WO2016011682A1

WO2016011682A1 - Equipment and method for circulating fluidized bed semidry simultaneous desulfurization, denitration, demercuration, and removal of dioxins of sintering flue gas

Info

Publication number: WO2016011682A1
Application number: PCT/CN2014/084111
Authority: WO
Inventors: 朱廷钰; 徐文青; 赵瑞壮; 叶猛
Original assignee: 中国科学院过程工程研究所; 北京正实同创环境工程科技有限公司
Priority date: 2014-07-21
Filing date: 2014-08-11
Publication date: 2016-01-28
Also published as: CN104107627A

Abstract

Equipment and a method for circulating fluidized bed semidry simultaneous desulfurization, denitration, demercuration, and removal of dioxins of a sintering flue gas, comprising an ozone generator (2), a diluting blower (1), a mixing buffer tank (3), an ozone distributor (4), and a circulating fluidized bed reactor tower (12). A flue gas oxidized by ozone is introduced into the circulating fluidized bed reactor tower (12), removal of SO_x and NO_x is implemented by a Ca-based absorbent under the action of atomized water, and contaminants such as Hg and dioxins in the flue gas are removed by an activated carbon adsorbent, thus implementing simultaneous desulfurization, denitration, demercuration, and removal of the dioxins. This provides the characteristics of a simple system, great performance, small footprint, and inexpensive investments and provides very considerable application prospects in the steel industry.

Description

Semi-dry method combined with desulfurization, denitrification, mercury removal and dioxin device and method for sintering flue gas circulation fluidized bed

The invention belongs to the field of flue gas purification, and particularly relates to a sintering flue gas circulating fluidized bed semi-dry method combined with desulfurization, denitrification, mercury removal and dioxin device and method in the steel industry.

Background technique

Steel industry pollutant emissions varied, and emission of various pollutants rank the forefront of the industry, it was reported that more than 50%, 90% and ₈₀₂ dioxin and NO _x emissions from the steel industry in the sintering step. The "Twelfth Five-Year Plan" just issued the "Steel Sintering, Pellet Industry Air Pollutant Emission Standards" has greatly improved the discharge standards for various pollutants, and put forward new requirements for the treatment of sintering flue gas pollution, from the original dust, The treatment of two single pollutants of sulfur dioxide (S0 ₂ ) has become a comprehensive treatment of various pollutants. Therefore, there is an urgent need for a joint removal technology and device for various pollutants in sintering flue gas.

At present, the domestic technology for simultaneously removing a variety of pollutants in various steel sintering flue gases is very scarce. The prior art is mostly focused on single desulfurization, denitrification, or combined desulfurization and denitrification, on combined mercury removal, de-dioxin, etc. Technology is even rarer. For example, CN 102228788A discloses a synergistic removal method for the combined removal of S0 ₂ and dioxins, but does not consider the combined removal of nitrogen oxides. At present, the CFB semi-dry method combined with desulfurization and denitrification based on oxidation method has found that it has good efficiency for desulfurization and denitrification, but it has poor effect on removal of mercury and dioxins. New industry emission standards require that we must actively develop effective removal technologies for multiple pollutants. Summary of the invention

In view of the above-mentioned technical deficiencies, in order to break through the existing sintering flue gas alone or in combination On the basis of the existing semi-dry desulfurization performance of the circulating fluidized bed, the present invention realizes simultaneous desulfurization and denitrification of the sintering flue gas by increasing the ozone oxidation process, and further realizes mercury removal by adding an activated carbon adsorbent (AC adsorbent). For the purpose of dedioxining, an aspect of the present invention provides a device for synergistic desulfurization, denitrification, demercuration and deoxygenation of steel sintering flue gas.

In order to achieve the above object, the present invention adopts the following technical solutions:

A sintering flue gas circulating fluidized bed semi-dry method combined with desulfurization and denitration device, the device comprises an ozone generator 2, a dilution fan 1, a mixing buffer tank 3, an ozone distributor 4 and a circulating fluidized bed reaction tower 12; The ozone generator 2 and the dilution fan 1 are connected to the inlet of the mixing buffer tank 3;

The ozone distributor 4 is installed in the flue 4', and a connection port is provided outside the flue 4' to be connected to the outlet of the mixing buffer tank 3;

The flue gas inlet 5 of the circulating fluidized bed reaction column 12 is connected to a flue 4' in which the ozone distributor 4 is disposed. The ozone distributor 4 enables the ozone generated by the ozone generator 2 to be evenly distributed in the flue, thereby maximizing the oxidation efficiency and reducing the ozone loss. The ozone distributor can be manufactured by the prior art, as disclosed in the invention of the application No. 201410059167.5 or 201410066906.3.

