GB2310386A

GB2310386A - Treating exhaust gases

Info

Publication number: GB2310386A
Application number: GB9603852A
Authority: GB
Inventors: Frederick Allen
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-02-23
Filing date: 1996-02-23
Publication date: 1997-08-27
Also published as: GB2310386A8; GB9603852D0; GB2310386A9

Abstract

A treating device comprises a series of absorbent discs or flat cylinders 1, each bearing spacing projections 5. The set may be formed as component which is held together so that it may be removed as one. The active chemicals may be calcium chloride or slaked lime, which act as drying agents, with the lime also serving to remove NOx. Activated carbon also acts to absorb noxious gases.

Description

Improvements m or relating to means for reducing air pollution by noxious gases The present invention relates to a means and method for absorption of noxious gases arising from the exhaust of an internal combustion engine in particular but relates also to any discharge of gaseous products into the atmosphere from industrial and chemical processes. Perhaps the greatest need at the moment, having regard to the Public concern about pollution produced by vehicle exhausts, is for a simple low cost means for the absorption of noxious gases issuing from such exhausts. Such means require to be low cost and efficient for a reasonable mileage before being serviced or exchanged.Thus the invention relates to a means for reducing pollutants which can be removed when saturated in a similar way that other items of vehicle equipment, namely spark plugs, brake linings and exhaust silencers etc. are dealt with at service intervals.Alternatively instead of replacement the service may be to clean the absorption material.The invention may also include means to delay saturation or blockage and extend the period of use of the anti-pollutant means before replacement or out of vehicle cleansing is required The anti-pollution means according to the present invention also relates to an exhaust cleansing system which may incorporate features for extending its useful life before unacceptable saturation or blockage occurs but also provides for cleansing and replacement of any elements used in the system The key components of emissions from internal combustion engines which are required to be controlled in accordance with certain International and specific National and Regional Standards are namely, Hydrocarbons (unburnt fusel), NO N02 and N03 (known collectively as NOX), Carbon Monoxide, Carbon Dioxide and soot("Carbon particulates").All these pollutants are emitted from Diesel Engines and all except "Carbon particulates" are emitted from Petrol engines and vary in quantity according to the efficiency of the combustion process within these engines.

In addressing the problem of controlling emission of the foregoing pollutants the following points have been considered in relation to the individual pollutants.

Whilst enormous improvements have been made in their control through improved combustion chamber design, computerised fuel injection systems, electronic ignition systems and improved fuel burning characteristics etc. hydrocarbons are still present in quantities of up to 1% Maximum of total emitted gases under certain critical engine conditions and of course as engine wear takes place or lacks proper servicing the problem is exacerbated.

NO,N02 and N03 are formed by the combination of Nitrogen and Oxygen during the combustion process due to the elevated temperatures which are obtained and are essential for optimum efficiency and engine power. Although NOX quantities are small in percentage terms they are relatively stable and are not easily reversed into Nitrogen and Oxygen. When emitted from an engine to the atmosphere they combine with water forming Nitric Acids which are highly detrimental to plant life and the general environment. NOX is perhaps the most hostile emission and also is the most difficult to control particularly in the case of Diesel engines where the quantity generated is much higher than from Petrol engines due to the very high temperatures of combustion inherrent in Diesel engines.

CO arises and appears in the emissions as not more than 5% by volume of the emission gases being caused by poor combustion and of course is a danger to all forms of life.

Ironically C02 is the result of good combustion and being inert is not easy to combat and therefore the approach has been to reduce its potential as an emission by introducing control standards on overall fuel consumption per unit of power. For example in U.S.A. all engines are required to produce optimum fuel consumption on a mileage per gallon basis according to engine capacity. Its control is part of the battle against the "greenhouse effect".

The emission of soot (Carbon Particulates) is peculiar to Diesel engines and is a major problem in this type of engine.Whilst it can be reduced by increasing the combustion temperatures this causes a reduction in engine life.

