CN101821225A - Process for producing aromatic carboxylic acid - Google Patents

Abstract

A process for producing an aromatic carboxylic acid which comprises an oxidation step and a step in which a discharge gas generated in the oxidation step is burned, wherein the discharge gas, which contains methyl bromide, is burned while inhibiting the generation of a brominated dioxin. Specifically, the process for aromatic-carboxylic-acid production comprises: an oxidation step in which an alkylaromatic compound is oxidized in the presence of a bromine compound to obtain an aromatic carboxylic acid; and a step in which a discharge gas generated in the oxidation step is burned in a burner. In the process, the discharge gas is burned at a combustion temperature of 450-1,000 DEG C and the gas resulting from the combustion is cooled to 250 DEG C or lower. In the cooling step, the time required for cooling from 450 DEG C to 250 DEG C is 1 second or shorter.

Description

The manufacture method of aromatic carboxylic acid

Technical field

The present invention relates to the manufacture method of aromatic carboxylic acid.

Background technology

Aromatic carboxylic acids such as terephthalic acid are useful as synthesis material of polyester etc.As the typical example of aromatic carboxylic acid, the following method of employing that is manufactured in the industrial production of terephthalic acid is carried out: for example, contain in utilization under the situation of gas pressurization of molecular oxygen and make p-Xylol generation liquid-phase oxidation.Liquid-phase oxidation normally in oxidation reactor, utilize the solvent contain aliphatic carboxylic acids such as acetate, carry out in the presence of based on the heavy metal catalyst of cobalt, manganese and bromine compounds.

But in above-mentioned manufacture method, can from oxidation reactor, produce highly compressed waste gas.For example comprise in this waste gas: remaining oxygen; The unreacting material p-Xylol; Aliphatic carboxylic acid as solvent; Carbon monoxide, aliphatic carboxylic acid esters,, monobromethane as by product; Or the like.For waste gas, to be discharged in the atmosphere again after the recovery of useful component and energy, the harmless treatment of objectionable constituent etc. carrying out as required usually.

In exhaust gas constituents, be one of material that damages the ozone layer by monobromethane as the generations such as bromine compounds of catalyst aid.Therefore, do not wish the monobromethane in the waste gas is discharged in the atmosphere, it need be removed from waste gas.

As the treatment of waste gas method that contains monobromethane, what adopt usually is the method for carrying out burn processing.For example, propose a kind of gas, combustion adjuvant of containing molecular oxygen in the presence of catalyzer, supplied with and waited the method (patent documentation 1 and 2) of burning this waste gas., the difficult point of this method is: catalyst life is short, so the cost of off gas treatment is higher.

Based on this, following method has been proposed: the method (patent documentation 3) of in the heat storage type combustion stove, the waste gas that contains monobromethane being carried out burn processing with fuel.According to the method for patent documentation 3 record, can not use catalyzer and waste gas is carried out effective burn processing.

Patent documentation 1: TOHKEMY 2000-189753 communique

Patent documentation 2: Japanese Unexamined Patent Application Publication 2001-515576 communique

Patent documentation 3: TOHKEMY 2004-257606 communique

Summary of the invention

The problem that invention will solve

In recent years, the hazardous property of chloride dioxin is recognized more and more widely that the hazardous property of the brominated dioxin that produces for the burning that can follow bromo-containing substance is also troubling, therefore wishes to suppress the generation of brominated dioxin., in patent documentation 3, the inhibition of the brominated dioxin that produces for the burning of following monobromethane is in advance noting, also not have to put down in writing about the combustion conditions that can suppress its generation etc.

Based on this, the objective of the invention is to: the waste gas that produces in comprising oxidation step carries out carrying out burn processing in the manufacture method of aromatic carboxylic acid of step of burn processing when suppressing brominated generation of dioxin.

In addition, generally speaking, the concentration of monobromethane is low more, and then it is difficult to burning fully more, handles and also becomes difficult more.And in patent documentation 3,, the treatment of waste gas about the monobromethane that contains several ppm～such lower concentration of tens ppm is not studied only relevant for the waste gas that contains the 30ppm monobromethane of having an appointment being carried out the record of burn processing.

Based on this, the objective of the invention is to: the waste gas that produces in comprising oxidation step carries out in the manufacture method of aromatic carboxylic acid of step of burn processing the reluctant waste gas that contains the lower concentration monobromethane being carried out burn processing.

The method of dealing with problems

The inventor etc. further investigate for achieving the above object, found that: by under given conditions the waste gas that contains monobromethane being burnt, the problems referred to above are solved, and finished the present invention thus.

Main points of the present invention are as follows.

[1] a kind of manufacture method of aromatic carboxylic acid, this method comprises: in the presence of bromine-containing compound the alkyl aromatic compound oxidation is obtained the oxidation step of aromatic carboxylic acid and makes the waste gas that produces in this oxidation step carry out the incendiary step in combustion unit, wherein, make after this waste gas burns under 450～1000 ℃ temperature of combustion, below the gas cooling to 250 ℃ after the burning, and, in this process of cooling, from 450 ℃ of cooling times that are cooled to 250 ℃ be below 1 second.

[2] according to the manufacture method of [1] described aromatic carboxylic acid, wherein, be below 1 second the cooling time that is cooled to 250 ℃ from described temperature of combustion.

[3] according to the manufacture method of [1] or [2] described aromatic carboxylic acid, wherein, utilize heat storage that the gas after burning is cooled off.

[4] according to the manufacture method of each described aromatic carboxylic acid in [1]～[3], wherein, under the situation that does not have combustioncatalysts, burn.

[5] according to the manufacture method of each described aromatic carboxylic acid in [1]～[4], wherein, combustion unit is the heat-accumulation combustion device.

[6] according to the manufacture method of each described aromatic carboxylic acid in [1]～[5], wherein, the concentration of the brominated dioxin in the gas of cooling back is 1ng-TEQ/m according to the toxic equivalent meter ³Below.

[7] manufacture method of each described aromatic carboxylic acid in basis [1]～[6], wherein, oxidation step carries out in the aliphatic carboxylic acid solvent, and this manufacture method comprises: the slurry that contains aromatic carboxylic acid and solvent that obtains in oxidation step is carried out the solid-liquid separation step that solid-liquid separation obtains aromatic carboxylic acid filter cake and mother liquor; And at least a portion of this mother liquor is supplied to mother liquor recirculation step in the above-mentioned oxidation step.

[8] according to the manufacture method of [7] described aromatic carboxylic acid, wherein, be supplied to above-mentioned oxidation step more than the 50 weight % with mother liquor.

[9] according to the manufacture method of each described aromatic carboxylic acid in [1]～[8], wherein, the concentration of monobromethane is below the 100 volume ppm in the waste gas.

[10] according to the manufacture method of each described aromatic carboxylic acid in [1]～[9], wherein, alkyl aromatic compound is a p-Xylol.

[11] according to the manufacture method of each described aromatic carboxylic acid in [1]～[10], wherein, aromatic carboxylic acid is a terephthalic acid.

The effect of invention

According to the present invention, the waste gas that produces in comprising oxidation step carries out in the manufacture method of aromatic carboxylic acid of step of burn processing, there is following advantage: can under the situation that suppresses brominated dioxin generation, carry out burn processing, thereby alleviate burden to environment to the waste gas that contains monobromethane.

In addition, according to the present invention, can also carry out effective burn processing to the waste gas that contains the lower concentration monobromethane.

In addition, according to the present invention, since in a large number oxygen-containing gas such as air supply, need not sustainable supply be used for burnt fuel and can under the situation that does not have catalyzer, burn, so can carry out effective burn processing to the waste gas that contains monobromethane.Thereby, also have the advantage that can reduce operating cost and equipment cost, save energy.

In addition, according to the present invention, can also suppress the generation of NOX (oxynitride).

Therefore, according to the manufacture method of aromatic carboxylic acid of the present invention, can provide a kind of safe, environmental pressure is little, the manufacture method of low-cost and low energy consumption.

Description of drawings

Fig. 1 is the schema that an example of off gas treatment step of the present invention is shown.

Fig. 2 is the schema that an example of terephthalic acid manufacture method of the present invention is shown.

Fig. 3 is another routine schema that terephthalic acid manufacture method of the present invention is shown.

Nomenclature

1 oxidation step waste gas

2 solvents

3 absorption tower exit gass

The recovering liquid of 4 fatty family carboxylic acids

The recovering liquid of 5 fatty family carboxylicesterss

6 exit gass

7 combustion unit exit gass

8 absorption unit exit gass

11 pressurizing absorption towers

12 heat exchangers

13 gas expanders (Gas expander)

14 combustion units

15 absorption units

21 oxidation reactors

22 equipment for separating liquid from solid

23 washing units

24 solid-liquid separation/washing unit

25 drying installations

26 condensers

31 oxidation reactors

32 low temperature append oxidation reactor

33 pumps

34 well heaters

35 high temperature append oxidation reactor

36 put pressure evaporation (putting Ya Zheng development) device

37 equipment for separating liquid from solid

38 washing units

39 solid-liquid separation/washing unit

40 drying installations

41 oxidation reactor condensers

42 low temperature append the oxidation reactor condenser

43 high temperature append the oxidation reactor condenser

44 put pressure evaporation unit condenser

The A p-Xylol

B contains the gas of molecular oxygen

The C slurry

The D terephthalic acid cake

The E mother liquor

F terephthalic acid cake (cleaning the back)

G terephthalic acid coarse crystallization

H recirculation mother liquor

J discharges (purge) mother liquor

The K scavenging solution

L cleans waste liquid

M oxidation reactor waste gas (before the condensation)

The N phlegma

P oxidation reactor waste gas (after the condensation)

Q recirculation aliphatic carboxylic acid and ester class

The a p-Xylol

B contains the gas of molecular oxygen

The c slurry

D low temperature appends oxidation slurry

E high temperature appends oxidation slurry

The f terephthalic acid cake

The g mother liquor

H terephthalic acid cake (cleaning the back)

I terephthaldehyde acid crystal

J recirculation mother liquor

K discharges (purge) mother liquor

The l scavenging solution

M cleans waste liquid

N oxidation reactor waste gas (before the condensation)

The o phlegma

P oxidation reactor waste gas (after the condensation)

Q low temperature appends oxidation reactor waste gas (before the condensation)

The r phlegma

S low temperature appends oxidation reactor waste gas (after the condensation)

T high temperature appends oxidation reactor waste gas (before the condensation)

The u phlegma

V high temperature appends oxidation reactor waste gas (after the condensation)

W is put and is pressed evaporation unit waste gas (before the condensation)

The x phlegma

Y is put and is pressed evaporation unit waste gas (after the condensation)

Z recirculation aliphatic carboxylic acid and ester class

Embodiment

The manufacture method of aromatic carboxylic acid of the present invention is included in the bromine-containing compound existence and down the alkyl aromatic compound oxidation is obtained the oxidation step of aromatic carboxylic acid and makes the waste gas incendiary step in combustion unit that produces in this oxidation step, wherein, make after this waste gas burns under 450～1000 ℃ temperature of combustion, below the gas cooling to 250 ℃ after the burning, and, in this process of cooling, from 450 ℃ of cooling times that are cooled to 250 ℃ be below 1 second.

