Wednesday, June 3, 2015

Sulfuric Acid - Manufacturing process

Manufacturing process -1

In front of SRG burner & WHB, Baoshan Steel Mill, Shanhai, China

Overview : Classify general sulfuric acid manufacturing process and it will be the following.

1. Classification by raw material 1) sulfur combustion type ... oil recovery sulfur and sulfur raw material 2 of high purity (99.9% or more)) or gold type ... copper, zinc, 3 for the refining gas and sulfide iron ore, such as nickel as a raw material ) Other raw materials ... coke oven gas desulfurization sulfur, the sour gas, flue gas desulfurization recovery SO2, 2, such as waste sulfuric acid decomposition gas. Classification by conversion (simple contact and double-contact) 3. Or energy recovery-oriented or construction costs emphasis

In addition, as a special process

1) wet method 2) non-stationary converter 2) WSA method 3) SULFOX method

I have.
General process: A) raw materials

Sulfur combustion: Modern sulfuric acid manufacturing process, are all "contact". Production method of this is, go through basically the "burning", "conversion" three-step reaction of "absorption".
1) If sulfur to generate the combustion = SO2 (sulfur oil recovery) is the raw material: S + O2 → SO2
2) oxidizing the conversion = SO2 to SO3 and
SO2 + 1 / 2O2 → SO3 (at converter)
3) The absorption = SO3 is reacted with water to produce sulfuric acid H2SO4
SO3 + H2O → H2SO4
Metallurgy formula: → "Introduction", " raw material "reference material is chalcopyrite, in the case of" metallurgy expressions "such as iron sulfide, because it contains a large amount of metal oxide dust during the roasting gas,
1) If the combustion chalcopyrite is of raw materials: 4CuFeS2 + 9O2 → 2Cu2S + 2Fe2O3 + 6SO2 (in smelting furnace) Cu2S + O2 → 2Cu + SO2 (at BOF)
2) removing the metal oxide by a gas purification dry, wet dust collector, to obtain a clean gas.
3) The same 4 and conversion ... sulfur combustion type) the same as the absorption ... sulfur combustion
Other Ingredients: It has clean ones and dirty ones by the raw materials.
Clean SO2 gas (recovery from wells Man load method flue gas desulfurization SO2) → gas drying, conversion, only the absorption of equipment dirty gas -1 (coke oven gas recovery sulfur, the sour gas, such as waste sulfuric acid) → about the same device used dirty gas and metallurgy type-2 (activated coke method desulfurization recovery SO2) → The "dirty gas -1" of the combustion device is not, "gas purification" and later, almost the same as the metallurgy formula
Other Although it is currently unclear whether also are driving, the process of obtaining the SO2 gypsum by thermal decomposition had been adopted in the former communist bloc. Today, we have seen plaster and clay, the process of manufacturing the SO2 and cement clinker from silica sand in the literature overseas.
"Whether used as a raw material?", You can consequence to all "whether profitable". Currently a good recovery sulfur purity can get at low cost, iron sulfide is not used. However, down the purity of the copper and nickel ore, and now that hydrometallurgy have been widely used, refining = increase of sulfuric acid usage (the selfish, refining = was a byproduct of sulfuric acid) it becomes. Of sulfide iron ore, there may be a re-turn.

B) conversion

When you want to increase the conversion rate, method called double-contact (double contact) is best. This course of 2) above, the partially converted gases in the converter to reduce the SO3 By intermediate absorption is intended to increase the overall conversion by conversion and absorption is fed back to converter. In other words, as compared to a normal (single-contact) system, an intermediate absorber tower and the pump tank for the circulating pump, a cooler, and becomes like the need gas heat exchanger for re-heating. The final conversion rate, it depends on the conditions, but is that of a possible 99.9%.
However, in this method, part of the gas sensible heat exiting the converter is absorbed by the acid intermediate absorber tower, since it is released into the cooling water, the recovery amount of energy will be the decrease in comparison with the single-contact .
It does not lead to so much of the conversion, as a way to increase in the same manner as the conversion rate, option is to use a cesium strengthening catalyst, but the placement of the equipment because this case is a single contact is immutable.

