KR101465140B1 - Desulfurization system of biogas - Google Patents

Abstract

The present invention relates to a biogas desulfurizing system by which hydrogen sulfide can be highly effectively removed, wherein a first treating tank in which caustic soda treating water is stored during treatment of a biogas including hydrogen sulfide; and a second treating tank in which caustic soda+hypochlorite soda treating water is stored, are serially installed. The biogas desulfurizing system of the present invention comprises a first treating tank (100) which is provided with a biogas in order to be contacted with caustic soda treating water and firstly treated; a second treating tank which is provided with a firstly treated gas discharged from the first treating tank (100) in order to be contacted with caustic soda+hypochlorite soda treating water and be secondly treated; a caustic soda supplying device (300) which supplies caustic soda to the first and second treating tanks (200); a hypochlorite soda supplying device (400) which supplies hypochlorite soda to the second treating tank (200); a water supplying device (500) which supplies water to the first and second treating tanks (100, 200); and a control unit (600) which maintains the pH of the first and second treating tanks (100, 200).

Description

{DESULFURIZATION SYSTEM OF BIOGAS}

In the present invention, a primary treatment tank for storing caustic soda treated water and a secondary treatment tank for storing caustic soda + sodium hypochlorite treated water are connected in series during the treatment of biogas containing hydrogen sulfide to remove hydrogen sulfide with high efficiency The present invention relates to a biogas desulfurization system.

The conventional method for removing hydrogen sulfide in biogas generated by anaerobic digestion of organic wastes such as food, livestock manure, and sewage sludge uses a dry desulfurization method of adsorbing and removing by using an adsorbent or a wet desulfurization method of neutralizing and removing by caustic soda have. In the past, sludge generated during sewage disposal was treated in the sewage treatment plant and hydrogen sulfide in the biogas generated was treated. In the case of treating only sludge, the dry desulfurization method was used in which the concentration of hydrogen sulfide was about 500 ppm or less. However, in recent years, there has been a tendency to treat sewage and wastewater in a sewage treatment plant in connection with sewage treatment or to energize organic wastes (livestock manure, food, etc.). At this time, the concentration of hydrogen sulfide in the biogas is in the range of about 2,000 to 4,000 ppm, The desulfurization method has a disadvantage in that it can not maintain its high efficiency in a competitive manner because it is inferior in economic efficiency. Since the biogas is used as a fuel for a boiler or a generator, a city gas and a gas for charging a vehicle, The method is emerging as an alternative.

Conventionally, the wet desulfurization method also uses a neutralization method using only caustic soda. However, when the high concentration of hydrogen sulfide is removed with high efficiency using only caustic soda, the pH can be removed by maintaining the pH at 12 or higher.

The wet desulfurization method using such caustic soda has the following problems.

1. Caustic soda reacts with hydrogen sulphide and scales cause scales on the inner wall and piping of the equipment, causing clogging of piping and malfunction of equipment

H ₂ S + ₂ NaOH → Na ₂ S + 2H ₂ O

2. The higher the pH, the greater the reaction between caustic soda and carbon dioxide, which leads to the excessive consumption of caustic soda

3. In the removal of hydrogen sulfide by using caustic soda, Na ₂ S reacts with H ₂ O in water and changes into NaSH. Na ₂ S and NaSH are strong reducing agents of organic sulfides, is a problem in that because the H ₂ S thereby reducing the recurrence acid _{(Na 2 S + H 2 O} → NaOH + NaSH)

4. Na ₂ S and NaSH are easily decomposed due to high corrosiveness and corrosiveness.

5. Since Na ₂ S and NaSH are strongly alkaline, it affects the pH control to control the introduction of caustic soda to remove hydrogen sulfide, and thus the removal rate of hydrogen sulfide can be reduced even if caustic soda injection is continued.

These problems are accompanied by problems of increase in maintenance cost and treatment of strong alkaline wastewater. In addition, although biogas has been mainly used as a boiler fuel in the past, biogas has recently been purified to be used for city gas, vehicle-charging gas, and fuel cell, so a desulfurization facility capable of stably maintaining high efficiency is required Do.

The object of the present invention is to provide a method for treating hydrogen sulfide-containing biogas, comprising the steps of: preparing a first treatment tank for storing caustic soda treated water and a second treatment tank for storing caustic soda + sodium hypochlorite treated water in series, And to provide a biogas desulfurization system that can be removed with high efficiency.

