Steam saving device

Abstract

The steam saving device for a steam explosion system for the hydrothermal pre-treatment of biomass comprises a tubular body 30 with a first open end 32 and a second open end 34. The first open end 32 being adapted to be coupled to an outlet opening 14 of a steam explosion reactor vessel 10, the second open end 34 being adapted to be coupled to a discharge line 18. The inner surface 36 of the tubular body 30 of the nozzle 16 may comprise an engraved helical structure 38.

Claims

1. A nozzle (16) adapted to be coupled to and inserted into an outlet opening (14) of a steam explosion reactor vessel (10) of a steam explosion system for the hydrothermal pre-treatment of biomass, the nozzle (16) configured to transfer pre-treated biomass suspended in steam from said reactor vessel via a conduit (18) to a separation device, the nozzle (16) comprising: a tubular body (30) with a first open end (32) and a second open end (34), the first open end (32) coupled to and inserted into the outlet opening (14) of the reactor vessel (10) to receive pre-treated biomass from the reactor vessel, the second open end (34) coupled to the conduit (18) to the separation device to convey the pretreated biomass to the separation device, wherein an inner wall surface (36) of the tubular body (30) of the nozzle (16) comprises an engraved helical structure, wherein the nozzle (16) is made from a ceramic material, and wherein the engraved helical structure of the nozzle is capable of reducing steam consumption in a steam explosion-based hydrothermal pre-treatment of a biomass carried out using said reactor vessel (10), nozzle (16), and conduit (18) by at least about 5-fold compared to the nozzle lacking an engraved helical structure.

2. The nozzle (16) according to claim 1, wherein the pitch of the engraved helical structure is in the range of between 1 and 300 mm.

3. The nozzle (16) according to claim 1, wherein the length of the nozzle (16) is in the range of from 1 to 3500 mm.

4. The nozzle (16) according to claim 1, wherein the cross-sectional area of the inner wall surface (36) of the nozzle (16) is in the range of from 10 to 9000 mm.sup.2.

5. The nozzle (16) according to claim 1, wherein the depth of the engraved helical structure is in the range of from 0.1 to 15 mm.

6. The nozzle (16) according to claim 1, wherein the width of the engraved helical structure is in the range of from 0.1 to 3 mm.

7. The nozzle (16) according to claim 1, wherein the nozzle (16) is made from aluminium oxide having a purity of above 92%.

8. The nozzle (16) according to claim 1, wherein the nozzle (16) is made from aluminium oxide having a purity of 99.7%.

9. The nozzle (16) according to claim 1, wherein the nozzle (16) reduces pressure in said conduit (18).

Description

(1) The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 shows a process flow diagram of a hydrothermal pretreatment process;

(3) FIG. 2 shows a part of a cut-open nozzle of the present invention with helically engraved inner wall;

(4) FIG. 3 shows a diagram illustrating the steam consumption of the system with and without using a nozzle at the outlet end of the reactor vessel;

(5) In FIG. 1 a process flow diagram is depicted which illustrates the main components of a hydrothermal pre-treatment system. The system comprises a reactor vessel 10 with inlets 12 and an outlet 14. A steam saving device/nozzle 16 is provided at the outlet 14 of the reactor vessel 10. The nozzle 16 is coupled to a conduit 18 which is connected to a separation device 20.

(6) In a hydrothermal pre-treatment process, biomass and steam are conveyed to the reactor vessel 10 via inlets 12. The biomass material is pressurized with steam in the reactor vessel 10 at elevated temperatures for a predetermined amount of time. After the heat/pressure treatment the outlet valve 14 is opened and the hydrothermally pre-treated biomass is allowed to expand. The expansion process is also referred to as “steam explosion”. By rapidly releasing the pressure, the steam expands within the biomass material and bursts the cells of the biomass material or defibrillates the biomass material. In the depicted embodiment in FIG. 1, the separation device is a cyclone 20 having a first outlet 22 for the pre-treated biomass and a second outlet 24 for steam and other gasses.