In addition to the various improvements which have been achieved and are ongoing in respect of improved combustion in the engine, Catalytic converters have been developed to deal with the residual unwanted emissions from Petrol engines. These converters comprise high surface areas of semi-refractory cores coated with catalytic elements such as Platinum and Rhodium thereby making them very expensive but nevertheless they are widely used and now have life expectancy of up to 100,000 miles. They require to operate at 420 degrees Centigrade minimum to achieve best effects.

In the case of Diesel engines, emissions have been tackled in a similar way in principle as those in Petrol engines in regard to the actual combustion process using computer controlled injection and high combustion temperatures etc. but NOX and Carbon particulates (Soot) remain as big problems.

Exhaust gases characteristics are hostile to their escape route structure and treatment in that they are very hot (1000 C+) initially, vary in speed from 50 m/sec down to 5 m/sec according to engine speed with associated volumes according to the engine capacity. Additionally the gases comprise substances which require different treatments in order to comply with regulations.

An additional complication in designing an exhaust and anti-emission system arises from the complex back pressure effects which are created by any structures installed in an exhaust system. Such back pressures can seriously effect engine performance unless they are controlled by design of the system. An ideal maximum back pressure of 10" WG is required Against the foregoing background the invention is particularly concerned with filtering or scrubbing exhaust gases in a system which maintains an acceptable efficiency over a realistic mileage and not as has been experienced with other proposals which have been merely sufficient for a short period of use in order to pass some test procedure after which these systems become rapidly ineffective.

The anti-pollutant system according to the present invention it is believed will overcome the shortcomings of similar prior proposals by careful selection of the chemicals incorporated in the filtration elements and by designing elements which do not produce unacceptable back pressure in an exhaust pipe to which, or in which, the system is placed and will provide a high surface area of anti-pollutant elements so that the exhaust gases are adequately and efficiently exposed to the chemicals of the elements whereby efficient absorption of noxious gases takes place 1 without rapidly blocking or causing back pressure problems in the exhaust or silencer system whilst providing easy replacement or cleansing of the elements at service intervals.

An object of the invention is to provide an anti-pollution system which is simple and low cost and is suitable for original equipment and retrofitting to existing vehicles having regard to the fact that both Petrol and Diesel engines' exhausts need to be treated and that the system will need to be readily adaptable without redesign for different sizes and characteristics of engine.An anti-pollution system for treating the out flow of noxious gases according to the invention includes a stack of substantially circular biscuits, the said biscuits having apertures therethrough, means to position the said stack of biscuits in a pipe connected to a gas producer in such a way that exhaust gases flow through the apertures of the said stack of biscuits from the producer before entering the atmosphere from the pipe exit, the relative disposition and size of the apertures being selected and arranged so as to satisfy the back pressure conditions required for the efficient operation of the said producer the biscuits together or singly containing a range of chemical compounds so that the outflow of (a) unburnt fuel droplets (b) a mixture of NO, N02 and N03, (c) Carbon Monoxide and Carbon Dioxide are all reduced to acceptable levels. The stack of biscuits is preferably held in a cassette located so as to be readily removable from the pipe and to enable ready replacement or cleansing of biscuits at service intervals.

The chemical compound constituent of each biscuit in the stack may vary in such a way that the exhaust gases pass sequentially through a series of biscuits of different chemical composition selected to cleanse the flow of gases into the atmosphere some biscuits being appropriate for the absorption of a particular noxious gas while other biscuits cater for the absorption of a different noxious gas Alternatively the biscuits may be identical in the chemical compounds they contain but contain a mixture of appropriate chemical compounds. Anhydrous CaCk and/or CaO may be used as a drying agent, Slaked lime may be used as a neutralising agent and Activated carbon may be used to absorb gases.

Conveniently the biscuits may be circular or annular in shape and have projections on their flat surfaces so as to space the biscuits apart and so that the assembled stack may produce a series of chambers to enable the noxious gases to react as fully as possible with the chemical compounds while keeping the increase of back pressure within acceptable limits.

