阅读说明：本技术 中间相沥青专用生产装置 (Special apparatus for producing of mesophase pitch ) 是由 牛永峰 徐�明 张可意 张东伟 徐德胤 于 2021-10-08 设计创作，主要内容包括：本发明涉及一种中间相沥青专用生产装置,包括原料过滤器、原料油缓冲罐、原料进料泵、进料加热器、压缩机入口缓冲罐、蒸汽压缩机、蒸汽加热炉、反应釜、产品出料泵、蒸汽加热器、干气吸收塔、吸收油冷却器、真空分液罐、抽真空装置、轻油冷却器、油气分离罐、蒸汽分水罐、产品冷却器和产品罐,原料油通过所述的原料进口进入所述的原料过滤器；压缩机入口缓冲罐的蒸汽出口与蒸汽压缩机的进气口连接；蒸汽压缩机的排气口与蒸汽加热炉的蒸汽入口连接；蒸汽加热炉的热蒸汽出口分别与的进料加热器和蒸汽加热器连接；反应釜的顶部设置有轻油气出口和不凝气出口；反应釜的底部与产品出料泵连接；轻油气出口与轻油冷却器的轻油气入口连接。(The invention relates to a special production device for mesophase pitch, which comprises a raw material filter, a raw material oil buffer tank, a raw material feeding pump, a feeding heater, a compressor inlet buffer tank, a steam compressor, a steam heating furnace, a reaction kettle, a product discharging pump, a steam heater, a dry gas absorption tower, an absorption oil cooler, a vacuum separation liquid tank, a vacuumizing device, a light oil cooler, an oil-gas separation tank, a steam water separation tank, a product cooler and a product tank, wherein raw material oil enters the raw material filter through a raw material inlet; the steam outlet of the compressor inlet buffer tank is connected with the air inlet of the steam compressor; the exhaust port of the steam compressor is connected with the steam inlet of the steam heating furnace; a hot steam outlet of the steam heating furnace is respectively connected with the feeding heater and the steam heater; the top of the reaction kettle is provided with a light oil gas outlet and a non-condensable gas outlet; the bottom of the reaction kettle is connected with a product discharge pump; the light oil gas outlet is connected with the light oil gas inlet of the light oil cooler.)

1. The special production device for the intermediate phase asphalt is characterized by comprising a raw material filter, a raw material oil buffer tank, a raw material feeding pump, a feeding heater, a compressor inlet buffer tank, a steam compressor, a steam heating furnace, a reaction kettle, a product discharging pump, a steam heater, a dry gas absorption tower, an absorption oil cooler, a vacuum separation liquid tank, a vacuumizing device, a light oil cooler, an oil-gas separation tank, a steam water separation tank, a product cooler and a product tank, wherein the raw material filter is provided with a raw material inlet and a raw material outlet, and the raw material oil enters the raw material filter through the raw material inlet; the raw material outlet is connected with the inlet of the raw material feeding pump; the outlet of the raw material feeding pump is connected with the feeding hole of the feeding heater; the discharge hole of the feeding heater is connected with the raw oil inlet of the reaction kettle; steam from a pipe network, a steam heater and/or a product cooler enters the compressor inlet buffer tank through a steam inlet of the compressor inlet buffer tank; the steam outlet of the compressor inlet buffer tank is connected with the air inlet of the steam compressor; the exhaust port of the steam compressor is connected with the steam inlet of the steam heating furnace; the hot steam outlet of the steam heating furnace is respectively connected with the feeding heater and the steam heater; the top of the reaction kettle is provided with a light oil gas outlet and a non-condensable gas outlet; the bottom of the reaction kettle is connected with the product discharge pump; the light oil gas outlet is connected with the light oil gas inlet of the light oil cooler; a light oil gas discharge port of the light oil cooler is connected with an oil gas inlet of the oil gas separation tank; the top of the oil-gas separation tank is also connected with a non-condensable gas discharge pipe; steam from the outside of the device enters the steam knockout drum through a steam inlet of the steam knockout drum; the steam outlet of the steam water distribution tank is respectively connected with the compressor inlet buffer tank, the steam heater and the product cooler; the product inlet of the product cooler is connected with the product discharge port of the product discharge pump; the product outlet of the product cooler is connected with the product tank; the vapor outlet of the product cooler is connected with the vapor inlet of the compressor inlet buffer tank; a non-condensable gas outlet at the top of the reaction kettle is connected with a non-condensable gas inlet of the dry gas absorption tower; lean absorption liquid from the outside of the device enters the dry gas absorption tower through a lean absorption liquid inlet of the dry gas absorption tower; the top of the dry gas absorption tower is connected with the vacuum liquid separation tank; the non-condensable gas outlet of the vacuum separation liquid tank is connected with the vacuumizing device; an absorption oil outlet of the dry gas absorption tower is connected with an inlet of an absorption oil pump; the outlet of the absorption oil pump is connected with the inlet of the absorption oil cooler; and the outlet of the absorption oil cooler is respectively connected with the circulating inlet of the dry gas absorption tower and the rich absorption oil discharge pipe.

