MXPA01006712A - Method for reducing hydrogen chloride emissions from an asphalt air-blowing process - Google Patents

Abstract

In a method for reducing hydrogen chloride emissions from an asphalt blowing process, ferric chloride and/or ferrous chloride are added to the asphalt. A chemical modifier is also added to the asphalt. The asphalt is subjected to a blowing process which produces hydrogen chloride emissions. The addition of the chemical modifier reduces the hydrogen chloride emissions by at least 25%compared to the same process without the addition of the chemical modifier. The addition of the ferric chloride and/or ferrous chloride provides beneficial effects such as increased blowing rate and increased final penetration of the asphalt. Preferably, the addition of the chemical modifier does not significantly reduce these beneficial effects.

Description

METHOD FOR REDUCING HYDROGEN CHLORIDE EMISSIONS FROM AN AIR BLOWING PROCESS ASPHALT TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION This invention relates, in general, to the asphalt process and, particularly, to a method for reducing hydrogen chloride emissions from an asphalt air blowing process. More particularly, this invention relates to a method for reducing the emissions of hydrogen chloride from the blowing of air from an asphalt modified with ferric chloride or ferrous chloride, by the addition of a chemical modifier to the asphalt, before the blowing process of air or earlier in the process. The method has industrial applicability, for example, in air blowing of asphalt for use as an asphalt for roofing.

BACKGROUND OF THE INVENTION Although most asphalts are used for paving, some asphalts are used for other applications, such as for roofing. Not all available asphalts are naturally suitable for roofing applications. The asphalts for the roof are blown with air to raise the softening point of the asphalt and meet other specifications. One way to use more asphalt filler materials for roofing is to add a ferric chloride or ferrous chloride catalyst to the asphalt, before the air blowing process. This ferric chloride or ferrous chloride improves the properties of the asphalt, such as the penetration to an objective softening point and accelerate the air blowing process to reduce the time of penetration. Unfortunately, emissions of hydrogen chloride are generated when an asphalt, modified with ferric chloride or ferrous chloride, is blown with air. When the asphalt is modified with ferric chloride, the reduction of ferric chloride to ferrous chloride, during the air blowing process, generates hydrogen chloride emissions. When ferric chloride is added as an aqueous solution to asphalt, hydrogen chloride emissions are also generated from free hydrochloric acid, present in the aqueous solution. More emphasis is placed on regulating the levels of hydrogen chloride emissions to reduce air pollution, and this trend will increase over time. If regulated levels of emissions are not achieved, the production of asphalt with ferric chloride or ferrous chloride will be restricted. There are no methods to reduce hydrogen chloride emissions from an asphalt air blowing process. The patent literature does not suggest a solution to the problem of hydrogen chloride emissions. U.S. Patent No. 5,611,910 to Marzari et al. , reveals a method to reduce sulfur oxide emissions from an asphalt air blowing process, adding an additive, which reduces emissions to asphalt, before blowing air or early in the process. This additive comprises: (a) at least one compound selected from the hydroxides of metals, metal oxides, metal carbonates and metal bicarbonates, wherein the metal is selected from calcium, sodium, potassium and magnesium; and (b) at least one compound selected from the hydroxides of metals, metal oxides, metal carbonates and metal bicarbonates, wherein the metal is selected from zinc, copper and aluminum. A preferred additive is a combination of 0.05 to 0.075% sodium hydroxide, 0.01 to 0.7% zinc oxide and 0.01 to 0.5% copper oxide, by weight of the asphalt and additive.

The Marzari et al patent does not reveal the use of ferric chloride or ferrous chloride, or the problem resulting from hydrogen chloride emissions. In particular, there is no discussion of a method to reduce emissions of hydrogen chloride. Likewise, the patent discloses the use of a level of sodium hydroxide, in which the current work indicates will reduce the beneficial effects of ferric chloride or ferrous chloride in increasing the reaction rate and improving the properties of the product. U.S. Pat., No. 2,506,283 to Smith et al. , reveals adding ferric chloride to asphalt, as a catalyst, during an air blowing process of the asphalt, and adding a basic or alkaline earth metal oxide or hydroxide, as a separate operation, after blowing air, to prevent the formation of foam on the surface of the asphalt. There is no suggestion of adding a chemical modifier to the asphalt prior to the air blowing process, and there is also no suggestion to reduce hydrogen chloride emissions from air blowing. Therefore, it is convenient to provide a method to reduce hydrogen chloride emissions from the blowing of air from an asphalt modified with ferric chloride or ferrous chloride.

