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Development and operation of liquid ammonia filter


Due to incomplete gas purification, the service life of synthetic catalyst in coal based ammonia plant is short and the catalyst is replaced frequently. Although hydrogen and nitrogen entering the synthesis system are separated twice by oil-water separator, some oil-water still enters the synthesis system. Impurities such as oil, water and catalyst powder are suspended in liquid ammonia, which can not be purified by natural sedimentation. They are added into the ammonia cooler together with liquid ammonia, which is easy to stick on the wall of the snake tube and affect the heat transfer effect; It is added into the ammonia cooling system of the circulator to block the pipeline and burn the packing. For this reason, we changed the scrapped angle stop valve into liquid ammonia filter, which was used before ammonia cooling of refining, synthetic ammonia cooler and circulator respectively.

Take out the valve rod, valve core and valve seat of the scrapped j41h-320-x angle stop valve, weld a 2.5 MPa flange at the end of the valve body with valve core, and process the inner hole of the valve seat into internal thread. Take a section of steel pipe, one end is processed into internal thread, and the other end is welded with steel plate with many small holes. After welding, it is welded with the processed steel pipe with external thread.

The steel pipe with internal thread is filled with 40 mesh filter element, and then the filter element is made by tightening the screw plug with many small holes. Connect the filter element with the valve seat through the thread and install them into the valve body together.

Installation and process principle

Connect the filter inlet a with the liquid ammonia pipe from the liquid ammonia storage tank. Outlet B is connected with ammonia cooler or ammonia cooler of circulator, and the inlet and outlet of liquid ammonia filter shall be equipped with valves and a shortcut pipe. The reverse drain outlet C is connected with the gas ammonia pipe of the absorption post.

The liquid ammonia enters from a through the interlayer between the valve seat and the filter element, and enters the filter element through the small hole on the oil plug. After separation by filter cloth, liquid ammonia enters ammonia cooler or ammonia cooler of circulator from B, and impurities such as oil stain and catalyst powder are trapped in filter cloth, filter core and valve seat interlayer. Regularly close the inlet valve of liquid ammonia filter, open the shortcut, liquid ammonia filter outlet and reverse blowdown valve.

Under the condition of normal ammonia supply, the impurities such as oil stain and catalyst powder in the filter are discharged into the gas ammonia pipe, and the discharged ammonia is recovered by dilute ammonia water in the absorption post. After the filter is backwashed, close the shortcut and reverse blowdown valve, open the inlet valve, and the liquid ammonia filter can be put into operation again.