GB2551014A

GB2551014A - An apparatus and a method for conditioning an exhaust gas

Info

Publication number: GB2551014A
Application number: GB1705356.2A
Authority: GB
Inventors: Macey Lionel
Original assignee: Therm Tech Ltd
Current assignee: Therm Tech Ltd
Priority date: 2016-04-01
Filing date: 2017-04-03
Publication date: 2017-12-06
Anticipated expiration: 2037-04-03
Also published as: GB201705356D0; GB2551014B

Abstract

Apparatus for conditioning exhaust gas, such as those emitted when processing plastics, comprises a conditioning chamber 2 where the gas is contacted with a liquid conditioner comprising condensate derived from condensing the conditioned gas. Chamber 2 comprises gas inlet 3, gas outlet 4, and a conditioner drain 6 connectable to a conditioner inlet 5 via flow-path 10. Conditioned gas from outlet 4 is directed to a condenser 13. Condensate derived from the gas is directed from the condenser 13 to the condensate flow path 10 or conditioner inlet 5 such that the liquid conditioner comprises condensate from the gas. The condenser is preferably a dry electrostatic precipitator and a current-draw monitor produces a signal indicative of reaching a current-draw threshold, which signal may trigger a cycle in which the condenser is cleansed using liquid conditioner supplied via flow path 30. Virgin conditioner may be introduced and waste conditioner may be drained. Conditioner additive may be introduced under the control of a conductivity measuring device 25. The liquid conditioner comprises a plasticiser and a hydrophilic agent preferably diethanolamine. The plasticiser preferably consists of the condensate and comprises phthalates.

Description

AN APPARATUS AND A METHOD FOR CONDITIONING EXHAUST GAS

Technical Field of the Invention

The present invention relates to conditioning exhaust gases and, more particularly, to an apparatus and a method for conditioning an exhaust gas emitted in processing plastics.

Background to the Invention

An electrostatic precipitator (ESP) is a filtration device that separates particles from a flowing gas by passing the gas between pairs of electrodes across which a unidirectional, high-voltage potential is placed. The potential applied can be up to 6000 volts or more. The particles are charged before passing between the electrodes and, when the flowing gas passes between the electrodes, the charged particles migrate to an oppositely charged electrode. Alternatively, the electrodes can comprise a mixture of similarly charged electrodes and earthed electrodes and the charged particles can migrate away from the similarly charged plates until they contact an earthed plate, where they lose their charge and can be collected.

An ESP can be used to effectively remove particles, such as small particles of dust and smoke, from the flowing gas.

In the processing of plastics materials, such as polyvinyl chloride (PVC), exposure to high temperatures, typically in excess of 120°C, is required in a curing phase. This is often conducted in a continuous or batch oven using electric platen heaters, gas platen heaters, high temperature thermal oil radiant heater pipes or by direct fired hot air recirculation.

As part of the processing of PVC, plasticisers are often used as additives to increase the flexibility and/or durability of the material. Common plasticisers used in the processing of PVC include phthalates, such as phthalate esters. During exposure to high temperatures, plasticiser chemicals can be emitted in the form of exhaust fumes, which can be visible as a dense smoke. Plasticiser emissions as part of PVC processing are subject to strict regulation by the Department of the Environment.

An ESP provides an effective means of removing plasticiser fumes and can be utilised in the processing of plastics materials such as PVC. Essentially, the particles in the plasticiser fumes can be electrically charged by passage of the fumes through an electrostatic field. The charged particles can then pass through a series of plates which can alternate between plates having a similar charge to the particles and earthed plates. The charged particles migrate away from the similarly charged plates and contact the earthed plate, at which the particles lose their charge and form a liquid film which runs off the plate into a collector.

An ESP is the most efficient way of removing plasticiser fumes from PVC curing oven exhausts. An ESP has up to 99.9% collection efficiency for particles below sub-micron size and is relatively energy efficient, typically requiring only 40 watts per 1000m3 per hour to achieve the aforementioned collection efficiency. An ESP is an environmentally acceptable energy efficient system for use in the pollution control of PVC processing exhaust fumes.

An ESP used in PVC processing relies on cooling hot oven exhaust gases to a temperature where they form a mist of sub-micron liquid droplets. A typical temperature drop can be from around 120°C to around 40°C. The mist passes through a matrix of ionising wires having an applied voltage of around 10000 volts (DC). The liquid droplets are non-electrically conductive and as they pass through the electronic corona they become electrically charged. The air carrying the sub-micron liquid droplets flows through a collector cell. The collector cell comprises a bank of electrode plates arranged with alternate plates electrically charged up to around 8000 volts (DC) at the same polarity as the ioniser matrix. The uncharged plates located between the charged plates are earthed so that as the liquid droplets pass between the plates they are repelled by the charged plates and land on the earthed plates. Once in contact with the earthed plates, they lose their charge and form a liquid film which runs off as a liquid condensate into a collector tank.

However, an ESP requires a high degree of maintenance. For example, the collector cell and heat exchanger can foul and lose dielectric insulation properties. Depending on the heating process used within the oven, additional contaminants can be present within the plasticiser exhaust gases.

Whilst the ESP system described hereinabove is effective in removing sub-micron droplets of plasticiser emissions, as has been described, it is similarly effective in removing additional contaminants present in the exhaust gases. Contaminants can include water, solid particles of carbon and dust, hydrochloric (HC1) gas, etc. Such contaminants can be present in the ESP and also upstream of the ESP at the stage of exhaust gas cooling referred to hereinabove, which reduces the effectiveness of the cooler.

The contaminants can be detrimental to the long-term effectiveness of the ESP system.

Solid particles of carbon can arise as a result of thermal degradation of organic plasticisers inside the high temperature oven. The presence of carbon is more acute in direct fired ovens where flame impingement can occur.

Water, typically water droplets, can arise from the inspired oven air as a product of combustion or as a by-product of chemical reactions occurring in the plastics curing process.

Both carbon and water droplets are highly electrically conductive and, as a result, can cause a discharge of the electrostatic charges within the ESP system. Further, together with dust particles, they can form a sticky sludge which can build up on the electrode plates. The build-up does not drain off and, eventually, can bridge the gap between the charged and earthed plates, thus rendering the whole cell ineffective without cleaning.

Furthermore, and particular to PVC curing ovens, the thermal degradation of PVC can give rise to HC1 gas. In the presence of water, HC1 gas can reduce the dielectric properties of the condensate. In addition, HC1 in the presence of water can cause some plasticisers to hydrolyse to phthalic acid and the corresponding alcohol. Phthalic acid is insoluble in the liquid condensate and will deposit as a sludge on heat exchanger surfaces, causing a loss in performance.

Phthalic acid is soluble in warm detergent water and, traditionally, this has been used as the method of removal. However, as water is electrically conductive as noted above, such a washing process has had to be performed when the ESP is off-line. The washing process results in an oily water emulsion which must be disposed of and also requires an extended drying time to ensure all water remnants have been removed from the ESP.

Alternatively, components of the ESP can be removed and cleaned off-site. The removal technique is disruptive, time consuming, expensive and can lead to mechanical damage to the system components. Such problems can be cited as reasons for the less widespread use of ESP systems.

The present invention has been developed with the aforementioned problems in mind. Summary of the Invention

According to a first aspect of the present invention, there is provided an apparatus for use with a condenser and for conditioning an exhaust gas, the apparatus comprising: a conditioning chamber, the conditioning chamber comprising a gas inlet, a gas outlet, a conditioner inlet and a conditioner drain; a conditioner flow path connectable to the conditioner drain for directing a liquid conditioner to the conditioner inlet; a conditioned gas flow path connectable to the gas outlet for directing conditioned gas to the condenser; and a condensate flow path connectable to the condenser for directing a condensate to the conditioner flow path and/or the conditioner inlet.