The circulating fluidized bed reaction column therein may be simply referred to as a CFB reaction column.

After sintering flue gas into the flue 4 ', are oxidized by ozone gas generated by an ozone generator 2, some or all of the flue gas NO is oxidized to NO _X high state, S0 ₂ will also be partially oxidized to S0 ₃ The oxidized flue gas enters the circulating fluidized bed reaction tower 12 through the flue gas inlet 5 of the circulating fluidized bed reaction tower 12, and the S0 ₂ and SO P in the flue gas are caused by the Ca-based absorbent under the action of the atomized water. valence state _the NO _x removal reaction.

Various forms of Hg and dioxin in the flue gas react with the activated carbon adsorbent to achieve the purpose of removal.

Preferably, the portion where the ozone distributor 4 is disposed is between the flue gas inlet 5 of the circulating fluidized bed reaction column 9 The distance of the flue 4' is 15~30 meters.

For the apparatus of the present invention, the upper outlet 13 of the circulating fluidized bed reaction column 12 is connected to the cyclone separator 14, and the cyclone separating hopper 15 is connected to the circulating fluidized bed reaction column 12 return port 18 through the air chute 16.

The cyclone separator 14 functions to separate the reacted Ca-based absorbent and the activated carbon adsorbent from the flue gas, and then return to the circulating fluidized bed reaction column 12 through the air chute 16 to continue to participate in the reaction.

Preferably, the upper outlet 13 of the circulating fluidized bed reaction column 12 is tangentially connected to the cyclone 14. For the apparatus of the present invention, the bottom of the circulating fluidized bed reaction tower 12 is a venturi structure, and the Venturi expansion section 19 is provided with a feed port, a return port 18 and a water spray gun 17, and the spray gun 17 nozzle is smoked. Installed in the downstream direction;

Preferably, the feed port is provided as two 6, 7, respectively, a Ca-based absorbent feed port 6 and an activated carbon adsorbent feed port 7.

For the apparatus of the present invention, the cyclone separator 14 is coupled to the baghouse 20, the baghouse 20 is connected to the ash bin 21, the ash bin 21 is provided with two outlets, and the first outlet 22 is fluidized by a pneumatic conveying pipe. The bed reaction tower 12 is connected to the feed port 18, and the purpose of the bag filter 20 is to stabilize the bed pressure and achieve further recycling of the absorbent. The second outlet 23 is connected to the ash store 24 to realize the outer row.

Preferably, the baghouse 20 is provided with a chimney 25 to discharge flue gas after removing a plurality of contaminants. The flue gas is further removed by the bag filter 20 and discharged into the atmosphere via the bacon 25.

Another object of the present invention is to provide a method for removing multi-contaminants by the above-mentioned circulating fluidized bed semi-dry method combined with desulfurization, denitration and mercury removal dioxin removal device, the method comprising the following steps:

1) spraying ozone into the flue 4' to react the ozone with the flue gas;

Preferably, the specific process of step 1) is: the ozone generated by the ozone generator 2 is uniformly mixed in the mixing buffer tank 3 by the dilution fan 1, and is sprayed into the flue 4' through the ozone distributor 4, and the smell is sprayed. Sufficient contact with the flue gas oxygen reaction, some or all of the flue gas NO is oxidized to NO _X high state, S0 ₂ will also be partially oxidized to S0 _3;

2) the oxidized flue gas fed to the circulating fluidized bed reaction tower 12, the flue gas S0 _2, S0 _3, and the Ca-based NO _x absorbent is atomized under the action of the reaction of water in the reaction column 12 mainly Remove

3) Various forms of Hg and dioxins in the flue gas are mainly reacted with activated carbon adsorbents for removal.

