Page 194 - CW E-Magazine (15-7-2025)

Special Report

Reducing solvent incineration emissions in API

manufacturing: Operational best practices

ABSTRACT residuals with APIs or unreacted re- ASIYA MUHAMMED KOCHUVEETTIL
olvent waste generated from agents (ICH, 2019). These wastes are McClelland Engineers Pvt. Ltd.
Active Pharmaceutical Ingredient diffi cult to treat biologically because E-mail: asiya@mcclellandindia.com
S(API) manufacturing presents of their toxicity, high COD, and non-
a growing environmental and compli- biodegradable characteristics. environment and helps recover valu-
ance challenge. Much of this waste is able resources.
incinerated, and the associated emis- In most instances, high-temperature
sions, energy ineffi ciencies, and regula- incineration is the sole regulatory-per- Halogenated solvents release
tory risks demand technical attention. missible and environmentally accept- hydrogen chloride (HCl), hydrogen fl uo-
This article outlines practical engineer- able disposal option, especially in the ride (HF), and other acid gases upon
ing strategies to reduce emissions from case of halogenated or multi-phase combustion. These gases can corrode
solvent incineration, focusing on com- solvent streams. stack components and lead to non-
bustion control, acid gas scrubbing, compliance with emissions regulations.
energy recovery, and material integrity. Combustion control: Enhancing A robust Air Pollution Control Device
destruction effi ciency (APCD) system generally consists of a
Introduction: The solvent waste Proper combustion is the corner- quench tower for cooling hot fl ue gas,
burden stone of clean incineration. The perfor- a packed bed scrubber with caustic
India’s API sector contributes signi- mance of an incineration system begins solution for neutralization, and a mist
fi cantly to global pharmaceutical at the combustion chamber. Optimised eliminator to eliminate fi ne droplets.
supply but also generates large quantity chamber design is necessary to achieve (UNEP, 2013).
of hazardous solvent waste. Most often, a Destruction and Removal Effi ciency
more than 35% of such waste is incine- (DRE) of more than 99.9% in solvent Advanced systems have continuous
rated – a process, when poorly engi- waste incineration. Dual-chamber sys- pH monitoring and optimised liquid-
neered, leads to higher levels of carbon tems allow for staged combustion and gas ratios. In some applications, re-
emissions, energy loss, and environ- improved thermal stability. For these covered aqueous HCl can be reused or
mental non-compliance. With Central to be attained, certain critical operating sold, providing added value to waste
Pollution Control Board (CPCB) stan- conditions need to be sustained: com- treatment.
dards becoming stricter and Environ- bustion temperatures above 1,100°C;
mental, Social and Governance (ESG) residence times of at least two seconds; Energy recovery: Converting
expectations on the rise, manufacturers and adequate turbulent mixing to bring emissions into effi ciency
have to implement best-in-class incine- about complete oxidation. Solvent incineration doesn’t have to
ration technologies for ensuring regu- be a net energy loss. High calorifi c sol-
latory compliance as well as sustain- Low-NOx burners and oxygen trim vent streams can sustain heat recovery
able operations. (CPCB, 2020). systems ensure optimal combustion systems, e.g., waste heat boilers or heat
conditions while reducing the forma- exchangers, located following the com-
Typical API solvent waste composi- tion of secondary pollutants. Program- bustion zone. Recovered steam from
tion mable logic controllers (PLCs) allow such systems can be employed to sus-
API manufacturing generates sol- for accurate burner modulation and tain boiler feedwater preheat, process
vent-rich residues from reaction, ex- safety interlocks, which avoid under- heating, or HVAC applications in the
traction, and purifi cation processes. burning and provide complete thermal facility.
These typically contain chlorinated sol- destruction of volatile organics.
vents like dichloromethane and chloro- In optimally designed systems, 10-
form; aromatic hydrocarbons such Acid gas management: Scrubbing 20% fossil fuel savings are possible
as toluene and benzene derivatives; and HCl recovery (US EPA, 2015). Flue gas quality has to
oxygenated solvents such as acetone Effi cient scrubbing avoids the be monitored with care so as not to foul
and methyl ethyl ketone; and mixed release of harmful acid gases into the and corrode recovery equipment.

194 Chemical Weekly July 15, 2025

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