TW201502456A - Plate heat exchanger and method of using - Google Patents

Abstract

A process for heating a cold stream with a hot stream is described. At least one of the cold inlet or outlet, the hot inlet or outlet, the cold inlet or outlet header, the hot inlet or outlet header, and the plurality of plates is made of one of two stainless steel alloys. One alloy has higher molybdenum content with copper for improved corrosion resistance and is resistant to chloride pitting, chloride SCC, and PTA SCC. The other alloy has significantly higher tensile and yield strength, which will reduce the susceptibility of the plate bundle to thermal stress damage.

Description

Flat plate heat exchanger and method of use thereof Priority statement

The present application claims priority to U.S. Application Serial No. 13/894,945, filed on May 5, 2013, the entire disclosure of which is hereby incorporated by reference.

Refineries typically incorporate one or more different processes to treat and/or convert hydrocarbons, such as those present in crude oil or another natural source, to produce a particular hydrocarbon product having properties that are useful for a particular application.

In order to carry out refining or processing operations to treat crude oil and other hydrocarbons to form usable products, refineries typically include one or more equipment complexes or groups designed to carry out one or more specific treatment or conversion processes to prepare The final product is expected. In this regard, the composites can each have a variety of interconnecting devices or vessels, including, in particular, cans, furnaces, distillation columns, reactors, heat exchangers, pumps, tubes, fittings, and valves.

Many types of hydrocarbon processing operations are carried out under relatively harsh operating conditions, including high temperatures and/or high pressures, and in a variety of demanding chemical environments. In addition, due to the high demand for hydrocarbon and petrochemical products, the volume flow of hydrocarbon streams through various refinery complexes is large, and the downtime of processing equipment is preferably small to avoid output loss.

High temperature hydrocarbon processing operations typically involve heating a hydrocarbon stream to a processing temperature and flowing the hydrocarbon stream through one or more hydrocarbon processing vessels forming a refinery complex. The particular processing technique utilized will depend on the feed and desired product, and may include flowing a hydrocarbon stream in the presence of other materials and/or reactants, including gases and liquids, for The product stream removes the adsorbent of a particular component and/or the catalyst used to control the rate of reaction. In this manner, the hydrocarbon stream can be processed to, for example, modify one or more components of the hydrocarbon stream, react one or more components with other materials in the vessel (eg, a gas), and use the components from the hydrocarbon stream as a potential The product (sometimes after further processing) is removed or discarded.

Traditionally, austenitic stainless steel has been used to make the refinery equipment listed above because these types of alloys can be used in a variety of demanding environments. The addition of 8% nickel to stainless steel containing 18% chromium produced a significant change in microstructure and properties. The alloy solidifies and cools to form a non-magnetic face centered cubic structure called Vostian Iron. Vostian Iron Stainless Steel is highly ductile and has excellent weldability and other manufacturing properties even at very low temperatures. The most widely used stainless steel may be type 304 (sometimes referred to as T304 or simply 304) due to cost. Type 304 stainless steel is a Wostian iron steel containing 18% to 20% chromium and 8% to 10% nickel. And have such other special austenitic stainless steel used in these applications, but tends to occur in the presence of such a high temperature in the process H ₂ S, sulfur and chloride -SCC corrosion and high temperature hydrogen attack problem.

Many metals, including Worthfield iron stainless steel, can withstand highly corroded forms known as stress-corrosion cracking (SCC). SCC is typically in the form of branch cracks in significantly extensible materials and can occur with little prior warning. In low pressure vessels, the first sign of stress corrosion cracking is usually leakage, but the high pressure vessel has a fatal failure due to stress corrosion cracking. Stress corrosion cracking occurs when the surface of the material exposed to the corrosive medium is under tensile stress (applied or residual) and the corrosive medium unambiguously causes stress corrosion cracking of the metal. Tensile stress can be caused by the applied load, internal pressure in the piping system and pressure vessel, or residual stress from previous welds or bends.

A particularly harsh environment is one that contains halides, typically in the form of inorganic chlorides, where it is generally observed that Worthfield iron stainless steel undergoes stress corrosion cracking. The presence of chloride and aqueous phases and tensile stress can cause chloride stress corrosion cracking ("chloride-SCC") of Worthfield iron stainless steel. This type of rupture is mainly transgranular and depends on time, oxygen and Chloride concentration. Stress corrosion cracking due to chloride is generally observed in the presence of chloride and oxygen in the region where tensile stress is experienced in the Vostian iron stainless steel. Typically, chloride-SCC will occur if a high concentration of chloride is present, but it can also occur at lower concentrations and elevated temperatures. In addition, although high temperatures can reduce the amount of time required for a particular chloride concentration to result in chloride-SCC, lower temperatures can cause chloride to condense on the surface, thereby increasing the concentration of chloride on the surface. Therefore, chloride-SCC can cause problems in many temperature ranges. For example, chloride-SCC can occur if the chloride concentration can accumulate on the heated surface, for example, due to pitting or cracking of the surface of the material, or if chloride present in the environment condenses on the surface of the material. Chloride can penetrate the passive membrane, allowing corrosive attack of the material to occur. A particularly problematic area of chloride-SCC is in the condenser where the chloride condenses and concentrates on the surface of the vessel.

Another type of harsh corrosive environment in which sensitized stainless steel is particularly susceptible is an environment containing polysulfonic acid (PTA) formed by the decomposition of sulfide scale by moisture in the air. Typically, chromium in the Worthfield iron stainless steel reacts with oxygen to form a passivated chromium oxide film that protects the material from corrosion. The passivated metal is resistant to further oxidation or rust. However, at a high temperature somewhere in the range between 370 ° C and 815 ° C (depending on the stainless steel alloy), chromium-rich carbides precipitate at the grain boundaries. The precipitation of chromium depletes the chromium content adjacent to the grain boundaries, thereby forming chromium depletion regions and significantly reducing the corrosion resistance and/or crack resistance in corrosive environments in such regions. This phenomenon is called sensitization. Iron sulfide scale can form on the surface of stainless steel due to the high operating temperatures in many refinery complexes and/or processes and the presence of sulfur (S) and hydrogen sulfide (H ₂ S) in the reducing environment or in the cold stream. After the equipment is shut down, if the sensitized stainless steel is exposed to moisture and oxygen from the surrounding environment, there is a possibility that sulfur and hydrogen sulfide will react with oxygen and moisture from the surrounding environment to form PTA. If the container is placed under tensile stress by pressurization or by residual stress from, for example, welding during fabrication, the PTA can erode the chromium depletion zone formed by sensitization, causing corrosion and eventual polysulfuric acid stress. Corrosion cracking (PTA-SCC). Worstian iron stainless steel (such as Type 304 and Type 316), which has traditionally been used to make unstabilized grades of refinery complexes, all exhibit sensitization and PTA-SCC due to polysulfuric acid. In order to minimize the formation of Cr-rich carbides or sensitized microstructures, elements such as Nb or Ti are added to react with excess C and stabilize the microstructure. However, if such stabilization levels (eg, Types 321 and 347) are exposed for a sufficiently long time at elevated temperatures (eg, 400 ° C to 800 ° C), they may even exhibit sensitization and PTA-SCC.