For the method of the present invention, the molar ratio of the ozone injected in the step 1) to the NO in the flue gas is 0.25 to 1.2, for example, 0.26 to 1.49, 0.45-1.15, 0.55 to 1.05, etc.; and the reaction time is 0.5 to 5 s, For example, 0.6 to 4.9 s, 1.0 to 3.5 s, 1.5 to 2.5 s, 2 s, etc. may be selected; Step 2) The Ca-based absorbent has a Ca/(S+N) molar ratio of 1.1 to 2.0, for example, 1.11 to 1.96. 1.3 to 1.8, 1.42-1.67, 1.53, etc., preferably a ratio of 1.2 to 1.5.

For the method of the present invention, the reacted Ca-based absorbent and activated carbon adsorbent are separated by a cyclone separator 14 and returned to the circulating fluidized bed reaction column 12 through the air chute 16 to achieve multiple cycles, and the flue gas passes through the baghouse 20 After the dust is further removed and discharged into the atmosphere, the dust collected by the baghouse 20 is returned to the circulating fluidized bed reaction column 12 by pneumatic conveying, which can stabilize the bed pressure and achieve further circulation of the absorbent.

For the method of the present invention, in step 2), the water spray amount of the water spray gun (14) is adjusted to control the temperature of the flue gas in the circulating fluidized bed reaction tower (9) above the acid dew point, generally 75 to 80°. C, for example, 76 ° C, 79 ° C, 82 ° C, 84 ° C, etc.; by adjusting the circulating return amount of the air chute (13), controlling the pressure difference between the inlet and outlet of the circulating fluidized bed reaction column (9), The particle concentration in the control tower satisfies the above Ca/(S+N) molar ratio requirement.

The invention adjusts the water spray amount according to the flue gas temperature of the outlet 13 of the circulating fluidized bed reaction tower 12, and ensures that the temperature in the circulating fluidized bed reaction tower tower is maintained above the flue gas dew point. Preferably, in step 3), the added activated carbon adsorbent is added in a mass ratio of Ca-based absorbent to activated carbon adsorbent of 15:1-25:1, and the mass ratio may be selected from 15.1:1-24.9:1, 16 :1-24:1, 17.5:1-22.5:1, 19:1-21:1, 20:1.

The invention can control the Hg and dioxin pollutants in the flue gas after the treatment by controlling the addition amount of the Ca-based absorbent to control the concentration of sulfur oxides and nitrogen oxides in the flue gas after treatment and adjusting the addition amount of the activated carbon adsorbent. concentration. Compared with the prior art solutions, the present invention has the following advantages:

1) The system is simple, the floor space is small, and the investment and operating costs are low.

2) by adding activated carbon adsorbent and an ozone oxidant, to achieve a synergistic removal of more contaminants SO _{_x,} NO _x, Hg and dioxins.

3) The cyclone separator 14 and the bag filter 20 collect the material and return it to the absorption tower 12, thereby realizing the extra-column circulation of the absorber, thereby improving the utilization efficiency of the absorbent.

4) High removal efficiency for S0 ₂ , NO, Hg and dioxins. When good operating condition, the desulfurization efficiency CFB technology semidry up to 90%; NO in the flue gas ₀₃ is oxidized very fast rate, the denitration efficiency can be more than 80%; dioxins Removal efficiency >70%; heavy metal removal efficiency ≥90%. DRAWINGS

Figure 1 is a process flow diagram of the present invention;

In the figure: 1-diluted fan; 2-ozone generator; 3-mixed buffer tank; 4-ozone distributor; 4'-flue; 5-cycle fluidized bed reactor bottom inlet; 6-Ca-based absorbent Slurry; 7-activated carbon adsorbent silo; 8-spiral conveyor; 9-Ca-based absorbent cartridge; 10-screw conveyor; 11-AC-based absorbent cartridge; 12-cycle Fluidized bed reaction column; 13-circulating fluidized bed reaction column upper outlet; 14-cyclone separator; 15- cyclone separator hopper; 16-air chute; 17-water spray gun; 18-return port; Venturi expansion section; 20-bag duster; 21 ash silo; 22-first exit; 23-second exit; 24-ash ash; 25-chimney.

