JPS5943402B2 - Method for producing sulfuric acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to reducing S0 produced by the decomposition of sulfate and dilute sulfuric acid.
SO2 is supplied to each catalyst shelf while SO2 is supplied to each catalyst shelf.
The SO3-containing gas is cooled between catalyst shelves, and S
It relates to a method for producing sulfuric acid by absorbing O3 into sulfuric acid.

In many chemical processes, such as the leaching of ores with sulfuric acid solutions and the pickling of metals, waste acids are produced which have a relatively low concentration of sulfuric acid and which contain some salt as an impurity.

For reasons of environmental conservation, the discharge of such waste acids into rivers and territorial waters must be increasingly restricted, and there are considerable transportation costs for abandonment, and even more for abandonment at sea. It takes.

Such waste acids must therefore be treated in an appropriate manner to make them recyclable or non-hazardous products, or to reduce their weight and volume during transport. .

This treatment is even more necessary from the viewpoint of raw material recovery.

Processing of waste acid is mainly carried out by thermal decomposition at 250-1100°C.

In this case, in addition to SO2 and H2O, various decomposition products that differ depending on impurities are produced.

In general, SO2 is the most valuable decomposition product and is generally converted to SO3 by a suitable post-process using a catalyst, absorbed in sulfuric acid and recovered as sulfuric acid.

The higher the sulfuric acid concentration, the more economically decomposition of waste acid can be carried out.

Therefore, the waste acid is generally concentrated by evaporation to the highest possible concentration.

As is known, the concentration of waste acids is carried out in immersion burners, which requires expensive primary energy and high temperature levels.

Concentration of waste acids is also known by direct heat exchange with the hot cracking gases produced in the cracking process (West German Patent No. 20).
37619, 861552, West German Patent Application No. 2339859) or by indirect heat exchange with high-temperature cracked gas (West German Patent Application No. 16
21637), but these methods require a gas with a high temperature, ie a gas with valuable heat capacity, for concentration.

Furthermore, the end gas of the contact process
It is known to scrape with dilute sulfuric acid to remove SO3 and sulfuric acid mist from ) and to concentrate the dilute sulfuric acid (
West German Patent Application No. 2145546).

In this case, it is possible to increase the concentration by heating the terminal gas prior to treatment with dilute sulfuric acid.

An object of the present invention is to provide a method for treating dilute sulfuric acid containing salts, which is as thermoeconomically advantageous as possible, and which keeps operating costs and equipment costs low.

According to the invention, this purpose is to catalytically convert 802 to SO3 in each catalyst shelf while supplying SO2 produced by the decomposition of sulfate and dilute sulfuric acid to each catalyst shelf, and to cool the SO3-containing gas between the catalyst shelves. The method for producing sulfuric acid by absorbing SO3 into sulfuric acid includes the following steps: (B) combining the sulfuric acid production step with the treatment step of salt-containing dilute sulfuric acid; decomposing the sulfate; (C) high temperature absorption of SO3 from the gas in the contacting step, at least in intermediate absorption at 100-200°C;
(D) absorbing said salt-containing dilute salt by direct contact with a hot gas consisting of the end gas of a contact process device and/or a low moisture inert gas heated with heat from said contact process device; (E) At the same time, supplying the thermal energy of the heating acid from at least the absorber of the contact method apparatus by indirectly exchanging heat with the salt-containing dilute sulfuric acid; (Fl Concentrating the dilute sulfuric acid using a plurality of concentrators connected in series in the direction of flow of the hot gas, each having an independent acid circuit with a different acid concentration; and (G) from the hot catalytic gas. Utilizing at least a part of the heat generated in the acid in the absorber when absorbing SO3 to heat dilute sulfuric acid in the acid circulation path in the concentration stage. .

In the arrangement according to the invention, by absorbing SO3 from the gas in the contacting step at an operating temperature of 100-200[deg.] C., good absorption and hotter acid from the absorber can be obtained at the same time.

The higher the temperature of the acid from the absorber, the higher the temperature of the gas leaving the absorber and the temperature of the medium heated by indirect heat exchange with the hot acid from the absorber. water can be efficiently taken away.

In the arrangement according to the invention, the concentration of dilute sulfuric acid is carried out by said concentrator, so that with different acid concentrations practically vapor saturation of the gas can be obtained even when the acid concentration is at low temperature, which makes it possible to The amount of heat generated by the system at low temperature levels can be utilized economically.

The reason is that even a low temperature heat source can be used to heat this low temperature 11 gas, since water can be driven out of the low concentration acid with a relatively low temperature gas.

