DE102007035046A1 - Continuously operated ideal tubular reactor system, e.g. for oxidizing toxic material, has sandwich construction for operation in near-critical, critical and supercritical regions of water - Google Patents

Abstract

A novel continuously operated ideal tubular reactor system (a) operates at the temperatures and pressures of water (as solvent) in the near-critical, critical and supercritical regions and/or (b) is assembled as a sandwich construction with an inner plating material (such as the duplex refined steel SAF 2507) and an outer structure of fine grained carbon steel (such as WB36, i.e. 15NiCuMoNb5). Independent claims are included for: (1) a continuously operated ideal tubular reactor system, heatable by a nitrogen-containing salt mixture (achieving a maxiumum temperature of 924 K) and additional aggregates to prevent the molten salt temperature falling below the eutectic temperature (which would cause catastrophic solidification of the salt, rendering the system inoperable); (2) the derivation of a suitable mathematical formula for providing a reliable correlation between time via density versus volume via mass (allowing an engineer to achieve the necessary overall conditions), the mathematical derivation being verified by desirable empirical results; and (3) a design concept for overcoming the different expansion of the internal part of the tube relative to the outer (enclosing) tube, where (in contrast to the present construction) the difference between the internal part of the tube relative to the outer tube in an oil-heated high pressure steam generator is compensated using a high temperature-resistant linear bellows compensator.

Description

One Continuously operated ideal tubular reactor system, which at Temperatures and pressures are working well beyond the critical temperature of> 647 K and the pressure of> 221 Bar (22.1 Mpa) of water, for the formation of precious Minerals on the one hand and the destruction of dangerous and toxic waste streams on the other side. extreme Difficulties associated with corrosion and scale Fixed. The system is made with molten nitrogenous salts operated as heating means, which for the correct functioning of the reactor system and create these conditions can.

Technical area

The The present invention relates to the formation of reaction products such as ceramic, magnetic, optical, electrolytic, Electrode and other powder, the use of high temperatures for the decomposition of unwanted compounds and a too structure used for this purpose, which at near-critical, critical and supercritical temperatures and the corresponding saturated pressures of the working fluid In particular, this liquid is water.

State of the art

A stable state is assumed in which the conditions at each point of the reactor are independent of time and the total mass flow Φ _m through each cross section is the same. In this type of reactor, the reaction mixture flows through the tube like a "plug"; the linear velocity μ of the reaction mixture is the same at each point in a cross-section S perpendicular to the flow and equal to Φ _m / ρS. Based on this short explanation, we call this type of model reactor a Plug Flow Reactor (PFR).

The composition of the reaction mixture depends on the distance Z to the point of entry, as in 1 is shown. To calculate the concentration of the distributions, the material balance must be applied to a differential Sdz where S is the area of the cross-section occupied by the reaction mixture.

m_J

= Masse von J im System;

–ΔΦ_mJ

= Nettozufluss von J durch Konvektion und gegebenenfalls auch durch einen Diffusionsprozess, in dem

ΔΦmJ = ΔΦmJout – ΔΦmJin

M_JR_J

= Massenproduktionsrate von J durch chemische Reaktion pro m3

< >

= räumlicher Durchschnitt von M_JR_J;

When considering the conversion rate equation, it is important to always refer to Bird et al. (1), which reads as follows: dm J / dt = -ΔΦ m + <M J R J > V [kg / s] (1) where:

m _J

= Mass of J in the system;

-ΔΦ _mJ

= Net inflow of J by convection and possibly also by a diffusion process in which

ΔΦ mJ = ΔΦ mJout - ΔΦ mJin

M _J R _J

= Mass production rate of J by chemical reaction per m3

<>

= spatial average of M _J R _J ;

There must be a term for the chemical production rate of the species for which the balance has been presented. For the production rate of a component j (the destruction rate is practically identical), the symbol R _{j is} used when expressed in molar units per unit of time and volume; the production rate in mass units is then determined by multiplying by the molecular weight M.