In some cases, a protective coating is applied to protect the exterior of the stainless steel container from exposure to chloride in the insulating sheath. In other applications, post-weld heat treatment can be used to relieve residual stress in the steel alloy.

The risks of PTA-SCC and chloride-SCC in refinery equipment are primarily addressed by known processes that prevent the formation of PTA and/or the presence of chloride or PTA in the environment prior to exposure to air.

In order to reduce the effect of chloride-SCC, precautions are often taken to minimize the amount of chloride in the process material or feed that will be contacted with the Worthfield iron stainless steel equipment. Precautions are also taken to limit the chloride content of any irrigant, purge or neutralizer used in the system to low levels. In addition, limiting exposure to oxygenated gases and/or water also helps to avoid chloride-SCC.

Prevention of PTA formation and subsequent rupture can be achieved by eliminating liquid phase water or eliminating oxygen, as these materials result in a reaction with sulfide scale to form a component of PTA. One method is to maintain the temperature of the Worthfield iron stainless steel equipment above the dew point of the water to avoid condensation of moisture. Another method is to purge the device with a dry nitrogen purge while depressurizing the system and opening the device and exposing it to air during any shutdown or start-up procedure, which is therefore typically the only time that a significant amount of oxygen can enter the system.

The PTA that must or may be formed in the composite or container can be neutralized by an ammoniated nitrogen purge or a soda ash aqueous solution. Ammonia nitrogen is purged, a special procedure is used to form ammoniated nitrogen, and the ammoniated nitrogen is pressurized and blown into the system. The neutralization step of the soda ash solution involves completely filling the tubing or parts of the equipment involved with the solution and allowing the system to be placed prior to exposing the system to air. Soak for at least two hours. During the operation of the refinery complex, each of these processes is time consuming and impractical, as additional material and additional downtime for the particular equipment is required to implement the purge or neutralization step. In addition, when nitrogen, ammonia nitrogen or soda ash is present, special precautions must be taken to protect the maintenance workers working on the equipment. Removal of these chemicals reduces the need for special disposal and waste disposal. In addition, if trace chemicals are left, the catalyst in the reactor may be poisoned, which is usually the case.

In addition, chemically stabilized Worthfield iron stainless steels (such as TP321 and TP347) have been used in reactors for the treatment of sulfur-containing streams due to their high temperature corrosion resistance. However, such Worstian iron stainless steels are also prone to PTA-SCC due to exposure to polysulfuric acid, as many hydrocarbon processing processes operate at temperatures that are sensitized. Similarly, these materials are prone to chloride-SCC when exposed to chloride, oxygen, water, and stress for sufficient time and temperature. The need for special procedures during the shutdown and start-up of the refinery complex not only affects costs, but also affects production time, as it takes a certain amount of time to implement.

Solder plate heat exchangers used in a variety of processes to heat or cool streams in a variety of processes are typically made of Type 304 or Type 316 or Type 321 stainless steel and are subjected to chloride-SCC and PTA-SCC.

Currently, when chloride or sulfur is likely to be present, corrosion in the welded plate heat exchanger is avoided by preventing the presence of moisture and oxygen. Chloride is typically present in the catalytic recombination process and ammonium chloride salts have been found in the effluent side of the flatbed. A small amount of sulfur is injected into the catalytic recombination process to minimize carburization and metal catalyzed coking. There is no liquid water and oxygen during normal operation. The heat exchanger was kept under nitrogen purge during shutdown. If the exchanger needs to be inspected or maintained, water washing and soda ash washing are performed to remove chloride and neutralize the sulfide prior to opening the exchanger to the atmosphere. However, even with such precautions, when liquid water is present in the feed, resulting in pitting of the chloride, chloride pitting due to corrosion under scale, and when a water dew point occurs during regeneration of the fixed bed recombination unit, Chloride pitting and chloride-SCC due to the presence of chlorides, oxygen and water, usually still Chloride corrosion of the welded plate heat exchanger was observed. Any failure due to corrosion or rupture will reduce product quality due to contamination of the product stream by the feed stream.

In addition, some of the welded plate heat exchangers can be damaged by thermal stresses that can cause mechanical damage to the heat exchanger. This type of mechanical damage accounts for the vast majority of all damage that causes beam cross-leakage. A thermal transient that produces a rapid transient change in beam temperature or a temperature differential that causes a temperature difference between adjacent portions of the beam can cause thermal stress. Thermal transients can occur during start-up, shutdown, and imbalance conditions. When there is fouling of the bundle, when there is a sudden blockage of the bundle, a flow poor distribution may occur when there is a blockage of the distributor or when there is a low velocity that causes the liquid in the bundle to flow upward.

Thermal stress damage that causes beam cross-leakage is costly for the end user because it results in cross-leakage of higher pressure flow to lower pressure flow, resulting in reduced heat transfer efficiency and possible contamination of the feed stream. Logistics. This damage can result in reduced throughput, reduced product quality, and may eventually require downtime to repair or replace the heat exchanger. In the case of corrosion and SCC, the bundle cannot be repaired because most or all of the flat channels are normally damaged and the bundle or the entire heat exchanger needs to be replaced. In the event of thermal stress damage, the bundle can be repaired by blocking the passage during downtime to allow continued operation. However, when the channel of 10-20% or higher is blocked, the resulting increase in pressure drop can significantly reduce the flux. In addition, the repaired bundle can be more susceptible to further thermal stress damage.

Currently, the mechanical properties of Type 304 and Type 321 stainless steels will be used to limit the beam design temperature to 560 °C for welded flat plate heat exchangers. Some processes may require higher design temperatures, for example, 590 ° C or higher.