In the configuration of the present invention, when the amount of heat generated in the acid in the absorber is used to heat the dilute sulfuric acid, this heat transfer can be carried out either by heat exchange between acids or by an independent medium such as water or oil. This can be done by

In this way, the thermal energy generated in the absorber acid at high temperature levels is economically fully utilized for the overall process.

In a preferred configuration according to the present invention, in the step (B), at least a part of the treated dilute sulfuric acid can be further decomposed, and in step (B), the energy of the hot acid from the dryer is further used to It can be supplied by indirect heat exchange with salt-containing dilute sulfuric acid.

Further, in a preferred configuration according to the invention, the volume of gas used for water removal is 30% of that of the terminal gas from the terminal catalyst shelf.
3 larger than the capacity after final absorption.

This allows the heat exchange area of the gas to be extremely small.

The reason for this is that when the acid concentration after treatment is the same, the gas temperature needs to be lower when the capacity is larger than when it is small, and it only needs to be heated to a lower temperature in the heat exchanger. It is.

In a preferred configuration of the present invention, the concentration of acid decreases from the gas inlet to the gas outlet in each of the independent acid circuits.

This allows a high level of moisture absorption by the gas, both when the gas temperature remains constant and when it increases.

In a preferred embodiment of the invention, the concentration of the dilute sulfuric acid is also carried out in at least one concentration stage with a plurality of concentrators connected in series, and between the concentrators the gas stream is filled with air and/or Flue gases are mixed.

This makes it possible to remove moisture at low gas temperatures and also increases the amount of moisture removed.

In a preferred embodiment of the invention, it is also provided that the concentration of the dilute sulfuric acid is carried out in its flow direction first with air and/or flue gas in at least the first concentration stage and with end gas, i.e. the final concentration stage, in the final concentration stage. This is carried out with the gas leaving the final absorber after the catalyst shelf, and can also be carried out with the addition of air and/or flue gas.

Each concentration stage preferably consists of a plurality of concentrators connected in series with independent acid circuits of different acid concentrations.

This provides contact between the end gas and the highly concentrated acid and improves the separation of H2SO4 mist and SO3.

In a preferred embodiment of the invention, it is further provided that the concentration of the dilute sulfuric acid is carried out in its flow direction first with said terminal gas in at least a first concentration step, and furthermore,
It can be carried out with the addition of air and/or flue gas, and in the final concentration stage with air and/or flue gas.

The concentration stages preferably consist of several concentrators connected in series with independent acid circuits of different acid concentrations.

In the case of low concentrations, especially low acid concentrations, such a configuration is advantageous, since the exhaust gas temperature of the end gas can be kept low.

In a preferred embodiment of the invention, the dilute sulfuric acid is further concentrated in a plurality of concentration stages each having a parallel acid circuit.

This keeps the gas temperature low in all enrichment stages and also keeps the water removal from all stages the same at high gas temperatures.

In a preferred embodiment of the invention, a further separation of the salt from the acid is carried out after concentration or between concentration steps.

This separation is preferably carried out by crystallization.

By concentrating after separation of the salts, acids with very low salt contents can be obtained.

This acid is simply concentrated and mixed directly with the sulfuric acid produced in the contact method equipment without going through a decomposition process.

This allows the decomposition device and the contact device to be downsized.

In a preferred embodiment of the invention, it is further provided that at least a portion of the gas heat generated in the contact process apparatus after intermediate absorption is utilized for heating the gas used to remove water from the dilute sulfuric acid.

In this case, both the intermediate absorption and the terminal absorption are operated as high temperature absorption, and the drying of the gas is preferably carried out at an elevated temperature of about 60-75° C. before being introduced into the contact process apparatus.
・.

The excess gas heat is thereby built up and can be utilized particularly economically with low heat exchange surfaces.

A part of the gas heat present after the intermediate absorption must optionally be utilized for heating the catalytic process gas, ie if the SO2 content of the gas is low.

In a preferred embodiment of the invention, it is further provided that during the drying of the gas introduced into the catalytic system, the amount of heat generated in the dryer acid at least partially heats the dilute acid prior to its introduction into the concentration stage. used for.

The heat transfer is carried out by acid-to-acid heat exchange or by an independent medium such as water, oil, etc.

In this way, the thermal energy generated during drying at low temperature levels but in large quantities is economically well utilized for the overall process.

In a preferred embodiment of the invention, it is further provided that part of the thermal energy generated in the absorber acid when SO3 is absorbed from the hot catalytic process gas is used to preheat the dilute sulfuric acid before it is introduced into the concentration stage. be done.

The heat transfer is carried out by acid-to-acid heat exchange or by an independent medium such as water, oil, etc.

