1. ENERGY CONSERVATION IN CHEMICAL PROCESS INDUSTRIES
Dr.V.SIVASUBRAMANIAN
Associate Professor
Former Head
Chemical Engineering
NIT Calicut

2. DEPARTMENT OF CHEMICAL ENGINEERING

3. Agenda Introduction Energy Conservation in Reactors
Energy Conservation in Packed Beds
Energy Conservation in Heat Exchangers
Energy Conservation in Evaporators
Energy Conservation in Crushers and Grinders
Heating and Cooling Requirement in Distillation Columns
Energy Conservation in Dryers
Energy Conservation in Pumps
Methodology of Optimizing Energy Use
Areas of energy Optimization in CPI
Energy Efficiency Improvement and Cost Saving Opportunities in Petrochemical Industry
Overview of Water & Waste Reduction Session
Brief outline of Method & Benefits of Conducting Study
Case Studies from industries indicative of a broad range of 3Rs measures
Case Studies of Water & Waste Efficiency at KSC and Cape Canaveral
Case Study of Incorporation of Water & Waste Management Work into a Sustainable Development Strategy for the Las Lajas Coop.

4. CHEMICAL ENGINEERING DEPT NIT CALICUT
1. Introduction
CHEMICAL PROCESS
UNIT PROCESS
UNIT OPERATION
Self Introductions by audience (name, business & interest in water & waste reduction)
Speaker performed these studies in the aerospace, automotive, Chemical, Commercial Product, Food, Electroplating, Mining, Petroleum, Pulp & Paper, and Public Sector.
Conducted water use reduction workshops offered by RMOW and at Canada’s First National Conference (Winnipeg 1993)
Presently train and lead teams of industry staff to complete resource conservation studies and implement solutions
Is President of Enviro-Stewards Inc., a firm whose mission is to “help our clients conserve their resources and effectively address their environmental liabilities.
CHEMICAL ENGINEERING DEPT NIT CALICUT

5. Figure I Input – Processing – Output System
RECYCLE
DISPOSAL
WASTE
INPUT
PROCESSING
OUTPUT
CHEMICAL ENGINEERING DEPT NIT CALICUT

6. Chemical Reaction Types in Petrochemical Industries
1 Pyrolysis
16 Oxidation
2 Alkylation
17 Hydrodealkylation
3 Hydrogenation
18 Isomerization
4 Dehydration
19 Oxyacetylation
5 Hydroformylation
20 Oligormerization
6 Halogenation
21 Nitration
7 Hydrolysis/Hydration
22 Hydrohalogenation
8 Dehydrogenation
23 Reduction
9 Esterification
24 Sulfonation
10 Dehydrohalogenation
25 Hydrocyanation
11 Ammonolysis
26 Neutralization
12 Reforming
27 Hydrodimerization
13 Oxyhalogenation
28 Miscellaneous
14 Condensation
29 Nonreactor processes
15 Cleavage
U.S.-EPA (1993)

7. CHEMICAL ENGINEERING DEPT NIT CALICUT
Unit Operations
Liquid-vapor separation (distillation, evaporation, stripping)
Liquid-liquid separation (extraction, decanting)
Solid-liquid separation (centrifugal, filtration)
Solid-gas separation (filtration)
Solid-solid separation (screening, gravity)
CHEMICAL ENGINEERING DEPT NIT CALICUT

8. 2.Energy Conservation in Reactors
Ideal Reactors
Batch reactor, or BR (b) Plug flow reactor, or PFR and
(c) Mixed flow reactor, or MFR

9. Broad Classification of Reactor Types
(a) The batch reactor. (b) The steady-state flow reactor. (c), (d), and (e) Various forms of the semibatch reactor
CHEMICAL ENGINEERING DEPT NIT CALICUT

10. Material Balance for the Element of Volume of Reactor

11. Material Balance for the Element of Volume of Reactor

12. Energy Balance for the Element of Volume of Reactor

13. Energy Balance for the Element of Volume of Reactor

14. AGITATION PROCESS VESSEL

15. Mixing Impellers
(a) three-blade marine propeller; (b) open straight-blade turbine; (c) bladed disk turbine; (d) vertical curved-blade turbine; (e) pitched-blade turbine

16. Design of Agitated Vessel

18. Power Consumption in Agitated Vessel
Np power no.
P power in kW
gc Newton’s law proportionality factor
n rotational speed r/s
Da diameter of impeller in m
 density in kg/m3