In a reaction that follows the reaction formula υ A A = υ B B → υ P P = υ Q Q [2] It is often beneficial to use the concept of chemical conversion rate, which is always positive when the reaction is in the direction of the arrow. If we specify with [R] the number of moles converted according to the stoichiometric formula, per unit time and volume, we can write: | R | = | R | A / υ A = | R | B / υ B = | R | P / υ P = | R | Q / υ Q [3]

Thus, the conversion rates | R | _J | the absolute values of the molar production rates R _J ; Similarly, the mass conversion rates are the absolute values of the mass production rates. If production rates are used instead of conversion rates, it will be clear to the above reaction that the production rates of reactants A and B are negative as they are consumed. For the production rates would result: Molar production rate = = R A / υ A = -R B / υ B = R p / υ P = R Q / υ Q [4]

For the sake of consistency: dmζ J / dt = -Φ m ζ J + M J | R | J V [5]

Using Equation [5] as a starting point, this equation for the component J: 0 = -Φ m dw J + M J R J Sdz [6]

Introducing the degree of conversion ζ _J would result in: 0 = -Φ m dζ J + M J R J Sdz [7]

The total reactor volume V _r = SL, which is required for a conversion ζ _L , results from the integration of equation [7]:

oder anders ausgedrückt

Equation [8] can be simplified in the case of a constant density of the reaction mixture; thus, after substitution of the relations: Φ m = ρΦ v and ω Ao = C Ao M A / ρ surrendered:

or in other words

Attention is drawn to the fact that the integral on the right side also occurs in the calculation of the reaction time in a batch reactor. This only applies if the density is constant. It is obvious that in this particular case the following is revealed:

• a) Menge des aus zwei (2) verschiedenen Abfallstromsystemen aufgenommenen Zuflusses;
• b) Konzentration von organischen Stoffen (%) im Abfallstrom gemeinsam mit dem CSB (chemischer Sauerstoffbedarf) in kg/metrische Tonne
• c) Minimale Konversionsanforderung (Reduzierung der CSB-Zahl durch den Generator zur anschließenden biologischen Behandlung);
• d) Maximale Wärmeübertragung (Fluss) in Relation zur Querschnittsfläche (S) und der Länge (L) des Reaktors; SL stellt das Volumen (V_r) des Reaktors dar;
• e) Das Heizmittel wird aus einer Mischung aus stickstoffhaltigen Salzen gebildet, welche das Erreichen von hohen Temperaturen < 923 K ermöglichen;
• f) Angemessene Auswahl von Materialien zur Gewährleistung einer maximalen Wärmeübertragung in Verbindung mit der Eliminierung von schwerwiegender Korrosion und beträchtlicher Verkrustung.

Since the flow of large volumes of waste streams requires an adaptive design to meet the conversion rate requirements, it is obvious that the mechanical design of a plug flow reactor that will be able to operate to meet the above strict requirements will depend to a large extent on the following information:

• a) the amount of the feed taken from two (2) different waste stream systems;
• b) Concentration of organic matter (%) in the waste stream together with the COD (chemical oxygen demand) in kg / metric ton
• c) Minimum conversion requirement (reduction of COD number by the generator for subsequent biological treatment);
• d) maximum heat transfer (flow) in relation to the cross-sectional area (S) and the length (L) of the reactor; SL represents the volume (V _r ) of the reactor;
• e) The heating medium is formed from a mixture of nitrogen-containing salts, which allow the achievement of high temperatures <923 K;
• f) Adequate selection of materials to ensure maximum heat transfer coupled with the elimination of severe corrosion and significant encrustation.