The biscuits may be stacked in a cassette of cylindrical shape which is split horizontally or may have a removable end flange to enable some or all of the biscuits to be changed or cleansed at service intervals. The cylindrical cassette is inserted into an exhaust system adapted to receive the cassette at some selected position along its length and may replace existing "silencer" systems which are generally located under vehicles.

In the case of a stack of biscuits of the same chemical composition the biscuits may incorporate or be formed around reinforcing wires or rods made of a material to further combine or accept on their surfaces pollutants contained in the flow of gases before their exit into the atmosphere. The reinforcing wires or rods may be formed alternatively as cages surrounding the biscuits for ease of handling, replacement and disposal.

Typical examples of such appropriate chemicals / chemical compounds and their functions and purpose are illustrated in the following table: pURPOSE FUNCTION CHEMICALS Drying agent. Remove free moisture from effluent -Anhydrous CaCl2 gases. -CaO Neutralising agent. Combine with acidic constituents of -Slaked lime effluent gases.

Absorption. Absorb gases from the effluent gases. -Activated Carbon NOTE: Other chemicals and chemical compounds will be incorporated also.

Examples of chemical reactions which occur in the system are shown in the following formulae:- & CaO + H 2 0 = Ca(OH) 2. B,Ca(OH)2 + CO 2 = Ca CO 3 The invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1. shows a mould and typical cross section of a biscuit.

Figure 2. shows a cross section of a biscuit having projections to provide a gap between otherwise adjacent spacers.

Figure 3. shows a cross section of a cassette or biscuit container in which the biscuits are contained in a wire cage.

Figure 4. shows a longitudinal cross section of an engine exhaust including a container or cassette with biscuits in position.

Figure 5. shows diagramatically a cassette or container for the biscuits which can be opened by releasing the flanges to enable biscuits to be inserted or removed and an open wire net in which the biscuits may be retained so that a stack of biscuits may be readily inserted to the container or removed therefrom.

Figure 6. shows diagramatically a cassette or container for the biscuits which can be opened by releasing the endwise flange to enable biscuits to be inserted or removed and an open wire net in which the biscuits may be retained so that a stack of biscuits may be readily inserted to the container or removed therefrom.

As shown in Figure 1. a biscuit 1. moulded by a moulding tool 3. is shown in cross section. Apertures 2. are shown along several radii. Also shown in Figure 1. is a typical moulding tool 3. shown in diametral section indicating the cores 4.which form the apertures 2.

Figure 2. shows both in cross section and end elevation integral projections 5.

Figure 3. shows a longitudinal cross section of a number of biscuits 1. being spaced apart by the integral projections 5. in a wire cage 6.

Figure 4. shows a longitudinal cross section of a canister 7. containing two wire cages 6. arranged in series. An inlet and outlet pipe is shown diagramatically at 8 and 9.

Figure 5. shows a canister 10. split and flanged longitudinally at 11. and 12. which contains the biscuits held in wire cages 6.

Figure 6. shows an alternative canister 13. having an end flanged cap 14. containing the biscuits held in wire cages 6.

"Improvements in or relating to means for reducing air pollyution by noxious gases" KEY to Drawing references.

Drawing Item ref: Item description.

Reference Fig. 1 "A" Drawing title - "A moulding tool and biscuit".

"B" Moulding tool - a diametral section.

"C" Biscuit.

Biscuit.

2. Apertures.

3. Moulding tool.

4. Cores.

Fig.2 "D" Drawing title - "Biscuit with integral projections" 5. Integral projections.

Fig.3 "E" Drawing title - "Partial longitudinal view of biscuits with integral projections mounted in a cylindrical wire cage." 6. Wire cage.

1. Biscuits 5. Integral projections.

Fig.4 "F" Drawing title - "Longitudinal section of cylindrical canister containing two cassettes of biscuits.

6. Two wire cages.

7. Canister.

8. Inlet pipe.

9. Outlet pipe.

Fig.5 "G" Drawing title - "Pictorial view of canister with longitudinal flanges to facilitate replacement of biscuit cassettes." 10. Canister.; 11 & 12 Canister longitudinal flanges.