19. Power Correlation hc individual htc for outside of coil, W/m2-C
S1, S2, Sn – Shape factors
hc individual htc for outside of coil, W/m2-C
Dc outside dia of coil tubing, m
k thermal conductivity, W/m-C
Cp specific pressure, J/g-C
 absolute viscosity, cP
w absolute or surface temp

20. Swirling flow pattern with a radial-flow turbine in an unbaffled vessel

21. Prevention of Swirling

22. Multiple turbines in tall tanks

23. Draft tubes, baffled tank
(a) Turbine (b) propeller

24. Energy Efficiency in Reactors
Agitator motor current monitoring:
VFD deployment –feasibility.
Accurate mass transfer for reaction by mass flow meters or vortex/magnetic flow meters.
Recovery of heat in case of Exothermic Reaction
Batch –Automation to control the reaction within a narrow range, saving energy consumed.

25. 3. Energy Conservation in Packed Beds
Nusselt Number
hw individual htc of gas film near tube wall
Dp diameter of particle
kg thermal conductivity of gas
Prandtl Number,

26. 4. Energy Conservation in Heat Exchangers
Single pass tubular condenser

28. Energy Balance in Heat Exchangers
flow rate of stream
q = Q/t = rate of heat transfer into stream
Ha, Hb enthalpies per unit mass of stream at entrance and exit

29. EXTENDED SURFACE EQUIPMENT
Types of extended surface: (a) longitudinal fins;
(b) transverse fins.

30. 5. Energy Conservation in Evaporators
Types of Evaporators

31. Climbing-film, long-tube vertical evaporator

32. Evaporator Capacity and Economy
q rate of heat transfer through heating
surface from steam
Hs specific enthalpy of steam
Hc specific enthalpy of condensate
s latent heat of condensation of steam
rate of flow of steam

33. Methods of Feeding in Evaporator
Patterns of liquor flow in multiple~effect evaporators:
(a) forward feed
(b) backward feed
(c) mixed feed
(d) parallel feed

34. 6. Energy Conservation in Crushers and Grinders
Rittinger’s Law
Kick’s Law
Bond’s Law

35. 7. Heating and Cooling Requirement in Distillation Column
If saturated steam is used as the heating medium, the steam required at the reboiler
steam consumption
vapor rate from reboiler
s latent heat of steam
 molal latent heat of mixture

36. If water is used as the cooling medium in the condenser and the condensate is not subcooled, the cooling-water requirement is
water consumption
T2 - Tl = temperature rise of cooling water

37. 8. Energy Conservation in Dryers
Tray Dryer

38. Temperature Patterns in Dryers
batch dryer
continuous countercurrent adiabatic dryer

39. Calculation of Heat Duty
Heat transferred per unit mass of solid

40. 9.ENERGY CONSERVATION IN PUMPS

58. 10. Methodology of Optimizing Energy Use
Measure and benchmark consumption. Compare with globally accepted norms.
Carryout energy audit and energy balance.
Examine availability of more energy efficient processes and equipment with higher efficiencies. Implement new technologies bringing in a reduction in energy & raw material consumptions.
Reduce cycle time by eliminating non-value adding activities.

59. Identify areas of losses and plan methods to reduce losses.
Reuse waste, harness waste streams.
Replace higher form of energy use by low grade / low cost / renewable energy.
Minimize transmission losses.
Measure and control.

60. 11. Areas of energy Optimization in CPI
1. BOILERS AND STEAM USAGE
For Solid fuel fired boilers: Convert stoker fired boilers to FBC
Optimize excess air. Provide continuous monitoring with auto adjustment of oxygen trim in large boilers and periodical checking in smaller boilers.
Preheat combustion air with waste heat
Install variable frequency drives (VFD) on large boiler combustion air fans having variable loads.
Burn waste stream if permitted, use bio waste like coconut kernel, rice husk, instead of conventional fuels.

61. Recycle condensate.
Recover flash steam from higher pressure condensate.
Pass steam through back pressure steam turbine rather than through pressure reducing station for low pressure steam.
Attend steam leakages and repair damaged insulation.
Examine possibility of installation of cogeneration systems (combined electricity and steam generation) / trigeneration system (combined electricity, steam & refrigeration generation)

62. 2. PUMPS Select the right pump to match head and flow requirements.
Make maximum use of gravity flow. Avoid intermediate storages to avoid pumping. For circulation system use siphon effect; avoid free fall (gravity) return.
Avoid throttling / bypass; to control flow, prefer speed controls or sequenced operation of pumps.
In pumping to systems having a number of non-continuous users, auto ON-OFF valves / control valves need to be provided on users and VFD on pumps.