The apparatus of the present invention can be used with, retrofitted with, or incorporated into, an existing processing plant that uses a condenser for gases. For example, the apparatus of the present invention could be incorporated into a processing plant that uses an electrostatic precipitator (ESP) to condense exhaust fumes. The condenser may be an ESP.

The ESP may be a dry-type ESP, referred to herein as a dry ESP. Any reference to an ESP herein may refer to a dry ESP. A dry ESP is preferred to a wet ESP, as wet ESPs are typically larger in size, expensive, produce a large volume of effluent and are very power consuming. A dry ESP is particularly beneficial as it has a significantly lower energy usage than a wet ESP.

According to a second aspect of the present invention, there is provided an apparatus for conditioning an exhaust gas, the apparatus comprising: a conditioning chamber, the conditioning chamber comprising a gas inlet, a gas outlet, a conditioner inlet and a conditioner drain; a conditioner flow path connectable to the conditioner drain for directing a liquid conditioner to the conditioner inlet; a condenser, the condenser comprising a condenser gas inlet and a condensate drain, wherein the condenser is linked to the conditioning chamber via a conditioned gas flow path such that the condenser can receive through the condenser gas inlet a gas discharged from the chamber, and a condensate flow path connectable to the condensate drain for directing a condensate to the conditioner flow path and/or the conditioner inlet.

The apparatus of the second aspect of the present invention can be installed into a new processing plant.

The present invention provides an apparatus whereby a condensate formed from condensing an exhaust gas in a condenser can be introduced into a liquid conditioner flow path and be directed to a conditioning chamber in which it can be utilised to condition subsequent exhaust gas.

An exhaust gas condensed to a condensate in a condenser downstream of a conditioning chamber can be returned to the upstream conditioning chamber to condition subsequent exhaust gas, which can then be condensed in the condenser downstream of the conditioning chamber to a condensate and returned to the upstream conditioning chamber, and so on in a cycle. In this way, the present invention provides an apparatus that can (a) condition exhaust gas, such as that emitted in the curing of plastics, to remove contaminants, (b) meet environmental requirements and regulations by controlling and processing exhaust gas emissions and (c) utilise the condensate obtained by condensing the exhaust gas for conditioning further exhaust gas in a cycle.

The condensate flow path is operable to introduce the condensate into the liquid conditioner flow path and/or the conditioner inlet.

The gas inlet, gas outlet, conditioner inlet and conditioner drain may be arranged such that a gas can pass through the conditioning chamber, wherein the chamber receives the gas through the gas inlet and discharges it through the gas outlet, and a liquid conditioner can counter-flow through the conditioning chamber, wherein the chamber receives the conditioner through the conditioner inlet and discharges the conditioner through the conditioner drain. The gas inlet may be located at a lower point in the conditioning chamber than the gas outlet. The conditioner inlet may be located at a higher point in the conditioning chamber than the conditioner drain.

Passing the liquid conditioner through the chamber counter to the gas flow enables the conditioner to contact the exhaust gas and reduce or remove contaminants present in the exhaust gas. The contaminants can be discharged from the chamber with the liquid conditioner through the conditioner drain.

The reduction or removal of contaminants from the gas in the conditioning chamber significantly reduces the maintenance requirements for apparatus and equipment downstream of the exhaust gas, such as the condenser, and improves the long-term effectiveness of such apparatus and equipment.

Contacting the gas with the liquid conditioner can cool the gas. The gas can be cooled to its dew point. This makes the exhaust gas more suitable for processing in the condenser downstream of the conditioning chamber.

The liquid conditioner discharged from the conditioning chamber may be recycled to the conditioner inlet for repeated use via the conditioner flow path.

Thus, the apparatus may be operable to provide a liquid conditioner cycle. The liquid conditioner cycle may comprise circulating the liquid conditioner discharged through the conditioner drain to the conditioner inlet and counter-flowing the liquid conditioner through the conditioning chamber back to the conditioner drain.

The apparatus may comprise a sump. The liquid conditioner may be collected in the sump.

The sump may be integral to the conditioning chamber. The sump may be located at the base of the conditioning chamber. The conditioner drain may be located at or in the base of the sump.

Alternatively, the sump may be separately connected to the conditioning chamber, such that liquid conditioner may be discharged through the conditioner drain and collected in the sump. The sump may be connected to the conditioner drain.

The liquid conditioner cycle may comprise collecting the liquid conditioner in the sump, discharging the liquid conditioner through the conditioner drain and circulating the liquid conditioner to the conditioner inlet.

The liquid conditioner may be pumped from the conditioner drain to the conditioner inlet. The apparatus may therefore comprise a pump. The pump may be located on the conditioner flow path. The recycling of the liquid conditioner to the conditioner inlet provides a more efficient and cost-effective process.

The conditioning chamber and the condenser may operate in series. The condenser may be an electrostatic precipitator (ESP). The ESP may be a dry ESP. Thus, the condenser may be a dry ESP.

The apparatus of the present invention provides a means of conditioning exhaust gases prior to them entering the condenser, such as an ESP.

When an exhaust gas is processed in an ESP, charged particles in the exhaust gas can contact an earthed plate in the ESP, lose their charge and be collected in the form a liquid condensate.

The apparatus of the present invention provides a condensate flow path which directs the condensate from the condenser into the conditioner flow path and/or the conditioner inlet. The apparatus may introduce the condensate from an ESP into the conditioner flow path, and thus into the liquid conditioner cycle described herein.

The condensate may be introduced at any point in the conditioner flow path. The condensate may be introduced into the conditioner flow path at the conditioner drain, the sump and/or any section of conditioner flow path. Alternatively, the condensate flow path may direct the condensate directly to the conditioner inlet. Further, the condensate can mix with the liquid conditioner and, consequently, be recirculated to the conditioner inlet via the conditioner flow path.

The condensate flow path may direct the condensate to the sump.

The condensate may be circulated from the condenser to the conditioner inlet via the condensate flow path, passed through the conditioning chamber as described herein and then re-circulated in the conditioner flow path as part of the liquid conditioner cycle.

The condensate may derive from plasticiser containing exhaust gas. In such embodiments, the condensate comprises one or more plasticisers. In some embodiments, the condensate will consist essentially of one or more plasticisers.

The liquid conditioner may comprise or consist essentially of the condensate. Alternatively, the liquid conditioner may comprise a mixture of condensate and a virgin conditioner. The virgin conditioner may comprise one or more plasticisers. The virgin conditioner may consist essentially of one or more plasticisers.

The plasticiser in the liquid conditioner may consist essentially of condensate derived from condensing the conditioned gas discharged from the conditioning chamber.

As gas is conditioned in the conditioning chamber and then condensed in the condenser, further condensate is obtained which can be introduced into the conditioner flow path. Thus, the apparatus of the present invention enables the use of a condensate derived from condensing a gas in a condenser, e.g. an ESP, as a conditioner for conditioning a flow of gas upstream of the condenser.

The apparatus of the present invention is particularly effective in conditioning exhaust gas emissions from the curing of a plastics material, more particularly the curing of PVC.

Periodically, it may be necessary to increase or reduce the volume of liquid conditioner and/or replace the liquid conditioner. This can be necessary if the liquid conditioner contains too high a quantity of contaminants removed from the exhaust gas in the conditioning chamber.

The apparatus may therefore comprise a conditioner container. The conditioner container may comprise virgin conditioner. The conditioner container may be linked to the conditioner flow path such that is can introduce virgin conditioner into the conditioner flow path. The conditioner container may be periodically filled with virgin conditioner as desired or as appropriate. The conditioner container may be linked to any point in the conditioner flow path. Alternatively, the conditioner container may be linked to the conditioning chamber, the conditioner inlet and/or the sump.

The apparatus may also comprise a waste conditioner drain. The waste conditioner drain may be linked to the conditioner flow path such that it can remove liquid conditioner from the conditioner flow path. The waste conditioner drain may comprise an outlet for the liquid conditioner that is being removed from the liquid conditioner cycle. The waste conditioner drain may be located at any point in the conditioner flow path.

