Compressed Air Transmission and Treatment

Antony Barber C.Eng., M.Sc., F.I.Mech.E., G.R.Ae.S. , in Pneumatic Handbook (Eighth Edition), 1997

Element life

In coalescing filters, element life is adamant by pressure drib, in absorption filters, element life is governed by saturation. It is worthwhile changing the filter elements at prescribed periods whether or non the pressure drop indicates it to exist due. Elements should exist changed at least once a year.

Chemical element life depends on the type of compressor supplying the system. An oil-free rotary compressor has a minimum of oil carry-over; a reciprocating compressor is adjacent best.

In a rotary flooded compressor, an oil separator is fitted as part of the organisation to minimize oil carry-over. The remaining aerosols in the delivery line are of the lodge of 0.1 to 0.five micron. A sub-micron filter is necessary to deal with these. If at that place should be a separator failure or at that place is poor maintenance, large quantities of oil can be carried over and cause immediate failure of the filter chemical element.

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Fans, Blowers, and Compressors

Stephen Hall , in Branan's Rules of Thumb for Chemical Engineers (5th Edition), 2012

Good Engineering Practice

•

Monitor compressed air filters, such as wet coalescing filters, to ensure they are cleaned or changed when dingy. A typical coalescing filter has a force per unit area drib of 2 psi. A pressure drop of six psi adds two% to the free energy cost for running the compressor.

•

Install differential pressure gauges on compressed air inlet filters. A rule of thumb is that a ii psi force per unit area drop reduces capacity past 1%.

•

Provide pressure sensing points at the compressor discharge, before and later dryers and filters, and throughout the distribution system to each point of use (compressed air systems).

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Air and Gas Filter Media

Derek B Purchas , Ken Sutherland , in Handbook of Filter Media (Second Edition), 2002

5.6.1.2 Air/oil separator

The air/oil separator is basically a coalescing filter. It follows the compression, and comprises master and secondary stages, with the objective of reclaiming the lubricating oil prior to the air being discharged at the required force per unit area. The primary stage utilizes gravity settling assisted by a reduction in gas velocity; downstream from it, the typical oil loading is five–l yard/m three of polydispersed aerosols.

The 2nd stage is ordinarily a multi-layer cartridge, the media used depending on whether the menstruum through it is out-to-in or in-to-out. With the latter, the get-go, prefiltration layer tin can be a choice of several high particulate loading fibrous fabrics, such as a 0.iii–0.7 mm thick, 100 g/m2 viscose rayon bonded with regenerated cellulose. In that location is then an overlapping support layer, typically a i mm thick, 120 g/one thousand2 50% mixture of polyester/nylon bonded with synthetic condom; the function of this is to comprise the multiple layers of high-efficiency media wherein the fine oil mist droplets coalesce into much larger droplets.

These high-efficiency layers are of borosilicate glass fibres of various characteristics. They include a thin felt of coarser fibres bonded with phenolic resin and as well microfibres bonded with an acrylic binder; integral support layers of spunbonded nylon provide intimate support for the fragile glass media to help the separator survive the rigours of frequent changes in pressure and the resultant circadian loading of the media. Following the coalescing activity of the glass fibre media, the large oil droplets are prevented from re-entrainment by a bulwark comprising a iii–v mm thick, 250 g/mtwo nylon or polyester non-woven acrylic bonded fabric; this ensures rapid drainage of the coalesced liquid to the base of the separator, for subsequent pressurized expulsion back to the air intake.

The whole coalescer assembly is resin bonded and mechanically locked into terminate caps of suitable location design, thus forming a highly efficient separator capable of removing particles down to 0.3 μm at over 99.995% efficiency. Oil carryover from a compressor is usually less than v mg/m3 of air; this allows for long service periods for the compressor.

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Gas Sweetening1,2

Maurice Stewart , Ken Arnold , in Gas Sweetening and Processing Field Manual, 2011

Traditional Pretreatment

Figure 1-24 shows the equipment used in traditional pretreatment organisation:

Effigy 1-24. Traditional membrane pretreatment.

Coalescing filter for liquids and mist elimination

Nonregenerable adsorbent guard bed for trace contaminant removal

Particle filter for dust removal subsequently the adsorbent bed

Heater for providing sufficient superheat to the gas

Figure i-24 menses scheme is acceptable for light, stable limerick gases, simply it has the following limitations:

Adsorbent bed is the only piece of equipment that is removing heavy hydrocarbons.

A sudden surge in heavy hydrocarbon content or heavier than initially estimated feed gas can saturate the adsorbent bed inside days and render it useless.

Since the beds are nonregenerable, they tin can get functional over again only after the adsorbent has been replaced.