SUMMARY OF THE INVENTION The present invention provides a method for reducing hydrogen chloride emissions from an asphalt blowing process. Ferric chloride and / or ferrous chloride are added to the asphalt. A chemical modifier, according to the invention, is also added to the asphalt. This asphalt is subjected to a blowing process, which produces emissions of hydrogen chloride. The addition of the chemical modifier reduces hydrogen chloride emissions by at least 25% by weight, compared to the same process without the addition of the chemical modifier. The addition of ferric chloride and / or ferrous chloride provides beneficial effects, such as an increased blowing rate and increased final penetration of the asphalt. Preferably, the addition of the chemical modifier does not significantly reduce these beneficial effects. Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments.

DETAILED DESCRIPTION AND PREFERRED MODALITIES OF THE INVENTION This invention relates to a method to reduce the emissions of hydrogen chloride from the air blowing process of a modified asphalt with ferric chloride and / or ferrous chloride, by adding a chemical modifier to the asphalt, before the air blowing process or early in the process. The raw material of asphalt that is going to blow with air, can be either the asphalt that occurs naturally or a manufactured asphalt, produced by the refining of the oil. They may include asphalts derived from directly operated fractions, asphalts from thermal decomposition, asphalts derived from processes, such as oxidation of asphalt, deasphalting of propane, steam distillation of water, chemical modification and the like. Mixtures of different kinds of asphalt can also be blown with air. The asphalt raw material is loaded in a suitable apparatus for air blowing of the asphalt, such as a converter. The asphalt is usually loaded at a temperature range of about 175 ° C to 230 ° C. The air blowing process involves passing air, or another gas containing oxygen, through the asphalt into the converter.

A mixture of a gas containing oxygen with an inert gas, such as nitrogen or helium, can also be used. The reaction produced < by the blowing of the air it is exothermic and raises the temperature of the asphalt. The temperature of the asphalt, during the air blowing process, usually varies from approximately 200 to 270 ° C. The maximum temperature can be controlled by a shirt cooled with water or by other means. The air blowing process increases the usefulness of the asphalt by raising the softening point from a typical starting point below 40 ° C to a final softening point of at least about 80 ° C. The time of the process can take from about 1 to 18 hours to reach the desired softening point. The process time is dependent on the temperature of the process, the air flow regime, the characteristics of the asphalt and the specifications of the desired product. According to the invention, the ferric chloride and / or ferrous chloride catalyst is added, either mixing it in the asphalt before the air blowing process or adding it to the asphalt in the converter early in the process, preferably within about the first hour. The addition of ferric chloride and / or ferrous chloride increases the rate of the air blowing process compared to the same process without the addition of ferric chloride and / or ferrous chloride. Ferric chloride usually increases the rate by at least 20%, typically by at least 30% and, more typically, by at least 40 to 50%. Ferrous chloride usually increases the rate by at least 35%, typically by at least 45% and, more typically, by at least 50 to 60%. The addition of the ferric chloride and / or ferrous chloride, also, usually, has other beneficial effects, such as the increased final penetration of the air-blown asphalt to a target softening point. Both ferric chloride and ferrous chloride usually increase the