C) energy recovery or construction costs?

Burning sulfuric equipment, conversion, all of the processes of absorption since exothermic reaction, is possible to recover the heat in the form of such steam and electricity. This is how to recover to the fullest, or recovery is also the choice of either reduce the construction costs by suppressing.
S (c) + O2 (g) → SO2 (g) + 301.89kJ / mol (combustion) SO2 (g) + 1 / 2O2 (g) → SO3 (g) + 98.87kJ / mol (conversion) SO3 (g) + H2O (l) → H2SO4 (l) + 132.46kJ / mol (absorption)
If you want to focus on energy recovery:
Recovery conversion heat in waste heat boiler of the combustion heat → combustion furnace exit → converter around the waste heat boiler, economizer, super heater, use the boiler feed water to cool the heat of absorption → circulation acid in the air preheater, or We installed a heat recovery system, such as HRS and HEROS. * 1
* 1: HRS US MECS , Inc., HEROS Germany Outotec in the system recommended by the company, to recover the heat of absorption of both SO3 as low-pressure steam.
Moreover, by increasing as much as possible the concentration of the sulfur combustion furnace exit gas, there is also effective to raise the gas temperature. By placing the air blower in the back of the drying tower, it is also possible to recover the heat of compression as an increase of the combustion gas temperature.
If you want to reduce the construction costs:
Cheap Toka there is no consumption destination be recovered vapor or power, or in large-scale plants such as when the device itself is large and expensive, you should reduce the construction costs. The adjustment of the inlet temperature of the converter layers, dry air of the drying tower exit (in the case of refining gas, dry gas SO2) by bubbling, omit the heat exchanger. Furthermore, cooling the gas surrounding the converter by air-cooled heat exchanger, the heated air is released into the atmosphere without heat recovery.
Combustion furnace exit gas it is thought that there is no choice but to cooling in the waste heat boiler, which also reduces the boiler by raising the boiler outlet temperature, it can also be followed by air cool. The pyrite raw material plant in Africa certain country for the roasting furnace exit gas is quenched with water, it was manner which is not at all heat recovery.
Course construction costs if small whole plant equipment will drop. In this case raise the ventilation resistance, so you will need a great deal of power in the blower, to drive the blower in a steam turbine that uses the recovery steam. Ventilation resistance of the entire plant, but was about conventional 35KPa, of recently, it is an example also become 45KPa ~ 70KPa especially in large plants.
Drying tower and the absorption tower but should differ from the original circulation acid concentration, it has also been put to practical use to circulate the same 98% of the sulfuric acid in the pump tank in common. In this case, we need a single concentration controllers and liquid level controllers also not only the pump tank is reduced. I do not have experience.

Manufacturing process -2

Sulfur combustion:
Sulfur combustion -1 :