2. The special production device for mesophase pitch according to claim 1, wherein the reaction kettle comprises a first reaction kettle, a second reaction kettle, a third reaction kettle and a fourth reaction kettle, the product discharge pump comprises a first product discharge pump, a second product discharge pump, a third product discharge pump and a fourth product discharge pump, the steam heater comprises a first steam heater, a second steam heater, a third steam heater and a fourth steam heater, and the first reaction kettle, the first product discharge pump and the first steam heater are connected in series to form a closed circulation loop; the second reaction kettle, the second product discharge pump and the second steam heater are connected in series to form a closed circulation loop; the third reaction kettle, the third product discharge pump and the third steam heater are connected in series to form a closed circulation loop; and the fourth reaction kettle, the fourth product discharge pump and the fourth steam heater are connected in series to form a closed circulation loop.

3. The special production device for mesophase pitch according to claim 2, wherein product discharge ports of the first product discharge pump, the second product discharge pump, the third product discharge pump and the fourth product discharge pump are connected to a product inlet of the product cooler.

4. The special production device for mesophase pitch according to claim 2, wherein low-pressure steam or steam from a steam heating furnace is introduced into the first steam heater, the second steam heater, the third steam heater and the fourth steam heater, respectively, and exhaust ports of the first steam heater, the second steam heater, the third steam heater and the fourth steam heater are connected with a steam inlet of the compressor inlet buffer tank, respectively.

5. The special production device for mesophase pitch according to claim 2, wherein the product circulation port of the first steam heater is further connected with the noncondensable gas outlet of the first reaction vessel; the product circulation port of the second steam heater is also connected with the non-condensable gas outlet of the second reaction kettle; the product circulation port of the third steam heater is also connected with the non-condensable gas outlet of the third reaction kettle; the product circulation port of the fourth steam heater is also connected with the non-condensable gas outlet of the fourth reaction kettle; and the product circulation port of the first steam heater, the product circulation port of the second steam heater, the product circulation port of the third steam heater and the product circulation port of the fourth steam heater are respectively connected with a nitrogen supply pipe.

6. The special production device for mesophase pitch according to claim 1, wherein a back-flushing dirty oil outlet is further arranged at the bottom of the raw material filter.

7. The special production device for mesophase pitch according to claim 1, wherein a medium-pressure steam gas supply pipe and a low-pressure steam gas exhaust pipe are further connected between the steam compressor and the steam heating furnace.

8. The special production device for mesophase pitch according to claim 1, wherein an absorption oil pump is further arranged between the dry gas absorption tower and the absorption oil cooler.

9. The special production device for mesophase pitch according to claim 1, wherein a gas oil outlet of the vacuum separation tank is connected with a gas oil pump.

10. The special production device for mesophase pitch according to claim 1, wherein the bottom of the oil-gas separation tank is connected with a light oil pump.

Technical Field

The invention relates to the technical field of asphalt production, in particular to a special production device for mesophase asphalt.

Background

Mesophase Pitch (MP for short) is a mixture of a plurality of flat disc-like fused ring aromatic hydrocarbons having a relative molecular mass of 370 to 2000, and is also called liquid crystal phase Pitch.

The mesophase pitch is a nematic liquid crystal substance formed by disc-shaped or rod-shaped molecules generated in the heat treatment process of heavy aromatic hydrocarbon substances, and the raw materials of the mesophase pitch can be coal tar pitch, petroleum pitch, pure aromatic hydrocarbon substances and mixtures thereof.

