Application-based safety valves for urea plants

The synthesis section of a urea plant is core to produce urea with safely and with high on-stream times. The safety valves applied in this section must be resistant to the high corrosiveness and the tendency to crystallisation of the carbamate to be processed. The LESER Urea Synthesis Safety Valve sets in at these key requirements for the synthesis process.

• The selection of the materials is exactly optimized for the critical application and guarantees the corrosion resistance.
• The unique continuous steam purging (LESER Flush) design prevents the condensation and crystallisation of the carbamate during normal operation and during blow-off conditions. No need to service the safety valve after blowing off.
• The steam requirement and thereby the operating costs are much less than with other alternatives.
• With the LESER Support Loading System Technology significant higher synthesis operating pressures and related higher conversion figures can be realised while realising 75% less emissions during a blow off situation.

LESER’s solution against corrosion

In the last 10 years LESER has installed more than 1800 Safety valves in urea plants in almost all countries of the world.

Of these 1800, more than 320 are equipped with the LESER Steam Flushing System , which prevents clogging of the discharge pipe line and condensation and erosion corrosion in the seat area .

More than 70 Safety valves are designed with a standardized 3J4 block body design and LESER flushing system with the following advantages:

• Material of all wetted parts can be in high corrosion resistant composition
• Constant temperature of the nozzle, higher than the condensation temperature of the carbamate solution, to avoid negative corrosion effects and material structure effects of the sealing surface.
• Metal-to-metal sealing with LESER nanotightness process for sealing finish with roughness and flatness in the measuring range of 100 nm.
• 360° flushing of the main valve body to prevent crystallization in the event of a blowdown situation
• A steam supply point is required for LESER purging , even if a Heating jacket is pre-installed to heat the outer area of the block body with minimal steam consumption .

And the synthesis sections of already four urea plants are equipped with the LESER auxiliary loading system , which allows these plants to operate the synthesis pressure very close to the set pressure, resulting in significant higher conversion rates and 75% lower emissions in case of a blowdown situation.