FALLSEM2024-25_BCHY101L_TH_VL2024250106791_2024-09-12_Reference-Material-I (2).pdf

Module-7: Industrial applications Water purification methods zeolites (principle, process, advantages and disadvantages), ion-exchange resins ( double /mixed bed (principle, process, advantages and disadvantages), Reverse osmosis (principle, process, advantages and disadvantag...

Module-7: Industrial applications Water purification methods zeolites (principle, process, advantages and disadvantages), ion-exchange resins ( double /mixed bed (principle, process, advantages and disadvantages), Reverse osmosis (principle, process, advantages and disadvantages), Fuels and combustion -LCV, HCV, Bomb calorimeter (numerical) Corrosion Prevention of Corrosion, cathodic protection (Sacrificial anodic protection and Impressed current cathodic protection). 11/11/2024 1  Water Softening Methods ❖ Zeolite (Permutit process) ❖ Ion-exchange ❖ Mixed bed ion-exchange ❖ Reverse Osmosis 11/11/2024 2  Permutit or Zeolite Process o Zeolite is hydrated sodium aluminium silicate having a general formula, Na2OAl2O3.xSiO2.yH2O. o It exchanges Na+ ions for Ca2+ and Mg2+ ions. o Common Zeolite is Na2OAl2O3.3SiO2.2H2O known as natrolith. o Other gluconites, green sand (iron potassium phyllosilicate with characteristic green colour, a mineral containing Glauconite)etc. are used for water softening. o Artificial zeolite used for water softening is Permutit. o These are porous, glassy particles having higher softening capacity compared to green sand. o They are prepared by heating china clay (hydrated aluminium silicate), feldspar (KAlSi3O8-NaAlSi3O8 – CaAl2Si2O8) are a group of rock-forming tectosilicate minerals which make up as much as 60% of the earth’s crust) and soda ash (Na2CO3) 11/11/2024 3 Natural Zeolites: 1. Natrolite - Na2O. Al2O3 4SiO2.2H 2O 2. Laumontite - CaO. Al2O3 4SiO2.4H 2O 3. Harmotome - (BaO.K2O). Al2O3 5SiO2.5H 2O - Capable of exchanging its Na ions 11/11/2024 4  Permutit or Zeolite Process o Method of softening: Na2Ze + Ca(HCO3)2 2 NaHCO3+CaZe Na2Ze + Mg(HCO3)2 2 NaHCO3+ MgZe Na2Ze + CaSO4 2 Na2SO4+CaZe Na2Ze + CaCl2 2 NaCl+CaZe o Regeneration of Zeolite: CaZe (or) MgZe + 2 NaCl Na2Ze + CaCl2 or MgCl2 Brine solution 11/11/2024 5 11/11/2024 6  Zeolite Process o Advantages: o Residual hardness of water is about 10 ppm only o Equipment is small and easy to handle o Time required for softening of water is small o No sludge formation and the process is clean o Zeolite can be regenerated easily using brine solution o Any type of hardness can be removed without any modifications to the process o Disadvantages: o Coloured water or water containing suspended impurities cannot be used without filtration o Water containing acidic pH cannot be used for softening since acid will destroy zeolite. 11/11/2024 7  Ion-Exchange Process o Ion-exchange resins are cross linked long chain polymers with microporous structure o Functional groups present are responsible for ion-exchange properties o Acidic functional groups (-COOH, -SO3H etc.) exchange H+ for cations & o Basic functional groups (-NH2, =NH etc.) exchange OH- for anions. A. Cation-exchange Resins(RH+): - Styrene divinyl benzene copolymers - When sulphonated, capable of exchange H+ 11/11/2024 8  Ion-Exchange Process B. Anion-exchange resins (R’OH): - Styrene divinyl benzene copolymers or amine formaldehyde copolymers with NH2, QN+, QP+, QS+, groups. - On alkali treatment, capable of exchange of OH- 11/11/2024 9 11/11/2024 10 11/11/2024 11  Ion-Exchange Process The Process of Ion-exchange is: 2 RH+ + Ca2+/Mg2+ R2Ca2+/R2Mg2+ + 2 H+ (Cation exchange) R’OH- + Cl- R’+ Cl- + OH- (anion exchange) 2 R’OH- + SO42- R’2 SO42- + 2 OH- (anion exchange) 2 R’OH- + CO32- R’2 CO32- + 2 OH- (anion exchange) Finally, H+ + OH- H2 O Regeneration of exhausted resins: Saturated resins are regenerated: R2Ca2+/R2Mg2+ + 2H+ 2 RH+ + Ca2+/Mg2+ (cation) (Strong acid) (washings) R’2 SO42- + 2 OH- 2 R’OH- + SO42- (Strong base) (washings) 11/11/2024 12  Ion-Exchange Process Note: Hard water should be first passed through the cation exchanger and then Anion exchanger to avoid hydroxides of Ca2+ and Mg2+ getting formed 11/11/2024 13 11/11/2024 14  Mixed Bed Deionizer 11/11/2024 15 11/11/2024 16  Advantages & Disadvantages o Advantages: - Can be used for highly acid and highly alkaline water - Residual hardness of water is as low as 2 ppm. - Very good for treating water for high pressure boilers o Disadvantages: - Expensive equipment and chemicals - Turbidity of water should be < 10 ppm. Otherwise output will reduce; turbidity needs to be coagulated before treatment. - Needs skilled labour 11/11/2024 17  Reverse osmosis Reverse osmosis membrane filters have a pore size around 0.0001 micron After water passes through a reverse osmosis filter, it is essentially pure water In addition to removing all organic molecules and viruses, reverse osmosis also removes most minerals that are present in the water Reverse osmosis removes monovalent ions, which means that it desalinates the water Osmosis is a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one. Membranes: Cellulose acetate, Polysulfone, Polysulfone amide, Polyamide, Poly-acrylonitrile 19  Reverse Osmosis oWhen two solutions of unequal concentrations are separated by a Semipermeable membrane, solvent will flow from lower conc. to higher conc. oThis phenomenon can be reversed (solvent flow reversed) by applying hydrostatic pressure on the concentrated side oIn reverse osmosis, pressure of 15-40 kg/cm2 is applied to sea water. oThe water gets forced through the semipermeable membrane leaving behind the dissolved solids. 11/11/2024 20 11/11/2024 21  Fuels and Combustion 11/11/2024 22  Fuel is a combustible substance, which on combustion produces a large amount of heat, which can be used for various domestic and industrial purposes. Combustion: The process of combustion involves oxidation of carbon, hydrogen etc. of the fuels to CO2, H2O, and the difference in the energy of reactants and the products are liberated as large amount of heat energy which is utilized. Fuel + O2 Products + Heat The primary or main source of fuels are coal and petroleum oils, the amounts of which are dwindling day by day. These are stored fuels available in earth's crust and are generally called "fossil fuels". 11/11/2024 23 11/11/2024 24  Calorific value of fuels The most important property of fuel to be taken into account is its calorific value or the capacity to supply heat. The calorific value of a fuel can be defined as "the total quantity of heat liberated when a unit mass or volume of the fuel is burnt completely". 11/11/2024 25 Does the efficiency of the same quantity of different kind of fuels are the same? For example Answer is No! Calorific Value or the capacity to supply heat "the total quantity of heat liberated when a unit mass or volume of the fuel is burnt completely". 26 Calorific Value: The amount of heat produced by the complete combustion of a material or fuel. Measured in units of energy per amount of material, e.g. kJ/kg. Wood 1500 -3500 Kcal / Kg; Cattle dung 1000- 3700 ; Bagasse 2200 -4400 ; Coconut husks, dry grass and crop residues 3500 3500 FOSSIL FUELS Coal 4000-7000 ; Charcoal 7000 Carbon 8000 ; Fuel oil 9800 Kerosene and diesel 10000; Petrol 10800 ; Natural gas 8600 Coal gas 4000; Bio gas( Kcal/cu mtr) (12 kg of dung produces 1 cu. Mtr gas) 4700-6000. Units: Amount of heat required to raise the temp. of Calorie: 1g of water through 1oC Kilocalories : 1Kg of water through 1oC British Thermal Unit (B. Th. U) : 1pound of water through 1oF Centigrade Thermal Unit (C.T.U) : 1pound of water through 1oC 28 29  Units of heat Calorie - Calorie is the amount of heat required