inlet washing area and the No1 washing area: The tail gas from the battery limit (temperature 60°C, pressure 99 kPa, mass flow rate 65.911 t / h) enters the inlet washing area from the inlet A of the horizontal cross-flow scrubber 1, and the tail gas is washed in the inlet washing area in a co-current manner by the two spray heads installed at the washing liquid inlets B1 and B2. The tail gas passing through the inlet washing area enters the No1 washing area, and in the No1 washing area, the tail gas is washed in a counter-current manner by the nine spray heads installed at the washing liquid inlets C1, C2, C3 at a gas velocity of about 1.7 m / s. The tail gas passing through the No1 washing area enters the No2 washing area. The washing liquid falls into the liquid collection tank of the No1 area and is discharged from the bottom drain port P of the No1 area liquid collection tank to the battery limit through the washing liquid transfer pump 2 (washing liquid temperature 50°C, mass flow rate 70.948 t / h).

[0068] (2)Washing in No2, No3, and No4 Washing Areas: The tail gas from the No1 washing area enters the No2 washing area. In the No2 washing area, the tail gas is washed in a co-current manner with nine spray nozzles installed at the washing liquid inlets E1, E2, and E3. The tail gas passing through the No2 washing area passes through the washing packing 1-1 and enters the No3 washing area. The washing liquid falls into the liquid collection tank in the No2 area and is discharged from the liquid discharge port Q at the bottom of the No2 area liquid collection tank through the No1 area washing pump 3 to the intake washing area and the No1 washing area; The tail gas passing through the No2 washing area enters the No3 washing area. In the No3 washing area, the tail gas is washed in a co-current manner with nine spray nozzles installed at the washing liquid inlets G1, G2, and G3. The tail gas passing through the No3 washing area passes through the washing packing 1-1 and enters the No4 washing area. The washing liquid falls into the liquid collection tank in the No3 area and is discharged from the liquid discharge port R at the bottom of the No3 area liquid collection tank through the No2 area washing pump 4 to the No2 washing area; The tail gas passing through the No3 washing area enters the No4 washing area. In the No4 washing area, the tail gas is washed in a co-current manner with nine spray nozzles installed at the washing liquid inlets J1, J2, and J3. The tail gas passing through the No4 washing area passes through the washing packing 1-1 and enters the No5 washing area. The washing liquid falls into the liquid collection tank in the No4 area and is discharged from the liquid discharge port S at the bottom of the No4 area liquid collection tank through the No3 area washing pump 5 to the No3 washing area.

[0069] (3)Washing in No5 Washing Area and Demisting in Demisting Area: The tail gas from the No4 washing area enters the No5 washing area. In the No5 washing area, the tail gas is washed in a co-current manner with nine spray nozzles installed at the process water inlets L1, L2, and L3 (the process water temperature is 30°C, the pressure is 400 kPa, and the mass flow rate is 65.911 t / h). The tail gas passing through the No5 washing area passes through the demister 1-2 and enters the demisting area. The washing liquid falls into the liquid collection tank in the No5 area and the liquid collection tank in the demisting area. The washing liquid from the liquid discharge port T at the bottom of the No5 area liquid collection tank, the liquid discharge port U at the bottom of the demisting area liquid collection tank, and the liquid discharge port V at the bottom of the fan 7 is sent to the No4 washing area through the No4 area washing pump 6.

[0070] (4)Transportation and Emission of Non-Condensable Gas: The washed non-condensable gas from the demisting area of the horizontal cross-flow washer 1 enters the fan 7 through the non-condensable gas outlet N of the washer. After being pressurized by the fan 7, the non-condensable gas (temperature 40°C, pressure 101 kPa, mass flow rate 60.949 t / h) is discharged from the outlet W of the fan 7 to the exhaust stack 8.