That is, the present invention can be by handling the generation that suppresses brominated dioxin to the waste gas that comprises monobromethane under specific burning and cooling conditions.

Below, manufacture method of the present invention is specifically described.It is pointed out that in following explanation do not having under the situation of particular determination, force value is represented absolute pressure, and described normal pressure is generally 0.101MPa.

The manufacture method of aromatic carboxylic acid of the present invention comprises the oxidation of alkyl aromatics at least and obtains the oxidation step of aromatic carboxylic acid and make the waste gas incendiary off gas treatment step in combustion unit that produces in this oxidation step, preferably further comprises solid-liquid separation step and mother liquor recirculation step.

Kind for the aromatic carboxylic acid that the present invention was suitable for there is no particular restriction, for example can enumerate: phthalic acid, m-phthalic acid, terephthalic acid, trimellitic acid (benzene tricarboxylic acid), 2,6-or 2,7-naphthalic acid, 4,4 '-biphenyl dicarboxylic acid etc.Wherein, the present invention preferably is applicable to the manufacturing of phthalic acid class (phthalic acid, m-phthalic acid, terephthalic acid etc.), especially preferably is applicable to the manufacturing of terephthalic acid.

Also do not have particular restriction for the alkyl aromatic compound as raw material, aromatic ring can be that monocycle also can be many rings.As alkyl, can enumerate for example methyl, ethyl, n-propyl and sec.-propyl etc.

As the specific examples of alkyl aromatic compound, for example can enumerate: dialkyl benzene and trialkyl benzene class, dialkyl group naphthalene and trialkyl naphthalene class and dialkyl group biphenyl and trialkyl biphenyl class.Preferred m-Diisopropylbenzene, p-Diisopropylbenzene, adjacent diisopropylbenzene(DIPB), o-isopropyl methylbenzene, an isopropyl toluene, cymene, o-Xylol, m-xylene, p-Xylol, Three methyl Benzene class, 2,6-or 2,7-dimethylnaphthalene, 2,6-diisopropylnaphthalene, 4,4 '-dimethyl diphenyl etc.Wherein and since have the alkyl of 2～4 carbonatomss such as methyl, ethyl, n-propyl and sec.-propyl 1～4 alkyl benzene, alkylnaphthalene class, and alkyl biphenyl class etc. have hyperergy, therefore preferred.

In addition, alkyl aromatic compound can also be by partial oxidation.Described partial oxidation compound be alkyl in the abovementioned alkyl aromatics through oxidation, be oxidized to aldehyde radical, acyl group, carboxyl or hydroxyalkyl etc., and the aromatic carboxylic acid degree of not oxidized one-tenth target and the compound that obtains.Particularly, for example can enumerate: 4-carboxyl benzaldehyde (below be called " 4CBA "), 3-tolyl aldehyde, 4-tolyl aldehyde, meta-toluic acid, paratolunitrile, p-tolualdehyde, 3-formyl radical phenylformic acid, 4-formyl radical phenylformic acid and 2-methyl-6-formyl radical naphthalene class etc.

These raw materials can be used alone, and also can will be used in combination more than 2 kinds.

To sum up,, preferably use xylene (o-Xylol, m-xylene, p-Xylol), especially preferably use p-Xylol as raw material.When using p-Xylol,, for example can enumerate as the aromatics that has through the alkyl of partial oxidation as raw material: 4CBA, p-tolualdehyde, paratolunitrile etc., and, will obtain terephthalic acid as aromatic carboxylic acid.

Below, be example with the manufacture method of using p-Xylol to obtain terephthalic acid as raw material, describe at oxidation step (I), solid-liquid separation step (II), mother liquor recirculation step (III), off gas treatment step (IV), and when making other aromatic carboxylic acid, also can similarly make through suitably changing.

＜oxidation step (I) 〉

In oxidation step (I), in the presence of bromine-containing compound, alkyl aromatic compound is carried out oxidation and obtain aromatic carboxylic acid.For example can enumerate: in oxidation reactor, utilize the gas contain molecular oxygen to make alkyl aromatic compound oxidation in solvent, thereby to obtain with aromatic carboxylic acid and solvent be the slurry of principal constituent as raw material.In above-mentioned oxidation step (I), aforesaid oxidizing reaction (oxide treatment) can only be carried out once, also can carry out repeatedly.Need to prove that for the situation of carrying out repeatedly oxidizing reaction (oxide treatment), its condition can be identical with initial oxidizing reaction (oxide treatment), also can be different.

When the target product aromatic carboxylic acid is terephthalic acid, use p-Xylol as raw material usually, but just as described above, except p-Xylol, raw material can also comprise intermediate or impurity such as paratolunitrile, p-tolualdehyde, 4CBA.In oxidation step (I), the above p xylene oxidation of preferred 90 weight % becomes terephthalic acid, and more preferably the above p xylene oxidation of 95 weight % becomes terephthalic acid.

As solvent, be principal constituent usually with the aliphatic carboxylic acid.Aliphatic carboxylic acid there is no particular restriction, but any carboxylic acid in preferred acetate, propionic acid, formic acid and the butyric acid.Need to prove that described " principal constituent " is meant the above composition of 60 weight % that accounts for the solvent total amount.Wherein, from solvability, boiling point, and the processing ease aspect consider, preferably be the solvent of principal constituent with acetate.The mixture of acetate and water most preferably.As the ratio of acetate and water, with respect to acetate 100 weight parts, the amount of water is generally more than 1 weight part, is preferably more than 5 weight parts, and, be generally below 40 weight parts, be preferably below 25 weight parts, more preferably below 15 weight parts.Is below the above-mentioned higher limit by making water for the amount of acetate, reaction efficiency is improved, is more than the above-mentioned lower value by making water for the amount of acetate, can suppress acetate thermolysis takes place when oxidizing reaction, in the scope of above-mentioned higher limit and lower value, can seek aspect energy, economic aspect is saved the energy, and is therefore preferred respectively.

With respect to alkyl aromatic compound 100 weight parts as raw material, the amount that makes solvent usually is more than 100 weight parts, is preferably more than 200 weight parts, and makes the amount of solvent be below 600 weight parts, be preferably below 400 weight parts usually.By the amount that makes solvent is more than the above-mentioned lower value, the concentration of the slurry that obtains in the oxidizing reaction can be adjusted at suitable degree, therefore is difficult in pipeline etc. unfavorable conditions such as generation obstruction.And, be below the above-mentioned higher limit by the amount that makes solvent, can realize the miniaturization of equipment, be preferred with regard to the cost aspect therefore.

The mother liquor that preferably will reclaim from solid-liquid separation step described later (II) in addition, utilizes as the part of the solvent that is used for oxidation step (I) use again.

As the gas that contains molecular oxygen, get final product so long as contain the gas of the oxygen of molecularity, for example, can use air, oxygen-rich air, by the oxygen of non-active gas dilution etc.Wherein, cost is lower during owing to the use air, has practicality, and is therefore preferred.With regard to the feed rate of the gas that contains molecular oxygen,, be generally 3～100 times of moles in molecular oxygen with respect to alkyl aromatic compound as raw material.

The manufacture method of aliphatic carboxylic acid of the present invention has the oxidation step that thereby the alkyl aromatic compound oxidation is obtained aromatic carboxylic acid in the presence of bromine-containing compound.Here, there is no particular restriction, for example can enumerate, the bromide of the heavy metal as catalyzer described later or as bromine-containing compound of catalyst aid etc. for said bromine-containing compound.

In the oxidation step of alkyl aromatic compound, to use catalyzer usually.As catalyzer,, then do not have particular restriction, but use heavy metal compound usually, and use bromine-containing compound as catalyst aid so long as have the alkyl aromatic compound oxidation and change into the material of the ability of aromatic carboxylic acid.In addition, in order to promote reaction, can also be used in combination co-oxidants.

As the heavy metal element in the heavy metal compound, for example can enumerate: cobalt, manganese, nickel, chromium, zirconium, copper, lead, hafnium, cerium etc.They can use separately, also can be used in combination.Especially preferably cobalt and manganese are used in combination.As such heavy metal compound, for example can enumerate: the acetate of heavy metal, nitrate, acetylacetonate, naphthenate, stearate, bromide etc.Wherein, the acetate or the bromide of preferred heavy metal.

As bromine-containing compound as catalyst aid, for example can enumerate: inorganic bromine compoundss such as molecular state bromine, hydrogen bromide, Sodium Bromide, Potassium Bromide, cobaltous bromide and Manganese dibromide, organbromine compounds such as monobromethane, methylene bromide, methenyl bromide, bromotoluene, Monobromoxylene, ethylene dibromide, tribromoethane and tetrabromoethane etc.These bromine-containing compounds both can use separately, also can use with the form of the mixture more than 2 kinds.

Catalyst concentration if can promotes oxidn the scope of reaction, there is no particular restriction, but as the heavy metal concentration in the solvent, usually make its concentration be 10ppm above, be preferably 100ppm above, more preferably more than the 200ppm, and make usually its concentration be 10000ppm following, be preferably 5000ppm following, more preferably below the 3000ppm.By making the heavy metal concentration in the solvent is more than the above-mentioned lower value, can improve speed of response, therefore preferred.In addition, be below the above-mentioned higher limit by making the heavy metal concentration in the solvent, can when suppressing cost, reduce heavy metal concentration, bromine concentration in waste liquid, the waste gas, therefore from the environment aspect, secure context considers it is preferred.

When the catalyzer that uses is when being used in combination the catalyzer of heavy metal compound and bromine-containing compound, with respect to 1 mole of heavy metal atom, usually to make bromine atoms be more than 0.05 mole, be preferably more than 0.1 mole, more preferably more than 0.5 mole, and to make bromine atoms usually be below 10 moles, be preferably below 7 moles, more preferably below 5 moles.The mol ratio that makes heavy metal compound and bromine-containing compound has the advantage that can improve catalyst activity in above-mentioned scope the time.

