Introduction

 

The flue gas treatment plant described in this case study is realized for a new Latvian company, specialized in lead recovery from exhausted lead-acid batteries.  TVT Termoventiltecnica was engaged by the customer during the construction of the factory. Therefore TVT has studied the process and, together with the client, developed a system for flue gas treatment for all production phases, including the melting zone for lead material laden with sulfuric acid in a rotary furnace, the refinery zone for refining and skimming the molten metal, and the slag warehouse area for handling the slag.

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Problem

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The requirements of the customer of regarding the flue gas treatment plant :

• Efficient suction from emission sources to prevent dust dispersion in the workplace environment.

• Dust emission below 1 mg/Nm3.

• SOx neutralization up to legal limits.

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The peculiarities and challenges of the process included:

• Suction from various process points with significantly different temperatures and flue gas characteristics.

• Regulation of flow rate and temperature.

• High toxicity of lead dust.

• Client's request for dust emissions reduction below 1 mg/Nm3.

• Presence of high loads of sulfur oxides in the gas requires the regulation of the correct gas temperature to prevent condensation and consequent corrosion.

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Solution

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To meet the customer requirements, TVT realized and supplied a turnkey flue gas treatment plant, which includes following phases: adeguate suction, gas mixing and temperature regulation, basic reagent dosing and injection (lime) for first-stage SOx neutralization, bag filter for final dust collection, and basic scrubber for final SOx neutralization.

The gas sucked from 14 points is conveyed into a calm chamber for the purpose of temperature regulation and coarse dust collection. In the subsequent pipe segments the gas undergoes two type of treatment:

• Temperature regulation;

• Addition of the reagent (powder lime) aimed at preliminary SOx neutralization.

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Afterwards the fumes are conveyed to the bag filter for dust separation, being then evacuated from hoppers through discharge valves and a chain conveyor (reddler) to convey the dust to a single discharge point.

 

The gases are then directed to the second stage for final SOx treatment in counter-current washing tower with a static bed, equipped automatic NaOH dosing system for washing liquid pH adjustment.

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The plant is equipped with a continuous dust emission control system.

 

Garanteed dust emissions below 1 mg/Nm3