A biogas desulfurization system according to the present invention comprises a primary treatment tank 100 for supplying biogas to a primary treatment tank 100 for contacting primary treatment with caustic soda water and a primary treatment tank 100 for supplying primary treatment gas discharged from the primary treatment tank 100 A secondary treatment tank 200 for secondary treatment in contact with caustic soda / sodium hypochlorite treated water, a caustic soda supply device 300 for supplying caustic soda to the primary and secondary treatment tanks 200, A sodium hypochlorite supply device 400 for supplying sodium hypochlorite to the secondary treatment tank 200, a water supply device 500 for supplying water to the primary and secondary treatment tanks 100 and 200, And a control unit (600) for maintaining the pH of the tea treatment tank (100, 200)

The first treatment tank 100 is provided with a first treated water storage tank 110 in which caustic soda treatment water is stored therein and a first water supply unit 110 connected to the first treated water storage tank 110, A first caustic soda inflow part 130 located at an inner upper side of the first treated water storage tank 110 and supplying caustic soda to the inside of the first treated water storage tank 110, The first treated water storage tank 110 and the second treated water storage tank 110 are supplied with the biosynthetic water to be supplied to the first treated water storage tank 110 and the residual hydrogen sulfide H ₂ S is firstly removed A first process gas discharge unit 170 for discharging the first process gas introduced into the first process water storage tank 110 to the outside, A first pH sensor 180 for identifying the pH of the stored caustic soda treatment water of the first treated water storage tank 110, A first water level sensor 181 for checking the water level of the caustic soda treated water and a first treated water discharge portion 190 for discharging the first treated water stored in the first treated water storage tank 110 to the outside ,

The second treatment tank 200 includes a second treatment water storage tank 210 in which caustic soda treatment water is stored therein and a second water supply unit 210 connected to the second treatment water storage tank 210, A second caustic soda inflow part 230 located at an inner upper side of the second treated water storage tank 210 and supplying caustic soda to the inside of the second treated water storage tank 210, A sodium hypochlorite supply unit 240 for supplying sodium hypochlorite to the inside of the first process water storage tank 110 and a first process gas discharge unit 170 of the first process water storage tank 110 to supply the first process gas The first process gas inlet 250 and the caustic soda / sodium hypochlorite treated water stored in the second process water storage tank 210 are supplied to be contacted with the primary process gas discharged from the first process tank 100 A second biogas treatment unit 260 for secondarily removing residual hydrogen sulfide (H ₂ S) by spraying, a second biogas treatment unit 260 for removing residual hydrogen sulfide A second pH sensor 280 for confirming the pH of the caustic soda / sodium hypochlorite treated water stored in the second treated water storage tank 210, a second process gas discharge unit 270 for discharging the introduced process gas to the outside, An ORP sensor 282 for confirming the ORP (redox potential difference) of the treated water, and a second treated water storage tank 210 for caustic soda and sodium hypochlorite And a second process water discharge unit 290 for discharging the stored secondary process water to the outside.

Preferably, the controller 600 includes a first controller 610 for adjusting the supply amount of water and caustic soda supplied to the first treated water storage tank 110 to maintain the pH of the caustic soda treated water in a predetermined state, And a second controller 620 for controlling the supply amount of water, caustic soda, and sodium hypochlorite supplied to the second treated water storage tank 210 so as to maintain the pH and ORP of the soda / .

In the desulfurization system according to the present invention, caustic soda is used to remove about 70% of the hydrogen sulfide contained in the biogas in the first stage, and hydrogen sulfide untreated in the first stage is mixed with caustic soda and sodium hypochlorite in the second stage 99% or more can be removed.

Further, in the present invention, the following improvements can be obtained by using sodium hypochlorite.

1. When sodium sulfide is removed by using caustic soda, Na ₂ S and NaSH generated by the reaction are reacted with sodium hypochlorite to form Na ₂ SO ₄ salt. Therefore, the problem of recycling to hydrogen sulfide is solved .

2. In addition, sodium hypochlorite has anti-scale effect due to oxidation and bleaching action, and it can remove untreated hydrogen sulfide.