For being the situation that raw material obtains terephthalic acid with the p-Xylol, as catalyzer, preferably use at least a kind in cobalt compound and the manganic compound, as catalyst aid, preferably use bromine-containing compound.Especially preferably adopt the combination of cobaltous acetate, manganous acetate, hydrogen bromide.

When using cobalt compound, manganic compound, and bromine-containing compound during as catalyzer, the consumption of each compound is as follows.That is, with respect to solvent, make usually cobalt (being converted into metal) be 10 ppm by weight above, be preferably 100 ppm by weight above, more preferably more than 200 ppm by weight, and make usually cobalt be 2000 ppm by weight following, be preferably below 1000 ppm by weight.Usually make manganese (being converted into metal) be more than 1 ppm by weight, be preferably more than 5 ppm by weight, and make manganese be below 1000 ppm by weight, be preferably below 500 ppm by weight usually with respect to solvent.Usually make bromine (being converted into bromo element) be more than 10 ppm by weight, be preferably more than 100 ppm by weight, and make bromine be below 3000 ppm by weight, be preferably below 2000 ppm by weight usually with respect to solvent.

In order to improve the reaction efficiency of oxidizing reaction, the pressure that makes oxidation step is to make solvent and can keep under the temperature of reaction more than the liquid pressure as the mixture of the alkyl aromatic compound of raw material.Here said maintenance is liquid, is meant to have liquid phase at least.

Usually make the pressure of oxidation step be higher than normal pressure, be preferably 0.2MPa above, more preferably more than the 0.4MPa, and make usually the pressure of oxidation step be 10MPa following, be preferably 7MPa following, more preferably 5MPa following, more preferably below the 3MPa.Be this scope by the pressure that makes oxidation step, can suppress the decomposition of side reaction and compound, have and to suppress the advantage that yield descends.In addition, the pressure suppression of oxidation step during alap level, can used the low reactor of compressive strength in above-mentioned scope, thus cost-saved.

With regard to the temperature of reaction (temperature of oxidizing reaction) of oxidation step (I), usually to make this temperature be more than 100 ℃, be preferably more than 140 ℃, more preferably more than 150 ℃, more preferably more than 170 ℃, and to make this temperature usually be below 300 ℃, be preferably below 250 ℃, more preferably below 230 ℃, more preferably below 210 ℃.Be controlled at above-mentioned scope by temperature, but fast reaction speed, improve yield oxidizing reaction.Be controlled at above-mentioned scope by temperature, can suppress the solvent loss that causes because of burning, can also suppress the decomposition of side reaction and compound, therefore have and suppress the advantage that yield reduces oxidizing reaction.

When carrying out continuously, oxidizing reaction can enhance productivity, therefore preferred, the reaction times (average retention time) of this moment is preferably more than 20 minutes, more preferably more than 30 minutes, more preferably more than 40 minutes, and be preferably below 300 minutes, more preferably below 150 minutes, more preferably below 120 minutes.Reaction times is above-mentioned lower value when above, can react fully and carry out, and can obtain highly purified aromatic carboxylic acid.Reaction times is above-mentioned higher limit when following, can suppress the solvent loss that causes because of burning, and can reduce cost.In addition, consider it also is preferred from the capacity angle that can reduce reactor.

Kind for the reactor that can use in oxidation step (I) there is no particular restriction, can use known in the past reactor.For example, can use the reactor of any types such as reactor, bubbling column reactor, piston flow pattern (pipeline circulation type) reactor of band stirrer, in order to improve reaction efficiency, preferably with the tank reactor of mixing fully of stirrer.The supplying opening of the gas that contains molecular oxygen will be set in the bottom of reactor usually.

The gas of giving from the underfeed confession of reactor that contains molecular oxygen is discharged from the top of tower of reactor with the form of the gas that contains a large amount of solvent vapours after the oxidizing reaction that is used for as the alkyl aromatic compound of raw material.Subsequently, expellant gas mainly separates solvent by condenser, distillation tower etc., and rest part is discharged as waste gas.The solvent that is separated is preferably being undertaken turning back in the oxidation reactor after the partial dehydration by distillation etc. again.By removing the moisture in desolvating, can suppress the increase of moisture in solvent that produces as the by product of oxidizing reaction.

There is no particular restriction for the oxygen concn in the waste gas, usually wish this concentration of control is 1.0 volume % above, be preferably 1.5 volume % above, more preferably more than the 2.0 volume %, and wish usually this concentration of control be 8.0 volume % following, be preferably below the 7.0 volume %.When the oxygen concn in the waste gas is above-mentioned lower value when above, has the advantage of the reaction efficiency (efficiency of combustion of monobromethane) in the time of can improving the aftermentioned waste-gas burning.Oxygen concn in the waste gas is above-mentioned higher limit when following, can improve security.And the oxygen concn in the waste gas is in the scope of above-mentioned higher limit and lower value the time, can be directly to heat-accumulation combustion unit feeding described later, and therefore preferred.

Need to prove, in oxidation step of the present invention (I), can after above-mentioned oxidizing reaction, append oxide treatment as required.The described oxide treatment of appending is meant: for the reaction mixture that obtains in the above-mentioned oxidizing reaction, no longer carry out raw material supplying, and further carry out oxide treatment by the gas that supply contains molecular oxygen.

The preferred embodiment that appends oxide treatment is under the low temperature that is lower than initial oxidizing reaction temperature reaction mixture to be appended oxide treatment (hereinafter referred to as " low temperature appends oxidation ").Preferably make low temperature append the temperature of oxidation than low 1～20 ℃ of initial oxidizing reaction.More preferably make temperature low more than 5 ℃, further preferably make temperature low below 15 ℃.By making temperature that low temperature appends oxidation, can suppress the decomposition of side reaction and compound in above-mentioned scope.The pressure that low temperature appends oxidation remains on more than the liquid pressure for can make the internal mix thing at least under temperature of reaction, is preferably 0.2～10MPa.The pressure that more preferably makes low temperature append oxidation is below the 5MPa.By the pressure that makes low temperature append oxidation is below the above-mentioned higher limit, can suppress the decomposition of side reaction and compound, and then can suppress yield and reduce.Usually, preferably with pressure-controlling at the pressure that is lower than initial oxidizing reaction.Low temperature appends oxide treatment preferably to carry out continuously, and preferably to make its reaction times be 5 minutes～150 minutes.

Append the gas that contains molecular oxygen that oxide treatment is supplied with for carrying out low temperature, can use and the initial identical gas of oxidizing reaction.Feed rate with respect to the molecular oxygen that is used for initial oxidizing reaction, with the amount of raw material alkyl aromatic compound is that the feed rate of the molecular oxygen of benchmark is preferably (volume ratio more than 1/10000, down with), more preferably more than 1/1000, more preferably more than 1/100, and be preferably below 1/5, more preferably below 1/10.

Need to prove that the preferable range of the oxygen concn in the waste gas of discharging and reason thereof are identical with above-mentioned oxidizing reaction after low temperature appends oxide treatment.

Other preferred embodiment that appends oxide treatment is under the high temperature that is higher than initial oxidizing reaction temperature reaction mixture to be appended oxide treatment (hereinafter referred to as " high temperature appends oxidation ").Append oxide treatment by carrying out high temperature, the part of the aromatic carboxylic acid particle in the slurry that is obtained by initial oxidizing reaction can be dissolved in the solvent.Thus, particle interior oxidation intermediate (impurity of not oxidized one-tenth target product aromatic carboxylic acid) is oxidized, and the purity of the aromatic carboxylic acid that obtains improves.It is higher 1～150 ℃ than initial oxidizing reaction preferably to make high temperature append the temperature of oxidation.More preferably high more than 30 ℃, further preferred high more than 50 ℃ than initial oxidizing reaction.In addition, preferably high below 100 ℃, more preferably high below 80 ℃ than initial oxidizing reaction.

For being the situation that raw material obtains terephthalic acid with the p-Xylol, particularly, the temperature of reaction that preferably makes high temperature append oxidation is more than 235 ℃, more preferably more than 240 ℃, and be preferably below 290 ℃, more preferably below 280 ℃.By the temperature of reaction that makes high temperature append oxidation is more than the above-mentioned lower value, terephthaldehyde's acid particles is become be easy to dissolving, thereby show the tendency that purity improves.On the other hand, be below the above-mentioned higher limit by the temperature of reaction that makes high temperature append oxidation, can demonstrate the tendency of the generation that suppresses tint permanence impurity.

The pressure that high temperature appends oxidation remains on more than the liquid pressure for can make the internal mix thing at least under temperature of reaction, be preferably 0.5MPa above, more preferably 1MPa above, more preferably more than the 3MPa, and, be generally below the 10MPa.By the pressure that makes high temperature append oxidation is below the above-mentioned higher limit, can suppress the decomposition of side reaction and compound, and then can suppress yield and reduce.Usually, preferably high temperature is appended the pressure-controlling of oxidation at the pressure that is lower than initial oxidizing reaction.High temperature appends oxide treatment preferably to carry out continuously, and preferably makes its reaction times at 5 minutes～150 minutes.

Append the gas that contains molecular oxygen that oxide treatment is supplied with for carrying out high temperature, can use the gas identical with initial oxidizing reaction.Amount with respect to the aromatic carboxylic acid in the slurry, with the amount of raw material alkyl aromatic compound is that the feed rate of the molecular oxygen of benchmark is preferably 0.003 times more than the mole, more preferably 0.01 times more than the mole, and be preferably 0.3 times of mole following, more preferably 0.1 times below the mole.Be controlled to be more than the above-mentioned lower value by feed rate, append the tendency that oxidation effectiveness has raising molecular oxygen.In addition, be controlled to be below the above-mentioned higher limit, can demonstrate and suppress solvent incendiary tendency in the presence of oxygen by feed rate with molecular oxygen.

Need to prove that in order to suppress the solvent burning, the oxygen concn in the waste gas of discharging after high temperature appends oxide treatment is preferably lower concentration, preferred oxygen concentration is the scope of 0～0.5 volume %.

The above-mentioned oxide treatment of appending can be carried out more than 2 times.For example, can carry out low temperature and append oxidation more than 2 times, also can carry out low temperature append oxidation and high temperature append oxidation each more than 1 time, can also carry out high temperature and append oxidation more than 2 times.In the present invention, preferably append oxide treatment more than 1 time.