The apparatus may also comprise an additive container. The additive container may comprise one or more additives as described hereinbelow, e.g. a hydrophilic agent. The additive container may be linked to the conditioner flow path such that it can introduce one or more additives into the conditioner flow path. The additive container may be linked to any point in the conditioner flow path. Alternatively, the additive container may be linked to the conditioning chamber, the conditioner inlet, and/or the sump. The additive container may be periodically filled with additive as desired or as appropriate. The additive container may comprise one or more compartments. Each compartment may contain a different additive.

It has been discovered that the level of contaminants within the liquid conditioner can be monitored by measuring the electrical conductivity of the liquid conditioner. It was found that the higher the concentration of contaminants in the liquid conditioner, the less effective the liquid conditioner will be.

The apparatus of the present invention may comprise a conductivity measuring device for measuring the conductivity of the liquid conditioner.

According to a third aspect of the present invention, there is provided a conductivity measuring device for measuring the conductivity of a liquid conditioner, the conductivity measuring device comprising a first electrode, a second electrode and means for applying a voltage between the first and second electrodes.

The conductivity measuring device is operable to measure the level of contaminants in the liquid conditioner. Generally, virgin conditioner does not conduct electricity. However, as the level of contaminants in the liquid conditioner increases, the resistance reduces. The conductivity measuring device is operable to provide a continual conductivity reading for the liquid conditioner as it flows through the liquid conditioner cycle.

The conductivity measurement device may be located within the conditioner flow path. The first and second electrodes may be fixed a known distance apart within the liquid conditioner flow. When a voltage is applied between the first and second electrodes, the current is measured. If the liquid conditioner comprises a higher concentration of contaminants, such as carbon, the conductance of the liquid conditioner will be higher and, thus, a higher current will be observed. Conversely, if the liquid conditioner comprises a lower concentration of contaminants, the conductance of the liquid conditioner is lower and, thus, a lower current will be observed.

The conductivity measuring device may further comprise a differential amplifier operable to produce a voltage output. The differential amplifier may be integral to the conductivity measuring device. The voltage output may be measured on standard measuring equipment. The differential amplifier may be operable to process the voltage measurement and output a measurement of conductivity for the liquid conditioner.

When the conductivity of the liquid conditioner reaches or exceeds a threshold level, the conductivity measuring device may emit a command signal to the additive container to introduce additive into the conditioner flow path. The command signal may include information concerning the volume and/or type of additive to be introduced into the conditioner flow path. The command signal may be emitted as soon as the threshold conductivity is reached or exceeded. Alternatively, the command signal may be emitted when a conductivity threshold has been reached or exceeded for a set duration of time.

Thus, the conductivity measuring device may monitor and maintain an appropriate conductivity for the liquid conditioner to perform at its optimum. A portion of the conditioning chamber may comprise a stationary phase. The stationary phase may comprise a packing material. The packing material may be any open heat/mass transfer media. The stationary phase may comprise a stainless steel mesh. The stationary phase serves to slow the time it takes for the liquid conditioner to flow through the conditioning chamber and increase the surface area of the liquid conditioner that is exposed to the gas within the conditioning chamber. This increases the likelihood of the gas contacting the liquid conditioner as it passes through the conditioning chamber.

Given the high temperatures of exhaust gas, contacting the liquid conditioner with the exhaust gas may heat the liquid conditioner. As such, the liquid conditioner discharged from the conditioning chamber may be hot. It is important that the liquid conditioner be at a temperature less than its degradation temperature.

The liquid conditioner may be cooled. The liquid conditioner may be cooled in the conditioner flow path.

Thus, the apparatus may further comprise a conditioner cooler. The conditioner cooler may comprise any suitable means for cooling a flow of liquid. For example, the conditioner cooler may comprise a heat recovery exchanger or a circulation cooling system, such as a water cooling system. The conditioner flow path may pass through a water cooling system. The conditioner cooler may be located at any point on the conditioner flow path.

The liquid conditioner comprises one or more additives. The one or more additives are present to treat contaminants in the exhaust gas and/or the liquid conditioner that result from the conditioning of the gas in the conditioning chamber and/or are contained within the condensate. The additive may comprise a hydrophilic agent.

According to a fourth aspect of the present invention, there is provided a liquid conditioner comprising a plasticiser and a hydrophilic agent. The plasticiser may comprise a mixture of plasticisers derived from condensing a conditioned gas discharged from the conditioning chamber and plasticisers present in virgin conditioner.

The addition of a hydrophilic agent to a plasticiser forms a conditioner that can treat contaminants contained therein and also reduce or remove contaminants from an exhaust gas.

The conditioner may be used in the apparatus described herein to reduce or remove contaminants from an exhaust gas emitted in the processing of PVC. The conditioner may be used to reduce or remove contaminants from an exhaust gas emitted in the curing of PVC.

The exhaust gas may contain one or more plasticisers. Such plasticisers are typically used to increase the flexibility and/or durability of a PVC plastics material. As a result, when PVC is cured, the exhaust gas emitted from the curing oven will contain one or more plasticisers. Plasticisers used in the processing of PVC may include phthalates, such as phthalate esters. The one or more plasticisers present in the exhaust gas may be the same as the one or more plasticisers in the virgin conditioner.

The exhaust gas may also contain one or more contaminants. The one or more contaminants may include water, carbon, dust particles, chloride containing compounds such as hydrogen chloride, and mixtures of the same. The nature of the contaminants in the exhaust gas is dependent on the method used to cure the plastics material.

The liquid conditioner as described herein that contacts an exhaust gas can have a four-fold effect on the exhaust gas.

One effect is that the exhaust gas may be cooled by the conditioner. The cooling effect may cool the exhaust gas to its dew point. This is beneficial since the exhaust gas requires cooling in order to form a mist of sub-micron liquid droplets required for processing in an ESP. A second effect is that the conditioner may neutralise chloride containing compounds, such as HC1 gas, present as a contaminant in the exhaust gas. This prevents HC1 in the presence of water causing one or more plasticisers to hydrolyse to phthalic acid and the corresponding alcohol. Beneficially, this can reduce the level of phthalic acid sludge that can deposit on surfaces and cause a loss in performance in a downstream ESP. A third effect is that the conditioner may reduce or remove moisture, such as water, present in the exhaust gas. As noted above, water droplets are highly electrically conductive and, as a result, can cause a discharge of the electrostatic charges within an ESP. Further, together with dust particles, they can form a sticky sludge which can build up on the electrode plates. The build-up does not drain off and, eventually, can bridge the gap between the charged and earthed plates in an ESP, thus rendering the whole cell ineffective without cleaning. A fourth effect is that the conditioner may increase the plasticiser content of the exhaust gas that is discharged through the gas outlet. Such a plasticiser-rich discharge gas may then flow to the condenser, such as an ESP, where it may condense to a condensate. The condensate may then be utilised in the present invention as described herein.

The neutralisation reaction and/or the water absorption may occur in the conditioning chamber, in the sump and/or in the conditioner flow path.

The plasticiser may comprise one or more phthalates. The one or more phthalates may be selected from diisononyl phthalate, dioctyl terephthalate, dioctyl phthalate, diisoctyl phthalate, di-n-octyl phthalate and mixtures of any two or more thereof. The plasticiser may comprise a mixture of diisononyl phthalate and dioctyl terephthalate.

The plasticiser in the liquid conditioner may be obtained from the condensate and/or virgin conditioner.

The plasticiser may be present in an amount of at least around 50wt% of the liquid conditioner. The plasticiser may be present in an amount of at least around 60wt%, at least around 70wt%, at least around 80wt%, at least around 90wt%, at least around 95wt% or at least around 99wt% of the liquid conditioner.

By evaporation following contact with the hot exhaust gases, the plasticiser in the liquid conditioner can increase the plasticiser content of the conditioned gas that is discharged through the gas outlet. Further, it may also raise the partial pressure of the plasticiser and hence its condensation temperature.