This arrangement is particularly advantageous when the thermal energy from the dryer acid is not sufficient to provide the necessary heating for the dilute sulfuric acid prior to its introduction into the concentration stage.

In a preferred embodiment of the invention, it is further provided that the thermal energy insufficient for the required concentration of the dilute sulfuric acid is supplied externally to the gas stream before it is introduced into the concentration stages and/or between the concentrators of each concentration stage.

Preferably, the external heat is provided as a hot gas, such as flue gas.

In this case, the entire gas stream of the condensation stage may consist solely of the gas that provides the external heat.

This allows the proportion of required external heat to be kept as low as possible, and the external heat can be utilized at a relatively low temperature level.

Note that external heat refers to all heat excluding that coming from the contact method system, and therefore heat coming from the decomposition process is also considered external heat.

In a preferred embodiment of the invention, furthermore, the thermal energy insufficient for the required concentration of the dilute sulfuric acid is provided by heating the dilute sulfuric acid in the acid circuit of the concentration stages.

In this case too, external heat at a low temperature level, such as waste steam from a turbine device or high-temperature water, is used.

In a preferred embodiment of the invention, the salts separated during the entire process are further dehydrated before being fed to the decomposition stage.

This allows the salt to be used more effectively in the process and reduces the amount of sulfur source (Schwefel trMger) required to be added to the cracking process.

This dehydration effect eliminates the need for dehydration at high decomposition temperatures and has the advantage of reducing the amount of moisture introduced into the process.

A preferred configuration of the invention further includes at least a portion of the concentration being carried out in a Venturi tube device.

Apparatus of this type is suitable for concentration, especially for the treatment of salt-containing acids.

In a preferred embodiment of the invention, the concentration is further carried out under reduced pressure.

This is effective in stealing water.

In a preferred embodiment of the invention, furthermore, after the concentration, the moisture content of the gas is reduced by condensation.

After the moisture has been condensed out, the gas can be led directly to the chimney, refluxed to a concentrator circuit, or sent to another condensation step.

This reduces the moisture content in the waste gas, allows it to be contained over and over again with a constant amount of gas, or allows concentration to be carried out without producing waste gas.

Condensation can take place either indirectly or directly.

In a preferred embodiment of the invention, the decomposition of the salt-containing machine and/or the salt is further carried out in the presence of oxygen or an oxygen-rich gas.

This makes it possible to generate gas with a high S02 content.

The main advantage of the method of the present invention constructed as described above is that excess heat, including heat generated at relatively low temperature levels, from the catalytic sulfuric acid production system can be used economically for concentrating salt-containing dilute sulfuric acid. ℃・It is at the point of obtaining.

As a result, the consumption of expensive primary energy or the use of heat with high temperature levels is unnecessary or saved.

The method according to the invention is particularly suitable for treatments such as the concentration of waste acids resulting from the processing of Ti-containing materials.

Next, details of the present invention will be explained for each embodiment with reference to the drawings.

Example 1 Figure 1 shows a factory that manufactures pigments from Australian titanium iron ore.
This diagram schematically shows the flow rates of materials and intermediate products at each process step on a scale that requires sulfuric acid equivalent to 1000 me100 Otons per day.

In this process, the acid generated by hydrolysis is evaporated and concentrated to approximately 44.4% by weight H2SO4, and then decomposed by heat treatment in a fluidized bed furnace, for example, and the produced S02 is converted to sulfuric acid in a contact method device connected downstream. , this sulfuric acid is then supplied again for dissolving the titanite.

Losses occurring in the entire process (calculated as SO3) are replenished by feeding sulfur-containing material to the cracking furnace.

The amount of heat required to evaporate and concentrate the dilute acid can be sufficiently met by using the residual heat from the contact process.

The heat release rates for the individual process steps of the contact process apparatus are shown schematically in FIG.

The types and states of these generated heat amounts and their utilization status for dilute acid evaporation and concentration are shown in Figure 5.

In this figure, a catalytic system consisting of a catalytic reactor and a heat exchanger is not shown.

SO2-containing gas at a temperature of about 38° C. and an SO2 concentration of about 28.43 vol. and is discharged via conduit 3.

The acid in this dryer is transferred to conduit 4, cooler 5, conduit 6, pump 7
, through conduit 8 and nozzle 9.

Approximately 190% partially converted to SO3 through conduit 1a
C. gas is introduced at a rate of 89930 standard m@3 /h into the Venturi intermediate absorber 2a, where the SO3 is mostly absorbed and discharged at about 140 DEG C. via conduit 3a.