to raise the temperature of one gram of water through one degree centigrade. Kilocalorie (or) kilogram centigrade unit - This is the unit of metric system and is equal to 1000 calories. This may be defined as "the quantity of heat required to raise the temperature of one kilogram of water through one degree centigrade". Thus 1 kcal = 1000 cal. 11/11/2024 30  Units of heat 3. British thermal unit (B. Th. U.) - This is defined as "the quantity of heat required to raise the temperature of one pound of water through one degree Fahrenheit". This is English system unit. 1 B. Th. U. = 252 cal = 0.252 k cal. 1 k cal = 3.968 B. Th. U. 4. Centigrade Heat Unit (C. H. U.) - This is the "quantity of heat required to raise the temperature of one pound of water through one degree centigrade". Thus, 1 k cal = 3.968 B. Th. U. = 2.2 C. H. U. 11/11/2024 31 Units Amount of heat required to raise the temp. of Calorie: 1g of water through 1oC Kilocalories : 1Kg of water through 1oC British Thermal Unit (B. Th. U) : 1pound of water through 1oF Centigrade Thermal Unit (C.T.U) : 1pound of water through 1oC 11/11/2024 32 11/11/2024 33 11/11/2024 34  Characteristic of a good fuel, 11/11/2024 35 11/11/2024 36 11/11/2024 37 11/11/2024 38  Determination of Calorific Value Bomb calorimeter 11/11/2024 39  Calculation m = mass of fuel pellet (g) W = mass of water in the calorimeter (g) w = water equivalent of calorimeter (g) t1 = initial temperature of calorimeter. t2 = final temperature of calorimeter. HCV = gross calorific value of fuel. 11/11/2024 40 11/11/2024 41  Corrections Fuse wire correction. Heat liberated during sparking should be subtracted from heat liberated. Acid correction. Fuels containing Sulphur and Nitrogen if oxidized, the heats of formation of H2SO4 and HNO3 should be subtracted (as the acid formations are exothermic reactions). Cooling correction. The rate of cooling of the calorimeter from maximum temperature to room temperature is noted. From this rate of cooling (i.e., dt°/min) and the actual time taken for cooling (t min) then correction (dt × t) is called cooling correction and is added to the (t2. t1) term. 11/11/2024 42 Corrections: For accurate results the following corrections are also incorporated: (a) Fuse wire correction: As Mg wire is used for ignition, the heat generated by burning of Mg wire is also included in the gross calorific value. Hence this amount of heat has to be subtracted from the total value. (b) Acid Correction: During combustion, sulphur and nitrogen present in the fuel are oxidized to their corresponding acids under high pressure and temperature. S  O SO ΔH= -144,000 cal 2 2 2SO  O  2H O 2H SO 2 2 2 2 4 2 N  5O  2H O 4HNO 2 2 2 ΔH= 3 -57,160,000 cal 11/11/2024 43 The corrections must be made for the heat liberated in the bomb by the formation of H 2SO4 and HNO3. The amount of H2SO4 and HNO3 is analyzed by washings of the calorimeter. For each ml of 0.1 N H2SO4 formed, 3.6 calories should be subtracted. For each ml of 0.1 HNO3 formed, 1.429 calories must be subtracted. (C) Cooling correction: As the temperature rises above the room temperature, the loss of heat does occur due to radiation, and the highest temperature recorded will be slightly less than that obtained. A temperature correction is therefore necessary to get the correct rise in temperature. If the time taken for the water in the calorimeter to cool down from the maximum temperature attained, to the room temperature is x minutes and the rate of cooling is dt/min, then the cooling correction = x  dt. This should be added to the observed rise in temperature 44 11/11/2024 1. 