The hydrophilic agent may be miscible with the plasticiser.

The hydrophilic agent may be inorganic or organic. The inorganic or organic hydrophilic agents may be miscible with the plasticiser.

The inorganic or organic hydrophilic agent may have a low electrical conductivity.

Preferably, the hydrophilic agent is an organic hydrophilic agent.

The organic hydrophilic agent may be selected from hydroxyethylidene-1,1-diphosphonic acid (HEDP), dibutanolamine, diethanolamine, diethylene glycol, diheptanolamine, dihexanolamine, dimethanolamine, dimethylethanolamine (DMAE/DMEA), dioctanolamine, dipentanolamine, dipropanolamine, erythritol, ethanolamine, ethanolbutanolamine, ethanolpropanolamine, ethyldiethanolamine, ethylene glycol, fructose, glucose, glycerol, glycidol, methanolamine, methanolbutanolamine, methanolethanolamine, methanolpropanolamine, N-ethyldiethanolamine, N-methylethanolamine, pentose, polyethylene glycol, propanolbutanolamine, propylene glycol, ribitol, sucrose, threitol, triethanolamine, triethylene glycol, tripropanolamine, tripropylene glycol, and mixtures of any two or more thereof.

The organic hydrophilic agent may be diethanolamine. Diethanolamine is a liquid at ambient temperature, is miscible with plasticisers, is thermally stable and is commercially available. Moreover, diethanolamine is an organic base, meaning it can neutralise chloride containing compound impurities, and it is hydrophilic, meaning it can absorb water impurity.

The hydrophilic agent may be present in an amount of less than around 10wt% of the liquid conditioner. The hydrophilic agent may be present in an amount of less than around 5wt%, less than around 3wt%, less than around 2wt%, or less than around lwt% of the conditioner. In some embodiments, the hydrophilic agent is present on a ppm scale. In some embodiments, the hydrophilic agent may be present in an amount of around lOppm or less.

In some embodiments, the conditioner may consist essentially of the plasticiser with a relatively minor (ppm) amount of the hydrophilic agent additive.

The hydrophilic agent can have a dual effect on the exhaust gas and/or the conditioner. The hydrophilic agent may be operable to neutralise chloride containing compounds, such hydrochloric gas (HC1 gas), present in the exhaust gas and/or the conditioner. In addition, the hydrophilic agent may also reduce or remove moisture, such as water, present in the exhaust gas and/or the conditioner. The hydrophilic agent may absorb moisture in the exhaust gas and/or the conditioner. Water is immiscible with plasticiser, typically forming droplets or an emulsion. The presence of a hydrophilic agent acts to absorb free water present in the exhaust gas and/or the conditioner and dissolve into the plasticiser, with which the hydrophilic agent is miscible.

Thus, the presence of the hydrophilic agent may have the dual effect of reducing or removing chloride containing compounds and moisture from the exhaust gas and/or the conditioner.

The liquid conditioner may also comprise an inorganic or an organic base. The inorganic or organic base is operable to act as an acidity regulator.

The inorganic or organic base may be miscible with the plasticiser.

The inorganic or organic base may have a low electrical conductivity.

The organic base may be selected from piperidinomethyl polystyrene, 1-(3-dimethylaminopropyl)-3-ethylcarbodiamide, 1,1-dimethylpropylmagnesium chloride, 1,4-diazabicyclo[2.2.2]octane, l,4-diazabicyclo[2.2.2]octane hydrochloride, 1,5-diazabicyclo, l,5-diazabicyclo[4.3.0]non-5-ene, l,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,8- diazabicyclo[5.4.0]undec-7-ene, 2-(2-chloro-6-fluorophenyl)ethylamine hydrochloride, 2-(ethylhexyl)lithium, 2-tert-buty 1-1,1,3,3-tetramethylguanidine, 2,2-dimethylpropylmagnesium chloride, 2,2,6,6-tetramethylpiperidine, 2,6-di-tert-butylpyridine, 2,6-lutidine, 2,6-lutidine purified by re-distillation, 2,6-lutidine purum, 2,6-lutidine reagentplus®, 2,8,9-triisobutyl-2,5,8,9-tetraaza-l-phosphabicyclo[3.3.3]undecane, 2,8,9-triisopropyl-2,5,8,9-tetraaza-l- phosphabicyclo[3,3,3]undecane, 2,8,9-triisopropyl-2,5,8,9-tetraza-1 - phosphabicy clo [3.3.3 ]undecane, 2,8,9-trimethyl-2,5,8,9-tetraaza-1 - phosphabicyclo[3.3.3]undecane, 4-(dimethylamino)pyridine, 9-azajulolidine, ammonia, barium tert-butoxide, benzimidazole, benzyltrimethylammonium hydroxide, butylamine, butylmagnesium, butylmagnesium chloride, choline hydroxide, choline hydroxide solution, dabco® 33-lv, diethanolamine, diethylamine, diethyldimethylammonium hydroxide, diisopropylamine, diisopropylaminomethyl-polystyrene, dimethylamine, ethylamine, ethylamine hydrochloride, ethyllithium, ethylmagnesium bromide, ethylmagnesium chloride, histidine, hexadecyltrimethylammonium hydroxide, hexamethonium hydroxide, hexyllithium solution, hexylmagnesium bromide, hexylmagnesium chloride, imidazole, isobutyllithium, isobutylmagnesium, isobutylmagnesium bromide, isobutylmagnesium chloride, isopropyllithium, isopropylmagnesium, isopropylmagnesium chloride, lithium 2,2,6,6-tetramethylpiperidide 97%, lithium bis(trimethylsilyl)amide, lithium dicyclohexylamide, lithium diethylamide, lithium diisopropylamide, lithium dimethylamide, lithium ethoxide, lithium isopropoxide, lithium methoxide, lithium tert-amoxide, lithium tert-butoxide, lithium triisobutyl(2,2,6,6 tetramethylpiperdino)aluminate, lithium trimethylsilanolate, magnesium bis(diisopropyl)amide, magnesium bis(hexamethyldisilazide), magnesium di-tert-butoxide, magnesium ethoxide, magnesium methoxide, methyl-d3-magnesium iodide, methylamine, methyllithium, methyllithium lithium bromide complex, methyllithium lithium iodide complex, methylmagnesium bromide, methylmagnesium chloride, methylmagnesium iodide, morpholine, morpholinomethyl-polystyrene, n-butyllithium, n-ethyldiisopropylamine, n,n-diisopropyl methylamine, pentylmagnesium bromide, pentylmagnesium chloride, phosphazene, piperazine, piperidine, poly(4-vinylpyridine-co-ethylvinylbenzene), potassium bis(trimethylsilyl)amide, potassium ethoxide, potassium isobutoxide, potassium methoxide, potassium tert-butoxide, potassium tert-pentoxide, potassium trimethylsilanolate, propylamine, propylmagnesium chloride, proton-sponge®, pyridine, sec-butyl lithium, sec- butylmagnesium chloride, sodium amide, sodium bis(trimethylsilyl)amide, sodium ethoxide, sodium methoxide, sodium tert-butoxide, sodium tert-pentoxide, sodium trimethylsilanolate, tert-butylmagnesium chloride, tetraalkylammonium carbonate, tetrabutylammonium ethoxide, tetrabutylammonium hydroxide, tetrabutylammonium methoxide, tetrabutylphosphonium hydroxide, tetrabutylphosphonium malonate, tetraethylammonium hydroxide, tetrakis(decyl)ammonium hydroxide, tetramethylammonium hydroxide, tetraoctylammonium hydroxide, tetrapentylammonium hydroxide, tetrapropylammonium hydroxide, tributylmethylammonium, trimethylamine, triethylmethylammonium hydroxide solution, trimethylphenylammonium hydroxide solution, and mixtures of any two or more thereof. Preferably, the organic base is diethanolamine.

