Page 178 - CW E-Magazine (23-4-2024)

Special Report Special Report

variable capacity control requirement, heat recovery is installation of additional leakage from such seal, the material is EMS-27: While looking for chang- EMS-31: In many reactions, oxygen tom of any plant contains valuable
can bring signifi cant energy saving. bank of economiser to add surface either contaminated, vented or fl ared. ing from high pressure steam to low is one of the reactants. Reaction is material, which cannot be recovered
area for more heat recovery from fl ue However, due to presence of gas at seal- pressure steam as energy source, it is normally at high pressure and tempera- by simple distillation operation. There
EMS-18: Steam tracing is provided gas and heat water/process stream. ing surface in many cases, when seal is observed that the requirement is mar- ture. As a source of oxygen, atmospheric are many other unit operations, as well
in petrochemical plants and refi ne- Normally, space available in econo- once found leaking due to any abnor- ginally for higher pressure than avail- air is used. When process is at high as unit processes, by which lighter
ries. Due to poor workmanship, use of miser section is not enough and struc- mal operation, it is diffi cult to get it able low level steam or operating mar- pressure, power consumption in such material from slop can be recovered as
many fi ttings, as well as aging, many tural integrity does not allow to add reset due to the presence of gas and this gin is reduced leading to probability of air compressor is very high. In order liquid/gas fuel or valuable chemicals.
leakages develop, leading to loss of one bank. It was be possible to insert leads to losses and unsafe conditions. upset. In such cases, thermo-compres- to reduce compression power, as well Detailed study is worthwhile for value
energy. Frequent repair is required to one tube bank in available blank slot Use of pressurised double mechanical sor is one of the solutions to increase as to enhance capacity of oxygen sup- addition and energy recovery.
maintain leak-proof system. Multiple between tubes and horizontal part seals for liquefi ed gas with compati- steam pressure and reduce high pres- ply, oxygen enrichment of air is accept-
traps are provided for steam tracing. of stack, especially in heat recovery ble sealing fl uid is a good practice to sure steam usage. able practice to reduce specifi c volume EMS-35: Industrial cooling tower
Many times, trap malfunction leads to steam generator (HRSG). Check in minimise leakage of hydrocarbons in and thereby, power reduction and to is evaporative cooling. Cooling water is
ineffective tracing or passing of steam. your case too. atmosphere and fl are, thereby reducing EMS-28: One of the reasons for enhance capacity. Caution: Metallurgy pumped to plant and various exchangers
Now electrical tracings are available energy loss and improving reliability. continuous fl are is passing of minor of equipment, as well as fl ammability to cool process stream. Many times, it
for hazardous areas also. It may be eco- EMS-22: Air compressors take air quantity of hydrocarbon from mul- of mixed reactant, limits extent of is used to cool circulating contaminated
nomical to convert from steam tracing from atmosphere. Temperature and rela- EMS-25: Many sites have continu- tiple Class 2 type valves in old design. oxygen enrichment. water or effl uent water stream. For
to electrical heat tracing or use electri- tive humidity (RH) of air varies, lead- ous fl aring of hydrocarbons. Even after By changing normally closed control such service, direct contact evapora-
cal heat tracing from project stage for ing to variation in load and sometimes detailed analysis as well as profi ling valve and manual valve for pressure EMS-32: Convection bank of tive cooler for contaminated or effl uent
better temperature control and low life become a bottleneck. Although suction of composition, source could not be control and by letting down to fl are furnace getting fouled due to deposits water stream is a good energy saving
cycle cost. It is worth checking local fi lters are provided, there can be fi ne identifi ed. It may be due to small pass- header by tight shut off valves will of soot, refractory or dust results in low solution. It may reduce capex also as
conditions of cost of steam and electri- dirt particles passing through fi lters, ing of many valves and blowdown reduce signifi cant hydrocarbon leak- energy recovery and increase of stack such evaporative cooling can be modu-
city, maintenance costs, costs of losses which can deposit and foul impellers required for pressure control, resulting age to fl are. temperature. Most convection bank lar and avoid expensive exchanger and
vs. capital investment. of air compressor, reducing effi ciency in continuous fl are. Due to the presence tubes are fi nned tubes and it is observed pipeline.
of the compressor; this may require fre- of large quantity of nitrogen as purge EMS-29: Air compressor impellers that particulate matter deposits in fi ns
EMS-19: Most control room and quent water-wash, as well as increase gas, the recovery is not considered. It get fouled due to fi ne dust deposits. It cannot be cleaned easily. Chemical EMS-36: Mixture of chemicals is
building ACs are compression refri- in frequency of periodic maintenance. is possible to recover such continuous is observed that this reduces effi ciency cleaning of convection bank from outer separated in a series of columns. For