The invention is further described in detail below. However, the following examples are merely illustrative of the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the claims. Concrete implementation

In order to facilitate the understanding of the present invention, the present invention is exemplified by the following. It should be understood by those skilled in the art that the present invention is only to be construed as a Implementation

Sintering flue gas circulating fluidized bed semi-dry method synergistic desulfurization denitrification demercuration deoxygenation dioxin device, characterized in that the device comprises ozone generator 2, mixing buffer tank 3, ozone distributor 4 and circulating fluidized bed reaction Tower 12;

The ozone generator 2 and the dilution fan 1 are connected to the inlet of the mixing buffer tank 3;

The flue gas inlet 5 of the circulating fluidized bed reaction column is connected to the flue 4' where the ozone distributor 4 is disposed, preferably, the portion where the ozone distributor 4 is disposed and the flue gas inlet 5 of the circulating fluidized bed reaction column 12 The distance of the road is 15~30 meters;

Preferably, the circulating fluidized bed reaction column upper outlet 13 is connected to the cyclone separator 14, and the cyclone separating hopper 15 is connected to the circulating fluidized bed reaction column 12 return port 18 through the air chute 16; preferably, The upper outlet 13 of the circulating fluidized bed reaction column 12 is tangentially connected to the cyclone separator 14; Preferably, the cyclone separator 14 is connected to the baghouse 20, the baghouse 20 is connected to the ash bin 21, the ash bin 21 is provided with two outlets, and the first outlet 22 is passed through the pneumatic conveying pipe and the circulating fluidized bed reaction tower 12 The material port 18 is connected, the second outlet 23 is connected to the ash store 24; the bag filter 20 is provided with a chimney 25 to discharge the flue gas after removing a plurality of pollutants;

Preferably, the bottom of the circulating fluidized bed reaction tower 12 is a venturi structure, and the venturi expansion section 19 is provided with a feed port, a return port 18 and a water spray gun 17, and the nozzle of the water spray gun 17 follows the direction of the flue gas. Preferably, the feed port is provided as two 6, 7, one is a Ca-based absorbent feed port 6, and the other is an activated carbon sorbent feed port 7.

The method for desulfurization, denitrification, mercury removal and deodorization using the above-mentioned sintering flue gas simultaneous desulfurization and denitration device comprises the following steps:

The ozone generated by the ozone generator 2 and the dilution wind generated by the dilution fan 1 are mixed into the mixing buffer tank 3, and then injected into the flue 4' through the ozone distributor 4, and the injected ozone is in full contact with the flue gas, mainly the flue gas. the NO _X NO oxidation reaction, smoke and CFB oxidized fluidized Ca-based activated carbon adsorbent and absorbent valency, to achieve a variety of pollutants SO _{_x,} NO _x, Hg and dioxin, etc. Synergistic removal, the flue gas after the reaction entrains a certain amount of solid particles, and the dust is collected twice by the cyclone separator 14 and the bag filter 20, and then the flue gas is discharged through the bacon 25, and the ash collected by the cyclone 14 is returned to the circulation. The fluidized bed reaction column 12, the dust portion under the baghouse 20 is returned to the circulating fluidized bed reaction column 12.

Example 1

The removal of the sintering flue gas synergistic desulfurization, denitrification, mercury removal and dioxin removal apparatus as described above includes the following steps:

The ozone generated by the ozone generator 2 and the dilution wind generated by the dilution fan 1 enter the mixing buffer tank 3 Line mixed, then distribution of ozone injected into the flue 4 4 ', ozone injected into full contact with the flue gas, primarily oxidizes NO to NO _X in the flue gas valency, smoke and oxidized fluidized CFB the activated carbon adsorbent, and Ca-based sorbent reacts synergies removing more contaminants SO _{_x,} NO _x, Hg and dioxin and other flue gas reaction after a certain amount of solid particles entrained by the cyclone 14 and the bag filter 20 collects the dust twice and then discharges the clean flue gas through the bacon 25, and the ash collected by the cyclone 14 is returned to the reaction tower 12, and the dust portion under the precipitator 20 is returned to the reaction tower 12.

The distance between the portion where the ozone distributor 4 is disposed and the flue gas inlet 5 of the CFB reaction tower is set to 30 m, and the molar ratio of ozone generated by the ozone generator 2 to NO in the flue gas is 0.6, and the reaction is 0.5. s, control the amount of lime slurry injected Ca / (S + N) molar ratio is 1.5, the mass ratio of added Ca-based absorbent to activated carbon adsorbent is 15:1, desulfurization efficiency can reach more than 90%, denitration efficiency can be More than 50%, dioxin-like pollutant removal efficiency ≥ 80%, heavy metal removal efficiency ≥ 90%.