The slurry that contains the aromatic carboxylic acid that obtains in the above-mentioned oxidation step (I) through after the intermediate process steps, is being sent to solid-liquid separation step (II) as required usually.Intermediate process steps is not must be through step, and, also can carry out a plurality of intermediate process steps.As intermediate process steps, can for example enumerate cool off, heat, boost, step-down, concentrate, cell processing such as dilution, precipitation, interpolation, as typical processing, can carry out crystal and separate out or dissolve.For example, improve the situation of the rate of recovery of target product aromatic carboxylic acid, carry out crystal and separate out for needs; When desire improves purity, dissolve.Above-mentioned intermediate process steps can wait suitably according to the product quality of the kind of the aromatic carboxylic acid of target and target and select.

Carrying out crystal when separating out as intermediate process steps, usually by separate out at crystal that the pressure that makes slurry in the groove reduces and cooling to make with the aromatic carboxylic acid be that the crystal of principal constituent is separated out.It can be 1 that crystal is separated out groove, but preferably in series is provided with a plurality ofly, divides a plurality of stages to carry out crystal and separates out.But, when depressing when carrying out solid-liquid separation step (II) adding subsequently, the crystal of also preferably not following pressure to reduce is separated out sometimes.Need to prove that in the present invention, described adding depresses or pressurized state, refer to above non-pressurized pressure.

＜solid-liquid separation step (II) 〉

The slurry that obtains through oxidizing reaction preferably is sent to solid-liquid separation step (II) subsequently, and is separated into the filter cake and the mother liquor of aromatic carboxylic acid.Solid-liquid separation step (II) can be under normal pressure, add under the random order under depressing, reducing pressure and carry out, but preferably carries out under normal pressure or pressurized state.More preferably under pressurized state, carry out.

If under pressurized state, carry out solid-liquid separation, then can obtain interior filter cake that can be big, be easy to carry out the drying of filter cake.The slurry wall pressure that preferably makes equipment for separating liquid from solid be 0.2MPa above, more preferably more than the 0.3MPa, and make usually this pressure be 5MPa following, be preferably 3MPa following, more preferably 2MPa following, more preferably 1.5MPa following, especially be preferably below the 1.2MPa.Be controlled under the pressure lower in the above-mentioned scope by slurry wall pressure, can reduce the resistance to pressure of equipment for separating liquid from solid, thereby can save the construction cost of equipment equipment for separating liquid from solid.

Solvent is a principal constituent in the mother liquor that obtains through solid-liquid separation, and comprises dissolved aromatic carboxylic acid, unreacted alkyl aromatic compound, catalyzer, by product, water etc.Wherein, described principal constituent is meant, accounts for the above composition of 60 weight % in the total amount.In addition, also be attached with mother liquor in solid-liquid separation on the filter cake of gained.Therefore, in order to prevent the purity drop of aromatic carboxylic acid, preferably clean.Scavenging solution does not then have particular restriction so long as be in the liquid of liquid state under the pressure in equipment for separating liquid from solid, temperature condition, use usually with solvent phase with compound, can use acetate, water etc.Owing to be dissolved with aromatic carboxylic acid in the waste liquid after cleaning, therefore,, preferably it reclaimed or recirculation in order to prevent the loss of aromatic carboxylic acid.Waste liquid recirculation after the cleaning can be: be recycled in the arbitrary steps in oxidation step (I), intermediate process steps, the solid-liquid separation step (II).

In the amount of scavenging solution and the filter cake weight ratio of solids component be preferably more than 0.03, more preferably more than 0.05, more preferably more than 0.1, and be preferably below 5.0, more preferably below 4.0, more preferably below 3.0.For fear of scavenging solution generation bumping, preferably making the pressure in the equipment for separating liquid from solid that imports scavenging solution is more than the vapour pressure of scavenging solution.The difference of the vapour pressure of scavenging solution pressure in the equipment for separating liquid from solid when cleaning more preferably 0.01MPa above, more preferably more than the 0.02MPa, and be preferably 2.0MPa following, more preferably 1.0MPa following, more preferably below the 0.5MPa.

As equipment for separating liquid from solid, can use known equipment for separating liquid from solid, but owing to when using in the time of can carrying out solid-liquid separation and clean the device of these two kinds of operations operation is simplified, therefore preferred.As such device, for example can enumerate: screen bowl centrifuge, screw settling centrifuge, vacuum rotary filter, horizontal band filter, rotation pressure filter etc.Wherein, preferably can under pressurized state, carry out the device of solid-liquid separation, particularly, preferred screen bowl centrifuge, screw settling separating machine, rotation pressure filter.

Through solid-liquid separation, and the filter cake that carried out as required cleaning in the liquid containing ratio be generally 50 weight % following, be preferably 30 weight % following, more preferably 20 weight % following, be preferably below the 15 weight % especially, and be generally 0.5 weight % above, be preferably more than the 1 weight %.This filter cake is sent to drying step, can obtain the aromatic carboxylic acid crystallization.The aromatic carboxylic acid crystallization of gained can be as required further by comprising that hydrogenation step, crystal separate out the purifying process of step, solid-liquid separation step, drying step etc. and obtain more highly purified aromatic carboxylic acid.

＜mother liquor recirculation step (III) 〉

In manufacture method of the present invention, preferably has mother liquor recirculation step (III).Mother liquor recirculation step (III) is that the part of the mother liquor that will obtain in the solid-liquid separation step (II) is supplied to the step that oxidation step (I) utilizes again.It is pointed out that the mother liquor that obtains in the solid-liquid separation step (II) also can be recycled to above-mentioned intermediate process steps, solid-liquid separation step (II), but these steps are not included in the mother liquor recirculation step (III).

According to inventor's etc. research as can be known: when carrying out mother liquor recirculation step (III), the monobromethane concentration in the waste gas of oxidation step (I) can be reduced to several ppm～tens ppm.Its reason is still very not clear and definite, but infers that its reason may be: by catalyst component contained in the mother liquor is recycled in the oxidation step (I), can improve the catalyst activity in the reaction system, the decomposition that suppresses bromine-containing compound and the generation of monobromethane.In addition,, can also make yield raising to the aromatic carboxylic acid of whole technology by carrying out the mother liquor recirculation step, therefore preferred.

For the situation with mother liquor recirculation step (III), { (recirculation mother liquor weight/mother liquor gross weight) * 100} is preferably above, the 70 weight % more preferably of 50 weight % to the recirculation rate of mother liquor.Recirculation rate is high more, then has the advantage of the monobromethane concentration that can reduce in the waste gas.Recirculation rate also can be 100 weight %, but is preferably below the 95 weight %, more preferably below the 90 weight %.By making recirculation rate in above-mentioned scope, existence can suppress impurity accumulating in system, thereby has the advantage of raising as the quality of the aromatic carboxylic acid of product.

As required, the mother liquor that obtains in solid-liquid separation step (II) is divided into the recirculation mother liquor and discharges mother liquor, and the recirculation mother liquor is supplied to oxidation step (I) after being accumulated in the mother liquor tank etc.Can control recirculation rate by the amount of discharging mother liquor is regulated.For discharging mother liquor, after useful components such as solvent, catalyzer are reclaimed that it is discarded usually.

The recirculation mother liquor preferably is recycled to oxidation step (I) under pressurized state.Particularly, for example carry out institute such as oxidation step (I), solid-liquid separation step (II) in steps adding to depress, under the situation that keeps this pressurized state, the mother liquor that obtains is turned back to oxidation step (I) again.Also can pressurize again to the step in the way as required.So, the recirculation mother liquor can keep pressurization, the condition of high temperature, can turn back to oxidation step (I) under the situation that keeps high activity of catalyst, thereby has the advantage that can further reduce the monobromethane concentration in the waste gas.In addition, can also save and be used for the required energy of heating again at the mother liquor of oxidation step (I) recirculation, therefore preferred.

Therefore, the pressure of mother liquor that carries out recirculation is identical with the slurry wall pressure of above-mentioned equipment for separating liquid from solid, preferably make this pressure be 0.2MPa above, more preferably more than the 0.3MPa.Remain on high level by pressure, the recirculation mother liquor can be remained on high temperature the recirculation mother liquor.On the other hand, make usually the pressure of recirculation mother liquor be 5MPa following, be preferably 3MPa following, more preferably 2MPa following, further following for preferred 1.5MPa, especially be preferably below the 1.2MPa.The pressure of the mother liquor by reducing recirculation can use the low slightly device of resistance to pressure, thereby can save cost.

＜off gas treatment step (IV) 〉

Then, in conjunction with Fig. 1 the preferred implementation of off gas treatment step of the present invention (IV) is described.

In oxidation step (I), use the condenser that links to each other with oxidation reactor to cool off usually from the gas that oxidation reactor is emitted.Condensation products such as solvent are back in the oxidation reactor, and remaining gas is discharged with the form of oxidation step waste gas 1.Also can adopt distillation tower to wait and replace above-mentioned condenser.When having low temperature when appending oxidation or high temperature and appending the step of oxidation, come from this gas that appends oxidation reactor and handle similarly, become oxidation step waste gas 1.These waste gas can carry out individual treated, also can merge processing.

The composition that contains in the waste gas is generally solvent, unreacting material, oxygen, by product etc.Waste gas is generally high pressure, be preferably 0.2MPa above, more preferably more than the 0.4MPa, and be generally 5MPa following, be preferably 3MPa following, more preferably below the 2MPa.Waste gas is normally carrying out after the recovery of Separation and Recovery, pressure and the hot homenergic of the various useful components that contained etc., and burning is carried out innoxiously in combustion unit, is discharged into the outside then.

When with the p-Xylol being raw material when obtaining terephthalic acid, the composition that contains in the waste gas comprises: as the aliphatic carboxylic acids such as acetate of solvent; P-Xylol as unreacting material; As the aliphatic carboxylic acid esters,s such as methyl acetate of by product, monobromethane, carbon monoxide, carbonic acid gas etc.The content of various compositions is in the waste gas: for example, aliphatic carboxylic acid and ester class thereof are below the 10 volume %, and oxygen is below the 8 volume %, the total amount of carbon monoxide and carbonic acid gas is below the 6 volume %, monobromethane is below the 25 volume ppm, and p-Xylol is below the 20 volume ppm, or the like.

