ptec 107 process science

Spring, 2012Session 4 – General Chemistry Pt 2

Inorganic chemistry applications to process technology

Analytical methods

Pulp and paper mills Refineries Energy Generation Food processing Water and wastewater treatment

Cooking (digestion) Oxygen delignification Chlorine bleaching Chemical recovery

Cooking or digestion – depolymerization by means of sodium sulfide and sodium hydroxide

NaOH + Na2S + H2CO3 = NaHS + Na2CO3 + H2O

1.Na2SO4 + 2 C → Na2S + 2 CO2

2.Na2S + Na2CO3 + Ca(OH)2 ←→ Na2S + 2NaOH + CaCO3

3.CaCO3 → CaO + CO2

4.CaO + H2O → Ca(OH)2

http://www.youtube.com/watch?v=QN1Ml8M7U8A

Hydrodesulfurization Hydrogen sulfide reaction with amines Sulfur plant

C2H5SH + H2 → C2H6 + H2S MoS catalytic hydrodesulfurization

H2S + RNH2 (amine) = RNH3HS Methyldiethanolamine (MDEA)

2H2S + 3 O2 → 2 SO2 + 2 H2O (step 1) 2H2S + SO2 → 3S + 2H2O (step 2) 2H2S + SO2 → 3S + 2H2O (overall reaction) Other reactions on surface of catalyst

◦ COS + H20 → H2S + CO2

◦ CS2 + 2H20 → 2H2S + CO2

◦ COS and CS2 are formed in the furnace

Combustion Hydrogen generation Fuel cells

CnH2n+2 + (3n/2 + ½)O2 = nCO2 + (n+1)H2O (complete combustion)

CnH2n+2 + (n + ½)O2 = n CO + (n+1)H2O (incomplete combustion)

Steam reforming: CH4 + H2O = CO + 3H2 or CH4 + 2H2O = CO2 + 4H2

Water gas shift reaction: CO(g) + H2O(v) → CO2(g) + H2(g)

H2 + ½ O2 = H2O

Based upon combination of oxygen and hydrogen to make water and produce electricity

Different types of fuel cells (phosphoric acid, alkali, proton exchange membrane, etc.)

http://americanhistory.si.edu/fuelcells/basics.htm

2H2O = 2H2 + O2

Hydrogen gas reservoir

Hydrogen loses electrons, is oxidized, at the anode Oxygen gains electrons, is reduced, at the cathode To electrolyze 0.001 gram mole of water to produce

0.0005 gram mole of oxygen gas (O2) and 0.001 gram moles of hydrogen gas (H2) requires the transfer of one faraday of electricity (96.485 coulombs)

0.001 gram mole of hydrogen is equivalent to 22.4 ml of gas at standard conditions

For a cell resistance of 20 ohms and a 3 volt battery, the current flow through the cell would be 3 V / 20 ohms = 0.15 A (0.15 coulombs/second). At this current flow, assuming 100% efficiency, it would take about 11 minutes to generate 22.4 ml of gas

Sugar refining Beer brewing Sterilization

Primary treatment (physical separation) Secondary treatment (biological oxidation) Disinfection Tertiary treatment (chemical treatment)

KAl(SO4)2 ·12H2O + 2Ca(OH)2 = Al(OH)3 + 2CaSO4 + KOH

Cl2 + H2O = HClO + HCl

Lab glassware Water analysis

◦ Physical◦ Chemical

Oil analysis◦ Physical◦ Chemical

Beakers – used to contain liquids for mixing together and can be used for rough volume measurements

Pipette – used to deliver measured amounts of liquids into beakers and flasks

Burette – used to deliver measured amounts of liquids for titration

Crucible – used to dry or ash solids

Color (comparison to color standards) Turbidity (obscuration of light)

◦ Measured in turbidity units (JTU, NTU) Settleable solids (Imhoff cone) in ml solids/l

liquid Suspended solids (filter, dry solids at 103 deg C)

measured as mg of solids per liter of liquid, mg/l Dissolved solids (filter, dry filtrate at 103 deg C)

mg/l Volatile suspended solids (fire dry solids at 600

deg C) mg/l

Turbidity and turbidimeters

Settleable solids by Imhoff cone

Suspended, volatile and dissolved solids

Standard solutions used for analysis pH measurement by electrodes Alkalinity (carbonate and hydroxide content) Hardness (calcium and magnesium

concentrations)◦ < 50 mg/l is soft water◦ > 150 mg/l is hard water

Iron and manganese (cause color and stains) Trace metals (zinc, arsenic, etc.)

pH meter

Hardness (total and calcium)

Organic material◦ Chemical Oxygen Demand (COD) for amount of

oxygen necessary to oxidize organic material mg oxygen required/l – determined by a chemical oxidation

◦ Total Organic Carbon (TOC) for amount of carbon (oxidation of organics to carbon dioxide and measurement of carbon dioxide) mg carbon/l – determined by an instrument

◦ Organic acids (absorption and chemical neutralization ) mg/l

Total Organic Carbon (TOC)

Water pH testing http://www.youtube.com/watch?v=GkbcKrcE9xY

Water hardness http://www.youtube.com/watch?v=npMq8b0d3a8

Jar tests are used to determine the effectiveness of chemicals added to coagulate and flocculate wastewaters, and to precipitate species. In these tests, different chemicals are added in different doses to see what dose causes the best coagulation and settling.

Jar test apparatus and results

Physical testing◦ Density◦ Distillation fractions◦ Gas chromatograph

Chemical testing◦ Elemental testing by ignition◦ Boiler feed water analysis

Ca(HCO3)2 + NaOH = CaCO3 + NaHCO3 + H2O (hardness)

NaHCO3 + HCl = NaCl + CO2 + H2O (bicarbonate alkalinity)

Others (silica, iron, etc.)