The organic base is present in an amount of less than around 10wt% of the liquid conditioner. The organic base may be present in an amount of less than around 5wt%, less than around 3wt%, less than around 2wt%, or less than around lwt% of the liquid conditioner. In some embodiments, the organic base is present on a ppm scale. In some embodiments, the organic base may be present in an amount of around lOppm or less.

The liquid conditioner may comprise one or more additional additives selected from demulsifiers, viscosity enhancers, antifoaming agents and mixtures of any two or more thereof.

The additional additives may be present in an amount of less than around 10wt% of the conditioner. The additional additives may be present in an amount of less than around 5wt%, less than around 3wt%, less than around 2wt%, or less than around lwt% of the conditioner. In some embodiments, the additional additives are present on a ppm scale. In some embodiments, the additional additives may be present in an amount of around lOppm or less.

The demulsifiers and viscosity enhancers may be selected from ethylene oxide block copolymer, propylene oxide block copolymer, ethyleneglycol, glycidol, hexylamine, pentylamine, polypropylene glycol), sodium dodecyl sulfate (SDS) and mixtures of any two or more thereof.

The antifoaming agent may be selected from polyhydroxy fatty esters, poly ethers, poly amides, silicone oils, silicon glycols, polydimethyl siloxanes, 2-octanol, Antifoam Cl33, Antifoam SAF-105, Antifoam SAF-110, Antifoam SAF-119FG, Antifoam SAF-120, Antifoam SAF-121, Antischiuma FL3, Antitack BTO-7, Baysilone® Antifoam 3099, Byk® -A 501, BYK® A 501, BYK® A 515, BYK® A 550, BYK® A 555, DOW CORNING(R) 1920, DOW CORNING(R) 544 ANTIFOAM COMPOUND, DOW CORNING(R) AF-3258 PULP AID COMPOUND, DOW CORNING(R) ANTIFOAM 1400, DOW CORNING(R) MSA ANTIFOAM COMPOUND, DOW CORNING(R) Q2-3183A ANTIFOAM, DOW CORNING® 1500 ANTIFOAM, Entschaumer L, Hallco® C-451, HDK® H2000, Inovol AF12, Pennwhite Foamdoctor® Compounds, PULPAID(R) 2000 CONCENTRATE, PULP AID (R) 3000 COMPOUND, PULPAID(R) 3056 COMPOUND, T-SIL 10000, Wacker® AK 100 Silicone Fluid, Wacker® AK 1000 Silicone Fluid, Wacker® AK 12500 Silicone Fluid, Wacker® AK 35 Silicone Fluid, and mixtures of any two or more thereof.

According to a fifth aspect of the present invention, there is provided a use of a liquid conditioner as described herein for conditioning an exhaust gas.

The apparatus of the present invention is particularly advantageous in conditioning exhaust gas emissions from the curing of PVC and/or exhaust gases containing HC1. For example, rather than allowing phthalic acid to form on apparatus components and then washing it off as described hereinabove, the conditioning chamber of the present invention can condition the exhaust gas to reduce or remove the HC1 upstream of the condenser, thus removing or reducing the need for washing.

In the conditioning chamber, when the liquid conditioner contacts the exhaust gas, a hydrophilic agent in the liquid conditioner may react with contaminants in the exhaust gas, as described above. The hydrophilic agent in the liquid conditioner effects the neutralisation of chloride containing compounds, such as HC1, and the absorption of water. Water is immiscible with liquid plasticiser and forms droplets or emulsions. The droplets or emulsions can cause disadvantages as mentioned hereinbefore. The hydrophilic agent in the liquid conditioner may absorb free water and effectively dissolve it in the liquid plasticiser with which the hydrophilic agent is miscible.

At least a portion of the liquid conditioner may evaporate upon contact with the exhaust gas. The evaporation typically occurs in the conditioning chamber following contact between the liquid conditioner and the hot exhaust gas, with the exhaust gas heating the liquid conditioner to evaporation. The evaporated conditioner mixes with the exhaust gas flowing through the conditioning chamber and discharged through the gas outlet. Consequently, the evaporated conditioner will flow with the exhaust gas to the condenser.

The evaporated conditioner typically comprises plasticiser as its most abundant component. Where an ESP is located downstream of the conditioning chamber, it has been discovered that it is important to ensure that the plasticiser concentration in the exhaust gas is maintained below a threshold level so as not to overload the current draw on the ESP.

Contaminants such as carbon particles and dust particles may be too small to be removed from the exhaust gas within the conditioning chamber. Such contaminants may therefore migrate through the conditioning chamber with the exhaust gas to the condenser downstream of the conditioning chamber. The contaminants may be deposited in the condenser and may cause a build-up. For example, in an ESP the carbon and dust particles may collect on the electrode plates. It has been discovered that the removal of these contaminants from the condenser may be effected by a wash cycle. The wash cycle may utilise liquid conditioner as described herein.

The wash cycle may wash at least a portion of the condenser.

Where the condenser is an ESP, the wash cycle may wash one or more of the electrode plates of the ESP. This will effectively remove contaminant build-up on the plates. The plates may be washed with the liquid conditioner by any suitable means. For example, the liquid conditioner may be sprayed onto the plates in the ESP.

The ESP may be a modular ESP. The term ‘modular’ is used herein to refer to an ESP which comprises individual portions that can be isolated and individually washed. For example, the modular ESP may comprise individual electrode plates which may be isolated and individually washed in the wash cycle referred to herein. The modular ESP may be a dry modular ESP.

The liquid conditioner used for the wash cycle may be discharged from the condenser through the condensate drain.

The liquid conditioner may be pumped from the conditioning chamber or the sump to the condenser. The apparatus may comprise a wash liquid flow path connectable to the conditioning chamber, the conditioner drain and/or the sump to direct a liquid conditioner to the condenser.

The liquid conditioner may be returned from the condenser to the conditioning chamber or the sump via the condensate flow path.

Thus, the wash cycle may comprise flowing a liquid conditioner from the conditioning chamber or the sump to the condenser for washing at least a portion thereof and then returning the liquid conditioner to the conditioning chamber or the sump.

The liquid conditioner returned to the conditioning chamber or sump from the condenser may be mixed with the liquid conditioner draining from the conditioning chamber. The liquid conditioner returned to the conditioning chamber or sump may be filtered as described hereinbelow.

The wash cycle may be continuous or conducted at regular or irregular intervals.

It has been discovered that the current draw in an ESP is affected by the concentration of contaminants on the electrode plates in the ESP. The inventors have also discovered that the current draw as measured in the ESP is a direct function of the plasticiser concentration in the exhaust gas discharged out of the conditioning chamber to the ESP.

Measuring the current draw thus provides a parameter that can be used to initiate a wash cycle described herein. Generally, the current draw in an ESP increases over time as the concentration of contaminants builds on the electrode plates. The inventors have discovered that washing the plates with liquid conditioner had the effect of returning the current draw to preferable operating levels. It was found that washing the plates with liquid conditioner returned the plates to full use within minutes of the wash completion.

The wash cycle may be programmed to operate at regular or pre-determined time intervals. Additionally or alternatively, the wash cycle may be programmed to operate when a current draw threshold has been reached in the ESP.

The apparatus of the present invention may further comprise a management unit for controlling a wash cycle. The management unit may comprise a current monitoring device operable to measure the current draw in at least one electrode in an ESP and emit an information signal based thereon, a processing unit operable to receive the signal emitted from the current monitoring device, determine whether the current draw has reached a threshold value and, if a threshold value has been reached, output a command signal indicative thereof The processing unit may output a command signal as soon as a threshold value has been reached or exceeded. Alternatively, the processing unit may output a command signal when a threshold value has been reached or exceeded for a set duration of time.

The current monitoring device may continually measure the current draw of at least one electrode in the ESP. Alternatively, the current monitoring device may measure the current draw of at least one electrode in the ESP at regular or irregular intervals. The current monitoring device may comprise an ammeter.