3. Sodium hypochlorite reacts with strong alkaline Na ₂ S and NaSH with Na ₂ SO ₄ , so it does not interfere with pH control, preventing excessive use of chemicals and stable operation with high efficiency.

4. OCl- generated by decomposition of sodium hypochlorite in water has the effect of removing scale because it oxidizes.

5. With the above advantages, it is possible to reduce the maintenance cost of the drug during the treatment, and the high efficiency can be expected at the same cost.

Such a desulfurization treatment system of the present invention can be effectively used in a vehicle fuel, a city gas, a boiler, and a generator fuel in which hydrogen sulfide is generated.

1 is a schematic diagram of a biogas desulfurization system according to a first embodiment of the present invention;
Fig. 2 is a partially enlarged view of the primary treatment tank according to Fig. 1; Fig.
3 is a partially enlarged view of the secondary treatment tank according to FIG.
4 is a schematic diagram of a biogas desulfurization system according to a second embodiment of the present invention.
Fig. 5 is a partially enlarged view of the primary treatment tank according to Fig. 4; Fig.
Fig. 6 is a partially enlarged view of the secondary treatment tank according to Fig. 4; Fig.

Hereinafter, the biogas desulfurization system of the present invention will be described in detail with reference to the accompanying drawings.

As shown in the figure, the biogas desulfurization system includes a primary treatment tank 100 that receives biogas and contacts the caustic soda treatment water for primary treatment, a primary treatment tank 100 for supplying primary treatment gas discharged from the primary treatment tank 100 A secondary treatment tank 200 for supplying secondary caustic soda and sodium hypochlorite treated water in contact with the secondary treatment tank 200 and a caustic soda supply device for supplying caustic soda (NaOH) to the primary and secondary treatment tanks 200 A sodium hypochlorite supply device 400 for supplying sodium hypochlorite (NaOCl) to the secondary treatment tank 200, a water supply device 500 for supplying water to the primary and secondary treatment tanks 100 and 200 And a control unit 600 for maintaining the pH of the primary and secondary treatment baths 100 and 200.

In the biogas desulfurization system according to the present invention, hydrogen sulfide contained in the biogas can be removed by the following reaction formula by the first and second treatment vessels 100 and 200.

H2S + 2NaOH - > Na2S + 2H2O

Na2S + 4NaOCl - > Na2SO4 + 4NaCl

_{Na2S + NaOCl + H 2 O →} S + NaCl + 2NaOH

H2S + 2NaOH + 4NaOCl ----- > Na2SO4 + 2H2O + 4NaCl

Each component of the biogas desulfurization system will be described in detail below.

First, the first treatment tank 100 includes a first treated water storage tank 110 in which caustic soda treated water is stored, a second treated water storage tank 110 connected to the first treated water storage tank 110, A first caustic soda inlet 130 for supplying caustic soda into the inside of the first upper side of the first treated water storage tank 110, A biogas inflow part 150 for supplying the hydrothermal treatment water to the tank 110 and a caustic soda treatment water stored in the first treated water storage tank 110 are supplied and sprayed to be in contact with the biogas to supply hydrogen sulfide (H ₂ S) A first process gas discharge unit 170 for discharging the first process gas introduced into the first process water storage tank 110 to the outside, and a second process gas discharge unit 170 for storing the first process water A first pH sensor 180 for confirming the pH of the caustic soda treated water stored in the tank 110, It comprises a first water level sensor 181, a first treated water storage tank 110 is stored in one first processing water discharge portion 190 for discharging the tea to be treated to the outside in to determine caustic level of the soda treatment.

The second treatment tank 200 includes a second treated water storage tank 210 in which caustic soda treated water is stored therein and a second treated water tank 210 connected to the second treated water storage tank 210, A second caustic soda inlet 230 located at one inner side of the upper inner side of the second treated water storage tank 210 and supplying caustic soda to the inside of the second treated water storage tank 210, A sodium hypochlorite soda supply unit 240 which is located on the inner upper side and supplies sodium hypochlorite to the inside and a first process gas discharge unit 170 which is connected to the first process gas discharge unit 170 of the first process water storage tank 110, And the primary treatment gas introduced into the primary treatment tank 100 are supplied to the primary treatment gas inlet 250 and the secondary treatment water storage tank 210 to be supplied with sodium hydroxide and sodium hypochlorite treated water, by spraying so as to contact the residual hydrogen sulfide second biogas processing unit 260, and a second treated water storage tank 210 to remove the second (H ₂ S) A second process gas discharge unit 270 for discharging the process gas introduced into the second process water storage tank 210 to the outside, a second pH sensor 280 for confirming the pH of the stored caustic soda of the second process water storage tank 210 and the sodium hypochlorite- An ORP sensor 282 for confirming the ORP (redox potential difference) of the treated water, a second treated water storage tank 210 of caustic soda and sodium hypochlorite, And a second process water discharge unit 290 for discharging the secondary process water stored in the second process water discharge unit.