In the prior art, mesophase pitch is mostly prepared from coal tar pitch, petroleum pitch and other heavy oils. Because the raw material cost is lower, and a way is provided for the efficient utilization of the heavy asphalt. However, the preparation of these heavy feedstocks is relatively complex due to their inherent complexity and diversity.

Coal pitch, also known as coal tar pitch, is pitch prepared by distilling coal tar obtained after coal carbonization. Coal pitch has a low carbonization yield and is not suitable for direct use as a precursor for the preparation of carbonaceous materials, and therefore, the raw material pitch is generally pretreated to adjust its composition to accommodate the formation of mesophases.

Petroleum asphalt is the residue of natural petroleum produced by distillation or other production processes. The asphaltene with a flaky fused ring aromatic structure in the residue has high relative molecular mass, aromatizing degree and thermal stability, and is a high-quality raw material for preparing mesophase asphalt. The process of producing mesophase pitch from petroleum pitch is essentially a purification process that removes low relative molecular mass, low aromatic materials.

In the prior art, the main problems of the mesophase pitch production device include: the structure is complex, the production efficiency is low, the utilization efficiency of the heat source is low, the mixed product cannot be finely utilized, and the like.

Disclosure of Invention

The invention aims to provide a special production device for mesophase pitch, and aims to solve the technical problems of simplifying equipment, improving production efficiency, fully utilizing heat sources, improving heat utilization efficiency, and separating and finely utilizing mixed products of non-condensable gas, light oil gas and the like.

The invention aims to solve the defects of the prior art and provides a special production device for mesophase pitch, which comprises a raw material filter, a raw material oil buffer tank, a raw material feeding pump, a feeding heater, a compressor inlet buffer tank, a steam compressor, a steam heating furnace, a reaction kettle, a product discharging pump, a steam heater, a dry gas absorption tower, an absorption oil cooler, a vacuum separation liquid tank, a vacuumizing device, a light oil cooler, an oil-gas separation tank, a steam water separation tank, a product cooler and a product tank, wherein the raw material filter is provided with a raw material inlet and a raw material outlet, and raw material oil enters the raw material filter through the raw material inlet; the raw material outlet is connected with the inlet of the raw material feeding pump; the outlet of the raw material feeding pump is connected with the feeding hole of the feeding heater; the discharge hole of the feeding heater is connected with the raw oil inlet of the reaction kettle; steam from a pipe network, a steam heater and/or a product cooler enters the compressor inlet buffer tank through a steam inlet of the compressor inlet buffer tank; the steam outlet of the compressor inlet buffer tank is connected with the air inlet of the steam compressor; the exhaust port of the steam compressor is connected with the steam inlet of the steam heating furnace; the hot steam outlet of the steam heating furnace is respectively connected with the feeding heater and the steam heater; the top of the reaction kettle is provided with a light oil gas outlet and a non-condensable gas outlet; the bottom of the reaction kettle is connected with the product discharge pump; the light oil gas outlet is connected with the light oil gas inlet of the light oil cooler; a light oil gas discharge port of the light oil cooler is connected with an oil gas inlet of the oil gas separation tank; the top of the oil-gas separation tank is also connected with a non-condensable gas discharge pipe; steam from the outside of the device enters the steam knockout drum through a steam inlet of the steam knockout drum; the steam outlet of the steam water distribution tank is respectively connected with the compressor inlet buffer tank, the steam heater and the product cooler; the product inlet of the product cooler is connected with the product discharge port of the product discharge pump; the product outlet of the product cooler is connected with the product tank; the vapor outlet of the product cooler is connected with the vapor inlet of the compressor inlet buffer tank; a non-condensable gas outlet at the top of the reaction kettle is connected with a non-condensable gas inlet of the dry gas absorption tower; lean absorption liquid from the outside of the device enters the dry gas absorption tower through a lean absorption liquid inlet of the dry gas absorption tower; the top of the dry gas absorption tower is connected with the vacuum liquid separation tank; the non-condensable gas outlet of the vacuum separation liquid tank is connected with the vacuumizing device; an absorption oil outlet of the dry gas absorption tower is connected with an inlet of an absorption oil pump; the outlet of the absorption oil pump is connected with the inlet of the absorption oil cooler; and the outlet of the absorption oil cooler is respectively connected with the circulating inlet of the dry gas absorption tower and the rich absorption oil discharge pipe.