The current monitoring device may continuously emit an information signal or it may emit an information signal at regular or irregular intervals. The information signal may indicate the current draw of the one or more electrodes in the ESP. The information signal may indicate the current draw of all electrodes in the ESP.

The information signal may be communicated to the processing unit by any suitable wired or wireless link. The information signal emitted by the current monitoring device may be an electrical signal or a radio frequency signal.

The processing unit may analyse the information signal received from the current monitoring device and compare it against a stored database of values to determine whether the current draw exceeds a threshold value or not.

In the event that the current draw does not exceed a threshold value, the processing unit may output no command signal. Alternatively, the processing unit may output a command signal for a wash cycle not to be initiated.

In the event that the current draw meets or exceeds a threshold value, the processing unit may output a command signal to initiate a wash cycle. The wash cycle may be as described herein. For example, if a threshold value is reached or exceeded, the processing unit may output a command signal to initiate a wash cycle, whereby liquid conditioner is directed to the condenser via the wash liquid flow path.

Additionally or alternatively, the processing unit may output a command signal to initiate a wash cycle after a pre-programmed duration of time has elapsed and/or at certain pre-set times. Still further, there may be a manual override switch to output a command signal to initiate a wash cycle.

The current draw may be continuously monitored to ensure that it is maintained within acceptable levels. The current draw may vary depending on the type of the ESP. In a multi-cell type ESP, the current draw varies dependent upon where the cell is in the ESP. For example, the cell(s) closer to the inlet of the ESP may be washed more frequently than the cell(s) further away from the inlet.

According to a sixth aspect of the present invention, there is provided a use of a liquid conditioner as described herein for washing a condenser. The condenser may be an electrostatic precipitator.

The liquid conditioner discharged from the conditioning chamber, and/or the liquid conditioner and/or condensate discharged from the condenser may contain contaminant particles as a result of the wash. The contaminant particles may be carbon, dust and the like.

The apparatus may comprise one or more filters suitable for removing contaminant particles from a liquid conditioner.

The one or more filters may be located at any point on the conditioner flow path, the condensate flow path and/or the wash liquid flow path. For example, a filter may be located at the conditioner drain, within the sump, between the sump and the conditioner inlet, between the sump and the conditioner cooler, between the conditioner cooler and the conditioner inlet, between the sump and the condenser, etc. The apparatus may comprise more than one filter.

Alternatively, the one or more filters may be separate to the conditioner flow path, the condensate flow path and/or the wash liquid flow path. In such embodiments, the one or more filters may operate independently of the liquid conditioner cycle. For example, the one or more filters may be connected to the sump and the liquid conditioner may be passed through the one or more filters. The liquid conditioner may be periodically passed through the one or more filters.

It has been discovered that it is advantageous to use a sump comprising separate sections. The sump may comprise two or more sections. The sump may comprise a first and a second section.

The first section may collect liquid conditioner discharged from the conditioning chamber through the conditioner drain. The conditioner flow path may be connectable to the first section to direct liquid conditioner from the first section to the conditioner inlet.

The second section may collect condensate and/or liquid conditioner returned via the condensate flow path. Thus, the second section may contain liquid conditioner comprising a lower degree of contaminants relative to the liquid conditioner in the first section. The condensate flow path may be split to direct condensate and/or liquid conditioner from the condenser to both the first and second sections.

It has been observed that the conditioning chamber can tolerate liquid conditioner which contains contaminant particles such as carbon and dust particles to a greater extent than an ESP. Thus, the filter described herein may only filter the contents of the second section.

The purpose of the one or more filters is to remove contaminant particles from the liquid conditioner, such as dust and carbon. The one or more filters may comprise a filter element. The filter element may be paper based or wood based. The filter element may be made from wood pulp. It has been observed that the wood pulp filter element can remove water moisture from the liquid conditioner in addition to removing particles such as carbon and dust.

According to a seventh aspect of the present invention, there is provided a method for conditioning an exhaust gas, the method comprising the steps of: (a) introducing an exhaust gas through a conditioning chamber, wherein the chamber receives the gas through a gas inlet; (b) contacting the exhaust gas with a liquid conditioner in the conditioning chamber; (c) discharging the conditioned gas through a gas outlet, wherein the liquid conditioner comprises a condensate derived from condensing a conditioned gas.

The method of the present invention may comprise any of the features described for the first to sixth aspects of the present invention.

The liquid conditioner may be introduced into the conditioning chamber through the conditioner inlet and discharged from the chamber through the conditioner drain, whereby the conditioner flows through the conditioning chamber counter to the flow of the exhaust gas.

The method may further comprise the step of flowing the conditioned gas to a condenser, condensing the conditioned gas in the condenser and flowing the condensate back to the conditioning chamber.

The method may further comprise the step of washing the condenser with the liquid conditioner. This may comprise measuring the current draw in an electrostatic precipitator as described herein.

The method may further comprise monitoring the conductivity of the liquid conditioner and introducing additive into the conditioner flow path as described herein.

Detailed Description of the Invention

In order that the invention may be more clearly understood, an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1: is a process flow diagram for an embodiment of the present invention;

Figure 2: is a schematic showing a side view of an apparatus according to an embodiment of the present invention;

Figure 3: is a schematic showing a front view of the apparatus of Figure 2;

Figure 4: is a schematic showing a plan view of the apparatus of Figure 2;

Figure 5: is a graphical representation of the measurement of conditioner conductivity and dosing;

Figure 6: is a graphical representation of the measurement of current draw over time for an ESP comprising an exhaust gas conditioning apparatus.

The following embodiment describes an apparatus of the present invention having an electrostatic precipitator as the condenser. As described herein, in some embodiments of the present invention, the apparatus may be retrofitted into a processing plant already utilising a condenser or electrostatic precipitator to process an exhaust gas. In such circumstances, pipework forming the conditioned gas flow path would be connected to the condenser or electrostatic precipitator such that a flow of conditioned gas discharged from the conditioning chamber can enter the condenser or electrostatic precipitator for processing. Further, the condensate flow path would be connected to the condenser or electrostatic precipitator such that the condensate collected in the condenser or electrostatic precipitator can flow back to the sump or conditioning chamber.

Referring to Figures 1 to 4, there is shown an apparatus 1 comprising a conditioning chamber 2. The conditioning chamber 2 comprises a gas inlet 3, a gas outlet 4, a conditioner inlet 5 and a conditioner drain 6. The conditioning chamber 2 further comprises a stationary phase 7, a sump 8 and spray nozzles 9.

An exhaust gas emitted from a curing oven or similar used in processing a plastics material will be introduced into the conditioning chamber 2 through the gas inlet 3. The exhaust gas will contain one or more plasticisers and contaminants such as HC1 gas, carbon particles, dust particles, and water.

When the exhaust gas enters the conditioning chamber 2, it will be hot. The exhaust gas passes through the conditioning chamber 2, through a stationary phase comprising a packing material 7 and out the gas outlet 4. The packing material 7 serves to slow the time it takes for the liquid conditioner to flow through the conditioning chamber 2 and increases the surface area of the liquid conditioner that is exposed to the gas within the conditioning chamber 2. A liquid conditioner is introduced into the conditioning chamber 2 through the conditioner inlet 5 and sprayed into the conditioning chamber 2 through the spray nozzles 9. The liquid conditioner will then cascade down the conditioning chamber 2, over the packing material 7 and be collected in the sump 8.

In the conditioning chamber 2, as the liquid conditioner cascades down the conditioning chamber 2, it contacts the exhaust gas passing through the chamber 2 from the inlet 3 to the outlet 4. Upon contact, the conditioner will cool the exhaust gas to its dew point, which converts it into a mist of sub-micron liquid droplets making it suitable for processing in an electrostatic precipitator. At the same time, a volume of the liquid conditioner will be heated to a degree sufficient to cause it to evaporate within the chamber 2. This will have the effect of increasing the plasticiser content of the conditioned gas discharged from the conditioning chamber 2. A conditioner drain 6 is located in the base of the sump 8. The conditioner drain 6 is connected to the conditioner inlet 5 via the conditioner flow path 10. The flow path 10 comprises pipework connecting the drain 6 to the inlet 5. Thus, a loop is created whereby liquid conditioner can flow through the conditioning chamber 2, into the sump 8, be discharged through the drain 6 and returned to the conditioner inlet 5. A pump 11 is utilised to pump the liquid conditioner from the conditioner drain 6 to conditioner inlet 5.