At first, oxidation step waste gas 1 is imported to the bottom of pressurizing absorption tower 11,, the dissolving of aliphatic carboxylic acid and ester class thereof is absorbed in the solvent 2, thereby this oxidation step waste gas 1 is removed from waste gas simultaneously from top donor solvent 2.Structure for pressurizing absorption tower 11 there is no particular restriction, can use various devices such as packed tower, spray tower, wet-wall tower, preferred packed tower.As solvent 2, make water usually.

Aliphatic carboxylic acid is absorbed on the tower top of pressurizing absorption tower 11, utilizes the aliphatic carboxylic acid dissolving of this absorption to absorb the ester class in the tower bottom.In addition, contain the liquid 5 that reclaims the aliphatic carboxylic acid esters,, discharge by midsection and contain the liquid 4 that reclaims aliphatic carboxylic acid, discharge absorption tower exit gas 3 from cat head by discharging at the bottom of the tower.

To contain the liquid 5 that reclaims the aliphatic carboxylic acid esters, and send back to oxidation step (I) when utilizing again, owing to can keep equal amount, thereby can suppress further by-product ester class, therefore preferred.

To contain the liquid 4 that reclaims lipid acid and send back to oxidation step (I) when utilizing again, but the solvent loss in the inhibited oxidation step is therefore preferred.It is pointed out that when containing water in the solvent 2, send back to oxidation step (I) after preferably in dehydration tower, dewatering again.

Absorption tower exit gas 3 still remains on high pressure conditions, therefore preferably its pressure energy is reclaimed, utilizes.As recovery method, comprise waste gas is carried out after the burn processing with the method for recovered energies such as various turbines and with the method for carrying out burn processing behind the recovered energies such as gas expander etc., when considering the power loss of burn processing step, the preferred latter.

Particularly, after being heated to about 150～160 ℃, carry out energy recovery, carry out burn processing with 14 pairs of expellant gas tube expanders of combustion unit exit gas 6 again with gas expander 13 with heat exchanger 12.The energy that utilizes gas expander 13 to reclaim can be used as the power of the air compressor that uses or is used for generator as required in oxidation step (I), thereby can carry out effective energy utilization.

Owing to comprise hazardous property gases such as carbon monoxide, monobromethane in the gas expander exit gas 6, therefore will after harmless treatment, discharge into the atmosphere again.In containing composition, the processing of monobromethane is difficulty the most, will carry out burn processing in the presence of catalyzer or in the presence of the catalyst-free usually., the burn processing cost height that in the presence of catalyzer, carries out, and on the other hand, need big energy when burning under catalyst-free exists.In addition, the monobromethane concentration in the waste gas is low more, then is difficult to carry out sufficient burn processing more.In addition, monobromethane can generate bromine or hydrogen bromide when carrying out burn processing, also exists according to combustion conditions and further with carbon monoxide or generate the possibility of brominated dioxin as the reactions such as aromatics of combustionresidue.

Need to prove that the monobromethane in the waste gas is considered to owing to as the heavy metal bromide of catalyzer, produce with generation side reactions such as solvents in oxidation step (I) as the bromine-containing compound of catalyst aid.

In view of the above problems, in the present invention, use combustion unit that waste gas is carried out burn processing, and be specified conditions its burn processing term restriction.

There is no particular restriction for the monobromethane concentration in the waste gas that is supplied to combustion unit 14, waste gas as oxidation step in aromatic carboxylic acid is made, be generally 100 volume ppm following, be preferably 50 volume ppm following, more preferably below the 29 volume ppm, and be generally 1 volume ppm above, be preferably 2 volume ppm above, more preferably more than the 3 volume ppm.If the monobromethane concentration in the waste gas is lower than above-mentioned lower value, then can increase the difficulty of burn processing, can reduce the necessity of harmless treatment simultaneously.

In order to reduce the monobromethane concentration in the waste gas, preferably improve the catalyst activity in the oxidation step (I).There is no particular restriction for the method that improves the catalyst activity in the oxidation step (I), particularly, can enumerate: improve the method for the concentration of cobalt in the reaction solution, the bromine concentration in the reaction solution is reduced to the method that does not make catalyst inactivation, the method that improves the mother liquor recirculation rate in mother liquor recirculation step (III) etc.

Wherein, in mother liquor recirculation step (III), preferably make the mother liquor recirculation rate be 50 weight % above, be preferably 70 weight %.By making the mother liquor recirculation rate in above-mentioned scope, can reduce the monobromethane concentration in the waste gas, can make monobromethane concentration is below the 29 volume ppm, more preferably below the 25 volume ppm.In addition, by making cobalt concentration, the bromine concentration in the reaction solution, the mother liquor recirculation rate optimization in the reaction solution, can make monobromethane concentration is below the 20 volume ppm, more preferably below the 15 volume ppm.

There is no particular restriction for the oxygen concn in the waste gas that supplies to combustion unit 14, usually make described oxygen concn be 1.0 volume % above, be preferably 1.5 volume % above, more preferably more than the 2.0 volume %, and make usually described oxygen concn be 8.0 volume % following, be preferably below the 7.0 volume %.By making the oxygen concn in the waste gas is more than the above-mentioned lower value, can make the monobromethane burning become easy.In addition, be below the above-mentioned higher limit by making the oxygen concn in the waste gas, can directly use the waste gas of oxidation step, therefore highly beneficial.Particularly, if use heat-accumulation combustion device described later, even the low waste gas of above-mentioned oxygen concn also can make it carry out good combustion as combustion unit 14.

Waste gas can directly use, and also can dilute as required, concentrate and regulate monobromethane concentration and oxygen concn.

In the present invention, be controlled at specified conditions, can suppress the generation of brominated dioxin by combustion conditions and cooling conditions with waste gas.

As the temperature of combustion of the waste gas in the combustion unit 14, to make this temperature usually be more than 450 ℃, be preferably more than 550 ℃, more preferably more than 600 ℃, and to make this temperature usually be below 1000 ℃, be preferably below 900 ℃, more preferably below 850 ℃.By the temperature of combustion that makes waste gas is more than the above-mentioned lower value, the abundant burning of monobromethane is become carry out easily, also can suppress the generation of brominated dioxin.By the temperature of combustion that makes waste gas is below the above-mentioned higher limit, can reduce cost of energy.

In addition, below the gas cooling to 250 after the burning ℃, preferably be cooled to below 200 ℃, more preferably be cooled to below 170 ℃, further preferably be cooled to below 150 ℃.Thereby the temperature of combustion unit exit gas 7 is below 250 ℃, be preferably below 200 ℃, more preferably below 170 ℃, more preferably below 150 ℃.Temperature by the back gas that will burn is controlled at above-mentioned scope, the generation of brominated dioxin in the gas after can suppressing to burn.In addition, lower limit for the cooling temperature (temperature of combustion unit exit gas 7 too) of gas after the burning there is no particular restriction, but be preferably more than 70 ℃, more preferably more than 80 ℃, when the lower limit of cooling temperature is controlled at above-mentioned scope, can save cooling time and energy.

In the present invention, in the gas cooling process after burning, make from 450 ℃ of cooling times that are cooled to 250 ℃ be below 1 second, further preferably make from 450 ℃ of cooling times that are cooled to 200 ℃ be (in the present invention, to abbreviate the needed time of the gas behind the cooling combustion as " cooling time " sometimes) below 1 second.In addition, preferably make from temperature of combustion and be cooled to cooling time of 250 ℃ be below 1 second, make more preferably that to be cooled to cooling time of 200 ℃ from temperature of combustion be below 1 second.In the process of cooling of the gas after burning,, can suppress the generation of brominated dioxin effectively by doing one's utmost to shorten residence time in the temperature range of 300 ℃ of front and back.

Gas after the burning is carried out rapid cooling method there is no particular restriction, for example, can enumerate following method: make method that the gas after the burning contacts with refrigeration agent, make method that the gas after the burning contacts with heat-sink material or heat storage, make itself and low temperature non-active gas blended method, import to method in the water with the gas to the method for the water spray of the gas after the burning, after will burning such as washer (scrubber), or the like.

According to the present invention, the brominated dioxin concentration in the gas of cooling back can be controlled at 1ng-TEQ/m ³Below, further be controlled at 0.1ng-TEQ/m ³Below, particularly be controlled at 0.01ng-TEQ/m ³Below, especially be controlled at 0.007ng-TEQ/m ³Below so extremely low-level.Wherein, with regard to brominated dioxin, except isomer, also comprise isomer with diphenylene-oxide ring with dioxin ring.Specifically can enumerate: many bromos dibenzo Dui dioxin (PBDDs), PBDF class (PBDFs) etc.According to the present invention,, also it can be controlled at the concentration range of aforesaid brominated dioxin for be considered to be difficult to abundant burning, be easy to generate the waste gas of the low monobromethane concentration of brominated dioxin in the past.

In the present invention, the assay method of brominated dioxin is as follows: " many bromos dibenzo is to the tentative investigation method of dioxin and PBDF " that (putting down into 14 years) the Japanese Environment Ministry that utilizes 2002 formulates carried out quantitatively each isomer of brominated dioxin, obtain the value of toxic equivalent (Toxic Equivalent is hereinafter referred to as " TEQ ") then based on the thought described in the bibliography 3 of the same year " brominated dioxin is discharged investigation result reports such as live telecast ".That is, described TEQ is meant: with 2,3,7, the toxicity of 8-TCDD (the tetrachloro dibenzo is to dioxin) is 1 o'clock, and the toxicity intensity of other dioxin is used the toxic equivalent factor (Toxic Equivalent Factor respectively, hereinafter referred to as " TEF ") convert, and their summation of obtaining.In addition, also can be with reference to " environment health care standard bromo more than 205 dibenzo is to dioxin and diphenylene-oxide " Corporation environmental information scientific center distribution (in October, 2000).

Kind for the combustion unit that uses in the present invention is also unrestricted, can adopt as lower device: do not use device arbitrarily such as the direct combustion unit of combustioncatalysts, the catalytic combustion system of use combustioncatalysts, the heat-accumulation combustion device of use heat storage, preferably be suitable for the heat-accumulation combustion device or the direct combustion unit of high-temp combustion.

As the combustion unit that uses in the present invention, the device that has burning portion and cooling end structure in the preferred burn device.When having such structure, can therefore can suppress the generation of brominated dioxin directly with the gas cooling after the burning.Consider also preferred heat-accumulation combustion device or direct combustion unit on the one hand from this.

