TOPIC: THE INDUSTRIAL PRODUCTION OF SULPHURICACID AND ITS USEFULNESS

VENUE: COLLEGE OF SCIENCE AND TECHNOLOGY (CST)CONFERENCE ROOM

DATE: FRIDAY, APRIL 7, 2017.

TIME: 11.00AM

GUESTSPEAKER: MR. SAMUEL IBILOYE

(B.Sc Chemistry, M.Sc Analytical/Environmental Chemistry)Quality Control Manager,African Hydro Agric Chemicals Nig. Ltd.Agbara.

1

INDUSTRIAL PRODUCTION OF SULPHURIC ACID AND ITS USEFULNESS

Process description

Industrial production of Sulphuric Acid Plant is

based on the most modern method called Double

contact Double Absorption (DCDA) process and is

designed to produce very high tonnage on 24

hours of normal operation using elemental sulphur

as feed stock (See flow chart).

2

Raw materials required are:-1. Sulphur 2. Oxygen 3. Demineralised water 4. Sulphuric acid H2SO4

Chemical Reaction1. S(s) + O2 SO2(g)

sulphur oxygen sulphur dioxide 2. 2SO2(g) + O2(g) 2SO3(g)

sulphur dioxide oxygen sulphur trioxide 2. SO3(g) + H2SO4(aq) H2S2O7(aq)

sulphur trioxide sulphuric acid oleum (100%) 4. H2S2O7 (aq) + H2O(1) 2H2SO4(aq)

oleum demineralised water sulphuric acid 98%

V2O5

3

AIR AND GAS CIRCUIT

• Air for sulphur burning is supplied through mainAir Blower. The air is passed through dryingTower to remove practically all moisturecontent.

• High efficiency Deminster pads are on top of thedrying tower to prevent acid carry over in air.

• Sulphur is burned in the sulphur furnace withdried air to produce gas containing 10.5% SO2.

4

• This is a highly exothermic reaction, thereforeheat is released which raises the gastemperature up to about 1000oC.

• The hot gases from sulphur burner is cooled inwaste Heat Boiler to about 430oC.

• The conversion of SO2 to SO3 is optimised bycarrying it out in four stages in the converterbed.

• The cooled gases from waste heat boiler Ipasses through the 1st catalyst bed of theconverter where approximately 60%conversion is achieved. This increases thetemperature of the outlet gases to about 600oCdue to exothermic reaction.

5

• The hot gases are cooled in waste heat boilerII and fed to the second catalyst bed of theconverter.

• The waste heat is used to produce saturatedsteam at 17.5 kg km2 pressure.

• A cumulative conversion of about 88% isachieved in the 2nd bed and 94% in the 3rd

bed of the converter.• The hot gases coming from 2nd bed are taken

through the tube side of Hot heat exchangerand fed to the 3rd bed of the converter.

• Gases leaving the 3rd bed are cooled in thetube side of the cold heat exchanger.

6

AIR CIRCUIT

• Acid circuit is designed to remove moisture inair and absorb SO3 from gas to producesulphuric acid. The hot acid from finalAbsorption Tower, Interpass Absorption towerand Drying Tower are returned to the Acidproduction tank.

• Hot acid from Acid production tank is pumpedby acid circulation pump through plate heatexchanger where it is cooled by cooling Towerand fed to the respective towers.

7

• The concentration of the acid is continuouslymeasured by concentration analyser andindicator and controlled by addition ofdemineralised water.

• The level of acid in the production tank isregulated by transferring the excess acid inthe level control valve as product to the Acidstorage tanks.

8

Water & Steam Circuit

• The circuit is designed to produce low pressuresteam at 17.5 kg/cm2 and 207oC utilizing heatgenerated in the plant.

• The steam is used partly for in-plantconsumption and the balance is transferred toAlum plant.

• A deaerator is mounted on Boiler feed watertank.

• Steam is introduced at 0.5 kg/cm3 to removedissolved oxygen.

9

• Make up demineralised water from DM watertank is fed at the top of the deaerator andcollected in the Boiler fed water tank.

• Cold gases from Interpass Absorption Tower(IPAT) are passed through high efficiencycandle filter for removal of acid mist.

• Outlet gases from candle fitter are heated toreaction temperature in the shell side of coldheat exchanger.

• Finally, in the shell side of Hot Heat Exchanger,located after the 2nd bed of the converter andfed to 4th bed of the converter.

10

• In the 4th bed, a cumulative conversion of99.75% is achieved.

• Gases leaving the 4th bed are cooled in theeconomizer to preheat boiler feed waterbefore being fed to the Final Absorption Tower(FAT) where SO3 produced in the 4th bed isabsorbed in the circulating sulphuric acid.

• Reacting gases from FAT are passed throughthe Demister pad mounted on top of FAT foracid mist removal.