The acid of this absorber is circulated via conduit 4a, coolers 5a, 5a1, conduit 6a, pump 7a, conduit 8a and nozzle 9a.

Via conduit 1b, the catalytically converted gas at 180° C. is introduced at a rate of 78,590 standard m”/h into Venturi end absorber 2b, where the remaining SO3 is absorbed.
It is discharged via conduit 3b at approximately 110°C.

The acid in the end absorber is circulated via conduit 4b, cooler 5b, conduit 6b, pump 7b, conduit 8b and nozzle 9b.

The acid transfer path between the Venturi dryer and both Venturi absorbers and the removal of the generated strong acid are omitted in this process diagram.

Concentration of the dilute acid to about 44.4% by weight H2SO4 is carried out in a multi-stage evaporator consisting of two concentration stages.

The total amount of heat required for preheating the dilute acid and evaporating water from the dilute acid reaches about 26.2 x 106 kcal/h.

A dilute acid with a H2SO4 concentration of about 21% by weight and a temperature of about 45°C is 10%
It is conducted at a rate of 6000 Kg/h through conduit 92 to the acid cooler 5 where it is preheated to approximately 75° C. in countercurrent with the acid from the dryer.

This acid passes through conduit 93 to acid section 46 of the first concentration stage.

During this concentration stage, air from the atmosphere is sent by a blower 34 to carry the generated water vapor to the outside.

In other words, air with a water vapor content of about 1147 kg/h is about 62
285 standard m/h through conduit 35 to a heat exchanger 36a located between the terminal catalyst shelf and the terminal absorber in a catalytic system (not shown); It is preheated to about 330° C. and introduced via conduit 37 into the vertical venturi tube 38 of the first concentration stage.

The H20 saturated waste gas at about 75° C. passes through the connecting conduit 39 at a rate of about 23085 kg/h through the horizontal venturi pipe 41, the spray tower 42 and the separator 43 containing water and passing through the connecting conduit 39 at a rate of about 23085 kg/h.
It leaves the concentrator via line 44 at a rate of 85 kg/h.

The H2SO4 concentration of the circulating acid is about 30% by weight in the vertical venturi circuit and about 25% by weight in the horizontal venturi-spray tower circuit.
7. This is the weight section.

The acid is taken out from the acid section 45 via the conduit 47 at about 75°C;
It is guided to the acid cooler 5a.

There, it is preheated to about 100° C. by heat exchange with high-temperature acid at about 140° C. from the intermediate absorber, and from there it is passed through a conduit 48 to a pump 49, and by this pump, it is passed through a conduit 51 to a nozzle 62.
and the other through conduit 50 to nozzle 63 .

Approximately 15 Or7+″ from both nozzles 62.63
The acid is sprayed into the gas stream at a rate of /h.

The acid is withdrawn from the acid section 46 via conduit 52 at a temperature of approximately 75 DEG C. and is pumped by pump 58 without preheating via conduit 60 to nozzle 64 and via conduit 59 to nozzle 65.

Acid is pumped through conduit 61 to acid section 45 at a rate of approximately 89,620 k19/h.

Both nozzles 64,65 each spray acid into the gas stream at a rate of approximately 100 m'/h.

78,670 kg of acid with a H2SO4 concentration of approximately 30% by weight
h is sent via conduit 33 to acid section 17 of the second concentration stage.

In the second concentration stage, the end gas produced in the sulfuric acid production plant is used as a steam carrier.

A heat exchanger installed between the terminal catalyst shelves in a catalytic process system (not shown) with a rate of approximately 77,485 standard m'/h of the terminal gas at approximately 110° C., containing almost no water vapor. 36 via conduit 3b, where it is preheated to approximately 182° C. and introduced via conduit 10a into the vertical venturi tube 10 of the second concentration stage.

After passing through the connecting pipe 11, the horizontal venturi pipe 12, the spray tower 14, and the separator 15, the humid temperature gas containing H2O at a rate of about 21,980 kg/h is transferred at a rate of about 104,860 standard m/h to about 7
The terminal gas is led to a chimney (not shown) at 0°C.

The concentration of the sulfuric acid solution in the vertical Venturi tube circuit is approximately 44.4% by weight, and that in the horizontal Venturi tube-spray tower circuit is approximately 32% by weight.
．． It is 7% by weight.

The acid is discharged from the acid reservoir 13 at about 70° C. via the conduit 18 and led to the acid cooler 5a1.

There, it is preheated to about 100° C. by heat exchange with high-temperature acid at about 140° C. coming from the intermediate absorber, and from there it passes through conduit 19 to pump 20, which in turn passes it through conduit 22 to nozzle 28K, and from there to conduit 21. is sent to the nozzle 29 through.

