A post-combustion lance for directing a gas at least partially therethrough. The post-combustion lance includes a body extending between an upstream end and a downstream end of the lance, the body including upper and lower portions and a post-combustion distributor mounted therebetween. The lance also includes an internal support assembly for supporting the body, the internal support assembly including an internal tube positioned inside the body and at least partially engaged with the lower portion, and at least partially engaged with the upper portion of the body, so that the internal support assembly supports the body both upstream and downstream relative to the distributor. The lance also includes a lower o-ring gland positioned downstream relative to the internal support assembly and an upper o-ring gland positioned upstream relative to the lower o-ring gland.