Now, the following applies to the present invention:
It has been developed a continuously operated ideal tubular reactor system, which can be operated at almost critical, critical and supercritical conditions and uses water (H ₂ O) as a solvent. In conjunction with the manipulation of both temperature and pressure, it is possible under the given conditions to form synthetic minerals and break down hazardous toxic waste streams into relatively harmless compounds for further biological treatment. The aim is to reduce the COD to such an extent that the water (the main component of these waste streams) can be recycled in order to make huge financial savings. Water is a precious commodity in certain areas of the world and it should be managed intelligently.

The system comprises a long pipe with an acceptably small inside diameter made of a fine-grained carbon steel called WB36 (15NiCuMoNb5), whose phenomenal physical properties include in mine U.S. Patent 6,241,953 31 which is clad with SAF 2507 duplex stainless steel manufactured by AB Sandvik Steel, S-81181 Sandviken, Sweden; this in contrast to the cladding according to claim 6 of the said patent, ie 316 Ti.

extended and lengthy tests (the duration was over two hundred (200) hours) at near critical, critical and supercritical Conditions have shown that SAF 2507, despite its brittleness, as a result its flexural strength decreases when considered independent Structure is used in combination with WB36 an outstanding Behavior with regard to scale and corrosion. These Tests were done in my private lab as well as at AB Sandvik Steel carried out.

Before presenting several methods of analysis, it is of utmost importance to define the term corrosion:
General corrosion is characterized by a uniform attack on the surface of the material when exposed to a corrosive agent. It is therefore possible to define a corrosion rate, which is often stated as a mass loss per unit area (g / m ² h) or as an average metal loss per unit time (mm / year). The corrosion behavior of metallic materials with respect to general corrosion is often represented in isocorrosion diagrams.

The most common environments where general corrosion of Stainless steel occurs, are strongly acidic or alkaline Environments.

It There are many types of corrosion, which is why I am specific to each one Kind of restrict; Details are in each scientific metallurgical manual.

• a. Grübchenkorrosion,
• b. Risskorrosion,
• c. Spannungsrisskorrosion.

These are the following types:
Intergranular corrosion;
Local corrosion, which is divided into the following subgroups:

• a. pitting,
• b. Corrosion cracking,
• c. Stress corrosion cracking.

Galvanic corrosion

General Information about stainless steels and the influence of chromium (Cr), nickel (Ni), molybdenum (Mo), nitrogen (N) and copper (Cu).

stainless steel is the name for a group of alloys with a composition that makes these substances passivating, d. H. They form a passive layer that protects the metal from the environment protects, so as to decompose the metal (corrosion) prevent. The most important alloying element in stainless steels is chromium (Cr), which is present in concentrations of more than 12-13% forms a passive layer on the metal.

One rising proportion of chromium leads to a stronger one Passivity and thus to a higher corrosion resistance. Chromium is a so-called ferrite stabilizer, that is, that chromium does not alter the structure of iron, which over has a ferritic structure. The physical properties an alloy in which only chromium is added, differ consequently not much of pure iron. These types of alloys are referred to as ferritic stainless steels.

Even though Chrome makes the steel stainless, it can be more aggressive environments not withstand. Furthermore, the ductility of ferritic Steels limited. To fix this problem additional elements are added to the structure, the mechanical properties as well as corrosion resistance to modify.

The effects of the additions of the above elements to the (improved) physical properties are also found in every scientific metallurgical handbook, but it makes sense to list the four (4) main types of structures in stainless steels here:
Ferritic;
austenitic;
Duplex (ferritic-austenitic).

Austenitic stainless steels

The austenitic family of stainless steels covers a wide Spectrum of alloying elements, starting at 18-9 up to super austenites with up to 7% molybdenum (Mo) and the appropriate content of chromium (Cr) and nickel (Ni). This super austenite are often alloyed with nitrogen (Ni). The corrosion resistance is therefore due to a wide variety of corrosive environments customized. The super austenites are mostly composed like this that they are resistant to pitting corrosion and crack corrosion in chloride-containing environments, eg. B. in seawater, resistant are. They also have a good resistance to stress corrosion cracking on, also in hydrogen sulphide and alkaline solutions.

