Problem:
A Canadian Pulp and Paper Mill was having difficulty controlling steam temperatures. The plant required two steam operating conditions – 11.4 bar (165 psig) and 5.5 bar (80 psig).
The plant foreman wanted to change the desuperheater for the 11.4 bar system, which they considered to be the more critical of the two.
The plant also operated a steam turbine which caused considerable load differential depending on whether the turbine was online or offline (refer to Table 1 for 11.4 bar steam system application details).
| Turbine | Online | Offline |
|---|---|---|
| Steam - Flow | 90 t/hr | 90t/hr |
| Steam - Temperature | 272°C | 400°C |
| Water - Flow | 11.65 t/hr | 27.17 t/hr |
| Water - Pressure | 56.2 bar | |
| Water - Temperature | 135°C |
Solution:
The plant consulted with Armour Valve to determine the best choice of desuperheater for its needs. Though the steam turbine was rarely offline, the plant wanted to find a solution that had the rangeability to handle both scenarios.
They had experienced numerous problems with their existing desuperheater since its installation: temperature control varied widely, spray-water control had to be adjusted manually, and the unit also required service every year – a costly annual disruption.
At Armour Valve’s recommendation, the plant decided on the HORA Multi-Nozzle Spray Desuperheater (MNSD) because of its design and durability in service, which was delivered by Armour Valve for installation during a scheduled shutdown.
Impact:
The reaction was immediately positive, with the MNSD controlling steam temperatures at 5ºC above saturation.
The MNSD did not require any servicing for 3 years, at which point the plant considered changing over the 2 desuperheater units on its low-pressure system to HORA products.