The accompanying drawings " PFD-1 Please refer to the ". Is this,
• The molten sulfur raw materials and a single contact as much as possible to minimize the cost (energy recovery is not much need)
This is an example of the case.
Molten sulfur is supplied to the sulfur combustion furnace at the pump. Combustion air, after removing the H2O in the gas by contacting the drying tower in 93 ~ 95% H2SO4, will be sent to the sulfur burner. In this flow blower it has been installed in front of the drying tower. Because this person is you can use the carbon steel as the material of the blower, the equipment cost will decrease. Sulfur is burned in the combustion furnace, SO2 - it becomes (10.5 12%). At this time, the gas temperature in the combustion heat will be 1,050 ℃ ~ 1,200 ℃.
S (c) + O2 (g) → SO2 (g) + 301.89kJ / mol
At the same time, it is a small amount in the furnace, but is said to occur also byproduct of SO3 and NO / NO2.
The hot gas is cooled in the waste heat boiler is recovered heat is simultaneously in the form of steam.
The converter inlet temperature, because the action of the catalyst to optimize the 430 ℃ before and after said (if normal vanadium catalyst) to control by adjusting the bypass valve opening degree of the waste heat boiler.
Converter has a catalyst layer of 3-5 stages, usually four stages. Here, the SO2 is oxidized to SO3, because each layer outlet temperature by oxidation heat rises, it does not go not to cool down before it enters the next layer to 430 ℃ or less.
SO2 (g) + 1 / 2O2 (g) → SO3 (g) + 98.87kJ / mol
To reduce the cost of equipment, it is blown to the catalyst layer a low dry air temperature in the conversion, to lower the inlet temperature. It (the case of four-layer) is often placed in a single layer outlet and the three-layer outlet. The inclusive air blowing, such as gas heat exchange and boiler of this part I will be measured reduction of construction cost is unnecessary. Furthermore surplus of heat, indirect cooling, and removed in the air by the gas cooler.
This process is a single contact late final conversion rate is 96-97 percent, by using, for example, cesium strengthening catalyst, depending on the conditions, it is also possible to 99%.
Gas from the converter absorbs the SO3 in the gas in the absorption tower at 98 ~ 98.5% H2SO4, get the product concentrated sulfuric acid by the circulation acid rose concentration is diluted with water.
SO3 + nH2SO4 · H2O → (n + 1) H2SO4
SO3 (g) + H2O (l) → H2SO4 (l) + 132.46kJ / mol
Part of the absorption tower circulating sulfuric acid, will be taken out as a product to the outside of the system. Although not shown in this flow, winter dilution equipment for diluting the product sulfuric acid concentration to 95%, and product cooler comes after this.
Exhaust gas from the absorption tower, SOx in the gas are absorbed and removed by an exhaust scrubber. There are different types of scrubber, but alkali absorption is common. It is not shown in the flow, but you might want to set up a mist Cottrell (wet electrostatic precipitator)) as white smoke measures of exhaust.
In addition, we have omitted to flow, the converter is the one often preheating furnace for the start TokiNoboru temperature is included.
By the way, the preheating of sulfur combustion furnace, heavy oil for preheating the oven (or, LPG) is done by direct heating and comes with a burner.

Sulfur combustion -2 :

PFD-2 please see. Is this
I for the purpose of a-molten sulfur feedstock · DC / DA (double contact double absorption method) and energy recovery increased
It is the case. Of the above-mentioned PFD-1 please compared to.
Air blower is installed after the drying tower, heat of compression of the air is supplied to the combustion gas, it has to be able to recovery. SO2 oxidation heat of the converter, in part, but has been used to raise the temperature of the return SO2 gas from the intermediate absorption tower, it is used to preheat the feed water to the boiler. In addition, to make the superheated steam, This will not drive the air blower.
The recovery of SO3 absorption heat of the intermediate absorption tower, we have established a HRS tower to cool the circulating acid, with the aim of recovery of medium- and low-pressure steam.

Manufacturing process -3

Metallurgy type process:

