MXPA01000098A - Process for autothermal reforming of a hydrocarbon feedstock - Google Patents

Abstract

Process for the preparation of a hydrogen and/or carbonmonoxide rich gas comprising the step of partial oxidation of a hydrocarbon feedstock with an oxygen containing reactant stream in presence of steam, wherein the steam is present in the hydrocarbon feedstock in an amount higher than in the oxygen containing reactant stream.

Description

PROCEDURE FOR THE AUTOTERMIC RESTORATION OF A HYDROCARBON SUPPLY MATERIAL DESCRIPTIVE MEMORY The present invention is directed to the soot-free autothermic restoration (RAT) of the hydrocarbon supply material. In the autothermal restoration, the combustion of the hydrocarbon supply material with substoichiometric quantities of oxygen is carried out by flame reactions in a burner combustion zone and, subsequently, the restoration of steam from the partially burned supply material in a bed. Fixed vapor recovery catalyst. Substequimetric combustion of hydrocarbons disadvantageously leads to the formation of soot. Soot formation can be avoided by using a specific burner design and controlling the operating conditions of the RAT process. Soot is formed in the flame of an autothermal reactor within certain limits of operating conditions. When the amount of vapor relative to the other components introduced to the RAT reaction is under a certain critical value, soot forms in the reactant supply material. The amount of steam can be expressed as the critical ratio of steam to coal, calculated as the molar flow velocity of the vapor at the molar flow rate of the carbon in the hydrocarbon supply material. The hydrocarbon supply material can be present in the form of natural gas or another type of hydrocarbon, including LPG, butane, naphtha, etc. The molar flow rate of the carbon is calculated as the molar flow rate of the hydrocarbon multiplied by the hydrocarbon content. The design of the burner nozzles influences the critical relationship of steam to coal. A similar burner is described, useful in the RAT, in the patent of E.U.A. 5,496,170. It summarizes examples of operating conditions, which do not cause soot, in a document by Christensen and Primdahl (Hydrocarbon Processing, March 1994, pages 39-46). The conditions exposed in this document are shown in table 1. Due to the relatively small heat loss of the pilot unit in the Christensen and Primdahl experiments at the adiabatic temperature of RAT output, the temperature will be higher than the temperature given in table 1. This means that if a unit is subjected to large, from which the loss of heat is negligible, at exactly the same conditions, the outlet temperature will be close to the adiabatic temperature of RAT output. Advantageously, the procedure is carried out in low steam to coal ratios, since a low ratio decreases the investment expenses for a RAT plant and reduces the energy consumption needed in the operation of the plant. Additionally, a low ratio of steam to carbon makes it possible to optimize the produced composition of synthetic gas for the production of CO-rich gases, for example for the synthesis of methanol or dimethyl ether and Fischer-Tropsh processes. The supply material to the RAT is divided into two separate streams that is sent to the burner. A stream contains oxygen and vapor. The other stream contains hydrocarbon and steam, and optionally hydrogen and / or carbon dioxide. The two streams are mixed downstream to the burner and combustion takes place. It has now been found that the critical ratio of steam to carbon depends on the distribution of the vapor to the stream of oxygen and hydrocarbon supply material. When the amount of vapor contained in the oxygen supply stream is reduced, the critical vapor ratio a! carbon. Based on the above findings, this invention provides a process for the preparation of a gas rich in hydrogen and / or carbon monoxide, comprising the step of partial oxidation of the hydrocarbon supply material with a reactive stream containing oxygen in the presence of steam, wherein the vapor is present in the hydrocarbon supply material in a higher amount than in the oxygen-containing reactive stream. The invention allows the operation of the process at a lower ratio of vapor to carbon compared to the critical vapor / carbon ratio to the same vapor distribution between the streams containing the oxygen and the hydrocarbon. The invention thus reduces the distance to the critical ratio of the steam to the coal and the risk of soot formation in the event of a change in operating conditions, for example in the event of a mismatch of the material supply. The inventive process is then illustrated at a vapor content in the stream containing reduced oxygen to an amount of 5%, but the process will also be applicable at lower vapor concentrations.