Acid is sprayed into the gas stream from both nozzles 28,29 at a rate of about 15 o=/h.

The acid is discharged from the acid reservoir 17 via conduit 24 at a temperature of about 70° C. and is led to an acid cooler 5b where about 1
It is preheated to about 90°C by heat exchange with a hot acid at 10°C.

From there, the pump 25 passes through the conduit 24a to the conduit 27.
through the nozzle 31K, and through the other conduit 26 to the nozzle 30.
sent to.

Acid is sprayed into the gas stream from both nozzles 30,31 at a rate of about 100 m3/h each.

Via conduit 32, acid is pumped to acid sump 13 at a rate of approximately 67,640 kg/h.

About 44.4% by weight concentrated sulfuric acid at about 100°C is about 6
It exits via conduit 23 at a rate of 2000 kg/h and is sent to the acid decomposition unit.

Example 2 Figure 2 is a process diagram of a factory that requires tooot/day of sulfuric acid as S03 in the process of manufacturing pigments from Canadian slag, with the flow rates of materials or intermediate products at each process step. be.

In this case, the slag is immediately hydrolyzed after dissolution, omitting intermediate crystallization.

The acid produced by hydrolysis is sent to an evaporative concentration system where it is concentrated.

All the heat generated in the contact method equipment is utilized for concentration (Figure 4).

The acid produced by the hydrolysis is concentrated and sent for decomposition, but in this case, unlike Example 1, the decomposition is carried out under the supply of atmospheric air instead of 02-rich air.

Therefore, the SO2 concentration near the inlet of the contact method device is about 17.
Therefore, the amount of heat and temperature generated per hour are different.

In the contact method apparatus, heat is generated as shown in FIG. 4, and the heat is utilized for concentration as shown in FIG. 6.

In this case, the catalytic method apparatus system consists of a catalytic reactor and a heat exchanger, which are not shown.

Via conduit 1, SO2-containing gas with an SO2 concentration of about 17.0 parts by volume is introduced into Venturi dryer 2 at about 38 DEG C. and at a rate of about 67,430 standard m''/h.

Also, air at 25°C in the atmosphere passes through conduit 1c at approximately 6357°C.
After being mixed with the SO2-containing gas for dilution at a rate of 0 standard m'/h and dried together in a dryer, it is discharged via line 3 at about 65.degree.

The dryer acid passes via line 4, coolers 5 and 5.1, line 6 to pump 7, which in turn circulates it via line 8 and nozzle 9.

At about 185°C, the gas partially converted to SO3 is about 1
A Venturi intermediate absorber 2aK is introduced via line 1a at a rate of 26,240 standard m3/h, where the SO3 is largely absorbed and removed and discharged at approximately 140° C. through line 3a.

The acid from this absorber is transferred to conduit 4a, cooler 5a and 5ax
, through conduit 6a, pump 7a, conduit 8a and nozzle 9a.

The gas that has undergone catalytic conversion has a temperature of about 11582 at about 180°C.
It is introduced at a rate of 0 standard m'/h via line 1b into a venturi-type end absorber 2b, where the remaining S03 is absorbed and discharged at about 110° C. via line 3b.

The acid from this absorber is transferred to conduit 4b, cooler 5b, conduit 6b
, pump 7b, conduit 8b and nozzle 9b.

The acid transfer path between the Venturi dryer and the two Venturi absorbers, as well as the removal of the strong acid as product, are not shown in this flow diagram.

The dilute acid is concentrated to a H2SO4 concentration of about 38.9% by weight in a multi-stage evaporation system consisting of two concentration stages.

The total amount of heat required to preheat the dilute acid and to evaporate water from the dilute acid is approximately 30.4 x 106 kcalA.

Dilute acid with a H2S04 concentration of about 22.1% by weight and at about 45° C. is conducted at a rate of 129,580 Kg/h through conduit 92 to acid cooler 5, where it exchanges heat countercurrently with the acid from the dryer. Preheat to approximately 85°C.

This acid enters the acid reservoir 46 of the first concentration stage via conduit 93.

During this concentration stage, atmospheric air is sent by blower 34 to entrain the water vapor to the outside.

That is, the air containing about 2568 kg/h of water vapor is about 103
000 standard m'/h through conduit 35 to a heat exchanger 36a located between the terminal catalyst shelf and the terminal absorber in the catalytic process apparatus group (not shown), where approximately 260 m'/h
After being preheated to 0.degree. C., it is introduced via conduit 37 into the vertical venturi tube 38 of the first concentration stage.