In addition, as the combustion unit that uses in the present invention, the device that has the structure of heat storage in the preferred burn device.When having such structure, its efficiency of combustion is good, the stability of temperature of combustion is also higher, and is easy to cool off fast, thereby can suppress the generation of brominated dioxin.

Need to prove, there is no particular restriction, specifically can enumerate: catalyzer such as manganese oxide, cupric oxide, chromic oxide, palladium class, platinum class, other halogen resistant catalyzer etc. for above-mentioned combustioncatalysts.

Directly combustion unit possesses the preheating part of waste gas, the cooling end that makes waste gas carry out recovery of heat at incendiary roasting kiln (burning portion) in the presence of the no combustioncatalysts and the gas after burning usually.The waste gas that utilizes the heat exchanger of preheating part to carry out after the preheating mixes with fuel and airborne a kind in burning portion at least, and it is above and keep the constant time and make its oxygenolysis to be heated to kindling temperature, and discharges in cooling end cooling back.Preferably will be used for the preheating of waste gas in the heat that cooling end reclaims.

The heat-accumulation combustion device comprises: preheating chamber (preheating part) wherein possesses the heat storage that does not have thermosteresis substantially that is filled with pottery system weighting material; Combustion chamber (burning portion) is used for the waste gas after the heat storage preheating is carried out burn processing; And heat recovery chamber's (cooling end), be used for from the burning after gas carry out recovery of heat.Even this heat-accumulation combustion device has the structure that also can keep chamber temperature under the state of burner closing.And, also have by the variable structure of preheating chamber and heat recovery chamber of alternately reversibly switching of the stream that makes waste gas.For example, can adopt device of putting down in writing in the TOHKEMY 2002-303415 communique etc.

In addition, can suitably select to use from following commercially available heat-accumulation combustion device and can carry out burning of the present invention and refrigerative machine, described commercially available heat-accumulation combustion device comprises: heat-accumulation combustion deodorization equipment (German Durr company make), rotary accumulation of heat emission-control equipment (Cugai Ro Co., Ltd.'s manufacturing), double-tower type accumulation of heat emission-control equipment (Cugai Ro Co., Ltd.'s manufacturing), single tower multichamber type accumulation of heat emission-control equipment (Cugai Ro Co., Ltd.'s manufacturing) etc.

In the heat-accumulation combustion device, usually, waste gas at first is warming up to assigned temperature through heat storage in preheating chamber, burn in the combustion chamber then.Temperature of combustion can be by fuel amount and waste gas in the amount of combustiblematerials control.Burning back gas is transferred to heat recovery chamber, at short notice with the heat absorption of gas to heat storage, be discharged to outside the combustion unit after cooling off.

In the heat-accumulation combustion device, optimizations such as loading level that can be by making exhaust gas flow, heat storage, shape come the speed of cooling of the back gas that burns is regulated.Thus, can will in heat recovery chamber, be controlled to be below 1 second from 450 ℃ of cooling times that are cooled to below 250 ℃, further, can be controlled to be the cooling time that is cooled to below 200 ℃ from 450 ℃ below 1 second gas.In addition, can also be controlled to be below 1 second the cooling time that is cooled to from temperature of combustion below 250 ℃, further, can be controlled to be below 1 second the cooling time that is cooled to from temperature of combustion below 200 ℃.Preferably will be used for the preheating of waste gas in the heat that cooling end reclaims.As mentioned above, can utilize open and close valve to realize that the supply of the waste gas between each chamber and the deflated of burning back waste gas alternately switch.As the heat-accumulation combustion device, present main flow is the turning valve formula, but as long as purport according to the invention does not then have particular restriction.

There is following advantage in the heat-accumulation combustion device: even oxygen concn is below the 8.0 volume % even the waste gas of the low oxygen concentration below the 4.0 volume %, or monobromethane concentration is that 25 volume ppm are following even 15 volume ppm following, the waste gas of the following low monobromethane concentration of 10 volume ppm particularly, also can carry out burn processing not needing to supply with from the outside under the situation of oxygen.And, its heat recovery rate height, fuel cost also can significantly be reduced, and energy-conservation.

When in the heat-accumulation combustion device, burning,, can use above-mentioned combustioncatalysts etc., but consider, preferably in the presence of no combustioncatalysts, carry out the burning of waste gas from combustion temperatures, waste and the aspect that reduces cost in order to promote burning.

Compare with direct combustion unit, the stability of the temperature of combustion of heat-accumulation combustion device is high, temperature of combustion itself can also be controlled at lower level, and also cools off fast easily, therefore exists and can suppress the advantage that NOX (oxynitride) generates.In addition, because the processing efficiency of heat-accumulation combustion device is also higher, therefore can reduces the device number, and then can reduce equipment cost.

Because remaining usually in the combustion unit exit gas 7 have compositions such as bromine, hydrogen bromide, so preferably make this combustion unit exit gas 7 carry out gas-to-liquid contact with alkali and reductive agent in absorption unit 15 and be discharged in the atmosphere after absorbing again.As alkali, preferably use caustic soda, Ke Xingjia etc., as reductive agent, preferably use S-WAT, urea etc., but be not limited to these materials.Except packed tower, spray tower, wet-wall tower, can also use washer etc. as the absorption tower.Absorption unit exit gas 8 discharges after confirming to be in the state that can discharge into the atmosphere again.

Need to prove, with the p-Xylol be raw material when obtaining terephthalic acid, the difference of quality etc. as requested, the manufacture method of the terephthalic acid of industrial implementation comprises PTA method, these 2 kinds of methods of QTA method, the present invention can effectively be applicable to arbitrary method wherein.Below describe at the example that is suitable for of the present invention in above-mentioned two technologies.

At first, in conjunction with Fig. 2 the PTA method is described.Do not having under the situation of particular determination, processing condition as mentioned above.

At first, in oxidation step (I), in oxidation reactor 21, in solvent, and in the presence of catalyzer, utilize the gas B contain molecular oxygen that p-Xylol A is carried out oxidation, obtain the slurry C of terephthalic acid and solvent.Temperature of reaction is the same, but for the PTA method, most preferred temperature of reaction is 170～200 ℃.

Go out phlegma N from the oxidation reactor waste gas M of oxidation reactor 21 through condenser 26 condensation separation, be discharged from as oxidation reactor waste gas P then, and be provided in the off gas treatment step (IV) based on solvent.Condenser 26 can constitute, also can be made of multistage by one section, can also use distillation tower to replace condenser 26 to carry out same separation.Part by the phlegma N that will be obtained by waste gas M condensation is expelled to outside the system, can regulate the amount of moisture in the reaction soln.Oxygen concn among the waste gas P is generally 1.0～8.0 volume %, but trends towards low slightly in the PTA method.For example be below the 4.0 volume %.

After in reactor 21, carrying out oxidizing reaction, can also carry out low temperature as required and append oxide treatment.Appending the waste gas of discharging after the oxide treatment through low temperature also can be provided in the off gas treatment step (IV).In the PTA method, append oxide treatment and oxygen concn in the waste gas that is discharged from is also identical with main oxidizing reaction through low temperature, the tendency that reduces is a little arranged.

The slurry C that obtains is through after the intermediate process steps of carrying out, being separated into terephthalic acid cake D and mother liquor E by equipment for separating liquid from solid 22 as required in solid-liquid separation step (II).As required, can also utilize scavenging solution K, clean with 23 couples of terephthalic acid cake D of washing unit, thus terephthalic acid cake F after obtaining to clean and cleaning waste liquid L.Wherein, shown in the dotted line part of Fig. 2, also can use solid-liquid separation/washing unit 24, this device can carry out equipment for separating liquid from solid 22 and washing unit 23 in 1 device.

The filter cake F that obtains becomes terephthalic acid coarse crystallization G by drying installation 25 dryings.Then, terephthalic acid coarse crystallization G becomes high purity terephthalic acid's crystallization through not shown hydrogenation purifying process (comprise dissolving step, step of hydrogenation, crystal separate out step, solid-liquid separation step, cleaning step, drying step etc.).

On the other hand, the part of the mother liquor E that obtains in solid-liquid separation step (II) is preferably passed through mother liquor recirculation step (III) and is supplied in the oxidation step (I).That is, mother liquor E is divided into recirculation mother liquor H and discharges mother liquor J after accumulating as required in mother liquor tank etc., and recirculation mother liquor H is back to the oxidation reactor 21 of oxidation step (I).In addition, clean the oxidation reactor 21 that waste liquid L also can be back to oxidation step (I) as required.

The waste gas that obtains in above step is provided to off gas treatment step (IV) and handles.

The liquid 4 that can also reclaim aliphatic carboxylic acid in containing of utilizing as required that dehydration tower etc. obtains in to off gas treatment step (IV), contain after the liquid 5 that reclaims the aliphatic carboxylic acid esters, handles, they are back to oxidation reactor 21 as recirculation aliphatic carboxylic acid and ester class Q.

Then, in conjunction with Fig. 3 the QTA method is described.Do not having under the situation of particular determination, processing condition as mentioned above.

In oxidation step (I), in oxidation reactor 31, in solvent, and in the presence of catalyzer, utilize the gas b contain molecular oxygen that p-Xylol a is carried out oxidation, obtain the slurry c of terephthalic acid and solvent.Temperature of reaction and pressure are the same, but for the QTA method, most preferred condition is 180～230 ℃, 1～3MPa.In oxidation step, more preferably with the above oxidation of 98 weight % of p-Xylol.

Go out phlegma o from the oxidation reactor waste gas n of oxidation reactor 31 through condenser 41 condensation separation, be discharged from as oxidation reactor waste gas p then, and be provided to off gas treatment step (IV) based on solvent.Condenser 41 can constitute, also can be made of multistage by one section, can also use distillation tower to replace condenser 41 to carry out same separation.Part by the phlegma o that will be obtained by waste gas n condensation is got rid of to system, can regulate the amount of moisture in the reaction soln.Oxygen concn among the waste gas p is generally 1.0～8.0 volume %, but trends towards high slightly in the QTA method.For example be more than the 4.0 volume %.

In the oxidation step (I) of QTA method, in reactor 31, carry out carrying out high temperature after the oxidizing reaction and append oxide treatment.At this moment, preferably append and carry out low temperature between the oxide treatment and append oxide treatment at oxidizing reaction and high temperature.This be because, when before high temperature appends oxide treatment, carrying out preparatory low temperature when appending oxide treatment, can obtain the higher terephthalic acid of purity.