Problems with the heater crave that the whole membrane system be taken offline, because the heater is the only slice of equipment providing superheat.

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Gas Sweetening

Maurice I. StewartJr. PhD, PE , in Surface Production Operations (Third Edition), Volume 2, 2014

9.9.iii.3 Traditional Pretreatment

Figure 9.24 shows the equipment used in a traditional pretreatment system: a coalescing filter for liquids and mist emptying; a nonregenerable adsorbent guard bed for trace contaminant removal; a particle filter for dust removal after the adsorbent bed; and a heater for providing sufficient superheat to the gas.

Effigy 9.24. Traditional membrane pretreatment.

Figure 9.24 too shows a flow scheme that is acceptable for light, stable composition gases only also has the following limitations. The adsorbent bed is the just piece of equipment that is removing heavy hydrocarbons. A sudden surge in heavy hydrocarbon content or heavier than initially estimated feed gas can saturate the adsorbent bed within days and render it useless. Since the beds are nonregenerable, they can become functional again only afterward the adsorbent has been replaced. Problems with the heater require that the whole membrane organisation be taken offline, considering the heater is the only slice of equipment providing superheat.

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Gas Compression

David A. Simpson P.Eastward. , in Applied Onshore Gas Field Engineering science, 2017

viii.three.3.4 Coalescing element

We oftentimes call the big lump of steel on the backside of the skid a "coalescing filter." It is not a filter. The coalescing elements look somewhat like filter elements, merely they serve a different function. The coalescing chemical element is intended to forcefulness small droplets (that are buoyant in the gas stream) to crash into other aerosol and coalesce into larger drops that are not buoyant in the gas. Every bit is normal with whatever piece of equipment, in that location is a range where they are more effective. It is recommended to endeavor to get the same magnitude of velocity in a coalescing chemical element as the target velocity for in a separator mist pad (see Chapter v: Well Site Equipment).

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Polymeric membranes for natural gas processing

S.East. Kentish , in Avant-garde Membrane Science and Technology for Sustainable Energy and Environmental Applications, 2011

eleven.v Application and integration into natural gas operations

The effectiveness of natural gas membrane operations relies heavily on an efficient pretreatment organization. As discussed in Section 11.four, the presence of significant quantities of condensable contaminants results in plasticization and competitive sorption. Contagion of the membrane surface or back up structure with liquids reduces mass transfer past providing a farther resistance to menses (Echt, 2002). In the simplest scenario, these condensables are removed by 'dew-pointing', That is, the gas stream is cooled to condense such contaminants and and so reheated to ensure that the gas is at least 10–15   °C higher up the dew signal.

A more complete pretreatment operation could involve a number of steps (Echt 2002):

1.

a chiller or cooler, to reduce temperature and thus cause condensation of contaminants;

2.

a coalescing filter, knock-out drum or a mist eliminator vessel to remove particulate matter and entrained liquids;

3.

a guard bed using an adsorbent such every bit activated carbon to remove the heaviest hydrocarbon fractions, including compressor oil;

4.

a downstream particle filter to capture any fines from the baby-sit bed;

5.

a pre-heater to heat the gas stream above the dew signal, to ensure that condensation of liquids does non occur even on the permeate side of the membrane. This pre-heater also ensures that the membrane is operated at a uniform temperature and hence provides consequent operation.

Other pretreatment options include thermal swing absorption using silica gel to remove heavy hydrocarbons (Anderson and Siahann, 2005). While non a necessary footstep for membrane processing, mercury is often besides removed at this phase using an adsorbent guard bed, to prevent amalgamation and embrittlement of aluminium and other metals in downstream piping.

A conclusion must be made as to whether a hollow fibre or spiral wound module format will be utilized. Hollow fibre modules give more membrane surface area per unit volume only will have a higher pressure drop on both retentate and permeate sides. The feed gas is usually supplied to the shell side of the module to minimize this pressure drop and to reduce compaction; hollow fibres are much stronger under compression than expansion (Kohl and Nielsen 1997). A number of modules tin be employed in series and this will pb to higher recoveries, but a greater force per unit area drop.

In many cases, the apply of a single membrane stage would pb to unacceptable losses of product methane. In such cases, two membrane stages are usually employed (Fig. 11.7). While these reduce hydrocarbon loss, the need for a compressor adds to both operating and uppercase costs.

11.seven. Two-stage natural gas sweetening arrangement

 (adapted from Echt, 2002).