EXAMPLE The test unit used consists of a system to supply the supply materials to the RAT reactor, the RAT reactor itself and equipment for the subsequent treatment of the product gas. The supply streams consist of natural gas, steam, oxygen and hydrogen. All gases are compressed at working pressure and preheated to working temperature. The natural gas is disulfurized before entering the RAT reactor. The two supply materials were combined into two streams and sent to the RAT burner. A first supply stream of natural gas, hydrogen and steam was heated to 500 ° C. A second feed stream containing oxygen and steam was heated to 220 ° C. In the RAT reactor, substoichiometric combustion and a subsequent catalytic vapor restoration and change reactions were carried out. The inlet and outlet gas compositions are analyzed by gas chromatography. The product gas was in equilibrium with respect to the restoration and exchange reactions. Downstream of the RAT reactor, the process gas was cooled and most of the vapor content of the product gas condensed. All soot formed during the above reaction will be collected in the condensed product. This condensed product was subjected to both gravimetric and spectrophotometric analysis. The following experiments were carried out to illustrate the influence of steam distribution on the critical carbon to steam ratios according to the invention. The hydrocarbon used was natural gas. The composition of natural gas is summarized in table 1.

TABLE 1 Composition of natural gas Each test was made by approaching the critical relationship of steam to coal from the vapor rich side. The tests were started with steam flow high enough to ensure the soot-free conditions. The vapor flow was then gradually decreased to a vapor to carbon ratio of approximately 0.03. The system was allowed to become stable, after which the condensed product was examined for soot content. If the condensed product was still free of soot, the next step was carried out. The term "soot-free conditions" refers to the condition in which the soot formation is negligible. The amount of soot formed at the critical ratio of steam to coal was about 3-5 ppm. Table 2 shows the critical relationship of steam to coal at two different temperature levels and a variable vapor distribution. The flow rates were in all the tests described above of 100 Nm3 / h of natural gas and 3 Nm3 / h of hydrogen. 100 Nm3 / h of natural gas corresponds to a coal flow rate of 103 Nm3 / h. The oxygen flow rate was adjusted to obtain the desired working temperature and varied in the range of 58-61 Nm3 / h. Due to the relatively small pilot unit heat loss, the adiabatic outlet temperature of RAT will be higher than the temperature given in table 2. This means that if a large unit is subjected, of which the loss of heat, at exactly the same conditions, the RAT outlet temperature will be close to the adiabatic outlet temperature of RAT.

TABLE 2 Critical relationship of steam to coal as a function of distribution and temperature. The pressure is 24.5 bar The gas composition of the RAT reactor product gas was measured by gas chromatography in the tests in Table 2. The selected gas compositions are shown in Table 3. The gas composition is given as% in dry mole, which is the mole composition of the gas components, when steam is not included.

TABLE 3 Composition of the product gas (% in dry mol) of the tests in Table 2 The data in Table 2 clearly demonstrate the influence of steam distribution on the critical ratio of steam to coal. The critical ratio of steam to coal is 44% higher in test number 1.1 than in test number 1.3. The concentration of vapor in the supply stream containing oxygen is 29% in test 1.1 and 5% in test 1.3. A similar but less pronounced influence is seen at higher temperature. The critical ratio of steam to coal is 15% higher in test number 2.2, in which the vapor concentrations are 24% and 6% respectively in the oxygen-containing stream.

Claims (4)

NOVELTY OF THE INVENTION CLAIMS

1. - Process for the preparation of a gas rich in hydrogen and / or carbon monoxide, comprising the step of partial oxidation of a hydrocarbon supply material with a reactive stream containing oxygen in the presence of steam, whereby two are provided streams, containing an oxygen and vapor stream, containing the other hydrocarbon and vapor, mix the two streams downstream of the burner and combustion takes place, characterized in that the vapor content of the oxygen-containing stream is less than 12%.

2. Method according to claim 1, further characterized in that the step of partial oxidation is carried out in a burner disposed in the upper part of an autothermal reactor.

3. Method according to claim 1, further characterized in that less than 1/3 of the total steam supply material is introduced with the oxygen-containing stream.

4. Method according to claim 1, further characterized in that the ratio of steam to carbon in the mixed stream is less than 0.9 at an exit temperature in an adiabatic process from 1000 ° C to 1150 ° C.