0.72 gram of a fuel containing 80% carbon, when burnt in a bomb calorimeter, increased the temperature of water from 27.3o to 29.1oC. If the calorimeter contains 250 grams of water and its water equivalents is 150 grams, calculate the HCV of the fuel. Give your answer in kJ/kg. Hint; Specific heat of water = s (1 calorie/gram °C = 4.184 joule/gram °C) Solution. Here x= 0.72 g, W = 250g, t1 = 27.3oC, t2 = 29.1oC. HCV of fuel (L) = (W + w) (t1 - t2) cal/g x = (250 + 150) × (29.1-27.3) / 0.72 cal/g = 1,000 cal/g = 1000 cal/g = 1000 x 10-3 / 10-3 Kcal/Kg = 1000 Kcal/Kg 1Kilocalorie= 4.184 Kilojules = 1000 x 4.184 = 4184 KJ/Kg 11/11/2024 45 2. On burning 0.83 of a solid fuel in a bomb calorimeter , the temperature of 3,500g of water increased from 26.5oC to 29.2oC. Water equivalent of calorimeter and latent heat of steam are 385g and 587.0 cal/g respectively. If the fuel contains 0.7% hydrogen, calculate its gross and net calorific value. Gross calorific value = (W + w) (t2 – t1)x specific heat of water x = (3500 +385) × 2.7x1 cal.g-1 = 12,638 cal/g 0.83 NCV = [GCV – 0.09 H(%) × 587] = (12,638– 0.09 × 0.7 × 587) cal/g = (12,638 – 37) cal/g = 12,601 cal/g 11/11/2024 46 3. A sample of coal contains C =93%; H =6% and ash = 1%. The following data were obtained when the above coal was tested in bomb calorimeter. Wt. of coal burnt =0.92g Wt. of water taken =550g Water equivalent of calorimeter =2,200g Rise in temperature =2.42 oC Fuse wire correction =10.0 cal Acid correction =50.0 cal Calculate gross and net calorific value of the coal, assuming the latent heat of condensation of steam as 580 cal/g. Solution: Wt. of coal sample (x) = 0.92 g; wt. of water (W) =550 g; water equivalent of calorimeter (w) = 2,200g; temperature rise (t2-t1) = 2.42 oC; acid correction = 50.0cal; fuse wire correction = 10.0 cal; latent heat of steam = 580 cal/g; percentage of H =6% 47 GCV = (W + w) (t1 - t2) –[acid+fuse corrections] x = (550+2,200) × 2.42 – [50+10] cal 0.92g = 7,168.5 cal/g. NCV = [GCV – 0.09 H × latent heat steam] = (7168.5 – 0.09 × 6 × 580) cal/g = 6855.3 cal/g 48 Solve this! A sample of coal has C=90%, H=8% and ash=1%. When coal is tested in bomb calorimeter, the following are the data: Weight of burnt coal=0.95g; weight of water taken=650g; water equivalent to bomb calorimeter=2500g; rise in temperature=4.50 0C; fuse wire correction=50 cal; acid correction=150 cal and latent heat of condensation of steam as 587 cal/g. Calculate gross and net calorific value of the coal in calories and joules. GCV = 14710.5 cal/g = 61,548.8 KJ/Kg NCV= 14,287.86 cal/g = 59,780.4 KJ/Kg 11/11/2024 49  Dulongs Formula The approximate calorific value of a fuel can be determined by knowing the amount of constituents present: Gross or higher calorific value (HCV) from elemental constituents of a fuel. H = 34500 kcal/kg; C = 8080 kcal/kg; S = 2240 kcal/kg Oxygen present in the fuel is assumed to be present as water (fixed hydrogen). Available Hydrogen = Total hydrogen - Fixed hydrogen = Total hydrogen - 1/8 mass of oxygen in fuel. Dulongs formula for calorific value from the chemical composition of fuel is, 11/11/2024 50  Corrosion 11/11/2024 51 Corrosion Any process of deterioration and consequent loss of solid metallic material, through an unwanted chemical or electrochemical attack by its environment Types Dry or Chemical Corrosion Electrochemical Corrosion 11/11/2024 52  Dry or Chemical Corrosion 1.Oxidation Corrosion 1.Corrosion by other gases 1.Liquid Metal Corrosion 11/11/2024 53  Oxidation Corrosion Oxygen present in the atmosphere attacks the metal surface – formation of oxide layers Mechanism Nature of the Oxide – When oxidation starts, a thin layer of oxide film will be formed on the surface and the nature of the film decides the further action! i.e. Porous film or non-porous film 11/11/2024 54  Factors Influencing Corrosion Nature of the Metal Environment Position in galvanic series Temperature Humidity Overvoltage Presence of impurities in atmosphere Relative areas of anode and cathode Suspended particles Purity of the metal pH Physical state of the metal Silicates Nature