The accompanying PFD-3 Please see. It has drawn sulfide iron ore, copper, zinc, nickel concentrate (both sulfide) as a raw material of the process of "metallurgy expressions". Even if you want to desulfurization recovered sulfur, such as desulfurization recovery H2S gas as a raw material, it is the same basically. Similar to the aforementioned process-2, Targeting · DC / DA Law and energy recovery increase
Although not described in detail here, in "dry gas purification", the cyclone and dry electrostatic precipitator (hot Cottrell), but the part of the "wet gas purification" various scrubber and wet electrostatic precipitator (mist Cottrell) It is included. In this part, to remove the dust in the gas from the roasting furnace, purpose is to obtain a clean SO2 gas. When arsenic and mercury in the raw material, is halogen and said substance is included, we can set up a dedicated removal equipment of each. Examples of the wet scrubber There are many things but, MECS, Inc. has focused on DynaWave.
Gas became clean enters the drying tower, it will remove absorb the H2O in the gas. From drying tower entrance is allowed to suck the air, and then the converter entrance of the O2 / SO2 ratio = ~ 1.2.
After this is basically does not change with the aforementioned sulfur combustion type, for gas passes through the purification system and the drying tower, the temperature has dropped to about 40 ℃, the catalytic reaction in the converter this optimal ~ 430 ℃ to cause the order to (usually the case of the catalyst) heated up, you can use the SO2 oxidation heat in the converter. Specifically, it is heated by causing the outlet gas and the heat exchange from the respective layers.
Absorption tower and Jogai-to after this is the same as the sulfur combustion.
For the conventional method, it is often becomes low SO2 concentrations in the converter inlet as compared to the sulfur combustion. Hence, the furnace recent metallurgical expression by suppressing the increase of the unreacted N2 components by using oxygenation air mixing oxygen into the combustion air, to lower the SO2 concentration, and those that do not increase the amount of gas It seems there are many. Such as in the case of sour gas from a conventional method and COG, it will not be able to raise the temperature of the gas entering the oxidation heat in too low, the converter. In this case, you need to'll supplemented with heat from outside continuously.
This, whether or not heat balance can take, you can be judged by the following formula.
Blower outlet (the first heat exchanger shell side inlet) gas sensible heat = Q1 Absorption tower entrance (the first heat exchanger tube side exit) gas heat = Q2 The SO2 → SO3 oxidation heat = Q3 in the converter
Q1 + Q3> Q2
Heat balance will take so long. However, because there is heat loss from the device surface of the converter system, in fact
(Q1 + Q3) * 0.9> Q2
It is safe if as a.

Other raw materials:
Clean flue gas desulfurization gas

PFD-4 please see. This is recovered from flue gas desulfurization equipment, such as Wellman Road Law, is the SO2 gas of high concentration in high purity (However, water vapor saturation). Since there is no need of gas purification, gas after removal of the H2O in the direct drying tower, will be sent to the converter. Because usually high SO2 concentration, you need to or use high-density catalyst or diluted with air. Exhaust of the absorption tower, so returned to the flue gas desulfurization gas, not necessarily the high conversion is required.

Dirty gas -1 (desulfurization sulfur waste liquid, waste sulfuric acid, containing H2S gas, etc.)

PFD-5 Please refer to. These raw materials, it is necessary to generate SO2 by first combustion. Because of course it combustion heat is generated, and the waste heat boiler is provided by a heat recovery in the form of steam. After that, it will remove the dust of gas was cooled and the gas at the gas purification equipment. After drying tower is the same as PFD-4, but the exhaust is released into the atmosphere after it was treated with a scrubber. Usually, because SO2 concentration is low, measures must be taken to reduce the H2O in the process gas.

Dirty Gas 2 (flue gas desulfurization gas containing dust)

PFD-6 Please refer to. This is because, as of activated coke law, those containing dust in the recovery SO2 gas, combustion furnace is not required gas purification equipment is necessary. Except there is no combustion furnace is the same apparatus sequence as a "dirty gas -1". However, because SO2 concentration is higher in the case of this gas, it will be rather necessary dilution with air.

Manufacturing process -4

Special process:
Wet method:

Whether the other raw materials any sulfur combustion, the catalytic reaction gas in the generic process is supplied to the converter does not contain H2O. This is to avoid the risk of equipment corrosion and stop time of the catalyst damage. The drying tower is used for the purpose, it has been absorbed and removed the H2O contained by washing the sulfur combustion air and process gas after the gas purification unit in the 93 ~ 95% H2SO4. However, there is also a process of contacting reaction while containing H2O in the gas. This is usually the gas in the beautiful but is also small equipment SO2 concentration is thin production volume, and the product will be only adopted in special conditions that may be a dilute sulfuric acid. Requires no drying tower as equipment, after the converter, the condenser and the cost of equipment and the electrical dust collector is only in place of the absorption tower is you can be kept low. However, because of that can not be concentrated sulfuric acid is that the application of the product is naturally limited, example that has now been adopted it seems that little.