The reaction kettle comprises a first reaction kettle, a second reaction kettle, a third reaction kettle and a fourth reaction kettle, the product discharge pump comprises a first product discharge pump, a second product discharge pump, a third product discharge pump and a fourth product discharge pump, the steam heater comprises a first steam heater, a second steam heater, a third steam heater and a fourth steam heater, and the first reaction kettle, the first product discharge pump and the first steam heater are connected in series to form a closed circulation loop; the second reaction kettle, the second product discharge pump and the second steam heater are connected in series to form a closed circulation loop; the third reaction kettle, the third product discharge pump and the third steam heater are connected in series to form a closed circulation loop; and the fourth reaction kettle, the fourth product discharge pump and the fourth steam heater are connected in series to form a closed circulation loop.

The product discharge ports of the first product discharge pump, the second product discharge pump, the third product discharge pump and the fourth product discharge pump are all connected with the product inlet of the product cooler.

And low-pressure steam or steam from the steam heating furnace is respectively introduced into the first steam heater, the second steam heater, the third steam heater and the fourth steam heater, and exhaust ports of the first steam heater, the second steam heater, the third steam heater and the fourth steam heater are respectively connected with a steam inlet of the inlet buffer tank of the compressor.

The product circulation port of the first steam heater is also connected with the non-condensable gas outlet of the first reaction kettle; the product circulation port of the second steam heater is also connected with the non-condensable gas outlet of the second reaction kettle; the product circulation port of the third steam heater is also connected with the non-condensable gas outlet of the third reaction kettle; the product circulation port of the fourth steam heater is also connected with the non-condensable gas outlet of the fourth reaction kettle; and the product circulation port of the first steam heater, the product circulation port of the second steam heater, the product circulation port of the third steam heater and the product circulation port of the fourth steam heater are respectively connected with a nitrogen supply pipe.

The bottom of the raw material filter is also provided with a back-flushing sump oil outlet.

And a medium-pressure steam air supply pipe and a low-pressure steam exhaust pipe are also connected between the steam compressor and the steam heating furnace.

An absorption oil pump is also arranged between the dry gas absorption tower and the absorption oil cooler.

And a gas oil outlet of the vacuum separation liquid tank is connected with a gas oil pump.

The bottom of the oil-gas separation tank is connected with a light oil pump.

Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

the special production device for the mesophase pitch has a simple structure, can cool and recover light oil components in the reaction process, and removes wax oil fractions by using the absorption tower; raw oil can carry out the self-loopa through the product discharge pump, has improved production efficiency to can make the raw materials fully react, avoid the raw materials extravagant, reduce manufacturing cost.

In the aspect of heat utilization efficiency, the special production device for mesophase pitch disclosed by the invention adopts two specifications of steam, low-pressure steam is used in the main working condition, the steam can be recycled, and the heat utilization efficiency is improved.

Drawings

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

FIG. 1 is a schematic view showing the structure of the feed oil and steam in the present invention.

FIG. 2 is a schematic view of the connection structure of the reaction vessel according to the present invention.

Fig. 3 is a schematic view of the connection structure of the noncondensable gas and lean absorption oil treatment portion in the present invention.

Fig. 4 is a schematic view of a connection structure of a light oil cooler according to the present invention.

Fig. 5 is a schematic view of the connection structure of the product cooler of the present invention.

Detailed Description

The present invention is described in more detail below to facilitate an understanding of the present invention.

