MXPA01003534A - Removal of soot in a gasification system - Google Patents

Abstract

The raw syngas generated in a partial oxidation gasifier (2) also includes carbon soot which is removed and recovered from the syngas by scrubbing with water. The scrubbing water (4) contains one or more high temperature surfactants (6) which allow greater soot concentrations in the water-scrubbing quench zone of the gasifier (2). The carbon soot is separated from the scrubbing water (10) with the aid of a scrubbing oil. The separation of the carbon soot from the scrubbing water (10) is enhanced with the aid of one or more surfactants (6) that render the soot particles hydrophobic and oleophilic. The recovered carbon soot is ultimately recycled to the gasifier (2) to recover the energy value of the carbon during the partial oxidation reaction. The overall energy efficiency of the gasification process can be increased by removing all or a significant portion of the water from the soot mixture before recycling the soot. Separating the soot from the water allows for independent regulation of the soot and water recycle streams, depending on the reaction conditions in the gasifier (2).

Description

"RETIREMENT OF THE HOLLIN IN A GASIFICATION SYSTEM" FIELD OF THE INVENTION This invention is directed to the improvements in the process of partial oxidation of hydrocarbonaceous raw materials, to produce synthesis gas or mixtures of gas species comprising H2, CO, and other types of gaseous materials. In particular, the improvements relate to the recovery of untreated coal and to the moderation of the temperature of the reactor used to produce the gaseous materials, where a hydrocarbonaceous raw material mixed with a recycled dispersion of carbon soot is introduced into the interior of the reactor. a gasification system, particularly in a gasification system fed by oil.

ANTECEDENTS OF L? INVENTION The production of mixtures of gas species from hydrocarbonaceous raw materials requires the addition of oxygen to the reactor of the gas species, which is also known as a gas species generator, or gasifier. These processes also require the addition of a moderator such as C02, steam or water, to keep the reactor temperature within permissible limits established by the economic conditions of the operation and within the limits of refractories of construction materials. of the reactor. A problem associated with the partial oxidation gasification process refers to the presence of unreacted or unconverted carbon, the largest amount in the form of soot, in the crude product of the gas species. Several techniques can be used to remove the soot, the most common is to wash the product of the species of gases with water in a washing machine, where the charred coal is transferred to the washing water and species of washed gases are produced and free of soot. The water with soot content can be further processed using petroleum naphtha to extract the carbon from the water phase. The soot can then be extracted from the petroleum naphtha with a heavy oil. The heavy oil will then substantially contain all the dispatched coal and may be used as a raw material for the partial oxidation reactor, thus using the value of the coal energy. Benzene can be used as an alternative to naphtha as an extractive agent for coal. After separating the carbon from the water, with the benzene, the benzene is removed and recovered for re-use.