final penetration of the asphalt by at least 15% and typically by at least 20% to 30%. The flow of air blown through the converter usually varies from approximately 220 to 650 liters (STP) per horra liter of the processed asphalt. The air is bubbled through the hot asphalt and produces a stream of smoke after it passes through the asphalt. The passage of air separates some materials from the asphalt, which include hydrogen chloride, generated by the addition of ferric chloride and / or ferrous chloride. The smoke stream leaves the converter and passes through a smoke line in a drain tank, sealed to the liquid. The liquid in this drain tank is a mixture of oil and water that condenses from the process. The temperature of the oil / water mixture in the pour tank typically ranges from about 65 to 121 ° C. The smoke stream is bubbled through the oil / water mixture and the drain tank condenses some of the material from the smoke stream; however, a significant amount of material still passes through it. Prior to release into the atmosphere, the smoke stream is subjected to an incineration process to control the emission of volatile organic compounds. Unfortunately, neither the emptying tank nor the incineration process adequately controls the emission of hydrogen chloride. In accordance with the present invention, a chemical modifier is added to the asphalt to reduce emissions of hydrogen chloride. As described below, the chemical modifier is a chemical or a combination of chemicals, which is effective in reducing emissions of hydrogen chloride. This chemical modifier can be added by mixing it in the asphalt, before the air blowing process or adding it to the asphalt in the converter in the early phase of the process, preferably within about the first hour. The chemical modifier can be added before or after the ferric chloride and / or ferrous chloride. The addition of the chemical modifier reduces hydrogen chloride emissions from the air blowing process, by at least 25% (weight percent), preferably by at least 45% and more preferably by at least 65%, compared to the same process without the addition of the chemical modifier. Hydrogen chloride emissions are measured at the chimney exit of the incinerator. It has been discovered that certain types of chemicals and combinations of chemicals are suitable for use as the chemical modifier, while other chemicals and combinations of chemicals are not suitable. Some chemicals that are expected to reduce hydrogen chloride emissions, either found to have no substantial effect on hydrogen chloride emissions or actually increased emissions. The materials and conditions of the air blowing process present a unique environment and the chemical modifier must be particularly suitable for use in that environment. Preferably, the chemical modifier is selected from sodium hydroxide, zinc oxide, ferric stearate, ferric citrate, iron oxide, high molecular weight amines, polyamines, aluminum, a combination of sodium hydroxide and zinc oxide, a combination of Sodium hydroxide and ferrous oxide, a combination of aluminum and ferrous oxide, or a combination of aluminum and zinc oxide. More preferably, the chemical modifier is a combination of sodium hydroxide and zinc oxide. The combination of chemicals has a synergistic effect in reducing emissions of hydrogen chloride. Some proposed reactions with hydrogen chloride in the converter are: Sodium hydroxide + HCl - sodium chloride + water Zinc oxide + HCl - »zinc chloride + water Ferric stearate + HCl - > ferric chloride + stearic acid Ferric citrate + HCl - »ferric chloride + citric acid Aluminum + HCl -» aluminum chloride + hydrogen Ferrous oxide + HCl - ferric chloride + water Jeffamine T-403 + HCl - »chlorine hydride and Jeffamine Jeffamine T-403 is trimethylolpropanetris ([poly (propylene glycol), amine terminated]), available from Huntsman, Corp. Austin, TX., USA.