Accordingly, there is still a need in the industry for an improved process for processing hydrocarbon streams while avoiding the costly, time consuming and inconvenient additional steps of purging or neutralizing the internal environment to avoid formation of polysulfuric acid and reduction in the welded flat plate heat exchanger. The effect of chloride and cause PTA-SCC, chloride-SCC or thermal stress.

One aspect of the invention utilizes a heat flow (e.g., reactor effluent) to heat a cold stream (e.g., feed to a reaction zone). In one embodiment, the process includes providing a plate heat exchanger. The plate heat exchanger comprises a plurality of corrugated plates forming a cold flow passage and a heat flow passage, a cold inlet in fluid communication with the cold flow passage, a cold outlet in fluid communication with the cold flow passage, a heat inlet in fluid communication with the heat flow passage, and a heat flow passage a hot outlet that is in fluid communication. The cold flow is directed to the cold inlet and the heat flow is directed to the hot inlet and the hot self-heat flow is exchanged to the cold stream. The exit is higher than the cold flow at the entrance, and the exit is below the heat flow at the entrance. At least one of the cold inlet, the cold outlet, the heat inlet, the heat outlet, and the plurality of plates is made of a first stainless steel alloy comprising 0.005 wt% to 0.020 wt% carbon, 9.0 wt% to 13.0 wt% nickel 17.0 wt% to 19.0 wt% chromium, 0.20 wt% to 0.50 wt% niobium, and 0.06 wt% to 0.10 wt% nitrogen; or a second stainless steel alloy comprising 0.0005 wt% to 0.020 wt% carbon, 10 wt% to 30 wt% Nickel, 15 wt% to 24 wt% chromium, 0.20 wt% to 0.50 wt% rhodium, 0.06 wt% to 0.10 wt% nitrogen, up to 5 wt% copper, up to 1.00 wt% rhodium, up to 2.00 wt% manganese, and 0.3 wt% to 7 wt% molybdenum.

Another aspect of the invention is a welded plate heat exchanger. The welded plate heat exchanger comprises: a plurality of welding wave plates forming a cold flow channel and a heat flow channel, a cold inlet in fluid communication with the cold flow channel, a cold outlet in fluid communication with the cold flow channel, and a heat inlet in fluid communication with the heat flow channel a heat outlet in fluid communication with the heat flow passage. At least one of the cold inlet, the cold outlet, the heat inlet, the heat outlet, and the plurality of plates is made of a first stainless steel alloy comprising 0.005 wt% to 0.020 wt% carbon, 9.0 wt% to 13.0 wt% nickel 17.0 wt% to 19.0 wt% chromium, 0.20 wt% to 0.50 wt% niobium, and 0.06 wt% to 0.10 wt% nitrogen; or a second stainless steel alloy comprising 0.0005 wt% to 0.020 wt% carbon, 10 wt% to 30 wt% Nickel, 15 wt% to 24 wt% chromium, 0.20 wt% to 0.50 wt% rhodium, 0.06 wt% to 0.10 wt% nitrogen, up to 5 wt% copper, up to 1.00 wt% rhodium, up to 2.00 wt% manganese, 0.3 wt% to 7 wt% Molybdenum, 0.01% by weight to 2.0% by weight of cerium and 0.1% by weight to 0.5% by weight of boron.

5‧‧‧ Fixed bed catalytic recombination process

10‧‧‧Feed

15‧‧‧ gas

20‧‧‧Compressor

25‧‧‧Combined feed-effluent (CFE) heat exchanger

30‧‧‧Preheated mixture

35‧‧‧Reaction zone

40‧‧‧heater

45‧‧‧Preheated mixture

50‧‧‧Reactor

55‧‧‧ effluent

60‧‧‧heater

65‧‧‧heated effluent

70‧‧‧Reactor

75‧‧‧ effluent

80‧‧‧heater

85‧‧‧heated effluent

90‧‧‧Reactor

95‧‧‧ effluent

100‧‧‧Drainage

105‧‧‧Condenser

110‧‧‧Partial condensate flow

115‧‧‧Separator

120‧‧‧Liquid products

125‧‧‧ airflow

130‧‧‧Parts

135‧‧‧ remaining part / net airflow

150‧‧‧welding plate bundle

155‧‧‧ Pressure vessel

160‧‧‧Hot entrance

165‧‧‧Hot inlet header

170‧‧‧hot exit

175‧‧‧Hot export header

180‧‧‧ cold entrance

185‧‧‧Cold inlet header

190‧‧‧ cold exit

195‧‧‧ Cold exit header

250‧‧‧welding plate bundle

260‧‧‧Hot entrance

265‧‧‧Hot inlet header

270‧‧‧hot exit

275‧‧‧Hot outlet header

280‧‧‧ cold entrance

285‧‧‧Cold inlet header

290‧‧‧ cold exit

295‧‧‧ Cold exit header

297‧‧‧End plate

299‧‧‧ lever

300‧‧‧Continuous catalytic regeneration process

310‧‧‧ Feeding

315‧‧‧ gas

320‧‧‧Compressor

325‧‧‧Combined feed-effluent (CFE) heat exchanger

330‧‧‧Preheated mixture

340‧‧‧heater

345‧‧‧Preheated mixture

350‧‧‧Reactor

355‧‧‧ effluent

360‧‧‧heater

365‧‧‧heated effluent

370‧‧‧Reactor

375‧‧‧ effluent

380‧‧‧heater

385‧‧‧heated effluent

390‧‧‧reactor

395‧‧‧ effluent

400‧‧‧heater

405‧‧‧heated effluent

410‧‧‧Reactor

415‧‧‧ effluent

420‧‧‧Exhaust flow

425‧‧‧Separator

430‧‧‧Liquid products

435‧‧‧ airflow

440‧‧‧Part 1

445‧‧‧Part II

450‧‧‧Net Gas Compressor

455‧‧‧Compressed net gas

460‧‧‧Used catalyst

465‧‧‧catalyst regenerator

470‧‧‧Renewable catalyst

480‧‧‧Recycling section

500‧‧‧Liquid-liquid process

505‧‧‧ Feed gas

510‧‧‧ absorber

515‧‧‧Processed gas

520‧‧‧cold solvent

525‧‧‧Plate heater exchanger

530‧‧‧Hot solvent

535‧‧‧Stripper

540‧‧‧temperature-raised solvent

545‧‧‧ concentrator

550‧‧‧cooling solvent

555‧‧‧top gas

560‧‧‧ Compressor

565‧‧‧Compressed gas

570‧‧‧Bottom

575‧‧‧ overheads

580‧‧‧Return accumulator

585‧‧‧acid flow

590‧‧‧Water flow

595‧‧‧Supply water

600‧‧‧ water flow

Figure 1 is a graphical illustration of a fixed bed catalytic recombination process utilizing a combined feed-effluent heat exchanger.