The conditioner flow path 10 comprises a conditioner container 17. The conditioner container 17 contains virgin liquid conditioner that can be introduced into the conditioner flow path 10. The virgin conditioner consists essentially of one or more plasticisers.

The conditioner flow path 10 also comprises a waste conditioner drain 18 so that liquid conditioner can be removed from the conditioner flow path 10 and passed through to a conditioner tank 19. The waste conditioner drain 18 can be controlled by a valve 20 and valve controller 21.

The presence of an additive in the liquid conditioner serves to neutralise chloride containing contaminants, such as HC1, present in the conditioner and also absorb water. The neutralisation and absorption reactions can occur in the conditioning chamber 2, the sump 8, or any point in the conditioner flow path 10. The liquid conditioner will periodically require dosing with additive to ensure that the neutralisation and absorption reactions occur as required.

An additive container 22 is connected to the conditioner flow path 10 by pipework 23. As required, additive can be introduced into the conditioner flow path 10 from the additive container 22 using a pump 24.

The dosing of the liquid conditioner with additive is automated and controlled by a conductivity measuring device 25. The conductivity measuring device 25 has two electrodes (not shown) positioned in the liquid conditioner flowing through the conditioner flow path 10. A voltage is applied between the two electrodes and the current is measured. The conductivity measuring device 25 has a differential amplifier (not shown) that processes the voltage measurement and outputs a measurement of conductivity for the liquid conditioner flowing through the conditioner flow path 10. It has been discovered that the higher the conductivity reading; the higher the concentration of contaminants in the liquid conditioner. Thus, conductivity measuring device 25 is operable to emit a command signal to the additive container 23 to introduce one or more additives into the conditioner flow path 10. The command signal will specify the volume and/or type of additive required to treat the contaminants in the liquid conditioner and thus lower the conductivity of the liquid conditioner. The additive container 22 therefore comprises a processor (not show) operable to receive command signals of the type emitted by the conductivity measuring device 25 and instruct the additive container 22 and the pump 24 to introduce additive into the conditioner flow path 10.

Referring to Figure 5, there is shown a graph of conditioner conductivity versus time. The graph shows the effect of dosing a liquid conditioner with an additive. Where the liquid conditioner contains a dosing of additive, the conductivity is relatively low, shown as below 6Sm"', After a time, the effect of the additive will reduce as the volume of it capable of neutralising HC1 and absorbing water reduces, such that the conductivity of the liquid conditioner increases to around 140 Sm"1. Once an additive dosing is triggered, the conductivity of the liquid conditioner will drop again whilst the dosing is being conducted and return to below 6Sm_1. Thus, the conductivity measuring device 25 can monitor and maintain a suitable level of additive in the liquid conditioner for the contaminants present therein.

The liquid conditioner in the conditioner flow path 10 will be hot due to its contact with hot exhaust gas. To cool the liquid conditioner, the conditioner flow path 10 passes through a conditioner cooler 26. The conditioner cooler 26 comprises a water flow path 27 in which cold water as the cooling medium flows counter to the direction of flow of the liquid conditioner in the conditioner flow path 10. The water flow in the water flow path 27 can be controlled by valve 28 and valve controller 29. The conditioner cooler 26 ensures the liquid conditioner is at an appropriate temperature before entry into the conditioning chamber 2.

The apparatus 1 further comprises a conditioned gas flow path 12 along which the conditioned gas discharged from the conditioning chamber flows to an electrostatic precipitator 13. Electrostatic precipitator 13 may be a dry electrostatic precipitator. The flow path 12 comprises pipework connecting the outlet 4 with a conditioned gas inlet 14. The electrostatic precipitator 13 comprises a condensate drain 15. A condensate collected in the electrostatic precipitator 13 is discharged through the condensate drain 15 and returned in to the sump 8 along the condensate flow path 16. The condensate flow path 16 comprises pipework connecting the condensate drain 15 with the sump 8.

The conditioned gas will flow down the pipework of the conditioned gas flow path 12 to the electrostatic precipitator 13 and be introduced through the conditioner gas inlet 14. Inside the electrostatic precipitator 13, the mist of liquid droplets of the conditioned gas will be electrically charged and pass over a bank of electrode plates which alternate between plates having the same charge as the liquid droplets and earthed plates. As the liquid droplets pass over the plates, they are repelled by the charged plates and land on the earthed plates. Upon contact with the earthed plates, the liquid droplets lose their charge and form a liquid condensate which is collected in the base of the electrostatic precipitator 13. The condensate collected consists essentially of plasticiser which was contained within the exhaust gas. The conditioned gas following removal of the plasticiser and other contaminant particles may be discharged from electrostatic precipitator through an outlet 38.

The condensate is discharged from the electrostatic precipitator 13 through the condensate drain 15 and flows along the pipework of the condensate flow path 16 back to the sump 8. In the sump 8, the condensate will mix with the liquid conditioner that has cascaded down through the conditioning chamber 2. The mixture is discharged from the sump 8 through the conditioner drain 6 and pumped back to the conditioner inlet 5 for repeat use to condition subsequent exhaust gas passing through the conditioning chamber 2. Thus, the liquid conditioner comprises a mixture of virgin liquid conditioner, condensate and additive.

The conditioned gas discharged from the conditioning chamber 2 can contain residual contaminants, such as carbon particles and dust particles, which are too small to be removed in the conditioning chamber 2. The conditioned gas flows to the electrostatic precipitator 13 along conditioned gas flow path 12 to the conditioned gas inlet 14. Inside the electrostatic precipitator 13, the contaminant particles can be collected on the electrodes and cause a build-up that can lead to operating problems. For example, over time the build-up can result in at least two electrode plates in the electrostatic precipitator 13 bridging. This can render the electrostatic precipitator 13 ineffective. The build-up is removed by washing the appropriate components of the electrostatic precipitator 13. The apparatus 1 utilises the liquid conditioner to wash the electrodes of the electrostatic precipitator 13.

In particular, a wash liquid flow path 30 allows liquid conditioner to flow from the sump 8 out through the drain 6’ to the electrostatic precipitator 13. The wash liquid flow path 30 includes a pump 31 for pumping the liquid conditioner to the electrostatic precipitator 13. The introduction of the liquid conditioner into the electrostatic precipitator 13 is controlled by valve 31 and valve controller 32. Inside the electrostatic precipitator 13, the liquid conditioner is sprayed onto the one or more electrodes (not shown) through spray nozzles 33 to clean off the build-up of contaminant particles, such as carbon and dust. The liquid conditioner used in the wash cycle will be collected in the electrostatic precipitator 13 and discharged through the condensate drain 15. As such, the liquid conditioner mixes with the condensate obtained from condensing the exhaust gas and is directed back to the sump 8 along the condensate flow path 16.

The electrostatic precipitator 13 further comprises a management unit 34. By monitoring the current draw in the electrostatic precipitator with the management unit 34, it can be determined when the electrode plates require washing. As described, a wash cycle can be initiated, whereby liquid conditioner in the sump 8 can be discharged through the conditioner drain 6’ and pumped along the pipework of the wash liquid flow path 30 to the electrostatic precipitator 13 using pump 31.

The management unit 34 comprises a current monitoring device (not shown) for measuring and monitoring the current draw on one or more electrodes in the electrostatic precipitator 13. The current monitoring device comprises an ammeter (not shown) and a transmitter for emitting an information signal indicating the current draw on the one or more electrodes.

