The horizontal tube ring type is a tube ring composed of a plurality of parallel tubes, which spirals up along the four walls of the furnace, with three sides horizontal and one inclined, or two sides horizontal and two sides slightly inclined. The main advantages are: there is no intermediate header and unheated downcomer, which can save metal and facilitate sliding operation. The main disadvantages are: low installation combination rate, large field workload, uneven heat absorption along the furnace height when using in large capacity, which will make the thermal deviation between tubes too large.

Vertical tube screen type (bunsen burner type) is to arrange multiple vertical tube screens around the furnace and connect them with pipes outside the furnace. The water walls of the whole boiler can be connected in series into one group or several groups, and the working medium flows through each tube screen in a group in turn, and each group is connected in parallel. This kind of water wall has the advantages of high combination rate, simple installation, multiple mixing of working fluids in the header and small thermal deviation. Disadvantages are: more downcomers and headers are used, which consumes a lot of metal and is not suitable for pressure swing operation.

The circuitous pipe ring (Sulzer type) is a pipe belt composed of several parallel pipes, which circuitous up and down or horizontally along the inner wall of the furnace. Advantages: there is no sewer pipe, which can save steel. Disadvantages: The pipeline between the two headers is very long and the thermal deviation is large, which is not conducive to the free expansion of the pipeline and is not suitable for the membrane wall structure.