WSA method:

A type of the above-mentioned wet method, but without causing total amount of condensed H2O in the gas, a method of obtaining a high concentration of sulfuric acid by partial condensation, Harudatopuso Inc. (Denmark) was developed in the mid 1980s. Gas containing H2O is oxidized SO2 is directly at the converter, the generated SO3 is a gaseous H2SO4 reacts with H2O. This H2SO4 vapor by partial condensation in a glass condenser to get the concentrated sulfuric acid. Oxidation heat generated by the converter will be recovered by the molten salt boiler. Concentrated sulfuric acid concentration of purification is determined by the H2O content in the gas. If 10% or less, Toka it possible to obtain 98% H2SO4. Moreover, by changing the SO3 Gasugu H2SO4 generated by converter, so remains SO3 concentration in the gas is always low, it means that same equilibrium with DC / DA method is shifted to the side to promote the oxidation of SO3, the final conversion Toka equal to or greater than 99%. Originally, the simple contact-type exhaust sulfuric equipment, such as boiler combustion gases, it was a process for producing sulfuric acid from a very thin SO2 concentration of the gas, at present, it and the high density SO2 from metallurgical type roasting furnace gas, H2S from oil refining, coke oven gas purification H2S, sulfur sludge, such as waste sulfuric acid and sulfuric acid drainage from the petrochemical, can accommodate a wide variety of raw materials, there is a construction track record 100 groups close to the world. In Japan, there was a facility from the petrochemical waste sulfuric acid, it is not currently for the generation process of the waste acid was discontinued. Globally, we have argued that already have a track record of more than 130 groups. (November 2014 currently) As compared with the general process, also in the plant cost, advantageous and manufacturers in the utility surface (Topuso Inc.) has claimed. However, in the molten sulfur raw materials, the original wet method because moisture is less in the air benefits I will think less. Also in the non-ferrous metal smelting, because the cost of the furnace and the gas purification part is greater than the sulfuric acid production facility, it will presumably cost benefit is small compared to other sulfur source. → WSA schematic flowexperience in smelting gas Direction you are interested contact us please. Topuso's Japanese distributor, we will introduce the OTC.

SULFOX method:

those MECS, Inc. has developed, like the WSA method, it is wet sulfuric acid production process. It unique in this process, not only a thin SO2, is that it is a can produce sulfuric acid by oxidation in the converter within the catalyst also the H2S gas. Again by adjusting the condensing temperature? It obtained a high concentration of sulfuric acid, and then you have.

Non-stationary converter:

The catalyst of the converter is not divided into multiple stages, in a manner that switching between the entrance and exit of SO2 gas at regular time intervals, it is that you omit the converter around the gas heat exchanger. After preheating the catalyst, when you through the cold SO2 gas from the catalyst top, because among the first is the catalyst temperature oxidation start temperature or higher SO2 + 1 / 2O2 → SO3 Reaction of go, but you have cold gradually gas inlet side. If the gas inlet is now switch to from the catalyst bottom, the oxidation by touching the high temperature of the catalyst is continued, catalyst upper part which has been cold will be heated by the heat of reaction. If you have cold the bottom, now also conducts SO2 gas from the top ... If you continue this reaction sufficient conversion rate is obtained, thing.
It is a technology that has been developed in the former Soviet Union, there was operational cases until recent years in China. But the will not big final conversion rate is obtained, it is questionable whether really stable conversion rate can be maintained. In Japan there was a engineering company that sells this technology, but it does not have heard the story that was sold.
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