geration. However, after commissioning Installation of combined fi lter, washer fl aring of gas and use as a fuel gas. In signifi cantly. Dust can deposit in inter- surface is done, but water and chemi- each column, there is refl ux condenser
of process plant, it is normally observed and chiller in suction of air compressor case of nitrogen, the recovered fl are gas and after-coolers, which further reduces cal may damage refractory of furnace and re-boiler. Heat is supplied in
that in many locations, low level energy will reduce specifi c volume of air and poses combustion issue. Minimise it by capacity and effi ciency. This can be or boiler. To avoid such damage, dry re-boiler and removed in refl ux con-
is either vented to atmosphere in form dirt load for effi cient, consistent and use of orifi ce or replace purge nitrogen due to passing or malfunction of suc- ice blast cleaning of convection bank denser. Many times, the columns are
of steam/water vapour, or cooled by reliable operation, ultimately leading to by methane, which will be recovered as tion fi lters or very dusty atmosphere was tried and found successful. Blast combined and intermediate product
cooling water/air. This is loss of energy. signifi cant energy conservation. fuel gas. or construction nearby. In order to gun can go inside small space between is removed as side stream and then
Present costs of Vapour Absorption regain effi ciency, online periodic water tubes and can clean solid deposits fi nished in fi nishing column. In order to
Machine (VAM) can justify their use EMS-23: In many distillation col- EMS-26: There are certain design spray cleaning of impellers is a nor- effectively. reduce signifi cant energy consumption
for chilled water generation for an AC umns and vessels, pressure control is margins while designing every equip- mally accepted practice and found very as well as reduce MPI, use of divided
load, especially if heat is from waste split range type. In case of low pressure, ment and when an equipment is lined effective. Caution: Type and location of EMS-33: Off-gas from many pro- wall column is one of the proven techno-
heat and do not have high cost tag. This supply the inert gas and when pressure up in process, requirement of utility spray nozzle is very important to avoid cesses is used as fuel gas, which con- logies and can be used in place of multiple
will save electricity and recover waste increases, vent gases to fl are header or condition will be different than design. imbalance and malfunction during tains hydrogen. This hydrogen has very columns, re-boilers and condensers.
heat. atmosphere (storage tank provision of Design operating parameters are main- online water spray cleaning. high calorifi c value per kg, but low
additional cooler/chiller on such vent tained by control system, which may calorifi c value per cu.m., as compared EMS-37: Any catalyst requires
EMS-20: When furnace or boiler stream can condense material for its not be energy-effi cient. For example, EMS-30: Process compressors to natural gas. When gas is transported activation energy. Therefore, feed is
is operating at high stack temperature recovery from which at least fuel value lower chest pressure of re-boiler, ope- handling mixed gases and unsaturated from one location to other, it restricts preheated even if the reaction is exo-
and there is no feasibility of recovery of can be recovered). ration of distillation column at lower gases are prone for polymerisation and the fl ow due to high pressure drop, thermic. Although energy integration
heat in economiser, it is good practice pressure, low refl ux temperature, and fouling of impellers as well as after-/ especially, when hydrogen is higher in catalytic reaction is done by utilising
to install air preheater or fuel preheater EMS-24: Pumping of pressurised low product temperature. It is possible inter-coolers. This reduces effi ciency than design. Recovery of hydrogen waste heat, product heat, etc., energy
for furnace, utilising fl ue gas to recover liquefi ed gas, where vapour pressure is to replace high pressure steam/high and capacity considerably. Effi ciency from off gas/fuel gas will be energy consumption is large and sometimes
waste heat signifi cantly. It will require more than atmospheric pressure is nor- temperature energy by low pressure/ is regained by online periodic fl ushing effi cient solution, especially, where require very high level energy. It is
Induced Draft (ID) fan and draft control mal practice in industry. Many types low temperature steam at many pro- by high aromatic stabilised oil or use of required hydrogen for process is gene- observed that due to technological advan-
system, as well as Interchanger. of mechanical seals are tried based on cesses, taking advantage of design chemical dispersant to clean impellers. rated by electrolysis process. tage and research, catalysts requiring
characteristic of fl uid, toxicity of fl uid margin and design dirt factor, which In many applications, continuous oil lower activation energy are available for
EMS-21: One more option of stack and compatibility of fl uid. In case of results in to signifi cant energy conservation. spray is also used to avoid fouling. EMS-34: Slop generated as a bot- many applications. During evaluation,

178 Chemical Weekly April 23, 2024 Chemical Weekly April 23, 2024 179

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