Example 2

The ozone generated by the ozone generator 2 and the dilution wind generated by the dilution fan 1 are mixed into the mixing buffer tank 3, and then injected into the flue 4' through the ozone distributor 4, and the injected ozone is in full contact with the flue gas, mainly the flue gas. the NO _X NO oxidation reaction, smoke and CFB oxidized fluidized Ca-based activated carbon adsorbent and absorbent valency, to achieve a variety of pollutants SO _{_x,} NO _x, Hg and dioxin, etc. Synergistic removal, the flue gas after the reaction entrains a certain amount of solid particles, and the dust is collected twice by the cyclone separator 14 and the bag filter 20, and then the flue gas is discharged through the bacon 25, and the ash collected by the cyclone 14 is returned to the reaction. At the tower 12, the dust portion under the dust remover 20 is returned to the reaction tower 12.

The distance between the portion where the ozone distributor 4 is disposed and the flue gas inlet 5 of the CFB reaction tower is set to 15 meters, and the molar ratio of ozone generated by the ozone generator 2 to NO in the flue gas is 1.0, 3s, control the amount of lime slurry injected Ca / (S + N) molar ratio is 1.2, the mass ratio of added Ca-based absorbent to activated carbon adsorbent is 25: 1, desulfurization efficiency can reach more than 90%, denitration efficiency can be More than 90%, dioxin-like pollutant removal efficiency ≥ 80%, heavy metal removal efficiency ≥ 90%.

Example 3

The distance between the portion where the ozone distributor 4 is disposed and the flue gas inlet 5 of the CFB reaction tower is set to 20 meters, and the molar ratio of ozone generated by the ozone generator 2 to NO in the flue gas is 0.25, and the reaction is 5 seconds. The Ca/(S+N) molar ratio of the injected lime slurry is 2.0, the mass ratio of the added Ca-based absorbent to the activated carbon adsorbent is 20:1, the desulfurization efficiency is over 90%, and the denitration efficiency is up to More than 20%, the removal efficiency of dioxin pollutants is ≥80%, and the removal efficiency of heavy metals is ≥90%.

Example 4

The ozone generated by the ozone generator 2 is mixed with the dilution wind generated by the dilution fan 1 into the mixing buffer tank 3, and then injected into the flue 4' through the ozone distributor 4, and the injected ozone is in full contact with the flue gas. To oxidize NO in the flue gas NO _X is higher valence state, and CFB oxidized flue gas fluidized activated carbon adsorbent, and Ca-based sorbent reacts achieve SO _{_x,} NO _x, Hg and dioxin and other The synergistic removal of the pollutants, the flue gas after the reaction entrains a certain amount of solid particles, and the dust is collected twice by the cyclone separator 14 and the bag filter 20, and then the flue gas is discharged through the bacon 25, and the cyclone separator 14 collects the collected flue gas. The ash is all returned to the reaction column 12, and the dust portion under the dust remover 20 is returned to the reaction column 12.

The distance between the portion where the ozone distributor 4 is disposed and the flue gas inlet 5 of the CFB reaction tower is set to 25 m, and the molar ratio of the ozone generated by the ozone generator 2 to the NO in the flue gas is 1.5, and the reaction is 2.5. s, control the amount of lime slurry injected Ca / (S + N) molar ratio is 1.1, the mass ratio of the added Ca-based absorbent to the activated carbon adsorbent is 22:1, the desulfurization efficiency can reach more than 90%, the denitration efficiency can be More than 90%, dioxin-like pollutant removal efficiency ≥ 80%, heavy metal removal efficiency ≥ 90%. The Applicant declares that the present invention illustrates the detailed structural features of the present invention and the desulfurization and denitration method by the above embodiments, but the present invention is not limited to the above detailed structural features and the contaminant removal method, that is, does not mean that the present invention must rely on the above. Detailed structural features and removal methods can be implemented. It will be apparent to those skilled in the art that any modifications of the present invention, equivalent substitutions of the components selected for the present invention, and the addition of the components, the selection of the specific means, and the like, are all within the scope of the present invention.

