Method for firing a rotary kiln with pulverized solid fuel

Claim 1

A method for firing a coal burner for a kiln comprising the steps of: providing pulverized coal at a predetermined rate which corresponds to the desired rate with which pulverized coal is combusted in the kiln; pneumatically transporting the pulverized coal to the burner with an amount of primary combustion air of at most about 5% of the theoretical amount of air needed to combust the pulverized coal; forming a supplemental primary combustion airflow measured so that the primary combustion airflow and the supplemental primary combustion airflow comprise at most about 20% of the theoretical amount of air needed to combust the pulverized coal; heating the supplemental primary air to a temperature of at least about 600° F.; combining the primary combustion airflow and the pulverized coal entrained therein with the supplemental primary combustion airflow to form a coal-airstream at the burner; flowing the coal-airstream over a sufficient distance so that volatiles in the pulverized coal in the stream are driven off; thereafter igniting the coal-airstream to form a flame directed into the kiln; generating a secondary combustion airstream for providing the balance of combustion air required for fully combusting the pulverized coal in the stream; heating the secondary combustion air with product discharged from the kiln to a temperature of at least about 800° F.; and mixing the secondary combustion air with pulverized coal discharged into the kiln to effect the full combustion of the pulverized coal.

Claim 2

A method for firing a coal burner for a kiln comprising the steps of: providing pulverized coal at a predetermined rate which corresponds to the desired rate with which pulverized coal is combusted in the kiln; pneumatically transporting the pulverized coal to the burner with an amount of primary combustion air of at most about 5% of the theoretical amount of air needed to combust the pulverized coal; forming a supplemental primary combustion airflow measured so that the primary combustion airflow and the supplemental primary combustion airflow comprise at most about 20% of the theoretical amount of air needed to combust the pulverized coal; heating the supplemental primary air to a temperature of at least about 600° F.; combining the primary combustion airflow and the pulverized coal entrained therein with the supplemental primary combustion airflow to form a coal-airstream at the burner; flowing the coal-airstream over a sufficient distance so that volatiles in the pulverized coal in the stream are driven off; thereafter igniting the coal-airstream to form a flame directed into the kiln; generating a secondary combustion airstream for providing the balance of combustion air required for fully combusting the pulverized coal in the stream; heating the secondary combustion air with product discharged from the kiln to a temperature of at least about 800° F.; and mixing the secondary combustion air with pulverized coal discharged into the kiln to effect the full combustion of the pulverized coal.

Claim 3

A method for firing a coal burner for a kiln comprising the steps of: providing pulverized coal; establishing an airflow of not substantially more than 5% of the theoretical amount of air needed to combust the pulverized coal in the kiln; entraining pulverized coal in the airflow at a predetermined rate which corresponds to the desired rate with which pulverized coal is combusted in the kiln to thereby form a pulverized coal flow; mixing the coal flow with an amount of supplemental, primary air to establish a coal-airstream having no more than about 20% of the theoretical amount of air needed to combust the pulverized coal in the kiln; directing the coal-airstream through a burner tube; heating the supplemental primary air to a sufficient temperature and retaining the coal-airstream in the burner tube for a sufficient length of time to vaporize in the coal-airstream volatiles present in the coal; thereafter discharging the stream from the burner tube into the kiln; igniting the stream; and introducing sufficient secondary air having a temperature of at least about 800° F. into the kiln and in substantially surrounding relationship to the stream discharged into the kiln so as to substantially completely combust the pulverized coal in the kiln.

Claim 4

A method for firing a coal burner for a kiln comprising the steps of: providing pulverized coal; establishing an airflow of not substantially more than 5% of the theoretical amount of air needed to combust the pulverized coal in the kiln; entraining pulverized coal in the airflow at a predetermined rate which corresponds to the desired rate with which pulverized coal is combusted in the kiln to thereby form a pulverized coal flow; mixing the coal flow with an amount of supplemental, primary air to establish a coal-airstream having no more than about 20% of the theoretical amount of air needed to combust the pulverized coal in the kiln; directing the coal-airstream through a burner tube; heating the supplemental primary air to a sufficient temperature and retaining the coal-airstream in the burner tube for a sufficient length of time to vaporize in the coal-airstream volatiles present in the coal; thereafter discharging the stream from the burner tube into the kiln; igniting the stream; and introducing sufficient secondary air having a temperature of at least about 800° F. into the kiln and in substantially surrounding relationship to the stream discharged into the kiln so as to substantially completely combust the pulverized coal in the kiln.