Figure 2 is a graphical illustration of a continuous catalyst regeneration recombination process utilizing a combined feed-effluent heat exchanger.

Figure 3 is a graphical illustration of a liquid-liquid process utilizing a Lean-Rich Solvent heat exchanger.

Figure 4 is an illustration of one embodiment of a plate heat exchanger.

Figure 5 is an illustration of another embodiment of a plate heat exchanger.

Processes for treating a cold stream of hydrocarbons comprising one or more different hydrocarbons and which may include other components and/or impurities typically include flowing a hydrocarbon stream through various parts of the apparatus. The apparatus may be included as part of a larger refinery complex capable of performing one or more specific types of hydrocarbon conversion or treatment processes for converting or treating one or more components of the hydrocarbon cold stream. The desired product is formed. The hydrocarbon stream and/or equipment is heated during operation. The hydrocarbon stream can be heated to raise its temperature to the processing temperature before it is placed in or into the apparatus. Specific process parameters or operating conditions (e.g., temperature, pressure, and space velocity) are typically process specific and selected to facilitate a particular reaction or processing step for a particular process. The process is maintained for a predetermined amount of time. The process can be shut down intermittently for repair or replacement of equipment, inspection or for other reasons.

The welded flat plate heat exchanger is used for equipment parts in some processes. The welded plate heat exchanger includes a wavy plate bundle. The corrugated plates are welded together to form flow channels for cold flow and heat flow. In one embodiment using countercurrent flow, the cold flow enters the heat exchanger at one end and exits at the opposite end. The heat flow enters at the opposite end and exits at the end where the cold flow enters.

In some embodiments, the cold inlet and outlet headers connect the cold inlet and outlet to the weld The plate bundle is connected, and the hot inlet and outlet headers connect the hot inlet and outlet to the welding plate bundle. In other embodiments, no headers are provided.

In one method, the process includes controlling a halide stress corrosion cracking of at least a portion of the welded plate heat exchanger heated to a predetermined temperature (eg, a temperature at which sensitization will occur), and more particularly, chloride-SCC , PTA-SCC and / or thermal stress. Even if chloride or polysulfonic acid is present therein during operation of the welded plate heat exchanger, the process can include controlling chloride-SCC, PTA-SCC, or thermal stress of at least a portion of the welded plate heat exchanger. In one form, controlling the chloride-SCC, PTA-SCC, and/or thermal stress of at least a portion of the welded plate heat exchanger is accomplished by employing one or both of the following specified in the welded plate heat exchanger Stone aluminum stainless steel composition to achieve.

In one method, the process includes controlling sensitization of at least a portion of the welded plate heat exchanger heated to a predetermined temperature. Controlling sensitization includes limiting or reducing the amount of sensitization that occurs and may involve limiting or reducing the extent of precipitation of chromium carbide within the material of the welded plate heat exchanger. Even if the welded plate heat exchanger is heated to a predetermined temperature for a predetermined amount of time, the precipitation of chromium carbide is controlled to the extent that sensitization is generally observed in the sensitized envelope of the conventional Worth iron stainless steel. When heating at least a portion of the welded plate heat exchanger, control of the precipitation of chromium carbide in the welded plate heat exchanger can be achieved because the welded plate heat exchanger is a Worth iron stainless steel composition as described below. One of them is formed.

The welded plate heat exchanger can be heated to a predetermined temperature and maintained at a predetermined temperature for a predetermined amount of time. It has been found that a welded plate heat exchanger formed from one of two Worthfield iron stainless steel compositions is heated to a predetermined time and temperature within the normal operating conditions of the welded plate heat exchanger without welding. Sensitization of the plate heat exchanger.

In one method, the welded plate heat exchanger can be heated to a temperature above a predetermined temperature by passing through a stream of hot hydrocarbon streams, wherein the hydrocarbon stream is heated to a predetermined temperature prior to entering the heat exchanger, and the hot hydrocarbons are heated. The flow is passed through a plate beam to a cold hydrocarbon stream.

Surprisingly, even within the sensitized envelope of the Worthite stainless steel conventionally used to make a welded plate heat exchanger, or near the sensitized envelope, at a predetermined temperature and for a predetermined time for maintaining the process At the same time, sensitization is still reduced or limited. Without being bound by theory, it is believed that the lower carbon content of the Worthfield iron stainless steel composition reduces or limits the extent of precipitation of chromium carbide along the grain boundaries within the alloy. This in turn reduces or limits the formation of chromium depletion zones and sensitization typically found in Worthfield iron stainless steels used in refinery complex fabrication. It is further believed that the added ruthenium interacts with the carbon and nitrogen present in the material to limit the formation and precipitation of chromium carbide. It is also believed that the addition of nitrogen to the Worthfield iron stainless steel reduces any loss of strength that can occur due to the low carbon content of the welded plate heat exchanger.

In addition, in addition to reinforced steel, it is believed that nitrogen and molybdenum have similar functions in terms of pitting corrosion and chloride-SCC resistance due to the formation of a nitrogen-limited chromium-molybdenum phase. In an acidic environment, corrosion of metals typically involves simultaneous metal dissolution reactions and hydrogen evolution reactions. Inhibiting one of these reactions will reduce corrosion. However, when a lower content of nitrogen is present, chromium nitride is formed in the grain boundaries, resulting in sensitization. The molybdenum in the novel Worthite iron stainless steel of the present invention significantly inhibits the escape of hydrogen in most reduced acids (e.g., most organic acids) and thereby increases the resistance of the metal to organic acids.