(7) In a preferred embodiment of the invention, the steam saving device is a tubular nozzle 16 as depicted in FIG. 2. The nozzle 16 comprises a generally cylindrical tubular body 30 with a first open end 32 and a second open end 34. The tubular body 30 has generally circular cross-section. The inner wall surface 36 of the tubular body 30 is provided with an engraved helical structure. The depicted structures of FIG. 2 do not necessarily correspond to the actual dimensions of the nozzle 16. Only the lower half of a part of the nozzle 16 is depicted, such that the engraved helical structure at the inner wall surface 36 is visible. The helical structure consists of a plurality of grooves 40 having a depth of 1 mm and a width of 1.5 mm. The pitch of the grooves 40 amounts to 30 mm such that each groove 40 forms two convolutions along the full length of 60 mm of the nozzle 16.

(8) The nozzle 16 depicted in FIG. 2 is made from commercially available high purity aluminium oxide material (Al.sub.2O.sub.3 99.7%). With a nozzle 16 made from this material, no abrasion was detected after 200 h of operation. Thus, the nozzle 16 not only reduces the required amount of steam in the hydrothermal pre-treatment of biomass, but the ceramic nozzle 16 also allows for smoother operation, since the pre-treatment process had not to be interrupted for maintenance.

(9) In the following, experimental results for steam consumption in a hydrothermal pre-treatment process according to the state of the art (without nozzle) and with a nozzle according to the invention are shown.

COMPARATIVE EXAMPLE

(10) In this example the biomass material was wheat straw bales, which were loosened up in a bale crusher equipped with rotating scrappers operated at 3000 rpm yielding particles with particle sizes from 10 to 40 cm. This particle size ensures smooth transport of the straw and operation of the subsequent milling step. The biomass material was pneumatically transported to a hammer mill operated at 3000 rpm with 30 mm sieves where the straw was cut to pieces with particle sizes from 1 to 5 cm.

(11) The cut straw was transported to the thermal pre-treatment system with a pin drum feeder followed by a transportation screw and plug screw. In the reactor vessel the wheat straw was continuously pre-treated in a reactor at 160° C. for 5 min without addition of any chemicals. After this hydrothermal pre-treatment, the biomass material was transported to a cyclone to separate the organic materials form the gases.

(12) The reactor vessel used in thermal pre-treatment had an outlet with a cross-sectional area of about 283 mm.sup.2. The steam was measured to amount to 4.6 kg steam per 1 kg dry matter as depicted in FIG. 3.

Example 1

(13) A nozzle with engraved helical structure according to the present invention was inserted into the outlet of the reactor vessel. The nozzle was made from aluminium oxide ceramic (99.7%), having a length of 60 mm and was provided with an engraved helical structure at the inner wall surface. The helical structure had a pitch of 30 mm. The two grooves of the helical structure had a depth of 1.0 mm and a width of 1.5 mm.

(14) The further process parameter were identical to the process parameters of the comparative example.

(15) In Table 1 and FIG. 3 the results of the steam consumption without nozzle and with a nozzle according to the present invention are indicated. With constant dry matter feed of 400 kg/h, the steam consumption amounted to 1840 kg/h without nozzle. This corresponds to a specific steam consumption of 4.6 kg steam per 1 kg dry matter.

(16) In contrast thereto, using the nozzle according to the present invention, for the same amount of dry matter feed, the steam consumption was reduced to 364.7 kg/h. This corresponds to a specific steam consumption of only 0.91 kg steam per 1 kg dry matter, which represents an effective reduction of steam consumption by factor 5.

(17) TABLE-US-00001 Feed Steam Flow Specific Steam Consumption Nozzle [kg (dry matter)/h) (200F25) [kg/h] [kg (steam)/kg (dry matter)] No nozzle 400 1840 4.60 Nozzle with engraved helix 400 364.7 0.91

(18) As a final advantage, the resulting pressure in the conduit between the nozzle and the separator device was reduced when a nozzle according to the present invention was used. Reduced pressure beneficially affects the lifetime of the piping system.