System for hydrogen generation through steam reforming of hydrocarbons and intergrated chemical reactor for hydrogen production from hydrocarbons

Abstract

The present invention provides a reactor, which includes: a unitary shell assembly having an inlet and an outlet; a flow path extending within the shell assembly from the inlet to the outlet, the flow path having a steam reformer section with a first catalyst and a water gas shift reactor section with a second catalyst, the steam reformer section being located upstream of the water gas shift reactor section; a heating section within the shell assembly and configured to heat the steam reformer section; and a cooling section within the shell assembly and configured to cool the water gas shift reactor section. The present invention also provides a simplified hydrogen production system, which includes the catalytic steam reforming and subsequent high temperature water gas shift of low-sulfur (<100 ppm by mass) hydrocarbon fuels followed by hydrogen purification through the pressure swing adsorption (PSA). The integrated reactor offers significant advantages such as lower heat loss, lower parts count, lower thermal mass, and greater safety than the many separate components employed in conventional and is especially well-suited to applications where less than 15,000 standard cubic feet per hour of hydrogen are required. The improved system also may be started, operated and shut down more simply and quickly than what is currently possible in conventional systems. The improved system preferably employs active temperature control for added safety of operation. The hydrogen product is of high purity, and the system may be optionally operated with a feedback control loop for added purity.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an integrated chemical reactor for the production of hydrogen from hydrocarbon fuels such as natural gas, propane, liquefied petroleum gas, alcohols, naphtha and other hydrocarbon fuels and having a unique unitized, multifunctional structure. The integrated reactor offers significant advantages such as lower heat loss, lower parts count, lower thermal mass, and greater safety than the many separate components employed in conventional systems to achieve the same end. The integrated reactor is especially well-suited to applications where less than 15,000 standard cubic feet per hour of hydrogen are required. [0003] The present invention also relates to the generation of hydrogen for use in industrial applications, as a chemical feedstock, or as a fuel for stationary or mobile power plants. [0004] 2. Discussion of the Background [0005] Hydrogen production from natural gas, propane, liqu...

AI Technical Summary

Benefits of technology

[0029] Accordingly, one object of the present invention is to provide a reactor for hydrogen production that avoids the problems associated with conventional systems.

[0031] Another object of the present invention is to provide a reactor for hydrogen production that is safer and more cost efficient than conventional systems.

[0032] Another object of the present invention is to provide a reactor for hydrogen production that is less complex and is more space-sensitive than conventional systems.

[0036] Another object of the present invention is the provide for the operation of the system in a mesobaric regime, between 4 and 18 atmospheres, where appropriate fluid compression devices of small capacity, low cost, high efficiency and high reliability are readily available, and the resultant thermal efficiency of the hydrogen production system is very high.

[0037] Another object of the present invention is to provide for the feedback control of the delivery of fuel and / or air to a catalytic combustor in proportions such that the peak temperature of the gases entering the primary steam reformer does not exceed a safe maximum temperature determined by the metallurgy of the steam reformer.

[0040] Another object of the present invention is to provide a process having a simplified system construction, operation, and control resulting in low cost and relatively fast start-up and shut-down.

Problems solved by technology

For several reasons, it is difficult to adapt these large-scale technologies to economically produce hydrogen at small scales.

Further, the extent of the reaction is low at low temperatures, such that greatly elevated temperatures, often as high as 800° C., are required by conventional systems to convert an acceptable amount of hydrocarbon to hydrogen and carbon monoxide.

The radiantly-fired furnaces employed in large-scale industrial reactors have many disadvantages that make them unsuitable for small-scale systems.

The most important disadvantage is the very high temperature of the radiant burners and the gas contacting the reactor surfaces, which are usually tubular in form.

If, however, the catalyst fails due to carbon formation, sulfur poisoning or other causes, then the tubes form what is referred to in the literature as a “hot spot,” which greatly accelerates the failure of the reactor tube in question.