The chloride ion may generally be sufficient to cause the chloride-SCC content to be present in the welded plate heat exchanger. It is believed that the inclusion of molybdenum in the Vostian iron stainless steel composition enhances the bluntness of the material in the chloride-containing environment by stabilizing the passive chromium oxide film on the material. If the passivation film is deteriorated, it is believed that molybdenum can even repair the passivation film. In this regard, the Worthfield iron stainless steel composition increases the pitting resistance and crack resistance of the welded flat plate heat exchanger. Since the pit is usually the starting point of chloride stress corrosion cracking, molybdenum also increases resistance to chloride stress corrosion cracking.

It can also include barium and boron. Niobium and boron reduce the tendency of stainless steel to undergo chloride stress corrosion cracking.

In addition, when these alloys are used, when polysulfonic acid is present in the welded plate, it is hot When it is in the converter, it will not cause polysulfuric acid stress corrosion cracking. Without being bound by theory, it is believed that polysulfonic acid does not attack the grain boundaries of stainless steel due to the absence of chromium depletion regions typically present due to sensitization when utilizing such alloys. In this manner, the process includes exposing the welded plate heat exchanger to the external environment without taking steps to reduce or limit the formation of polysulfonic acid and control the corrosion of the polysulfonic acid to the welded plate heat exchanger.

The plate bundle is made of one of two stainless steel alloys. In some embodiments, at least one of the cold inlet, the cold outlet, the hot inlet, and the heat outlet are also made of, or lined with, one of two stainless steel alloys. In some embodiments, all of the components are made from one of two alloys. In some embodiments, the plate heat exchanger includes a cold inlet header in fluid communication with the cold inlet and the cold flow passage, a cold outlet header in fluid communication with the cold outlet and the cold flow passage, and is in fluid communication with the hot inlet and the heat flow passage. A hot inlet header or a hot outlet header in fluid communication with the hot outlet and the heat flow passage. If one or more of the headers are present, one or more of them may also be made of one of the two alloys or lined with the alloy, depending on how the welded flat plate heat exchanger is used. .

The first stainless steel alloy has a content of 0.005 wt% to 0.020 wt% carbon, 9.0 wt% to 13.0 wt% nickel, 17.0 wt% to 19.0 wt% chromium, 0.20 wt% to 0.50 wt% bismuth, and 0.06 wt% to 0.10 wt% nitrogen. Or a composition consisting essentially of or consisting of. The remainder of the composition includes iron and may include one or more additional components. This alloy has significantly higher tensile and lodging strengths, which allows the design of flat beams for higher pressures and/or temperatures. This alloy will also reduce the sensitivity of the flat beam to thermal stress damage. Generally, when a thin plate is cooled or cooled more rapidly than an adjacent portion, it contracts with respect to the adjacent portion, resulting in a tensile mechanical failure called thermal stress damage. Higher allowable tension fluctuations and relief stresses allow thicker portions, such as headers, spacers, and end plates, to be designed with smaller thicknesses to reduce thermal inertia and reduce thermal stresses due to thermal transients. At the same time, thin plates benefit from higher tension drop and fall strength, allowing them to handle large thermal stresses. The thin plate is made of a sheet (for example, 0.8 mm to 1.2 mm) which is wavy, stacked and welded to shape A welded flat plate heat exchanger bundle.

The second stainless steel alloy has from 0.0005 wt% to 0.020 wt% carbon, 10 wt% to 30 wt% nickel, 15 wt% to 24 wt% chromium, 0.20 wt% to 0.50 wt% rhodium, 0.06 wt% to 0.10 wt% nitrogen, up to 5 wt% Copper, up to 1.00 wt% bismuth, up to 2.00 wt% manganese, and 0.3 wt% to 7 wt% molybdenum or a composition consisting essentially of or consisting of. The remainder of the composition includes iron and may include one or more additional components. A second stainless steel alloy having a higher molybdenum content and enhanced copper resistance for enhanced corrosion resistance, chloride pitting, chloride SCC and PTA SCC. This will eliminate concerns about corrosion damage to the flatbed during both operation and downtime.

The first alloy, the second alloy, or both may optionally include from 0.01 wt% to 2 wt% bismuth and from 0.1 wt% to 0.5 wt% boron. Niobium and boron reduce the tendency of stainless steel to undergo chloride stress corrosion cracking.

In one embodiment, a welded plate heat exchanger can be used when the cold stream referred to as a coolant or cooling fluid has a high chloride content. Cooling fluids include, but are not limited to, water.

Although the two alloys are more expensive than the alloys currently used for welded flat plate heat exchangers, this can be compensated for by reducing the risk of costly unplanned downtime or flux reduction in the process, since Potential damage.

In one method, the process includes maintaining the operation of the welded plate heat exchanger for more than 300 hours, during which time the process is intermittently shut down and no sensitization of the welded plate heat exchanger occurs. In some embodiments, the process can be maintained for more than 1,000 hours or more than 2,500 hours or more than 5,000 hours or more than 7,500 hours or more than 10,000 hours or more than 50,000 hours or more than 100,000 hours or more than 150,000 hours. It should be noted that, as described herein, the occurrence of sensitization of the welded plate heat exchanger is not considered to be sufficient if the amount of sensitization of the welded plate heat exchanger is insufficient to cause chloride-SCC or PTA-SCC of the welded plate heat exchanger within a predetermined amount of time. Chemical.

In one method, the process includes high exchange of heat between the heat flow and the cold flow Warm process. In this method, at least a portion of the welded plate heat exchanger is heated to a temperature by a heat flow through which it flows. In one method, at least a portion of the welded plate heat exchanger is heated to a predetermined temperature. In another method, some or all of the welded plate heat exchangers are heated to a temperature above 400 °C or above 550 °C or above 565 °C. In still another method, the maximum temperature is below 700 °C. The term predetermined temperature as used herein does not necessarily mean constant or known temperature, and may include, for example, average temperature, median temperature, temperature range, and the like.