Meanwhile, the controller 600 receives the pH information of the caustic soda treated water from the first pH sensor 180 and supplies the caustic soda treated water to the first treated water storage tank 110 so that the pH of the caustic soda treated water is maintained at 8.5 to 10 A first controller 610 for adjusting the supply amount of water and caustic soda and a second pH sensor 280 for receiving the pH information of caustic soda + sodium hypochlorite treated water from the second pH sensor 280 to adjust pH of caustic soda + And a second controller 620 for controlling the amount of water, caustic soda, and sodium hypochlorite supplied to the second treated water storage tank 210 to maintain the ORP at 650 to 700.

1 and 2, in the first treatment tank 100 according to the first embodiment of the present invention, the biogas inflow section 150 is connected to the first biogas treatment section 160, 1 process gas outlet 170 is connected to one side of the first treated water storage tank 110. Accordingly, the first biogas treatment unit 160 injects the caustic soda treated water supplied through the first conveyance pipe 161 through the first nozzle (not shown) during the introduction of the biogas to remove the hydrogen sulfide (H ₂ S) is firstly removed. The injected caustic soda treated water falls back into the first treated water storage tank 110. The primary treated gas introduced into the first treated water storage tank is discharged through the first treated gas discharge portion 170 do.

1 and 3, the secondary treatment tank 200 according to the first embodiment of the present invention is configured such that the second biogas treatment unit 260 is provided with a primary treatment tank 100, A first process gas inlet 250 for supplying a process gas is connected and a second process gas outlet 270 is connected to one side of the second process water storage tank 210. Accordingly, the second biogas processing unit 260 injects the caustic soda / sodium hypochlorite treated water supplied through the second transfer pipe 261 through the second nozzle (not shown) when the first process gas is introduced The residual hydrogen sulfide (H ₂ S) contained in the primary process gas is secondarily removed. The injected caustic soda + sodium hypochlorite treated water falls again into the second treated water storage tank 210, and the secondary process gas introduced into the second treated water storage tank flows into the second process gas discharge unit 270 ).

4 and 5, the first treatment tank 100 according to the second embodiment of the present invention includes a first biogas treatment unit 160, a first process gas discharge unit 170, And the biogas inlet (150) is connected to one side of the first treated water storage tank (110). The first biogas treatment unit 160 supplies the caustic soda treatment water supplied through the first transfer pipe 161 to the first process gas discharge unit 170, And the hydrogen sulfide (H ₂ S) contained in the biogas is firstly removed.

4 and 5, in the second treatment tank 200 according to the second embodiment of the present invention, a second process gas discharge unit 270 is provided on the second biogas treatment unit 260 And the primary processing gas inlet 250 is connected to one side of the second treated water storage tank 210. [ The first process gas discharged from the first treatment tank is directly supplied to the second treated water storage tank 210 and the second biogas treatment unit 260 is supplied with the caustic soda supplied through the second transfer pipe 261 + Sodium hypochlorite treated water is injected into the primary process gas discharged to the second process gas discharge unit 270 to remove the residual hydrogen sulfide (H ₂ S) contained in the primary process gas secondarily.

<Examples>

A first treatment tank 100 in which caustic soda treatment water is stored and a secondary treatment tank 200 in which caustic soda and sodium hypochlorite treatment water are stored are installed in series and the first treated water 100 in the first treatment tank 100 The amount of water and caustic soda is adjusted so that the pH of the caustic soda treated water stored in the storage tank 110 is maintained at 8.5, 9.0, and 10.0 as shown below, Sodium hydroxide, sodium hydroxide, and water were adjusted so that the pH of the caustic soda / sodium hypochlorite-treated water stored in the water bath was adjusted to 8.0, 8.5, 9.5, and 9.0 as shown below. Then, the amount of sodium hypochlorite was adjusted so that ORP (oxidation-reduction potential difference) was maintained at 650, 680, 720, and 700 in the second treatment tank 200.

