Page 8 - European Energy Innovation - Autumn 2015 publication
P. 8
utumn 2015 European Energy Innovation

Recycle your Steam and Save Energy

The potential of Mechanical Vapour Recompression (MVR) using Radiax® Technology

INTRODUCTION its latent energy, reaching COP RADIAX® COMPRESSOR
Steam systems are a part of values up to 10. TECHNOLOGY
almost every major industrial Different types of compressors
process today. For various After a short introduction of MVR, such as centrifugal fans,
heating processes steam is used this article describes the Radiax® turbo-compressors and rotary
as heat carrier for evaporating compressor. This compressor has root blowers are suitable as
solvents in distillation columns, been developed by Bronswerk mechanical vapour compressors
drying processes, reactor and has several advantages in if operating according to
columns, etc. Roughly a quarter comparison to conventional the principle of continuous
of the oil and gas consumed compressors. Many of these flow machines. However,
in the process industry is used advantages are relevant for MVR. each compressor type has its
to generate steam. As steam limitations on pressure ratio,
production is in most cases one THE PRINCIPLE OF MVR volume flow and operating
of the largest energy users and During MVR, a mechanically flexibility. Bronswerk Heat
plant arrangements are often driven compressor increases Transfer has developed a new
outdated, improvements can the pressure of a steam flow. compressor which eliminates
lead to significant energy savings. The compressor operates as a various limitations known from
Besides saving costs, enterprises heat pump by adding energy conventional compressors. Figure
are taking more responsibility to the vapour. Contrary to the 2 illustrates a cross section of
nowadays for their impact on compression heat pump with its the Radiax® compressor. The
society and therefore focus on separate circulating fluid (closed specially designed inlet rotor
improving energy efficiency. MVR system), MVR operates as an ensures no-stall characteristics,
can be a solution for reducing open system. In an open heat which result in a smooth axial
your energy costs and carbon pump system the process fluid pressure rise. The divergent
footprint significantly. (in this case steam) is also acting design of the rotor contains a
as the circulating fluid. Due to large number of blades. The rotor
The basic principle of MVR is the elimination of the evaporator, is capable of reaching tip speeds
recycling unused low-value steam, condenser and separate close to the speed of sound while
mechanically converted into circulating fluid, high COPs, up to converting flow speed in dynamic
high-value steam while preserving 10, can be obtained. pressure. The rotor is directly
driven by the electric motor.
Figure 1: Log(p)-h diagram for water vapour An example MVR cycle is Vapour leaving the rotor enters
illustrated in the log(p)-h water the stator-diffusor where dynamic
vapour diagram (figure 1). The pressure is converted into static
mechanical work delivered by the pressure. Vapour enters the
compressor is depicted as dH. stator-diffusor tangential and is
Steam leaving the compressors guided by 3D designed channels
is slightly superheated due ensuring a perfect transition in
to the dissipated thermal axial direction. The rotor, electric
and mechanical losses of the motor and stator-diffusor are
compressor. If favourable, the integrated in a single casing,
superheated steam can be which minimises the amount
tempered or de-superheated to of components and leads to a
its saturation point by injecting compact design.
boiler feed water (BFW) in order
to attain the required process Advantages of the Radiax®
conditions. compressors compared to
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