An example of a fixed bed catalytic recombination process 5 is illustrated in FIG. Feed 10 is mixed with gas 15 from compressor 20. The mixture of feed 10 and gas 15 is preheated in a combined feed-effluent (CFE) heat exchanger 25. The preheated mixture 30 then flows to the reaction zone 35. As shown, reaction zone 35 includes a series of one or more heaters and reactors. The preheated mixture 30 is heated in the heater 40 and the mixture 45 is preheated and then flows to the reactor 50. The effluent 55 from reactor 50 is sent to heater 60. The heated effluent 65 from the heater 60 is sent to the reactor 70. The effluent 75 from reactor 70 is sent to heater 80. The heated effluent 85 from the heater 80 is sent to the reactor 90. The effluent 95 from reactor 90 is sent to CFE heat exchanger 25 where effluent 95 is used to preheat the mixture of feed 10 and gas 15. The heat exchange in the CFE heat exchanger 25 reduces the temperature of the effluent stream 100. Stream 100 can partially condense. Stream 100 is further condensed in condenser 105. The partial condensate stream 110 is sent to a separator 115 where the partial condensate stream 110 is separated into a liquid product 120 and a gas stream 125. The liquid product 120 can then be sent for further processing, such as fractionation (not shown). Stream 125 includes a light fraction gas and hydrogen. A portion 130 of the gas stream 125 is sent to the compressor 20 for mixing with the feed 10. The remaining portion 135 is a net airflow 135. The light ends gas can be further separated in a recovery section (not shown).

FIG. 2 illustrates a continuous catalytic regeneration recombination process 300. Feed 310 is mixed with gas 315 from compressor 320. A mixture of feed 310 and gas 315 is preheated in a combined feed-effluent (CFE) heat exchanger 325. Preheating the mixture 330 and then flowing to the opposite Should be district. As shown, the reaction zone included a series of 4 heaters and 4 stacked reactors. The preheated mixture 330 is heated in the heater 340 and the mixture 345 is preheated and then flows to the reactor 350. The effluent 355 from reactor 350 is sent to heater 360. The heated effluent 365 from heater 360 is sent to reactor 370. The effluent 375 from reactor 370 is sent to heater 380. The heated effluent 385 from heater 380 is sent to reactor 390. The effluent 395 from reactor 390 is sent to heater 400. The heated effluent 405 from the heater 400 is sent to the reactor 410. The effluent 415 from reactor 410 is sent to a CFE heat exchanger 325 where the effluent 415 is used to preheat the mixture of feed 310 and gas 315. The heat exchange in the CFE heat exchanger 325 reduces the temperature of the effluent stream 420. The effluent stream 420 from the CFE heat exchanger 325 can be partially condensed (condenser not shown). The effluent stream 420 is sent to a separator 425 where the effluent stream 420 is separated into a liquid product 430 and a gas stream 435. The gas stream 435 is divided into a first portion 440 that is sent to the compressor 320 and a second portion 445 that is sent to the net gas compressor 450. The compressed net gas 455 is combined with the liquid product 430 and sent to a recovery section 480. The used catalyst 460 is sent to the catalyst regenerator 465 which oxidizes the coke. The regeneration catalyst 470 is sent to the reactor 350.

3 is an illustration of one embodiment of a liquid-liquid process 500 that uses a physical solvent to remove an acid process gas from a synthesis or natural gas stream. Feed gas 505 is directed to absorber 510 where feed gas 505 is treated with a liquid solvent. The self-absorber 510 removes the treated gas 515. Cold solvent 520 is fed to plate heater exchanger 525 where heat is exchanged with hot solvent 530 from stripper 535. The heated solvent 540 is sent to the concentrator 545 and the cooled solvent 550 is sent to the absorber 510. The overhead gas 555 from concentrator 545 is sent to compressor 560. The compressed gas 565 is sent to the absorber 510. The bottoms 570 from the concentrator 545 are sent to a stripper 535 where the bottoms 570 are separated into a solvent 530 and an overhead 575. The overhead 575 is sent to a reflux accumulator 580 where the overhead 575 is separated into an acid stream 585 and a stream 590. Water stream 590 can be combined with make-up water 595 to form stream 600 and sent to stripper 535.

One embodiment of a CFE heat exchanger 25 is shown in FIG. In this embodiment, the welding plate bundle 150 is housed in the pressure vessel 155. The pressure vessel 155 contains a pressurized fluid. The plate beam is designed for the differential pressure between the cold flow and the heat flow.

There is a thermal inlet 160 that is connected by a hot inlet header 165 to the welding plate bundle 150. At the opposite end of the CFE heat exchanger 25, there is a heat outlet 170 connected to the welded flat sheet bundle 150 by a hot outlet header 175. The cold inlet 180 is connected to the welded flat plate bundle 150 by a cold inlet header 185, and the cold outlet 190 is connected to the welded flat plate bundle 150 by a cold outlet header 195, although this is not required. For the illustrated counterflow configuration, the hot inlet 160 and the cold outlet 190 are on one end of the CFE heat exchanger 25, while the hot outlet 170 and the cold inlet 180 are on opposite ends. However, other configurations are possible, as will be understood by those skilled in the art.

In some embodiments, the inlet and/or outlet are nozzles and may include a connecting conduit.

Not all welded flat plate heat exchangers have headers that connect the inlet and outlet to the flow passage. There may be separate fluid communication between the cold inlet and outlet and the cold flow passage and between the hot inlet and outlet and the heat flow passage, and the presence or absence of the header depends on the type and design of the flat heat exchanger.

Another embodiment of heat exchanger 525 is shown in FIG. In this configuration, there is no pressure vessel. A pair of end plates 297 are clamped to the welded flat plate bundle 250. The pair of end plates 297 can be clamped to the welded flat sheet bundle 250 using any known method including, but not limited to, tie rods 299. The end plate may also be formed from a plurality of parts each held by a plurality of tie rods.

There is a thermal inlet 260 that is connected by a hot inlet header 265 to the welded plate bundle 250. At the opposite end of the CFE heat exchanger 525, there is a hot outlet 270 that is connected by a hot outlet header 275 to the welded plate bundle 250. The cold inlet 280 is connected to the welded flat plate bundle 250 by a cold inlet header 285, and the cold outlet 290 is connected to the welded flat plate bundle 250 by a cold outlet header 295, although this is not required. For the illustrated counterflow configuration, the hot inlet 260 and the cold outlet 290 are on one end of the CFE heat exchanger 525, while the hot outlet 270 and the cold inlet 280 are on opposite ends. However, other configurations are possible, as will be understood by those skilled in the art.

Specific embodiment

Although the following is set forth in conjunction with the specific embodiments, it is understood that this description is intended to be illustrative and not restrictive.