of the surface film Conductance Passive character of the metal Formation of O2 conc. cell Solubility of corrosion products 11/11/2024 Flow velocity 55 Forms of Corrosion 11/11/2024 59  Control of Corrosion Corrosion can be controlled by: a) Proper designing b) Proper selection of metal or alloy c) Use of pure metals d) Use of alloys e) Cathodic protection f) Anodic protection g) Use of inhibitors h) Changing the environment i) Application of protective coatings 11/11/2024 60  Cathodic Protection Cathodic protection: Principle is to make the base metal to be protected as cathode by connecting to a highly anodic metallic plate. Two methods of cathodic protection are known: i) Sacrificial anodic protection ii) Impressed current cathodic protection i) Sacrificial anodic protection: o The metallic structure to be protected is connected through a metal wire to a more anodic metal. o This will induce corrosion at the anodic metal. o Thus the more anodic metal sacrifices itself and gets corroded protecting the metallic structure. o Sacrificial anodes known are Zn, Mg, Al and their alloys. o Applications are: protection of underground pipelines, ship hulls and 11/11/2024 other marine devices, water tanks. 61  Sacrificial anodic protection Sacrificial anodic protection - concept e- Mg Mg2+ 11/11/2024 62  Sacrificial Anodes Galvanization of Steel Dip steel sheet in molten zinc. Get a pretty thin coating. Zinc will be anode. Steel exposed by crack is the cathode. Since we have a huge anode having to be served by a small cathode, corrosion rate will be slow. Tiny cathode (steel) Larger Area Large area (Zinc) anode (zinc) An example of a unfavorable area ratio. Bad deal: huge cathode, tiny anode An example of a favorable area ratio. Bad deal: huge cathode, tiny anode 11/11/2024 63  Another Example Zinc is attached to the steel hull of the vessel 11/11/2024 64 11/11/2024 65 11/11/2024 66  Sacrificial Anode for a Pipeline 11/11/2024 67  Aluminium anodes mounted on a steel jacket structure – using galvanic corrosion for corrosion control! Called cathodic protection (aka sacrificial anode) 11/11/2024 68 ii) Impressed current cathodic protection: o Impressed direct current is applied in the opposite direction to the corrosion current to nullify it. o Usually, one terminal of a battery is connected with an insoluble anode e.g. graphite electrode is immersed in black fill containing coke, gypsum, bentonite and sodium sulphate for good electrical conductivity. o The other terminal is connected to the metallic structure to be protected. o Since the current is impressed on the metallic structure, it acts as cathode and thus gets protected. o This method is usually used to protect underground water pipe lines, oil pipe lines, transmission lines, ships etc. 11/11/2024 69  Impressed current cathodic protection Corrosion current of equal magnitude but opposite in direction applied to nullify corrosion current. Pipeline in Sea Water Buried pipeline  Impressed current cathodic protection Corrosion current of equal magnitude but opposite in direction applied to nullify corrosion current 11/11/2024 71  See Exxon Mobil example 11/11/2024 72 ▪ Copper plating: Anode reaction: Cu (s) → Cu2+ (aq.) + 2 e Cathode reaction: Cu2+ (aq.) + 2 e → Cu (s) Electrolyte: Aqueous CuSO4 solution ▪ Nickel plating: Anode reaction: Ni (s) → Ni2+ (aq.) + 2 e Cathode reaction: Ni2+ (aq.) + 2 e → Ni (s) Electrolyte: Aqueous NiSO4 solution ▪ Gold plating: Anode reaction: Au (s) → Au+ (aq.) + e Cathode reaction: Au+ (aq.) + e → Au (s) Electrolyte: Aqueous K[Au(CN)2] solution ▪ Silver plating: ▪ Silver plating: Anode reaction: Ag (s) → Ag+ (aq.) + e Anode reaction: Ag (s) → Ag+ (aq.) + e Cathode reaction: Ag+ (aq.) + e → Ag (s) Cathode reaction: Ag+ (aq.) + e → Ag (s) Electrolyte: 11/11/2024 Aqueous AgNO3 solution Electrolyte: Aqueous K[Ag(CN)2] solution 73