CONDITIONING SKIDS
Skid mounted gas conditioning packages for ensuring the quality of inlet (fuel) gases used in turbines and gas engines. These packages are generally designed for natural gas, coal bed methane. In some cases, they can also be designed to accommodate low calorific gases like coke oven gas, blast furnace gas.
Some of the common contaminants that are removed in these packages:
Sand & ClayHydrocarbon liquid
RustGas hydrates
SlugCalcium carbonate
Glycol from dehydratorConstruction debris
Water & SaltwaterCorrosion Inhibitors
Iron sulfate, copper sulfideOther condensates
Lubricating oilAmines
The conditioning process has two / three stages:
Particulate removal– Dust, particulate contaminants, rust and slug from pipelines is removed by mechanical separation and filtration
Removal of condensable – Handling of water and other condensing constituents
Provision of superheat or dew point depression
The design approach is based on process simulations to determine the condensing temperature, hydrate formation temperature, water, and constituent dew point before deciding the individual stages of cleaning and conditioning.
The packages are capable of achieving:
Removal of particulate matter up to 3 Μ. In some cases 10 Μ as per specification
Removal of all free liquids at the inlet of the turbine or the engine even with the variation of the inlet pressure and temperature of the gas
Provision of a superheat of 28 °C above the hydrocarbon or water dew point at the inlet of the turbine (to avoid condensation in control valves)
Water dew point depression (for gas engines), so that the engine inlet sees a relative humidity of 70 – 80 %
Description of equipment used in the gas conditioning packages:
Dry Scrubber (multi-cyclone)
Multi-cyclone unit (40 m3/hr, 80 m3/hr capacity each) with a turndown of 4:1. Gas enters tangentially through a port which imparts high centrifugal force, throwing solid and liquid particles against the wall of the cyclone, resulting in separation. They can also be provided with coalescing filters to have better turn down. In case there are no liquid particulate filters can be used to achieve better turndown.
Gas Separator (vane separator)
Operates also operates on inertial force separation principal. Wet gas passes through an inlet baffle where the liquid slug is removed. The gas then passes through a series of angled vanes that impart inertial forces on the remaining liquid droplets. The droplets strike the vane and are removed from the flow stream by gravity. Horizontal or vertical configuration possible.
Coalescing Filter
Used for removal of liquid droplets. Available up to 0.008 ppm and 1 Μ. The filter module consists of a vertical vessel with a number of parallel coalescing cartridges. Cartridges are made of borosilicate glass fiber and have an outer drain layer of chemical resistant polyester with stainless steel perforated plate backing and helical spring support. Gas flows from into out and liquid is separated out from the bottom.
Combined Separator (Filter Separator)
Combination of coalescer and vane separator.
Pressure Reduction Valve
In case the pressure of the inlet is higher than permissible at the turbine inlet, a pressure reduction valve is provided.
Electric Heater (for the provision of superheat)
Designed for the hazardous zone to maintain the temperature above the condensing temperature after the expansion in the pressure reduction valve or providing superheat at the gas turbine inlet. In case a compressor or blower is used in the circuit to boost inlet pressure, they can also be used to provide superheat.
Waste Heat Fired (water bath) Heater
Hot water is generated in a vessel by firing the waste gas and the cold inlet gas passes through a coil to pick up the heat.
Gas to Gas Cooler/Heater and Chiller
Used in case dewpoint depression is warranted (for gas engines).