63. Segregate high head and low head loads and install separate pumps.
Operate booster pumps for small loads requiring higher heads, in place of operating complete system at higher head.
Operator cooling/chilling system with higher fluid differential temperature to decrease flow and hence save pumping energy.
Replace old pumps by high efficiency pumps.

64. Trim impellers wherever pumps are over designed.
Valve throttling indicates pump over design; replace pump with correct size pump or install lower size impeller
Coat hydraulic passages of pumps with resins having better surface finish to reduce internal friction and increase efficiency.
Minimize pressure drop in piping by rerouting of pipeline, removing valves, which never need to be operated, and resizing of pipeline.

65. 3. COOLING TOWERS
Control CT fans based on cold well temperature; use two speed or VFD if fans are few and on-off stage control if cells are many.
Select CT with low pressure drop, high efficiency PVC cellular fills in place of splash bars.
Periodically clean, water distribution nozzles. Ensure that no channeling of water flow is taking place. Uniform flow distribution will improve performance of cooling tower.
Optimize cooling water chemical treatment.
Replace aluminum fans by aerodynamic FRP fans.

66. 4. REFRIGERATION SYSTEMS
Challenge the need of refrigeration system, particularly, for old batch processes. Optimise the temperature requirement.
Examine the possibility of vapour absorption system operating with waste heat streams in place of vapour compression systems.
Check regularly for correct refrigerant charge levels.

67. Check for damaged insulation / sweating.
Select multistage compressors with inter cooling for low temperature applications.
Operate chillers with lowest possible condensing temperature and highest possible chiller (evaporator) temperature.
Carryout regular cleaning of condenser to ensure proper heat transfer.

68. 5. LIGHTING
Select high efficiency lighting luminaries having highest lumens / watt output. eg. Compact fluorescent lamp (CFL), low pressure sodium vapour lamp.
Provide lighting transformer to reduce the voltage of lighting loads.
Make use of task lighting.
Make most use of day lighting by providing skylight.

69. Paint walls and ceiling with light colors.
Lower height of light fixtures.
Control lighting with clock timers, occupancy sensors, photocells and master switch.
Select ballast with high efficiency and high power factors.
Use LED lamps for indicating purpose.

70. 6. FANS & BLOWERS
Select fans with aerofoil fan blades; replace old inefficient fans by modern high efficincy fans / blowers.
Ensure that design of fans / blowers are matching with operating conditions if not replace with correct size fan / blower.
Replace throttle / bypass control by speed control.

71. Minimize speed to minimum possible.
Reduce pressure drops in system by proper design / sizing of ducting. Minimize bends in ductings.
Eliminate leakages.
Clean screen, filters, fan blades regularly.
Avoid idle running of fans by interlocking with main equipments.

72. 7. MOTORS Properly size the motor for the optimum efficiency.
Use energy efficient motors for continuous operating loads.
Balance three phase loads. An imbalanced voltage can reduce efficiency of motor by 3-5%.
Connect motors remaining under loaded (< 40%) continuously, in star.

73. Rewound motors should be checked for efficiency.
Provide capacitor banks at MMC to correct PF.
Use soft starters / VFD instead of fluid coupling for loads having high starting torque or loads prone to jamming.

74. 12. Energy Efficiency Improvement and Cost Saving Opportunities in Petrochemical Industry

75. The U.S. Petrochemical Industry
The North American Industry Classification (NAICS) distinguishes seven 4-digit sub-sectors of the chemical industry:
3251 Basic chemical manufacturing
3252 Resin, synthetic rubber, and artificial synthetic fibers and
filaments manufacturing
3253 Pesticide, fertilizer and other agricultural chemical
manufacturing
3254 Pharmaceutical and medicine manufacturing
3255 Paint, coating, and adhesive manufacturing
3256 Soap, cleaning compound, and toilet preparation
3259 Other chemical product and preparation manufacturing

76. Supporting Equipment and Infrastructure
Emission abatement equipment.
Product storage and handling equipment
Boilers, Combined Heat and Power (CHP) plants and other parts of the steam infrastructure including pipes and valves.
Furnaces and process heaters.
Pumps, compressors, vacuum, pressure relief equipment and fans.
Heat exchangers, cooling and refrigeration.