The content of H ₂ S contained in the biogas supplied to the first treatment tank 100 in which the caustic soda treatment water is stored and the second treatment tank 200 in which caustic soda and sodium hypochlorite treated water are stored, The content of H ₂ S contained in the process gas discharged from the treatment tank 200 was measured and the treatment efficiency of H ₂ S was calculated.

Experiment
collection Primary treatment tank
pH Secondary treatment tank
pH Secondary treatment tank
ORP Primary treatment group
H ₂ S inflow Secondary treatment group
H ₂ S emissions Treatment efficiency of H ₂ S One 8.5 8.0 650 780 0 100% 2 8.5 8.0 650 950 0 100% 3 9.0 8.5 680 1,050 2 99.8% 4 9.0 8.5 680 1,240 3 99.75% 5 10.0 9.5 720 2,100 2 99.9% 6 10.0 9.5 720 2,070 2 99.90% 7 10.0 9.0 700 1,790 One 99.94%

<Comparative Example>

Only the caustic soda was injected into both the first treatment tank 100 and the second treatment tank 200 used in the embodiment of the present invention to create an environment of the treatment tank in which only caustic soda treatment water was used as in the prior art. Treatment tank pH was equally adjusted on both passing a process gas containing 8.5, 9.0, was adjusted to 10.0, the same H ₂ S to the embodiment according to the experiment number, respectively the final removal efficiency of H ₂ S is discharged to Respectively.

Experiment
collection Primary treatment tank
pH Secondary treatment tank
pH Primary treatment group
H ₂ S inflow Secondary treatment group
H ₂ S emissions Treatment efficiency of H ₂ S One 9.5 9.5 700 200 74.02% 2 9.5 9.5 945 265 71.95% 3 10.0 10.0 1,060 300 71.69% 4 10.5 10.5 1,230 350 67.99% 5 11.0 11.0 2,110 680 68.77% 6 11.0 11.0 2,040 620 69.6% 7 11.0 11.0 1,750 550 68.57%

<Experimental Results>

As can be seen from Tables 1 and 2, it was confirmed that when only caustic soda treated water was used as in the prior art, the H ₂ S removal efficiency was about 68% to 74%. In particular, when H ₂ S is contained at a high concentration of about 1,700 or more, it can be seen that even when the concentration of caustic soda is increased to pH 11.0, the removal effect is about 70% or less.

On the other hand, when the primary treatment tank 100 storing the caustic soda treatment water and the secondary treatment tank 200 storing the caustic soda + sodium hypochlorite treated water are connected in series, 99.75% to 100% H ₂ S removal efficiency. In particular, even when H ₂ S is contained at a high concentration of about 1,700 or more, it can be seen that the removal efficiency is 99.75% or more even at pH 10.0.

On the other hand, sodium hypochlorite reacts Na ₂ S and NaSH with Na ₂ SO ₄ , so that it can be confirmed that the pH control can be maintained and the efficiency can be maintained even over time.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is to be understood that within the scope of the appended claims, various changes and modifications may be made.

100: Primary treatment tank 110: First treated water storage tank
120: first water supply unit 130: first caustic soda inlet
150: Biogas inflow section 160: First biogas processing section
170: first process gas outlet 180: first pH sensor
181: first water level sensor 190: first treated water discharge portion
200: Second treatment tank 210: Second treated water storage tank
230: Second caustic soda inflow section 240: Sodium hypochlorite supply section
250: primary treatment gas inflow part 260: second biogas treatment part
270: second process gas discharging portion 280: second pH sensor
281: second water level sensor 282: ORP sensor
290: second treated water discharge part 300: caustic soda supply device
400: sodium hypochlorite supply 500: water supply
600:

Claims (6)

