Carbon Steel Power Plant CFB Boiler Steam Drum / High Pressure High Temperature Drum

                  Carbon Steel Power Plant CFB Boiler Steam Drum / High Pressure High Temperature Drum

Introduction

A steam drum is a standard feature of a water-tube boiler. It is a reservoir of water/steam at the top end of the water tubes. The drum stores the steam generated in the water tubes and acts as a phase-separator for the steam/water mixture. The difference in densities between hot and cold water helps in the accumulation of the "hotter"-water/and saturated-steam into the steam-drum.

The steam drum is the primary interface between water and steam. In a coal-fired plant, boiler feedwater passes through the economizer and into the drum where the steam separates from the feedwater and is drawn off to the superheater.Maintaining constant liquid level in the upper part of the steam drum is necessary to provide the proper quality of steam. Instrumentation must withstand high temperatures and pressures.

Working Procedures

The working conditions of drum are complex and the consequences of accidents are serious. It is necessary to strictly control the chemical composition, mechanical properties and welding and processing quality of material used in drums, and to pass a series of strict tests. The cylinder is composed of a cylinder body and a head.

1. Cylinder:refers to the cylinder part of the drum. Its inner diameter and length are related to the circulation mode, boiler capacity, steam parameters and the structure of inner equipment. Steam drum is usually rolled on multi-roll reel machine. The drum wall of subcritical pressure boiler is too thick to be pressed on giant press.

2. Head: Subcritical pressure boilers are usually hemispherical, high pressure and ultra high pressure boilers are ellipsoidal, medium pressure boilers are relatively flat ellipsoidal, with manholes on the head for installation and maintenance of internal devices. The head is pressed on a hydraulic press or an oil press.

1. The mixture of steam and water coming from the water wall enters the drum through the upper inlet pipe of the drum. Along the narrow annular passage formed by the inner wall of the drum and the arc liner, the steam-water mixture can be uniformly transferred to the inner wall of the drum at an appropriate flow rate, thus overcoming the difficulty of excessive temperature difference between the upper and lower walls of the drum during start-up and shutdown of the boiler and enabling faster start-up.

2. The steam-water mixture entering the drum enters the steam-water cyclone separator, and uses the inertia of changing the flow direction to separate the steam-water mixture, which is the first separation of the steam-water mixture.

3. The separated steam still contains a lot of water. It enters the corrugated plate separator from the top of the separator. The steam with some water droplets flows through the cracks between the corrugated plates, and the water film is formed on the metal wall to flow downward.

4. The steam after secondary separation is finally cleaned by steam, and gravity separation is carried out by using the density difference of water, which is the third separation.

5. After three separations, the steam meets the steam quality standard, and leads to the platen superheater from the saturated steam pipe at the top of the drum.

Steam-water separation details

Primary steam-water separation removes nearly all the steam from the water so that very little steam is recirculated from the drum bottom towards the heated tubes through the outlet connection (downcomer).

At secondary separation, steam is passed through a secondary stage of separators or scrubber elements (usually closely spaced corrugated parallel plates) for final water droplet removal. Steam is then exhausted through various ports.

Accessories

The main components in a boiler system are the boiler feedwater heaters, deaerator, boiler, feed pump, economizer, boiler, superheater, attemperator, steam system, condenser and the condensate pump. In addition there are sets of controls to monitor water and steam flow, fuel flow, airflow and chemical treatment additions.

Classification

Quality Control

1. Impact test and Strength calculation report with applied materials information.

2. 100%NDT(non-destructive inspection) report of steel plate, tube and electrode

3. X-ray, γ-ray and liquid penetrant test inspection report (welding seam): to ensure the quality of the entire boiler

4. Hydraulic test report: ensure the standard working pressure and safety