An authority may at any time and from time to time issue refunding bonds for the purpose of refunding the principal of and the interest on any bonds of the authority theretofore issued hereunder and then outstanding, whether or not such principal and interest shall have matured at the time of such refunding, and for the payment of any expenses incurred in connection with such refunding and any premium necessary to be paid in order to redeem, retire or purchase for retirement the bonds to be refunded. The proceeds derived from the sale of any refunding bonds shall be used only for the purposes for which the refunding bonds were authorized to be issued. Any such refunding may be effected either by sale of the refunding bonds and the application of the proceeds thereof, or by exchange of the refunding bonds for the bonds or interest coupons to be refunded thereby; provided that the holders of any bonds or coupons so to be refunded shall not be compelled without their consent to surrender their bonds or coupons for payment or exchange prior to the date on which they may be paid or redeemed by call of the authority under their respective provisions. All provisions of this chapter pertaining to bonds of an authority that are not inconsistent with the provisions of this section shall, to the extent applicable, also apply to refunding bonds issued by such authority. An authority may at any time and from time to time issue bonds both for the purpose of so refunding the principal of and the interest on any of its bonds and for any other purpose for which it is authorized to issue bonds, in which event the provisions hereof respecting refunding bonds shall apply only to that portion of such combined issue authorized for refunding purposes and the provisions thereof respecting other financing shall apply to the remaining portion of such combined issue.