77. Energy use in the chemical industry by fuels and feedstock category, 2002

78. Energy use by sub-sector, 2002

79. End use of electricity in the total chemical industry and the sub-sectors studied, 2002

80. Estimated final energy consumption for selected key chemicals

81. Main elements of a strategic energy management program

82. Simplified schematic of a steam production and distribution system

83. Summary of energy efficiency measures in boilers (Steam Supply)

84. Steam Supply - Combined Heat and Power
Steam injected gas turbines
High-temperature CHP
Steam expansion turbines

85. Summary of energy efficiency measures in steam distribution systems

86. Furnaces and Process Heaters
Heat Generation
Control the air-fuel ratio
Excess air should be limited to 2-3% oxygen

87. Heat transfer and heat containment in heaters
Use of soot blowers, burning off carbon and other deposits from radiant tubes and cleaning the heat exchange surfaces. Typical savings are 5-10%.
Ceramic coated furnace tubes can improve heat transfer
Reducing wall heat losses (typical savings 2-5%), furnace pressure control (5-10%), maintenance of door and tube seals (up to 5%), reducing cooling of internal parts (up to 5%) and reducing radiation heat losses (up to 5%).

88. Flue gas heat recovery
Others – controls, maintenance and electric heaters

89. Electric Motors Motor Management Plan
Creation of a motor survey and tracking program.
Development of guidelines for proactive repair/replace decisions.
Preparation for motor failure by creating a spares inventory.
Development of a purchasing specification.
Development of a repair specification.
Development and implementation of a predictive and preventive maintenance program.

90. Strategic motor selection
Maintenance
Properly sized motors
Adjustable speed drives
Power factor correction
Minimizing voltage unbalances

91. Pumps Operations and maintenance Monitoring Reduce need
More efficient pumps
Correct sizing of pump(s) (matching pump to intended duty)
Use multiple pumps
Trimming impeller (or shaving sheaves)
Controls

92. Adjustable speed drives (ASDs)
Avoid throttling valves
Correct sizing of pipes
Replace belt drives
Precision castings, surface coatings or polishing
Sealings
Curtailing leakage through clearance reduction
Dry vacuum pumps

93. Fans and Blowers Fan oversizing
Adjustable speed drives (ASDs) and improved controls
High efficiency belts (cog belts)

94. Compressors and Compressed Air Systems
Compressed air – maintenance
Monitoring
Reduce leaks (in pipes and equipment)
Reducing the inlet air temperature
Maximize allowable pressure dew point at air intake
Optimize the compressor to match load
Controls
Properly sized regulators
Sizing pipe diameter correctly
Heat recovery for water or space heating preheating
Adjustable speed drives (ASDs)
High efficiency motors

95. Distillation Enhanced distillation controls
Optimization of reflux ratios
Check product purity
Seasonal operating pressure adjustments
Column insulation
Reducing reboiler duty
Feed conditioning
Upgrading column internals
Stripper optimization

96. Buildings: HVAC and Lighting Energy Efficiency Measures for HVAC Systems
Energy efficient system design
Recommissioning
Energy monitoring and control systems
Non-production hours set-back temperatures
Duct leakage repair
Variable-air-volume systems
Adjustable-speed drives (ASDs)
Heat recovery systems
Fan modification
Efficient exhaust fans
Use of ventilation fans
Cooling water recovery
Solar air heating
Building reflection
Building insulation
Low emittance (Low-E) windows

97. Energy Efficiency Measures for Lighting
Turning off lights in unoccupied areas
Lighting controls
Exit signs
Electronic ballasts
Replacement of T-12 tubes with T-8 tubes
Replacement of mercury lights
High-intensity discharge (HID) voltage reduction
High-intensity fluorescent light
Daylighting

98. CONCLUSIONS
A key first step in any energy improvement initiative is to establish a focused and strategic energy management program, which will help to identify and implement energy efficiency measures and practices across and organization and ensure continuous improvement.
 While the expected savings associated with some of the individual measures may be relatively small, the cumulative effect of these measures across an entire plant may potentially be quite large.
The degree of implementation of these measures will vary by plant and end use; continuous evaluation of these measures will help to identify further cost savings in ongoing energy management programs.

99. ACKNOWLEDGEMENT
Octave Levenspiel, Chemical Reaction Engineering, Wiley Eastern Limited.
McCabe, W.L. and Smith, J.C., Unit Operation of Chemical Engineering, McGraw Hill, New York.
Internet sources

100. THANK YOU