Another selection often utilized is to place a single membrane phase upstream of a solvent absorption unit. This hybrid arrangement provides a better product purity than can exist achieved by a single stage membrane unit and lower energy and operating costs than is possible with a solvent system lone (Echt, 2002). This approach tin can be peculiarly bonny for an offshore gas supply. The more meaty and lighter weight membrane skid can be placed offshore to remove the majority of the COtwo, reducing the capital and operating costs associated with bringing this gas onshore. The COtwo permeate tin can frequently be reinjected directly into the well, increasing recovery rates and minimizing the carbon footprint. An onshore solvent absorption unit so increases the purity of the production methane.

For Due north2 separation from natural gas, a single stage is sufficient for feed streams of half dozen–8% Ntwo. For higher nitrogen concentrations, two stages are necessary (Lokhandwala et al., 1997). For case, for feeds of eight–15% North2 (Fig. 11.viii), the starting time phase is used to remove pipeline quality natural gas as permeate, but the retentate retains significant quantities of methane. This retentate is thus directed to a 2nd stage for additional methane recovery. The permeate from this stage, containing half-dozen–x% nitrogen is recycled to the feed stream. The retentate can be used straight as a compressor fuel or sent to a third stage for enhancement of the heating value prior to such apply.

xi.8. Menses scheme required to bring 200 psia natural gas streams with viii–fifteen   mol% nitrogen content to pipeline specification (≤ 4% nitrogen) using membrane-based separations

 (reprinted with permission from Lokhandwala et al., 2010).

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Simple Cycle Power Constitute Equipment

Kenneth Storm , in Industrial Piping and Equipment Estimating Manual, 2017

3.15 Balance of Plant-Equipment Installation Man Hours

Facility-Simple Cycle Power Plant Actual Estimated
MH BM IW MW MH
Shop Fabricated Tanks
Aqueous ammonia storage tank 70 0 0 0 0
Fuel gas liquids drain tank 45 0 0 0 0
Fuel gas drains tank 21 0 0 0 0
Filters
Fuel gas coalescing filters 80 0 0 0 0
Fuel gas terminal filter fourscore 0 0 0 0
Wastewater filter fourscore 0 0 0 0
Compressors and Generators
Fuel gas compressor skid 800   hp 300 0 0 0 0
Equipment and Skids
  Ammonia forwarding pump A/B skid twoscore 0 0 0 0
  Ammonia unloading sideslip 40 0 0 0 0
Air compressor skid A/B 19 0 0 0 0
Compressed air receiver 20 0 0 0 0
Compressed air dryer skid; fifty   hp 22 0 0 0 0
Sodium hypochlorite injection slip twoscore 0 0 0 0
Fire pump sideslip 40 0 0 0 0
CEMS 80 0 0 0 0
Process wastewater sump forty 0 0 0 0
Oil/h2o separator 40 0 0 0 0
Pumps and Drivers
  Ammonia pump A/B 40 0 0 0 0
Demin water transfer pumps A/B (7.five   hp) twoscore 0 0 0 0
Process wastewater sump pump 2   hp 20 0 0 0 0
Oil/h2o sump pump 40 0 0 0 0
Service water pumps 40 0 0 0 0
Equipment installation man hours 1236 0 0 0 0

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Introduction to Natural Gas Processing Plants

William A. Poe , Saeid Mokhatab , in Modeling, Command, and Optimization of Natural Gas Processing Plants, 2017

1.3.1.viii Gas Compression and Manual

Feed gas to the gas plant is typically reduced in force per unit area such that phase separation is viable. Most often, recompression of the residual gas to the pipeline pressure level is necessary. Major projects are being planned to move massive amounts of HP sales gas from processing plants to distribution systems and large industrial users through big-diameter buried pipelines. These pipelines apply a series of compressor stations forth the pipeline to move the gas over long distances.

Compressor stations comprise one or more compressor units (designed with enough horsepower and throughput capacity to meet contractual requirements levied on the organisation), each of which will include a compressor and commuter together with valves, control systems and exhaust ducts, and noise attenuation systems. Nearly compressors are powered past natural gas taken direct from the pipeline, but electric-powered compressors are becoming more common.

A typical single-stage compressor station pattern, as shown in Fig. i.23 , may consist of an inlet scrubber to collect entrained liquids (i.due east., h2o, corrosion inhibitors, and hydrocarbon liquids that may have formed in the gas transmission pipeline) followed by a coalescing filter 5 to remove fine solids (i.eastward., piping scale) and hydrocarbon mist from the gas that could otherwise contribute to compressor failure. From the scrubber, the gas is taken to the compressor unit(s) where it is compressed. At the compressor station discharge or between compressor units in example of series arrangement the gas is cooled, typically with an air libation, and so it passes through a scrubber allowing drainage of whatsoever formed liquid. In case of reciprocating compressor usage, a coalescing filter shall exist used after the scrubber to remove lube oil mist before introducing the gas into the pipeline.