The austenitic steels exhibit both at low and good ductility at high temperatures Well weldable with all currently used techniques.

Duplex stainless steels

Duplex stainless steels are stainless steels with a microstructure that is ordinary 40 to 50% ferrite and the remaining amount comprises austenite. These steels combine important properties of both ferritic as well as austenitic stainless steels. she have excellent corrosion resistance as well as good Ductility and weldability on. All modern Duplex stainless steels have a nearly identical (low) Thermal conductivity (W / m.K) compared to WB36 and a low carbon content.

Duplex grade with an effective sum or PRE number (Pitting Resistance Equivalent =% Cr + 3.3% Mo + 16% N) greater than 40 are referred to as super-duplex. These steels have very good corrosion resistance properties, especially in chloride containing environments.

The Duplex structure gives a high mechanical strength, approximately is twice the strength of austenites, and is combined with a small thermal expansion, which is the of carbon steel. The low nickel content is cost-saving and high mechanical strength leads to lighter structures, resulting in further cost savings result.

It should be noted that the operating temperature of duplex stainless steel as a building material due to the risk of embrittlement and the formation of precipitation limited to 574 K. is. The salient benefits reveal themselves as plating in combination with WB36.

The This description is merely an example and an expert from the relevant field will be able to others Embodiments of the invention of this disclosure to realize without departing from the claimed invention departing.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 624195331 [0017]

Claims (10)

Continuously operated ideal tubular reactor system, which at temperatures and pressures of water (as a Solvent) in almost critical, critical and supercritical Area works. Continuously operated ideal tubular reactor system for the synthesis of oxides containing minerals, which at temperatures and pressing water (as a solvent) in the almost critical, critical and supercritical range is working. Continuously operated ideal tubular reactor system to destroy hazardous waste streams Refineries and petrochemical processes, which at temperatures and pressing water (as a solvent) in the almost critical, critical and supercritical range is working. Continuously operated ideal tubular reactor system for the oxidation of toxic organic compounds, such as Nerve gases, pesticides, etc., which at temperatures and pressures of water (as a solvent) in the near-critical, critical and supercritical area works. Continuously operated ideal tubular reactor system, which is put together in a sandwich construction, which is an interior plating material such as SAF 2507 or any suitable material, as well as one of a fine-grained carbon steel made outer Structure, such as WB36 or any suitable material, includes. Sandwich construction according to claim 5, which two (different) materials with almost identical thermal conductivities contains, thus resulting in a high heat flux towards the inside of the reactor, if this from the outside is heated. Sandwich construction according to claim 6, wherein the made of SAF 2507, mainly as a corrosion resistant inner cladding Material acts and thus a crusting or dangerous Corrosion such. B. pitting, crack and stress corrosion cracking prevents and that preferably from a fine-grained Carbon steel like WB36 produced outer material in able to withstand strong mechanical stresses during operation almost critical, critical and supercritical conditions withstand. Continuously operated ideal tubular reactor system, which, with the aid of a mixture of nitrogen-containing salts, which can reach a maximum temperature of 924 K, and is heated by auxiliary equipment which prevents that the molten salt has a temperature below its eutectic Temperature reached, resulting in catastrophic solidification of the would cause heating salts, with the result that the system would become inoperative. Derivation of the appropriate mathematical formulas, which provides a reliable correlation between time Density versus volume through mass and an engineer enable all the necessary conditions to fulfill, with the empirical results obtained confirm the mathematical derivations. Design concept the different ones Expansions of the inner set of tubes as opposed to the outer ones mechanically overcomes (comprehensive) pipe. In contrast to the current construction of a thermal oil heated high pressure steam generator will be the difference between the inner set of tubes and the outer (comprehensive) Heating tube with the help of a high temperature resistant linear Compensated bellows compensator.