Another technique used to remove unreacted or unconverted carbon is to filter the wash water and recover the carbon filter for further processing. U.S. Patent No. 3,979,188 assigned to McCallister, discloses a method of concentrating the water-carbon paste from the washing step of the reactor gaseous effluents in up to about 5 to 7 percent carbon, mix the concentrated paste with a fuel oil and return the coal / oil / water mixture without the vaporization of the partial oxidation reactor as a substitute for the commonly used high-pressure and super-heated steam moderator. U.S. Patent No. 4,699,631, assigned to Marion, also discloses a method for concentrating an aqueous dispersion of soot to produce a pumpable dispersion of soot-water with about 0.55 to 4.0 percent by weight of carbon soot , and recycle the soot-water dispersion to the gas supply of the partial oxidation gasifier. U.S. Patent No. 1,321,069, assigned to Shell International Research, discloses removal of carbon soot by agglomeration of the soot particles with a hydrocarbon oil as an auxiliary agent. The use of an auxiliary substance which makes the soot particles hydrophobic and oleophilic is also disclosed. Once formed, the agglomerated particles are physically removed by using a sieve, they are dried to remove waste water, and are finally recycled back to the gasifier as a reactant. U.S. Patent No. 4,289,647, assigned to Tippmer, discloses a method for recovering carbon from the gas effluent from a gasification reaction. The gas is quenched with water to separate unburned coal and ash, and the heat from the effluent gas is used to produce steam. The washing water is then decanted to separate it in clear water, in water containing carbon, and in ash mud. The water with carbon content is used to produce steam to control the conversion of the ash oil in the gasification reaction. Partial oxidation gasifiers usually operate at high conversion rates to minimize soot formation. The high soot formation is undesirable due to the unstable soot suspensions and the increased gross viscosity. A large soot formation results in a lower efficiency of the cold gas, unless the heat value of the soot is recovered. The amount of water that can be used to wash the soot is limited to that required to function as a moderator in the partial oxidation gasifier, as determined by a heat balance. The amount of soot generated is established by the carbon: oxygen ratio. So the amount of water can not be varied to prevent the excessive accumulation of soot. It is an object of this invention to separate the streams of water and soot to allow variation in the amount of suffocation water used to wash the soot. It is another object of this invention to maintain a low viscosity in the soot / water or soot / oil mixture. Ideally, the gasifier could be operated at lower conversion rates of the gas species, while maintaining a low viscosity in the soot / water or soot / oil mixture. In partial oxidation gasification processes, the raw process gas leaves the reaction zone of the gasifier at a temperature in the range of about 1,700 ° C to about 3,500 ° C, typically around 2,000 ° C a about 2,800 ° C and at a pressure of about 200 psia to about 2,500 psia, typically from around 700 psia to about 1,500 psia. Particle carbon is present in the range of almost nothing to about 20 percent by weight, based on the amount of carbon in the original raw material. U.S. Patent No. 4,021,366, assigned to Robin et. al., teaches that it is desirable to maintain the concentration of carbon particles in suffocation water in the range of almost nothing to 2 percent by weight, preferably below 1.5 percent by weight. The flow of raw and hot effluent gas species leaving the reaction zone of the partial oxidation gasifier carries with it substantially all of the carbon soot particles in the reaction zone of the gasifier. The stream of effluent gases, raw and hot, is introduced into a zone or suffocation chamber located below the reaction zone of the gasifier. The turbulent condition of the suffocation zone, caused by the large volumes of the gas species that bubble through the suffocation water present there, helps to wash the greater amount of soot from the gas species. The suffocation chamber generates quantities of soot mixed with water. This soot can be concentrated by means of recycling the suffocation water to the suffocation zone suffocation ring.

COMPENDIUM OF THE INVENTION The raw gas species generated in the partial oxidation gasifier also includes the carbon soot that has been recovered from the gas species by washing with water. The wash water contains one or more high temperature surfactants which allows higher concentrations of soot in the suffocation zone with washing water from the gasifier. The carbon soot is separated from the washing water with the help of washing oil. The separation of the carbon soot from the washing water is improved with the aid of one or more surfactants which make the soot particles hydrophobic and oleophilic. The recovered carbon soot is ultimately re-cycled to the gasifier to recover the carbon energy value during the partial oxidation reaction. The total energy efficiency of the gasification process can be increased by removing all or a significant portion of water from the soot mixture before re-cycling the soot. Separating the soot from the water allows the independent regulation of the recirculation currents of water and soot, depending on the reaction conditions in the gasifier.

DESCRIPTION OF THE DRAWING Figure 1 is a schematic diagram of the process of the present invention.