These reactions make chemical modifiers highly suitable for extracting hydrogen chloride during the air blowing process.

As discussed above, the addition of the ferric chloride and / or ferrous chloride usually provides beneficial effects, such as an increased rate of air blowing and the increased final penetration of the asphalt at a target softening point. Preferably, the addition of the chemical modifier does not excessively reduce these beneficial effects. Typically, the addition of the chemical modifier does not reduce these beneficial effects by more than 50%, preferably by no more than 35% and, more preferably, by no more than 20%. Especially preferred, the addition of the chemical modifier does not significantly reduce the beneficial effects of ferric chloride and / or ferrous chloride. Therefore, it has been discovered that some of the chemical modifiers must be limited in the amount added to avoid reducing the beneficial effects of ferric chloride and / or ferrous chloride. When sodium hydroxide is used as the chemical modifier, alone or in combination with other chemicals, sodium hydroxide is preferably added at a level not higher than 0.012% by weight of the asphalt, for each 0.1% by weight of the chloride ferric or ferrous chloride active added to asphalt. For example, if the level of the added ferric chloride is 0.3% by weight of the asphalt, preferably the level of the added sodium hydroxide is not greater than 0.036% by weight of the asphalt. Sodium hydroxide is usually added at a level of at least 0.001% by weight of the asphalt, typically at least 0.004%, per 0.1% by weight of the ferric chloride or added active ferrous chloride. When zinc oxide is used as the chemical modifier, alone or in combination with other chemicals, preferably zinc oxide is added at a level not higher than 0.15% by weight of the asphalt, for each 0.1% by weight of the chloride ferric or ferrous chloride active aggregates. The zinc oxide is usually added at a level of at least 0.02% by weight of the asphalt, typically at least 0.05%, for each 0.1% by weight of the active ferric chloride or ferrous chloride added. The term "ferric chloride" and / or "active" ferrous chloride means the actual weight of the ferric chloride and / or ferrous chloride, excluding the weight of the water of the solvation and solution. In another embodiment of the invention, hydrogen chloride emissions are further reduced by the addition of a filter between the waste tank and the incinerator. The filter removes the hydrogen chloride by condensation and coalescence from the cooled smoke stream. The smoke stream can be cooled or by the natural heat exchange from the smoke line to the atmosphere, or by any specific cooling operation. The filter can be of any type, capable of removing oil or condensable water from the smoke stream. If used alone, the filter preferably reduces hydrogen chloride emissions by at least 25% and, more preferably, by at least 45%, compared to the same process without the filter. If used in combination with the chemical modifier, the filter preferably reduces hydrogen chloride emissions by at least 10% in addition to the reduction provided by the chemical modifier and, more preferably, by at least 20%. Preferably, the filter is a fiber bed filter. Such filters are described in Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. I, 4th Ed., Pages 799-800 (1991). The fiber bed filter includes a fiber bed element to condense the smoke stream. This fiber bed element is made of fibers that are packaged either randomly or in alignment. The use of randomly oriented fiber beds is preferred in the present invention. This bed of randomly oriented fibers includes those made of mineral fiber, such as glass fibers, polymer fibers, such as polyester fibers or polypropylene fibers, and fluorocarbon fibers. As an example of suitable fibers are finely spun glass fibers, which have an average diameter of about 1-2 microns. Other fibers will be acceptable, depending on their compatibility with the chemical modifier and with the asphalt. In another preferred embodiment of the invention, hydrogen chloride emissions are further reduced by the injection of a spray of water or steam into the smoke stream, immediately downstream from the converter. It has been found that both water spray and water vapor are effective in removing hydrogen chloride from the smoke stream, because hydrogen chloride is highly hygroscopic. Preferably, the water spray or water vapor is injected into the smoke line within approximately 0.3 meter of the converter outlet. Preferably, the water or steam spray is injected into the smoke stream at a rate in the range of about 0.05 to 6 liters of condensed water per minute per cubic meter of the airflow in the STP. If used alone, the water or steam spray preferably reduces hydrogen chloride emissions by at least 25% and, more preferably, by at least 45%, in sympathy with the same process without spraying water or steam . If used in combination with the chemical modifier, this water or water vapor spray preferably reduces hydrogen chloride emissions by at least 10%, in addition to the reduction provided by the chemical modifier and, more preferably, by at least 20% If the water or steam spray is used in combination with the filter, hydrogen chloride emissions are preferably reduced by at least 65%, compared to the same process without the filter and water or steam spray.

Example 1 Chemical Modification in a Small Converter Monitoring of HCl emissions began in a converter of 3,785 liters. Three different sources of asphalt were tested. Before adding a chemical to the converter, the air was connected at a low rate of 0.28 cubic meters per hour in STP. Then, depending on how many chemicals are added, different amounts of asphalt were first introduced into the converter. If a chemical product is going to be used (just ferric chloride as a control), half of the asphalt is loaded, if two chemicals are used, one third of the asphalt is introduced; and if three chemicals are used, one quarter of the asphalt is added to the converter. Ferric chloride was always the first chemical to be added, with a corresponding amount of asphalt in the upper part. Ferric chloride (solid) was added at an active level of 0.3% by weight of the asphalt. This was continued until all the asphalt and chemicals were in the converter. This converter was then increased to a temperature of 254 ° C and the air was increased to 0.85 cubic meters per hour. At this point, the test officially began. In order to measure the amount of hydrogen chloride emissions from the converter, the following steps were taken. Once the equipment was adjusted, the exhaust was connected to a series of two baths of 0.2N sodium hydroxide solution. The gases were grooved in such a way that they bubbled through the baths. Most acid gases (HCl, H2S, carboxylic acids) were captured by this solution. A sample was sent to an external laboratory to measure the concentration of chloride ions by an ion chromatography technique.