Figure 1.23. Schematic process diagram of single-stage gas compressor station.

Each compressor station volition be congenital upward from the same functional blocks of equipment shown in Fig. one.23. Each functional element plays a function in the work of the station and the design and sizing of each is essential to the efficient and safe performance of the found.

The functional elements include gas scrubbing and liquid removal, compressor and driver units, aftercoolers, pipes, and valves. Controls, including the Supervisory Control and Information Acquisition (SCADA) organisation, monitoring and data recording, alarms and shut down procedures, and both routine and emergency, are an integral part of the station. Provision also has to be made for venting the compressor and driver housing and buildings, complete with ventilation and fire protection, and safety equipment.

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Nonwoven textile filters

N. Mao , in Advances in Technical Nonwovens, 2016

10.iv.4 Nonwoven coalescing filters

For applications requiring compressed air/gases of high quality (eg, oil contents as low as 0.01   ppm) or smell elimination, air filtrations are needed to eliminate submicron liquid particles in the air and gases. Conventional filters simply having mechanical separation mechanisms are not effective on those small liquid aerosol particles. Filters containing adsorbents (eg, activated carbon) and absorbents (eg, porous polymer materials) are one of the options. Still, adsorptive materials (ie, activated carbon), which capture vapour molecules and small liquid particles via surface attraction forces, take express adsorption capacities and lose their adsorptive properties quickly when saturated with liquids accumulated. Absorbent filter materials containing wool, viscose, cotton wool, and superabsorbent polymers will blot liquids into their interior porous structures. They also have limited absorption capacities and easily become ineffective after being saturated with liquids.

Coalescing is a technique used in filter media for the separation of liquid aerosols and droplets from a gas, and coalescing filters are specifically designed to remove submicron oil, water, and other liquid droplets from airflows. It is used for the removal of mist and foggy pollutants, irritants, and odours in natural gas vehicle filtration, compressed air filtration, compressed natural gas filtration, mist elimination, and air oil separation.

The liquid droplets in the airflow are removed through the coalescence process in which two or more liquid droplets come up into contact with each other to overcome surface tensions of the droplets to coalesce. 169 Nonwoven coalescing filters capture liquid aerosols in private fibres with depth filtration mechanisms including gravitational settling, inertial impaction, direct interception, and diffusion interactions. After the small liquid aerosols are arrested on the filter fibres, they gradually coalesce and abound together to form larger oil droplets in the coalescing filter fibres. The gravitational force of these coalesced larger aerosol increases gradually against the elevate force between the droplets and the airflow; when the larger oil droplets take reached a critical mass, the aerosol volition drift to gravitate to the bottom of the media and eventually drain out of the filter media. 170

Therefore, coalescing filter elements installed in a house have three layers of filter fabrics with contaminated airflow passing through the filter element inside to outside. The inner layer is a capture layer, and the outer is a coarser drainage layer, and a high-efficiency coalescing layer commonly sits in betwixt. When oil mist is to exist removed, the fine fibres of the inner layer are usually water absorptive and modified with functional resins to exist oleophobic to help release oil particles. Oleophilic borosilicate glass microfibers are ordinarily used in making the coalescing layers to capture the fine liquid aerosols and droplets, which run together forth the fibres to class big drops within the depth of the element. These large drops are then forced to the outside of the filter element to be drained to the bowl of the housing by gravity. Coalescing filter elements will too remove particulates at the same efficiency as particulate type elements of the same grade.

Specific surface area and geometry of fibres, fibre orientation, fibre and fabric surface properties and morphologies, filter fabric porosity, thickness, and composite structures influence the liquid wetting, spreading, and accumulation on the fibre surfaces, and thus are crucial for coalescing filter efficiency. For example, the sizes and surface property of the binders used in chemic bonded nonwoven fabrics are important variables that bear upon the coalescence filtration performances. It was reported that a novel coalescing filter adopting the combination of B- and E-glass fibres to eliminate the acrylic binder and the solvent performs significantly better than the media with the acrylic binders, both in terms of capture efficiency and the quality factor. 171 Increasing the filter area spreads the mist and contaminant loading over more filter fibres to reduce of high mist loadings in private fibres, thus increasing collection efficiency, filter life, and maintenance intervals, and decreases filter force per unit area drop. All of these contribute to increased operation and decreased operating toll.

In addition, both the physical properties of the liquid droplets (density, viscosity, surface tension) and the performance conditions of the filtration procedure such as pressure, temperature, fluid velocity, and humidity all influence the caste to which coalescence occurs, and the fibre selections and structural blueprint of nonwoven coalescing filters need to be engineered in understanding with those system configurations.

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