Fig.6 "H" Drawing title - "Longitudinal section of cylindrical canister with endwise flange." 13. Alternative canister.

14. End flanged cap.

6. Two wire cages Fig. 1 - Fig.6 "X" Date - January 24th 1996 (Inclusive) "Y" Name and address of Applicant.

F.Allen Esq. B.Sc.C.Eng.F.Inst.E.

c/o Ambleside, Hellidon, Nr Daventry, Northants, NNl 1 6LG.

"Z" Copyright.

Claims

,xAIMS.

IL An anti-pollution system for treating the outflow of noxious gases includes a stack of substantially circular biscuits, the said biscuits having apertures therethrough, means to position the said stack of biscuits in a pipe connected to a gas producer in such a way that exhaust gases flow through the apertures of the said biscuits from the producer before entering the atmoshere from the pipe exit, the relative disposition and size of the apertures being selected and arranged so as to satisfy the back pressure conditions required for the efficient operation of the said producer the biscuits together or singly containing a range of chemical compounds so that the outflow of (a) unburnt fuel droplets (b) a mixture of NO,N02 and N03, (c) Carbon Monoxide and Carbon Dioxide are all reduced to acceptable levels.
2. An anti-pollution system for treating the outflow of noxious gases as claimed in claim 1 in which the stack of biscuits is held in a cassette located so as to be readily removable from the pipe and to enable ready replacement or cleansing of biscuits at service intervals.
3. An anti-pollution system for treating the outflow of noxious gases as claimed in claims 1 and 2 in which the chemical compound constituent of each biscuit in the stack may vary in such a way that the exhaust gases pass sequentially through a series of biscuits of different chemical composition selected to cleanse the flow of gases into the atmosphere some biscuits being appropriate for the absorption of a particular noxious gas while other biscuits cater for the absorption of a different noxious gas.
4. An anti-pollution system for treating the outflow of noxious gases as claimed in claims 1 and 2 in which the biscuits are identical but contain a mixture of appropriate chemical compounds.
5LAn at anti-pollution system for treating the outflow of noxious gases as claimed in any of the preceding claims in which the biscuits include anhydrous CaC12 and or CaO as a drying agent, slaked lime as a neutralising agent and activated carbon as a gas absorber.
6. An anti-pollution system for treating the outflow of noxious gases as claimed in any of claims 1,2,4 and 5 in which the biscuits are arranged sequentially in the order of drying, neutralising and absorption.
7. An anti-pollution system for treating the outflow of noxious gases as claimed in any preceding claim in which the biscuits are arranged to be replaceable in the cassette by replacement biscuits or cleansed biscuits.
8. An anti-pollution system for treating the outflow of noxious gases as claimed in claim 7 in which the cassette is in the form of a split cylinder to enable the biscuits to be held together and the cassette is adapted to be readily insertable upstream of the outflow.
9. An anti-pollution system for treating the outflow of noxious gases as claimed in claim 7 in which the cassette is in the form of a cylinder with a removable end flange to enable the biscuits to be held together and the cassette is adapted to be readily inserted upstream of the outflow.
tO. An anti-pollution system for treating the outflow of noxious gases as claimed in any of the claims 1-8 in which the chemical compounds are compressed and/or sintered to form a compacted biscuit.
IL An anti-pollution system for treating the outflow of noxious gases as claimed in claim 9 in which the biscuits incorporate reinforcing wires or rods made of material which further assists treatment of noxious gases into the atmoshere.
12. An anti-pollution system for treating the outflow of noxious gases as claimed in claims 1-10 in which the biscuits are surrounde by a wire mesh or cage.

13,An anti-pollution system for treating the outflow of noxious gases as claimed in any of claimsl-l 1 in which successive biscuits have a space between them to form chambers to provide firther reactiontime for the gtases to react with the chemicals of the biscuits.

14, An anti-pollution system for the treatment of the outflow of noxious gases as claimed in any of claims 1-12 in which the spaces are formed by projections on the surfaces of the biscuits spacing the biscuits apart