Carbon Capture and Storage Low Emissions Combustor

Compressor Products

Compression is used extensively in stand alone products such as air and gas compressors, and as a critical component in gas turbine power generation and propulsion systems.

The industry is loosely divided into air compression and gas compression.

Air compressors are a relatively standard product sold to support what has sometimes been referred to as the fourth utility – 100-125 psig compressed air or “shop” or “plant” air as it is often called. It is estimated that up to 12-18% of the United States electrical energy consumption is used to drive industrial air compressors, and the DOE has sponsored numerous programs and initiatives to improve the overall efficiency of compressors and compressed air systems

Air compression is also a critical element in determining the efficiency of all types of combustion engines, as well as future hybrid fuel cell systems.

Gas compression on the other hand covers a wide variety of gases and gas mixtures, sold in more limited quantities to the chemical and process industries. These are application specific designs and include process gas compression, as well as refrigeration and pipeline compressors.

Ramgen's compression technology can be used across a wide range of current compressor applications as both a product and a component, but the emergence of CO2 compression, increasingly seen as a key component to mitigate the effects of Green House Gases (GHG) and their Global Warming effects, compels us to concentrate our development efforts in this area.

Today, there are two basic turbocompressor configurations and one hybrid form. Ramgen’s technology represents a uniquely different approach.

Ramgen Discrete Drive HP Stage
Hitatchi Inline Process CO2 Compressor


MAN Turbo Integrally Geared Compressor
MAN Turbo (Sulzer) Isotherm™ Compressor



The inline designs incorporate multiple stages mounted on a common drive shaft and are typically used in refinery and petrochemical applications. These designs are heavily oriented to API specifications and requirements and intercooling is done between separate casings, or bodies as they are called.

  • 100:1 CO2 compressor is 4-casing/12-stages
  • 3-4 stages per casing (body)
     -Stages are the same diameter and speed
     -Stage specific speed & efficiency is successively reduced thru the body
     -Pr 1.5-1.6 per stage on CO2
     -Stage-1 can be an overhung, higher ratio, open design
     -Last stage specific speed/efficiency fall-off dictates shift to smaller stage & casing
     -Thru shaft reduces flow area amplifying Mach# constraint
     -Shrouded impeller design
     -Large diameter return channels exacerbate large diameter casing working pressure design/mfg   challenges
  • External gear drive
     -Operating speeds typically above synchronous motor speeds
     -100:1 normally set up as an LP & HP train/2-casings each
     -3 x 50% deployment = 12 casings/9 gearboxes/6 drivers
     -Mechanical loss add-on ~6%
  • External intercoolers between casings
  • Control – no turn down to match constant pressure CO2 system
     -System resistance -> constant speed; variable pressure
     -Constant pressure -> recirculation
     -Variable speed & IGV’s not practical
  • Cost
     -Equipment - $1000/hp
     -Installation +75%

Inline Compressor Designs

Integral geared designs are rooted in the air compressor market and have found some level of acceptance in selected gas compression applications. Individual stages of compression are driven through a common bullgear and intercooling can be done after each stage.

  • 100:1 CO2 compressor is 8-stages/6 or 7-intercoolers
  • Common drive thru an integral bullgear to compression stages
     -4 pinions, double horizontal split casing
     -Individual compression stages mounted on opposite ends of each pinion
     -At least one stage on each pinion is operating off its optimum specific speed.
     -Pr 1.7-1.8 per stage on CO2
     -Stage temperature rise approximately 100°F
     -Stage-1 impeller can be an open design at Pr of 2.0:1
     -Later stages suffer sharp aero efficiency falloff due to their small size
     -Even number of stages required to balance thrust loads
     -Frames are “torque limited” by the gearing and therefore “power rated”
  • External intercoolers between casings
     -Low Pr per stage aero requires very low DP intercoolers
     -CO2 requires stainless steel intercoolers
     -Stainless steel has low a heat transfer properties
     -Concerns exist over 2-phase flow, aggravated by intercooling near the critical point
     -Impurities add another level of uncertainty
  • Control – 30% turndown at constant pressure
     -IGV’s are common practice and can be applied on intermediate stages
     -System resistance -> constant speed; variable pressure
     -Full variable speed is not practical; variable speed trim possible
  • Cost
     -Installation 50-75% depending on intercooler configuration
  • API oriented customers do not like integral gear drives

Integral Gear Compressor Designs

An “Isothermal” design is a attempt to introduce a level of intercooling between stages of an inline compressor to compete with the efficiency of an integral geared unit, and have been applied in very large capacities where gear peripheral speeds impose limitations on the center distances required to support large stages and where the operating speeds are such that a direct drive configuration can be employed.

"Isothermal Process is one in which there is no change in temperature" .....I-R Compressed Air & Gas Data

  • Described as a 30-year old concept
  • Originally intended to achieve some level of intercooling on an inline design
     -Inspired 30+ years ago but Sulzer’s lack of an   integrally-gear offering
     -Sulzer recently sold compressor business to   MAN Turbo
  • Built-in intercooler
     -Are not low AP, high effectiveness “high-   performance” designs
     -Space limits in material availability
     -Horizontal split casing required for   cleaning/maintenance
     -Horizontal split casing limits working pressure

"Isothermal" Compressor Designs

The Ramgen Compressor utilizes an independent drive for each of its compression stages. Stage pressure ratios can be 10-12:1 on CO2. Intercooling is used between the LP and HP stages for a compression ratio of 140:1, typical of the CO2 application.

Ramgen Discrete Drive HP Stage
Ramgen Compressor Rotor
  • 100:1 CO2 compressor —> 2-casings/2-stages
     -No aero Mach# limit
     -10+:1 pressure ratio; 400°F temperature rise
     -1400 fps tip speeds; Shrouded rotor design

  • Single-stage, discrete-drive
     -Single stage per drive optimizes specific
      speed match
     -Simple single-step external gearbox or high
      speed direct drive
     -Lower mechanical losses

  • Variable speed option
     -Match MW and temperature changes with
      speed changes

  • Configuration adapts easily to match
    process requirements
     -Mismatched thru-flow
     -Side stream additions

  • Active IGV Flow control on each stage
     -Match CO2 capture system constant
      pressure requirement

  • Heat exchangers
     -Inter/aftercooler can be the CCS or power plant
     -“Compressor” heat exchanger cost can be
     -Eliminate or substantially reduce cooling
      tower requirement
     -Eliminate or substantially reduce cooling tower
      make-up water
     -3x LMTD _ heat exchangers with 1/3 the
      surface area

  • 1/10th the physical size – facilitate space
    constrained retrofits

  • 1/2 the installation cost



Ramgen Compressor Designs


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