PRODUCTION OF SULFURIC ACID DCDA POCESS PRODUCTION OF SULFURIC ACID

PREPARED BY : NAME EN NO: 1. PATEL VIVEK 140110105046 2. PAUL SOURAV 140110105047 3. PITHADIYA MAULIK 140110105048 4. RADADIYA ROSHAN 140110105049 5. RAVAL KUNJAN 140110105050

COLLEGE NAME: G.H.PATEL COLLEGE OF ENGG & TECH. BRANCH : CHEMICAL 2nd year SEM: 3rd SUBJECT: CHEMICAL PROCESS INDUSTRIES - 1

Sulfuric acid PURE 100% H2S04 Mol. Wt. 98.08 M.P. 10.5. C B.P. 340. C SOLUBILITY : COMPLETELY MISCIBLE WITH H2O WITH LARGE HEAT OF SOLUTION .SO3 SOLUBLE IN H2S04 TO GIVE VARYING PERCENTAGE OF OLEUM.

Manufacturing by DCDA Process Raw materials Sulfur Pyrites CuS ,ZnS, PbS, MoS2 H2S Sources Sulfur source

Chemical reactions Three Step Process 1) S + O2 SO2 2) SO2 + 1/2O2 SO3   2) SO2 + 1/2O2 SO3 3) SO3 + H2O H2SO4

Process The process can be divided into five stages: combining of sulfur and oxygen purifying sulfur dioxide in the purification unit adding excess of oxygen to sulfur dioxide in presence of catalyst vanadium pentoxide, with temperatures of 450 °C and pressure of 1-2 atm sulfur trioxide formed is added to sulfuric acid which gives rise to oleum (disulfuric acid) the oleum then is added to water to form sulfuric acid which is very concentrated.

Oxidation of Sulfur Air 93% H2SO4 Sulfur 10-12% SO2 Steam Water

Oxidation of Sulfur Process: - Air drying tower with acid - Sulfur is injected into burner - Reaction Temperature 2000°F - Exothermic reaction must be cooled - Steam recovered Kinetic Effects - Oxidation of sulfur dioxide is slow and reversible - The reaction requires a catalyst and 426.7°C temperatures The reaction is exothermic and sensitive to excessive heat Equilibrium Constant (The degree at which the reaction proceeds is temp. dependent) 

log Kp = 4.956 - 4.67 T T = absolute temp. in kelvin Kp = equilibrium constant as a function of partial pressure of gases Kp = ( PSO3 ).5 /( PSO2 PO2 ).5

Purification unit Purification unit This includes the dusting tower, cooling pipes, washing tower, drying tower, arsenic purifier and testing box. Sulfur dioxide has many impurities such as vapours, dust particles and arsenous oxide. Therefore, it must be purified to avoid catalyst poisoning . In this process, the gas is washed with water, and dried by sulfuric acid. In the dusting tower, the sulfur dioxide is exposed to a steam which removes the dust particles. After the gas is cooled, the sulfur dioxide enters the washing tower where it is sprayed by water to remove any soluble impurities.

In the drying tower sulfuric acid is sprayed on the gas to remove the moisture from it. Finally, arsenic oxide is removed when the gas is exposed to ferric hydroxide.

OVERALL FLOW CHART

DCDA The next step to the Contact Process is DCDA or Double Contact Double Absorption. In this process the product gases (SO2) and (SO3) are passed through absorption towers twice to achieve further absorption and conversion of SO2 to SO3 and production of higher grade sulfuric acid. SO2-rich gases enter the catalytic converter, usually a tower with multiple catalyst beds, and are converted to SO3, achieving the first stage of conversion. The exit gases from this stage contain both SO2 and SO3 which are passed through intermediate absorption tower

where sulfuric acid is trickled down packed columns and SO3 reacts with water increasing the sulfuric acid concentration. Though SO2 too passes through the tower it is unreactive and comes out of the absorption tower. This stream of gas containing SO2, after necessary cooling is passed through the catalytic converter bed column again achieving up to 99.8% conversion of SO2 to SO3 and the gases are again passed through the final absorption column thus resulting not only achieving high conversion efficiency for SO2 but also enabling production of higher concentration of sulfuric acid.

The industrial production of sulfuric acid involves proper control of temperatures and flow rates of the gases as both the conversion efficiency and absorption are dependent on these.

Oxidation of Sulfur Dioxide Gas Cooling SO3 Gas SO2 Gas 93% H2SO4

Because of the large effect temperature plays on the reaction, multiple catalyst layers are used, with cooling between each step. Additionally, as the partial pressure of SO3 increases, further reaction is limited. This is overcome by removing the SO3 after the third stage to drive the reaction to completion. CATALYST: MOST WIDELY USED CATALYST IS VENADIUM P ENTOXIDE DISPERSED ON A POROUS CARRIER IN PELLET FORM.

Oleum Production Sulfuric acid with additional SO3 absorbed 20% Oleum contains 20% SO3 by weight in the oleum Common strengths of oleum are 20, 30, 40, 65 percent. To produce 20 and 30 percent oleum, only requires an additional absorption tower. Oleum is used in reactions where water is excluded SO3 + H2SO4 H2S2O7 (disulfuric acid)

Reaction By-products / Heat Integration 57 to 64% of the energy input generates steam Steam energy is used to drive the turbine that supplies power to the main air blower Additional steam remaining is tolled internally for other plant operations SO2/SO3 is vented in small amounts and is federally regulated. Heat Integration Steam is used to pre-heat and vapor from the absorption towers used to cool Minimizes the cost of manufacturing to maximize the profit.

Production Considerations Metal corrosion is a big issue in the manufacture of sulfuric acid. Special alloy metals must be used to guard against excessive corrosion. Nickel, chromium, molybdenum, copper, an silicon are the most important elements that enhance corrosion resistance of alloys. important variables for corrosion Concentration of the acid Temperature of service Speed of flow in pipes and equipment Alloy element make-up

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