THERMORIGENERATIVE THERMORIGENERATIVE COMBUSTOR FOR COMBUSTOR FOR

CHLORINATED OFF-GASCHLORINATED OFF-GAS

A SPECIFIC DESIGN FOR THE A SPECIFIC DESIGN FOR THE CHEMICAL-PHARMACEUTICAL CHEMICAL-PHARMACEUTICAL

INDUSTRYINDUSTRY

C+A

WHY AN AD HOC COMBUSTOR WHY AN AD HOC COMBUSTOR FOR CHLORINATED OFF-GAS?FOR CHLORINATED OFF-GAS?

1.1. The resort to organo-chlorinated solvents in The resort to organo-chlorinated solvents in the synthesis of pharmaceutical intermediate the synthesis of pharmaceutical intermediate products, sometimes only during well defined products, sometimes only during well defined campaigns, comes from the high campaigns, comes from the high characteristics of these compounds, which are characteristics of these compounds, which are often unreplaceable. often unreplaceable.

2.2. Under combustion chlorinated compounds Under combustion chlorinated compounds produce HCl (hydrochloric acid). In some produce HCl (hydrochloric acid). In some cases HCl is present in the off-gas input as cases HCl is present in the off-gas input as well.well.

WHY AN AD HOC COMBUSTOR WHY AN AD HOC COMBUSTOR FOR CHLORINATED OFF-GAS?FOR CHLORINATED OFF-GAS?

3.3. The thermorigenerative combustor type is the highest The thermorigenerative combustor type is the highest efficiency combustor: it has the lowest support fuel efficiency combustor: it has the lowest support fuel consumption and consumption and exit temperatures of 60 exit temperatures of 60 ÷ 150°C÷ 150°C. It is . It is of simple construction but materials generally adopted of simple construction but materials generally adopted result to be unfit for chlorinated off-gas.result to be unfit for chlorinated off-gas.

4.4. In the combustor flue gases HCl has a dew point of ab. In the combustor flue gases HCl has a dew point of ab. 200°C200°C. Below this temperature HCl condensation (very . Below this temperature HCl condensation (very corrosive) finds place. For T < 100°C condensation of corrosive) finds place. For T < 100°C condensation of water vapour produced by combustion brings in dilution water vapour produced by combustion brings in dilution of HCl condense, so decreasing the overall of HCl condense, so decreasing the overall corrosiveness, which nonetheless remains high.corrosiveness, which nonetheless remains high.

REFERENCE DESIGN REFERENCE DESIGN PARAMETERSPARAMETERS

Data apply to off-gas Data apply to off-gas thermorigenerative thermorigenerative combustors in the combustors in the Lombardia Region - Lombardia Region - Italy (D.g.r. 1.08.2003 Italy (D.g.r. 1.08.2003 n. 7/12943 – Utilzation n. 7/12943 – Utilzation of best available of best available technologies PC.T.02). technologies PC.T.02).

The following main The following main parameters apply:parameters apply:

Organic chlorine in the

VOC

[% p.]

Combustion chamber

temperature

[°C]

Combustion chamber residence

time[sec]

Absent ≥ 750 ≥ 0,6≤ 0,5 ≥ 850 ≥ 1,0> 0,5 e ≤ 2,0

≥ 950 ≥ 2,0

> 2,0 ≥ 1100 ≥ 2,0

POSSIBLE TECHNICAL SOLUTIONSPOSSIBLE TECHNICAL SOLUTIONS

After a careful study and examination of what has been After a careful study and examination of what has been been done in this field in Italy and Europe up till now, been done in this field in Italy and Europe up till now, the technical solutions appear to be:the technical solutions appear to be:

SOLUTION A (high energy consumption)SOLUTION A (high energy consumption)

Enhancing the chlorinated off-gas inlet temperature Enhancing the chlorinated off-gas inlet temperature to T to T ≥≥ 200°C 200°C by a heat exchanger - 270°C overheated by a heat exchanger - 270°C overheated steam / off-gas or double heat exchanger - 200°C steam / off-gas or double heat exchanger - 200°C steam/ off-gas and NG flue gases / off-gas), with steam/ off-gas and NG flue gases / off-gas), with relating high costs of heat exchangers (graphite) and of relating high costs of heat exchangers (graphite) and of utilities.utilities.

POSSIBLE TECHNICAL SOLUTIONSPOSSIBLE TECHNICAL SOLUTIONS

SOLUTION B (with minimized energy consumption)SOLUTION B (with minimized energy consumption)

Feeding the off-gas (chlorinated and non) directly to Feeding the off-gas (chlorinated and non) directly to combustor, combustor, with no preheatwith no preheat, under the same conditions , under the same conditions of off-gas release from production, or after scrubbers of off-gas release from production, or after scrubbers that may be introduced to reduce high concentration that may be introduced to reduce high concentration peaks of chlorinated compounds (alkaline scrubbing).peaks of chlorinated compounds (alkaline scrubbing).

Feeding auxiliary fuel (natural gas) for combustion Feeding auxiliary fuel (natural gas) for combustion chamber temperature control, chamber temperature control, leaving the combustor leaving the combustor flue gas temperature uncontrolled:flue gas temperature uncontrolled: this shall then this shall then depend upon off-gas input flow (turn-down) and organic depend upon off-gas input flow (turn-down) and organic concentration / enthalpy of combustion.concentration / enthalpy of combustion.

BASE POINTS OF C+A PROJECTBASE POINTS OF C+A PROJECTSOLUTION A

Plant capacity 10.000 Nm3/h

SOLUTION B(C+A)

Plant capacity 10.000 Nm3/h

Steam consumption (15 bar g - 200°C) for off-gas preheat

686 Kg/h 0 Kg/h

Natural gas consumption(34,953 KJ/Nm3) for off-gas preheat

32 Nm3/h 0 Nm3/h

Yearly cost (5,000 hrs/year) of steam and natural gas for off-gas preheat

131,000 Euro/year

0 Euro/year

COMPARISON OF UTILITIES CONSUMPTION AND RELATING COSTS FOR SOLUTIONS A AND B – 10,000 NM3/H OFF-GAS PLANT

BASE POINTS OF C+A PROJECTBASE POINTS OF C+A PROJECT

Steam ejector

Concentr. off-gasDiluted off-gas

3 tower combustorHot gas by-pass

Flue gas duct

Scrubber-quencher

Final chimneyFlue gas fan

Natural gas

NaOH 30% Salty drain

OVERALL OFF-GAS INPUT FLOW: 5,000 ÷ 70,000 NM3/H

BASE POINTS OF C+A PROJECTBASE POINTS OF C+A PROJECT

Plant guaranteed emission concentrations:Plant guaranteed emission concentrations:

COMBUSTOR[mg/Nm3]

SCRUBBER[mg/Nm3]

TOCCONOxHCl

< 20 < 100 < 100

< 10

Values refer to measured oxygen level (= O2 as such)