DESCRIPTION OF PREFERRED INCORPORATIONS In accordance with the present invention, the addition of one or more surfactants, such as ammonium lignosulfonate or other surfactant equivalent, allows the soot to concentrate in the water as a stable suspension. The surfactants also improve the pumpability of the mixture by means of the reduction of the total gross viscosity. The highest concentrations of soot, in the order of about 3 percent by weight or more, can be achieved in the area of suffocation of the washing water. The soot / water mixture recovered from the washing operation of the gas species is combined with a washing oil, heated and directed towards a high pressure separator. The water is volatilized and the soot forms a suspension with the oil in the high pressure separator. The soot-water mixture is removed from the separator and returned to the gasifier, where it is used as a fuel source. The volatilized water, which also contains small amounts of light oil, exits the high pressure separator and returns to the gasifier to be used as a temperature moderator. When the water is used as the moderator in the gasifier, the soot and water formed during the partial oxidation gasification reaction can be re-cycled to the gasifier. This minimizes or eliminates the need for a soot filter blowing unit or for a coal extraction unit to re-cycle the soot to the gasifier. This invention combines the benefits of steam and water moderators by means of re-cycling soot and water into a narrow stream of the oil feedstock, into the gasifier and then vaporizing and removing water at high pressure. Referring to Figure 1, hot and crude gas species containing small amounts of transported coal soot and very small amounts of transported ore ash are produced in the reaction zone (not shown) in the upper part of the gasifier. The hot gas species then pass to the smothering zone (not shown) in the lower part of the gasifier 2. Here they make contact with the smothering water stream 4 and with the water-based solution 6 containing one or more high temperature surfactants. The temperature of the raw gas species is substantially reduced, and substantially all of the carbon soot and the mineral ash is removed from the gas species. The species of clean and cooled gases 8 leave the zone of suffocation to be additionally processed by the equipment outside the system. The quench water stream 4 contains from about 0.1% by weight of soot to about 1.5% by weight of soot. It is generated in the washing equipment of the species of gases, downstream from the clean and cooled gas species 8. The water-based solution 6 contains one or more high temperature surfactants, such as ammonium lignosulfonate or an equivalent surfactant that is thermally stable at temperatures of about 300 ° F to about 600 ° F. Such surfactants are well known in the art, for example, organic phosphates, sulfonates and amine surfactants. The surfactants are used to establish a stable suspension of soot l¬ in the water, in the lower part of the suffocation chamber, where the soot concentration is in the range of about 3.0% by weight to about 15.0% by weight. The surfactants also reduce the total liquid viscosity. The concentration of surfactants in the lower part of the suffocation chamber varies from about 0.01% by weight to about 0.30% by weight. A concentrated stream of soot-water 10 leaves the zone of suffocation of the gasifier.

A small blowing stream 12 is separated from the stream 10 and leaves the system. The purpose of stream 12 is to purge the system of mineral ash, such as salts and suspended heavy metals. The stream 12 may be directed towards a metal recovery operation (not shown) or towards an appropriate waste disposal system, in accordance with applicable environmental regulations. The mass flow rate of the blow stream 12 is from about 0.005 to about 0.050 that of the soot-water stream 10. The remainder of the soot-water stream 14 flows through the pump 16, in where its pressure is sufficiently increased to allow it to enter a high pressure instantaneous separator 44. The soot-pressurized water 18 leaving the pump 16, can be increased with an optional stream of blowing water 20 supplied from outside the system, usually from the washing equipment of the downstream gas species (not shown). The water stream of blowing 20 often contains high concentrations of ammonium and of formats that are preferably forcibly introduced into the high pressure flash separator 44. The ammonium and the formats enter the reaction zone of the gasifier 2, where decompose under severe operating conditions. By combining the blowing stream 20 with the pressurized soot-water stream 18, to form the high pressure blown / soot-water stream 22, the need for a waste water separation column for the above mentioned washing equipment of the species of gases, is eliminated. The combined high-pressure stream 22 is then contacted with the soot-oil re-cycling stream 24 to form a water / soot-oil stream 26 which enters a high-tension kinetic mixer 36, where it is intimately mixed with an oil raw material, washing machine 28 from outside the system, and with an oil-based solution 32 of one or more surfactants that serve to make the soot particles hydrophobic and oleophilic. The raw material of oil, washer 28, can be any commonly available fuel oil, but be a medium distillate with an API Gravity range of around 30-50, which is preferred. The flow rate of the oil raw material, washing machine 28, is adjusted to maintain the concentration of soot in the lower part of the high pressure flash separator 44 in the amount of about 5.0% by weight to about 50.0% by weight . The purpose of using a second surfactant in the oil-based solution 32 is to make the soot particles hydrophobic and oleophilic. These surfactants are well known in the art and include carboxylates, phosphates, sulfonates, sulfates, alcohols, glycols, amines and organic oxides, preferably the polymers of the alkylene glycols, the amines ether alkyls , the oxyalkilene amines, and the oxypropylene diamines. The concentration of the surfactants varies from about 0.01% by weight to about 0.30% by weight of the total of the soot / oil / water mixture 38 leaving the kinetics mixer 36.