A primary treatment tank 100 for supplying biogas to the caustic soda treatment water for primary treatment and a secondary treatment tank 100 for supplying primary treatment gas discharged from the primary treatment tank 100 to caustic soda + A caustic soda supply device 300 for supplying caustic soda to the primary and secondary treatment tanks 200 and a secondary treatment tank 300 for supplying secondary caustic soda to the secondary treatment tanks 200 The sodium hypochlorite supply device 400 for supplying sodium chlorate, the water supply device 500 for supplying water to the primary and secondary treatment baths 100 and 200 and the pH of the primary and secondary treatment baths 100 and 200 And a control unit (600)
The first treatment tank 100 is provided with a first treated water storage tank 110 in which caustic soda treatment water is stored therein and a first water supply unit 110 connected to the first treated water storage tank 110, A first caustic soda inflow part 130 located at an inner upper side of the first treated water storage tank 110 and supplying caustic soda to the inside of the first treated water storage tank 110, The first treated water storage tank 110 and the second treated water storage tank 110 are supplied with the biosynthetic water to be supplied to the first treated water storage tank 110 and the residual hydrogen sulfide H ₂ S is firstly removed A first process gas discharge unit 170 for discharging the first process gas introduced into the first process water storage tank 110 to the outside, A first pH sensor 180 for identifying the pH of the stored caustic soda treatment water of the first treated water storage tank 110, A first water level sensor 181 for checking the water level of the caustic soda treated water and a first treated water discharge portion 190 for discharging the first treated water stored in the first treated water storage tank 110 to the outside ,
The second treatment tank 200 includes a second treatment water storage tank 210 in which caustic soda treatment water is stored therein and a second water supply unit 210 connected to the second treatment water storage tank 210, A second caustic soda inflow part 230 located at an inner upper side of the second treated water storage tank 210 and supplying caustic soda to the inside of the second treated water storage tank 210, A sodium hypochlorite supply unit 240 for supplying sodium hypochlorite to the inside of the first process water storage tank 110 and a first process gas discharge unit 170 of the first process water storage tank 110 to supply the first process gas The first process gas inlet 250 and the caustic soda / sodium hypochlorite treated water stored in the second process water storage tank 210 are supplied to be contacted with the primary process gas discharged from the first process tank 100 A second biogas treatment unit 260 for secondarily removing residual hydrogen sulfide (H ₂ S) by spraying, a second biogas treatment unit 260 for removing residual hydrogen sulfide A second pH sensor 280 for confirming the pH of the caustic soda / sodium hypochlorite treated water stored in the second treated water storage tank 210, a second process gas discharge unit 270 for discharging the introduced process gas to the outside, An ORP sensor 282 for confirming the ORP (redox potential difference) of the treated water, and a second treated water storage tank 210 for caustic soda and sodium hypochlorite And a second treated water discharging part (290) for discharging the stored second treated water to the outside. delete The first treatment tank 100 is connected to the first biogas treatment unit 160 through the biogas inflow unit 150 and the first treatment gas discharge unit 170 is connected to the first treatment water storage tank 110,
The second treatment tank 200 is connected to the second biogas treatment unit 260 through a first treatment gas inlet 250 for supplying the first treatment gas discharged from the first treatment tank 100, And the gas discharge unit (270) is connected to one side of the second treated water storage tank (210). The first treatment tank 100 has a first treatment gas discharge unit 170 connected to an upper portion of the first biogas treatment unit 160 and a biogas inflow unit 150 connected to the first treatment gas discharge unit 170. [ And is connected to one side of the storage tank 110,
The second treatment tank 200 is connected to the second biogas treatment unit 260 through a second treatment gas discharge unit 270. The first treatment gas introduction unit 250 is connected to the second treatment water storage tank 210) is connected to one side of the biogas desulfurization system. The method according to any one of claims 1, 3, and 4, wherein the controller (600) controls the supply of water and caustic soda to the first treated water storage tank (110) so as to maintain the pH of the caustic soda treated water A first controller 610 for adjusting the pH and the ORP of the caustic soda / sodium hypochlorite treated water to a predetermined level, a water supply unit for supplying water and caustic soda of sodium hypochlorite to the second treated water storage tank 210 And a second control unit (620) for controlling the supply amount of the biogas desulfurization system.
[7] The method according to claim 5, wherein the first controller 610 maintains the pH of the caustic soda-treated water at 8.5 to 10, the second controller 620 maintains the pH of the caustic soda + sodium hypochlorite-treated water at 8.0 to 9.0 , And the ORP is controlled to be maintained at 650 to 700.

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