• The gases are passed through Alkali scrubberto reduce SO2 emission level further and thenvented through a stack mounted on the alkaliscrubber.

11

Note – the waste heat boiler system should betested at test pressure in the presence of boilerinspector and necessary clearances should beobtained before plant commissioning.• All instruments which are installed should be

tested and calibrated to ensure properfunctioning.

• Electrical systems including Motor Controlcentre, interlocking system and overloadtripping system should be checked to ensurenormal functioning.

• Laboratory tests are carried out for raw materials:-Sulphur - % moisture, % acidity, % ash +bituminous matter and percent purity.

12

ANALYSIS OF CONCENTRATED SULPHURIC ACID

• The following parameters are usually analysed

in the laboratory:

total acidity, residue on ignition, iron, chloride,

lead, arsenic, oxidizable impurities, ammonia,

nitrate, selenium, manganese, copper, zinc and

specific gravity.

• There are four types of sulphuric acid:

technical grade, battery grade, chemically pure

grade and analytical grade.13

• Operation A: involves heating of sulphurburner, gas is fired into the furnace in thepresence of oxygen from blower to heat thefurnace and raise the temperature gradually.

• Operation B: involves the recovering of heatfrom the furnace by dry air and heating allthe catalyst by dry hot air to a temperatureabove 125oC.

• Operation A & B are carried out alternativelyseveral times till the gas leaving the catalystis above 125oC.

14

• Operation C: this is to finally heat the plant forsulphur firing. Hot combustion gases arepassed directly through the converter to raisethe temperature of all beds.

1st day – max. possible slow rate 35oC /hr.2nd day – raise from 300oC to 400oC at the

same rate.3rd day – raise temperature to 500oC.4th day – raise furnace temperature to 600oC

for start up of new plants.Subsequent start up, temperature can beraised to 50oC/hr.

15

DE-IONISED WATER

• Demineralised water is produced by passingsoftener water into Cation and AnionExchangers to remove positively charged andnegatively charged ions respectively.

• Cation & Anion exchangers are loaded withresins.

16

STORAGE

• Sulphuric acid is stored in a large mild steeltank whose inside is lined with acid resistantBricks.

• The acid is sold in acid resistant kegs of 20litres, 30 litres, 200 litres or in tankers to bigcompanies such as NNPC, Fertilizer plants,PHCN, etc.

17

IMPORTANCE /USEFULNESS OF SULPHURIC ACID

• More sulphuric acid by mass is producedworldwide than any other chemicals.

• It has been found that the production ofsulphuric acid closely mirrors historical eventssuch as major wars that affect a country’seconomy.

• For this reason, some economists use sulphuricacid production as a measure of a country’sindustrial strength.

18

• Sulphuric acid is used directly or indirectly innearly all industrial processes, including theproduction of fertilizers, detergents, paints,in ore processing, steel production and watertreatment, approximately 250 million tonnesare produced annually across all continents.

19

APPLICATION /USAGE S/N Application/Usage Sector

1. Used as an electrolyte in lead accumulator andbatteries and in refining of metals byelectrolysis.

The batteryindustry.

2. Used to clean or pickle metals beforeelectroplating or enameling.

Electroplatingindustry.

3. Used for manufacturing of pigment e.gtitanium (vi) oxide and bariumtetraoxosulphate (vi) for use in plant and dyes.

Paints/pigmentindustry. Textileindustry.

4. Used as a dehydrating agent in the nitration ofcompounds used for making explosives.

Explosiveindustry

5. Used in synthesis of phenol and alkylation ofisobutane

Organic chemicalindustry

6. Used for purification of crude oil and in themanufacture of artificial silk.

Petroleum/TextileIndustry 20

7. Recovery of fatty acids in soapmanufacturing and sulphonation ofdodecyl benzene

The soap anddetergent industry

8. Used in preparation of many importantchemical compounds e.g HCl and HNO3

acid, metallic tetraoxosulphate

Chemical industries

9. Used for production of fertilizers likeurea, single superphosphate and N.P.Kassisting to increase the agriculturaloutput of the country

Fertilizer Industry.

10. Used for production of Aluminumsulphate.

Alum industry.

11. Used for production of demineralisedwater

Water treatmentplants.

21

A typical sulphuric acid plant22

REFERENCES

• The Columbia Electronic Encyclopedia, 6th ed.Copyright 2012, Columba University Press. Allrights reserved.

• Sulphuric acid plant. African Hydro Agric chemicalsLtd. Opic Industrial Estate. Agbara, Ogun State.

• Nigerian Industrial Standard N1.5 788:1992.

• Lunge, Theoretical and Practical Treatise on theManufacture of Sulphuric acid and Alkali, with thecollateral Branches, 3rd ed., vol 1, part 2. page 975.(London, England, Gurney and Jackson 1903).

23

Thank You For Listening

24