Dissolved Oxygen+Residual Hydrazine

Dear Sir,

I am the chemical controller of a large Petrochemical company in India. I am facing a unique problem in Boiler water treatment. I seek your advice to troubleshoot.

We have 40 Ton/Hr steam system operating at 45 bar. We dose Hydrazine as the only oxygen scavenger to the water coming from deaerator , where dissolved oxygen is removed with steam. We dose morpholine also as a neutralizing amine along with hydrazine.

Recently, we have adopted to dose just the required hydrazine . We have reduced the quantity of hydrazine so that the residual hydrazine is barely 0.5 mg/lit.

The trouble is this water also shows the presence of Dissolved Oxygen to the extent of 0.4 mg/ lit.

1. Will you please brief me the rare (?) phenomenon of coexistence of Oxygen and residual Hydrazine?

2.Can I overlook the presence of Dissolved Oxygen since residual hydrazine is present ?

3. Should I increase the dosing quantity of hydrazine till dissolved oxygen is non-deductible ?

I will be happy to receive your expert reply at the earliest.

Regards,

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