As shown in fig. 1 to 5, the special production apparatus for mesophase pitch according to the present invention includes a raw material filter 1, a raw material oil buffer tank 2, a raw material feed pump 3, a feed heater 4, a compressor inlet buffer tank 5, a vapor compressor 6, a vapor heating furnace 7, a reaction kettle, a product discharge pump, a vapor heater, a dry gas absorption tower 8, an absorption oil cooler 9, a vacuum liquid separation tank 10, a vacuum pumping device 30, a light oil cooler 41, an oil-gas separation tank 42, a vapor water separation tank 44, a product cooler 45, and a product tank 46, wherein the raw material filter 1 is provided with a raw material inlet and a raw material outlet, and raw material oil enters the raw material filter 1 through the raw material inlet; the raw material outlet is connected with the inlet of the raw material feeding pump 3; the outlet of the raw material feeding pump 3 is connected with the feeding hole of the feeding heater 4; the discharge hole of the feeding heater 4 is connected with the raw oil inlet of the reaction kettle; steam from a pipe network, steam heater and/or product cooler enters the compressor inlet buffer tank through the steam inlet of the compressor inlet buffer tank 5; the steam outlet of the compressor inlet buffer tank 5 is connected with the air inlet of the steam compressor 6; the exhaust port of the vapor compressor 6 is connected with the vapor inlet of the vapor heating furnace 7; the hot steam outlet of the steam heating furnace 7 is respectively connected with the feeding heater 4 and the steam heater; the top of the reaction kettle is provided with a light oil gas outlet and a non-condensable gas outlet; the bottom of the reaction kettle is connected with the product discharge pump; the light oil gas outlet is connected with the light oil gas inlet of the light oil cooler 41; a light oil gas discharge port of the light oil cooler 41 is connected with an oil gas inlet of the oil gas separation tank 42; the top of the oil-gas separation tank 42 is also connected with a non-condensable gas discharge pipe; steam from the outside of the apparatus enters the steam knockout drum through the steam inlet of the steam knockout drum 44; the steam outlet of the steam water separation tank 44 is respectively connected with the compressor inlet buffer tank 5, the steam heater and the product cooler 45; a product inlet of the product cooler 45 is connected with a product outlet of the product discharge pump; the product outlet of the product cooler 45 is connected to the product tank 46; the vapor outlet of the product cooler 45 is connected to the vapor inlet of the compressor inlet surge tank 5; a non-condensable gas outlet at the top of the reaction kettle is connected with a non-condensable gas inlet of the dry gas absorption tower 8; lean absorption liquid from the outside of the device enters the dry gas absorption tower 8 through a lean absorption liquid inlet of the dry gas absorption tower 8; the top of the dry gas absorption tower 8 is connected with the vacuum liquid separation tank 10; the non-condensable gas outlet of the vacuum separation liquid tank 10 is connected with the vacuumizing device 30; the absorption oil outlet of the dry gas absorption tower 8 is connected with the inlet of an absorption oil pump 31; the outlet of the absorption oil pump 31 is connected with the inlet of the absorption oil cooler 9; the outlet of the absorption oil cooler 9 is respectively connected with the circulating inlet of the dry gas absorption tower 8 and the rich absorption oil discharge pipe.

As shown in fig. 2, in a preferred embodiment, the reaction vessels include a first reaction vessel 11, a second reaction vessel 12, a third reaction vessel 13 and a fourth reaction vessel 14, the product discharge pumps include a first product discharge pump 15, a second product discharge pump 16, a third product discharge pump 17 and a fourth product discharge pump 18, the steam heaters include a first steam heater 21, a second steam heater 22, a third steam heater 23 and a fourth steam heater 24, and the first reaction vessel 11, the first product discharge pump 15 and the first steam heater 21 are connected in series to form a closed circulation loop; the second reaction kettle 12, the second product discharge pump 16 and the second steam heater 22 are connected in series to form a closed circulation loop; the third reaction kettle 13, the third product discharge pump 17 and the third steam heater 23 are connected in series to form a closed circulation loop; the fourth reaction vessel 14, the fourth product discharge pump 18 and the fourth steam heater 24 are connected in series to form a closed circulation loop.

The product discharge ports of the first product discharge pump 15, the second product discharge pump 16, the third product discharge pump 17 and the fourth product discharge pump 18 are all connected with the product inlet of the product cooler 45.

Low-pressure steam or steam from the steam heating furnace 7 is respectively introduced into the first steam heater 21, the second steam heater 22, the third steam heater 23 and the fourth steam heater 24, and exhaust ports of the first steam heater 21, the second steam heater 22, the third steam heater 23 and the fourth steam heater 24 are respectively connected with a steam inlet of the compressor inlet buffer tank 5.