The waste gas saturated with about 2857 oky/h of H2O passes through the connecting pipe 39, the horizontal Nturi pipe 41, the spray tower 42, the separator 43 and the conduit 44 at about 70°C to produce about 28 ky/h of H2O.
It leaves the device entrained at a rate of 570 kg/h.

The H2SO4 concentration of the circulating acid will be about 28.4 weight width for the vertical venturi circuit and about 23.6 weight width for the horizontal venturi-spray tower circuit.

The acid is discharged from the acid reservoir 45 at about 70° C. and is led via conduit 41 to the acid cooler 5b where about 1
It is preheated to about 88° C. by heat exchange with hot acid at 10° C. and from there is passed through conduit 48 to pump 49 which in turn sends it through conduit 51 to nozzle 62 and then through conduit 50 to nozzle 63.

From nozzle 62, at a rate of about 150 m'/h, nozzle 63
Acid is sprayed into the gas stream at a rate of approximately 100 m'/h.

Acid is discharged from the acid reservoir 46 via conduit 52 at approximately 70°C and sent to an acid cooler 5.1 where it is preheated to approximately 77°C by heat exchange with the acid from the dryer and passed through conduit 53. to pump 58, which pump passes through conduit 60 to nozzle 64;
to the nozzle 65 via the other conduit 59.

Furthermore, 121,947 kg/
Acid is supplied at a rate of h.

Approximately 1007y+3/ from both nozzles 64.65
The acid is sprayed into the gas stream at a rate of h.

Also, 103,583 kg of sulfuric acid with a concentration of approximately 28.4 weight range
/h via conduit 33 to acid reservoir 17 of the second concentration stage.

In the second concentration stage, the end gas produced in the sulfuric acid production plant is used as a steam carrier.

Via conduit 3b, the end gas, which contains almost no water vapor, is introduced into the vertical venturi tube 10 of the second condensation stage at a rate of about 113,750 m@3 /h at about 110.degree.

H at a rate of about 24,680 kg/h via the connecting pipe 11, horizontal venturi pipe 12, spray tower 14, separator 15 and conduit 16.
When the wet waste gas containing 2O is about 70℃, it is about 144,740
The terminal gas is discharged at a rate of standard m/h into a terminal gas stack (not shown).

The concentration of sulfuric acid in the vertical venturi tube circuit is approximately 38.9
In terms of weight width, it is approximately 32.1 weight width in a horizontal venturi-spray tower circuit.

Acid is withdrawn from the acid reservoir 13 via conduit 18 at about 70°C and sent to acid cooler 5ai K where it is preheated to about 93°C by heat exchange with the hot acid at about 140°C from the intermediate absorber and from there Through conduit 19 it is fed to a pump 20 which in turn sends it through conduit 22 to nozzle 28 and through conduit 21 to nozzle 29.

Acid is sprayed into the gas stream from nozzle 28 at about 150 m'/h and from nozzle 29 at about ioOm'/h.

Acid is removed from the acid reservoir 17 at 70° C. via the conduit 24 and sent to the acid cooler 5a.

There, it is preheated to about 91° C. by heat exchange with high-temperature acid at 140° C. from the intermediate absorber, and then from there through conduit 24a to pump 25, further through conduit 27 to nozzle 31, and on the other hand through conduit 26 to nozzle 30. sent to.

Approximately 150 m3/h from nozzle 31,
The acid is sprayed into the gas stream at approximately 100 vh.

Via conduit 32, acid is pumped to acid sump 13 at a rate of approximately 93,040 kg/h.

Approximately 38.9 gb of concentrated sulfuric acid is discharged from the acid reservoir 13 via conduit 23 at a temperature of approximately 70 DEG C. at a rate of 78,901 kg/h and is sent to the acid decomposition unit.

Example 3 FIG. 7 shows a single stage concentrator for concentrating sulfuric acid of about 22.6 weight width to about 28.0 weight width.

In the illustrated operating mode, most of the heat required for preheating and evaporative concentration of the acid is met by utilizing the heat generated by the acid produced in the contact process apparatus (not shown), so the total amount of heat is approximately 15.
Approximately 5.4x 106k of Ox 106kcal/h
Only caL/h is the amount of heat that must be supplied from the outside as low pressure steam.

Approximately 100,000 kg of dilute acid having a weight range of approximately 22.6 kg were heated at a rate of 4 from approximately 45°C to approximately 70°C in an acid cooler (not shown).
and then via conduit 93 to acid sump 4 of the concentrator.
Sent to 6.