Results and Conclusions Each of the three asphalts were operated with ferric chloride to determine the amount of emissions generated. Table 1 shows the results of these tests. It can be seen that only about 12 to 24% of the HCl emissions expected stoichiometrically (due to the reduction of ferric chloride to ferrous chloride) were developed from the converter. Table 1 Different Emissions of HCl with Different Asphalts A wide variety of chemical additives were introduced into the asphalt in an attempt to reduce HCl emissions. The added chemicals were: aluminum, calcium carbonate, ferric citrate, ferric phosphate, ferric stearate, ferrous oxide, Jeffamine T-403, polyvinyl alcohol (PVA), co-glycidyl polyethylene methacrylate (PEGMA), sodium hydroxide, oxide of zinc, zinc and ethylene vinyl acetate copolymer (Elvaloy, manufactured by DuPont, Wilmington, DE). Blowings of the asphalt were completed with each of the chemicals and active ferric chloride at 0.3% in solid form. The results were grouped into three different categories; chemicals that reduced HCl emissions, chemicals that had no effect on HCl emissions, and chemicals that increased HCl emissions. The results are shown in Tables 2 to 4: Table 2 Chemical Products that Reduce HCl Emissions Table 3 Chemical Products that Have No Effect on HCl Emissions Table 4 Chemical Products that Increase HCl Emissions Additional tests were performed with zinc oxide, to determine the purification performance against the aggregate concentration. As shown in Table 5, zinc oxide provided a good reduction in HCl emissions, when added at a level of 0.15% and provided a very good reduction in HCl emissions when added at a level of 0.30. % or 0.45%.

Table 5 Variable Concentration of Zinc Oxide A few combinations of chemicals were treated as the chemical modifier. The results are grouped into two different categories: combinations of chemicals that reduce HCl emissions and combinations of chemicals that have no effect on HCl emissions. The results are shown in Tables 6 and 7.

Table 6 Table 7 Combinations of Chemical Products that Have No Effect on HCl Emissions Two Modifiers Concentration% Asphalt% Reduction Elvaloy + CaC03 0. 13 + 0 19 11 # 2 Example 2 3.785 Liter Converter, Which Uses Solid Ferric Chloride Modifiers and Chemicals The test was done with air blowing on asphalt # 2 in a 3,785 liter converter. The solid ferric chloride was added to the asphalt as follows: Starting from 2,724 kilograms of asphalt in the converter, 681 kilograms of moved to the mixed tank. The ferric chloride was then added in small amounts to the mixed tank through a funnel in the tank lid, until an active level of 0.3% active ferric chloride was added by weight of the asphalt. When the addition of ferric chloride was completed, the asphalt was moved from the mixed tank back to the converter. The chemical modifier was a combination of zinc oxide and sodium hydroxide. After 681 kilograms of asphalt, modified with ferric chloride, have been brought back to the converter, another 681 kilograms of unmodified asphalt was pumped into the mixed tank. Zinc oxide and sodium hydroxide were added to the mixed tank through a funnel in the tank lid. Then the asphalt moved from the mixed tank back to the converter, and the modified asphalt was blown with air.

Environmental Adjustment of the Equipment A probe in the chimney of the incinerator boosted samples of the emission gases developed at a rate of 6-8 liters per minute. The gas was carried through a sample line heated at 179 ° C to a Mini-GASS ™ gas analysis sampling system (Perma Puré Inc., Toms River, NJ). The sampling system removed water from the gas and sent it to the following analyzers: for hydrogen chloride emissions, a TECO Model 15 analyzer (Thompson Equipment Co., New Orleans, LA); and for sulfur dioxide emissions, a Bovar Model 721 ATM analyzer (Bovar Equipment Co., Hattershein, West Germany). Emissions were measured continuously using these monitors. The analog signal from each monitor was collected by a Campbell CRIO data logger (Campbell Scientific, Inc., Logan, UT) and transformed to digital values. After the operation, the emission data was downloaded to a laptop, which uses a software (program) of data logger support. The emissions were collected every 30 seconds. The equipment was calibrated before each operation, using a zero gas as a calibration gas.

Results and Discussion Table 8 shows a summary of the emissions, processing time and penetration data. The 0.3% unchanged ferric chloride formulation (30 + 0 + 0) was repeated four times, with the results being averaged. All other data are simple pieces of information or data points. The emissions are in units of kilograms per metric ton. "% Ben" means the percentage of the maintained benefit of the addition of ferric chloride.

Table 8 Results of the Emission Test of 3,785 liters, which uses Solid Ferric Chloride The formulation (30 + 2.4 + 15) of 0.3% ferric chloride, + 0.024% sodium hydroxide + 0.15% zinc oxide, is the optimal formulation in this example, because it not only reduces HCl emissions by 65%, but also decreases sulfur oxide emissions by 75%, maintains 95% of the benefit of the increased air blowing regime of the addition of ferric chloride and maintains 88% of the increased final penetration benefit of the addition of ferric chloride.