The product circulation port of the first steam heater 21 is also connected with the non-condensable gas outlet of the first reaction kettle 11; the product circulation port of the second steam heater 22 is also connected with the non-condensable gas outlet of the second reaction kettle 12; the product circulation port of the third steam heater 23 is also connected with the non-condensable gas outlet of the third reaction kettle 13; the product circulation port of the fourth steam heater 24 is also connected with the non-condensable gas outlet of the fourth reaction kettle 14; the product circulation port of the first steam heater 21, the product circulation port of the second steam heater 22, the product circulation port of the third steam heater 23 and the product circulation port of the fourth steam heater 24 are also connected with a nitrogen gas supply pipe respectively.

The bottom of the raw material filter 1 is also provided with a back-flushing sump oil outlet.

And a medium-pressure steam air supply pipe and a low-pressure steam exhaust pipe are also connected between the steam compressor 6 and the steam heating furnace 7.

An absorption oil pump 31 is also arranged between the dry gas absorption tower 8 and the absorption oil cooler 9.

The gas oil outlet of the vacuum separation liquid tank 10 is connected with a gas oil pump 32.

The bottom of the oil-gas separation tank 42 is connected with a light oil pump 43.

The process flow of the special production device for mesophase pitch provided by the invention is as follows:

raw oil is filtered by a raw material filter 1 and then enters a raw oil buffer tank 2, is pressurized by a raw material feed pump 3, enters a feed heater 4, is heated to 400 ℃, and then enters a reaction kettle (the time for use is 4 hours); heating to 450 deg.C in a reaction kettle by a steam heater, reacting for 24 hr, wherein the raw oil is self-circulated via a product discharge pump to make the reaction uniform; in order to reduce the oil carrying amount of the vacuum system, a filling section is arranged at the top of the reaction kettle.

The light oil component is recovered after cooling in the reaction process; when the reaction is finished, closing an oil gas emptying valve on the reaction kettle, quickly opening a vacuum valve on a vacuumizing device, and pumping out the residual light oil components (taking half an hour); then starting a product discharge pump (using time is 1 hour), removing wax oil fraction from the product by an absorption tower, cooling the product by steam, and then sending the product into a product tank or shaping the product, wherein the operation period of each reaction kettle is 36 hours.

The special production device for mesophase pitch adopts two specifications of steam, uses low-pressure steam in a main working condition, and is divided into three stages:

1) firstly, a raw material heating stage, wherein low-pressure steam enters a compressor inlet buffer tank 5, is pressurized to 1.1MPa by a steam compressor 6 and then enters a steam heating furnace 7 to be heated to 500 ℃ to serve as a heat source to enter a feeding heater 4 to heat the raw material, the steam coming out of the feeding heater 4 returns to the compressor inlet buffer tank 5, is pressurized by the steam compressor 6 again and heated by the steam heating furnace to serve as a thermal mass for recycling, and is prepared to enter a reaction stage after feeding is completed;

2) in the reaction stage, stopping feeding and heating, and changing into reaction and heating; the heated low-pressure steam is used as a heat source to enter a steam heater to heat reaction materials, the low-pressure steam coming out of the steam heater enters a compressor inlet buffer tank, is pressurized to 1.1MPa by the steam compressor, enters a steam heating furnace to be heated to 500 ℃, then enters the steam heater as the heat source to circularly operate, and enters a product cooling stage when the reaction is finished;

3) in the product cooling stage, low-pressure steam from the system is taken as a cold source and introduced into a steam heater to cool reaction materials, then the reaction materials enter an inlet buffer tank of a compressor, and are sent out of the device after being pressurized to 1.1MPa by the steam compressor; when the reaction kettle is cooled to a set temperature, low-pressure steam from the system is introduced into the product cooler as a cold source to cool the reaction materials, then enters the inlet buffer tank of the compressor, is pressurized to 1.1MPa by the steam compressor, and is then sent out of the device.

The standby working condition adopts high-pressure steam, when a steam compressor is not started, the high-pressure steam is decompressed to 1.5MPa, enters a steam heating furnace to be heated to 500 ℃, enters a feeding heater as a heat source to heat raw materials and a steam heater to heat, the technological process is the same as that of the low-pressure steam working medium, and the steam coming out of the steam heater enters a compressor inlet buffer tank and then is sent out of the device.

The foregoing describes preferred embodiments of the present invention, but is not intended to limit the invention thereto. Modifications and variations of the embodiments disclosed herein may be made by those skilled in the art without departing from the scope and spirit of the invention.