The management unit 34 further comprises a processing unit (not shown). The processing unit comprises a transmitter and a receiver such that is can receive the information signal emitted by the current monitoring device, determine whether the current draw has reached a threshold value and, if so, output a command signal. The command signal can contain instructions for the pump 31 to initiate a wash cycle by directing liquid conditioner from the sump 8 to the electrostatic precipitator 13 as described.

The benefits of conducting a wash cycle using a liquid conditioner of the present invention are shown in Figure 6. The graph measures the cell power draw within an electrostatic precipitator versus time. After each 24hr period, a wash cycle was conducted. For first wash cycle after 24hrs was conducted without the liquid conditioner of the present invention and the wash cycles after two days, three days and after four days were conducted with the liquid conditioner of the present invention. As can be seen, using the liquid conditioner in the wash cycle had the effect of significantly reducing the cell power draw in the electrostatic precipitator.

In washing the electrodes in the electrostatic precipitator 13, the liquid conditioner used for the wash will contain contaminants that had built-up on the surface of the electrodes. The contaminants typically comprise carbon and dust particles. The liquid conditioner is discharged from the electrostatic precipitator 13 through the condensate drain 15 and flows back to the sump via the condensate flow path 16. Thus, the liquid conditioner used in the wash is mixed with the condensate collected from the condensing of the exhaust gas in the electrostatic precipitator. It is desirable to remove the contaminant particles from the liquid conditioner. This is achieved using a filter 35.

The apparatus 1 comprises a filter 35 and pump 36 as components in pipework 37 that defines a loop, which allows liquid conditioner in the sump 8 to flow out through the conditioner drain 6” to the filter 35 and back to the sump 8.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS:

1. An apparatus for use with a condenser and for conditioning an exhaust gas, the apparatus comprising: a conditioning chamber, the conditioning chamber comprising a gas inlet, a gas outlet, a conditioner inlet and a conditioner drain; a conditioner flow path connectable to the conditioner drain for directing a liquid conditioner to the conditioner inlet; a conditioned gas flow path connectable to the gas outlet for directing conditioned gas to the condenser; and a condensate flow path connectable to the condenser for directing a condensate to the conditioner flow path and/or the conditioner inlet.

2. An apparatus for conditioning an exhaust gas, the apparatus comprising: a conditioning chamber, the conditioning chamber comprising a gas inlet, a gas outlet, a conditioner inlet and a conditioner drain; a conditioner flow path connectable to the conditioner drain for directing a liquid conditioner to the conditioner inlet; a condenser, the condenser comprising a condenser gas inlet and a condensate drain, wherein the condenser is linked to the conditioning chamber via a conditioned gas flow path such that the condenser can receive through the condenser gas inlet a gas discharged from the chamber, and a condensate flow path connectable to the condensate drain for directing a condensate to the conditioner flow path and/or the conditioner inlet.

3. An apparatus as claimed in claim 1 or claim 2, wherein the condenser is a dry electrostatic precipitator.

4. An apparatus as claimed in any preceding claim, wherein the gas inlet, gas outlet, conditioner inlet and conditioner drain are arranged such that the exhaust gas can pass through the conditioning chamber, wherein the chamber receives the gas through the gas inlet and discharges it through the gas outlet, and a liquid conditioner can counter-flow through the conditioning chamber, wherein the chamber received the conditioner through the conditioner inlet and discharges it through the conditioner drain.

5. An apparatus as claimed in any preceding claim, further comprising a sump.

6. An apparatus as claimed in claim 5, wherein the sump is located at the base of the conditioning chamber and the conditioner drain is located at or in the base of the sump.

7. An apparatus as claimed in claim 5 or claim 6, wherein the condensate flow path directs the condensate to the sump.

8. An apparatus as claimed in any preceding claim, further comprising a conditioner container linked to the conditioner flow path such that it can introduce virgin liquid conditioner into the conditioner flow path.

9. An apparatus as claimed in any preceding claim, further comprising a waste conditioner drain linked to the conditioner flow path such that is can remove liquid conditioner from the conditioner flow path.

10. An apparatus as claimed in any preceding claim, further comprising an additive container linked to the conditioner flow path such that it can introduce one or more additives into the conditioner flow path.

11. An apparatus as claimed in any preceding claim, further comprising a conductivity measuring device for measuring the conductivity of a liquid conditioner.

12. An apparatus as claimed in claim 11, wherein the conductivity measuring device comprises a first electrode and a second electrode and a means for applying a voltage between the first and second electrodes.

13. An apparatus as claimed in claim 11 or claim 12, wherein the conductivity measuring device comprises a differential amplifier operable to process a voltage measurement and output a measurement of conductivity for the liquid conditioner.

14. An apparatus as claimed in claim 13, wherein the conductivity measuring device is operable to emit a command signal to an additive container to introduce additive into the conditioner flow path when the conductivity of the liquid conditioner reaches or exceeds a threshold level.

15. An apparatus as claimed in any preceding claim, wherein the conditioning chamber comprises a stationary phase comprising a packing material.

16. An apparatus as claimed in any preceding claim, further comprising a conditioner cooler located on the conditioner flow path.

17. An apparatus as claimed in any preceding claim, further comprising a wash liquid flow path connectable to the conditioning chamber, the conditioner drain and/or the sump for directing a liquid conditioner to the condenser.

18. An apparatus as claimed in claim 17, wherein the condenser is an electrostatic precipitator and the apparatus further comprises a management unit, the management unit comprising a current monitoring device operable to measure the current draw in at least one electrode in the electrostatic precipitator and emit an information signal based thereon, a processing unit operable to receive the signal emitted from the current monitoring device, determine whether the current draw has reached a threshold value and, if a threshold value has been reached, output a command signal indicative thereof.

19. An apparatus as claimed in any preceding claim, further comprising one or more filters for removing contaminant particles from a liquid conditioner.

20. A method for conditioning an exhaust gas, the method comprising the steps of: (a) introducing an exhaust gas into a conditioning chamber, wherein the chamber receives the gas through a gas inlet; (b) contacting the exhaust gas with a liquid conditioner in the conditioning chamber, and (c) discharging the conditioned gas through a gas outlet, wherein the liquid conditioner comprises a condensate derived from condensing a conditioned gas.

21. A method as claimed in claim 20, wherein the liquid conditioner is introduced into the conditioning chamber through a conditioner inlet and discharged from the chamber through a conditioner drain, whereby the conditioner flows through the conditioning chamber counter to the flow of the exhaust gas.

22. A method as claimed in claim 21, wherein the method comprises a liquid conditioner cycle, the cycle comprising circulating the liquid conditioner discharged from the chamber through the conditioner drain to the conditioner inlet and counter-flowing the liquid conditioner through the conditioning chamber back to the conditioner drain.

23. A method as claimed in any one of claims 20-22, wherein the method further comprises the step of flowing the conditioned gas to a condenser, condensing the conditioned gas in the condenser and flowing the condensate back to the conditioning chamber, wherein the condenser is a dry electrostatic precipitator.

24. A method as claimed in any one of claims 20-23, wherein the liquid conditioner is as claimed in claims 26-30.

25. A method as claimed in claim 23 or claim 24, wherein the method further comprises the step of washing the condenser with the liquid conditioner.

26. A liquid conditioner comprising a plasticiser and a hydrophilic agent.

27. A liquid conditioner as claimed in claim 26, wherein the plasticiser is derived from condensing a conditioned gas.

28. A liquid conditioner as claimed in claim 26 or claim 27, wherein the plasticiser consists essentially of a condensate derived from condensing a conditioned gas.

29. A liquid conditioner as claimed in any one of claims 26-28, wherein the plasticiser comprises one or more phthalates.

30. A liquid conditioner as claimed in any one of claims 26-29, wherein the hydrophilic agent is diethanolamine.

31. Use of a liquid conditioner as claimed in any one of claims 26-30 for conditioning an exhaust gas.

32. Use of a liquid conditioner as claimed in any one of claims 26-30 for washing a condenser.