The slurry c that obtains in the oxidation reactor 31 is supplied to low temperature appends oxidation reactor 32, and further supply with the gas b that contains molecular oxygen, append oxidation to carry out low temperature.Low temperature appends oxide treatment preferably to carry out continuously, and its reaction times is compared short slightly with main oxidizing reaction, be preferably 5～90 minutes.

The waste gas of discharging after appending oxide treatment through low temperature also can be supplied to off gas treatment step (IV).That is, the oxidation reactor waste gas q that comes from oxidation reactor 32 goes out phlegma r based on solvent through condenser 42 condensation separation, is discharged from as oxidation reactor waste gas s then, and is provided to off gas treatment step (IV).Condenser 42 can constitute, also can be made of multistage by one section, can also use distillation tower to replace condenser 42 to carry out same separation.In the QTA method, the oxygen concn in the waste gas of discharging after low temperature appends oxide treatment is also the same with main oxidizing reaction trend towards high slightly.

The low temperature that obtains appends oxidation slurry d and is heated to assigned temperature by well heater 34 usually after utilizing pump 33 pressurization, transfers to high temperature and appends in the oxidation reactor 35, contains in supply under the situation of gas b of molecular oxygen to append oxidation.High temperature appends oxide treatment preferably to carry out continuously, and its reaction times is preferably 5～120 minutes.

The waste gas of discharging after high temperature appends oxide treatment also can be supplied to off gas treatment step (IV).That is, the oxidation reactor waste gas t that comes from oxidation reactor 35 goes out phlegma u based on solvent through condenser 43 condensation separation, is discharged from as oxidation reactor waste gas v then, and is provided to off gas treatment step (IV).Condenser 43 can constitute, also can be made of multistage by one section, can also use distillation tower to replace condenser 43 to carry out same separation.Oxygen concn in the waste gas of discharging after high temperature appends oxide treatment is low, but can and handle in off gas treatment step (IV) by waste gas p, the s merging that oxygen concn is high.

The high temperature that obtains appends oxidation slurry e and is being sent to solid-liquid separation step (II) through after the intermediate process steps as required, usually, this high temperature appends oxidation slurry e and presses after decompression is cooled to specified pressure, temperature in the evaporation unit 36 putting, and is separated into terephthalic acid cake f and mother liquor g through equipment for separating liquid from solid 37.Also can under the refrigerative situation that do not reduce pressure, carry out solid-liquid separation, but, preferably press cooling that its temperature is reduced to a certain degree through putting in order to suppress the decomposition amount of solvent to slurry e.In addition,, wish that the temperature of recirculation mother liquor can not exceed pressure, the temperature of oxidation reactor 31 significantly, for this reason, also preferably put and press cooling for the situation of carrying out mother liquor recirculation step described later (III).Put the preferred pressure after the pressure and the preferred pressure of above-mentioned solid-liquid separation step (II) and be in equal extent.In addition, come to put and press putting of evaporation unit 36 to press evaporation unit waste gas w to go out phlegma x, be discharged from as putting pressure evaporation unit waste gas y then based on solvent through condenser 44 condensation separation.As required, also can put pressure evaporation unit waste gas y to this in off gas treatment step (IV) handles.

As required, can also utilize scavenging solution 1, clean with 38 couples of terephthalic acid cake f that obtain of washing unit, thus terephthalic acid cake h after obtaining to clean and cleaning waste liquid m.Wherein, shown in the dotted line part of Fig. 3, also can use solid-liquid separation/washing unit 39, this device can carry out equipment for separating liquid from solid 37 and washing unit 38 in 1 device.

As required, the filter cake h that can also further utilize 40 pairs of drying installations to obtain carries out drying, to obtain terephthaldehyde's acid crystal i.

On the other hand, the part of the mother liquor g that obtains in solid-liquid separation step (II) is preferably passed through mother liquor recirculation step (III) and is supplied to oxidation step (I).That is, mother liquor g is divided into recirculation mother liquor j and discharges mother liquor k after accumulating as required in mother liquor tank etc., and recirculation mother liquor j is back to the oxidation reactor 31 of oxidation step (I).In addition, clean the oxidation reactor 31 that waste liquid m also can be back to oxidation step (I) as required.

The waste gas that obtains in above step is provided to off gas treatment step (IV) and handles.

The liquid 4 that can also reclaim aliphatic carboxylic acid in containing of utilizing as required that dehydration tower etc. obtains in to off gas treatment step (IV), contain after the liquid 5 that reclaims the aliphatic carboxylic acid esters, handles, they are back to oxidation reactor 31 as recirculation aliphatic carboxylic acid and ester class z.

Embodiment

Below, in conjunction with the embodiments the present invention is carried out specific description more, but the present invention is not subjected to any qualification of following embodiment.

＜measuring method 〉

(1) monobromethane concentration

Under the following conditions, utilize gas chromatographic analysis to measure monobromethane concentration.Utilize gas chromatograph GC-14B and chromatopack C-R3A (making) to measure, wherein, used the glass column of diameter 3mm, long 5m, and adopted polysiloxane DC-550 (letter and chemical industry manufacturing) as weighting agent by Shimadzu Seisakusho Ltd..Use nitrogen as carrier gas, and be 30ml/ minute its flow set.Column temperature in the analysis is that 45 ℃, detector temperature are 100 ℃.

(2) brominated dioxin concentration

" many bromos dibenzo is to the tentative investigation method of dioxin and PBDF " that (putting down into 14 years) the Japanese Environment Ministry that utilizes 2002 formulates carried out quantitatively each isomer of brominated dioxin, then, calculate the value of toxic equivalent (TEQ) based on the thought described in the bibliography 3 of " brominated dioxin is discharged investigation result reports such as live telecast " in the same year.

As brominated dioxin, except isomer, also comprise isomer with diphenylene-oxide ring with dioxin ring.

＜embodiment and comparative example 〉

In following embodiment and comparative example,, all adopted the tank reactor of mixing fully of band stirrer as comprising that low temperature, high temperature append the reactor of the oxidizing reaction of oxidation.In addition, force value is an absolute pressure.

(embodiment 1)

In reactor, supply with the recirculation mother liquor that solution (being dissolved with the solution of cobaltous acetate, manganous acetate and hydrogen bromide in the acetate that contains 14 weight % water), 6.24 weight parts that 1 weight part p-Xylol, 3.35 weight parts contain catalyzer have kept the state of the pressure and temperature when the aftermentioned equipment for separating liquid from solid separates in fact, supply simultaneously is equivalent to the air that contains molecular oxygen that p-Xylol is 20 times of moles, and carries out oxidizing reaction when the reaction times (average retention time) is adjusted to 60 minutes under 195 ℃ of temperature, pressure 1.34MPa (absolute pressure).The concentration of the cobalt/manganese in the reaction solution/bromine is respectively 300/300/1000 ppm by weight.Oxygen concn in the waste gas is adjusted in 5.0～7.0 volume % scopes.

Utilize the multistage condenser, the waste gas that will come from reactor finally is cooled to 45 ℃ of temperature, pressure 1.16MPa, and the phlegma that obtains from each condenser is after merging, and part is discharged, and rest part is back to reactor.Output to phlegma is regulated, and making the moisture concentration in the slurry mother liquor is 10 weight %.

Discharging with crude terephthalic acid and solvent from the reactor of oxidizing reaction is the slurry of principal constituent.In 5.84 weight part slurries, crude terephthalic acid is that 2.05 weight parts, mother liquor are 3.79 weight parts, and slurry concentration is 35 weight %.

This slurry of 5.84 weight parts is continuously supplied to low temperature appends oxidation reactor, and when will being adjusted into 30 minutes the reaction times, under 183 ℃ of temperature, 1.04MPa, carry out low temperature and append oxidizing reaction.The air capacity of supplying with is adjusted to above-mentioned oxidizing reaction feed rate 1/44.6.Oxygen concn in the waste gas that has air is simultaneously regulated, made oxygen concn in 5.0～7.0 volume % scopes.

Utilize the multistage condenser, will come from the waste gas that low temperature appends oxidation reactor and finally be cooled to 45 ℃ of temperature, pressure 1.16MPa, the phlegma that obtains from each condenser is back to low temperature and appends oxidation reactor after merging.

Then, append the slurry of discharging the oxidation reactor from low temperature and append oxidation reactor, and when will being adjusted into 50 minutes the reaction times, under 260 ℃ of temperature, pressure 5.5MPa, carry out high temperature and append oxidizing reaction through being continuously supplied to high temperature after heating, the pressurization.Being adjusted to the air capacity of supplying with respect to the terephthalic acid molecular oxygen is 0.12 times of mole.And the oxygen concn in the waste gas is adjusted to 0～0.5 volume %.

Utilize the multistage condenser, will come from the waste gas that high temperature appends oxidation reactor and finally be cooled to 45 ℃ of temperature, pressure 1.16MPa, the phlegma that obtains from each condenser is back to high temperature and appends in the oxidation reactor after merging.

Appending the slurry of oxidation reactor discharge is pressing evaporation unit putting temperature, pressure range that pressure is cooled to initial reactor from high temperature via putting, be supplied in the screen bowl centrifuge then, under the situation that keeps this temperature, pressure, carry out solid-liquid separation, be separated into terephthalic acid cake and mother liquor.After acetate cleans, discharge in filtration (screen) portion of filter cake in settling centrifuge, and disposable putting be depressed into normal atmosphere so that the liquid evaporation that adheres to carries out further drying again, thereby obtain 1.56 weight part terephthaldehyde acid crystals from outlet valve.

On the other hand, make mother liquor under the situation that keeps its temperature, pressure, be divided into 35 weight % discharge mother liquor and 65 weight % recirculation mother liquors, the recirculation mother liquor is transferred in the initial reactor through obtaining after the solid-liquid separation.Reclaim useful component such as terephthalic acid, acetate, catalyzer and utilize from discharge mother liquor, rest part is discharged into the outside after innoxious.

Come from reactor, low temperature and append the waste gas that oxidation reactor and high temperature appends oxidation reactor and behind above-mentioned condenser, combine, and in off gas treatment step shown in Figure 1, handle with the form of the waste gas of 45 ℃ of temperature, pressure 1.16MPa.