Approximately 300 kg/h containing water vapor through conduit 37 at approximately 350 kg/h
C. air is introduced into the vertical venturi tube 38 at approximately 18,800 standard m@3 /h (calculated as dry air).

Also, through the conduit 35, approximately 850 kg/h of air at approximately 30° C. and containing water vapor is introduced into the connecting pipe 39 at a rate of approximately 45,000 standard m''/h (calculated value as dry air).

The waste gas saturated with 17,600 kg/h of N20 is transferred to the connecting pipe 39, the horizontal venturi pipe 41, the spray tower 42, and the separator 4.
3 and conduit 44 at approximately 70°C.

The waste gas is then introduced into the condensing group 44a where the water vapor is largely removed by a water spray introduced via conduit 44b.

Water exits the condensing group through conduit 44c.

The waste gas leaves the condensing station via conduit 44e at approximately 20 DEG C. and is then fed again by blower 34 to the concentrator.

High-temperature acid H at approximately 70°C circulates in a vertical venturi tube circuit.
The 2SO4 concentration is about 28 parts by weight and that of the horizontal venturi-spray tower circuit is about 25 parts by weight.

Acid is removed from acid reservoir 45 via conduit 47 at approximately 70°C and sent to an acid cooler (not shown).

There, it is preheated to about 110° C. by heat exchange with the hot acid from the absorber, and from there it passes through conduit 48 to pump 49, which in turn passes it through conduit 50 to nozzle 63, and from there to conduit 50 and nozzle 63.
1 and is sent to the nozzle 62.

from nozzle 62 at approximately 100 m'/h, from nozzle 63
The acid is sprayed into the gas stream at approximately 90 m'/h.

From the reservoir 46 through the conduit 52, the concentration is approximately 25% by weight and 70% by weight.
℃ sulfuric acid is discharged.

A portion of this passes through conduit 55 to preheater 56 where it is preheated to approximately 92° C. with low pressure steam at a flow rate of approximately Lot/h, then through conduit 57 to pump 58 and from there through conduit 60 to nozzle 64. , and the other via conduit 59 to nozzle 65 .

Acid is sprayed into the gas stream from each nozzle 4 at approximately 150 m', zh and from nozzle 65 at approximately 100 m''/h.

Acid is also pumped via conduit 61 to acid sump 45 at a rate of approximately 92,000 kg/h.

Approximately 83,300 sulfuric acid weighing approximately 28% by weight passes through conduit 33.
kg/h.

[Brief explanation of drawings]

FIG. 1 shows the process flow for producing pigment from Australian titanite according to the method according to the first embodiment of the present invention.
Chart, FIG. 2 is a flow chart of the process of producing pigment from Canadian slag according to the method according to the second embodiment of the present invention, FIG. 3 is a flow chart of the process of producing pigment from Canadian slag according to the method according to the second embodiment of the present invention, and FIG. 3 shows S03 production amount of 1000 tons/day; Materials:
02 Decomposition gas of waste acid with high content of air; concentration of decomposed gas: 28.43 volume ratio so 2. 3.86 volume ratio 02s remaining N2 + CO2; and SO2 content after dilution with air in contactor: 12.2 volume ratio ;The first under the condition that
A schematic diagram showing the amount of heat generated at each stage of the contact method apparatus in the case of implementation according to the diagram, Figure 4 shows the amount of SO3 produced:
1000t/day; Material: Decomposed gas of waste acid by atmospheric air; Concentration of decomposed gas: 17. O volume ratio SO2, 1,50 volume ratio 02 + remaining N2 + C02: and SO2 content after dilution with air in the contact device: 875 volume ratio; A schematic diagram showing the state of heat generation in each stage, Figure 5 is a schematic process flow diagram showing the specific usage status of the heat source in the case of implementation according to Figure 1, and Figure 6 is a diagram showing the specific usage situation of the heat source in the case of implementation according to Figure 2. FIG. 7 is a schematic process flow diagram similar to FIG. 5, and FIG. 7 is a schematic flow diagram showing a method according to a third embodiment of the present invention. In addition, in the code used in the drawing, 5,5.1゜5a
, 5a1, 5b are coolers, 10 is a vertical venturi tube,
11 is a connecting pipe, 14 is a spray tower, 38 is a vertical venturi pipe, 39 is a connecting pipe, and 42 is a spray tower.