The intimately mixed treated water / oil / soot surfactant stream 38 enters the heat exchanger 40, where it exits as a heated stream of water / oil / soot 42 under the conditions necessary for the desired instantaneous separation, when entering the high pressure flash separator 44. The high pressure flash separator 44 typically operates at about 100 psi to about 200 psi above the operating pressure of the gasifier 2, which operates at pressures ranging from about 200 psia. to about 2,500 psia, and preferably from about 700 psia to about 1,500 psia. The operating temperature of the high pressure flash separator 44 ranges from about 450 ° F to about 650 ° F. The steam stream 46 leaves the high pressure flash separator 44 and contains small amounts of vaporized oil and transported in the order of about 0.1% by weight to about 5.0% by weight. The steam stream 46 will be used as a moderator to regulate the temperature in the partial oxidation gasifier 2. However, a portion 48 of the vapor stream 46 that is not required to be used as a temperature moderator can be divided. and introduced into the light oil recovery and heat waste 50 unit.

The remainder of the steam stream 52 to be used as a moderator passes through the heat exchanger 54, where it is super heated to a temperature of about 50 ° F to about 150 ° F over the saturation conditions and it comes out as a super heated steam stream 56 which enters the gasifier 2, where it is used as a temperature moderator. Super heating the steam improves the overall performance of the raw material injector nozzle (not shown) which serves as the inlet for the hydrocarbonaceous fuel 66 towards the gasifier 2. The concentrated soot-oil mixture 58 leaves the instant separator of high pressure 44 is substantially free of water and passes through pump 60, where its pressure is increased by about 100-200 psi more than the operating pressure of gasifier 2. The concentrated and pressurized mixture of soot-oil 62 , it leaves pump 60 and is divided into streams 24 and 64. The flow rate of stream 24 is adjusted to maintain a water to oil weight ratio in stream 38, from about 03.: 1 to about 3: 0, respectively. The flow rate of the stream 64 is controlled by the level in the instant high pressure separator 44 and is essentially equal to the flow rate of the stream of oil raw material, washing machine 28. The concentrated and pressurized mixture of soot -oil 64, enters the partial oxidation gasifier 2, where it supplements the hydrocarbonaceous fuel 66 as a reactant. The weight ratio of stream 64 to stream 66, is generally around 0.05: 1 to about 0.30: 1, respectively. The remaining portion 24 of the concentrated soot-water mixture is contacted and mixed with the high pressure soot-water blowing stream.

Claims (7)

R E I V I N D I C A C I O N S

1. A process for recovering and using carbon black that accompanies the synthesis gas without treatment produced during the gasification reaction by partial oxidation of hydrocarbonaceous feeds, consists of: a) separating the carbon black from the untreated synthesis gas by purification with water in the presence of a first surfactant to form a concentrated black smoke / water mixture, and improve the pumping capacity of the mixture by reducing the total relative viscosity; b) contacting the black-smoke / water mixture with a scrubbing oil in the presence of a second surfactant to make the particles of carbon black hydrophobic and oleophilic and to form an intimate mixture of carbon black / oil / water; c) separating the black smoke / oil / water mixture in a black smoke / oil mixture and vaporized water without carbon black by means of an instantaneous high pressure separation operation; d) recycle at least a part of the vaporized water, without carbon black, to the gasification reaction by partial oxidation to serve as a temperature moderator; and e) recycling the black smoke / oil mixture to the gasification reaction by partial oxidation where it is used as fuel.

2. The process of claim 1, wherein the first surfactant is selected from the group consisting of: phosphates, organic sulfates and amines.

3. The process of claim 2, wherein the surfactant is ammonium lignosulfate. The process of claim 1, wherein the black smoke / water concentrate mixture contains about 3.0 wt% to about 15.0 wt% of carbon black. The process of claim 1, wherein the scrubbing oil is a semi-distillate in the range of about 30-50 API gravity. The process of claim 5, wherein the concentration of carbon black in the black smoke / oil mixture exiting the instant high pressure separation operation ranges from about 5.0 wt% to about 50.0 wt%. The process of claim 1, wherein the pressure during the instantaneous high pressure separation operation is from about 100 psi (689.7 kPa) to about 200 psi (1379.4 kPa) greater than the pressure of the gasification reaction by oxidation partial.