Page 181 - CW E-Magazine (3-9-2024)

Special Report Special Report

Managing air emissions profi tably  High thermal durability; usually involves a single solvent, usu- Concentration: 6,000-ppm by volume
ally ethyl acetate. This would be suit-
Recovery: 364-tonnes/year.
Superior mechanical properties; and

 High conversion effi ciencies. able for recovery and reuse of solvent Includes fuel used for steam, power,
ir emission control need not al- tor unit inlet capacity may range from D.M. MOHUNTA by absorption technology. It also eco- and natural gas for heating.
ways be a cost it can at many 5,000-Nm /hr to 130,000-Nm /hr. Commercial Chemical and Develop- Odour removal friendly as it has lower CO footprint Absorption technology using Geno-
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Atimes be profi table. Large num- ment Company Due to the very low VOC concentra- than oxidation technology. sorb: 271.
ber of volatile organic and other com- Recovery Chennai tion, a catalytic oxidizer is the most suit- Thermal oxidation with recuperation:
pounds like nitrogen oxides) (NO ), A large range of VOCs can be re- Email: dmm@ccdcindia.com able approach for waste odorous organic Case Study: Carbon dioxide foot- 1,161-tonnes CO /year.
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x
sulphur dioxide (SO ), hydrogen sul- covered from process and tank vents www.ccdcindia.com streams compared to other technologies. print of ethyl acetate recovery (only Global warming potential (GWP)
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phide (H S), carbon monoxide (CO), using absorption technology because of Catalytic oxidizers are capable of conti- for process) for ethyl acetate: 3.2-4.0 per kg.
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and ammonia (NH ), are emitted into the fairly high concentration. We have suc- lytic oxidiser. The preferred process is nuous steady state operating conditions Solvent: ethyl acetate Recovery of 364 tonnes would
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atmosphere by chemical processes and cessfully used Genosorb, a high boiling catalytic oxidation to water, nitrogen for nearly indefi nite periods and accom- Table 1: Comparison of absorption system (Genosorb) for ethyl acetate (EA)
other processes like substrate coating, absorption media supplied by Clariant. and CO . It operates at lower tempera- plish VOC destruction at relatively low recovery
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combustion of fuels and wastes. The CO footprint is lower than in the ture and gives better thermal economy temperatures. With few moving parts
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case of incineration. than high temperature oxidizer process. and constant stable operating pressures Parameter Units Without Rotary With Rotary
Environmental norms require a In practice, the equipment is quite and temperatures, a properly designed concentrator Concentrator
maximum level of emission reduction; Incineration or destruction/decom- compact with minimum ducting oxidizer can easily achieve more than Air fl ow rate m /hr 20,000 20,000
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therefore these must be either recovered position (see Figure 1). 99% destruction effi ciency. Lower ope- EA quantity kg/hr 42 42
or destroyed to environmentally non- This can be applied to VOCs as well rating temperatures in conjunction with EA in air mg/m 2,100 2,100
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hazardous or less harmful products. as to gas species like nitrogen dioxide Selection of suitable catalyst from heat recovery can give lower operating
(NO , nitric oxide (NO), nitrous oxide the wide range of catalysts available expenses. Steam kg/hr 1,250 180
2)
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A further and increasingly important (N O), NH , and CO that may emanate from Clariant-Sudchemie, for a given Cooling water m /hr 200 35
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consideration in the choice of process from chemical processes or combustion application is key to overall perfor- Printing Refrigeration TR 200 60
for emission control, is generation of equipment like boilers. Incineration is mance/destruction effi ciency. Printing of fl exible packaging uses Power (connected load) KWH 48 50
global warming gases like CO , etc. suitable for vapours from high boiling inks with multiple solvents like ketones
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products like tar, phenolic bodies, resins, Advantages of catalytic emission (e.g., acetone, methyl ethyl ketone, Fuel LPG or natural gas KW 0 110
Recovery or incineration etc. and also other organic odours. control are: methyl isobutyl ketone, etc.), esters Genosorb loss gm/hr 112.1 50
Under certain conditions it would be  Low operating temperature; (e.g., methyl acetate, ethyl acetate, Base price (India) Rs. lakhs 350 300
economical to recover and recycle the The incineration may be done in a  Wide range of operating tempera- n-propyl acetate, n-butyl acetate, isobutyl

volatile organic compounds (VOCs). high temperature oxidiser or in a cata- tures; acetate, etc.), alcohols (e.g., methanol,
When the VOC concentration is high but ethanol, n-propanol, isopropanol, buta-
requires abnormally low temperatures in nol, etc.), mineral turpentine, etc. High
the condenser to achieve the emission volumes of hot air are used to dry and set
target, Genosorb absorption technology the ink. The hot air emanating from the
can be used for economic recovery. In machine have low level concentrations
other cases, where the VOC concentra- of the solvents – typically a few hundred
tion is low, the operating costs of such parts per million (ppm) – and is a cause
recovery are very high (see example be- of odour and pollution.
low). However, in such instances, it may
be possible to increase concentration, by A recovery system would give a
using a specially designed rotary con- mixture that is diffi cult to separate and
centrator, to level where it is economical therefore has only calorifi c value. A
to recover or process. Where the concen- catalytic oxidation system with rotary
trations are of the order of 50-100 ppm, concentrator to bring the concentration
the concentration can be increased 20-30 up to 25% of Lower Explosive Limit
times. Thus, a volume of 50,000-m /hr is (LEL) will reduce the volume by 10-30
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reduced to 2,500-m /hr while still keep- times and would be an economic
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ing the concentration well below the solution.
lower explosive limit. There will be very
large reduction in capex as well opex Fig. 1: Schematic of catalytic oxidation process Laminating and coating Fig. 2: Schematic of solvent recovery system
for recovery or incineration. A concentra- Adapted from Siebu-Giken Co. Ltd. The laminating of fl exible package Adapted from Siebu-Giken Co. Ltd.

180 Chemical Weekly September 3, 2024 Chemical Weekly September 3, 2024 181

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