Method for in situ coating a tower solar receiver

Abstract

The invention relates to a method for in situ coating a tower solar receiver in order to protect the surface of the receiver from corrosion and to increase absorptivity of same, which is carried out in several steps: surface preparation, application of the coating, curing, optional vitrification, and controlled cooling. The surface preparation is done by zones depending on the size of the receiver, a methodology that enables an intercalated application of the coating in order to minimize the risk of corrosion. The curing stage is carried out by supplying steam to the inside of the receiver tubes, and temperature requirements above the operating limits of the boiler are adjusted with the solar field as support system. Vitrification is done using saturated steam traveling through the receiver tubes and concentrating solar radiation on the surface of the receiver from the solar field.

1 . Method for in situ coating of a tower solar receiver, comprising the following steps:
 a) Surface preparation of the receiver   b) Application of the coating   c) Curing of the coating by means of the circulation of steam through the inside of the receiver   d) Controlled curing of the receiver   
     
     
         2 . Method of coating according to  claim 1 , characterized in that a delimitation of the surface of the receiver into several zones is carried out prior to the surface preparation. 
     
     
         3 . Method of coating according to  claim 2 , characterized in that steps a) and b) are carried out by the zones into which the surface of the receiver has been delimited, said steps being intercalated to minimize the time between them. 
     
     
         4 . Method of coating according to  claim 3 , characterized in that the application of the coating on each area of the receiver which surface has been previously treated is carried out less than eight hours after the execution of the surface treatment. 
     
     
         5 . Method of coating according to  claim 1 , wherein the surface preparation is carried out by blasting the surface with a pressurized abrasive material. 
     
     
         6 . Method of coating according to  claim 1 , characterized in that the application of the coating is carried out by airless spraying. 
     
     
         7 . Method of coating according to  claim 1 , characterized in that after the curing step and prior to the controlled cooling step of the receiver, a vitrification step of the film of coating by means of the supply of steam through the inside of the receiver and by means of the concentration of solar radiation coming from the field of heliostats at the surface of said receiver, is carried out. 
     
     
         8 . Method of coating according to  claim 7 , characterized in that the concentration of radiation on the receiver in the vitrification step is carried out by focusing the heliostats of the solar field towards the receiver in a controlled manner at a heat input ratio of 5 MWt every 10 minutes, until reaching the vitrification temperature recommended by the coating manufacturer for this operation. 
     
     
         9 . Method of coating according to  claim 1 , wherein the curing process, in addition to being carried out by means of the supply of steam through the inside of the receiver, uses the solar field as support system to maintain a constant heat input towards the receiver until reaching the temperature recommended by the coating manufacturer for this operation. 
     
     
         10 . Method of coating according to  claim 1 , wherein the controlled cooling of the receiver is carried out by means of the controlled defocusing of heliostats of the solar field and wherein, after removing the heat input, the circulation of cold fluid through the receiver begins. 
     
     
         11 . Method of coating according to  claim 10 , wherein the defocusing of the heliostats is such that the heat input is reduced in 5 MWt every 10 minutes, and the recirculation of the cold fluid through the receiver is carried out by means of recirculation pumps until the surface temperature is below 100° C., when the pumps are disconnected and the receiver is allowed to cool to room temperature.