Claims (1)

[Claims] 1. 802 is catalytically converted to SO3 in each catalyst shelf while supplying S02 produced by the decomposition of sulfate and dilute sulfuric acid to each catalyst shelf, the SO3-containing gas is cooled between the catalyst shelves, and 803 A method for producing sulfuric acid by absorbing sulfuric acid into sulfuric acid includes the following steps: (A) combining the sulfuric acid production step and the treatment step of salt-containing dilute sulfuric acid; (B) decomposing at least the sulfuric acid salts produced in the treatment step; (C) absorbing SO3 from the gas in the contacting step at a temperature of 100 to 200°C at least in intermediate absorption as high temperature absorption;
(D) absorbing said salt-containing dilute salt by direct contact with a hot gas consisting of the end gas of a contact process device and/or a low moisture inert gas heated with heat from said contact process device; (F') At the same time, the thermal energy of the hot acid from at least the absorber of the contact method apparatus is supplied by indirect heat exchange with the salt-containing dilute sulfuric acid; Concentrating the sulfuric acid using a plurality of concentrators connected in series in the direction of flow of the hot gas, each having an independent acid circuit with a different acid concentration; and (G) 803 from the hot catalytic process gas. 2. A method for producing sulfuric acid, characterized in that a small amount of heat is generated in the acid in the absorber when absorbing sulfuric acid (some of which is used for heating dilute sulfuric acid in the acid circulation path in the concentration stage). The method according to claim 1, further comprising decomposing at least a portion of the treated dilute sulfuric acid in step (B). 3. In step (B), the energy of the hot acid from the dryer is further used to The method according to claim 1 or 2, wherein the method is supplied by indirectly exchanging heat with the dilute sulfuric acid contained therein. 4. The method according to any one of claims 1 to 3, wherein the capacity of the gas used for water removal is larger than the capacity of the terminal gas from the terminal catalyst shelf after final absorption of SO3. 5. The method according to any one of claims 1 to 4, wherein the acid concentration decreases from the gas inlet to the gas outlet in each of the independent acid circulation paths. 6. Concentration of the dilute sulfuric acid takes place in at least one concentration stage with several concentrators connected in series, between which the gas stream is mixed with air and/or flue gas. A method according to any one of claims 1 to 5. 7. The concentration of the dilute sulfuric acid is carried out in its flow direction first with air and/or flue gas in at least the first concentration stage and with end gas in the final concentration stage. 6th
The method described in any one of the following paragraphs. 8. Process according to claim 7, wherein the final concentration step is carried out with the addition of air and/or flue gas. 9. The concentration of the dilute sulfuric acid is carried out in its flow direction first with end gas in at least the first concentration stage and with air and/or flue gas in the final concentration stage. 8th
The method described in any one of the following paragraphs. 10. Process according to claim 9, in which the first concentration step is carried out with the addition of air and/or flue gas. 11. The method according to any one of claims 1 to 10, wherein the dilute sulfuric acid is concentrated in a plurality of concentration stages each having acid circuits connected in parallel at °C. 12. The method according to any one of claims 1 to 11, wherein the separation of the salt from the acid is carried out after concentration or between concentration steps. 13 At least a part of the gas heat generated in the contact method apparatus after the intermediate absorption is used to remove water from the dilute sulfuric acid (
- The method according to any one of claims 1 to 12, which is used for heating gas. 14. Claim No. 1, wherein at least a part of the heat generated in the acid in the dryer during drying of the gas introduced into the contact method apparatus is used for heating the dilute sulfuric acid before introducing it into the concentration stage. The method according to any one of items 1 to 13. Claim 1: Part of the thermal energy generated in the absorber acid when absorbing 15SO3 from the hot catalytic process gas is utilized to heat the dilute sulfuric acid prior to its introduction into the concentration stage. - The method according to any one of paragraphs 14 to 14. 16 Claims in which the thermal energy insufficient for the desired concentration of the dilute sulfuric acid is replenished externally to the gas stream at °C before being introduced into the concentration stage and/or between the concentrators of each concentration stage. The method according to any one of Items 1 to 15. 17. Process according to any one of claims 1 to 16, in which the thermal energy insufficient for the desired concentration of the dilute sulfuric acid is provided by heating the dilute sulfuric acid in the acid circuit of the concentration stages. 18 Claims 12 to 1 in which the salt separated at °C throughout the process is dehydrated in advance before being supplied to the decomposition process.
The method described in any one of Section 7. 19. The method according to any one of claims 1 to 18, wherein at least a portion of the concentration is performed using a Venturi tube device. 20. The method according to any one of claims 1 to 19, wherein the concentration is performed under reduced pressure. 21. The method according to any one of claims 1 to 20, wherein the water content of the gas is reduced by condensation after concentration. 22 Claims 1 to 22 in which the decomposition of salt-containing acids and/or salts is carried out in the presence of oxygen or oxygen-rich gas
Which of Section 21 is the method described in Section 1.