For systems producing below 1 ton per day, however, the complexity and cost of such safety measures can become prohibitive.

In all cases, the low temperature shift converter is quite large because of the poor catalyst activity at low temperatures.

For systems producing less than 1 ton per day, however, the unit process approach has many disadvantages.

The first disadvantage is the high proportion of the total system mass dedicated to the hardware and plumbing of the separate components.

This high mass increases startup time, material cost, and system total mass, which is undesirable for mobile applications such as powerplants for vehicles.

Another disadvantage of the unit process approach in small systems is the complexity of the plumbing system to connect the components.

The complexity increases the likelihood of leaks in the final system, which presents a safety hazard, and also significantly increases the cost of the assembly process itself.

Moreover, the requirement that each component have its own inlet and outlet provisions also adds considerable manufacturing cost to the components themselves.

A third disadvantage is the high surface area of the plumbing relative to the unit process hardware itself, which means that a disproportionately large amount of heat is lost through the connecting plumbing in small scale systems.

This can drastically reduce the thermal efficiency of the system and adds cost and complexity associated with adequately insulating the plumbing system.

A fourth disadvantage to the unit process approach in small-scale systems is that this approach requires a large volume to package, as each component and its associated plumbing must be accessible for assembly and maintenance purposes.

This is particularly disadvantageous in space-sensitive applications such as building fuel cell power stations, fuel cell vehicle refueling stations, and fuel cell mobile powerplant hydrogen generation.

These catalysts, typically based on nickel metal in the former and copper in the latter case, are extremely sensitive to poisoning and deactivation by sulfur or molecular oxygen.

Especially in the case of molecular oxygen, exposure of the active catalyst can lead to catalyst damage and even create a safety hazard through pyrophoric oxidation of the finely-divided base metal catalysts.

Provision of these reactors, heat exchangers, valves, as well as sensors and controls adds significantly to the complexity of conventional systems.

Before the system is at operating conditions, full removal of sulfur and molecular oxygen is not guaranteed, so the process feed gas must be vented to the atmosphere, wasting fuel, generating air pollution, and creating a potential safety hazard while further increasing system complexity.

Because the added components for fuel pretreatment add significant mass to the system, they also extend the warmup time required for hydrogen production.

When this traditional approach is applied to small-scale systems, however, the relative cost of these added components becomes disproportionately large, and the resulting hydrogen cost is dominated by the cost of the system.

Accordingly, it is not advantageous to simply scale down large scale systems if a small scale system is desired.

Because steam reforming creates additional moles of gas, the compression of the product gas is very energy-intensive and requires expensive and complicated compression and intercooling equipment.

Unfortunately, in small-scale systems, the provision of compression and pumping equipment to deliver the reactants into a high-pressure (20 bar or higher) reactor can undesirably increase the cost of such a system.

The operation of the primary steam reformer with such high gas temperatures can lead to significant excursions in the reformer tube wall temperature due either to poor control of the distribution of the hot gases or to poisoning of the reforming catalyst.

If the catalyst for the endothermic steam reforming reaction is locally-poisoned, the heat flux from the combustion products to the wall can form a local “hot spot.” In either case, the increase in the reformer wall temperature can lead to premature reformer structural failure, presenting both a safety and an operational liability.

Conventional systems for hydrogen generation through steam reforming of hydrocarbons have several inherent deficiencies which make them ill-suited to economical small-scale hydrogen production.

The second concerns the problems with operation in the ambient pressure regime where the large volume of reformate gas must subsequently be compressed prior to purification.

The third is associated with operating the reactor in the high-pressure regime typical of large-scale units where appropriate compression and pumping equipment adds considerable cost at small scales.

This approach, however, undesirably retains the multiple connections and extensive plumbing characteristic of the unit process approach.

Moreover, because of its complicated packaging, the assembly of the Corrigan system undesirably presents a significant challenge.

These connections once again present the same drawbacks found in unit process reactor systems.

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