Example 3 3.785 Liter Converter, which Uses the Chemical Addition of Ferrous Chloride Modifiers and Chemical Modifiers The test was done with the air blowing of asphalt # 2 in the 3.785 liter converter. The liquid ferrous chloride was added to the asphalt as follows: starting with 2,724 kilograms of asphalt in the converter, 2,270 kilograms moved to the wave tank, leaving 454 kilograms in the converter. This allowed the level of asphalt in the converter to be below the level of the door, where the liquid ferrous chloride was added. The blower was driven and decreased to a differential pressure reading of 1.8. Then the liquid ferrous chloride was slowly added to the asphalt in the converter, using a manual rotary pump. The chemical modifier was a combination of zinc oxide and sodium hydroxide. Zinc oxide and sodium hydroxide were added to the asphalt in the wave tank. The asphalt, in the wave tank, was then brought back to the converter and the operation started.

Results and Discussion Table 9 shows a summary of the data on emissions, process time and penetration. The unmodified 0.3% ferrous chloride solution was repeated three times, and the results averaged. All other data are simple pieces of information. It can be seen that none of the formulations reduces emissions to the extent that can be obtained with solid ferric chloride. The optimal formulation for this data adjustment is: 0.3% ferrous chloride, 0.012% sodium hydroxide and 0.15% zinc oxide (30 + 1.2 + 15).

Table 9 Results of the Emissions Test of 3,785 liters, which uses a 30% Water Solution of Ferrous Chloride Example 4 3.785 Liter Converter Using Chloride Modifiers Ferric Liquid and Chemicals The test was done with the blowing of air to asphalt # 2 in a converter of 3.785 liters. The liquid ferrous chloride was added to the asphalt as follows: starting with 2,724 kilograms of asphalt in the converter, 2,270 kilograms were moved to the wave tank, leaving 454 kilograms in the converter. This allowed the level of asphalt in the converter to be below the level of the door, where the liquid ferrous chloride was added. The blower was driven and decreased to a differential pressure reading of 1.8. Then the liquid ferrous chloride was slowly added to the asphalt in the converter, using a manual rotary pump. The chemical modifier was a combination of zinc oxide and sodium hydroxide. Zinc oxide and sodium hydroxide were added to the asphalt in the wave tank. The asphalt, in the wave tank, was then brought back to the converter and the operation started.

Results and Discussion Table 10 shows a summary of the emissions, processing time and penetration data. It can be seen that none of the formulations reduced emissions to the extent that can be obtained with solid ferric chloride. The optimal formulation for this example is 0.3% ferrous chloride + 0.012% sodium hydroxide + 0.15% zinc oxide (30 + 1.2 + 1.5).

Table 10 Results of the Emission Test of 3,785 liters, using a 40% Ferric Chloride Water Solution Example 5 Addition of a Fabric Filter between the Emptying Tank and the Incinerator In the process of blowing air, described above, the smoke line was equipped with a cloth filter, after the emptying tank and before the incinerator. This cloth filter was activated before starting the operation and before activating the blower. The results are shown in Table 11: Table 11 Adding a Fabric Filter • * A chemical modifier comprising 0.012. of NaOH and 0.15% ZnO, by weight of the asphalt, was added to the asphalt in the converter.

• ** A chemical modifier comprising 1.82 kilograms of calcium hydroxide was added to the liquid seal in the drain tank.

The results show significant reductions in HCl emissions by the use of the fabric filter alone and in combination with the chemical modifier.

Example 6 Water Vapor Injection in the Smoke Line After the Converter In the air blowing process of the asphalt, as described above, water vapor or water spray was injected into the smoke line, after the converter , in an attempt to reduce hydrogen chloride emissions from the process. Both applications joined the smoke line within 0.3 meter of the converter output. The results are shown in the following Table 12: 31 - «- '" »" - • Table 12 Water Vapor Injection • * 3,785 kg of condensed water per hour • ** 9.5 kg of condensed water per hour.

The results show a significant reduction in HCl emissions with water vapor or water spray. Water vapor was somewhat more effective, reducing HCl emissions by 88% and 89%. Using the water vapor in combination with a cloth filter, there was an even greater reduction in HCl emissions, of 96%. While the invention has been described in terms of the benefit of reducing air pollution from hydrogen chloride emissions, it should be noted that the invention also provides other benefits. For example, the reduction of hydrogen chloride in the asphalt decreases the corrosivity of the asphalt, so there is less corrosion of the manufacturing equipment and less corrosion of the metal parts in the roof. This decreased corrosivity of the asphalt allows it to be used in a wider variety of applications. The principle and mode of operation of this invention have been described in their preferred embodiments. However, it should be noted that this invention can be practiced in another way to that illustrated and described specifically, without departing from its scope.