That is, from the tower bottom when pressurizing absorption tower 11 is supplied with waste gas 1, spray water as solvent 2 from tower top.The water that sprays can absorb the acetate in the waste gas etc.In addition, in the tower bottom, absorbed that dissolving has absorbed the methyl acetate in the waste gas etc. in the water of acetate etc.The methyl acetate that absorbs as contain reclaims the aliphatic carboxylic acid esters, liquid 5 from the tower bottom discharge, and be back in the reactor and utilize again.In addition, acetate etc. are discharged from midsection with the form that contains the liquid 4 that reclaims aliphatic carboxylic acid, after the dehydration tower dehydration, still are back in the reactor and utilize.

On the other hand, the nubbin of waste gas, to be gas 3 discharge and be heated to 155 ℃ heat exchanger 12 from top of tower.Then, gas 3 is sent to gas expander 13 and is used as the part motivating force of air compressor, becomes the exit gas 6 of pressure 0.1MPa.Oxygen concn in the exit gas 6 is that 6.4 volume %, monobromethane concentration are 13.7 volume ppm.

Exit gas 6 is imported in the heat-accumulation combustion device as combustion unit 14, and in 820 ℃ of temperature of combustion (temperature of combustion chamber), cooling time in cooling room be below 1 second, carry out burn processing (wherein under the condition of 80～90 ℃ of temperature outs (temperature of exit gas), be meant that burning back gas reaches the cooling time below 200 ℃ described cooling time, down together).That is, to be cooled to the time below 200 ℃ be below 1 second to 820 ℃ of gases after heat-accumulation combustion device internal combustion.It is pointed out that after reaching temperature of combustion, do not carry out the supply of air and fuel.

The result that monobromethane concentration in the combustion unit exit gas is measured shows that monobromethane concentration promptly is lower than 0.1 volume ppm below limit of detection.In addition, the result that the brominated dioxin concentration in the combustion unit exit gas is measured shows that brominated dioxin concentration promptly is lower than 0.007ng-TEQ/m below limit of detection ³Can think that thus monobromethane has carried out abundant burning, and change into bromine substantially.The result is shown in table-1.

Then, combustion unit exit gas and alkali are contacted to absorb after the compositions such as wherein bromine, hydrogen bromide with reductive agent generation solution-air, after confirming to reach harmless state it is discharged in the atmosphere.

(embodiment 2)

Obtained the exit gas 6 of discharging by gas expander 13 according to the method identical with embodiment 1.Oxygen concn in the exit gas 6 is that 6.6 volume %, monobromethane concentration are 13.9 volume ppm (value of oxygen concn and monobromethane concentration and embodiment 1 exist to a certain degree, and difference is to be caused by the change in the operation).In the same manner this exit gas 6 is imported in the heat-accumulation combustion device with embodiment 1, and in 600 ℃ of temperature of combustion, cooling time be below 1 second, carry out burn processing under the condition of 80～90 ℃ of temperature outs.That is, to be cooled to the time below 200 ℃ be below 1 second to 600 ℃ of gases after heat-accumulation combustion device internal combustion.It is pointed out that after reaching temperature of combustion, do not carry out the supply of air and fuel.

Its result, the monobromethane concentration in the combustion unit exit gas are 1.1 volume ppm.In addition, the brominated dioxin concentration in the combustion unit exit gas promptly is lower than 0.007ng-TEQ/m below limit of detection ³Can think that thus monobromethane has carried out abundant burning, and change into bromine substantially.The result is shown in table-1.

(embodiment 3)

Obtained the exit gas 6 of discharging by gas expander 13 according to the method identical with embodiment 1, utilize nitrogen that this exit gas 6 is diluted, it is that 2.0 volume %, monobromethane concentration are 4.1 volume ppm (ratio of oxygen concn and monobromethane concentration and embodiment 1 exist to a certain degree, and difference is to be caused by the change in the operation) that the result makes oxygen concn.In the same manner this exit gas 6 is imported in the heat-accumulation combustion device with embodiment 1, and in 820 ℃ of temperature of combustion, cooling time be below 1 second, carry out burn processing under the condition of 80～90 ℃ of temperature outs.That is, to be cooled to the time below 200 ℃ be below 1 second to 820 ℃ of gases after heat-accumulation combustion device internal combustion.It is pointed out that after reaching temperature of combustion, do not carry out the supply of air and fuel.

Its result, the monobromethane concentration in the combustion unit exit gas promptly are lower than 0.1 volume ppm below limit of detection.In addition, the brominated dioxin concentration in the combustion unit exit gas promptly is lower than 0.007ng-TEQ/m below limit of detection ³Can think that thus monobromethane has carried out abundant burning, and change into bromine substantially.The result is shown in table-1.

(embodiment 4)

Obtained the exit gas 6 of discharging by gas expander 13 according to the method identical with embodiment 1.Oxygen concn in the exit gas 6 is that 6.4 volume %, monobromethane concentration are 13.7 volume ppm.This exit gas 6 is imported in the direct combustion unit as combustion unit 14, and in 1000 ℃ of temperature of combustion, cooling time be below 1 second, carry out burn processing under the condition of 180 ℃ of temperature outs.That is, time of being cooled to below 200 ℃ of 1000 ℃ of gases after direct combustion unit internal combustion is below 1 second.It is pointed out that in order temperature of combustion to be remained on 1000 ℃, sustainable supply air and fuel (heavy oil).

Its result, the monobromethane concentration in the combustion unit exit gas promptly are lower than 0.1 volume ppm below limit of detection.In addition, the brominated dioxin concentration in the combustion unit exit gas promptly is lower than 0.007ng-TEQ/m below limit of detection ³Can think that thus monobromethane has carried out abundant burning, and change into bromine substantially.The result is shown in table-1.

(comparative example 1)

Obtained the exit gas 6 of discharging by gas expander 13 according to the method identical with embodiment 1.Oxygen concn in the exit gas 6 is that 5.0～7.0 volume %, monobromethane concentration are 13.2 volume ppm.This exit gas 6 is imported in the catalytic combustion system as combustion unit 14, and utilize palladium class oxide catalyst under the condition of 352 ℃ of temperature of combustion, 352 ℃ of temperature outs, to carry out burn processing.

Its result, when the monobromethane concentration of combustion unit exit gas was measured, monobromethane concentration was 0.8 volume ppm.In addition, the result that the brominated dioxin concentration in the combustion unit exit gas is measured shows that brominated dioxin concentration is 120ng-TEQ/m ³The result is shown in table-1.

Catalytic combustion system exit gas with alkali with reductive agent generation solution-air contacted to absorb thereafter.

(comparative example 2)

Obtained the exit gas 6 of discharging by gas expander 13 according to the method identical with embodiment 1.Oxygen concn in the exit gas 6 is that 5.0～7.0 volume %, monobromethane concentration are 13.0 volume ppm.Except this exit gas 6 being imported in the catalytic combustion system as combustion unit 14, and temperature of combustion is set at 401 ℃, temperature out is set at beyond 401 ℃, carried out burn processing according to the method identical with comparative example 1.

Its result, the monobromethane concentration in the combustion unit exit gas promptly are lower than 0.1 volume ppm below limit of detection.In addition, the brominated dioxin concentration in the combustion unit exit gas is 31ng-TEQ/m ³The result is shown in table-1.

[table 1]

Industrial applicibility

According to the present invention, can suppress in the situation that brominated dioxin generates waste gas processings of burning, so can be used as a kind of can alleviating the manufacture method of the aromatic carboxylic acid of the burden of environment is had industrial applicibility.

In addition, according to the present invention, can be to the processing of effectively burning of the Celfume in the waste gas, therefore can be used as a kind of manufacture method of the aromatic carboxylic acid that can reduce operating cost and equipment cost, energy savings and have industrial applicibility.

In addition, because the present invention not only can suppress the generation of brominated dioxin when waste gas being burnt processing, can also suppress the generation of the aromatic compound such as benzene class and NOX (nitrogen oxide), therefore can be used as a kind of can alleviating the manufacture method of the aromatic carboxylic acid of the burden of environment is had industrial applicibility.

Need to prove, the full content specific reference of on October 26th, 2007 was filed an application in this application, Japanese patent application 2007-278939 number and Japanese patent application 2007-278940 number specification sheets, claims, accompanying drawing and the summary of filing an application on October 26th, 2007 is in specification sheets of the present invention.

Claims (11)

1. the manufacture method of an aromatic carboxylic acid, this method comprises:

In the presence of bromine-containing compound, the alkyl aromatic compound oxidation is obtained the oxidation step of aromatic carboxylic acid; And

Make the waste gas incendiary step in combustion unit that produces in the above-mentioned oxidation step,

Wherein, make after this waste gas burns under 450～1000 ℃ temperature of combustion, with below the gas cooling to 250 after the burning ℃, and, in this process of cooling, from 450 ℃ to 250 ℃ cooling times be below 1 second.

2. the manufacture method of aromatic carboxylic acid according to claim 1, wherein, from cooling time of described temperature of combustion to 250 ℃ be below 1 second.

3. the manufacture method of aromatic carboxylic acid according to claim 1 and 2 wherein, utilizes heat storage that the gas after burning is cooled off.

4. according to the manufacture method of each described aromatic carboxylic acid in the claim 1～3, wherein, under the situation that does not have combustioncatalysts, burn.

5. according to the manufacture method of each described aromatic carboxylic acid in the claim 1～4, wherein, combustion unit is the heat-accumulation combustion device.

6. according to the manufacture method of each described aromatic carboxylic acid in the claim 1～5, wherein, the concentration of the brominated dioxin in the gas of cooling back is counted 1ng-TEQ/m by toxic equivalent ³Below.

7. according to the manufacture method of each described aromatic carboxylic acid in the claim 1～6, wherein, oxidation step carries out in the aliphatic carboxylic acid solvent, and this method comprises:

The slurry that contains aromatic carboxylic acid and solvent that obtains in oxidation step is carried out solid-liquid separation to obtain the solid-liquid separation step of aromatic carboxylic acid filter cake and mother liquor; And

At least a portion of this mother liquor is supplied to the mother liquor recirculation step of above-mentioned oxidation step.

8. the manufacture method of aromatic carboxylic acid according to claim 7 wherein, is supplied to above-mentioned oxidation step more than the 50 weight % with mother liquor.

9. according to the manufacture method of each described aromatic carboxylic acid in the claim 1～8, wherein, the concentration of monobromethane is below the 100 volume ppm in the waste gas.

10. according to the manufacture method of each described aromatic carboxylic acid in the claim 1～9, wherein, alkyl aromatic compound is a p-Xylol.

11. according to the manufacture method of each described aromatic carboxylic acid in the claim 1～10, wherein, aromatic carboxylic acid is a terephthalic acid.

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