A first embodiment of the present invention is a process for heating a cold flow by heat flow, comprising providing a plate heat exchanger comprising a plurality of undulating plates forming a cold flow passage and a heat flow passage, in fluid communication with the cold flow passage a cold inlet, a cold outlet in fluid communication with the cold flow passage, a hot inlet in fluid communication with the heat flow passage, a heat outlet in fluid communication with the heat flow passage; directing the cold flow to the cold inlet and directing the heat flow to the heat inlet and from the heat flow The heat exchange to the cold flow, the cold flow of the cold outlet is higher than the cold flow at the cold inlet, and the heat flow of the hot outlet is lower than the heat flow of the hot inlet; wherein the plurality of flat plates are made of the following a first stainless steel alloy comprising 0.005 wt% to 0.020 wt% carbon, 9.0 wt% to 13.0 wt% nickel, 17.0 wt% to 19.0 wt% chromium, 0.20 wt% to 0.50 wt% bismuth, and 0.06 wt% to 0.10 wt% % nitrogen; or a second stainless steel alloy comprising 0.0005 wt% to 0.020 wt% carbon, 10 wt% to 30 wt% nickel, 15 wt% to 24 wt% chromium, 0.20 wt% to 0.50 wt% 铌, 0.06 wt% to 0.10 wt% Nitrogen, up to 5 wt% copper, up to 1.00 wt% rhodium, up to 2.00 wt% manganese, and 0.3 wt% to 7 wt% molybdenum. An embodiment of the invention is one, any or all of the prior embodiments in this paragraph up to the first embodiment in this paragraph, wherein the first stainless steel alloy, the second stainless steel alloy or both further comprise 0.01 wt % to 2.0 wt% 铍 and 0.1 wt% to 0.5 wt% boron. An embodiment of the invention is one, any or all of the prior embodiments in this paragraph up to the first embodiment of the paragraph, wherein at least one of a cold inlet, a cold outlet, a hot inlet, and a hot outlet It is made of a first stainless steel alloy or a second stainless steel alloy. Embodiments of the invention are any, any or all of the prior embodiments in this paragraph up to the first embodiment of the paragraph, further comprising a cold inlet header in fluid communication with the cold inlet and the cold flow passage a cold outlet header in fluid communication with the cold outlet and the cold flow passage, a heat inlet header in fluid communication with the heat inlet and the heat flow passage, and at least one of a heat outlet header in fluid communication with the heat outlet and the heat flow passage, and Among them, the cold inlet header and the cold outlet At least one of the header, the heat inlet header, and the heat outlet header is made of a first stainless steel alloy or a second stainless steel alloy. An embodiment of the invention is one, any or all of the prior embodiments in this paragraph up to the first embodiment in this paragraph, wherein a plurality of plates are welded. An embodiment of the invention is one, any or all of the prior embodiments in this paragraph up to the first embodiment of the paragraph, wherein the plate heat exchanger further comprises a pressure vessel containing a plurality of plates. Embodiments of the invention are one, any or all of the prior embodiments in this paragraph up to the first embodiment of the paragraph, wherein the plate heat exchanger further comprises a pair of clamps on the plurality of plates End plate. Embodiments of the invention are any one, any or all of the prior embodiments in this paragraph up to the first embodiment of the paragraph wherein the heat flow comprises steam and wherein the heat flow at least partially condenses in the plate heat exchanger . Embodiments of the invention are one, any or all of the prior embodiments in this paragraph up to the first embodiment in this paragraph, wherein the cold flow comprises liquid and wherein the cold flow is at least partially in the plate heat exchanger Vaporization. An embodiment of the invention is one, any or all of the prior embodiments in this paragraph up to the first embodiment in this paragraph, wherein the cold flow comprises a cooling fluid. Embodiments of the invention are one, any or all of the prior embodiments in this paragraph up to the first embodiment of the paragraph, wherein a plurality of plates are welded, the plurality of plates are contained in the pressure vessel, and the cold flow A liquid mixed with a recycle gas, the heat stream being a vapor, and wherein the cold stream is at least partially vaporized in the plate heat exchanger, and the heat stream is at least partially condensed in the plate heat exchanger. Embodiments of the invention are one, any or all of the prior embodiments in this paragraph up to the first embodiment of the paragraph, wherein a plurality of plates are welded, the plate heat exchanger further comprising a pair of clamps The end plates of the plurality of plates are cold flow liquid, and the heat flow is liquid. Embodiments of the invention are one, any or all of the prior embodiments in this paragraph up to the first embodiment of the paragraph wherein the cold inlet and the heat outlet are at one end of the plate heat exchanger and are cold The outlet and the hot inlet are at the other end of the plate heat exchanger. Embodiments of the invention are one, any or all of the prior embodiments in this paragraph up to the first embodiment of this paragraph, wherein the plate heat exchanger operates at a temperature above 590 °C.

A second embodiment of the present invention is a welded plate heat exchanger comprising a plurality of welding wave plates forming a cold flow passage and a heat flow passage, a cold inlet in fluid communication with the cold flow passage, and a cold outlet in fluid communication with the cold flow passage. a heat inlet in fluid communication with the heat flow passage, a heat outlet in fluid communication with the heat flow passage; wherein the plurality of flat sheets are made of: a first stainless steel alloy comprising 0.005 wt% to 0.020 wt% carbon, 9.0 wt% to 13.0 wt% nickel, 17.0 wt% to 19.0 wt% chromium, 0.20 wt% to 0.50 wt% niobium, and 0.06 wt% to 0.10 wt% nitrogen; or a second stainless steel alloy comprising 0.0005 wt% to 0.020 wt% carbon, 10 wt % to 30 wt% nickel, 15 wt% to 24 wt% chromium, 0.20 wt% to 0.50 wt% niobium, 0.06 wt% to 0.10 wt% nitrogen, up to 5 wt% copper, up to 1.00 wt% niobium, up to 2.00 wt% manganese, 0.3 wt% % to 7 wt% of molybdenum, 0.01 wt% to 2.0 wt% of rhodium, and 0.1 wt% to 0.5 wt% of boron. An embodiment of the invention is one, any or all of the prior embodiments in this paragraph up to the second embodiment of the paragraph, wherein at least one of a cold inlet, a cold outlet, a hot inlet, and a hot outlet It is made of a first stainless steel alloy or a second stainless steel alloy. Embodiments of the invention are any, any or all of the prior embodiments in this paragraph up to the second embodiment of the paragraph, further comprising a cold inlet header in fluid communication with the cold inlet and the cold flow passage a cold outlet header in fluid communication with the cold outlet and the cold flow passage, a heat inlet header in fluid communication with the heat inlet and the heat flow passage, and at least one of a heat outlet header in fluid communication with the heat outlet and the heat flow passage, and At least one of the cold inlet header, the cold outlet header, the hot inlet header and the hot outlet header is made of a first stainless steel alloy or a second stainless steel alloy. An embodiment of the invention is one, any or all of the prior embodiments in this paragraph up to the second embodiment of the paragraph, further comprising a pressure vessel comprising a plurality of plates. An embodiment of the invention is one, any or all of the prior embodiments in this paragraph up to the second embodiment of the paragraph, further comprising a pair of end plates clamped to the plurality of plates. Embodiments of the invention are any, any or all of the prior embodiments in this paragraph up to the second embodiment of the paragraph wherein the cold inlet and the heat outlet are at one end of the plate heat exchanger and are cold The outlet and the hot inlet are at the other end of the plate heat exchanger.