Claims

Claim

A sintering flue gas circulating fluidized bed semi-dry combined desulfurization and denitration device, characterized in that the device comprises an ozone generator (2), a dilution fan (1), a mixing buffer tank (3), an ozone distributor (4) and a circulating fluidized bed reaction column (12);

The ozone generator (2) and the dilution fan (1) are connected to the inlet of the mixing buffer tank (3); the ozone distributor (4) is installed in the flue (4'), in the flue (4') An external connection port is connected to the outlet of the mixing buffer tank (3);

The flue gas inlet (5) of the circulating fluidized bed reaction column (12) is connected to a flue (4') in which the ozone distributor (4) is disposed.

2. Apparatus according to claim 1, characterized in that the distance between the portion where the ozone distributor (4) is arranged and the flue gas inlet (5) of the circulating fluidized bed reaction column (9) For 15 to 30 meters.

3. Apparatus according to claim 1 or 2, characterized in that the upper outlet (13) of the circulating fluidized bed reaction column (12) is connected to a cyclone (14), and the cyclone separation hopper (15) Connected to the return port (18) of the circulating fluidized bed reaction column (12) through the air chute (16);

Preferably, the upper outlet (13) of the circulating fluidized bed reaction column (12) is tangentially connected to the cyclone (14).

The apparatus according to any one of claims 1 to 3, wherein the bottom of the circulating fluidized bed reaction tower (12) is a venturi structure, and the venturi expansion section (19) is provided with a feed port. The return port (18) and the water spray gun (17), the water spray gun (17) are installed in the direction of the flue gas;

Preferably, the feed port is provided as two (6, 7), respectively a Ca-based absorbent feed port (6) and an activated carbon adsorbent feed port (7).

5. Apparatus according to any one of claims 1 - 4, characterized in that the cyclone (14) is connected to a bag filter (20), a bag filter (20) hopper and an ash bin (21) Connected, ash silo (21) Two outlets are provided, the first outlet (22) is connected to the circulating fluidized bed reaction tower (12) return port (18) through a pneumatic conveying pipeline, and the second outlet (23) is connected to the ash silo (24);

Preferably, the bag filter (20) is provided with bacon (25).

6. A method of multi-contaminant removal using the apparatus of any of claims 1-5, comprising the steps of:

1) Spray ozone into the flue (4') to react the ozone with the flue gas;

2) the oxidized flue gas fed to the circulating fluidized bed reaction column (12), the flue gas S0 _2, S0 _3, and NO _x in the reaction column 12) (mainly Ca-based sorbent of the atomized water The reaction is removed under the action;

3) Various forms of Hg and dioxin pollutants in the flue gas are mainly reacted with activated carbon adsorbents for removal.

7. The method according to claim 6, wherein the specific process of step 1) is: the ozone generated by the ozone generator (2) is uniformly mixed in the mixing buffer tank (3) by the dilution fan (1) , the ozone distributor (4) is sprayed into the flue (4'), and the injected ozone is in full contact with the flue gas.

The method according to claim 6 or 7, wherein the step 1) the molar ratio of the injected ozone to the NO in the flue gas is 0.25 to 1.2; the reaction time is 0.5 to 5 s; Ca-based absorbent is added in a ratio of Ca / (S + N) molar ratio of 1.1 to 2.0, preferably 1.2 to 1.5;

Preferably, the reacted Ca-based absorbent and the activated carbon adsorbent are separated by a cyclone (14) and then returned to the circulating fluidized bed reaction column (12) through the air chute (16) to achieve multiple cycles, and the flue gas passes through the bag. The dust remover (20) is further removed from the dust and discharged into the atmosphere, and the dust collected by the bag filter (20) is pneumatically transported back to the circulating fluidized bed reaction tower (12).

The method according to any one of claims 6-8, wherein in step 2), the amount of water sprayed by the water spray gun (14) is adjusted to control the smoke in the circulating fluidized bed reaction tower (9) The gas temperature is above the acid dew point; the circulating fluidized bed reaction column is controlled by adjusting the circulating return amount of the air chute (13) (9) The pressure difference between the inlet and outlet, and the particle concentration in the control tower, meet the Ca/(S+N) molar ratio requirement.

The method according to any one of claims 6 to 9, wherein the step 3) the added activated carbon adsorbent has a mass ratio of the Ca-based absorbent to the activated carbon adsorbent of 15:1 to 25:1. Join.