Claims (10)

1. A method to reduce emissions of hydrogen chloride from an asphalt blowing process, this method includes: modifying an asphalt, adding a catalyst, selected from ferric chloride, ferrous chloride, or their mixtures, and adding a chemical modifier; subjecting the modified asphalt to a blowing process, which produces a smoke stream containing hydrogen chloride; and emitting the smoke stream, in which the addition of the catalyst provides a beneficial effect of an increased final penetration, compared to the same blowing process, without the addition of the catalyst; where the addition of the chemical modifier reduces hydrogen chloride emissions from the blowing process by at least 25% by weight, compared to the same blowing process, without the addition of the chemical modifier; and wherein the addition of the chemical modifier does not reduce the beneficial effect of the catalyst by more than about 50%.

2. The method of claim 1, wherein the addition of the catalyst provides a beneficial effect of increasing the final penetration by at least 15%, compared to the same blowing process without the addition of the catalyst, and where the addition of the chemical modifier does not reduces the beneficial effect of the catalyst by more than about 35%.

3. The method of claim 1, wherein the addition of the catalyst further provides a beneficial effect of an increased blowing rate, compared to the same blowing process without the addition of the catalyst, and where the addition of the chemical modifier does not reduce the beneficial effect of the catalyst by more than about 50%.

4. The method of claim 1, wherein the chemical modifier includes sodium hydroxide, which is added at a level no greater than about 0.012% by weight of the asphalt, for each 0.1% by weight of the active catalyst added to the asphalt.

5. The method of claim 1, wherein the chemical modifier includes zinc oxide, which is added at a level no greater than about 0.25% by weight of the asphalt, for every 0.1% by weight of the active catalyst added to the asphalt.

6. The method of claim 1, wherein the chemical modifier comprises a combination of sodium hydroxide and zinc oxide, this sodium hydroxide being added at a level no greater than about 0.012% by weight of the asphalt, and the zinc being added at a level no greater than about 0.15% by weight of the asphalt, per each 0.1% by weight of the active catalyst added to the asphalt.

7. The method of claim 1, wherein the chemical modifier is selected from sodium hydroxide, zinc oxide, ferric stearate, iron oxide, ferric citrate, high molecular weight amines, polyamines, aluminum, a combination of sodium hydroxide and zinc oxide, a combination of sodium hydroxide and ferrous oxide, a combination of aluminum and ferrous oxide, or a combination of aluminum and zinc oxide.

8. The method of claim 7, wherein the chemical modifier comprises a combination of sodium hydroxide and zinc oxide.

9. A method to reduce emissions of hydrogen chloride from an asphalt blowing process, this method includes: modifying an asphalt, adding a catalyst, selected from ferric chloride, ferrous chloride, or their mixtures, and adding a chemical modifier, selected of sodium hydroxide, zinc oxide, ferric stearate, iron oxide, ferric citrate, high molecular weight amines, polyamines, aluminum, a combination of sodium hydroxide and zinc oxide, a combination of sodium hydroxide and oxide ferrous, a combination of aluminum and ferrous oxide, or a combination of aluminum and zinc oxide, provided that the sodium hydroxide is added at a level no greater than about 0.012% by weight of the asphalt, and the oxide of zinc is added at a level no greater than about 0.15% by weight of the asphalt, for every 0.1% by weight of the active catalyst added to the asphalt; subjecting the modified asphalt to a blowing process, which produces a smoke stream containing hydrogen chloride9; and emit the smoke stream; wherein the addition of the catalyst provides a beneficial effect of an increased final penetration, as compared to the same blowing process without the addition of the catalyst; where the addition of the chemical modifier reduces hydrogen chloride emissions from the blowing process, by at least 25% by weight, compared to the same blowing process without the addition of the chemical modifier, and in that addition of the chemical modifier it does not reduce the beneficial effect of the catalyst by more than about 50%.

10. The method of claim 9, wherein the chemical modifier comprises a combination of sodium hydroxide and zinc oxide.