Although at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, It is also to be understood that the exemplified embodiments are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; It is to be understood that various changes may be made in the <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt;

5‧‧‧ Fixed bed catalytic recombination process

10‧‧‧Feed

15‧‧‧ gas

20‧‧‧Compressor

25‧‧‧Combined feed-effluent (CFE) heat exchanger

30‧‧‧Preheated mixture

35‧‧‧Reaction zone

40‧‧‧heater

45‧‧‧Preheated mixture

50‧‧‧Reactor

55‧‧‧ effluent

60‧‧‧heater

65‧‧‧heated effluent

70‧‧‧Reactor

75‧‧‧ effluent

80‧‧‧heater

85‧‧‧heated effluent

90‧‧‧Reactor

95‧‧‧ effluent

100‧‧‧Drainage

105‧‧‧Condenser

110‧‧‧Partial condensate flow

115‧‧‧Separator

120‧‧‧Liquid products

125‧‧‧ airflow

130‧‧‧Parts

135‧‧‧ remaining part / net airflow

Claims (10)

A method of heating a cold flow using a heat flow, comprising: providing a plate heat exchanger (25) comprising: a plurality of undulating plates (150) forming a cold flow passage and a heat flow passage, and being in fluid communication with the cold flow passages An inlet (180), a cold outlet (190) in fluid communication with the cold flow passages, a heat inlet (160) in fluid communication with the heat flow passages, and a heat outlet (170) in fluid communication with the heat flow passages; A cold flow is directed to the cold inlet (180) and directs the heat flow to the hot inlet (160) and exchanges heat from the heat flow to the cold stream, the cold flow at the cold outlet (190) being higher than The cold flow (180) is at the enthalpy of the cold flow, and the heat flow at the heat outlet (170) is lower than the heat flow at the heat inlet (160); wherein the plurality of flat plates are Made of: a first stainless steel alloy comprising 0.005 wt% to 0.020 wt% carbon, 9.0 wt% to 13.0 wt% nickel, 17.0 wt% to 19.0 wt% chromium, 0.20 wt% to 0.50 wt% 铌, and 0.06 wt% to 0.10 wt% nitrogen; or a second stainless steel alloy comprising 0.0005 wt% to 0.020 wt% carbon, 10 wt% to 30 wt% nickel, 15 wt% to 24 wt% chromium, 0.20 wt% to 0.50 wt% 铌, 0.06 wt % to 0.10 wt% nitrogen, up to 5 wt% copper, up to 1.00 wt% rhodium, up to 2.00 wt% manganese, and 0.3 wt% to 7 wt% molybdenum. The method of claim 1, wherein the first stainless steel alloy, the second stainless steel alloy, or both further comprise 0.01 wt% to 2.0 wt% bismuth and 0.1 wt% to 0.5 wt% boron. The method of any one of claims 1 to 2, wherein at least one of the cold inlet (180), the cold outlet (190), the hot inlet (160), and the hot outlet (170) is the first Made of stainless steel alloy or the second stainless steel alloy. The method of any one of claims 1 to 2, further comprising a cold inlet header (185) in fluid communication with the cold inlet (180) and the cold flow channels, and the cold outlet (190) a cold outlet header (195) in fluid communication with the cold flow passages, a heat inlet header (165) in fluid communication with the heat inlet (160) and the heat flow passages, and the heat outlet (170) and the like At least one of a heat outlet header (175) in fluid communication with the heat flow passage, and wherein the cold inlet header (185), the cold outlet header (195), the hot inlet header (165), and the set of hot outlets At least one of the tubes (175) is made of the first stainless steel alloy or the second stainless steel alloy. The method of any one of claims 1 to 2, wherein the plurality of plates are welded. The method of claim 5, wherein the plate heat exchanger (25) further comprises a pressure vessel (155) comprising the plurality of plates (150). The method of claim 5, wherein the plate heat exchanger (25) further comprises a pair of end plates clamped to the plurality of plates (150). The method of any one of claims 1 to 2, wherein the heat stream comprises a vapor and wherein the heat stream is at least partially condensed in the plate heat exchanger, or wherein the cold stream comprises a liquid and wherein the cold stream is hot in the plate The exchanger is at least partially vaporized, or both. The method of any one of claims 1 to 2, wherein the plate heat exchanger (25) is operated at a temperature above 590 °C. A welded plate heat exchanger (25) comprising: a plurality of welding wave plates (150) forming a cold flow channel and a heat flow channel, a cold inlet (180) in fluid communication with the cold flow channels, and the like a flow outlet fluidly connected cold outlet (190), a thermal inlet (160) in fluid communication with the heat flow passages, and a heat outlet (170) in fluid communication with the heat flow passages; wherein the plurality of flat sheets are made of: a first stainless steel alloy comprising 0.005 wt% to 0.020 wt% carbon, 9.0 wt% to 13.0 wt% nickel, 17.0 wt% to 19.0 wt% chromium, 0.20 wt% to 0.50 wt% bismuth, and 0.06 wt% to 0.10 wt% Nitrogen; or a second stainless steel alloy comprising 0.0005 wt% to 0.020 wt% carbon, 10 wt% Up to 30 wt% nickel, 15 wt% to 24 wt% chromium, 0.20 wt% to 0.50 wt% rhodium, 0.06 wt% to 0.10 wt% nitrogen, up to 5 wt% copper, up to 1.00 wt% rhodium, up to 2.00 wt% manganese, 0.3 wt% Up to 7 wt% molybdenum, 0.01 wt% to 2.0 wt% rhodium, and 0.1 wt% to 0.5 wt% boron.