Illustrate the General Design of Waste heat boilers
The boiler system shall be made up of a fire tube type heat exchanger, a steam drum with relief valve internals, risers and downcomers.
The required quantity and conditions of steam and all pertinent operating conditions are specified in the Design Data Sheets for the boiler. Performance of boiler shall meet all requirements over the range of ambient temperatures as specified in the above mentioned data sheets. The quantity, composition and temperatures of inlet gas are as specified.
Unless otherwise stated on the data sheet the fouling resistance's shall be 0.00044 m2 c/w (0.0025 hr.ft2 o F/BUT) for the tube side and 0.00176 m2 c/2 (0.011hr.ft2 o F/BTU) for the shell side.
The waste heat boiler (WHB) shall be designed as a horizontal fire-tube type thermasyphone using risers and downcomers with integrally supported steam drum. A single pass acid gas operating with a single steam drum unit is required. The maximum allowable pressure drop in the tubeside shall be limited to 3.45 kPa (0.5 psi).
The shell and tube side design of the heat exchanger shall be such that only nucleation-type boiling shall be present throughout the entire length of tubes under all rates of flow from the minimum turn down to a maximum design flow. Vapor blanketing shall be avoided by providing sufficient tube pitch for vapor escape maintaining a circulation ratio of average value of 15:1 with minimum individual value of 12:1, supported by calculations.
The boilers shall be designed for a load moving of 20% MCR from minimum flow to peak rate without upset or solid carryover in the stem of more than 1 ppm.