[0071] The operating parameters of the examples of the present invention are shown in Table 1

[0072] Table 1 Operating Parameter Table of Examples

[0073] Table 1 Operating Parameter Table of Examples

[0074]

Claims

1. An exhaust gas scrubbing system, characterized in that: The system comprises a horizontal cross-flow scrubber (1), wherein the horizontal cross-flow scrubber (1) is provided with N≥2 washing zones and a defoaming zone, each washing zone is equipped with a liquid collecting tank, and the washing zones along the air flow direction are named as the first washing zone, ..., the Nth washing zone in sequence; The process water is connected to the washing pipe of the Nth washing zone. The washing liquid collected in the Nth washing zone enters the matching collecting tank, and the washing liquid in the collecting tank is transported to the washing pipe of the N-1th washing zone; the washing liquid collected in the N-1th washing zone enters the matching collecting tank, and the washing liquid in the collecting tank is transported to the washing pipe of the N-2th washing zone; and the process proceeds to the first washing zone in sequence, and the washing liquid collected in the first washing zone is transported outside the boundary.

2. The tail gas cleaning system according to claim 1, characterized in that: The upper part of the inner cavity of the horizontal cross-flow scrubber (1) where the washing area is located is provided with a plurality of vertically arranged washing pipes, and the washing pipes are provided with a plurality of groups of nozzles; Preferably, the upper part of the inner cavity of the horizontal cross-flow scrubber (1) where the washing zone is located is provided with 1 to 10 vertically arranged washing pipes, and the washing pipes are provided with 1 to 10 nozzles.

3. The tail gas cleaning system according to claim 2, characterized in that: A washing filler is provided between any two connected washing zones from the second washing zone to the Nth washing zone; and a demister (1-2) is provided between the Nth washing zone and the demister zone.

4. The tail gas cleaning system according to claim 3, characterized in that: The setting direction of the washing pipe nozzles in the first washing area is opposite to the airflow direction, and the setting direction of the washing pipe nozzles in the remaining washing areas is the same as the airflow direction.

5. The tail gas cleaning system according to claim 1, characterized in that: The tail of the horizontal cross-flow scrubber (1) is connected to an exhaust pipe (8) via a fan (7).

6. The tail gas cleaning system according to claim 1, characterized in that: An air inlet channel is provided at the upper part of the horizontal cross-flow scrubber (1), and a nozzle is provided in the channel. The arrangement direction of the nozzle is the same as the air flow direction, and the washing liquid collected in the second washing zone is connected to the nozzle.

7. The tail gas cleaning system according to claim 2, characterized in that: The bottom drain port of the fan (7) and the bottom drain port of the liquid collecting tank matched with the defoaming zone are both connected to the washing pipe of the N-1th washing zone.

8. The tail gas cleaning system according to claim 1, characterized in that: The bottom of each liquid collecting tank is an inclined bottom, and the angle between the inclined bottom and the horizontal plane is 90°≥α≥0°.

9. A method for tail gas cleaning using the system of claim 1, characterized in that: The method comprises the following steps: (1) The tail gas from the boundary zone enters the air inlet washing zone from the inlet of the horizontal cross-flow scrubber (1) to wash the tail gas downstream, and the washed tail gas enters the first washing zone of the horizontal cross-flow scrubber (1), in which the nozzle performs countercurrent washing on the tail gas, and then the nozzles in other washing zones perform downstream washing on the tail gas until it reaches the last washing zone; then the tail gas passes through the demister (1-2) and enters the demister zone; (2) The process water from the boundary area enters the last washing area, and the washing liquid collected in the liquid collecting tank of the last washing area enters the washing liquid of the N-1 washing area; the washing liquid of the N-1 washing area enters the matching liquid collecting tank, and the washing liquid in the liquid collecting tank is used as the washing liquid of the N-2 washing area; and then proceeds to the first washing area in sequence, and the washing liquid collected in the first washing area is transported to the outside of the boundary; (3) The non-condensable gas from the defoaming zone of the horizontal cross-flow scrubber (1) is pressurized by the fan (7) from the non-condensable gas outlet N of the scrubber and then discharged to the exhaust pipe (8).

10. The method according to claim 9, characterized in that: The tail gas from the boundary zone has a temperature of 20°C to 100°C, a pressure of 90 to 100 kPa, a gas velocity of 1 to 3 m / s in the horizontal cross-flow scrubber (1), and a mass ratio of the tail gas from the boundary zone to the process water of 1:2 to 2:1.

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